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helton333
07-10-2009, 10:56 AM
If I have a separate battery for audio hooked up to my starter battery with a cutoff between, is it still wise to run a ground from the second battery to the engine block? The starter battery is obviously grounded there - but wondering if it would hurt to do this..

btriantos
07-10-2009, 11:25 AM
What do you mean hooked up to the starter battery? If you mean the ground, then that's ok, and it won't hurt it. Optimilly, it would good to have two separate, low gauge grounds going to the block for each battery. Have you fixed your speaker problem yet with any of these changes?

JimN
07-10-2009, 11:25 AM
What happened to the other thread?

You have to have a ground to either the main battery or the block, or the second battery will never charge and it will try to ground itself through anything it's connect to, like the stereo. This will cause the stereo or other accessories to die. If the second battery is near the main one, run the same gauge of cable that is used for the positive lead and wrap it with the main battery's ground lead.

helton333
07-10-2009, 12:25 PM
that's my point - I have it done this way - but will it hurt, as the second post suggests, to go ahead and ground the second battery to the block anyway

JimN
07-10-2009, 12:37 PM
that's my point - I have it done this way - but will it hurt, as the second post suggests, to go ahead and ground the second battery to the block anyway

Which way- directly to the main battery or to the motor? You still haven't indicated where the second battery is located. If you went to the main battery with positive and negative, the original charging lead and ground cable won't be heavy enough to support the current flow of both and voltage drop will occur. This will reduce the charging ability of the alternator, cause hot connections (thermally).

The best way to do this is:

Double the size of the charging lead,
Run cables of the appropriate gauge from the second battery to the main one,
Add a second ground cable of at least the same gauge as the original one.

The single ground cable for the main battery won't handle what you're trying to do, really. Bad grounding isn't tolerated by electronics.

helton333
07-10-2009, 12:46 PM
second battery is a foot from the starter battery- positive to positive post, negative to negative. Will it hurt to ground the second additionally, to the block

helton333
07-10-2009, 12:55 PM
I think I got it. I have 4 gauge wire connecting the two batteries (using the smaller threaded post on the tops of the marine batteries - not the main, larger post) - I can run another ground off the second. So the charging lead is the lead going from the starter battery, positive, to the engines ignition systems? It is a large wire - probably 2 gauge. I need to change it out as well. Maybe I can draw a diagram if this is unclear - I do appreciate your help trying to figure it out.

btriantos
07-10-2009, 01:00 PM
No it wouldn't hurt to ground the second battery to the block. So, it sounds like you are close after you do this, and upgrade the charging cable if needed.

TX.X-30 fan
07-10-2009, 01:54 PM
second battery is a foot from the starter battery- positive to positive post, negative to negative. Will it hurt to ground the second additionally, to the block



I think your done then. Seen as 1 battery by the alt. and boat.


My 2 and third are ground to the starter/house but no positives attached

helton333
07-10-2009, 02:11 PM
is there a bigger charging cable than a 2 gauge, or whatever came in a 1989 prostar? I assume it may be hard to find a bigger one?

btriantos
07-10-2009, 02:23 PM
You're ok with 2 gauge

JimN
07-10-2009, 02:56 PM
I think I got it. I have 4 gauge wire connecting the two batteries (using the smaller threaded post on the tops of the marine batteries - not the main, larger post) - I can run another ground off the second. So the charging lead is the lead going from the starter battery, positive, to the engines ignition systems? It is a large wire - probably 2 gauge. I need to change it out as well. Maybe I can draw a diagram if this is unclear - I do appreciate your help trying to figure it out.

The charging lead goes from the alternator to the battery but in this case, it goes to the battery post on the starter solenoid. that needs to handle the extra current demands. The battery cable is fine.