A couple other factors not mentioned that could influence one’s decision:
· State of charge monitoring
· Charging
· Battery management system
With separate packs, your charging just got more complicated as possibly did your state of charge monitoring and definitely your battery management system would be a lot more expensive with 2 packs. With lead acid, the BMS issue may go away.
-mt
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of James Lambden
Sent: Friday, July 22, 2011 9:32 AM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] two banks
Hi Mark,
The Blue Seas 48 volt switch is rated at 48 volts maximum not 48 volts nominal - which includes charging voltages up to 58 volts.
We use the BEP switches that are rated at 48 volts nominal.
I have had one string of four 4D batteries in parallel with one string of four 8D batteries on Kapowai for 5 years without any issues.
The advantages of operating as one big parallel bank are there is less effect from Peukert's exponent, so the batteries actually act like they are more than twice as large, because each 48 volt battery sees only half the current under operation.
The disadvantage is that one bad cell in one battery will bring down the voltage in the other string of batteries - so its important to monitor the individual battery voltages.
I keep all 8 of my batteries together all of the time to avoid the issue of combining a full battery with a depleted one.
James
Propulsion Marine Products by
Above the Waterline, Ltd.
On Jul 22, 2011, at 8:50 AM, acsarfkram wrote:
Hi Mike,
I thought about using a 1-2-both switch but was not comfortable with the close proximity of the terminals on the switch and the 32 volt max voltage rating (Blue Sea). The single on/off Blue Sea switch that I used is rated at 48 volts. I spoke with someone at Blue Sea and they said that there was enough margin in the rating for my use.
Thanks,
Mark
Santa Cruz
--- In electricboats@yahoogroups.com, "Capt. Mike" <biankablog@...> wrote:
>
> Many boats have a 1, 2, or both battery
> switch for there 12 volt systems. On mine switch 1 was for the starter battery and two was for the house 12 volts (two group 27 gel batteries in parallel ). When I converted to electric I was able eliminate the starter battery and now have each house battery on it's own switch but, I operate in the Both position BTW. It should work the same with two 48 volt banks. Just make sure your wiring and switch can handle the increased current. Also as someone else mentioned if the batteries are not equally charged the higher charged one will drain into the weaker until they are equal.
>
> Capt. Mike
> Sent from on board BIANKA
> http://biankablog.blogspot.com
>
> -----Original Message-----
> From: Dennis Wolfe <dwolfe@...>
> Sender: electricboats@yahoogroups.com
> Date: Fri, 22 Jul 2011 08:48:15
> To: <electricboats@yahoogroups.com>
> Reply-to: electricboats@...: Re: [Electric Boats] two banks
>
> On 7/22/2011 1:29 AM, acsarfkram wrote:
> >
> > My EP system has two separate 48 volt, 100ah battery banks with a
> > common negative. If I switched both on at the same time would I get
> > one bank at 200ah? There is a diagram here;
> > http://groups.yahoo.com/group/electricboats/photos/album/237790029/pic/72846009/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc
> > <http://groups.yahoo.com/group/electricboats/photos/album/237790029/pic/72846009/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc>
> >
> > I've always figured I would fry something if I turned both on but
> > someone mentioned that it would just act as one 48 volt bank with both
> > switches on.
> >
> > Thanks,
> >
> > Mark
> > Santa Cruz
> >
> >
> yes
>
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