Battery voltage question..

[bob72]

Recently my relatively new battery ran quite flat (something must have been left on in the van). It was showing a voltage of around 7v :scared:

Anyway, I have charged it via a mains charger, done around 450 miles in the van and since had solar panels fitted.
However, now when not in use, the Zig unit shows the battery as being one light above normal, one below high, and the solar regulator is showing a voltage reading of around 12.6 - 12.8v.

Problem is, whenever I use anything more taxing than the LED lights the Zig starts to flicker between Normal and low and the voltage reading on the solar regulator drops to around 12.2v.

Is this normal? I seem to remember when using the lights, heater and water pumps the voltage never dropping below the 'Normal' indicator on the Zig unit (this was before the battery ran very flat).

Is this battery now dead? I am planning a trip to the alps in the new year and really want the battery to hold up!!

 

[solarman]

12.7 volts is fully charged altjough a reading showing this does not mean it's agood battery especially if it drains fast or recharges full quickly,as others have mentioned get it drop tested or run your normal loads on to see how long they can run for,all it needs is for one cell to be dead and the whole battery is uesless

 

[DTDog]

When are you taking the voltage reading from the zig unit. I suspect that the reading of 12.6v + is the battery voltage when being charged by the solar panel during the day?

I agree with the advice to fully charge the battery, leave it overnight and then take it to a battery specialist to have it tested as it does sound as if it is on it's way out.

 

[Firefox]

I would not rely on lights on a zig panel. Use a multi meter or a Zig with a proper voltage meter built in.

Key Voltages 13.5-14.5v charging. 12.7to 12.8v fully charged, 12V 50% charge, 10V or less fully discharged.

If you were down at 7v for some time the battery may have become partly damaged (sulphated). So you will not get the full capacity any more. Fully charge it. Leave it to rest. Connect some loads (A) and see how long (h) it takes to drop to 12V like the others have said. Multiply this Ah x 2 and that gives you the Ah equivalent of the capacity you have left in your battery.

Don't take it much below 12V (50%). Although leisure batteries say "deep cycle," what they actually mean is 40-50% cycle. They never tell you that properly though! Whatever Ah is quoted you can devide that by 2 for practical capacity.

The only batteries you can truly deep cycle are proper 6V traction batteries with really thick plates. They cost an arm and a leg though and I suspect very few of us use them!

 

[bob72]

That is what I find odd the battery with a meter is showing 12.8 and its stable at that (checked over the space of a few hours). I turn the TV on and the voltage almost immediately drops down to around 12.2v - The TV is 12v with fairly low A rating (can't think of top of my head but I maybe 1.5 - 3)

If I turn on something else while the TV is on, the voltage drops further (eg a load of lights - all LED).

I can't be sure how long the battery was down at 7v, I think the van was only left for about two weeks although it may have been a bit longer. I must have left something on

Think I know someone with a battery tester so I'll take it to them over the Xmas hols.

 

[Firefox]

A battery in good condition should be able to maintain 12.5 to 12.7v for some time under sensible loads. Eg lights 20W, TV 20W say 3-4 amps. Would hope to get 10 hours for those at least before the voltage starts dropping towards 12v.

So if you connected a TV and you are down to 12.2v straight away, I wouldn't expect that on a good condition battery. Your TV sounds about right. Mine is 20W which at 12V is 1.7A and say 4 times 5W LED = 20w, another 1.7A. Say 3.4A total

I just put in 2x110A new batteries and they will take those loads for 12+ hours without the needle moving from about 12.6v. My old failing batteries would show an immediate drop in voltage and probably only 5 hours before 12V was reached.

 

[Channelcrosser]

Have a think about an Intelligent Battery Charger - this will really help - you can get them from RoadPro and they have a video on their website about them - go to RoadPro, RoadPro Ltd, Daventry, Truck Parts & Accessories, Motorhome Parts & Accessories, Marine Parts & Accessories, Off Road Parts & Accessories, Canal & River Boat Parts & Accessories, Caravan Parts & Accessories, Car Parts & Accessories, Coach &

Great company with lots of 12 volt equipment for us motor homers.

Good luck

Channelcrosser

 

[bob72]

A battery in good condition should be able to maintain 12.5 to 12.7v for some time under sensible loads. Eg lights 20W, TV 20W say 3-4 amps. Would hope to get 10 hours for those at least before the voltage starts dropping towards 12v.

So if you connected a TV and you are down to 12.2v straight away, I wouldn't expect that on a good condition battery. Your TV sounds about right. Mine is 20W which at 12V is 1.7A and say 4 times 5W LED = 20w, another 1.7A. Say 3.4A total

I just put in 2x110A new batteries and they will take those loads for 12+ hours without the needle moving from about 12.6v. My old failing batteries would show an immediate drop in voltage and probably only 5 hours before 12V was reached.

Yeh that is what I was expecting I just wasn't 100% sure. I'll get this battery back to the supplier next week and pick up two 110Ah batts to replace it.

Regarding the 12.6v reading, I was checking that when there was no charge from the solar panel (it was dark outside). I also took the reading from the battery and not the regulator (although the regulator was showing the same voltage anyway)

Thanks for your help guys :wave: