Charging LiFePO4 battery box in vehicle - How do I limit current?

[pdxfrogdog]

I've built myself a battery box that contains a 100AH LiFePO4 battery, inverter, victron 75/15 MPPT SCC and numerous 12V ports. The purpose was to have a significant amount of portable power that could be easily moved between vehicles as well as used at home during power interruptions. Right now, my charging options are plugging into AC with an external charger or using a solar suitcase connected to the in-box solar controller.

I would like to add in-vehicle charging, but not coming up with a good solution on my own. I have a fuse block mounted behind the front seats, it's connected to the main battery via 8AWG and fused at 40A. Ideally I would like to come up with a solution for plugging my battery box into the fuse block, but it seems like I would need to limit the current in some way as to not exceed the capacity of existing wiring. Looking for thoughts from the electrical gurus here. One thing I was considering is if I could place something like a Victron Orion-Tr 12/24-5 in between the fusebox and the battery box, and route the 24V output into the in-box solar controller.

Thanks in advance for your feedback.

 

[e60ral]

What about just using a 12V LiFePO4 charger?

 

[john61ct]

A DCDC charger, ideally Sterling's BB line.

Get the highest amp one you can afford for future flexibility.

It has the de-rating functionality built in.

 

[pdxfrogdog]

I should have included in my original post that I'm familiar with DCDC chargers, at least the CTEK model. I'm just trying to find a way around them for a few reasons: mainly cost, insufficient wiring gauge from starter battery to house battery location (8 gauge, 15-20ft round trip) and in some cases the lack of programmable charge parameters in DCDC chargers.

Concerning my theoretical question, would taking the output from a 12 to 24v converter (victron makes a number of inexpensive, programmable ones) and feeding that into an SCC that will accept 12 or 24volt panels work? The victron converter below includes a place to tie into a low power on/off switch which could be ignition controlled. The scenario I have in mind:

[Starter battery] ----(13-15v)----> [Victron Orion-Tr 12/24-10] ----(20-30v programmable)----> [Victron 75/15 MPPT] ----(14.0v)----> [House LiFePO4 battery]

Specs on Victron Orion-Tr

Thanks again for your thoughts

 

[Hillbilly Heaven]

Looks sound to me but waiting on the solar experts to weigh in.

 

[john61ct]

The Sterling are nothing like CTEK, fully adjustable.

Only downside is cost.

Without DCDC charger is when you need fatter wiring not thinner.

Some SCs can be used with generic input.

You will have big efficiency losses.

 

[john61ct]

There was an early ACR from Blue Sea that incorporated Current Limiting, comes up on eBay sometimes for $80 or so.

9012 I think?

 

[john61ct]

You really should just put in the fat wiring direct to the alt / starter circuit.

Since your DIY powerpack is portable, just locate it near the firewall keep distance down.

Obviously confirm alt output voltage isn't too high as per mfg specs.

But me, I'd use the BB charger.

Infrastructure usually costs more than the consumable bank.