# How good are my Batteries



## papaken (Nov 21, 2010)

Have just charged my van and hab batteries over the last couple of days  and was wondering what a fully charged battery should read?

Van batt was 12.5v at start and after 8hrs charge and rest was 12.72v.
hab batt was 12.36v and also 12.72v at rest.

Can anyone give me an idea what a fully charged batt should read. :? 
Last winter I left both batts and they were both fine come Febuary. 

Also had no heating in van and no problems just a fortnightly check so here's hoping this winter. 

Forum Helper - This thread moved from New Feature Requests


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## Sideways86 (Feb 25, 2009)

They look ok to me, if you take them to a battery dealer/supplier they can out a load test on them and give you a comprehensive evaluation.


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## peribro (Sep 6, 2009)

See this chart:


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## listerdiesel (Aug 3, 2012)

Leaving them over winter is not good for them, if you cannot get a small charger on to them that will keep them topped up (and I mean a proper float charger) then give them a monthly charge.

You probably lose 5% capacity or more during a 4-month layup with no standing drain on the battery, the more frequently you keep that replaced, the better battery the battery will be.

Lost capacity isn't just a matter of charging the battery up to replace it, you never really recover it, once it has gone it is gone.

For most people, the loss of as much as 20% capacity isn't noticed, but the life of the battery has been shortened.

Note that commercially a battery is at the end of its life when the available battery capacity has fallen to 80% of its new value. In practice most batteries continue to serve well even when the capacity is much lower.

Peter


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## midgeteler (Jul 19, 2009)

I was worried about the state of my elecsol hab batts and after taking advice from those on here, asked Halfords if I could bring them in to be checked. The answer was that they would/could not test leisure batteries.
Is there anyone else?


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## pieterv (Feb 3, 2009)

It makes sense not to test leisure batteries with a set up meant for starter batteries. They draw a large current and judge the state of the battery by the amount of voltage drop.

This is fine for starter batteries which are meant to supply a large current for a short amount of time. Leisure batteries however are meant for smaller currents over much longer periods of time, so cannot be tested this way. It can lead to damage.


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## barryd (May 9, 2008)

So how do you test a leisure battery then?

Im sure our single 110AH Battery must be on the way out. It coming up 7 years old. Since we got the van in 2008 its been used constantly for at least half the year.

It was fine all summer with the solar panel but in late October early November the charge didnt seem to be lasting as long as before. Maybe 2-3 days. However I was checking the voltage when things were on like the lights or maybe the TV. I noticed when I checked in again in the morning it had gone back up a bit. I never let it go below 12.1 but underload sometimes it reads less than this. 

So how do you check it?


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## listerdiesel (Aug 3, 2012)

There's no difference in practical terms between a leisure battery test and a vehicle battery test, you check to see if the battery will support a short high-current load for X seconds. What you are testing for is the ability of the battery to support high current loads and thus prove that the cells and internal links are OK. It is not a capacity test.

A full discharge capacity test is the same for both batteries, you load the battery up with a discharge current at the C/20 rate and see how long it takes to discharge, you can then calculate the removed capacity and also recharge it immediately. It takes up to 20 hours at the C/20 rate.

We design and manufacture discharge testers for the rail industry, usually up to 110V nominal battery voltage and up to 300ah capacity.

Peter


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## jd_boss_hogg (Aug 26, 2009)

Just tacking my question into this posting, in that i have a new camper, 2 new leisure batteries coupled. I dont know if they are 2x90a, or 2x77a, because they say both on the battery ! I have a solar 100w panel. 

After our very first trip, we thought the batteries were not lasting as long as our previous vans, when we expected more (bigger capicty, bigger panel). So, after a 5 hour drive home we parked up with what we thought would be full batteries. 

3 days later, hardly been in the van and the odd LED light has been on for a short while, our control panel in the Rapido shows 50%, 12.3v. I've tested both leisure batteries, and they have the same voltage, so i guess they must be wired up correctly.

Does anyone think that the "50%" level doesnt actually mean a true 50% charge, but perhaps it means we are 50% towards the 'danger zone' according to peribro's chart?

Even so, 12.3v seems a long drop from 12.7, when we havnt been in the van or doing anything, especially being as the solar panel looks like it is pulling 1a for 5-6 hours a day ?


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## pieterv (Feb 3, 2009)

barryd said:


> So how do you test a leisure battery then?


As Peter said, with a lower discharge current and see how long it can support that. I wouldn't go for a full/deep discharge as this isn't good for the battery.

You could discharge until the voltage drops below 12V. Then let it rest for a while and use the table above to determine remaining capacity (the voltage is only a reliable indicator of charge after the battery has had a good few hours of rest).

