Do I have a problem with my leisure battery or am I just a worrier?

[Caderman]

I have a T5.1 and installed a new 100ah leisure battery 2 years ago. I also installed a 100w solar with Victron mppt controller.
I thought I’d pretty much be able to run my webasto CR 49 elegance fridge ( claims daily usage of 265 to 280 watts, which I think is equivalent to about 22 to 24 amps) and 12v lighting, planar diesel heater and charging phones etc with no need to worry about leisure battery health and no need for EHU.
Because I’m a worrier I installed a battery monitor connected directly to the leisure that tracks the battery voltage and it seems to be dropping more quickly than I’d expect. I’ve attached a couple of days worths of voltage graphs.
Welcome thoughts on whether I have a leisure battery problem or I’m worrying unnecessarily and had false expectations. The first graphs show impact of charging battery by split charger, the second includes impact of solar on a cloudy day (victron showed 40wh for that day). The variation in the graphs shows when the fridge kicks in. Thanks in advance for any assistance.

 

[Fisherman]

I believe in fitting two batteries, and I don’t use a compressor fridge.
If you are dropping to 50% on your battery as the reading shows this will shorten its lifespan.
You are far less likely to do so with two batteries. You should try not to drop below 12.4 volts when off load.
Also if you have a diesel heater they can draw more current on start up than gas.
If off grid in winter your solar is almost useless, two batteries would be a must then.

 

[jagmanx]

I have a T5.1 and installed a new 100ah leisure battery 2 years ago. I also installed a 100w solar with Victron mppt controller.
I thought I’d pretty much be able to run my webasto CR 49 elegance fridge ( claims daily usage of 265 to 280 watts, which I think is equivalent to about 22 to 24 amps) and 12v lighting, planar diesel heater and charging phones etc with no need to worry about leisure battery health and no need for EHU.
Because I’m a worrier I installed a battery monitor connected directly to the leisure that tracks the battery voltage and it seems to be dropping more quickly than I’d expect. I’ve attached a couple of days worths of voltage graphs.
Welcome thoughts on whether I have a leisure battery problem or I’m worrying unnecessarily and had false expectations. The first graphs show impact of charging battery by split charger, the second includes impact of solar on a cloudy day (victron showed 40wh for that day). The variation in the graphs shows when the fridge kicks in. Thanks in advance for any assistance.View attachment 99215View attachment 99216

I would also not ne happy.
For many years we had just 1 x 90ah LB but fridge and heating on gas.
I monitor the battery voltage and got twitchy at 12.7 V and believe we were never below 12.5 and then only at 3am.
With 120watt solar the battery soon recovered to well over 13 eg 13.5 most mornings.
Reading your figures yes do something
Maybe lithium or a 2nd battery....Just my opinion based on 7 years mainly off-grid AND summer only (6 months touring so input frpm alternator usually every 2nd day.
Others will be along with more scientific advice.

 

[wildebus]

There are quite a few people who claim you can run a 50L Compressor Fridge for a full long weekend on a single 100Ah battery.
What they forget to tell you is they arrive Friday night with a full battery and the fridge loaded with frozen bottles of water, they turn off the fridge overnight and they don't need it by Sunday lunchtime as they are on their way home.

Basically it is as you say .... you have false expectations rather than a battery problem.
You have room for more solar - on a T5.1 SWB you can fit upto 250W and easily have 200W on there. Add to the 100W if you are a summer camper and it will make a difference.
Adding a second battery to your setup will make a big difference. Currently you are just about ok but ending up watching the voltage rather than enjoying the experience. Ideally you would have two matched batteries installed at the same time. With the current one being 2 years old, it depends what the battery is to if it is worth adding one more or remove the current and get two fresh ones. What battery do you have fitted? (make/model)

 

[Caderman]

I believe in fitting two batteries, and I don’t use a compressor fridge.
If you are dropping to 50% on your battery as the reading shows this will shorten its lifespan.
You are far less likely to do so with two batteries. You should try not to drop below 12.5 volts when off load.
Also if you have a diesel heater they can draw more current on start up than gas.
If off grid in winter your solar is almost useless, two batteries would be a must then.

