Leisure battery question

[NigelNovice]

I have 2 100ah lead leisure batteries, I added 1 shortly after getting MH, I fitted then in parallel and I also wired the inverter direct (switched) but not used in anger yet, we went out for a night on a campsite with grandson without EHU, we lost 12v about 10pm with leisure battery voltage down to 10v, I have a solar panel (unknown wattage) and I know it wont charge at night but I thought 200ah would have lasted a bit longer than that.
In the battery compartment there is a second harness connection for the second battery to the Sargent EC325, my question is would it benefit me to use said connection and undo the parallel set up and from what I have read I can choose which battery to use/charge or do I leave as parallel?

 

[Itsmcb]

If you have recently added a second battery it seems likely that the original one is suspect and is dragging the new one down. Unless of course you are running multiple items with your inverter and draining both. I would disconnect both and charge them individually and see if one loses charge with nothing connected.

 

[pappajohn]

If the voltage dropped that low so soon I would be replacing them asap.
Were you using the inverter for anything that evening ?

 

[NigelNovice]

If you have recently added a second battery it seems likely that the original one is suspect and is dragging the new one down. Unless of course you are running multiple items with your inverter and draining both. I would disconnect both and charge them individually and see if one loses charge with nothing connected.

I did suspect the older one draining but I did disconnect when I got home and measure voltage on both and they were both reading within a couple of points of each other 12.5 and 12.3, I also checked the Solar panel on a not to sunny Saturday was putting in 2.4 amps and about 16v

 

[NigelNovice]

If the voltage dropped that low so soon I would be replacing them asap.
Were you using the inverter for anything that evening ?

Grandson had telly on 12v not used Inverter yet, I dont know the age of first Leisure battery either, only bought second one in April

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[Itsmcb]

I did suspect the older one draining but I did disconnect when I got home and measure voltage on both and they were both reading within a couple of points of each other 12.5 and 12.3, I also checked the Solar panel on a not to sunny Saturday was putting in 2.4 amps and about 16v

Check them both again after being disconnected for a couple of days. If one is faulty it should lose charge.
Do you know what condition the batteries were in when you arrived on site?

 

[Itsmcb]

Grandson had telly on 12v not used Inverter yet, I dont know the age of first Leisure battery either, only bought second one in April

Must be a faulty battery. I have two 110amp batteries and I can watch TV, charge phones, use the microwave and run an electric blanket through an inverter all night and still only use about half of the 110 available amps.

 

[NigelNovice]

Check them both again after being disconnected for a couple of days. If one is faulty it should lose charge.
Do you know what condition the batteries were in when you arrived on site?

As the are in parallel it can only read it a one and was 12.8

 

[Itsmcb]

As the are in parallel it can only read it a one and was 12.8

12.8 is fully charged so it's highly doubtful you can have used enough power to drain both batteries. Separate and check

 

[funflair]

12.8 is fully charged so it's highly doubtful you can have used enough power to drain both batteries. Separate and check

The battery/batteries could hold a charge but have very little actual capacity I believe.

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[autorouter]

There are several ways a battery can fail, and one way is that is loses capacity. It charges up and goes into float charging as normal, but when you apply a load to it, it behaves like a battery with capacity of 50Ah or less.

You can test this by charging it to 100% full, then applying a known load and see how long it lasts. For a 100Ah battery, a 5A load should last 100/5 = 20 hours. So in 10 hours it should only be down to 50%. If you have a method of measuring the amps, just switch on several devices until you get about 5A drain.

It's best to test both batteries separately, because very likely only one has failed.

 

[pappajohn]

For testing actual capacity a 60 watt (main beam) headlamp bulb will give you a 5amp load.

 

[Manic]

You have 2x 100amp batteries but you only really have 100amps and if down to 10volts they’re probably toast