Re: [electricboats] Used EV battery for home or boat use ? BMS ?

Used EV batteries have been available for some years now, though what is changing is the number of these, which certainly will also reduce the price to purchase.  I bought my first ex-EV batteries for my boat around 2014 and over the years have increased the capacity to 30kwh.  For my first 6kwh, I paid about $300/kwh.  Soon after, entire packs became available and cost was around $200/kwh---these were all new, ex-THINK bankruptcy Enerdel batteries.  Fast forward to 2023, I paid just $50/kwh for a used pack (80kmiles) and probably could have paid half of that.

 

As for Nissan batteries, I have no experience, though I know folks in Europe who have swapped out their Enerdel modules for Nissan modules in their THINK cars.  I don't know if they continued to use the Enerdel remote BMS cards or not, but probably did, and if so, Enerdel RLEC cards work.  The problem there is that you'd then need a master controller to communicate via CAN to the RLEC cards.

My boat, Dan Pence's Ginger and my 1920 Milburn EV all use these batteries and RLEC cards for BMS.  Years ago I wrote code so an Arduino Due microcontroller can act as a master BMS controller.

 

My main reason for going this route was the fact that all these battery modules came with the RLEC remote BMS card and so switching to something else would just cost huge amounts of money.  Since then, I also purchased a large stock of RLEC cards and provide them to THINK owners around the world for an affordable price for their cards.

 

On our boats (Ginger and Reach Of Tide), we almost never balance our cells.  Most of the time the RLEC boards are unpowered.  Once every 6-18 months we'll take a look at cell balance across the packs and if more than 40mv spread, leave the BMS connected for 1-5 days to balance the pack.  There is no reason to maintain power to the BMS cards and continuously balance cells any more frequently for a boat that sees use only 1-3x per month with a battery pack that gets charged just 3-4x per year.  Simply powering a BMS card consumes power---about 1watt in the case of these ones.  But in 1 month's time, that's about ¾ kwh per card---about 15kwh in a month for my pack, or about 50%SOC per month!  Sure, I could power them with shore power, but what's the point?  It only adds risk.  Especially when you also learn the details of a BMS implementation.  Turns out that while one thinks that these RLECs bypass specific cells and not others, in reality even cells not intentionally bypassed will see cell bypassing at a 8% duty cycle.  And bypassed cells see that increased to just 75% duty (25% less than one might expect).  Adding this, there's an extra load on the pack even when all cells are balanced.  So it'd be more like a 60% drop in SOC in 1 month if left operating.

 

So, the devil is in the details as regards BMS.  I haven't shopped for BMS cards so don't have recommendation.  I recall that the Orion BMS cards were running about $500 each---you'd need 1 of these for each of your Nissan strings.  These days I'm sure you can do much better for cheaper.

 

If Enerdel RLEC cards were preferred, contact me…I still have a couple hundred of them.  Not turnkey and might not work with the Nissan cell ratings, but at under $100/card, reasonably affordable…add cabling and cost for a master controller.

 

Anyway, it's really a great time to reuse ex-EV batteries!

 

-Myles

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of Carsten via groups.io
Sent: Saturday, June 1, 2024 6:29 PM
To: electricboats@groups.io
Subject: [electricboats] Used EV battery for home or boat use ? BMS ?

 

Hi, all

Soon there will be a flood of used EV batteries available, still having 70 or 80% capacity.
Getting one of these to use in a sailboat however, requires the right controller.

Hvaing a Maxi 87, My old Volvo diesel engine is to be scrapped now, so the replacement (even of weight) would fit well by a used 70-80% Nissan Leaf 1'st gen. battery placed near the keel, and a suitable BMS in the line, to power the motor.

Anyone knows, or having an idea of, which BMS controllers are capable of handling these car batteries if installed in a boat ?

Regards,
Carsten, Denmark