Custom Battery Cables

[diesel_driver]

I've just replaced my original OEM batteries (Oct. 2003 purchase, and they were still working fine), and I plan on relocating at least the passenger side battery, along with the battery temp sensor. In researching what size cable to use, I've come up with the following: Starter draw is 700 amps (max), and grid heater is around 90 amps. Figuring a small margin of over-capacity, I am building the cables to handle 1000 amps, using 3/0 cable. I could jump that to 1200 amps by stepping the wire size up to 4/0 cable. Both those sizes would allow 100% duty cycle through the cables, which would never happen. It's really just the starter that raises the requirements so high, but it is necessary to calculate for the highest draw.

I know that there are some engineers on this site, and maybe someone could chime in if I'm off base on my choice?

I would really like to relocate the driver side battery as well. I could use the space for a double stack transmission cooler/fan assembly. I am going to remove the heat exchanger for the auto trans and replace it with this:

I know that the air to water heat exchanger is more efficient than a cooler/fan, but I really want to remove the chance of cross contamination the heat exchanger presents. I would like to mount this assembly somewhere near the driver side battery location.

I have searched this site for battery relocation threads, and know that there are quite a few members that don't like the idea. I'm going to do the relocation, I could always revert back if it causes any problems. I won't modify any existing cables or wiring, so switching back wouldn't be a problem. The battery or batteries will be mounted inside a bed mounted tool box, along with a couple of other items.

Just a little chuckle for everyone; I got a quote for the OEM drivers side positive battery cable. $1,055.00 Got to love dealer mark-up!

 

[phantomusa]

I can make cables cheaper then that dealer $1,054.00 no markup and free shipping LOL

 

[sag2]

There should be lots of nice hot air under the hood to cool your transmission fluid. I think your trying to fix something that isn't broken.

 

[diesel_driver]

There should be lots of nice hot air under the hood to cool your transmission fluid. I think your trying to fix something that isn't broken.

I hear that. However, I would like to eliminate potential trouble spots.

After an incident last year, miles away from anyone and a large towing bill, near trouble free is what I'm after. Luckily, I still had cell service. Trying to direct the tow to our location was quite a challenge. My wife and I were traveling alone, and the nearest tow was almost two hours out. We took a gamble that the large 2-wheel drive tow truck could get us out, and they did. If a 4-wheel drive tow had been needed, the closest one was about 4 plus hours out. We were on gravel and dirt roads the whole trip, looking at property, and never thought we would need any help.

I know that the heat exchangers have for the most part been pretty reliable, but some do fail. If I eliminate that, I also eliminate a couple of hard to access small rubber hoses.

As far as heat from the engine compartment, that is pretty easy to minimize.

I would be interested to know what changes were made to the 48RE transmission that allowed the elimination of the heat exchangers in the later trucks. I can't recall what year they were no longer used.

 

[Bob4x4]

The only reason to relocate the batteries that makes much sense is to improve weight distribution.The failure rate for the heat exchanger is very low.I have been working on CTD's since their inception in a fairly hi volume shop with a big diesel following.First hand I can remember seeing 3 failures since the early recall versions.I travel far off the beaten path in my trucks and the cooler is not one of my concerns.

 

[cerberusiam]

The 48RE's all used a heat exchanger. Not sure on the newer transmissions if they used coolant or just 2 coolers, but, they are a lot different in how they work also.

There is a large cooler between the CAC and the radiator that will handle the cooling when moving. If you remove the heat exchanger then this one needs to be there for slow speed driving and idling in traffic. Best place to mount it is under the bed on the driver side where it can get some air flow and be out of the engine area when hot. There is not enough air flow under the hood when sitting or moving less than 20 mph to do a thermostated cooler any good there, if will just get hotter and hotter. Room there is also a premium so cramming one more heat generating thing under the hood that will make it worse when it is needed is not good engineering.

Battery temp sensor is under the driver side battery and charging is fed by the cross over cable. If you move the driver side battery you need to move the alternator output wire to the driver side battery now you have to run a cross over cable from the rear battery to the front to link them for charging. Grid heaters drive off the passenger side battery and the starter off the drive side for a reason, they are huge amp draws and off one battery they will suck it down fast. Since that battery also supplies voltage for the ECU, and it needs a good clean source to drive the injectors at 22 volts or starting and running go south in a hurry, you are either routing much larger wiring harnesses back and forth between batteries and large amp draws to make up for the cables being 4 or 5 times longer than normal and split the load.

Chassis grounds are run tot he negative battery cable for a reason, you would have to run them back to batteries to provide the protection in the OE system. The gain just isn't there when you start moving the stuff around that far and definitely not for trying to put a trans cooler under the hood. It is hard enough to keep the cables and connections clean and tight with what is there let alone remoting the power sources and still provide the same as designed.

With a stock transmission you best bet is a completely divorced system from the OE. Pretty easy to source an oil rated pump that will circulate it thru the fan backed cooler. You can use the thermostat to trigger both the pump and the fan, tap the pan on both sides for feed\return and let the OE system handle the cooling\lube circuit it is designed for.

 

[diesel_driver]

Thanks for the input guys.

I really want the batteries out of the engine compartment, but if I find the number and complexity of connections to be to great, then I will abandon the project.

 

[softailer]

I am also interested in a similar conversion. I did have the misfortune of the heat exchanger failure you discussed. I had the transmission rebuilt by a reputable builder and the stock heat exchanger replaced. The transmission had just finished being rebuilt when this occurred. I too am thinking this conversion would be insurance against this re-ocurrance. Thinking of mounting mine under the bed... for increased cooling efficiency. What cooler are you considering using???

 

[Bob4x4]

I am also interested in a similar conversion. I did have the misfortune of the heat exchanger failure you discussed. I had the transmission rebuilt by a reputable builder and the stock heat exchanger replaced. The transmission had just finished being rebuilt when this occurred. I too am thinking this conversion would be insurance against this re-ocurrance. Thinking of mounting mine under the bed... for increased cooling efficiency. What cooler are you considering using???

Did you check to see if your truck had the cooler recall?

 

[diesel_driver]

I am also interested in a similar conversion. I did have the misfortune of the heat exchanger failure you discussed. I had the transmission rebuilt by a reputable builder and the stock heat exchanger replaced. The transmission had just finished being rebuilt when this occurred. I too am thinking this conversion would be insurance against this re-ocurrance. Thinking of mounting mine under the bed... for increased cooling efficiency. What cooler are you considering using???

Sorry, I missed responding to your question about cooler choice. I'm looking to use a Derale 15870. It measures 13" x 13" x 6", and dissipates 67,000 BTU's per hour. That's double the cooling that most who do this mod are achieving. It comes with a mounted fan, but no other components. BD sells a complete kit, with wiring and thermo switch, as well as hose, fittings, and a universal mounting kit. It is rated at about 33,000 BTU's.

 

[JKosten]

When I had my transmission rebuilt at 230k miles I added a Derale cooler and 25 micron spin on filter to the trans cooling system. It has a fan that kicks on at 185 deg. I now have over 30k on this setup and every engine oil change, I also replace the spin on filter for transmission.

Daily driving with no load I average 130-150 deg. Towing in the flats is stays around 160-175. Pulling hills it will see 180ish. The fan normally only comes on when I slow down in traffic after a climbing a hill or pulling into a fuel station.

During the install