Best Practices for Battery Health and Management

[Officient]

Hi everyone!

Damn, it's hot out I'm currently working through my first summer with 3 x EG4 Wallmount Batteries in parallel with an 18k inverter. The manual does not mention much about recommendations on battery treatment after initial setup. I'm hoping to gain any wisdom that can be offered. The questions that stick out to me are the following, based on my experience with several electric vehicles:

1. Should I be looking to change the default settings for the minimum/maximum state of charge to prolong battery life if that is my goal? For example, it's recommended to keep electric vehicles below 80% and above 20% as a rule of thumb unless the power is needed. So, I would think during the summer you might keep batteries in this zone, as storage really isn't a problem.
2. How often should I charge to 100% and discharge to 20% to allow BMS calibration (or other percentages perhaps)? I know this was a big deal in the past for older EVs like the Nissan Leaf; otherwise, the BMS gets out of whack enough to be noticeable.
3. Should I be leaving the batteries at 100% SOC for a certain amount of time to help with BMS calibration? Again, this was a thing for older EVs like the Nissan Leaf, but it might not apply here.
4. Is there any issue letting the Chargeverter top off the batteries all the way to 100% until the Chargeverter stops pushing power? I have my batteries set up to the inverter without solar panels currently, looking to add those after I sort out a ground mount. I've been topping off the batteries with a generator and EG4 Chargeverter V2. I did this last night, and the Chargeverter ramped itself down and all the batteries went into standby after 10-15 minutes at 100% SOC. Just want to make sure this isn't tough on the batteries.

 

[jpwhit]

This thread has good info that is consistent with my knowledge about LFP and Li-ion batteries.

Ask Me Anything About LFP Batteries and More! – Industry insider at top EV firm

Can't you expose an LLM (chat ai) pretty easily by asking some spacial/physical questions referring to a photo?

diysolarforum.com

Yes, staying between 80% and 20% will increase the cycle life of any Li based battery significantly. it's a bigger factor for Li-Ion because it makes a bigger difference especially on the low end of the statistical cycle life. Whereas LFP will last a pretty long time even going outside that range, but staying inside that range can make LFP batteries last for very high cycle counts.

There seems to be a lot of misconception around balancing and SOC. But, how a BMS handles balancing is completely up to the design of the BMS. Most BMS designs I've done, have been based around chipsets like the LTC6812. This chip performs its balancing operation while the batteries are charging, not when the battery is at 100% SOC. And most of the BMS designs I'm familiar with work this way. They typically do that by shunting current around the high cells during the charge cycle.

 

[Hedges]

I think in the "Ask Me" thread, he said LiFePO4 not as big a deal to hold at 100%.

Look in resources for cell data sheets.
I was looking at CATL, table and graph showed allowed charge can be as high as 1C up to 80% and moderate temperature. Lower beyond those limits. 0.5C good over a pretty decent range.

Don't know if degradation goes high order, and backing off further is insignificant. But seems to me most stationary applications would rarely give reduced results charged at 0.15C. Exception being if you've got only a couple hours before clouds roll in.

I think air conditioning (refrigeration?) when appropriate would be more important than reduced SoC (for LiFePO4). Maybe use a refrigerator with desiccant bags as enclosure. Set to about 50F or 60F?

 

[hardtop]

For my EVE 304's temperature control has been the biggest issue. Its been 120F at 4PM for the past several days. I noticed I only get 2.6 kWh instead of 3.x kWh now.
I don't have A/C so I stopped charging in the afternoon and wake up at like 4 AM to start the generator to begin charging. The charger also likes it cooler because it will drop to about 47 AMPs from 60-62 AMPs when its warm. Its 118F ambient now and the battery temp. reads only 110F.

 

[Officient]

I think in the "Ask Me" thread, he said LiFePO4 not as big a deal to hold at 100%.

Look in resources for cell data sheets.
I was looking at CATL, table and graph showed allowed charge can be as high as 1C up to 80% and moderate temperature. Lower beyond those limits. 0.5C good over a pretty decent range.

Don't know if degradation goes high order, and backing off further is insignificant. But seems to me most stationary applications would rarely give reduced results charged at 0.15C. Exception being if you've got only a couple hours before clouds roll in.

I think air conditioning (refrigeration?) when appropriate would be more important than reduced SoC (for LiFePO4). Maybe use a refrigerator with desiccant bags as enclosure. Set to about 50F or 60F?

I have been considering a mini-split for the battery room, need to insulate first though. It's a metal box and get's quite hot. I try to charge in the evening. Morning is probably better.

 

[Hedges]

I have no experience with LiFePO4 yet but have some on the way.
San Jose is mild, but I'm toying with the idea of a refrigerator (insulation between it and top freezer already removed.) Would set thermostat around 60F, and a heating thermostat for lower end.

Chest freezer and Inkbird thermostat would be another idea.

It may be these batteries last far longer with comfortable temperature, and reduced charge rate. The CATL I'm getting, or at least different one of their cells, specify 0.2C, which is good enough for me.