How Much

[admiralslater]

I have tried searching the forum, sorry if I missed it.

My question relates to cost of Lithium Batteries on a boat. I've heard lots about the cost but not seen much in numbers.
I will layout basoic boat specs.and if any one can give a very rough estimate that would be good. I understand some gear may not be good with lithium.
I want to replace capacity of 5 type 31 105 amp AGMs
I have 2 banks of solar with about 500 watts of power and controlled with blue sky mppt 2512i units
A brand new Sterling charger
And normal alternators with remote balmar 614 regulators .
Any help is welcomed

[Adelie]

Originally Posted by admiralslater

I have tried searching the forum, sorry if I missed it.

My question relates to cost of Lithium Batteries on a boat. I've heard lots about the cost but not seen much in numbers.
I will layout basoic boat specs.and if any one can give a very rough estimate that would be good. I understand some gear may not be good with lithium.
I want to replace capacity of 5 type 31 105 amp AGMs
I have 2 banks of solar with about 500 watts of power and controlled with blue sky mppt 2512i units
A brand new Sterling charger
And normal alternators with remote balmar 614 regulators .
Any help is welcomed

5-105 a-hr batteries is 505 a-hr total. With best practices you should be using between 30% and 50% of that capacity, lets say 40% which is 202 a-hr.

With Lithium you can use 80%, but let's be a little conservative and say 70%. That means to get the same usable capacity you need 202/0.7 = 289 a-hr of lithium.


If you want one or two batteries for the house bank 12v Mastervolt batteries come in 180 and 360 a-hr sizes. The 360 a-hr is $6340 at West Marine. You could probably find a slightly better deal elsewhere but your are still looking at about $6k for the battery alone.


If you want to build your own bank from non-marine sources then

Shorai - 12v/12a-hr $333 each, so you would need 289/12 = 24 batteries totaling $8200.

Antigravity - 12v/12 a-hr at $194 each, 24 needed totaling $$4656.


Further down the food chain you can pick up the individual cells and assemble the bank from them:

Prismatic EV Battery 3.2v/100 a-hr meaning you need [12v/3.2] * [289a-hr/100a-hr] = [4] * [3]n= 12 batteries at $120ea = $1440. It is not clear to me whether the cells come with BMSs or not, I think not so that would be an added expense.

This source also has 12v batteries Lead Acid Replacement Battery with built in BMSs for $928 so total cost would be about $2780.


Ancillary issues:
Your regulator will need to be limited, most alternators are limited by what the battery will accept so most regulators do no limit the current they will put out. With Lithium the battery/bank would have to be pretty small in order to limit the current, and then that might be damaging to the batteries. With any reasonable sized bank Lithiums will accept so much current that the alternator will fry itself trying to keep up. So you need a regulator that will cap the out put. What you have may work, but you need to find out before the first time you use the alternator to charge.

I don't know how sensitve LiFePos are to charging voltage. You will need to research whether your charger and solar controller will interact well with the BMSs on the batteries. If there is an issue you may need to replace one or both.