T-Pain Is On A Boat: Re: [Electric Boats] Re: two banks

Friday, July 22, 2011

Re: [Electric Boats] Re: two banks

Depends how depleted, and how good the connection is between banks. People do this all the time with jumper cables.

Story time: when I still had my diesel installed, I had the common house battery and separate starter battery setup. One time the house batteries shorted down to 6V through an internal short.

Not knowing this, and not checking first, I put the battery switch to 'both' for a few seconds. The positive post at the starter battery melted through.

I suspect you could buy a 'break before make' A-B battery switch for your setup.

From: acsarfkram <acsarfkram@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Fri, July 22, 2011 8:31:56 AM
Subject: [Electric Boats] Re: two banks

Hi Pat,

Thanks for the response. I have no intention of combining them, I am a proponent of two separate banks as a safety/redundancy matter. The switching issue has been something that I have been thinking about since I installed the two bank setup (three years). The plan was to have some physical restriction to turning both switches on at the same time.

If one bank was depleted and someone turned on the other bank without turning off the depleted bank's switch any idea on how fast would the current would flow to the low SOC bank? Seems it could happen pretty quickly and damage some batteries.

Thanks again,

Mark
Santa Cruz

--- In electricboats@yahoogroups.com, "greenpjs04" <greenpjs@...> wrote:
>
> Hi Mark,
> Yes, you would have one bank at 200 ah. But, be very careful doing that. Make sure both banks are at the same state of charge before turning on both switches. If one bank is fully charged and the other is discharged, a huge amount of current will flow from the charged bank to the other. There is nothing to control how much current flows other than the internal resistance of the batteries and wiring. That is not a good situation. I think most people here would recommend keeping your setup as two separate 100 ah banks. In fact, I can't think of any good reason to combine them. You might want to Google batteries in parallel for more information.
>
> Pat
>
>
> --- In electricboats@yahoogroups.com, "acsarfkram" <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
> >
> > 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
> >
>