Leisure Battery - accidentally drained, what next?

[interbear]

Hi all. My testing today went something like this.

• Charged overnight via EHU
• 07:20 - battery was 100% at 13.8V. I then unplugged the EHU and switched on the fridge to run from the battery.
• 09:20 - battery was 88% at 12.6V. I switched off the fridge to see if the battery maintained its charge.
• 11:50 - battery was still 88% at 12.6V. I switched the fridge on again to run from the battery.
• 14:50 - battery was 77% at 12.5V. I plugged the EHU back in and turned the fridge off.
• 18:50 - battery was back to 100% at 13.8V.

So, it seems to charge back up to 100% and 13.8 V reasonably consistently when plugged in.

In terms of drain when running the fridge from the battery, the first session it drained 12% over 2 hours, the second session it drained another 11% over 3 hours. Is this reasonable or does it suggest some damage? It does have a solar panel always feeding it which probably helped reduce drain later in the day.

I think it may be OK but I’m not sure so hoping you more experienced owners may be able to advise. If the answer is “just f’ing replace the battery”, that’s what I’ll do.

 

[TallPaul_S]

What fridge do you have? Mine is a CRX50 (equivalent) which only uses 1Ah to 1.5Ah per hour in 25 degrees, on a 75Ah battery that's about 1.6% per hour. When I tested it tested it recently in 10 degrees it was only using 1% per hour Which is about right I think.

12% per hour is a lot for a fridge. You'd barely get 5 hours if you're on an AGM battery.

 

[AussieMick]

When you charge your battery on the charger the 13.8v is only the result of being on a charger.
You have to let it stand for a while or put a temporary load on the battery to get a true reading.

An charged agm will be around 12.8v.

Once the compressor on the fridge runs it will drop a couple of volts eg 12.5v and when the compressor stops running the voltage should recover upwards towards 12.8v.

When a battery is no good it will lose voltage quickly when the fridge or load is applied. Eg. Drop from 12.8v to 10v
Or not hold a charge where once load is applied to battery it drops voltage much quicker than a good battery. Rather than last a couple of days it will drop below 50% charge in a few hours.

You can't measure the battery voltage with it connected to a charger as you are measuring the charging voltage not the true battery voltage.

 

[Howzat]

23% of a 100ah battery in 5 hours is a lot of drain just for a fridge, especially if you have solar feeding in as well. Your testing suggests the fridge is using about 5 amps per hour. That's a lot. If your fridge is using that much then it's either a massive fridge, is faulty or was left open. What fridge is it?
More likely it's the battery at fault. You're only supposed to run an AGM down to 50% so another 5 hours and you'd be down to that.
When I first got my leisure battery (80ah LiFePO4) and fridge I ran the fridge off it at home to about 10% and it ran for about 4-5 days from memory. I posted about it here. Will see if I can find the post.

EDIT: Wow, it was even better than I remember. Down to 68% after 3 days.

Fridges & Cold Beer -- How I Done It --

thanks so much for the replies what was the brand ?

www.t6forum.com

 

[roadtripper]

What happens if you don't switch the fridge on?

Eliminate the possibility you have another drain elsewhere.

 

[interbear]

What happens if you don't switch the fridge on?

Eliminate the possibility you have another drain elsewhere.

No drain at all today when the fridge was off for 2.5 hours. Stayed at 88% / 12.6v.

 

[interbear]

What fridge do you have? Mine is a CRX50 (equivalent) which only uses 1Ah to 1.5Ah per hour in 25 degrees, on a 75Ah battery that's about 1.6% per hour. When I tested it tested it recently in 10 degrees it was only using 1% per hour Which is about right I think.

12% per hour is a lot for a fridge. You'd barely get 5 hours if you're on an AGM battery.

It’s a 100a AGM battery and the fridge is a 50L VitriFrigo fridge / freezer.

This one:

 

[interbear]

23% of a 100ah battery in 5 hours is a lot of drain just for a fridge, especially if you have solar feeding in as well. Your testing suggests the fridge is using about 5 amps per hour. That's a lot. If your fridge is using that much then it's either a massive fridge, is faulty or was left open. What fridge is it?
More likely it's the battery at fault. You're only supposed to run an AGM down to 50% so another 5 hours and you'd be down to that.
When I first got my leisure battery (80ah LiFePO4) and fridge I ran the fridge off it at home to about 10% and it ran for about 4-5 days from memory. I posted about it here. Will see if I can find the post.

EDIT: Wow, it was even better than I remember. Down to 68% after 3 days.

Fridges & Cold Beer -- How I Done It --

thanks so much for the replies what was the brand ?

www.t6forum.com

Fridge was on but closed.

I don’t think the fridge is the problem, I think it’s the fact I accidentally left the electrics on for a couple of weeks and let the battery run down to zero, which may have damaged the battery based on everything I’ve read about battery management.

 

[roadtripper]

It sounds most likely that it's damaged and has reduced capacity.

I'm mildly surprised that's occured in a single incident, do you normally keep it above 50%?

Does your charger have an logging, it would be interesting to see how much charge it thinks it has put in.

 

[Howzat]

Your battery is goosed.

Fridge Technical Information

Weight 16 kg
Dimensions 532mm (h) x 380mm (w) x 342mm (d)x 384 mm
Flush Depth (mm) 384
Volume (litres) 42
Voltage options 12/24V DC (upgradeable to 12/24 & 110-240V AC)
Consumption in Watts (with compressor running) 31W
Average 12 Volt Consumption (over 24 hours in UK summertime) 0.4A/h
Freezer volume 3.6 litres

 

[interbear]

When you charge your battery on the charger the 13.8v is only the result of being on a charger.
You have to let it stand for a while or put a temporary load on the battery to get a true reading.

