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penny2011

Flat battery

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Hi guys we just had to put our caravan in outside storage after 5yrs and has always been plugged into mains and always had a fully charged battery,we have a 100w solar panel fitted on roof so was hoping this was going to keep battery charged but went there last week to find battery flat ,I turned all electrics off now should I have left the charger on or has solar panel got its own charger,but what ever have now got to get another battery as this wont charge.

 

 

 

 

 

 

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Penny, it all depends how your vans been wired up … you’ll need to check that out and perhaps get it rewired so that you don’t need the main switch on.  But the van’s charger doesn’t really have anything to do with the solar panel.

 

How long has the van been at storage before the battery went flat, because I leave mine all winter without a charge. How old is the battery?

 

John

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Quite possibly the battery has simply reached the end of its days, nothing to do with the panel or the charger.

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I have a 100w solar panel and I have the charger button turned off when it’s in storage and the solar keeps the battery charged. 

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If your charger is a smart one it is unlikely to charge a completely flat battery but an older none smart one may work to get the voltage up to about 10 volts when the smart charger can then be used. I have done this with our caravan battery when it was down to about 8 volts so know it can work.

 

2 things had flattened the battery, the heater fan had been set on Auto which kept the fan running at a very low speed which I could not hear. Now I make sure the 12 volt master switch is off (I thought it was) and the heater fan switch is off and not on auto. Also the alarm battery had failed so the main battery was constantly trying to charge it - sorted by removing the alarm battery until a new one was bought and removing the 12 volt fuse for the alarm. In storage the alarm battery also needs to be kept charged up so ours is removed (insurance does not include the alarm).

Edited by Paul1957

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12 hours ago, Paul1957 said:

If your charger is a smart one it is unlikely to charge a completely flat battery but an older none smart one may work to get the voltage up to about 10 volts when the smart charger can then be used. I have done this with our caravan battery when it was down to about 8 volts so know it can work.

 

2 things had flattened the battery, the heater fan had been set on Auto which kept the fan running at a very low speed which I could not hear. Now I make sure the 12 volt master switch is off (I thought it was) and the heater fan switch is off and not on auto. Also the alarm battery had failed so the main battery was constantly trying to charge it - sorted by removing the alarm battery until a new one was bought and removing the 12 volt fuse for the alarm. In storage the alarm battery also needs to be kept charged up so ours is removed (insurance does not include the alarm).

A caution... Paul1957 is correct in that a trickle charger may bring your battery back, but make sure you put it on its lowest setting (typically 1A IIRC)... None of the recovery can be done quickly, I had 3x110AH AGMs on the boat years back, and they were recovered by using a trickle charger, but it took 10 days at an amp so as not to let the batteries overheat...

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Another item that can drain your battery is the radio if it hasn't been isolated. If it has a removable front, taking it off when the van is in storage is the safest bet.

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1 hour ago, MalH said:

Another item that can drain your battery is the radio if it hasn't been isolated. If it has a removable front, taking it off when the van is in storage is the safest bet.


Also, very often the TV aerial booster doesn’t turn off with the master switch, and is usually hidden away in a cupboard so you don’t spot it’s blue light - my mates battery was flattened this way.

 

John

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I have been surprised on  how batteries can recover. The main problem is my charger will not charge a heavy sulphated battery, the auto charger auto turns off when disconnected, many do this, so with heavy sulphated battery it sees it as no battery being connected.

 

So I had to cheat and put two batteries in parallel, and charge them as a pair, one fully charged the other completely discharged and heavy sulphated, it had been left completely discharged for around 6 months, the charger was a Lidi smart charger it would normally charge at 3.8 amp, but once the charge rate had dropped to 0.8 amp it would not return auto to either the 3A or 3.8A rate, so the charger was connected to a energy monitor so I could on the PC see a graph of power into charger, which is a reflection of power out, so I could see if battery taking power.

 

So two weeks nothing, half way through 3rd week charge rate jumped from 0.1A to 0.8A and when I looked the voltage had dropped, it was near enough steady for first two weeks at 12.9 volt actually it would drop to 12.8 then rate to auto change to 0.8A then it would go to 14.4 volt in a minute or so then back to 12.9 volt so 99% of time it sat at 12.9 volt.

 

When the rate auto increased it stayed at 0.8A for around Ah/0.7 hours, i.e. just a likely more than Ah divided by charge rate, and then dropped to 0.1 amp again, the surprise was no slow lead up, it was as if after 2.5 weeks some one had flicked a switch, it was repeated a few times and the same results, sat for a long time with no sign of charging, then as if switch flicked it fully charged.

 

It was done first with two batteries from a chair lift, then repeated with battery off caravan, until the smart charger I would have not walked away and left a battery on charge for that long, but as long as the good slave battery is smaller or same size of battery being charged no problem, when it starts to take a charge if there is a shorted cell then it will take a massive charge rate with a simple voltage regulated battery charger, so the caravans built in battery charger could charge at 35 amp until battery boiled dry and it could explode, so it needs charging with a low rate battery charger so if there is a shorted cell, the max charge is the transfer from good battery plus charger charge rate, the doner battery  will soon discharge and so it will not boil the battery dry.

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I suspect that the 12v switch has been left in the On position although all the other electrics are switched off

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