Question(s) About Running an Auxiliary Battery:

[Defcon-1]

Alright electrical-gurus, I need some help trying to figure something out in my truck. To preface this, my 923 has an industrial lift-gate installed on the back of the bed. It has been working (has worked) in the past until I removed the aux-battery from the aft-tool-box (to install tooling in there). This disabled the lift-gate operation, until I can reinstall the aux-battery in another location.

Looking over the entire system to get it back in operation, I have some concerns / questions. Maybe I'm just overthinking this, but I want it to be correct / safe, and more specifically, I don't want it damaging the trucks main electrical system. I don't use the lift-gate for anything outside of occasional purposes, so it's not considered high-priority but when I do get it working again I want it to be correct (if not already).

Below are two diagrams I made, one is the Basic-Elec Layout that I have running four 6TL batteries. The pic on the right is how the lift-gate electrical portion is (currently) hooked up to that system (with the exception that originally the converter 24v (+) input line was connected to the #4 battery (+) terminal, since then I moved it to the Kill-Switch so that the 24v/12v converter would not be powered unless the K-S was disengaged, but the aux battery is also removed at this time too so the converter is inop anyway)

My question is, do I need a DC to DC battery charge limiter / battery charger anywhere in the system? In between the converter and the Aux battery? Or is the Aux battery maintained by the constant flow of 13.3v to it? My gut tells me something is not 100% correct in this setup, even though it works. All comments/criticisms welcomed, please help me understand, I'm not too good with electrical, but I can make diagrams I guess lol. How are you guys running a 12v Aux battery in your truck?

Thanks in advance

 

[FullSpecial]

I too started with an inverter but soon decided to go with two systems. 24V for the truck, 12V for the toys.

 

[Defcon-1]

I too started with an inverter but soon decided to go with two systems. 24V for the truck, 12V for the toys.

NGL that's awesome, but that is *way* out of my technical-know-how (and) desire to do something like this lol. Is your 12v alternator connected to it's own 12v battery?

 

[FullSpecial]

NGL that's awesome, but that is *way* out of my technical-know-how (and) desire to do something like this lol. Is your 12v alternator connected to it's own 12v battery?

Correct, five batteries on the truck.

 

[Defcon-1]

Correct, five batteries on the truck.

Where is it in your truck? Just curious. Having a 12v battery being charged on its own system by its own alternator is optimal, but that's going to be too far out of my technical ability. I need to find a way to charge it / maintain it outside of that, (that's even if I need to do that, because I'm not sure if it just being charged by the converter is legit lol).

Shouldn't my 12v battery stop taking a charge after it's full? IE: The amps stop flowing to it from the converter because the battery is topped off? Or, is it not good to have a constant supply of 13.3v to the Aux-battery without it tricking down? (The voltage being reduced to the Aux-battery the closer it gets to being fully charged)?

 

[FullSpecial]

You are somewhat close. While an inverter is not designed to be a charger, a battery should charge and level off depending on the output voltage of the inverter. If the inverter puts out 13.8-14.2V then the battery should charge at about 12.6V, or what we would normally expect. Your liftgate is basically a starter motor that is going to pull more amps than the inverter is designed for. Even though the battery will carry the load the inverter might fail because again, it was not designed to take a deep hit.

 

[Defcon-1]

You are somewhat close. While an inverter is not designed to be a charger, a battery should charge and level off depending on the output voltage of the inverter. If the inverter puts out 13.8-14.2V then the battery should charge at about 12.6V, or what we would normally expect. Your liftgate is basically a starter motor that is going to pull more amps than the inverter is designed for. Even though the battery will carry the load the inverter might fail because again, it was not designed to take a deep hit.

This makes good sense, thank you. The manufacturer of the converter got back to me and said "it is not a stage-charger, it offers power only if needed, and does not push power" but they wouldn't comment further. I'm guessing this means it's different than a regular battery charger that slowly tapers off voltage when it senses the battery is nearing capacity due to amperage draw, that this converter will input 13v+ no matter what when the battery is less than 100%, no voltage taper off.

The gate system came installed when I bought the truck, it was owned/operated by a Police Department in Central NJ, so I'm assuming it was installed professionally, not sure why they didn't buy the 24v version of the lift-gate though lol. When I hook it all back up, I'll have to monitor what's going on amp/v wise. I could also put the converter on it's own power-switch, that I can control when it actually sends power to the aux-battery and not just when the truck is on (it used to be 24/7 because it was hooked directly to the 24v system, but I moved the main (+) input onto the trucks main kill-switch).