# AMP Hours



## Rapide561 (Oct 1, 2005)

Hi

Silly question....

If a leisure battery is 110 amp hours, does that mean (in theory) if I were to use 11amps per hour, it would last 10 hours?

Rapide561


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## DABurleigh (May 9, 2005)

If you think that's a silly question (well, apart from the "per hour" bit), you just wait until you see how this thread runs 

Even the theory is complex, let alone the in practice bit which says you'll get much less. 

What is definite is that you should not plan for it to give you that much, certainly not at that consumption rate.

Dave


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## sallytrafic (Jan 17, 2006)

DABurleigh said:


> If you think that's a silly question (well, apart from the "per hour" bit), you just wait until you see how this thread runs
> 
> Dave


Oooh! I like a challenge! ;-)

First of all I think that you would get 11A for 10 hours on a NEW battery in fact you might get slightly more.

BUT completely discharging even a 'deep discharge' battery is not good for its long term life, every time you do it you are bringing closer the day that you will have to replace it. If you were to leave it in a flattened state that would do even more damage.

Paradoxically if you were to repeatedly charge and discharge the battery for say five times under controlled conditions down to 80% discharged you might find that the capacity of the battery has increased! This is because the process of initially charging a battery by the manufacturer is often skimped.

Personally I would never plan to take a battery below 90% discharged and others on this site would for very good reasons say not below 50% discharged.

The first part of my article on Solar systems might be worth a read as it is largely talking about the battery. see it HERE

Regards Frank

Now I suspect its George's turn......


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## DABurleigh (May 9, 2005)

Before he does, a suspicion I have that I haven't yet got around to checking either by testing or researching, is that when you draw those sort of currents in the ambient temperatures we "enjoy" (brrrrr...) in these sceptred isles, the terminal voltage drops below 12V when you get to having drawn 50% capacity out of them.

I'm sure I'm going to regret saying the next, but I would appreciate your's and George's views on that hypothesis.

Dave


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## Scotjimland (May 23, 2005)

I'm settling down with a large coffee jug.. it's going to be a long day :wink:


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## thehutchies (Jun 25, 2005)

As James Joyce said:

'Agonising Christ, wouldn't it give you a heartburn on your arse? '


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## gaspode (May 9, 2005)

Forget the theory, if you *plan* to get half the rated output (ie. 11 amps for 5 hrs) then:

a) you won't be disappointed

and

b) you're unlikely to knacker your battery


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## 88724 (May 9, 2005)

Hi Rapide

On your initial question, If the battery was fully charged to start with, at 5.5 Amps used per hour the battery would (under Ideal conditions) last 20 Hours (the 20 Hour discharge rate is how manufacturers rate their batteries)

On paper at 11 amps it should last 10 Hours, but the Peukert's rating will lower this. About half way down the following -page there is a discription and some diagrams

a Good explaination of batteries on the net, still incorrect in some parts but overall pretty good

It as been mentioned that in reality you do not want to discharge a battery fully, In Franks opinion you can discharge to 90%, however I disagree (and more importantly so do the battery manufacturers, see the above link and for further evidence look up battery manufacturers and what they say)

Note also that manufacturers will show a graph thats says something along the lines of

if you take 10% out and recharge the battery will last 6,000 cycles
if you take 20% out and recharge the battery will last 5,000 cycles
if you take 30% out and recharge the battery will last 4,000 cycles
if you take 40% out and recharge the battery will last 3,000 cycles
if you take 50% out and recharge the battery will last 2,000 cycles

etc etc, by the time you get down to 80 or 90% take out from battery the life expectancy is dire.

Fully recharging is another thread entirely, but suffice to say the usual onboard chargers (zig & similar) will only charge to about 90% if left chargibng for 4-5 WEEKS. If you use split charge relay the max is around 70% full

At 70% full to begin with and with a maximum reccomended discharge of 50% that only leaves 22 amphours............

I'll get my coat


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## Rapide561 (Oct 1, 2005)

*amps*

Hi all

I think I get the idea!

Rapide561


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## Scotjimland (May 23, 2005)

Good post George.. thanks


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## DABurleigh (May 9, 2005)

Any thoughts on the terminal voltage at the higher currents and low temperatures George?


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## 96783 (Nov 23, 2005)

Oh I do enjoy these threads and, as Scotjimland says, it could run and run and another cup of tea (sorry, don't like coffee) is definitely called for. They're always instructive though and I'm happy enough about that. Surely for most of us, most of the time, the answer is not to discharge to silly levels and to have a decent stage charger to ensure safe recharging.


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## spykal (May 9, 2005)

Hi

Good posts ....

