105ah x 2 and 2000w pure sine wave inverter

sunrise

Solar Enthusiast
Joined
Jul 16, 2020
Messages
188
Hey folks,
Currently I have 2 LiFePo4 banks (105ah x 2, with 2 120a JBD BMSes) in my small camper trailer and it works very well. I am adding a 2000w (continuous) inverter and wondering if it's safe - The cells are rated 1C, so if I trust that it should be fine, but I am worried the connectors(M4 bolts, I think, not the M6 in 280ah ones), and busbars are little too small for this kind of current. I need about 1500w for 5 minutes or so coffee maker, microwave, hairdryer, etc, but most of time it's under 500w. My cells are wrapped in fiberglass reinforced tape and then put in a plywood enclosure - it's not clamp compressed though.
Question 1 - when one bank is out of juice, would > 1C discharge permanently damage the 120A BMS on the other bank, or it will just shut off and OK?
Question 2 - Is it a good idea to use them with the 2000w inverter? When it discharge close to 1C, would the cell swell and damage the cell rod since cells are wrapped pretty tightly? Would I be better off getting a 280ah ones?

Thanks in advance!
 

MisterSandals

Participation Medalist
Joined
Nov 5, 2019
Messages
5,053
Location
Silicon Valley
210Ah x 12.8V = 2688Wh
when one bank is out of juice
If they are wired in a balanced manner, they should run out of juice at the same time. But in reality, one BMS would likely hit LVD before the other. The BMS should protect the batteries for low voltage and over current.

When it discharge close to 1C, would the cell swell and damage the cell rod since cells are wrapped pretty tightly? Would I be better off getting a 280ah ones?
From what I've seen/heard/know, its usually over charging that leads to cell bloating. Your BMS can be configured to cut out at your preferred current if you want to protect your batteries.
280Ah? Mo bigger is mo better if you can fit and afford them! Though I do not see your use case as specified requiring bigger batteries.

2688Wh / 1500W = 1.8h runtime.

Have you done a daily energy audit to see if your batteries cover as many days as you are expecting without recharging?
What is your method of recharging?
 

sunrise

Solar Enthusiast
Joined
Jul 16, 2020
Messages
188
210Ah x 12.8V = 2688Wh

If they are wired in a balanced manner, they should run out of juice at the same time. But in reality, one BMS would likely hit LVD before the other. The BMS should protect the batteries for low voltage and over current.


From what I've seen/heard/know, its usually over charging that leads to cell bloating. Your BMS can be configured to cut out at your preferred current if you want to protect your batteries.
280Ah? Mo bigger is mo better if you can fit and afford them! Though I do not see your use case as specified requiring bigger batteries.

2688Wh / 1500W = 1.8h runtime.

Have you done a daily energy audit to see if your batteries cover as many days as you are expecting without recharging?
What is your method of recharging?
I can only fit 1 single 280ah DIY battery. But that would cost me around $800 (cells + 200A BMS).

I recharge them in 3 different ways
- Converter/Charger - 50A max, so max charging current 20-25A per battery, I have been doing this for a year now, no worries.
- Solar panel, I have 300W solar. 10A per battery max.
- Car alternator through 7-way plug, I only get about 5A charging current, but that's ok.

So I am not worried about bulging during charging.
 
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