An charged agm will be around 12.8v.

Once the compressor on the fridge runs it will drop a couple of volts eg 12.5v and when the compressor stops running the voltage should recover upwards towards 12.8v.

When a battery is no good it will lose voltage quickly when the fridge or load is applied. Eg. Drop from 12.8v to 10v
Or not hold a charge where once load is applied to battery it drops voltage much quicker than a good battery. Rather than last a couple of days it will drop below 50% charge in a few hours.

You can't measure the battery voltage with it connected to a charger as you are measuring the charging voltage not the true battery voltage.

Useful info thanks. I did switch the charger off when I checked the battery voltage. Its not connected to EHU now so I’ll see how it looks in the morning and will then test with the fridge on again tomorrow. I won’t plug in at all tomorrow and see where that ends up.

 

[interbear]

It sounds most likely that it's damaged and has reduced capacity.

I'm mildly surprised that's occured in a single incident, do you normally keep it above 50%?

Does your charger have an logging, it would be interesting to see how much charge it thinks it has put in.

Whenever I’ve checked the battery previously it seems that the solar keeps it at 100% and/or as we use the van pretty regularly as a daily driver (or every couple of days anyway) that also keeps it topped up.

I’ve never felt the need to plug in at home, only to EHU when on campsites.

 

[interbear]

Your battery is goosed.

Fridge Technical Information

Weight 16 kg
Dimensions 532mm (h) x 380mm (w) x 342mm (d)x 384 mm
Flush Depth (mm) 384
Volume (litres) 42
Voltage options 12/24V DC (upgradeable to 12/24 & 110-240V AC)
Consumption in Watts (with compressor running) 31W
Average 12 Volt Consumption (over 24 hours in UK summertime) 0.4A/h
Freezer volume 3.6 litres

It’s looking like this is the unfortunate reality, I agree.

 

[TallPaul_S]

Looks like that Fridge is a GR50 which is rated at 2.8a/36w max power, so yeah it'll only be using an amp or even less per hour in normal usage.

Another thing to test would be to leave something charging via USB that's dead - like a phone - which will only need a tiny amount to fully charge, less than an aH. Test before you plug it in, ideally with no solar and no charging beforehand, then after with the same. Your battery voltage should be only a tiny bit lower.

Ultimately, I think your battery is toast, though.

 

[TallPaul_S]

Whenever I’ve checked the battery previously it seems that the solar keeps it at 100% and/or as we use the van pretty regularly as a daily driver (or every couple of days anyway) that also keeps it topped up.

I’ve never felt the need to plug in at home, only to EHU when on campsites.

All you would have needed, with the fridge running constantly, would be a couple of dull days with only a few Ah of solar - if your fridge was using say 15h-20Ah per day - 2 days with no solar and you've used up 30 or 40ah, and you're down to 60-70% - and that's if your battery was full to start with. As you tested the heater, it probably wasn't. You'd get about 30Ah per day in full sun from a 100w panel, so it's really not hard to only see a few Ah from solar. Then you're at a 10-15Ah deficit every day.

If you're not driving it once a week at least, you're relying on solar to put back in what the fridge has taken out, which during the UK winter, it simply won't be. Not with a 100w panel.

 

[interbear]

All you would have needed, with the fridge running constantly, would be a couple of dull days with only a few Ah of solar - if your fridge was using say 15h-20Ah per day - 2 days with no solar and you've used up 30 or 40ah, and you're down to 60-70% - and that's if your battery was full to start with. As you tested the heater, it probably wasn't. You'd get about 30Ah per day in full sun from a 100w panel, so it's really not hard to only see a few Ah from solar. Then you're at a 10-15Ah deficit every day.

If you're not driving it once a week at least, you're relying on solar to put back in what the fridge has taken out, which during the UK winter, it simply won't be. Not with a 100w panel.

In normal circumstances the van gets driven more than once a week. In an unlikely set of unfortunate coincidences I messed up and left the electrics on after testing the diesel heater and the van was not used for a couple of weeks. And it’s rained constantly during that period so solar was limited anyway.

Mainly though, I f***ed up, which is a lesson for me in battery management. In future I’ll need to do a more regular check on battery capacity and perhaps set a schedule in my calendar to plug it in regularly.

I’ll contact the convertor and see what advice they give me on replacing the battery.

 

[TallPaul_S]

That's one of the reasons why all my electrics in my kitchen pod I'm building will be switched, I can still have the aux battery power the diesel heater, or lights, USB, water pump etc without having the fridge on.

 

[interbear]

That's one of the reasons why all my electrics in my kitchen pod I'm building will be switched, I can still have the aux battery power the diesel heater, or lights, USB, water pump etc without having the fridge on.

Indeed. The control panel in my van has separate switches for lights, fridge and water pump. Or a master switch to switch everything on or off. I left the master switch on after testing the diesel heater, hence the apparent problem.

I unplugged the EHU last night, the battery had a full charge. I’ll check it this morning, leave it unplugged and switch the fridge on to see how long the battery lasts today.

EDIT: Just checked, after overnight unplugged the battery is showing 100% and 12.8V. Fridge now switched on.

 

[MK2Golf24v]

Your "testing" seems totally unconclusive.

If the fridge is off, its warm, of course it will use a chunk of power when you switch it on to get it cold! It only becomes really efficient when its at temp and only maintaining it.

 

[roadtripper]

He's loosing around 10aH of capacity (if the battery is at original capacity) an hour. That's an average drain of 10A or 120w - no fridge is going to draw that current sustained for 2 hours.