Re: [electricboats] Draft Schematic-Please give input

We haven't had any bad cells imported yet, knock wood.  We *are* doing our best to burn down our offices with our BMS experiments though :)  Also, our latest batch was all EVE 280AH cells, the Lishen 272AH are apparently "all gone".

Another cool idea we are kicking around... we want our 48v pack to have a 12v tap, so you can use it as your house battery as well as your traction battery.  I'm disappointed in the available downconverters, mostly current limited to 30-60A.  Maybe that would be enough for your house, but it wouldn't do it for mine.

So we want to try to cycle through internal banks of four cells, very quickly (like 10khz), connecting them in turn to the 12v tap.  We believe that this way you will be able to pull the full 1C discharge of the 16 cell pack (280A), but at 12v!  We hope to maintain balance in discharge by cycling very fast, but the BMS should pick up the slack.

Cheers,

Jeff LaCoursiere
s/v Angels Quest
www.aquasparc.com

On 4/29/21 11:34 AM, Carsten via groups.io wrote:

Hi, Jeff

Did you experience single/multiple cell dropouts from Lishen batteries so far ?

On Thursday, 29 April 2021, 23:22:13 GMT+8, Jeff LaCoursiere <jeff@stratustalk.com> wrote:

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

www.aquasparc.com

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

--
Jeff LaCoursiere
s/v Angels Quest
St Thomas USVI

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	Jeff LaCoursiere STRATUSTALK, INC. / CTO Phone: +1 703.496.4990 x108 Mobile: +1 815.546.6599 Email: jeff@stratustalk.com Website: https://www.stratustalk.com Address: One Freedom Square 13th Floor Reston, VA 20190