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RichardRubright · 23-08-2016, 18:12

Quote:

Originally Posted by Cottontop

6 2v batteries at 1766 amphours each is 21kwh. It doesn't matter how you hook them up or how you think about it, it's 21kwh.

I should have mentioned that the LiFePO4 batteries can be drawn down to 20% SOC, no problem.

I found other Surrette batteries that were 2 Volt 4860 amp hours. The 1766 was a different battery that was a start point. I applied the corrected math formula to the new batteries and that is how I got to 58.2 kwh. My idea here is to make sure I don't drain low which you obviously got, so I looked for more storage in relation to the kwh drain. maybe with recharge in the 3-4 days at anchorage from wind and solar I could push it further, all depending on how much that airco worked at night. I guess what I am saying at this point is maybe with the right set up rather than looking for the 100% solution, 70%-80% is good enough with some dockside recharge time to top back up.

Cottontop · 23-08-2016, 18:12

Quote:

Originally Posted by Cottontop

6 2v batteries at 1766 amphours each is 21kwh. It doesn't matter how you hook them up or how you think about it, it's 21kwh.

Sorry, just realized you had moved on from the 1766 ah batteries to the behemoths.

If you're halfway serious about this, learn about LiFePO4 batteries. Tesla is selling them for about USD700/kwh, I think. If memory serves, they are about half the weight of lead (and smaller).

There is a huge thread on this forum on these batteries.

RichardRubright · 23-08-2016, 18:20

I will look into it and I know the weight savings are huge. Boeing chose them for the 787 Dreamliner. I have to admit, perhaps they are being used incorrectly by people, but lithium scares me a bit. If my charge controller malfunctions and those babies overcharge I would hate to wake up to a fire.

**StuM** · 23-08-2016, 18:22

Quote:

Originally Posted by RichardRubright

I found other Surrette batteries that were 2 Volt 4860 amp hours.

Now you are talking about 260kg per battery or about 1.5 tonnes for the six.

Cottontop · 23-08-2016, 18:24

Quote:

Originally Posted by RichardRubright

I will look into it and I know the weight savings are huge. Boeing chose them for the 787 Dreamliner. I have to admit, perhaps they are being used incorrectly by people, but lithium scares me a bit. If my charge controller malfunctions and those babies overcharge I would hate to wake up to a fire.

The Boeing batteries were a different lithium chemistry. My understanding is LiFePO4 batteries are safe(r). But there are a number of experts on this forum that can answer questions.