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Battery Charger Help Please!


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Hi

Our onboard charger seems to be killing our leisure batteries.
We have 91 Coachman and are having problems with the charging system. Basically thinking it was a dead battery I connected a spare that had been fully charged away from the van and all seemed OK. Today, 2 days later I have been in the van and the battery is dead, only reads 6. 5volts.

The reading on the charger terminals at the battery is 1. 2volts which is obviously low but all 12volt lights work fine as does water pump and reads 11. 9 volts on the ceiling light and awning light.

Any ideas why this would happen, is the charger faulty; why 12v at lights and only 1. 2v to battery?

 

 

I have reconnected the battery but neither are strong enough to switch lights on. The reading is 6. 4 volts with mains off and 7. 6 with mains on, so the 1. 2 volts on the charger terminals seems correct.

I have also tried both batteries on an external charger and the charger reading alternates between fully charged and dead every second, so it seems to me that both batteries have somehow been killed by the van charger.

All lights etc still work and I get a reading of 11. 9 on the awning light.

Why only 1. 2 at the battery charger terminals?????
Cheers

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With mains connected and charger ON, the voltage at the battery terminals should read around 13. 8v DC.

 

With the readings you have given, your charger is faulty and the batteries are well and truly flat and will need a serious recharge to try and revive them, if they in fact do revive.

 

A normal smart charger probably will not start charging as they only kick in at 10v DC so to get them going you will need a very basic charger which does not measure battery voltage before starting to charge.

 

The other 12v iitems which do work are drawing their power from a different part of the PSU.

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The other 12v iitems which do work are drawing their power from a different part of the PSU.

Really? Why would a caravan PSU have more than one 'part'? Not saying you're wrong, just that I can't see any logic in it.

 

The voltages quoted by the OP don't make sense. I think he needs someone more knowledgeable to take a look.

 

Tony

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Really? Why would a caravan PSU have more than one 'part'? Not saying you're wrong, just that I can't see any logic in it.

 

The voltages quoted by the OP don't make sense. I think he needs someone more knowledgeable to take a look.

 

Tony

The charger unit has two take offs, one for battery, one for 12v supply, so if the charge side fails, as has done in this case, the 12v still works from the secondary takeoff, so you still have power when connected to the mains supply.

Edited by Brecon
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With 12. 6 volts at the charger, it is not charging the battery.

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Thanks again for the reply.

 

OK, so should I not expect to see 12. 6v at the battery also? Why 1. 2v?

 

Could it be a problem with the control board as well?

 

Also why would 2 batteries be ruined by connecting to this output?

 

Sorry for so many questions - our next trip is all EHU so will get buy without battery but would like have a good backup plan.

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Are the switches in the photo set as you have been using them, shouldn't the left hand switch be set to "van"?

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The charger unit has two take offs, one for battery, one for 12v supply, so if the charge side fails, as has done in this case, the 12v still works from the secondary takeoff. ..

How?

 

The battery is connected to the 12V circuits. Ergo if the charger had two outputs they would be connected together.

 

Tony

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Thanks again for the replies.

 

regarding the switches, yes that was just the position in the photo, is tried it in various positions but yes it should be in the "van" position.

 

Tony - That fuse in the pic is one I put in to test - made no difference though.

Thanks again.

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If you disconnect the battery do the 12V circuits work? If they do then the charger is okay, but the battery is kaput.

 

Tony


Or. .. the wiring to the battery is Kaput.

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yes - the lights still work without battery.

 

I have just been out and checked al connections again, including the rear of the control/switch panel and I now get 12. 6 on the charger terminals (battery end and battery disconnected).

 

Problem now is. ...... was the fault causing the discharge of the batteries or are they just knackered? And will the van charger be capable of recovering the bats?

Just reconnected and reading at the battery goes from 6. 5v to 8. 2v (ish) when turning on the charger.

 

New battery????

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Yes, you need a new battery. Before I answer your other questions, what are you measuring the voltage with? Do you know how accurate it is? 12. 6V is low - about 1V below what it should be for charging a battery - but I don't know how accurate your measurement is.

 

I will say that a constant 12. 6V fed to the battery would definitely not kill the battery, but it wouldn't charge it either.

 

Tony

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Evening, thanks again for the replies.

Looks like a new battery at the weekend then or may just run without battery. ..... we only have plans for EHU this year anyway.

 

I am measuring with a digital multi meter, (can't remember the manafacturer), i will borrow a friends tomorrow and compare the readings, I think you maybe on to something though as I have just checked the voltage with the same meter on another battery charger and that read 12. 6 too, so two chargers both with low outputs seems a coincidense. ........

 

Regarding the age of the batteries, one was new last year 110AH and the other is a couple of years older 85AH i think.

 

Thanks again for the advise.

 

Jim

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