My thoughts a bit off topic, but relevant I hope:

We use our van mostly for stays away of 3-4 days, long weekends and some mid week breaks. We do occasionally take longer trips but the average is 3-4 days.

For most of us who like to camp without hookup.... all we are after is longer on site without resort to a hook up or generator or even solar panels. I know that those who have either a solar panel or a generator will say that that is the way to go but I do not want the noise from a generator or the expense of fitting an efficient solar panel.

So for what it is worth.... I use a couple of the cheapest bog standard lead acid leisure batteries and I *do* abuse them.....take them down to 50% and below almost every trip, that is almost every week in the summer and once a month or so in the winter. But with the aid of a decent charger (not the onboard Zig but a Ctek) my batteries are still in good nick, one is coming up to 3 years old the other is a year old. I try to get them on charge on the Ctek as soon as possible after our 3/4 days away...I know that the alternator will bring them back up as soon as we travel but the Ctek finishes the job properly.

The point I am making is that for around £28 each (85 amp) I get excellent value from my leisure batteries. When I suspect that I am not getting the usual service from one of them £28 spent will bring the situation back to normal. I know that there are much more sophisticated batteries available but in my opinion unless you have a special need for them buy a decent charger ( Sterling or Ctek) and budget lead acid batteries and change them when necessary.

Mike

P.S. I do use my batteries in a slightly unconventional way.....the two 85 amp Leisure batteries are not connected together when in use, but can be if necessary when charging from the altenator ( another minefield I know...different charge states ect...but it works for me). One supplies the essentials (lights, water pump, fan for blown air) the other supplies the entertainment suite...TV, computer, freeview box and Dvd. We do not use the TV very much but if the entertainment battery gets used up we just don't watch any more TV....this makes sure that we always have power for essentials :roll:


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## olley (May 1, 2005)

How long do you expect your batteries to last? would you be happy to replace them every five years?

I try to get away as much as possible but I doubt this is more than 60-70 days a year including our main holiday, so thats 60-70 recharges per year, so it seems to me that if I do abuse them they are still going to easly last five years. so I will continue to abuse them :lol: 

Olley


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## 88724 (May 9, 2005)

DABurleigh said:


> when you draw those sort of currents in the ambient temperatures we "enjoy" (brrrrr...) in these sceptred isles, the terminal voltage drops below 12V when you get to having drawn 50% capacity out of them.


Hi Dave

I missed this, sorry, but here goes better late than never..

First off, Voltage measured is rarely the TRUE terminal voltage, If you were to measure straight after starting the vehicle the voltage can be below 12v this soon rises again (Peukerts explains the lowering (of terminal voltage), its the reason for the starting voltage effect), in the same vein after charging it may show 13.5 volts or so and will soon settle lower, however to get the true voltage you would need to wait at least 12 hrs with no usage or charge.

Cold does effect capacity and terminal voltage of the battery, nothing as really changed except the battery's ability to supply at that point, ie warm it up again and the capacity returns (unless the battery as died....)

Batteries charge quicker and more fully in hot weather and vice versa slower and less fully in cold weather, ie even a zig will do better in hot weather, in cold weather it will be worse than its usual useless performance.

So to answer your question, yes it would *appear* to be lower than 12v, but the reality would be higher, after the battery as settled (and if returned to normal temps)


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## DABurleigh (May 9, 2005)

George,

I've been meaning to come back for some time on the "only 70% full" from an alternator.

I have a Victron 4 stage charger, albeit set in the default battery-safe mode to minimise gassing. I also have the Victron battery meter that integrates current over time while simultaneously integrating Peukert, etc.

Now, once it goes to float charge on mains, the "Battery full" flag comes up. If I then use the van away from mains, even at highish currents using plenty of satellite TV and eberspacher glow-plugs, taking the capacity down to 50%, the alternator gives it 35 amps for quite a time, but then decreases down to ~20 amps, then gradually lower and lower (the sense is still on the vehicle battery I guess, and I have a normal split-charge arrangement). BUT, the key point is that after a LONG drive, I do get up to 95%, and it doesn't take long once I get home for mains to get it to 100% when it goes back down to float.

All grist to the mill.

Dave
Edit - our posts crossed. Thanks.
"yes it would appear to be lower than 12v, but the reality would be higher"
But when the appliances cut out at 11.7 volts, they don't want to hang around until I've let the battery rest ....... :-(


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## spykal (May 9, 2005)

DABurleigh said:


> George,
> 
> I've been meaning to come back for some time on the "only 70% full" from an alternator.(


Hi Dave and George

My findings are much like DAB's. Often on return from a long drive after a three day trip ( so the battery will have been well down) I find that when connected the Ctek charger will indicate that the Leisure battery has been fully charged from the altenator. In other words it will not go into charge mode when connected to the leisure battery....I have often wondered about this because most pundits do say that the altenator will not fully charge the leisure battery....so what is going on here? If I leave the battery for a day or so and connect the Ctek it invariably goes into charge mode for a short time..returning quickly to the maintenance mode....which I assume to indicate fully charged.

