I made a pack for an ebike from used laptop cells at 36 volts.
Unfortunately I made the pack as 2 seperate serial packs connected in parallel, because I had 2 different capacity cells.
I monitored each serial pack at a midpoint to see if they stayed ballanced.
The 2 packs slowly were unbalanced.
I liked the power for the weight, but you would need alot of cells of the same capacity build in parallel blocks and then built serial with a BMS.
I found the cells warmed up quite a bit under hard use as well.( possibly I needed more cells to reduce the current per cell.
I think a better option is modules from a chevy volt .
They have 24v and 48 v modules at 45 AH
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I hope to find time to use a 48 volt one this summer on my boat.
It has the ability to water cool the pack too.(it has water jackets in the plastic mouldings.
These have a similiar problem for large capacity that you would need a bms for each block, if connected in parallel.
Lithium is more complicated, it seems
From: "oak oak_box@yahoo.com [electricboats]" <electricboats@yahoogroups.com>
To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
Sent: Tuesday, February 6, 2018 4:57 AM
Subject: [Electric Boats] #18650 Batteries
I saw AA Energizer Lithium batteries at the grocery store, and was thinking about the past a year (or two or three?) ago where someone said they were going to put together a bank from a whole bunch of small cells.
It seemed odd that they had plenty of lithium AA batteries, but no chargers. Looking the internet, it kinda' seems like these aren't meant to be recharged - just used as a higher capacity disposable?? Is that really true?
Then, I came across #18650 batteries. Just looking at the internet, they appeared to be very close to the AA battery form factor, but on closer inspection, longer and thicker - but also higher capacity? And higher voltage - these were rated as 3.7V cells, not 1.5 like AA's.
Many of the 18650 batteries were about 3000mAh, but some by Garberiel, seemed reasonably priced (on Amazon), and claimed to be 6000mAh. I haven't done the math yet, but it looked like it would be a cheap way to get a 48V bank quickly, and then as I wanted to put more $$ into it and as the experiments went forward, I could always add more capacity in parallel (which at that point would probably be more expensive than just buying higher capacity cells to begin with).
Anyway, I was curious if anyone has played with these cells? Is the 6000mAh rating likely to be real?
Sounds like it would take about 221 of these to make a 48V, 100Ah battery - is that right?
13 x 3.7=48V 17x6Ah>100Ah, so 221 cells to make up the bank... @ about $15/10, about $330 for the bank??? That sounds way too good to be true. Of course, there would need to be monitors and battery boxes, etc... But does this math sound at all close???
John
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Posted by: Mark F <mark.internet@yahoo.ca>
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