T-Pain Is On A Boat: Re: [Electric Boats] Charging batteries in series?

Thursday, January 29, 2015

Re: [Electric Boats] Charging batteries in series?

NiFe chemistry is ideal for fixed off-grid situations. In a zombie apocalypse, I would love the ever-loving snot out of a NiFe battery pack. Lye for the electrolyte can be made onsite from filtering water through wood ash. So these cells can be terminal shorted, or charged until they boil dry, then rebuilt and be good to go. But for a sailboat? I'll keep my 125lb 5kwh lithium pack, thanks. It will be good for more cycles than I'll have my boat, even though I hope to keep her a very long time.

In an off-grid house at resale, the state of the battery pack is a big unknown and will therefore impact the price, like a roof at the end of its life... NiFe iron batteries can just be topped up or have the electrolyte replaced and be good to go. So I doubt they would lose their value with time.

/Jason

On Jan 29, 2015, at 01:14, 'Myles Twete' matwete@comcast.net [electricboats] <electricboats@yahoogroups.com> wrote:

Regarding NiFe batteries, Jeff indicated:
"Wow, this *is* interesting. I'm looking at the spec sheet for the 300Ah cell at 1.2v. So for 48v I would need 40 of them, and at 23.1 lbs per cell, that is close to 900lbs of battery :) Using their pricing page it looks like that pack would cost $11,400. Has anyone used these for EV applications yet? I do love the idea that you can abuse the crap out of them. They claim 11,000 cycles."

Jeff- Such a pack would yield just shy of 15kwh and cost almost 1.5x what my 30kwh of ex-THINK EnerDel lithium modules cost (3x kwh/$). My pack weighs about 650# (3x kwh/#). If you have $11k for batteries, there are lots of options available to you.

As for cycle life, for pleasure boat use, more than a thousand cycles seems like a multi-lifetime concern and value. I mean, how many of us charge our packs more than 3x per month on average? I'd guess that with PbA, I was at about 30 charge cycle per year usage. Now with a larger lithium pack, I probably am looking at 15-20 charge cycles per year. My pack is likely good to 2000 cycles with still 80% capacity after that---i.e. these lithium batteries' won't be seeing that cycle life for the next 100 years and will more likely die from some other fate before then.
I couldn't place a value on 11,000 cycles for a pleasure boat battery pack unless it were also my commute boat or I otherwise got it out every day of the year for 35 years and had to recharge it daily.

-Myles