Pulled the trigger on the cheapest LiFePO4 batteries anywhere. And I have a question.

[Rohan]

Pulled the trigger on the cheapest LiFePO4 batteries anywhere, these Ecoworthy LiFePO4 12V 100Ah.

https://www.eco-worthy.com/products/...sphate-battery

They are already cheap, and I got 4 of them on Amazon prime day for insanely cheap to replace my AGMs.

So I tried them over the weekend - installation was harder than I expected because the battery posts are flush with the battery instead of raised like they are on AGMs so it didn't line up well with my existing cables which each has a bend to accommodate that raised portion.

And instead of a screw post built into the battery like on AGMs, instead you line up the cable and thread a screw down into it. Problem is, the screws they provided are so freaking short that they can only accommodate one battery cable at a time, but I need to attach more to connect multiple batteries together.

I solved both problems by going to the hardware store, getting longer screws (M8 1.25 metric), and some washers and nuts to act as spacers. I chose zinc instead of steel since zinc has better connectivity (hope that was correct decision, my multimeter seems to show a good connection).

I loved the fact that by swapping out I was removing over 100lbs weight. And for a few days anyway, the batteries worked flawlessly with one exception and I'm wondering if the forum can explain this.

I have been using 4 batteries in 2 battery banks. I rigged it so bank 1 has a single battery that I treat as the starting battery. Bank 2 has the other three batteries which I switch to when I'm going to be anchored for awhile. This arrangement worked well with my AGMs.

When I installed LiFePO4 battery #1, it was reading 13.3v right out of the package, so I decided to test it and see if it would start the motor (Yanmar 29hp). It couldn't. In fact, it basically went dead immediately and read only 5v! I thought maybe it wasn't ready right out of the box, so I charged it up for a couple hours, and then it bounced back and was able to start the engine on it's own. However, after being out on the water for awhile, I tried again, and same problem, it wouldn't start and basically flatlined. I had to use my other 3 batteries on bank 2 to start the motor instead. So it seems like one LiFePO4 can't start the engine by itself unless it's been bumped up a bit from recent charging.

So what gives? My AGMs could start the engine no problem even when they were drained down to 12v. But the LiFePO4 showing 13.3v can't do it? My AGMs had 900 marine cranking amps (These are the AGMs I was using). I don't know the MCA/CCA of the lithium batteries because that's not listed.

Is this a typical problem with LiFePO4s or did I get a bad one?