Thanks. have thought about 2 batteries but at the moment just trying to understand whether the one I have is doing what it should. Mine is AGM and battery supplier says that 50% is 12.1v so trying to keep it above that. Any thoughts about whether the voltage drop is to be expected given the load? I was expecting to get about 48 hours even without solar before it got to 12.1v.

 

[Fisherman]

Thanks. have thought about 2 batteries but at the moment just trying to understand whether the one I have is doing what it should. Mine is AGM and battery supplier says that 50% is 12.1v so trying to keep it above that. Any thoughts about whether the voltage drop is to be expected given the load? I was expecting to get about 48 hours even without solar before it got to 12.1v.

Read wildebus‘s post, he has forgotten more than I know.
But you do need a second battery.
Taking your battery down to 12.1v repeatedly is not a good idea.

 

[Tookey]

I DON'T KNOW but I presume fridge watts consumption provided by manufacturers is based on the fridge door not being opened during the 24hrs and at an ambient room temp of maybe 20c or else there are too many variables. With your front opening door on the fridge every time you open it you are dumping lots of that cold air on the floor and replacing it with ambient temp air so I'm not sure manufacturers wattage actually applies to real world

I only have space for one battery and therefore turn my fridge off at night and at this time of year the PV has filled my battery before I wake and it gets turned on again when I make my brew

Back to the point...........I cant help with your 'volt drop/load' question but if Wildebus doesn't think you have a fault it's likely you don't

 

[barryd]

12.1 should be ok as long as it doesnt drop much below that. This is the chart I always went by and Ive had no real issues.

I think its the fridge. We have a single 125ah battery and a single 100w panel on the roof with a clever MPPT Controller which shows Watts / amps in, watts / amps being used and the battery voltage. This time of year I have more power than I know what to do with and can stay in one place indefinitely for weeks on end. Always have laptops, TV, phones etc on charge or running. These last few days away by the time I switch off everything last thing voltage is generally about 12.4 or 12.5 but its fully charged by mid morning again. By Mid August, early September it might be getting down to 12.1 or 12.2 and after that I start looking for hookup or move around a bit. So similar set up to you apart from that Fridge. Get the battery tested maybe and if its ok you maybe need to think about a second panel and a second battery. Pointless getting one without the other though I think.

 

[Caderman]

There are quite a few people who claim you can run a 50L Compressor Fridge for a full long weekend on a single 100Ah battery.
What they forget to tell you is they arrive Friday night with a full battery and the fridge loaded with frozen bottles of water, they turn off the fridge overnight and they don't need it by Sunday lunchtime as they are on their way home.

Basically it is as you say .... you have false expectations rather than a battery problem.
You have room for more solar - on a T5.1 SWB you can fit upto 250W and easily have 200W on there. Add to the 100W if you are a summer camper and it will make a difference.
Adding a second battery to your setup will make a big difference. Currently you are just about ok but ending up watching the voltage rather than enjoying the experience. Ideally you would have two matched batteries installed at the same time. With the current one being 2 years old, it depends what the battery is to if it is worth adding one more or remove the current and get two fresh ones. What battery do you have fitted? (make/model)

Thanks. - it’s a

Advanced AGM LP100 Leisure Battery 100ah 12v

 

[Tookey]

12.1 should be ok as long as it doesnt drop much below that. This is the chart I always went by and Ive had no real issues.

