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Old 10-31-2016, 09:41 AM   #1
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Powerwall 2 14 kwh with inverter < $6k

Tesla announced powerwall2 pricing of $5500 for 14kw battery bank with an inverter. Seems to me a factory reconfiguration of the battery pack to 12vdc would provide an ideal house battery for boats and RVs... Obviously the bank could be scaled for smaller load demands... Cool stuff.
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Old 10-31-2016, 10:13 AM   #2
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That price is getting better, but 14 kw is really way too big for a house bank.


14 kw is about 1,200 Ahs at 12v. One of the selling points of a lithium battery system is that it can be routinely discharged to near zero and easily recharged to 100% unlike FLAs.


FLAs really effectively cycle between 50 and 85% whereas lithiums probably can be cycled between 10 and 100%, giving almost three times the effective capacity.


So a 1,200 FLA bank which would be rather big for a boat system is equivalent to a 400 Ah lithium bank. If the cost of a 400 Ah lithium bank is near 1/3 the cost of a 1,200 Ah bank then it is getting much closer to the cost of FLAs.


AGMs supposedly can be discharged deeper than FLAs, but I haven't seen any manufacturer data to back that up. But if true and assuming a 30-90% cycle, the lithium bank is even more competitive with AGMs.


I never thought I would see the day that lithiums would compete for the marine house bank business, but it is getting closer it seems.


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Old 10-31-2016, 11:34 AM   #3
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I never thought I would see the day that lithiums would compete for the marine house bank business, but it is getting closer it seems.

David
I read an article this morning where an automaker was quoted at saying their cost for Lithium Ion batteries is now down to $145/kWh. When I bought my EV under three years ago the cost was reported to be more than double that. Still lots of concerns over battery management and risk of heat/fire, but the rapid progress on resolving these issues is going to continue.
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Old 10-31-2016, 02:43 PM   #4
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I never thought I would see the day that lithiums would compete for the marine house bank business, but it is getting closer it seems.
David
If you have ever been involved is a fire at sea, lithiums would be a last choice to have aboard.
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Old 11-06-2016, 10:41 PM   #5
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What Brooksie said. I don't see the average boat owner adding Class D extinguishers. Will that be in copper, graphite, TEC, or THD, Captain? I think the rec boat application is still well over the horizon.
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Old 11-07-2016, 12:41 AM   #6
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Originally Posted by djmarchand View Post
That price is getting better, but 14 kw is really way too big for a house bank.


14 kw is about 1,200 Ahs at 12v. One of the selling points of a lithium battery system is that it can be routinely discharged to near zero and easily recharged to 100% unlike FLAs.

Sounds about right for me.
I have 8 x 220ah @ 12v = 1760 now
so 880ah @ 24v giving 2 days autonomy.

A couple of days extra wouldn't go astray, I could piss off this puny 3 burner smev gas oven and get in a decent sized electric oven in its place.

Unfortunately, your $5500 there will be more like $20,000 here.
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