Electrical problems - Lithium batteries

[recox]

Hello everyone,

I'm seeking some help to better understand my electrical system in my CamperVan. I have limited knowledge about electricity, but I'm eager to learn more.

The electrical system in my van was professionally installed. Currently, I have 3 lithium batteries (Vision SP12-200 - [link](https://www.cellpower.co.nz/shop/product/513843/a-vision-sp12-200a-lithium-battery-12-volt-200-ahr/)) connected in series, although for the tests and description in this post, I am using only one battery, with the others disconnected from the vehicle.

All the tests I'm conducting are with the batteries fully charged using the PowerTech MB3910 charger (which marks 13.17V). It's worth mentioning that after a recent road trip on New Year's Eve, the batteries were nearly drained, and their voltage had dropped to a very low level (around 2V, as checked with a multimeter). This caused the BMS system protection to activate. To charge them, I had to "jump start" them as demonstrated in this video ([link](https://www.youtube.com/watch?v=j2JjOpq50MI)) using a NOCO Boost 12V 500A Jump Starter - GB20.

I'm encountering several issues with my vehicle, and I'm hoping for assistance with the following:

1. **Water Pump**: I initially had a 25dpi water pump ([link](https://www.rvsupercentre.co.nz/flojet-3426-series-water-pump-11-lpm)), which didn't work well. I often experienced air bubbles in my water system, requiring me to manually prime the hose. I sent it to a caravan repairer for proper fixing, and they suggested replacing it with a 30dpi pump ([link](https://www.dometic.com/en-gb/professional/marine-solutions/boat-pumps/dometic-powerpump-pp1210-64063)). While it worked initially, it stopped functioning after a short road trip. The voltage readings for the pump are 11.18V (not running) and 11.68V (running), whereas the 25dpi pump never had this issue and reliably turned on.

2. **Battery Duration**: I have a 200Ah battery and want to determine how long it will last. To test this, I connected the battery to the van and used only the fridge (GASMATE 3-WAY UPRIGHT FRIDGE 62L - [link](https://www.gasmate.co.nz/product/62-litre-upright-camping-fridge/)). Here are my observations:
- Test A: I connected the battery at 6 PM, turned on the fridge, and the next day at 9 AM, the battery charge was nearly empty, as indicated by the Victron BMV 712 Smart ([link](https://www.victronenergy.com/display-and-panels/bmv-712-smart)). However, the voltage remained at 12.58V. The fridge was still operational and cool. After removing the battery, a multimeter read 12.69V, and I am currently recharging it.

All these pictures are part of Test A










- Test B: I connected another battery and left it running for approximately 24 hours (exact duration not remembered). When I checked, the electrical system, including the battery monitor, was completely off. After removing the battery, a multimeter showed 9.33V. Interestingly, the battery required another "jump start" to begin charging.

3. **Victron BMV 712 Smart**: I'm facing issues with the Victron BMV 712 Smart. The manual states that it should retain usage history for 45 days. However, every time I close the app or the system shuts down, it erases all data. Am I doing something wrong or is there a misconfiguration?


These pictures are for reference only, just one battery is in the vehicle in the tests.



Any help or insights regarding these issues would be greatly appreciated. Thank you in advance for your assistance!

 

[abnorm]

connected in series,

3 x 12 volt Batteries in SERIES is 36 Volt.................................

When you ran the fridge test ...12 volt or Mains voltage ?

For the most part this is a USA forum

 

[bullfrog !]

I believe Victron has a customer service tech department you could contact. Most manufacturers battery and electronic equipment have customer service or tech departments you should contact for specific product information. One of our members has a consulting business who may be able to advise you. Hopefully he will see this.

 

[jonyjoe303]

From what I can tell your batteries aren't being fully charged. Lifep04 requires at least 14.4 volts, I always charge mine to 14.6 volts. Your victron shows the max voltage reached was 14.16 volts (which is insufficient).
The mfg recommends charging at 13.6 to 13.8 volts which most chargers will be trickle charging at low amps for such large batteries. At higher voltage of 14.4 to 14.6 volts is when you will be sending max amps to the battery.

Many people recommend not to fully charge the lifepo4 batteries but it won't damage them I been charging my 220ah lifepo4 to 14.6 volts every day for the past 5 years, they are still working excellent.


These are the specs from the battery mfg. for your battery.
Recommended Charge Current 25A
Maximum Charge Current 50A
Recommended Charge Voltage 13.6 to 13.8
Charge mode CC/CV
BMS CHARACTERISTICS
Max Charge Voltage 14.4V-14.6V
Overcharge protection voltage 14.8V-15.2V
Maximum Continuous Discharge Current 100A
Discharge cut-off voltage range 9.2V-11.2V

Your victron is probably not properly calibrated, most coulombcounters have to reach max voltage (at least 14.4 or 14.6 volts whatever setting you set for max voltage) at least once to be properly calibrated. If your battery has never been fully charged to max voltage it won't know what percentage it is suppose to be at.

If my battery was reading 12.58 volts with no loads, it would be dead. For lifepo4 any voltage under 12.8 volts (no load) is 50 percent or less. Normal voltage for recently charge lifepo4 is always going to be over 13 volts (no load).

I don't think the powertech is fully charging the battery, at 15 amps, it would take 13 hours to fully charge to the powertech max voltage of 14.5 volts. When charging did you see if the max voltage of 14.5 volts was reached by the battery (on victron or multimeter). With lifepo4 you have to reach those voltages to get an idea if it is fully charge.
If there is voltage drop from the charger to battery, the chargers voltage LCD might be off, thats why its best to get the voltage reading from the battery terminal.