So, your capacity would be the remaining capacity (indicated by rest voltage) plus the number of Ah you took out during your slow discharge (current x time in hours).

Note, that the capacity in Ah is not a fixed number, it depends on discharge current. Greater current, less capacity (Peukert's law). So a battery might have 100Ah when discharged with 10A, but only 80Ah when discharged with 20A.


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## raynipper (Aug 4, 2008)

50% after only 3 days indicates some serious parasitic loads. This can only really be checked with an ammeter in series to the leisure batteries.
Modern vans do have more and more parasitic loads with auto fridges, radios, alarms, engine data chips.

Ray.


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## Sideways86 (Feb 25, 2009)

As Ray is saying, even with nothing going on you will be getting a drain the secret is to establish what that drain is

Disconnect your positive terminal and connect ammeter in series to positive lead.

Please be aware it will take up to an hour to establish a stable current draw because modern systems shut down in stages.

Target figure in my humble opinion would be around .20 to .25 drain max.


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## listerdiesel (Aug 3, 2012)

You have to be careful with interpreting voltages.

First of all, 'gadget' voltmeters are not terribly good, and I'd want to see a voltage on a professional DVM, something like a Fluke, before coming to any firm conclusions. I'd also want to know what the voltages were at the end of the trip and before the 3 day layup to give an accurate comparison.

Secondly, I'd also want to see the voltages with the engine running and with the on-board charger running to confirm that both are working correctly.

It's easy to jump to a wrong conclusion.

One of our MPPT solar controllers has a voltmeter with an error of 0.2V on it, compared with the other controller and a DVM. That is quite a significant error when you are looking at 12.5V or something in that area, and could mean the difference between a working and a faulty system.

Lastly, all voltages should be checked with no standing discharges or loads.

Our on-board chargers and our solar panels keep the batteries at 13.80V, showing as 14.00V on the faulty unit. (We have the interface cable and software from the makers to correct that)

Peter


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## peribro (Sep 6, 2009)

jd_boss_hogg said:


> Does anyone think that the "50%" level doesnt actually mean a true 50% charge, but perhaps it means we are 50% towards the 'danger zone' according to peribro's chart?


If your meter is saying 50% then I would assume it is broadly that. The chart is guidance only and if in doubt, err on the side of caution. The manual for my current motorhome says that 12.3V equates to 50% although the chart (which was previously posted on MHF) and elsewhere that I have seen have shown higher than 50%. I think that 12v or 12.1v are the "danger" levels below which you shouldn't go.


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## Sideways86 (Feb 25, 2009)

listerdiesel said:


> You have to be careful with interpreting voltages.
> 
> First of all, 'gadget' voltmeters are not terribly good, and I'd want to see a voltage on a professional DVM, something like a Fluke, before coming to any firm conclusions. I'd also want to know what the voltages were at the end of the trip and before the 3 day layup to give an accurate comparison.
> 
> ...


I agree with all of the above except that running voltage confirms that alternators chargers and regulators are actually charging

They DO NOT confirm a amp drain, you do need to gather all of the facts and weigh up the complete picture


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## jedjack (Dec 28, 2013)

What is all the Obsession with volt meters ?

All good old battery chargers are fitted with ammeters and when they read zero your battery is charged.


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## Sideways86 (Feb 25, 2009)

jedjack said:


> What is all the Obsession with volt meters ?
> 
> All good old battery chargers are fitted with ammeters and when they read zero your battery is charged.


I couldn't agree more volts are great but if batteries cannot sustain them then you are measuring power of alternators etc in essence

You need to establish the basics as detailed by a few peeps above


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## listerdiesel (Aug 3, 2012)

jedjack said:


> What is all the Obsession with volt meters ?
> 
> All good old battery chargers are fitted with ammeters and when they read zero your battery is charged.


Mainly as ammeters are good for showing what the charger is doing, not the condition of the battery.

Peter


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## Sideways86 (Feb 25, 2009)

listerdiesel said:


> jedjack said:
> 
> 
> > What is all the Obsession with volt meters ?
> ...


That isn't actually right in isolation

Ammeters also show more importantly what the actual installation is doing when there are no charging devices switch on or engines running!!!


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## readyforoff (Dec 28, 2013)

Sideways is correct.........the poster has no means of knowing if the battery condition meter is accurate so needs to check if there is any current draw when standing. Digital ammeter inline as he says but .2A (200ma) will take the batteries out in a couple of weeks.Less if he had 1 x leisure. If the van is left for several weeks and has a drain either trace and rectify it or disconnect when not in use....John


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## jedjack (Dec 28, 2013)

listerdiesel said:


> jedjack said:
> 
> 
> > What is all the Obsession with volt meters ?
> ...