I think its the fridge. We have a single 125ah battery and a single 100w panel on the roof with a clever MPPT Controller which shows Watts / amps in, watts / amps being used and the battery voltage. This time of year I have more power than I know what to do with and can stay in one place indefinitely for weeks on end. Always have laptops, TV, phones etc on charge or running. These last few days away by the time I switch off everything last thing voltage is generally about 12.4 or 12.5 but its fully charged by mid morning again. By Mid August, early September it might be getting down to 12.1 or 12.2 and after that I start looking for hookup or move around a bit. So similar set up to you apart from that Fridge. Get the battery tested maybe and if its ok you maybe need to think about a second panel and a second battery. Pointless getting one without the other though I think.

Barry, is that table for a Lead Acid?

 

[Fisherman]

State of Charge	Sealed or Flooded Lead Acid battery voltage	AGM battery voltage
100%	12.70+	12.80+
75%	12.40	12.60
50%	12.20	12.30
25%	12.00	12.00

 

[Caderman]

12.1 should be ok as long as it doesnt drop much below that. This is the chart I always went by and Ive had no real issues.

I think its the fridge. We have a single 125ah battery and a single 100w panel on the roof with a clever MPPT Controller which shows Watts / amps in, watts / amps being used and the battery voltage. This time of year I have more power than I know what to do with and can stay in one place indefinitely for weeks on end. Always have laptops, TV, phones etc on charge or running. These last few days away by the time I switch off everything last thing voltage is generally about 12.4 or 12.5 but its fully charged by mid morning again. By Mid August, early September it might be getting down to 12.1 or 12.2 and after that I start looking for hookup or move around a bit. So similar set up to you apart from that Fridge. Get the battery tested maybe and if its ok you maybe need to think about a second panel and a second battery. Pointless getting one without the other though I think.

 

[trevskoda]

I followed all the tests when wildbus was going through the motions, I now to have 2 90ah batts and 200w solar running through a voltronic mppt regulator, 24 hrs with only a mini fridge running is about it without killing the batts, listen to what he is telling you.

 

[Caderman]

Barryd, thanks for that. Agree, suspect if I didn’t have a fridge I would be rolling in spare amps. I’m off to Cornwall for a couple of weeks and will take the opportunity to check out how many amps my fridge uses with a clamp ammeter. I’ve also got a flexi 100w solar panel which I can connect for additional solar if needed so won’t have a problem but as Wildebus said in his reply, I’m trying to move away from watching the voltage to enjoying the experience

 

[barryd]

Barryd, thanks for that. Agree, suspect if I didn’t have a fridge I would be rolling in spare amps. I’m off to Cornwall for a couple of weeks and will take the opportunity to check out how many amps my fridge uses with a clamp ammeter. I’ve also got a flexi 100w solar panel which I can connect for additional solar if needed so won’t have a problem but as Wildebus said in his reply, I’m trying to move away from watching the voltage to enjoying the experience

I guess you could tell if you could live without the fridge for a few days to see if its the problem. Doubling up solar though (so I am told) its best to double up the battery bank also.

 

[barryd]

Barry, is that table for a Lead Acid?

Dont know. Cant remember where I got it from. I have had two batteries on this van. A 110ah Banner which lasted six or seven years and this 125ah bought in France (maintenance free, cant remember the model) also six to seven years. Both been well hammered. This one must be about to die but still seems to be doing well. Cost me about 100 euros.

 

[molly 2]

I would think your 100 solar panel is too small on a good ,on a bad day when heating is needed you solar harvest will be almost nothing .a battery monitor that counts amps in and out is more informative. That a voltmeter.

 

[Caderman]

Thanks to everyone for their replies. Very interesting and helpful. For my own benefit I thought I‘d summarise my take out from the posts. Apologies if I’m stating the obvious.

1. It looks like my set up is on the edge of sufficient power ( battery + solar). In my defence I installed a typical set-up that Campervan converters install to run the equipment I’ve got.
2. Given all the changing variables on battery power consumption I can see why people plan on having more than you need rather than the exact amount to avoid voltage watching. - most suggesting about twice what I’ve got.
3. Beware of stated power consumption from suppliers as they may underestimate real life usage.
4. Having a monitor that watches amps and voltage is more useful than one that just watches voltage.
5. Different battery suppliers advise different voltage levels to reflect 50% depletion for AGM batteries (12.3 and 12.1).

