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H Rosenblatt

Tue, Jun 8, 2004 10:18 PM

I have a dedicated pair of golf cart batteries as a 12 volt starting
battery. I also have four more golf cart batteries connected in
series-parallel as a big 12 volt house battery (and windlass, and thruster,
etc. etc.).

My question, the batteries (I think) are electrically separate. Should I tie
all the 12 volt negative posts together or not? What are the pros and cons.

Thanks.

Harry

I have a dedicated pair of golf cart batteries as a 12 volt starting battery. I also have four more golf cart batteries connected in series-parallel as a big 12 volt house battery (and windlass, and thruster, etc. etc.). My question, the batteries (I think) are electrically separate. Should I tie all the 12 volt negative posts together or not? What are the pros and cons. Thanks. Harry

MM

Mike Maurice

Tue, Jun 8, 2004 11:59 PM

"H Rosenblatt" harryr@mchsi.com
At 06:18 PM 6/8/04 -0400, you wrote:

My question, the batteries (I think) are electrically separate. Should I tie
all the 12 volt negative posts together or not? What are the pros and cons.

You don't have to have the negative posts tied together, UNLESS you want to
use them for the same output usage.
In that case you will have to tie them together, even if only while the
usage is active. Like using the house bank to start the main engine. You
will get all kinds of really weird results if you try to use separate banks
to start the engine(s) and the grounds are not connected. When the grounds
are not connected a return path WILL be found by whatever path can be
created. This may come as quite a surprise, if not a shock, when something
melts without warning.

In other words, it's like having 2 batteries, using either to start an
engine but only one has the ground cable connected to the starter. The
ground connection will come about by whatever means it takes. Through the
cement floor, etc.

Do it right, ground all battery banks to the common ground point.

Mike

Capt. Mike Maurice
Wilsonville, Oregon (Portland).

"H Rosenblatt" <harryr@mchsi.com> At 06:18 PM 6/8/04 -0400, you wrote: >My question, the batteries (I think) are electrically separate. Should I tie >all the 12 volt negative posts together or not? What are the pros and cons. You don't have to have the negative posts tied together, UNLESS you want to use them for the same output usage. In that case you will have to tie them together, even if only while the usage is active. Like using the house bank to start the main engine. You will get all kinds of really weird results if you try to use separate banks to start the engine(s) and the grounds are not connected. When the grounds are not connected a return path WILL be found by whatever path can be created. This may come as quite a surprise, if not a shock, when something melts without warning. In other words, it's like having 2 batteries, using either to start an engine but only one has the ground cable connected to the starter. The ground connection will come about by whatever means it takes. Through the cement floor, etc. Do it right, ground all battery banks to the common ground point. Mike Capt. Mike Maurice Wilsonville, Oregon (Portland).

PB

Peter Bennett

Wed, Jun 9, 2004 12:29 AM

Tuesday, June 8, 2004, 3:18:39 PM, H wrote:

HR> I have a dedicated pair of golf cart batteries as a 12 volt starting
HR> battery. I also have four more golf cart batteries connected in
HR> series-parallel as a big 12 volt house battery (and windlass, and thruster,
HR> etc. etc.).

HR> My question, the batteries (I think) are electrically separate. Should I tie
HR> all the 12 volt negative posts together or not? What are the pros and cons.

HR> Thanks.

HR> Harry

If the two banks are charged by the same charger or alternator, the
negative terminals must be connected together. Even if they are
charged by independent chargers and alternators, the negatives should
be tied together, as (I think) the negative side of most alternators
is connected to the engine, so the two banks will be tied together
there.

Unless you have a really good reason, and are certain the two
systems are 100% isolated from each other, the negative terminals
must be tied together.

--
Peter Bennett, VE7CEI Vancouver, B.C., Canada
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver-webpages.com/van-ps

Tuesday, June 8, 2004, 3:18:39 PM, H wrote: HR> I have a dedicated pair of golf cart batteries as a 12 volt starting HR> battery. I also have four more golf cart batteries connected in HR> series-parallel as a big 12 volt house battery (and windlass, and thruster, HR> etc. etc.). HR> My question, the batteries (I think) are electrically separate. Should I tie HR> all the 12 volt negative posts together or not? What are the pros and cons. HR> Thanks. HR> Harry If the two banks are charged by the same charger or alternator, the negative terminals _must_ be connected together. Even if they are charged by independent chargers and alternators, the negatives should be tied together, as (I think) the negative side of most alternators is connected to the engine, so the two banks will be tied together there. Unless you have a _really_ good reason, and are certain the two systems are 100% isolated from each other, the negative terminals _must_ be tied together. -- Peter Bennett, VE7CEI Vancouver, B.C., Canada GPS and NMEA info: http://vancouver-webpages.com/peter Vancouver Power Squadron: http://vancouver-webpages.com/van-ps

trawlers@lists.trawlering.com

Common Ground for all Batteries?