charging 12v

Jul 10, 2006
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hi all i assumed that the battery would charge up whilst towing (after going flat over winter).this the 1st time we've used the 12v system normally we hook up.when we arrived at the pitch the battery had no power are we missing something obvious or do we have a problem.also what position should the switch be in when towing car / van help andy
 

Damian

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Mar 14, 2005
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Lisa, depends what van you have as to what position the switch needs to be in when towing to charge the battery from the car.

However, if your battery has gone flat over the winter lay up, then there will not be sufficient charge from the car to charge it up properly.

It is possible that by leaving the battery in the van , and discharged for a long period that you have done irreversible damage to it, and it will never charge again.

Batteries should be removed from the van if overwintering without use, and be kept fully charged at home, in a cool place, but not subjected to frost.

Your best option now is to try a ful charge at home with a multi level charger, as are available in most places now, and see if you can getit to charge up.
 
Jun 21, 2006
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Lisa,

I'm afraid that if the battery has been left flat or anywhere close to half charged or less over the winter it is probably dead. Below 75% charge the plates in the battery will start to sulphate causing it to loose it's ability to accept and store charge. There are some fancy chemicals and pulse chargers around that are suposed to recover batteries in such a state but they may or may not work depending on the articles you read.

Simple answer is, if it won't charge on you vans built in charger or a stand alone charger then get a new battery and remember to disconnect it over the next winter layup or at least make sure it has a top up charge every month or so.

Giles
 
Jun 23, 2006
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Over many years I have lost at least 3 batteries over the winter due to letting them go flat having put of checking they were charged. Have never saved one yet!

My van is stored outside so we have a Solar panel on the roof that keeps it healthy these days.
 
Jul 11, 2006
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One problem of batteries that have gone flat is the control of the recharge. Sophistcated chargers, when faced with a totally dead battery, will apply a low rate charge for some time if necessary until the plate voltage comes up above about 10.8V whence normal charging commences.

An AA man gave be a flat battery some years ago and told me to charge it at low current for a long time. Being an Electronics Engineer I have access to a power supply unit which is both variable voltage and variable current. I connected it to the battery, set the current at about 200mA, and left it for a couple of weeks and it was fine. When my wife's car battery died I replaced it with my freebie and it was still on the car and working perfectly when we got rid of it four years later!

If your battery is dead don't give up on it. Try connecting your charger but with a light bulb (domestic, car headlight, whatever) in series and see if you can recover it. Better than having to buy new!
 

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