Did I get two bad chins?

[cdoublejj--]

dude you are affectivley farting around. Just get a capacity tester, https://www.amazon.com/gp/product/B07HB3XK7L/

charge them up slowly and run them down a few times, https://diysolarforum.com/threads/bought-a-25v-150ah-cloud-energy-to-try.62975/

though be warned these little takes days to discharge, but, then again at 4 amps it will take days to charge up too. thats not always bad thing, it gives the cells a chance to balance.

 

[Blakes]

+1 on using a shunt. The curve of a LiFePO4 is just too extreme on the ends and flat in the middle to really tell anything about SOC other than you're about > 90% or < 20%.

The chart in the Chins manual doesn't seem very accurate either. I just got a CHINS 12V 100A, it arrived at just under 13.2V, which according to the manual should mean about 20% but when I charged it it only took 42Ah in, which more closely fits this chart:

View attachment 153285

After running these two, 100ah chins for a month, I think this chart is pretty accurate.

I run these chins feeding my main array for about 5 hours every night at around ~500w of load.

They seem to be doing great and I plan to get a couple more when funds free up.

 

[DIYrich]

I would buy a shunt before more batteries. Unless you charge to float on a regular basis, especially when you add more batteries, it is hard to know the SOC. Even the shunt will have a hard time staying calibrated if not charged to full on a weekly basis.