Mike


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## 88724 (May 9, 2005)

Hi Dave

*I've been meaning to come back for some time on the "only 70% full" from an alternator.*

Yes I know 70% is a bit high  most experts are indicating that 65% is the most that can be expected. I always give the benefit of the doubt....

*I have a Victron 4 stage charger, albeit set in the default battery-safe mode to minimise gassing.*

This only delays the gassing, charging is an electrochemical process, which will create the same amount of gas just take longer doing it at lower charge rates..

*I also have the Victron battery meter that integrates current over time while simultaneously integrating Peukert, etc.
Now, once it goes to float charge on mains, the "Battery full" flag comes up. If I then use the van away from mains, even at highish currents using plenty of satellite TV and eberspacher glow-plugs, taking the capacity down to 50%, the alternator gives it 35 amps for quite a time, but then decreases down to ~20 amps, then gradually lower and lower (the sense is still on the vehicle battery I guess, and I have a normal split-charge arrangement). BUT, the key point is that after a LONG drive, I do get up to 95%, and it doesn't take long once I get home for mains to get it to 100% when it goes back down to float.*

Dave,

This last bit is extremely hard to explain *briefly*, but if you leave the battery after the trip home for 12 hours and then connect the charger you will see, it will take a lot longer to charge.

Easy test, deplete battery at home, run engine for a while, until you and Victron think you have 95%, then leave 12 hours, connect charger and it will take ages to charge.

catch you later


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## 88927 (May 10, 2005)

Hi guys
Great thread. So to cut a long story short (and I know it has all been said before) what is the best way to charge the batteries to achieve the best charge rate and does leaving the batteries hooked up to the mains charger do them good or harm? Is there a simple way to determine the depletion of the batteries if not on hook up ie a meter of some kind, or do you just extrapolate from the terminal voltage reading?

Thanks

Keith


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## Rapide561 (Oct 1, 2005)

*Amps*

Hi

well I feel I am now much more aware of the subject of AMPS!

And batteries

Thanks for the input

Rapide561


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## 92046 (May 1, 2005)

*Mine Field*

Hi To All

The "Battery Reference Book" by T.R. Crompton. (Butterworth)

This is a BIG THICK book, this is just one of my electrical reference books, often used in a previous life as a senior electrical engineer, and "*"NO"*" i will not quote from it, as it now a few years old and may be a little out of date 8)

However I personally use a Sonnenschein 85 Ah battery of 1994 vintage, as a single battery, and has been discharged to 50% on a regular basis,

Also when on longer (5000 mls), or winter journey in the north of UK, I use 2 x 85 Ah Sonnenschein batteries of 1997 vintage, in both cases connected up to 2 x 50 watt solar panels, again often discharged down to 50%,

In the north of the UK this set-up is OK for a week or so in Dec/Jan, if no TV etc is being used, in the south of UK or France etc, this set-up works well for me, but I do not use a TV, the CD/radio is run from the engine battery, and 20 watt solar panel if required.

Good luck 
Colin R......


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## DABurleigh (May 9, 2005)

"Easy test, deplete battery at home, run engine for a while, until you and Victron think you have 95%, then leave 12 hours, connect charger and it will take ages to charge."

George,

I haven't done this, as once home during summer I leave the solar panel doing its thing, and in winter I connect immediately to mains to leave an oil radiator on frostat.

I will after the next trip, but for now I note Mike HAS done this, and it wasn't as you claim, the mains charger going soon to float after the battery had settled for a day or so. In other words, the alternator had hacked it.

I'm seeing Clive MMM's 12V technical consultant tonight, so will seek his views. With a lifetime in fork lift truck 12V electrics I'm sure I'll get plenty.

Dave


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## spykal (May 9, 2005)

GeorgeTelford said:


> This only delays the gassing, charging is an electrochemical process, which will create the same amount of gas just take longer doing it at lower charge rates..


I am not sure that I should comment on this because of my limited understanding ..but that understanding is .....that lead acid batteries only start to gas when you attempt to charge them faster than they can absorb the energy. So a correct charge rate does not produce excessive gassing.

Mike


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## DABurleigh (May 9, 2005)

Charging voltage is key, too, Mike, in determining gassing or not:
http://www.victronenergy.com/TechnicalInfo/TechPDF/Adaptive charging how it works.pdf

Sorry, Keith, we've been remiss in not addressing your query:

1) Don't charge the batteries at a greater current than 1/5th of its capacity (so 40Amps for 200Ah, say). Frank says preferably less than this.

