Is This Battery Pack for Real ($106) ??

m@Robertson

Well-Known Member
Region
USA
The safe chemistry is LiFePo4, or LFP. Ebike companies do not like the bulk.
LiFePo4 also lives a lot longer. My SoGen uses LiFePo4 cells and they are good for 80% to 0% cycles and I can expect a life of 2000 cycles before they drop to 80% of capacity. 3000 if I am not so aggressive on depth of discharge.
But... size matters, and LiFePo4 is not as dense, so it makes for great big packs.
 

harryS

Well-Known Member
This is the inside of a 36V12AH SIlverfish that came on my $700 Ecotric Ebike.Nylon forms to held the cells. Precut nickel end plates. They look fairly regular. Could be robotic, The cells are listed as 2500 mah. I checked out a row of five. all were over 2600 after 2 1/2 years. Much better than the glue and fish paper battery vendors used to use. I replaced this pack with a UPP Silverfish, but I haven't chosen to look inside the UPP pack. Previous UPP packs from 2017 have been pretty sad though,.

I replaced this battery because it got unbalanced, and the unbalanced row dropped down to 2 volts. I changed to a balance BMS, and the pack was staying in balance, but the weak row would still discharge faster, and reduced the capacity to about 8AH. That's no big deal, but I was worried about fire safety. So I replaced it.

PA020255.JPG


For a lark, I took out the bad row. A little battery surgery. I tested those old cells on a dedicated battery tester, The results did not match battery performance. I believe these cells were down to 1800 ma, and would only cjrage to 4.0V, but the tester said they all had over 2600 mah and could fully charge. It's probably because the tester runs the cells at 1/10 of the current levels in an ebike.
PA020258.JPG


Here it is with the suspect cells replaced. New cells were glued to the form. I used NCR 1650B, which are 2500mah tool cells. Maybe not the best choice. I have neat little $60 spot welder I bought off amazon. I haven't put a full ride cycle on this battery yet, but it should work OK.
FA030154-3.JPG


My feelings are that even cheapo ebike packs are fairly well made these days. Otherwise, we hear about big fiores at the battery makers.