# Basic Battery questions



## MinusNothing (Jul 27, 2009)

Hi all,

Newbie here again. Autosleeper Clubman 1997.

I initially thought my battery setup was okay, having no problems during light use - weekend wild camping for example.
However, after leaving my camper in storage for two weeks before Xmas the cab battery didn't have enough charge to start the van. The 12v leisure battery also appeared to be dead using my test panel (Red LED sigifying dead). Jump starting and a little trip out solved this temporarily.

A week or so later the same thing happened, so I bought a multimeter to perform test.
Another week later I went to check the van, presuming the battery would be dead, but tests with the multimeter showed both batteries to be okay (charged to around 12.5v each).

I know cold affects battery performance - the two times this happened it was extremely cold. I also think the alarm may be draining the battery, but surely 2 weeks should be okay?

Cab battery is 85mAh, Leisure is 110mAh.

I therefore have a few Q's regarding batteries and 12v in general:-
1 - How can I tell if my batteries are now faulty or have been discharged too much and damaged?
2 - Using the multimeter can I tell how much is being drained from my battery - how do I do this?
3 - Using the multimeter can I tell if the batteries are being charged at a given point in time?

Any other tips appreciated.

Thanks a million.


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## weldted (May 1, 2005)

*batteries*

Hi with the engine running your batteries should read 13.8 volts plus,

12.5 is not a fully charged battery you should be nearer 12.8

there should be a second hole where the leads for your multimeter goes one should be marked common for the black the red goes into the other one that may have something like ten amps max. turn everything off disconnect the negative lead from the battery, put the red probe from the multi meter onto the negative terminal of the battery and the black lead to a known earth or onto the battery lead. you have just connected. if you have a clock in the system you may get a very small reading from the meter other than that it should be zero. another test check the voltages of both batteries with the engine off, then turn all the lights on in the camper side of the van wait five mins with the lights still on the leisure battery voltage should have dropped but not the engine battery.

if they both drop you have a permanent link between the two and one will pull the other down. what type of control panel do you have and what age is the van?


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## trevorf (May 16, 2005)

A multimeter will tell you if the battery is charging as per welteds explanation but for a true indication of battery condition you really need a load tester like this one in the link below.

load tester

Trevor


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## eddied (May 9, 2005)

*Electrickery and batteries*

:roll: Ciao, being a complete ignoramus where all this is concerned, I consider myself very lucky that over 4 years, with 2 leisure batteries, I've not had any problems on my 2.8 Ducato JTD. If I did have an unpleasant surprise, I would be stuck.
What I do is once a week/10 days run my Kipor generator for an hour, and check the voltage going into the engine battery with a multimeter. This seems to work and esnure that I always have a healthy engine battery whatever the weather. Must admit that really cold here is only as low as 5 Celsius.
This also gives a boost to the 2 X 85 AMP. leisure batteries of course, and I never seem to have a problem with them, although they are 4 years old.
If I'm not been anywhere, I will occasionally run the engine instead.
HTH,
saluti,
eddied


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## NicknClair (May 18, 2006)

Good way to test leisure is to fully charge over a 12 hour cycle (charging volts between 13.8 and 14.2). Disconnect leisure battery and make note of volts after 15 mins (this is to insure that there is no outside influence of discharge). Then take another reading (with the battery still disconnected) after 12 hours. This shouldn't drop below 12.7 volts. 

Engine battery is tested slightly differently, as it is the cold cranking amps (sudden omph that is need as well as holding it's charge) that is important on an engine, so going to a garage for a "drop test" is the best way to go. Never perform a drop test on a leisure battery, or it's bye bye in most cases. 
Good luck.


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## mickdee (Apr 17, 2010)

Hi NicknClaire

im also having battery problems and wondering if its my batteries (2 * 110 Ah), im interested in doing the test you suggested in the previous post.
can you tell me if there is an acceptable voltage drop (over the 12 hrs) or should it be exactly the saem voltage

thanks
mick


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## rayc (Jun 3, 2008)

mickdee said:


> Hi NicknClaire
> 
> im also having battery problems and wondering if its my batteries (2 * 110 Ah), im interested in doing the test you suggested in the previous post.
> can you tell me if there is an acceptable voltage drop (over the 12 hrs) or should it be exactly the saem voltage
> ...


They have not posted since early this year so they may not be actively monitoring MHF.

I believe they are saying that it is not important what it is at the start but must be above 12.7v after the 12 hour period.


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## Wizzo (Dec 3, 2007)

If the battery is getting on a bit it is unlikely to hold 12.7v, probably around 12.5 or 12.6. I would not be too concerned if that were the case.

JohnW


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## listerdiesel (Aug 3, 2012)

Even an older battery will show 12.6-12.7 volts on open circuit after a charge, but to be honest, the battery needs to be doing some work for you to be able to tell how good or bad it is, which implies something like a 10-15A load being put across it for a short period and the voltage monitored while the load is on.

We make a small 30V battery/charger for sub-stations, and they have a resistive load, a load switch and a voltmeter with a marked 'safe' area so the operator can apply the load for 10 seconds and see how the battery responds.

If you had a 3-way fridge with a 12V heater that you could connect across the battery, that would be about 10A, it varies with model, but it is a convenient item that might be available.

A good battery should support that for an hour and still be above 12.3V - 12.4V, could be lower or higher, it all depends on your battery capacity and the load current.

If the volts start to collapse after half an hour, chuck the battery away.

Peter


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