I wanted to comment on 1) below - we have that same concept in mind. We are working on a BMS design that will basically allow cells to be "dropped out" of series, the output run through a boost circuit to maintain steady voltage. There are of course limits to how many can drop out and we are very much at the experimental stage here, but there is some hope :)
Jeff LaCoursiere
s/v Angels Quest
On 4/29/21 10:06 AM, oreillygb@hotmail.com wrote:
First Draft of Schematic. Using Lishen 202Ah. I decided to go with the BMS only actively controlling the charge side of the circuit and opted for passive monitoring on the load side. Using a victron 712 for monitoring and hopefully can connect it to a relay to shut off charge circuit at predetermined voltage. Guys please tell me what I have missed.
Couple of points.
1) Passive Load monitoring. I have decided to go this route as i understand that the load BMS can turn off for 2 reasons, obviously first is if whole bank drops to a lower than 20%SOC and secondly if single cells fail. From my perspective if I have a single cell failure I would rather still be able to use the other 15 cells than have no power. If I let my bank drop to below SOC of 20% that's on me.
2) Want to keep house bank separate for now, mainly as if I have to shut off my 48v bank for low SOC I don't want to have to worry about all my electronics being offline.
3) I want a separate relay to shut off charge current so that I can set this manually. When I come back from a sail i want to be able to top bank up to about a 70% SOC for storage. Then on the day I want to sail I can top it off o 90%
-- Jeff LaCoursiere StratusTalk, Inc. 703 496 4990 x108 815 546 6599 cell
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