Leisure battery 11.1v then 10.1 then 10.8 ??

[Aliceincamperland]

Hi. Currently away, been driving a couple of hours each day. This morning, woke up and the totalcool fridge display read F1. I unplugged and plugged it back in ( my go to!) And came back on. Battery display on it read 10.1. Is now (20 mins later)reading 11.2. The table above is from. The manual and I have it set to the M mode. I presume it turned off due to it reaching the 10.1v cut off. I have been having a Google and it suggests that thus is extremely low for a leisure battery....can anyone explain a little? Thanks.

 

[t0mb0]

Yes, it’s extremely low. The first thing to do is measure the voltage at the battery itself (or as close to as you can get). If this is similarly low, your leisure battery is very depleted, if not, it could be an issue with the wiring to the fridge from the battery.

How is your battery usually charged and is this the first time this has happened?

 

[Aliceincamperland]

The display on the wall of van says 11.3 whilst on fridge says 11.2. It just read now 9.9 so have flicked everything off. Normally charge by driving.

 

[Sim60]

Looks like your fridge and other electrics are taking more out of your leisure battery than you're putting back in each day. If the voltage is reaching 10.1V then the battery has low charge.
What sort of leisure battery do you have and how is it charged? If it's an AGM battery, then the voltage is an approximation to the state of charge of the battery- the lower the voltage, the lower charge remaining - But the measurement is also affected by the amount of current you are drawing out of the battery. You can find tables on the internet equating the 'no-load' voltage of the battery to its SoC or State of charge. While the fridge is drawing current from the battery , it's voltage will reduce below 'no load' voltage and in your case, when it reaches 10.1, the fridge will cut off. At this point, the battery voltage will start to recover. If you then re-connect the fridge, the battery may well show 11.2 V but will soon drop down to the cut-off point again under load if you are not charging it.

If the battery voltage is dropping this low regularly, you are probably damaging the battery and reducing its overall capacity and its lifetime.
Hope this makes sense

Simon

 

[Qnapper]

Your battery needs replacing as: 11.3 whilst on fridge says 11.2. It just read now 9.9volts on AGM signs its dead...... You can try to recover it, but you could be wasting time as when under load again it will drop down to 9.9volts again. Good luck.

 

[t0mb0]

The display on the wall of van says 11.3 whilst on fridge says 11.2. It just read now 9.9 so have flicked everything off. Normally charge by driving.

Ok, so probably a genuinely low state of charge on the leisure battery. As @Sim60 says above then, it’s a case of working out whether the battery is getting charged properly. You say it’s charged by driving, so the first thing to check is to start the van and check whether the voltage climbs (should be over 13v or so). If not, that indicates that it’s not being charged when driven as expected. If it is as expected, then the draw on it from the fridge etc has simply overcome however it’s being charged. In this case it’s a question of whether it’s from exceptional circumstances (e.g. heavy use and not much driving) or whether the battery itself is heavily degraded.

 

[roadtripper]

Anything below 50% charge on a Lead Acid/AGM is dangerously low and likely to cause damage. That's a resting voltage (no charge no load) of around 12.0v

Below this level you start to get damage to the plates in the battery that reduces the effective battery capacity very quickly.

If your battery is over 2 years old it might be time for a new one.

Generally I'd only advise using the H setting here - the 11.1v cut out setting accounts for the voltage drop that will occur when the fridge compressor is running. If you find your fridge cuts out a lot then you are not charging often enough.

Let's run some numbers. Generally a leisure battery is around 100Ah so with the 50% rule of thumb you can use 50Ah of that (so long as you have a DCDC charger, if you are split charging in a smart alternator van it only gets charged to about 80% so only 30Ah is usable..)

My compressor fridge draws about 60w and I would say it runs about a third of the time. So 60w divided by 12v is 5A - so the fridge is consuming 5Ah of capacity every 3 hours.

So on a fully charged battery the fridge will use the available capacity in 30 hours (50Ah divided by 5Ah times 3) or in a 80% split charge only 18 hours.

Assuming a nominal 25A charge rate 2 hours driving is just enough to replace 50Ah of charge, though the charge rate will slow right down in the last 10% - if you are draining the usable capacity of a 100Ah leisure battery you probably need a solid 3 hours of engine to fully charge if you are working off grid.

 

[roadtripper]

If you want some battery background I went through quite a few basics in this thread:

W

Thread 'Newbie battery charger questions'

11 Dec 2023

Hi all, I'm new to forum and to campervan ownership. We have bought a new T28 conversion and would like to understand the battery and charging setup. The items which depend on the battery in our van from the top of my head are: Fridge; Heater (its run off diesel but has a fan); Lights; Water pump for taps;

Having used our van across the british summer, its just had its first winter trip ...and with no hookup. I now realise I have no idea how its battery setup works. What I do know:

• It has a starter battery and a leisure battery (which I'm 99.9% sure is 12V lead acid and not lithium...

• wallport
• charging leisure battery
• Replies: 189
• Forum: Electrics, Lighting, ICE, Security

•