Question about battery box charging

[FatherT]

Awesome! Even better is that 4wdsupacentre is just up the road from me !

[Ozian]

Not sure a simple isolator system is the best idea when you’ve got different cranking/auxiliary batteries. The JK has a smart alternator and will vary charging voltage and rate to the primary battery.

A deep cycle auxiliary battery will likely need a different charge pattern to fully charge and get the longest life possible. That’s why I recommended a DC to DC system, and will be installing one of these in my Jeep. I prefer to pay a bit more up front and have a proper system that’s compatible the smart electronics in my JKU.

Cheers,
Ian


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[Nanook]

The JK doesn't have a smart alternator, it's a standard constant output unit with the voltage controlled by the TIPM.

[Ozian]

Originally Posted by Nanook

The JK doesn't have a smart alternator, it's a standard constant output unit with the voltage controlled by the TIPM.

I stand corrected Nanook! Learn something new every day.

Would the TIPM vary the voltage to the cranking battery, and if you hook the secondary battery to the cranking battery wouldn’t you end up with a similar issue as having a true smart alternator? Just curious to understand as electrical systems are not my forte (obviously).

[Nanook]

There are a lot of old posts on here as there has been discussions before about whether or not it's a smart alternator. If you are interested do a search on the topic but it's pretty dry reading

A smart alternator is one that will cut in and out as needed to keep the start battery charged.

The reason it does this is to take load off the engine and theoretically save fuel.

The Wrangler's alternator just slightly varies the charging voltage via the onboard computer but it doesn't fall below 14Vs.

A smart isolator ensures that the start battery doesn't fall below 12.8V ensuring that it will always be able to start the engine.

Yes a deep cycle battery does require a different charge rate which is why you need a DC-DC charger for a smart alternator but with a standard alternator, because the voltage doesn't vary a great deal it's not going to hurt your second battery.

Most owners of smart alternator vehicles get their dealers to change to standard ones via the computer software so they can have a simple set up.

[Ozian]

Great info Jamie. Thanks for the clarification!