2) Use a multi-stage mains charger/ power supply, say Sterling or Victron or similar. I haven't checked but some C-Tek charges are just for battery maintenance I think. These all automatically change to a floating voltage of 13.5 to 13.8V and can be left running for LONG periods no problem.

3) If you REALLY want to know the residual capacity/ state of charge, a battery monitor that measures and integrates current in and out is handy. Necessary? No, of course not. Convenient? Absolutely.
http://www.victronenergy.com/upload/documents/Datasheet-UK-BMV501BattMonitor.pdf

Dave


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## 88724 (May 9, 2005)

Hi Mike

if you were to check a battery that is being "charged" by a zig (and I use the word charged in the loosest possible sense)

You will notice if you were to remove the caps little bubbles forming on the plates and then gently rising to the top, I did have the chemical formula that shows the reaction on charging and discharging, which explains why the gas is formed, if it isnt gassing it isnt charging.

Dave, Mike

Here is a Quote from Collyn Rivers
*
As noted in Chapter 2, 14.2.14.4 volts output is a compromise. It's high enough to spin the starter motor, but also low enough to prevent overcharging unless the vehicle is driven non-stop for days on end. But that 14.2.14.4 volts output is too low to charge any conventional lead-acid battery beyond 70.75% in any practicable length of time.

Experts in this field are increasingly quoting 65% as a more realistic norm. *

From the free Chapter here

http://www.caravanandmotorhomebooks.com/books/motorhome_electrics_caravans_too.htm

Next Victron and Sterling amongst others would be doing the equivilent of selling snake oil by selling Smart regulators if alternators were any good at charging.

Sterling on alternators and smart regs http://www.sterling-power.com/htm/ar12vd.htm

Victron http://www.victronenergy.com/product.php?productid=163

Quote from Ardverc

*
ADVERC voltage control of the alternator and battery sensing, results in 100% state of charge compared with 60%-70% using standard regulation, at a faster rate of charge and safely.*

Tests that I did a few years ago all, show the same results, alternator charging doesnt get anywhere near 100%, In fact a fully charged battery which recieved an extra 1 hour 14 mins of Alternator charging actually lost 52 mins of usuable power, compared to not having the "extra charging" from the alternator.

Mike, does your motorhome have a smart reg fitted?


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## 88927 (May 10, 2005)

Thanks Dave
I had a quick look and the whole subject of battery charging makes my head spin, maybe next time we meet we can have a chat about it in plain english over a brew :wink: :wink: 

Keith


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## 88724 (May 9, 2005)

Hi Keith

The plain English version is

1. Get a good quality charger 3-4 Stage

2. Do not use a split charge system

3. Do not discharge below 50% (easiest way to see that is a battery management system, it aint cheap though) the other way is to fully charge and moniter (add up) your average usage. 

Find the settled voltage of your fully charged system, charge with a good charger (see point one) allow battery to sit unused for 12 hours minimum then take a voltage reading this is your 100% point 1 volt below is completely flat so 50% is .5 Volt down from 100% reading, while away if you measure in the morning before any power usage will give a pretty good indication of State of charge.

Rule four make sure you follow rule one.

Rule 6 if you dont want long and complex answers do not question rules one to six


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## DABurleigh (May 9, 2005)

I only found rule 5 simple 

I had to pop to the van tonight to get my Brompton out, and I made a point of checking the battery monitor. Just 20Ah has been put in by the mains charger since I returned home charging on the alternator. I have 200Ah battery capacity, so only another 10% has been put in.

I had a ragchew with Clive tonight and I'll send him this thread link so he can jump in if he wants.

My only thoughts at squaring this circle, George, is that to REALLY maximise the charge in a lead acid battery, you have to go above the critical gassing voltage up to 2.7V per cell, 16.2V total. The downside is you will frequently have to top the cells up. However, if this is your 100%, then even my Victron 4 stage adaptive charger doesn't go there. See page 21 of:
http://www.victronenergy.com/upload/documents/Manual-ML-PhMultiCompact.pdf
for my charging voltage and current with time in the default battery safe mode. I have checked my batteries 3 times in almost 12 months, and no topping up has been needed, despite charging at 40A and discharging at up to 100A for short periods (longer if Alison's drying her hair and I'm not there to stop her .....)

Dave


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## 88724 (May 9, 2005)

Hi Dave, all

Gassing is not the same as losing electrolyte, otherwise we would all be in trouble and topping up all the while, electrolyte loss is electrolyte that is "evapourated" off by rapid charging which as warmed up the battery.