Any regulated charger will do exactly what the battery demands of it which is why it is such a good indicator of battery charge status.


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## listerdiesel (Aug 3, 2012)

(Response re: ammeters and voltmeters, not the post above) 

Sorry, I have to disagree, a voltmeter is far more useful in my experience for diagnostics than an ammeter, but of course in an ideal world you would have both.

Unless you have a digital ammeter, most analogue meters won't show small discharges, especially the moving iron type of meter.

If you go looking for problems, you don't take an ammeter with you (although our Flukes do have amps capability) you take a voltmeter.

It's the way it is for most systems as it isn't easy to disconnect a circuit and insert an ammeter, but you can quite easily check for voltage drop in a cable, useful when you have multiple circuits coming from one battery. On the mV range on a DVM you can sense very small currents and identify really small current flows.

I had an ammeter and voltmeter in my truck servicing days, hardly ever used the ammeter but the analogue voltmeter was always in use.

The other problem with DVM's and their amps ranges is that 10A isn't going to get you far in systems with 100A alternators and 25A chargers.

Peter


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## BrianJP (Sep 17, 2010)

Your batteries are probably ok if you have had no problems. There are so many things that can affect accurate assement nowadays. 
The only true test is to fully charge both batteries then disconnect them and measure their voltages in the ensuing days. Beware though only only a new battery or one in excellent condition will hold the full voltage, around 12.8v , for any length of time.
All other batteries will decay over time but that does not mean they need replacement.


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## readyforoff (Dec 28, 2013)

Good info Peter but I use an ammeter everyday for such problems as the poster has. He doesn't need to be measuring large input currents he needs to be checking for a drain. If he sets a Digital ammeter inline with one of his leisure negatives on the 10A scale and he disconnects the other for the test and he gets a reading of say 0.25A he knows then it's safe to drop the meter to the 2A scale for a more accurate reading 250ma. If he has less than 100ma it's acceptable and he may have one or other of his leisures faulty. My own leisure draws 38ma for the tracker and goes flat in about 15 - 16 weeks. Starter battery is as factory and never goes flat........John


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## Sideways86 (Feb 25, 2009)

readyforoff said:


> Good info Peter but I use an ammeter everyday for such problems as the poster has. He doesn't need to be measuring large input currents he needs to be checking for a drain. If he sets a Digital ammeter inline with one of his leisure negatives on the 10A scale and he disconnects the other for the test and he gets a reading of say 0.25A he knows then it's safe to drop the meter to the 2A scale for a more accurate reading 250ma. If he has less than 100ma it's acceptable and he may have one or other of his leisures faulty. My own leisure draws 38ma for the tracker and goes flat in about 15 - 16 weeks. Starter battery is as factory and never goes flat........John


Couldn't agree more !

Its a simple process, alternators make volts for batteries to store if they are in good health!

If when the alternators are not generating volts i.e. no engine running you need to check for a system drain

Connect ammeter in series set to read milliamps and let system close down to resting position, modern canbus system's shut down in stages you can actually see this happening on the ammeter(not volt meter) by the drain reducing

Once system is stable note drain figure and check if it is acceptable

If it isn't remove one fuse at a time from a circuit until you see drain reduce or disappear and the you know which circuit your problem is in.

Fiat Ducatos have had problems with the factory fitted radio and other things draining too much, hence the newer system of isolation via ignition.

Not really any good if you want to run an alarm system I am afraid.

For the record a .20 to .25 amp drain will take a battery down in around 2 to 3 weeks, trust me I know and got the teeshirt


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## organplayer (Jan 1, 2012)

*Organplayer*

I appreciate all the information from the really knowledgeable folk on here and must confess a lot is way above my understanding, but I understand that cold weather can seriously affect the battery causing an appreciable drop in voltage. Perhaps the cold weather we have been experiencing is the main reason batteries are "playing up" Thanks to all who have provided the info on this matter.


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## readyforoff (Dec 28, 2013)

Hi Organplayer (you ever played naked ?) :wink: Temperature has surprisingly little effect on the state of the battery. What it does do is closes engine tolerances etc making it harder to start. If there are no standing current draws on a charged when parked battery it won't go flat or discharge significantly for several months....John.


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## organplayer (Jan 1, 2012)

*Organplayer*

Hi readyforoff. I did once ttt..try to playyy nnnaked bbbutt I kkkept gg.getttin mee fff flattts mickksed uup wiv mee ssshharrps, and e
eended uppp onn sssliddin orff the ooorgan sstoooll onto de ffflloorr Gud jjobb I wernt playin in church. Hhappiiee new year everyone.


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