Replacing the 8Ds

[ktmossman]

I am replacing the original 8D batteries of my J4500. However, with all of the old house electrical systems gone, I'm thinking I probably don't need to stay with 8Ds.  The question is, what size would be more appropriate?

[lostagain]

If you preheat the engine in the winter, either with a diesel heater (Webasto, AquaHot or the like), or with an electric block heater off the generator or plug in at a camp ground, 2 group 31 batteries is really adequate.

[thomasinnv]

this has been debated over and over, kinda like beating a dead horse. In probably 99% of situations 2 group 31 will be more than adequate, but that one time you have an issue that requires cranking the engine more than once or twice for 20 seconds each and you will quickly see the advantage to a larger capacity battery bank. Even most otr trucks that never had all the extra electrical loads like busses have a minimum of three group 31. I ran two group 31 in my old mc8 for a while but that one time I needed to crank it a little longer they quickly fell on their face and my situation went from bad to worse. I went back to 2 8d after that.

All that being said, if you have the ability to connect the house bank to the start bank at the flip of a switch for those emergency situations, I wouldn't hesitate to run with 2 group 31. Just make sure that your battery solenoid and cables between the two banks are up to the task so you don't have a meltdown.

[dtcerrato]

What thomasinnv said...
2 8Ds start, 5 group 31s house & a switch to bring it all together for starting, inverting, & alternator charging. 

[ktmossman]

Thanks for the insight...  I will definitely have plenty of house batteries.  One of the fun parts of this project is that I'm going to use it as a platform to experiment with how far I can push Solar and Lithium batteries on the house side.  While it will be a number of months before I am ready for them, I am currently very intrigued with the potential of using Tesla battery packs. You can store a %@$ ton of power in a pretty small package, that is already engineered for a mobile platform.  (https://hsrmotors.com/products/battery_modules).  Anyway, I will definitely have plenty of house battery capacity to backstop the smaller starting batteries.