# Voltage Drops



## 108033 (Nov 1, 2007)

I was concerned that our single 85 amp leisure battery wasn't holding it's charge and, with a big trip coming up, decided to replace it with two new 85s. Having fitted and fully charged them, I thought I would perform a test to ensure that we could watch an evening's TV without a hook-up. Up to now we have always stayed on sites (with hook-ups).
Firstly I tried to make sure that absolutely everything was turned off, even down to unplugging the 12v Sky minibox (so that the standby light wasn't glowing).
- Initially (and with the van still plugged into the mains) the indicator showed the batteries having a healthy 12.7v charge.
- I then unplugged the mains - and the indicator dropped immediately to 12.5v.
- I then turned on the inverter (300w), followed by the 15" LCD which was plugged into it - and the power dropped again - to 12.3v. The TV was just tuned into an analogue channel (no satellite or Freeview).
- I kept it on for 4 hours, checking the battery indicator every half hour. By the end of this period, the indicator had dropped to 11.4v.
- Finally, I turned off the TV and inverter - and the charge immediately went up to 11.9v
I am quite new to all this, and understand little about how leisure batteries work. Is the above scenario - with the slowly dropping charge - what should be expected? What concerns me is that, if I had left it on for another hour or two, the indicator might have dropped so much that the inverter would have stopped working. And of course in 'real life' I would normally have the Sky box and a couple of lights working at the same time.
Am I worrying needlessly? It's just that, with a total of 170 amps (in two brand new batteries) and with so little being used, I would have expected to have had enough power to last for at least a day.
Any comments from the less electronically-challenged would be much appreciated!


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## clodhopper2006 (Aug 13, 2006)

Dificult to tell without doing some testing but it may be that whatever you're reading the voltage from is reading low. When you charge the battery I would expect to see a terminal voltage of 13 or 14 V not 12 ish volts so either your voltmeter is reading low or your charger is not outputing a sufficiently high voltage. I suspect the former because your telly is still working and a battery down below 12v is flat so I think your inverter would be squealing. 
Also not ambient temperature affects battery performance and they suffer in the cold weather.
Best bet is to simulate a night in the van with everything switched on that you would have on normally. Then just see how it copes.

Bob


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## teemyob (Nov 22, 2005)

*Volts*

Hello,

Same problem here, we have 3 x 110ah batteries and 2 x 80w solar panels. The voltage drops rapidly but the solar controller (secca 30) states 100% SOC (State of charge) even when the battery voltage indictates 11v.

Trev.


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## sallytrafic (Jan 17, 2006)

12.7V isn't a healthy state of charge, if as you say, the mains was still connected and thus the charger still connected. I would expect about 14V so I doubt that the charger was on.

When you first take the charger off the first thing to go is the 'surface charge' its ok for a battery to drop 0.2V or more with nothing being taken out until th ebattery over the first 30 mins drops back to its resting value..

A multimeter check at the battery terminals is more reliable than inbuilt indicators as you can be sure exactly what you are measuring.

I've attached a table. In UK with lower temperatures the battery should be 0.1 to 0.2 higher than that shown for the same state of charge.


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## 108033 (Nov 1, 2007)

Thanks for the replies, which would seem to indicate that something is wrong.
The thing that i'm getting the reading from is the control panel above the habitation door, which i'm pretty sure is the original Autotrail fitting. As for the charger, it is definitely 'working', in the sense that the light and fan come on when I switch on the unit. Of course I suppose that, just because something is 'on' doesn't mean that it's functioning properly.
We've only got a matter of days now before going off on a six-month trip and, from past experience, getting an appointment with our dealer (Chelston) at less than a month's notice is unlikely...


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## Guest (Feb 26, 2008)

The most suspect thing looks to be your voltmeter.

What type is your meter ?

A new Duracell Alkaline measure 1.6 off load.

Line a few up and measure end to end to check your meter.

A tenner, tops, will buy a meter that will do the job.


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## geraldandannie (Jun 4, 2006)

philwaring said:


> The thing that i'm getting the reading from is the control panel above the habitation door, which i'm pretty sure is the original Autotrail fitting.


As Frank says, try using a digital voltmeter directly on the battery terminals to find out what's _really_ happening. It's quite possible that the voltemeter you're looking at is measuring the voltage at the control panel, and depending on the size of power wire from the battery to the panel, may be seeing a voltage drop between them.