The above should not be mixed up with boiling the battery or thermal runaway.

Not sure where this critical gassing voltage of 16.2 comes from, charging causes gassing, no gas = no charge have a look at a cell in your car battery at tick over, it will be bubbling away gently those bubbles are gas being formed car will be running at around 13.8 to 14.2 well below the gassing voltage you mention and do any of us actually ever top up the starter battery?

Ask any of these companies that mention this mythical charging without gassing if its OK to have a naked flame near the battery when being *charged below the gassing point* that they _*claim*_ exists, I have asked and its amazing how quickly they clam up. Ardverc even claim to charge above and below gassing voltage quote *(By cycling the battery voltages above and below the gassing point of the battery)*

Apply a little logic to the following Ardverc statement

*The underlying principle is that batteries should be charged fully, quickly, safely and without damage to batteries and alternator. This is achieved, firstly, by cycling the battery voltages to an established programme, at a nominal 14.0-14.4v (12v systems) or 27.5-28.5v (24v systems).

The cycling programme is normally: 5 minutes @ 14.0 volts, followed by 15 minutes @ 14.4 volts. After four 20 minute cycles, there is a 'rest period' of up to 40 minutes i.e. at the lower voltage, depending on the battery state-of-charge and electrical duty-cycle.

These voltage values lie either side of the battery gassing voltage, ensuring rapid charging without the battery actually gassing.*

My italics

Logical progression; gassing only occurs between 14v+ and under 14.4v (depending on temperature)

So no lead acid battery will produce explosive gas if charged above 14.4 Volts or just under 14 volt's?

Below is Electricity on board by Reinout Vader (Victron)

A damned good read, highley reccomended

http://www.victronenergy.com/upload/documents/ElectricityonBoard_rev8_july2004.pdf

The gassing bits wrong, but eh ho, you could always ask if he (they) would be happy for you to light a flame near a charging battery and see if he has (they have) the courage of his/their convictions Check out 2.2.2 for another different take on gassing.


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## DABurleigh (May 9, 2005)

I didn't say the critical gassing voltage was 16.2. It is usually taken to be 14.4. The relevant bit is in one of my earlier links, extracted here:

"Often the absorption charge voltage of a battery does not exceed the gassing voltage limit (approximately 14,4 V for a fully charged 12 V battery). Some batteries however need a higher absorption voltage to fully charge them (tubular or thick plate deep cycle batteries for ex.), and open, flooded, batteries in general can be charged faster by not only increasing the bulk charge rate, but also the absorption voltage. A high charge rate will heat the battery (temperature compensation needed!)
and will also increase gassing, in extreme cases up to the point that the gas bubbles will push the active mass out of the plates, destroying the battery. The BatterySafe mode limits the rate of voltage rise of the charger output after the gassing voltage has been reached. The effect is a sharp drop in charge current which prevents excessive gassing"

Dave


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## 88724 (May 9, 2005)

DABurleigh said:


> I only found rule 5 simple


well spotted, truly you are an eagle among men

I ommited rule 5 its off topic, because rule 5 is not about batteries

Rule 5

Wer mit Ungeheuern kämpft, mag zusehn, dass er nicht dabei zum Ungeheuer wird. Und wenn du lange in einen Abgrund blickst, blickt der Abgrund auch in dich hinein. Freid Nietzsche

Wilkepedia notes

Translation: He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you. 
Aphorism 146 
Source: Gutenberg-DE 
Translation source: Hollingdale

You can lead a horse to water, But your batteries must be lead

BTW this is a totally lighthearted, jokey post with no disguised messages or attacks


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## 88724 (May 9, 2005)

Hi Dave



DABurleigh said:


> I didn't say the critical gassing voltage was 16.2. It is usually taken to be 14.4.


I have just extracted this next quote from your previous post

"My only thoughts at squaring this circle, George, is that to REALLY maximise the charge in a lead acid battery, *you have to go above the critical gassing voltage up to 2.7V per cell, 16.2V total." *

Am I missing something subtle?


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## sallytrafic (Jan 17, 2006)

I have been carefully following this thread, looking up references where given and trying to come to a pragmatic view on battery charging that whilst not ignoring inconvenient facts keeps the object in view.

The most telling posts in my view haven't been the carefully reasoned and accurate ones from Dave and George but those by Mike and Olley near the begining. Basically I believe they are saying 'Yes but....' and the 'but' is about whole life economy.

In what follows I illustrate the extreme case to make the argument easier to follow.

