3 batteries
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More Turbo
Joined: Jan 2010
Posts: 685
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From: Western NC mountains
3 batteries
Putting 31 batteries in my 88 f350. So ive got a couple of pretty good 65s and was thinking about mounting one behind the cab where my electric/hydro hoist is for my dump. The question is would the 3 rd weaker battery draw too much off of my 31s? The current 2 battey setup and stock alt works fine so far. If it works why change is one thought. Just thinking out loud this morning i guess.
Postmaster
Joined: Feb 2011
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we generally don't advise having mis-matched batteries married together, especially under a heavy load like running your dump unit with the engine off.
if you will be running the dump unit much with the engine off, it would be ideal to isolate the third battery from the starting batteries using a battery isolater, or a heavy-duty relay that looks like a starter solenoid - either way it would be set up so it charges along with the starting batteries but is isolated when the engine is off, allowing the dump unit or whatever else to pull power from it alone and not the starting batteries.
at the end of the day, you can have as many batteries as you have space to mount - my diesel van has 3 batteries and one is huge.
if you will be running the dump unit much with the engine off, it would be ideal to isolate the third battery from the starting batteries using a battery isolater, or a heavy-duty relay that looks like a starter solenoid - either way it would be set up so it charges along with the starting batteries but is isolated when the engine is off, allowing the dump unit or whatever else to pull power from it alone and not the starting batteries.
at the end of the day, you can have as many batteries as you have space to mount - my diesel van has 3 batteries and one is huge.
Laughing Gas
Joined: Feb 2010
Posts: 859
Likes: 2
From: Port Orchard, WA
Isolate for starting. In a perfect world, even if the batteries were different sizes, as long as they had the same voltage it would work fine. However, if there's a voltage difference between the batteries (the real world scenario), some current will flow between the batteries instead of to the starter. It would more than likely be negligible, but it does have the potential to cause you problems when combined with weak batteries, corroded cables, etc etc. If you have one bad battery, it will bring down the charge of the other two significantly.
So the solution is to isolate the two battery systems when not running. Once the truck is running, the alternator becomes the high voltage point in the system. It will charge the lowest voltage battery first, and have the effect of equilibrating the voltage between the three batteries.
So the solution is to isolate the two battery systems when not running. Once the truck is running, the alternator becomes the high voltage point in the system. It will charge the lowest voltage battery first, and have the effect of equilibrating the voltage between the three batteries.
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Dyllan78
6.0L Power Stroke Diesel
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Sep 12, 2010 12:37 PM