Voltage will drop as a product of current and resistance (V = I X R). The more current you're drawing through a cable, or the lower the resistance of that cable (i.e. the thinner it is), means more voltage dropped between the two ends (i.e. the battery and the panel).

It's still my guess that the panel meter isn;t reading _actual_ voltage available to the van accessories.

I always carry a small (£10) digital multimeter around with me in the van.

Gerald


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## johng1974 (Jan 17, 2007)

Gerald I have visions of you carrying the voltmeter everywhere in the van, even when you clean you teeth etc  

digital voltage on my charged 110ah was 13.7 ..

on another unused battery I have it was 12.5... but when connected to a charger, interesting to watch the voltage increase step by step.. 1/100 of a volt every 5 seconds, or on fast charge every 3 seconds..

John


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## 108033 (Nov 1, 2007)

bhewart said:


> The most suspect thing looks to be your voltmeter.
> 
> What type is your meter ?
> 
> ...


The panel giving the readings is branded 'Autotrail', although the word 'Sargent' is printed in the corner - the manufacturer perhaps?

I've got a Halfords battery charger. Unfortunately it doesn't have anything with a reading - just a green light (fully charged) and an amber light (charging). Would that be of any use? If not, where could I buy a voltmeter quickly? Halfords? Or a specialist electrical store?


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## johng1974 (Jan 17, 2007)

Phil definately Halfords or any electrical store..

as said, about £10

John


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## geraldandannie (Jun 4, 2006)

[quote="philwaringIf not, where could I buy a voltmeter quickly? Halfords?[/quote]

Maplin is your best bet. Looking at the South West of the country, :: these :: are the stores in your area.

Or, failing that, I think I bought mine from a well-stocked caravan shop.

Gerald


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## geraldandannie (Jun 4, 2006)

Halfords do :: this one ::

Gerald


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## 108033 (Nov 1, 2007)

I'm certainly hoping that the control panel is the issue, and that the charge is actually OK. So I'm off to Halfords.
When I get the meter, do I measure between the positive terminal of one battery to the negative terminal of the second? Sorry if this seems a really obvious question - but I really am technically challenged!


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## seanoo (Mar 31, 2007)

hi all, on my scout there is a big difference between the auto trail panel and using a voltmeter across the battery terminals. at the moment i have 10 amps going in off my solar panels- autotrail panel says 12.8v and voltmeter says 14.3v . in the evening when not charging my resting voltage is normally 12.9- 13.0 volts (at the battery terminals)and auto trail panel says 12.3- 12.4 respectively. i agree with everyone else the voltmeter at the terminals is the only way to measure your correct voltage as the panel is inaccurate. measure betweem positive on one and negative on the other, hope this helps seanoo


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## olley (May 1, 2005)

geraldandannie said:


> or the lower the resistance of that cable (i.e. the thinner it is), means more voltage dropped between the two ends (i.e. the battery and the panel).
> 
> It's still my guess that the panel meter isn;t reading _actual_ voltage available to the van accessories.
> 
> ...


Shouldn't that be higher Gerald? Senior moment perhaps. :lol: :lol:


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## geraldandannie (Jun 4, 2006)

olley said:


> Shouldn't that be higher Gerald? Senior moment perhaps. :lol: :lol:


*cough* - well it would be, if I was _senior_ :evil:

Well done for spotting today's deliberate mistake. Your prize is in the post :wink:

Gerald


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## Guest (Feb 26, 2008)

>> If not, where could I buy a voltmeter quickly?

Maplin is the first name that comes to mind.

Maplin

Places like Halfords tend to put a premium price on things but you now have a guide price.


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## oilslick (Oct 3, 2007)

*Charging on our Apache*

We had a problem with the charging on our Apache. There was hardly any output from the charger. The dealer (Chelstons) couldnt see the problem, but as soon as I showed them the voltage at the battery with the charger on, and then with a couple of lights and the telly on, they soon realised it was doing virtually nothing. A new charger cured the problem and the charge was there even with all the lights, heater fan etc on.

It is obvious to me, running round with my voltmeter all the time, is that the wiring on the Autotrail just isnt really up to the job. They have cut back on cost, and the voltage drops are quite high around the camper. This is one reason why the voltmeter on the panel above the door drops down so much with anything on. Its not the battery that it implies has dropped, its the voltage drop in the wires!! as soon as you turn things off the voltage comes back up.

I also Dont think much of the "Seargant" PSU, I am on my third one now and only 8000 miles (over cheap spec again?). If this one goes down then I shall be buying my own components and making a decent charger.