To achieve 100% charged batteries and say, 6000 cycles (15 years?) the costs are:

Expensive charging and monitoring equipment that as far as practicable ensures that the electro-chemical reactions go to the end points at both positive and negative plates of the battery (ie gets the battery more than 65% charged) without permanent damage to the battery and excessive loss of electrolyte.

Carrying the weight and finding room for 10 times more battery than the AmpHr rating would indicate (assuming discharge only by 10%). Along with the costs of the purchasing 10 times more battery. 

At the opposite end of the spectrum is split charging and taking the battery down to 90% discharged. ie abuse at both ends. How many cycles - well 300 or 400 perhaps. How much does that cost? Shall we say new batteries every 2-3 years.

Which you choose is up to you but if you have a large RV, are a full timer and want absolutely to rely on your batteries then go for the sophisticated system, if like me you have a small van, hope to be able to get away 60-70 days a year then you might want something smaller, simpler which also might be cheaper over the life of the vehicle.

As usual once you figure in cost and convenience the science and engineering can take a knock. The science doesn't change because of the economics but the path that you choose might. Good engineering keeps the needs of the user firmly at the forefront.

That said a thread that explores and debates the science/engineering is much more interesting than cost benefit analysis so lets have the next question 

Or we could do the same question over but this time include all the different battery types :-D


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## DABurleigh (May 9, 2005)

"Am I missing something subtle?"

You are inferring that I said the critical gas voltage is 16.2V, whereas I didn't say that. My words are entirely consistent with that voltage being around 14.4V.

Rearranging the phrases
"you have to go up to 2.7V per cell, 16.2V total, above the critical gassing voltage" 

Dave


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## 88724 (May 9, 2005)

Hi Dave

I see what you meant to say now, the clue I suppose is in *up to* 16.2 Volts. Anyway either way critical gassing voltage is an "adspeak" nonsense, if you are charging then the batteries gassing

Hi Frank (SallyTraffic)

I understand your use of the extreme case for illustrative purposes, just for completeness lets add the middle ground.

Buy a £45 4 stage charger (not really expensive, far cheaper than a Zig "charger" Offsetting this cost will also be the savings on replacing the batteries ie the service life will be longer.)

Discharging to 50% giving say 2000 cycles (on my "for example" chart posted earlier)

You can get a reasonable idea of your usage by "monitoring" an "average" couple of days.

In summary.

1. Your useable amphours are up
2. Not expensive savings in replacement batteries would easily exceed cost of battery charger (one battery costs as much as a basic 4 stage charger from Sterling)



> Frank said *"As usual once you figure in cost and convenience the science and engineering can take a knock. The science doesn't change because of the economics but the path that you choose might. Good engineering keeps the needs of the user firmly at the forefront."
> *


Figuring in cost and convenience, I believe the middle ground described above is actually cheaper in the long run, its more convenient for the user's use of his/her vehicle (in Amphours and longer service life) Its even better enviromentally as there are fewer duff batteries to contend with.


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## DABurleigh (May 9, 2005)

Clive is following this thread, but refuses to post to a subscription site as a matter of principle (even though at present you don't need to subscribe to post).

Dave


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## 88724 (May 9, 2005)

Isnt the MMM forum a subscription site then? I thought you had to buy a magazine to use it (officially at least)


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## DABurleigh (May 9, 2005)

There are principles, and principles that are deployed in an attempt to justify pure emotion....

http://www.motorhomefacts.com/ftopicp-103870.html#103870

Dave


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## 88927 (May 10, 2005)

Dave.... Don't go there mate :wink: :wink: :wink: 

George, thanks for the info, and I hadn't realised that you could buy a decent charger for so little money. In our RV we seem to have a transformer set up to sort out the 110 volt issues and also a charger somewhere. Would you recommend replacing the existing charger for a 4 stage one? I guess you would :lol: I shall have to get it checked out to see if one can easily be dropped in without rewiring up the entire system.

Keith


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## Scotjimland (May 23, 2005)

kands said:


> Would you recommend replacing the existing charger for a 4 stage one? I guess you would :lol: I shall have to get it checked out to see if one can easily be dropped in without rewiring up the entire system.


I've looked at this option for Georgie, ... birds nests and a can for worms come to mind :lol: :lol:

Good thread so far 8)


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## olley (May 1, 2005)

I just want to add to my earlier post, if I spend some money on a decent charger, so that my batteries last 10 years, whats the point if I sell it after 3? most motorhomers/RVer's don't keep the vehicles a long time, so whats the point.

Also I have 2x85 amp connected to 2x105 amp another no no but if I run low I simply start the genny for 15mins, I can get a lot of power for just a little petrol :lol: This to me is the real world, and it works for me.

