Re: [electricboats] Anyone uses a used EV car battery for powering ?

As usual, your mileage may vary.

Truly, $1700-2000 for a 14kwh pack w/BMS is not a bad deal.

That's just about $120-140/kwh.

And it's true that some of the used EV packs and modules out there are being advertised at too high of a price for what they are worth.

And it's likely true that some of these module & BMS cards have issues.

Still, there are deals out there AND the complexity of using packs made of modules with series strings themselves can be managed.

 

Arguably, land-EV batteries are of the highest quality cells/module/packs designed, built and deployed.  Same story for the BMS systems.  And more and more you can find these, surplus or salvaged for very attractive rates.  Heck, if one has the time and room, you could purchase, then part out a salvaged EV while retaining the battery pack for a very low cost.  I almost did that a couple times with used THINK electrics.

 

I use surplus Enerdel modules designed for use on a 2011 THINK EV for my boat's pack.  I've paid a lot for this pack, particularly for the initial modules.  The last pack expansion added modules at a cost of around $500 ea (3kwh/module), or about $166/kwh for new, very high quality modules including remote BMS cards.

 

Others have used Chevy Volt and other modules.  I would consider adding Chevy Volt modules to my pack (mainly because the earlier ones were 12S as my Enerdel modules are).  They're also a handy size and I'm certain I could adapt Enerdel cell management cards to them (I have a ton of them).  A major factor for me going with lithium on my boat and for using Enerdel THINK modules is the fact that I own (and still drive) a 2011 THINK City electric.   I now have over 70k miles on that car's Enerdel pack and still love it.  Having spares for a car from a bankrupt company is a good feeling.  That was my justification for leaving lead-acid with my boat.

 

Anyway, people have different reasons for doing what they do.

Just do the analysis and be clear about the reasons and the risks.

Be aware that BMS and other electronics draw power and that power can draw a pack down while your boat sits idle at the marina.  One Tesla owner recently related that her Tesla pack loses 3% charge for every 24hours.  It's not the battery's fault, but rather the design choice to value security over energy retention.  That car's pack would brick within 30 days if not plugged in.  Contrast that with my THINK City, which I left unplugged for 5 months and saw nearly no capacity drop.

On my boat, I do not generally plug in and power my BMS.  I see little need to do so regularly given I only charge 1x/2 or 3 months and the power rates are so low with my boat.  When I do plug in and power my BMS cards, there's rarely a surprise---typically I have about 6 cell pairs out of 240 that droop or self-discharge more than the rest.  So there's very little value added in powering my BMS cards 24:7, especially given that 1 bad decision or failed card or poor software could lead to depletion of a cell pair/module/pack before I realize it.

 

Anyway, I'm rambling again.

 

Again, YMMV-

 

-MT

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of Dan Pfeiffer
Sent: Thursday, June 3, 2021 3:56 PM
To: electricboats@groups.io
Subject: Re: [electricboats] Anyone uses a used EV car battery for powering ?

 

I don't have first hand info on this but I do know of one installation on a 13,000lb monohull that just upgraded from Chevy Volt batteries to a bank made from the 280AH LiFePo4 cells that are currently very popular and have been discussed here.  A single 280AH bank replacing a a bank of four of the 48V Volt (apr. 200AH)  The report was that the new battery configuration is performing much better though I don't have any metrics.  But the recommendation was that the Chevy Volt batteries were not worth considering with better options now available at competitive costs. 

A 48V 280AH bank from the Eve or LeiShen cells will cost between $1700 and $2000 USD including a BMS (like a Daly).  A similar sized bank from Chevy Volt batteries will be about $500 for each 48V 50AH unit.  So that's about $3000 for the same capacity but the BMS will be more complicated I think.  And those are not new cells but probably have a lot of life left and might be a good interim solution if you can find a good deal on 2 or 3 of them.  They are more easily scaled with the 48V units.  But they run at a slightly lower voltage than the LifePo4 cells I think. 

Dan Pfeiffer

 

On 2021-06-03 10:31 am, Carsten via groups.io wrote:

Scouting for a useful and low-cost battery bank, I would like to know - are some of you using a used EV car battery (50-80% remaining) for powering your boat ?

 

If so, how ?

 

I would like to wait to spend BIG bucks for a large new bank, so this might be an alternative, until the battery technology has come up at a higher level.

 

Cheers,

Carsten