# Battery losing charge



## richardsnow (Dec 9, 2007)

My Boxer/Compass Avantquard has 2 leisure batteries (both only about 6 months old) wired in parallel and it seems that the batteries gradually are losing charge over a period of a few weeks.

From the charge indicator they get up to about 12.7v and when the engine is running achieve about 13.7v which is similar to when the mains lead is connected.

Nothing seems to be left on when I park up the van and it usually is parked with a good charge in it (I then actually switch off the main switch just inside the habitation door to ensure that everything is off too) but over a period of 3 or 4 weeks the batteries gradually drop to just over 12v

Should this happen and if not where would you suggest that I start looking please? What tests can I do using a multimeter?


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## DABurleigh (May 9, 2005)

Welcome to MHF! rs123123, catchy name ....

It is not unusual and could be due to alarm, etc. To check the drain, disconnect the negative cable from the leisure battery and put your multimeter in current-measuring mode between the negative terminal post of the battery and the negative cable you have just disconnected.

Dave


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## Autoquest (May 16, 2007)

My avantgarde 115 has exactly the same problem... I managed to track one of the culprits down to the radio that I had fitted, the permanent IGN feed was draining 0.3amps which I think equates to 8 amps per 24 hours. Now I'm down to about a month before the battery is below 10V.

I am runnuing an alarm which draws power to light one LED and that's about it.


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## framptoncottrell (Jan 6, 2006)

Remember, all batteries self-discharge to a certain extent - if left on the shelf with nothing connected they will still end up like the dodo. Lead-acid batteries self-discharge more rapidly than most.

When I was a teenager (what a long time ago!) lead acid batteries were supplied to my father's company dry charged, without any acid, to avoid losing charge whilst in store. One of my jobs in the garage was filling them with concentrated sulphuric acid just before a customer called to collect. The Health & Safety Executive would have had fits, had there been one.

And no, I didn't go up chimneys in the rest of my spare time.....

Dr. (musical, not medical) Roy


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## richardsnow (Dec 9, 2007)

DABurleigh said:


> Welcome to MHF! rs123123, catchy name ....
> 
> It is not unusual and could be due to alarm, etc. To check the drain, disconnect the negative cable from the leisure battery and put your multimeter in current-measuring mode between the negative terminal post of the battery and the negative cable you have just disconnected.
> 
> Dave


Should I set the meter to DCA and just experiment between the various settings??


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## JohnsCrossMotorHomes (Jul 21, 2007)

DABurleigh said:


> Welcome to MHF! rs123123, catchy name ....
> 
> It is not unusual and could be due to alarm, etc. To check the drain, disconnect the negative cable from the leisure battery and put your multimeter in current-measuring mode between the negative terminal post of the battery and the negative cable you have just disconnected.
> 
> Dave


Make sure you know the radio code before you do that.

Regards


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## sallytrafic (Jan 17, 2006)

JohnsCrossMotorHomes said:


> DABurleigh said:
> 
> 
> > Welcome to MHF! rs123123, catchy name ....
> ...


Radio powered by Leisure battery? Rare I would have thought.


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## sallytrafic (Jan 17, 2006)

framptoncottrell said:


> Remember, all batteries self-discharge to a certain extent - if left on the shelf with nothing connected they will still end up like the dodo. Lead-acid batteries self-discharge more rapidly than most.
> 
> When I was a teenager (what a long time ago!) lead acid batteries were supplied to my father's company dry charged, without any acid, to avoid losing charge whilst in store. One of my jobs in the garage was filling them with concentrated sulphuric acid just before a customer called to collect. The Health & Safety Executive would have had fits, had there been one.
> 
> ...


Self discharge rule of thumb 5% per month.

Concentrated sulphuric acid would have killed the battery! 1280 SG acid was normal when I used to fill batteries 40+ years ago (although for some reason I'm also getting 1340 in my mind perhaps that is the SG of the concentrated stuff -edit no that about 1.8 )

What I remember most about making up the battery acid is the mantra add acid to water never the other way around.


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## sallytrafic (Jan 17, 2006)

rs123123 said:


> DABurleigh said:
> 
> 
> > Welcome to MHF! rs123123, catchy name ....
> ...


Start at the highest Amp range and work down. To cause the problem you speak of its unlikely to be a drain of more than 100mA or so. If you are measuring a recently charged battery remember that there just may be hydrogen about and your battery disconnection/multimeter connection may be a source of sparks. (its not likely but safe is better than sorry)


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## sallytrafic (Jan 17, 2006)

Autoquest said:


> My avantgarde 115 has exactly the same problem... I managed to track one of the culprits down to the radio that I had fitted, the permanent IGN feed was draining 0.3amps which I think equates to 8 amps per 24 hours. Now I'm down to about a month before the battery is below 10V.
> 
> I am runnuing an alarm which draws power to light one LED and that's about it.


I hate to be picky (no ok I like being picky  ) Autoquest but 0.3A over 24 hours doesn't equal 8A it equals 8Ah (Amperehours sometimes abbreviated to 8Ahr)

For info a single small indicating LED will light at about 3mA but 10mA would be a typical drain.

A battery is very flat at 10V (almost fatally) and repeatedly getting that low ain't good see attached chart.


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## richardsnow (Dec 9, 2007)

Dave[/quote]

Make sure you know the radio code before you do that.

Thanks folks for all the advice - I shall have a go a bit later on. Radio is powered by vehicle battery thank you!


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## Autoquest (May 16, 2007)

Not being picky at all old chap, always keen to learn.. So what does 8Ah equate to with regards to a 110Ah battery?


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## Autoquest (May 16, 2007)

Last charged two weeks ago and now holding 12.7V, guess the radio was the culprit.


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## sallytrafic (Jan 17, 2006)

Autoquest said:


> Not being picky at all old chap, always keen to learn.. So what does 8Ah equate to with regards to a 110Ah battery?


Its 8/110 about 7% of capacity BUT taking the idea that you should never drop below 10% of the capacity the sum should be 8/99 or about 8%. Then you could argue that you shouldn't drop below 50% so it represents 8/55 or about 15% of the capacity. So take your pick 

So putting it another way if you had your 110Ah battery fully charged (and assuming its in top notch condition) after seven days it would be down to 50% and would get down to the 10% level on about the 12th day.

Hope this helps


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