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## 103279 (Mar 5, 2007)

To add to the information already posted.
To accurately check a battery’s terminal voltage:

1)	Turn off everything including the charger; better still disconnect the Positive terminal from the battery to isolate it.
2)	Leave for at least half an hour for the battery to stabilise.
3)	Measure the voltage directly across the battery terminals.


A common misconception is that cheap digital multi-meters are accurate; they are a lot better than they used to be but I’ve calibrated some that were reading 1.1V low on the 0 – 20V range! I’m fortunate to own a ‘Standard cell’ to check this. I prefer to use my old AVOMk7 analogue meter – I’m just old fashioned.

Given the general low quality of some M/H wiring and some of the components used in the panels I suggest using the control panel meter or LED/LCD display as a rough guide.

Something else that may be of interest is that when the vehicle engine is running and the leisure battery is being charged via the alternator the charge voltage across the battery should be 14.4V but is frequently as low as 13.8V because of voltage drop across the split charging diodes. I’ve discovered that some ‘hook up’ chargers only put out about 13.8V, partly to prevent possible damage to appliances but also to reduce gassing – no not that type again! – Hydrogen that is given off during the charging process.


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## 108033 (Nov 1, 2007)

I've got my new voltmeter! I'm not sure that the results of testing the batteries prove too much though.
Having had the charger on for about four hours this morning, immediately after turning it off the control panel read 12.5v. The voltmeter accross the batteries gave a reading of 12.48v - so effectively the same. When I went back to the control panel however, the reading there had gone down to 12.3v. At the batteries though, the voltmeter reading was still 12.48v.
My plans (unless anyone has a better sugestion) is to put it back on charge again until early evening, then take more readings at both the panel and at the batteries. Then I will unplug the van, and set it for an evening's wild camping (on the driveway!) - with Sky, the TV, the inverter plus a couple of lights working. After about four hours (and assuming everything is still running) I will then check the voltage again - both at the control panel and at the batteries.
But the fact that the panel and the voltmeter have just given me the same reading is starting to make me think that - like Oilslick - I may have a problem with the charger.


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## Chascass (May 10, 2007)

What you should do now is check what the voltage is at the battery's, with the charger switched on, if the voltage is not reading around the 14 v region, ether the battery charger is not working or a fuse between the charger and battery's has fused.

Charlie


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## Guest (Feb 26, 2008)

>> do I measure between the positive terminal of one battery to the negative terminal of the second?

Make sure you are set for Volts DC.

Then just play around - you'll soon get the hang of it.

Though all -ve terminals should be the same and a good place to hang the black probe. Then stab around with the red one.


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## 108033 (Nov 1, 2007)

Chascass said:


> What you should do now is check what the voltage is at the battery's, with the charger switched on, if the voltage is not reading around the 14 v region, ether the battery charger is not working or a fuse between the charger and battery's has fused.
> 
> Charlie


During charging the control panel says 13.4v but the voltmeter at the batteries says 13.13v. Turn the charger off for a minute and the readings go down to 12.7v and 12.86v respectively. I don't think I've ever seen the control panel higher than 13.5v, but because it appends the word (Good) to any reading above 12v I'd never realised that there was a problem. As I said earlier, we've only ever camped with hook-ups.

Again excuse my ignorance in these matters, but if a fuse had gone between the charger and the batteries wouldn't that mean that no charge at all would get through i.e. it would stay at the same reading, rather than increase (albeit slowly).

Another question has just come into my mind: if the charger is not performing properly, would the charging which occurs as a result of driving also be affected? Or does that get to the battery via a different route, avoiding the charger?


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## sallytrafic (Jan 17, 2006)

philwaring said:


> Chascass said:
> 
> 
> > What you should do now is check what the voltage is at the battery's, with the charger switched on, if the voltage is not reading around the 14 v region, ether the battery charger is not working or a fuse between the charger and battery's has fused.
> ...


A good battery charger has 3 or 4 stages.

Near the end of charging the charger should for a short time have the battery up at 14.4V or slightly more this is to ensure the negative plate chemistry is taken to completion. There after it will revert to a maintenance charge until the battery voltage drops far enough to warrant and increased charge.

