Is my Battery Dead?

[johnandrew70]

Hi Guys
I have been over to the Van today and Wired the 13pin plug on the van all working lovely jubbley, i tested the fridge while the engine was running and that works all the lights work but i found the battery was only charging at 11.6 volts, i asked a friend to rev the engine but only brought the battery up to 11.7 volts.
I then disconnected the battery and tested it it was reading 9.4 volts so i know the car was doing something to charge it,
I have as we speak got it on charge and has been on for a couple of hours. if its a good battery what should it read once rested. i have put a multimeter on the battery while its charging but wont lift above 13v at the moment.

John

 

[ProfJohnL]

Hello John,

A battery with a terminal voltage of only 9.5 is severely depleted. Its difficult to judge whether the battery is damaged from the information you currently have given us, but leave it on charge for 36 to 48 hours and then disconnect the charger, leave it to stand for a couple of hours to allow the battery cells to settle, then measure the terminal voltage. If the voltage is less than 12.0V then it strongly points to a damaged battery.

 

[johnandrew70]

Thanks Prof,
It has a little indicator window in the top of the battery, that is showing Red instead of Green, i know from past experiance with Battery's when it shows Black its duff, it says if its red it needs charging so hopefully fingers crossed it will be fine.
If i do need a new battery do i need to use a Leisure battery?? I dont do any touring off mains electricity and its only for the mover really.
I have a Car battery that i bought for the car a while ago then found i didnt need it so i was wondering if i can use that or does it need to be a Leisure??

John

 

[Damian]

It will take at least 36 hours to charge the battery to its proper level on your car charger, then let it rest for a couple of hours and test the voltage , it should be around 12.8v
The car will only charge at a higher rate once the car battery has been charged by th ealternator.

If the battery will not hold charge after charging, then as you only want it for the mover a car battery would be OK for short mover use.

 

[johnandrew70]

Thats great, i will leave it on charge for 36 hours and see what happens if not i will use the car battery at least it saves me a few quid as i couldnt find a 110ah for much below £80.

 

[colin-yorkshire1]

hi John,
very little to add as the information given above is comprehensive enough,
however If I may elaborate a little on Damians answer, I had the same problem has you have last year, exept my battery was deceased,
on pondering a replacement, was told that I had to have a lesiure battery of a least 100amps if I wanted to use a motor mover,
this is incorrect, because I allways use a EHU, (even in the garage while stood) and the car via the alternator charges it while on the move, leisure batteries do not like this situation and are happier being charged /discharged and then charged again. keeping them at a constant charge rate could damage them. however a car battery is designed to be on constant charge, with a large output for short burst (cranking amps) and then recharged, providing the cranking amps is high enough to run the mover during start/stop manouvers it is the best choice if you use a EHU, while on site,
I went for a heavy duty standard car battery it runs the mover for 20mins without problems and seems ideal.
one other point although you may be aware of this a EHU will not fully charge any battery only to about 80% so occasionally it has to be topped up with a smart charger.

 

[johnandrew70]

Hi Colin
thanks for the reply, i have the leisure battery on charge here in the kitchen as we live in a flat and have nowhere else to do it(will switch it off at night) its currently at 13.5v while charging.
The Car battery is a 60ah with a cold cranking of 550 amps. its been in the cupboard for 18months checked the voltage earlier and its at 12.6v.
as i said earlier i only use the battery for moving the van, all the other 12v things are used once hooked up (water pump and lights)

John

 

[colin-yorkshire1]

hi john, sounds like the lesuire battery might be ok once charged leave it to stand a couple of hours then check the voltage.
the car battery you have seems adequate as it is a similar size to mine, so now you have a spare, being stood so long yet giving such a good reading prooves it is a good one, ps dont forget to top up the charge once the lesuire battery is charged,

 

[johnandrew70]

Hi Colin
As i said i switched the battery charger off over night and tasted this morning before recomencing charging, it was reading 12.8v Also the little Hydrometer window in the top has now started to turn green.
Fingers crossed it will be ok although the proper test will be loading it, Has anyone got any idea's on a simple load test???

John

 

[Damian]

A simple load test is to connect the battery up as normal to the van.
Without engaging the mover rollers, put a multimeter to the battery terminals and note the voltage.
Now operate the mover in either forward or reverse and see what the voltage does.
If it drops and recovers to around 12v the battery is fine.
If it drops and stays down, the battery is no use.

 

[johnandrew70]

A simple load test is to connect the battery up as normal to the van.
Without engaging the mover rollers, put a multimeter to the battery terminals and note the voltage.
Now operate the mover in either forward or reverse and see what the voltage does.
If it drops and recovers to around 12v the battery is fine.
If it drops and stays down, the battery is no use.

Thanks Damian i will try that once the battery has finished charging.
The charger i am using is a few years old and has seen better days to be honest so hope it dont screw the battery up.
it ssems to be doing a cracking job at the minute although i am worried as i only put it on charge 3.30 yesterday and have just checked it and its reading 13.8v, considering i am meant to leave it on charge for 36 hours i think its charging it a bit fast.
John

 

[WoodlandsCamper]

am worried as i only put it on charge 3.30 yesterday and have just checked it and its reading 13.8v,

John
The reading of 13.8v is the output voltage of the charger, not what the battery is at. Which is why you have to disconnect the battery and let it settle for a few hours before taking a reading of the battery health.

 

[johnandrew70]

OK guys a quick update, the charger stopped charging a bit earlier, the fully charged LED has come on to say its all done, i have just taken a reading and it says 13.6v i will leave it a bit longer to see if it drops further.

 

[johnandrew70]

Ok so the battery is back in the van all charged.
Checked the voltage before, 12.8, Operated the mover without rollers on wheels whilst checking voltage 12.63v when i stopped it started to climb back up.
I shall be keeping my eye on it but think its looking good to me.
Thanks for all your help, i just dont understand how it lost its charge in such a short time, i have the van charger on everytime we go away, last time was 2 weeks ago for 3 days, maybe the battery was low and the van charger is unable to recover the battery when its low??
I know the charger is ok as with no battery connected the 12v appliances still work in the van using the charger to power them.

John