Duel battery charging
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Mountain Pass
Joined: Sep 2021
Posts: 104
Likes: 56
Duel battery charging
2022 F250 Platinum/Power Stroke: My truck has two batteries. I'll be travelling for few months and want to put a smart charger on the battery (ies). If I connect the charger to only one battery, will it charge both or do I need to put a charger on each battery. The truck will be locked while I am away. Thanks
Hotshot
Joined: Oct 2015
Posts: 19,734
Likes: 12,876
From: Wyoming
As Jim said, connect the charger to either one. That's what I do. My charge is connected to the passenger side battery, only because that one is closest to the wall where the outlet is for the charger to plug into. Be sure to use a quality smart charger. Grandpa's charger may overcharge the batteries.
If you're really ****, you could connect the positive lead from the charger to the positive post of one battery and the negative charger lead to the negative of the other battery. My charger leads won't span that far, so I go to just one battery.
If you're really ****, you could connect the positive lead from the charger to the positive post of one battery and the negative charger lead to the negative of the other battery. My charger leads won't span that far, so I go to just one battery.
6th Gear
Joined: Dec 2020
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Super Moderator
Joined: Dec 2011
Posts: 13,361
Likes: 6,152
If the batteries are DEEPLY discharged, then the choice to charge the batteries as one big battery or separately as individual batteries depends on the amp rating of the charger.
I have a 25 amp charger, and on one truck with dual batteries, for reasons beyond the scope of this response, I tried charging both batteries in parallel (that were deeply discharged) without disconnecting them individually.
It was too much for the charger. The charger is a "smart" charger, so it shut down before cooking to death (but man was it warm to the touch).
I have quick disconnects on each battery, so it was a simple matter to let the charger cool, and charge each battery separately.
The foregoing story is not relevant for simply maintenance charging of otherwise mostly charged up batteries.
However, when the batteries are deeply discharged, one may have to restore each battery separately, depending on the charging current produced by the plug in the wall battery charger.
I have a 25 amp charger, and on one truck with dual batteries, for reasons beyond the scope of this response, I tried charging both batteries in parallel (that were deeply discharged) without disconnecting them individually.
It was too much for the charger. The charger is a "smart" charger, so it shut down before cooking to death (but man was it warm to the touch).
I have quick disconnects on each battery, so it was a simple matter to let the charger cool, and charge each battery separately.
The foregoing story is not relevant for simply maintenance charging of otherwise mostly charged up batteries.
However, when the batteries are deeply discharged, one may have to restore each battery separately, depending on the charging current produced by the plug in the wall battery charger.
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Tuned
Joined: Jul 2005
Posts: 353
Likes: 115
I park mine for extended periods as well and plug it into a Battery Tender brand maintainer, Tender. It is a 2 bank charger/maintainer. I have used a single bank charger on just one battery before and it charged up that battery until the LED was green, I then plugged it into the other battery and that battery showed according to the LED's on the charger that the second battery still needed to be charged. So who knows if they are wired together when shut down.
Super Moderator
Joined: Dec 2011
Posts: 13,361
Likes: 6,152
@wheelerfreak You appear to have a 7.3L gasoline powered truck. The dual battery option in gas trucks is wired differently than the dual battery standard in diesel trucks.
The OP has a diesel truck, where the batteries are in parallel at all times, as both batteries are needed to power the glow plugs prior to start, as well as turn over the high compression diesel engine.
On a gas truck, there are no glow plugs, and the lower compression gas motor is readily started on a single battery. Therefore, a continuous duty separation relay is typically placed between batteries on gas trucks equipped with optional dual batteries, so that any electrical loads powered by the auxiliary battery while the engine is off do not drain the main battery designated for starting the gas engine. Once the engine is running, the relay is engaged to parallel the batteries for charging by the alternator(s) while underway. When the engine is turned off, the batteries are isolated again, by way of the relay.
The diesel trucks, like the OP's, do not have a separation relay, because both batteries are needed prior to starting the engine.
The OP has a diesel truck, where the batteries are in parallel at all times, as both batteries are needed to power the glow plugs prior to start, as well as turn over the high compression diesel engine.
On a gas truck, there are no glow plugs, and the lower compression gas motor is readily started on a single battery. Therefore, a continuous duty separation relay is typically placed between batteries on gas trucks equipped with optional dual batteries, so that any electrical loads powered by the auxiliary battery while the engine is off do not drain the main battery designated for starting the gas engine. Once the engine is running, the relay is engaged to parallel the batteries for charging by the alternator(s) while underway. When the engine is turned off, the batteries are isolated again, by way of the relay.
The diesel trucks, like the OP's, do not have a separation relay, because both batteries are needed prior to starting the engine.
Fleet Mechanic
Joined: Jul 2008
Posts: 1,937
Likes: 1,221
From: Southern Crescent
@wheelerfreak The dual battery option in gas trucks is wired differently than the dual battery standard in diesel trucks.
On a gas truck, there are no glow plugs, and the lower compression gas motor is readily started on a single battery. Therefore, a continuous duty separation relay is typically placed between batteries on gas trucks equipped with optional dual batteries, so that any electrical loads powered by the auxiliary battery while the engine is off do not drain the main battery designated for starting the gas engine. Once the engine is running, the relay is engaged to parallel the batteries for charging by the alternator(s) while underway. When the engine is turned off, the batteries are isolated again, by way of the relay.
On a gas truck, there are no glow plugs, and the lower compression gas motor is readily started on a single battery. Therefore, a continuous duty separation relay is typically placed between batteries on gas trucks equipped with optional dual batteries, so that any electrical loads powered by the auxiliary battery while the engine is off do not drain the main battery designated for starting the gas engine. Once the engine is running, the relay is engaged to parallel the batteries for charging by the alternator(s) while underway. When the engine is turned off, the batteries are isolated again, by way of the relay.
ON EDIT: Based on a schematic provided in another thread, I do not believe this is correct. I do think I'd like it better, though.
Tuned
Joined: Aug 2020
Posts: 314
Likes: 90
@wheelerfreak You appear to have a 7.3L gasoline powered truck. The dual battery option in gas trucks is wired differently than the dual battery standard in diesel trucks.
The OP has a diesel truck, where the batteries are in parallel at all times, as both batteries are needed to power the glow plugs prior to start, as well as turn over the high compression diesel engine.
On a gas truck, there are no glow plugs, and the lower compression gas motor is readily started on a single battery. Therefore, a continuous duty separation relay is typically placed between batteries on gas trucks equipped with optional dual batteries, so that any electrical loads powered by the auxiliary battery while the engine is off do not drain the main battery designated for starting the gas engine. Once the engine is running, the relay is engaged to parallel the batteries for charging by the alternator(s) while underway. When the engine is turned off, the batteries are isolated again, by way of the relay.
The diesel trucks, like the OP's, do not have a separation relay, because both batteries are needed prior to starting the engine.
The OP has a diesel truck, where the batteries are in parallel at all times, as both batteries are needed to power the glow plugs prior to start, as well as turn over the high compression diesel engine.
On a gas truck, there are no glow plugs, and the lower compression gas motor is readily started on a single battery. Therefore, a continuous duty separation relay is typically placed between batteries on gas trucks equipped with optional dual batteries, so that any electrical loads powered by the auxiliary battery while the engine is off do not drain the main battery designated for starting the gas engine. Once the engine is running, the relay is engaged to parallel the batteries for charging by the alternator(s) while underway. When the engine is turned off, the batteries are isolated again, by way of the relay.
The diesel trucks, like the OP's, do not have a separation relay, because both batteries are needed prior to starting the engine.