During the initial charge phase the voltage is controlled so as not to charge at too fast a rate. There is a lot of more complicated stuff happening as well


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## pete4x4 (Dec 20, 2006)

13.14 suggest the batteries are charging but now you have two it will take twice as long to charge, a fully charged battery at 20 degrees C would read 13.8V in a perfect world so I would expect you to be reading 13.8V for one in 6-7 hours but you have two so that time will be longer and it also depends on how much charging current is being put out by the charger.
I would hope that with nothing else on the batteries should be above 13.8 volts within 12 hours. 
Nothing suggests a fuse been blown and yes it is charged differently when driving and as the alternator can deliver higher currents than your charger they should charge quicker.


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## 108033 (Nov 1, 2007)

pete4x4 said:


> I would hope that with nothing else on the batteries should be above 13.8 volts within 12 hours.


Perhaps then I should leave them charging overnight, rather than 'wild camp' this evening.


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## pete4x4 (Dec 20, 2006)

Wouldn't hurt, you'd know in the morning then whether your charger can charge your batteries.


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## Sargent (Feb 1, 2008)

Hi Phil, I believe that there may be a problem, but if you could advise how the battery voltage performs after a nights charge, but either way if you would like to talk to one of our technical support team on 01482 678981 or if you want to send me a PM with your contact details and i will get one of the team to give you a call.
I can confirm that since 2005 all of our units have had multistage charging systems, as Sallytrafic has indicated.

Regards

Ian Sargent


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## Guest (Feb 26, 2008)

pete4x4 said:


> Wouldn't hurt, you'd know in the morning then whether your charger can charge your batteries.


And in the morning measure straight away, then turn a light or two on and measure again under a light ( no pun ! ) load, I'd expect the battery to hold it's voltage if the charger is doing it's job. If the voltages dips a lot the charger is only putting out a low charge.

This is good, you've now got the tools and learning how to use them.


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## 108033 (Nov 1, 2007)

*The Results are In - and It's Not Looking Good*

After around 20 hours on charge in the last 24, the results are:

Charger On
Voltage at Panel: 13.5v
Voltage at Batteries: 13.48v

Charger Off / No Load
Voltage at Panel: 13.0v
Voltage at Batteries: 13.20v

Charger Off / Two Lights On
Voltage at Panel: 12.7v
Voltage at Batteries: 13.01v

So, judging from the opinions in earlier posts, there is a problem with the charger. I will be taking up Mr Sargent's offer of a phone call to his support team. I just hope he or Chelston will be able to do something before we head off on Saturday.

Many thanks again to everyone who - as always in this forum - have spent so much time helping a newbie.


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## 108033 (Nov 1, 2007)

Even better news - Chelston can replace the charger tomorrow afternoon!


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## geraldandannie (Jun 4, 2006)

That's great news, Phil  

And you've got a multimeter to carry around with you anyway - welcome to the club :wink:

Gerald


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## 107558 (Oct 10, 2007)

*Re: Volts*



teemyob said:


> Hello,
> 
> Same problem here, we have 3 x 110ah batteries and 2 x 80w solar panels. The voltage drops rapidly but the solar controller (secca 30) states 100% SOC (State of charge) even when the battery voltage indictates 11v.
> 
> Trev.


On the Steca the SOC only works if the load for the whole Van is connected to the load terminals (not recommeded). You need to change the display from SOC to VOL.


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## H1-GBV (Feb 28, 2006)

I'm jumping on the back of this thread and hoping someone can help me with, possibly, similar problems.

Measuring the voltage at the terminals gives me a reading of about 12.8V With no load, the display panel shows the same.

However, as I increase the load, the panel indicator drops such that with 6 lamps on it is around 11V and the "low voltage" beeper goes. At the terminals, it is still about 12.2V.

This sounds to me like a high resistance somewhere in the circuit, but where do I start to look?

Some technical stuff: this is a 2002 Rapido with split charger/coupler, so the base battery shares the load until 12.4V. The panel sometimes reads as high as 13.6V, but this seems fairly random. We are "permanently" connected outside the house, but when touring we rarely seem to get above 12.8V. I fitted a new (but cheap) 110Ah battery last year, as recommended here when I reported problems with my blown air system. Could there be a problem with the base battery??

Thanks for any ideas.

Gordon


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## Guest (Mar 1, 2008)

H1-GBV said:


> This sounds to me like a high resistance somewhere in the circuit, but where do I start to look?
> Gordon


Battery terminal are always a prime suspect, are you measuring the actual battery terminals or the wires connected to the battery terminals. Your resistence might be right there.

Otherwise it's try and track the main power cable and see where the voltage drops. Any connection is suspect and fuses are a lowish grade connection.


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