Olley


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## Scotjimland (May 23, 2005)

Another thought, If you spend most of your time without a mains hook up then spending a lot on a sophisticated mains charging system seems a bit daft. 
On the other hand, if you prefer to be on a hook up most of the time you don't need to worry if your battery only reaches 70% from the alternator .... either way unnecessary. 

If you prefer not to be on hook up a better investment would be a decent solar charging system.. with a gennie as back-up. :wink:


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## 88724 (May 9, 2005)

Hi Olley

Hang on, you buy an RV for loads of money sell after 3 years with a not insignificant price drop and yet £45 for a decent charger bothers you?

The point is that you probably lose more money juicing the genny to replace what the charger would have done for you.

Obviously you need more power than you were getting in the RV, hence the extra batteries you have fitted, would it not have been better to fill the two that you started with, before buying extra batteries to underfill?
Would have been lighter and cheaper to buy a decent charger.

Everything in your post says you would have been better off buying a decent charger.


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## DABurleigh (May 9, 2005)

I have but a mere philosophical point.

It strikes me that people's "solutions" are all different, but they defend/justify their particular one to the hilt (and I'm no different).

The question is, is it because everyone's needs ARE different, and everyone HAS got the optimum solution for themself, or is it simply because it is human nature to defend one's past decisions, but in truth there really is a smaller set of sensible motorhome battery/charging solutions we ought to be deliberating over?

Dave


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## 88724 (May 9, 2005)

Hi Jim

Lets look at your solar system idea, costs a grand to get any *worthwhile *power.

A decent charger, lets go up to 30 A to minimise genny usage say £250 run the genny for half hour and it will produce more power than the solar system will all day and be far more reliable producer of power.

Wild camping, a smart reg will turn your alternator into a superb charger for £100 then every trip gives you a good charge. Or run the mains charger via invertor..........................

For weekend travelers (off grid) a small charger £45 will double the amount their present battery can supply (as long as you dont split charge when traveling)

But everyones needs are different, there isnt one size fits all, but a decent charger is a good start to most systems.


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## homenaway (Jul 27, 2005)

I've been following this thread with interest but from George's last posting as I understand it I could connect my basic modified sinewave invertor into the starter battery and charge the leisure battery while driving around via a CTek mains 4 stage charger or similar instead of using the split charge relay?

Will the charger run ok from a rough mains input?

At present we just run the standard zig (or Plug in Systems) setup with a cheap 85Ah battery and use a hookup maybe every third day.

This has been ok for three years of moderate usage.

Steve


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## Scotjimland (May 23, 2005)

Hi George 
I see where you coming from, advice and discussion before spending £1k + on solar panels is well worth while. Bear in mind I need my system for fulltiming without a hook up if possible. 

You say 
Quote:
" A decent charger, lets go up to 30 A to minimise genny usage say £250 run the genny for half hour and it will produce more power than the solar system will all day and be far more reliable producer of power." 
Un Quote

That would produce 15ah .. more reliable , yes but in practice I would need to run the genny a bit longer than 30min to recharge each day, maybe 4 hours or more giving 120ah.? 

My conclusion: 
I should invest the £1k+ in solar panels and upgrade my charger to a decent 30A job for rainy days or when on hook up.. 

Is that a fair assessment ?


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## olley (May 1, 2005)

Hi george which is easier to fit 2 batteries or 1 charger.

1) drop two batteries into basement storage connect upto existing, job done

2) Remove existing 110v 50amp 2 stage charger and fit new 240v 4 stage charger with associated new wiring.

I will go for option 1 

In real life am I ever likely to notice a difference in performance between the two ways no.

If I discharge to 50% on your method I get 85 amps if i do it my way, (when the lights go out i start the genny) 90% of 380=342 amps. even when they are knackered I expect to get maybe 150 amps. 
Sorry no contest.

Olley


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## 88724 (May 9, 2005)

Hi Jim

120 AH which you want reliably day after day? In Australia to get that reliably would require 10 Panels!! to get it only in the summer would need 5-6 Panels, Cant imagine the amount of panels you would require in the UK, northern europe. Have you got enough roof space and money? 

If you really require that kind of power, what about a serious battery bank and 1 day in 10 on a site to fill tanks empty waste and charge up etc.

I cant imagine you really needing that much power.

Probably best to start another thread for your system, could the mods move these posts to a new thread?