If I am to increase my battery power and have limited resources should I
A. Invest in extra 100w solar and buy a second battery and so have a new one and my 2 yr old one ?
Or
B. Invest in 2 new batteries (ie keep solar as is).
Bear in mind my aim is to enjoy the experience and not watch the voltage. We could be parked up for upto 4 days in one spot. ?

 

[Tookey]

Be aware that if you become a full member you are entitled to a discount at Alpha batteries so could easily cover the cost of your membership immediately

 

[wildebus]

Thanks to everyone for their replies. Very interesting and helpful. For my own benefit I thought I‘d summarise my take out from the posts. Apologies if I’m stating the obvious.

1. It looks like my set up is on the edge of sufficient power ( battery + solar). In my defence I installed a typical set-up that Campervan converters install to run the equipment I’ve got.
2. Given all the changing variables on battery power consumption I can see why people plan on having more than you need rather than the exact amount to avoid voltage watching. - most suggesting about twice what I’ve got.
3. Beware of stated power consumption from suppliers as they may underestimate real life usage.
4. Having a monitor that watches amps and voltage is more useful than one that just watches voltage.
5. Different battery suppliers advise different voltage levels to reflect 50% depletion for AGM batteries (12.3 and 12.1).

If I am to increase my battery power and have limited resources should I
A. Invest in extra 100w solar and buy a second battery and so have a new one and my 2 yr old one ?
Or
B. Invest in 2 new batteries (ie keep solar as is).
Bear in mind my aim is to enjoy the experience and not watch the voltage. We could be parked up for upto 4 days in one spot. ?

for #1, it is quite likely you were guided by some comments on the VW T4 forum you might have read (I noticed you posted the question on there as well). So I am not surprised at the results as it is on that forum you get a a few folk bragging about how they can run a fridge, TV, Heater, etc on a single 100Ah for a whole weekend. However, quite simply, as Scotty would say ... "ye cannae change the laws of physics, Jim".

For #2, yup.

For #3, yup. The numbers quoted for the Fridge are best case. When the outside temp goes up, the fridge consumption goes up and it can virtually double.

For #4, indeed. A Voltmeter is certainly better than nothing and if you know how the voltages relate to the state of charge for YOUR battery, then it can be a reasonable, if somewhat flawed, way to keep an eye on the battery.

For #5, it can vary on the battery technology and on different types of AGM batteries as well. There are some very flawed voltage vs SOC graphs out there (I saw one totally incorrect one posted on a popular forum recently which will have really messed with the questioners mind if he believed it!). Personally, I tend to regard a resting voltage (resting means no charge received or no load taken for about an hour) of 12.05V as 50% to be a decent target and as there is usually some kind of load going on, try to avoid the battery dropping below 12V (easier to remember then a 100th of a value) on a typical Lead-Acid battery. But the lower it goes, the lower the service life - and that applies above 50% discharge as well.
If you have 2 batteries which allow you to not go below 75%, they will last MORE THAN TWICE a single battery going to 50%.

In your voltage graphs you also never started from a full battery. Looking at the first graph, the end voltage was just about the same as the starting voltage. The second graph you dropped down to 12.09V but again you started at a fairly low voltage point.
What are your charging devices? Have you got a B2B Charger for when driving or just a Split Charge VSR?
Note that a VSR will not provide a way to fully charge an AGM Battery and the best you could hope for with a standard Lead-Acid AGM Battery is around 80%. Doing the maths, starting with 80% and avoiding dropping below 50% leaves you with around 30% of the battery capacity to work with - just 30Ah of your 100Ah battery. You might want to consider the charging aspect. a B2B could take the battery to 100% and give you potentially nearly a 2nd battery with another 20Ah (as opposed to another 30Ah if you added one but had the same charging limits).