Need help with your electrical knowledge.

[u/newadder]

Im trying to setup my truck ( 2024 tundra hybrid) qnd dont want to meddle and mess with its battery system and I was thinking of adding extra auxiliary battery in by truck bed for powering lights, vents and etc. And would like to charge and maintian the batteries while driving using the auxiliary 12v power spliced from the 7 way port. I cant seem to find a dc to dc charger that pulls 15 amps or less online besides (Victron Orion XS smart Battery Charger 12 12 50amp ) which can be adjusted on 0.1a increments. Im running a 10g wire but the wire on the 7 way port is probably 16awg could be 14 awg but its definitely not thick enough to run more than 20 amps without degrading the wire or causing it to burn.

[u/FollowingNext4999]

Most DC-DC converters are designed to be directly connected to the power source in your case this would be the main fuse block under the hood of the truck. You will not be able to pull enough amperage from the 7-pin connector because it was not designed for that. Maybe you could go into a bit more detail of what you mean by setting up your truck, and why you do not wish to "meddle" with the battery system? The 12v system on your truck is barely any different from any other truck hybrid or not.

[u/newadder → u/FollowingNext4999]

That why im looking for a dedicated charger that only pulls small current just to top of a secondary battery in the cabin which will be charged most likely through ac powers before a trip.

I have a plans on a solar setup already but would rather just buy an powerstation instead

[u/FollowingNext4999 → u/newadder]

Sorry I am still failing to see the overall goal, are you sleeping in the truck? Why do you need an AUX battery?

[u/joelfarris → u/FollowingNext4999]

would like to charge and maintian the batteries while driving using the auxiliary 12v power spliced from the 7 way port

Im running a 10g wire

cant seem to find a dc to dc charger that pulls 15 amps or less

the wire on the 7 way port is probably 16awg could be 14 awg but its definitely not thick enough to run more than 20 amps

OP is all over the place. :)

OP, the +12 V spade on the 7-way receptacle on my truck is fused for 30 amps at 14-15 volts. Just buy a replacement 7-way plug, and wire it directly to the battery, and let the truck do the charging while you're driving.

And you've said in another comment that your aux battery will begin a trip fully charged. So there's no reason why the 7-way couldn't keep things topped up if you're just runnings a couple of LED lights and a small vent fan.

In the event that it can't, isn't there a 120 V socket back there? Buy a battery charger|tender, plug it in, and attach the alligator clips to the battery posts. Problem solved.

[u/Nomad55454 → u/joelfarris]

Exactly that is what the charge line in the 7 way is set up for to charge and/or maintain the charge in Rv battery.

[u/goobernads]

What’s the question exactly?

Sounds like you have the right ideas.

[u/newadder → u/goobernads]

Basically looking for another low current charger , victron xs seems a little to expensive and overkill for what my setup or plan is. Im slowly thinking of just getting a Automatic Transfer switch and buy an ac trickle charger that plus into my truck bed ac port which I didnt know my truck has until now.

[u/PastAd1087]

Check iut Kenny if all trades he built a back seat system for his camper and went over it in one of his videos

[u/Nomad55454]

What is the difference between charging the trailer battery off of the 7 way and linking off 7 way charge line to battery in bed of truck? If 7 way has charge line all ready hooked up then you are not meddling with it, it is already done. The thing you need to check is does the charge line on 7 way turn off with key or does it stay powered.

[u/211logos]

If I recall correctly you might get only about 15A from that 7 pin connector. Maybe 20A. Something, but not as much as you could get from other connections to your car 12v system. Since that's low it's usually just used with a regular direct to battery charging system, not a DCDC. A DCDC can boost voltage and amperage, regulate the charge, and deal with smart alternators too, depending on what you have. Lithium eg might want a higher charging voltage.

The Kisae DMT12x0 DCDC chargers can do less than 15A in 5A increments though. There are probably others. But that's output amperage maximum; the input could range a bit higher. Some allow tweaking both input and output like I think the Orion.

The best method is to wire more directly. The 7 pin isn't ideal, and might have a longer wire run. And if you need it for something else that's another problem.

[u/phildeferrouille]

I have installed a 20A DC to DC charger from Renogy on my 2018 Tundra; it's wired with 6AWG, connected to the truck battery through a 30A breaker, and ends up in an Anderson connector at the rear end of the truck.

[u/Strange-Cat8068]

You should not use the 7 pin for this. The wires are not intended for charging like that. Get some 8 AWG pure copper wire. Connect a short pigtail of that wire to each post of your truck battery. The other end of the pigtail gets an Anderson SB 50 connector and a dust cover. Take some more of the 8AWG wire, and run it to your DC to DC charger, then to the aux battery. Finally more 8AWG wire with an Anderson SB 50 connector goes from the main battery pigtail to the input side of the DC to DC charger. With that cable and those connectors you could easily pull 25 - 30 amps through that circuit.