Dual Battery Truck; 2/0 cable for 40 amp B2B charger

[jpcjtrtj]

Hi, My Ford F150 just left this earth (blown turbo which warped the engine block @ 125,000 miles); so I replaced it with a Dodge 2500 with the 6.7 Cummins diesel. In the Ford, I ran 2/0 wires from the battery positive and the chassis ground through the frame to the back bumper where I have a dedicated connection to the trailer and the B2B 40 Amp charger. The charger is only on when the trailer lights are on due to the switch on the charger.

The Dodge has 2 batteries (one with a high amperage connection). So, my question is, do I run the positive cable from the positive terminal (through a 60 amp fuse again) and the negative from the frame? or the negative directly from the battery post? The Dodge Tech sheet recommends an engine ground for the high capacity connection, but others say that is a bad practice. The truck has a 220 amp alternator, so, I think there's plenty of amps in the alternator to suck 40 out when driving. I am only running a 40 amp max connection and have a 60 amp fuse on the battery and 50 amp between the charger and battery.

Any thoughts?

jps

 

[FilterGuy]

Hi, My Ford F150 just left this earth (blown turbo which warped the engine block @ 125,000 miles); so I replaced it with a Dodge 2500 with the 6.7 Cummins diesel. In the Ford, I ran 2/0 wires from the battery positive and the chassis ground through the frame to the back bumper where I have a dedicated connection to the trailer and the B2B 40 Amp charger. The charger is only on when the trailer lights are on due to the switch on the charger.

The Dodge has 2 batteries (one with a high amperage connection). So, my question is, do I run the positive cable from the positive terminal (through a 60 amp fuse again) and the negative from the frame? or the negative directly from the battery post? The Dodge Tech sheet recommends an engine ground for the high capacity connection, but others say that is a bad practice. The truck has a 220 amp alternator, so, I think there's plenty of amps in the alternator to suck 40 out when driving. I am only running a 40 amp max connection and have a 60 amp fuse on the battery and 50 amp between the charger and battery.

Any thoughts?

jps

First the Chassis Vs Battery question.

If done properly, a chassis connection can work find.... but the keyword is "properly".

• You need to make sure there are no bolted joints between where you tie to the chassis and where the battery/alternator ties to the chassis. There should only be solid metal or welded metal between the two connections. It may still work with bolted connections, but it becomes a bit of a crap shoot because most modern vehicles will have some type of corrosion protection on the metal parts being bolted together.
• You need to make sure there is no corrosion or paint at the point you tie to the chassis. There needs to be a clean flat surface that the lug sits against.
• You need to make sure the connection at the chassis can't rotate around the bolt/screw due to forces on the cable. The moment the lug starts to move, the integrity of the connection goes into question.
• The point you tie to the chassis is likely to be exposed to the elements. Be sure to use some type of dielectric grease to help prevent corrosion.
• Make sure the connection between the starter battery and the chassis is big enough to handle the 40 extra amps.

Because of all of the above, I like to go directly to the battery.

You may also want to review this:

Wiring the connection at the trailer hitch

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diysolarforum.com

 

[S Davis]

I didn’t want to run the neg through the frame so I ran a 1/0 DLO cable for positive and negative, I made my connections at the auxiliary battery with a 120 amp fuse and then a resettable 120 amp breaker on the positive. I use a 50amp Redarc DC/DC charger to charge two 12 volt 280ah batteries.