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## 88724 (May 9, 2005)

homenaway said:


> I've been following this thread with interest but from George's last posting as I understand it I could connect my basic modified sinewave invertor into the starter battery and charge the leisure battery while driving around via a CTek mains 4 stage charger or similar instead of using the split charge relay?
> 
> Will the charger run ok from a rough mains input?
> 
> Steve


Hi Steve

yes I have tried it with the Sterling, which is OK with 80v to 300 V 40 to 400 Hz input

But I even tried a cheapo and that worked too


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## 88724 (May 9, 2005)

Hi Olley

I do understand what you have done. I can even see where you are coming from with it

You ask which is easier, adding two wires to the battery bank and then plugging in the new charger, time 5 mins? sorting leads and siteing 2 new batteries as got to take longer.

If it had been me I would have gone for the charger and added 2 85's to the existing pair (or changed the whole lot for 110's) 

Mixing and matching is causing poor charging and the discharging will be adversly effecting the bank too.

Anyone who as ever mixed batteries in a torch (or any other item) will know that they do not last as well.

But eh its your system, your money and your choices.

Regards

George


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## Rapide561 (Oct 1, 2005)

*Post*

Hi

I was told my original post would run and run!

How right you were - but I have learned a lot!

Rapide561


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## spykal (May 9, 2005)

Hi rapide

Was it the Carpenters who sang ..."We've only just begun"..........or Mike and the Mechanics?

Mike


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## DABurleigh (May 9, 2005)

"How right you were - but I have learned a lot!"

And to prove it you can declare the answer to your question here.

;-)

Dave


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## 88927 (May 10, 2005)

Hi Mike (without the mechanics :lol: :lol: )
The Living Years is the song you are looking for mate :wink: :wink:

Keith


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## Rapide561 (Oct 1, 2005)

*Carpenters*

Hi

Karen and Richard CArpenter - We've only just begun!

Rapide561


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## daveandcarol (May 21, 2005)

Maybe a little off topic but I found this interesting chart as regards voltage against state of charge.....


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## 88724 (May 9, 2005)

Hi Dave

In the UK A fully charged battery will be typically around 12.8 12.9 volts when fully charged, which would make 12.3-4 the 50% discharged voltage as long as it is rested by the time you measure.

A voltmeter can give a rough indication of the battery condition only when there has been no load on the battery for some time, or when the battery has not been charged for some time. When there is a fridge and TV running, the voltage will be lower by some amount depending on battery size and current draw. Similarly, when charging, the voltage will be higher and depending on charger size, the voltage can be the same when the battery is still flat or almost full.


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## haylingchrist (May 15, 2005)

I think the rule with batteries is you always get a lot less than you expect.

I did a run-down test on a 6 month old Exide 110ah battery using a 4.5 amp load, taking the voltage and SG every 30 minutes or so.

Based on the SG readings the total capacity of the battery was 54ah. Obviously, the usable capacity would be, at best, about half this. Recharging the battery from 75% discharge at the end of the test showed a total capacity of 47ah.

After a lot of phone calls to Exide I got to talk to their technical expert who agreed with my test method and results, thought the capacity was 'a bit low' but refused to replace it...

The attached zip contains a spreadsheet of results.

I'd say this sort of performance is pretty typical based on 3 vans and loads of disappointing lesiure batteries.


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## nukeadmin (Oct 10, 2003)

hiya Chris, hows the full timing lifestyle treating you and where are you at present


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## 88724 (May 9, 2005)

Hi HC

Couple of questions, what charger were you using ? Its seems to be set for Gel/AGM is the battery a gel or AGM?

The SG at the start is very low (again is it AGM? they have low SG's) According to normal UK specs fully charged standard lead acid would be *in excess* of 1.265 @25 C

Does it weigh aprox 33.5 KG?

BTW wow I wish I had your discipline for noting results


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## haylingchrist (May 15, 2005)

(Dave, full-time is great. The only fly in the ointment is that I have to do a bit of work to make ends meet 

Charger was a Sterling 30amp switch-mode job. Battery is normal (cheap) wet flooded.

Not sure what makes you think it was set for gel as the charge peak is 14.7V this would be far too high for gel (14.1 or 14.4 depending who you speak to).

Actually in trying to get decent charging performance from this charger with very cold batteries I've been inside numerous times and tweaked the 'pots' having spoken to Sterling at length.

Yes I agree on the SG readings, but that's where it was after several days charging. I got some really strange readings in the Alpine winter - it would hardly register on my hydrometer... I found this hard to believe and bought a posh one from the battery supplier but the readings weren't much different. Everyone assured me that SG readings were the only true measure and were true during charge/discharge.

Not sure of the weight, it's long gone.

Rigor on results only came 'cause I thought I might get a new battery...


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## 88724 (May 9, 2005)

Hi HC

I must have misread the Voltage when I read your spreadsheet first time, its clear as day now. Thats a damned good charger (same one I have)

BTW they owed you a new battery without a doubt, them SG's and charging results are way off for a straight lead acid battery.


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