What do you consider the minimum voltage for AGM leisure batteries?

[ThomasHJ]

I have always wondered what the minium voltage level is for the (AGM) leisure batteries. I never seem to find a straight answer, mentioning a certain voltage number. Neither on websites or on the forums here. Or when I do, it differs from other sources that mention a different number. The answer to the question doesn't seem straightforward, because the voltage of a battery should be measured without load, and without it being charged and after (at least) 12 hours in rest. Which, when using the van, isn't a realistic option.

Today I found the following article online, which explains in depth the way AGM batteries work and I found it very enlightening. Perhaps it is of use to others here. For some it may not be new, for some it might be useful.

Still wondering though, what is the lower limit you use for the voltage? In other words, at what V (as shown on the control panel and not being on EHU) do you feel you can no longer use the van's electricty and really need to either drive the van or get on EHU?

 

[kurienp]

That is an interesting article indeed. Thank you for sharing. Never have had my batteries very low, so cannot comment. When on a trip, we do move every 2-3 days ... and so have not yet had the lead time for the battery to drop beyond an inconvenient number.

 

[KGCali]

The fridge and auxiliary heater won't work if your battery is below 11.7 volts so I'd say the minimum voltage on the control panel would be around 12.3v which could drop as soon as you switch an appliance on.

 

[Ozzy Pete]

I have always wondered what the minium voltage level is for the (AGM) leisure batteries. I never seem to find a straight answer, mentioning a certain voltage number. Neither on websites or on the forums here. Or when I do, it differs from other sources that mention a different number. The answer to the question doesn't seem straightforward, because the voltage of a battery should be measured without load, and without it being charged and after (at least) 12 hours in rest. Which, when using the van, isn't a realistic option.

Today I found the following article online, which explains in depth the way AGM batteries work and I found it very enlightening. Perhaps it is of use to others here. For some it may not be new, for some it might be useful.

Still wondering though, what is the lower limit you use for the voltage? In other words, at what V (as shown on the control panel and not being on EHU) do you feel you can no longer use the van's electricty and really need to either drive the van or get on EHU?

I’ve seen many people on here say they can get 4 days out of their batteries running the fridge without charging. Surely that would mean the batteries are completely flat and therefore damaged. Traveling short distances won’t charge the batteries enough to give them a good enough charge so need to be on hook up. I have to say that I have seen my batteries down to 20% (don’t remember the voltage) but after a good charge they are back to the way they were.

 

[capt kirk]

As mentioned before I have flattened my batteries twice by accident. Once left the fridge on while on the drive and once away for a long time and had to run the van to charge them. I did a non scientific test while in lockdown just to see how long they would do and they lasted 5 days with the fridge on 3. I didn't go longer as I didn't want them completely flat. They are just coming up to four years old and as far as I can see still doing the job just fine. If they die soon ill let you all know.

 

[Ch1pbutty]

I’ve seen many people on here say they can get 4 days out of their batteries running the fridge without charging. Surely that would mean the batteries are completely flat and therefore damaged.

Some fridges (Dometic CFX ) are designed to cut off before the batteries get too low to prevent this.

 

[ThomasHJ]

So, it seems (so far, in this thread) no-one really has a number that they use / consider the lowest voltage the battery should go? Except for @KGCali who mentions 12.3 based on the cutout voltage of the fridge. This surprises me. I'd think more people would (want to) know what the lower limit is. I can't imagine every Cali owner on here camping without power for a max of 2 nights or so. Or always being on EHU when camping. And I also doubt everyone has solar.

Anyone?

 

[Loz]

It has been discussed before, but the minimum voltage at which the warranty becomes void is 10.6V

 

[ThomasHJ]

Yes, thanks @Loz. I did find an older thread in which you mention 10.6V and it's interesting information. And good to know, absolutely. However, 10.6V seems like a number -below- a sensible voltage. And since it is also well below the point where the fridge turns itself off, it's not particularly usefull for real life camping situations. After my fridge (and the heater) stops itself, I hardly need any power anyway. Camping is over.

My question basically is variation of the often asked 'how long can you go camping without EHU', but since usage, battery age, and other variables differ between different vans/people, battery voltage seems the most logical indicator of how long you can camp without EHU.

It would really help me to know, when I am camping for several days without EHU, at what voltage I should move on, drive for a while or find EHU. So I don't worry about messing up my (expensive) leisure batteries.

 

[WelshGas]

So, it seems (so far, in this thread) no-one really has a number that they use / consider the lowest voltage the battery should go? Except for @KGCali who mentions 12.3 based on the cutout voltage of the fridge. This surprises me. I'd think more people would (want to) know what the lower limit is. I can't imagine every Cali owner on here camping without power for a max of 2 nights or so. Or always being on EHU when camping. And I also doubt everyone has solar.

Anyone?

Personally I use 12v as my limit. Normally the Fridge or Parking Heater won’t start at this level, as the startup voltage drops below the 11.5v cutoff point.
However, if already running then they will continue to do so for a few hours.

 

[paul_f]

My CFX3 35 cuts off at 11.4V

 

[sidepod]

#overthinkingit

 

[Loz]

Yes, thanks @Loz. I did find an older thread in which you mention 10.6V and it's interesting information. And good to know, absolutely. However, 10.6V seems like a number -below- a sensible voltage. And since it is also well below the point where the fridge turns itself off, it's not particularly usefull for real life camping situations. After my fridge (and the heater) stops itself, I hardly need any power anyway. Camping is over.

My question basically is variation of the often asked 'how long can you go camping without EHU', but since usage, battery age, and other variables differ between different vans/people, battery voltage seems the most logical indicator of how long you can camp without EHU.

It would really help me to know, when I am camping for several days without EHU, at what voltage I should move on, drive for a while or find EHU. So I don't worry about messing up my (expensive) leisure batteries.

I think you have answered your own question, the minimum voltage is when you can no longer use anything, so long as you don't let it get below the 10.6v floor.

Once your fridge stops working you can still use led lights for hours, but if you are leaving the site the next morning then your milk will still be good in the morning for breakfast before you leave.

The next stage is to add solar to extend your off-EHU time until you next run the engine to charge it all up.
Next is more battery capacity.

This is what we used to do when we were Overlanding with a roof tent. It's all about timing and working with a portable leisure battery that was charged when driving, but just ran a fridge for an afternoon, evening and overnight, it was no good for the fridge after that unit we drove off again.

 

[ThomasHJ]

Hi @Loz, thanks for your reply. So basically what you are saying is, the voltage at which things (fridge, heater, etc) turn themselves off, is in practise also the minimum voltage. And that's well above the 10.6v at which the battery will be in danger of permanent damage, so effectively the minimum voltage is the moment stuff turns itself off (keeping in mind that the fridge/heater need more juice to work/power up, so will cut out earlier then the lighting). Do I understand you correctly? That would surely put my mind at ease.

 

[Kingfisher]

I now have solar, but before that I was using 12.0 V as a decision point. If the display was showing less than that in the morning, I would do something about it that day (EHU, drive, or run engine).