Four 185 ah AGM 12 volt batteries wired in parallel would be a 12 volt 740 ah pack if you used half it would give 370 ah
Four 185 ah AGM 12 volt batteries wired in series would be a 48 volt 185 ah pack if you used half it would give 92 ah
To get a 12 volt lithium batter you wire 4 in series for one 12 volt 100 ah battery.
Four of these in parallel (for a total of 16 cells) would give you a 12 volt 400 ah pack if you used 80% that would give 320 ah
All wired in series would give you one 48 volt 100 ah pack, used to 80% that would give you 80 ah
I would guess a lithium 80 ah battery would give more usefully energy then a 92 ah AGM do to high internal resistance of lead batteries.
So at the prices give the lithium is what I would go with. You could not use them with an alternator with out a very good shunting/balancing BMS.
On Apr 18, 2012, at 5:18 PM, william munger <wmunger@programmer.net> wrote:
> After more reading I of course have more questions.
>
> For 800AH in AGM I am looking at 4 US AGM 185 batteries for a total of
> $2000 and a weight of 600lbs. That would give me 280Ah of usable
> battery at 50%DOD and charging back up to 20% while away from dock with
> alternator on inboard diesel. I think it would take me about 3 hrs of
> charging with a 100amp alternator to get from 50% dod to 20% dod (is
> that correct?).
>
> Looking at LIFEPO4 Sinopoly 100Ah batteries it would take 4 in series to
> make 12V, then could use 16 for four banks of 12V for a total of $2160
> and weight of 112lbs. That would produce 640 usable amps at 0% to 80%
> discharge. Or 480 usable amps at 20% to 80% discharge.
>
> My questions are:
>
> What rate of charge will the LIFEPO4 batteries take? (do they require
> float charging as AGM's do)
>
> Can I use a normal 12V 100amp alternator to charge these?
>
> Would it be better to series all 16 for a 48V bank, get a 48V alternator
> for the motor and then use a DC/DC converter to get back down to 12V for
> my house loads?
>
> I have a 4 bank charger designed for AGMs, What type of charger would I
> need to handle LIFEPO4?
>
> My understanding is the LIFEPO4 batteries give you at least 2 times the
> cycle life, way less weight, more usable amps via deeper discharge, no
> self draining, no issues with sitting unused at less then full charge,
> but way more cost. (although in this case less then $200 more for the
> same capacity)
>
> Am I missing something important/costly?
>
> William
>
>
> ------------------------------------
>
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