Why would new lifepo4 batteries state-of-charge drop so fast within a week of sitting?

[Rocksnsalt]

Yeah I’m well aware it’s a Chinese co… as are seemingly 95% of battery makers.
I’m also well aware of some of the shady the practices.
@Will Prowse seems to find some decent and some very good quality Chinese batteries and in fact one of his videos is how I became aware of Vestwoods. It was good quality but was lacking the low temp cutoff claimed. I suppose that could’ve been my clue to stay away right there.
Before I bought I did some research, Vestwoods makes batteries for a lot of applications, not just some random xdjrbti3924xy co as commonly seen on Amazon flipping junk 100ah batteries cheap then disappearing.
I’ve confirmed low temp protection works on my 250ah ultra model works. So at least that’s something haha.

So in your mind is RoyPow / Epoch junk or possibly a fly by night co because they’re from a China?

I’d certainly like to buy everything made in USA, Canada, Europe, etc but it’s simply cost prohibitive for me.

Yes it would probably be a good idea for me to buy and connect a BMV712 or similar and monitor it that way.

 

[Cmiller]

Yeah I’m well aware it’s a Chinese co… as are seemingly 95% of battery makers.

Yes, I believe pretty much all Lithium batteries in the US come from China or at least have cells from China.

....one of his videos is how I became aware of Vestwoods.

Got it.

So in your mind is RoyPow / Epoch junk or possibly a fly by night co because they’re from a China?

I’d certainly like to buy everything made in USA, Canada, Europe, etc but it’s simply cost prohibitive for me.

I honestly don't know about RoyPow/Epoch, and I wasn't trying to say that all batteries being made by Chinese companies are junk. I apologize if that is how my comment came across! Personally I feel like having a company at least based in the US (even if they get their product made in China) tends to end up being a better experience for the end user. Partially because even on customer support, you will have better communication options due to logistics and/or language barriers etc. I do realize though that there are many US based companies that have absolute crap for customer support, so there is that too....

Something that I have seen quite a bit now is that when a company from the US just tells a Chinese company they want xxV/xxAH battery and then put their own label on it, the results are usually not great long term, when compared to a company that designs their battery from the ground up and gets a Chinese company to then produce that specific product. There are many ways that corners can be cut on a battery! To note a few: low grade cells, "loose" cell matching/grouping, small internal cables, cheap/low quality BMS, cheap voltage based "SOC%" screens... the list goes on. Many of these items don't show up on the "surface", and the battery looks like a fine battery. But 5 years down the road those low grade cells start giving out, or the cheap/low amperage BMS gives out because of strenuous use. Sometimes a cheap battery ends up being more expensive once it needs to be replaced way prematurely! If we look at 3,000-5,000 cycles for a LifePo4 battery, and if we were to cycle that battery once per day (that would be a far undersized battery bank, unless someone is doing TOU, and doesn't want storage for "grid-down") 3,000 cycles/365 pr year = 8.2 years of life. If the battery gives out at 5 years, you might have been further ahead going with Lead Acid batteries instead, and you definitely would have been further ahead spending more on a better quality battery.

Sorry that might be a bit of a bunny trail, but hopefully that makes sense where I'm coming from. I'm not trying to bash companies, I'm just pointing out some of the things that I have seen over the last 5-10 years. (The first LifePo4 batteries that I was involved with, we probably installed ~10 years ago.)

Yes it would probably be a good idea for me to buy and connect a BMV712 or similar and monitor it that way.

That would give you a good perspective of whether that screen is just voltage based. Also, the Victron battery monitors, when set up correctly, are very accurate, even with Lithium batteries! I have one on my personal system, and have set up many of them on other systems with absolutely terrific success!