HELP - Leisure Battery Low in AM

[Lenny HB]

I initially added the BMS between the two battery's but Piers pointed out that I wouldn't get an accurate reading with that.

Now I can obsessively check the health of the batteries

A true Motorhomer.

 

[Stug.]

Hi
Just my opinion.
Each to their own, and I know we all have different needs but...
If I had your problem with energy usage I'd ditch the fridge.
Good cool box, bag of ice every few days if that. Going somewhere cold? Stick your wine/beer in the snow
Suddenly things look totally different.
Stug

 

[Raul]

So reporting back on my experience with BatteryMegastore.

Piers was very helpful and advised not to upgrade to the 60A B2B. I bought 2x 84Ah LiFePo4's and the Victron BMS-712 with the 30% discount offered to MHFUNsters.

As I needed additional cabling (BMS shunt required larger diameter terminals and I was connecting two batteries) he provided advice, custom length cables, and tools to allow me to complete the work in their carpark.

Piers even helped me set up the B2B and MPPT to output the correct voltage for the new LiFePo4's and didn't charge us for the 2 meters of 50mm cable and terminals!

After running the Dometic CRX65, 1x cell phone 1x laptop on charge overnight, and Wallas diesel heating for 1 hour before lights out we were left with 94% capacity at 7am this morning.

Couldn't be happier

View attachment 354741

At 13.1v your LiFePo4 is quite discharged very close to 10-15% SOC. At 95-96% soc your voltage should be close to 13.35v. I think you need to calibrate your bmv (not bms, that’s diferent animal), and dial in appropriate settings for LiFePo4 on your bmv monitor. And no issue at all reading two batteries in parallel, it will see it as one bank.

 

[Pausim]

Not all LiFePO4 batteries have the same discharge characteristics. My Relion is about 70% SOC at 13.1V and 15% SOC is nearer 12.6V. The discharge rate can make a big difference to SOC voltages.

 

[Otter Spotter]

£1000 plus $140 for the BMS just after Christmas

What else Did you want anything else for Christmas but a new battery ?

^{_{Subscribers  do not see these advertisements}}

 

[Raul]

Not all LiFePO4 batteries have the same discharge characteristics. My Relion is about 70% SOC at 13.1V and 15% SOC is nearer 12.6V. The discharge rate can make a big difference to SOC voltages.

I agree that cells differ, due to construction type, and much to do with internal resistance. I have no experience with cylindrical cells but, prismatic’s are quite flat from 10-20 to 80 ish state of charge, around 3,2v per cell: 12.8v hence the nominal voltage terminology. I remember taking out 300ah of 400ah and voltage was above 13.2v. Like you said, it may differ.

 

[minesapint]

Thank You, guys. Great advice, all.

With our aspiration to see Norway in January, I think peterc10 suggestion of a generator is probably the way to go given our free-camping lifestyle.

I can plug the genie into the shore power charger (Victron Blue Smart IP22 charger) for a boost at sundown and rise. Being in the UK now we can trial this scenario and determine if we also need to replace the leisure battery (which I'd like to avoid given the Xmas expenses!).

So, onto researching generators.

Why not simply pull onto a proper camp site with EHU, occasionally and give the batteries a good charge up.

To keep running the engine will only give automotive problems in time, and running a generator could upset others with its noise.

 

[JJ]

AGM's are pretty useless for leisure battery and quite common for them to fail at not much over a year old.

Could you tell me your source(s) for this statement?

What does "quite common" actually mean?

I ask because I know of experienced, long term motorhomers who always use AGM batteries and have had them last over 5 years yrouble free.

Also my new to me van has an AGM battery.

Thanks in advance...

JJ

 

[Raul]

Could you tell me your source(s) for this statement?

What does "quite common" actually mean?

I ask because I know of experienced, long term motorhomers who always use AGM batteries and have had them last over 5 years yrouble free.

Also my new to me van has an AGM battery.

Thanks in advance...

JJ

I can tell you from personal experience. Agm’s are built with limited cycle life, and they intended use is shallow cycle. They charge and discharge the fastest of all lead, but they reserve capacity is low. Your known friends have had 5 years out of them because extra capacity and good charging rates. Being that by chance or knowledge. If you need 20ah daily, and you got a 100ah agm, and your recharge capacity is 20-30a, then you will have a 5-6 year life out of that battery without hiccups. Throw this balance out, and your battery will die prematurely. It’s not the agm,s fault, but the users inexperience and misuse.
Airplanes use agm, boats use thick plate flooded, and drones use lithium’s, there is a niche and suitability for everything.