There were two points to putting the packs in parallel:
1) My Torqeedo is rated to 4800W, which would take at least 4 of the 20AH packs (with a max spec'd output of 30A) in parallel to be able to fully drive (if only for a short burst).
2) Peukert effect - Not sure how much of a factor this is for Lithium, but for my previous FLA packs, they did MUCH better if they were drained at a lower power level.
If I ended up getting 4 packs, I could put 3 in parallel for primary power, and use the 4th as my "backup" pack. With 3 in parallel, if I pulled 5A from each pack, I'd get 700W (enough to get me 3.5-4mph on my current boat), and might be able to expect 2-3 hours of run time without excessively wearing the batteries.
Just using battery switches, if I pull 15A at a time from each battery, I'm guessing I might get 30-45 min before I would need to switch to the next battery.
$500-600 per pack is pricey, but at least there's a chance of being able to get multiple packs to explore how well they do in parallel, or not, and capacity can be added over time.
Going "all in" with Thunderstruck CALB Lithium batteries - I would need 16 batteries for a 48V system (right???). For a 70AH bank, that would be about $1600, but would require a bunch of wiring, a bms, and a charger.
The electric bike option gives me a 20AH bank in a small, fully contained package with a charger for about $500.
Ultimately, the full bank is probably a much better option - but difficult to swallow for "experimenting", and having no idea how it's really going to work out.
From: "cpcanoesailor@yahoo.ca [electricboats]" <electricboats@yahoogroups.com>
To: electricboats@yahoogroups.com
Sent: Monday, January 23, 2017 9:23 AM
Subject: [Electric Boats] Re: Electric Bike batteries, and parallel connection?
king, from what I've read about Lithium cells and packs, many are designed to provide high current compared to AH capacity, sometimes 3C or more, so for a 20AH pack, up to 60A. For a 20AH pack, I would expect 15 or 16AH of usable capacity. The maximum draw would depend more on the BMS and pack wiring. Check the specs.
As to using multiple packs, the easiest solution IMO is to use a battery switch which connects only one pack at a time. Then the packs won't affect each other.
As to using multiple packs, the easiest solution IMO is to use a battery switch which connects only one pack at a time. Then the packs won't affect each other.
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Posted by: oak <oak_box@yahoo.com>
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