opinion on 12v to 12v battery charger

[madmaths]

HI! any one is using a 12v to 12v battery charger? this summer we plan a road trip and I would like to charge a small battery bank I made in a jerry can ( 4 x 12v 18ah in parallel ) so I would like to use the lighter plug in my truck and plus a 12v to 12v battery charger to charge it will we drive. I think I will also use it in my popup trailer to charge my class 31 agm battery. my car is a 2017 honda hrv and my jeep a 2015 rubicon I think with a charger like this my BCM in my 2 vehicle will be safe like this.
what are you thinking?? opinion? thanks
here a example of a 12v to 12v charger:

here my jerry battery bank :

 

[DiploStrat]

Spend some quality time researching this forum - this has been discussed into the ground.

-- Volts matter: for many people a B2B is a cure for which there is no disease.
-- Amps matter: most cigarette lighters can't produce much current.

 

[jonyjoe101]

to charge from your cigarette lighter while the car is running you dont even need a charger. Your jerry can is something similar to those 12 volt jump packs, the 12 volt jump packs are charged straight from the cigarette adapter. Just connect one of those double male cigarette adapters from the car to your jerry can. But your cigarette lighter maxes out at 15 amps, which is the max it will charge your jerry can, and make sure your cigarette male plug is high quality, the cheaper ones melt if you run 15 amps constant.

Those small 12 volt dc to dc chargers are more trickle chargers than anything else, the good ones max out at 5 amps, most are like 2 amps. Even driving it will take forever to charge any battery.

Just make sure you unplug the charger when you stop driving are it will drain your start battery.

You dont have to worry about damaging or overcharging your jerry can batteries. 12 volt lead acid battery when they get full wont accept any more amps. Only way to overcharge/vent it is to force it to accept more amps by charging it with more than 15 volts. Your car alternator will max out at about 14.4 volts. Thats why you dont really need a charger.

 

[madmaths]

Spend some quality time researching this forum - this has been discussed into the ground.

-- Volts matter: for many people a B2B is a cure for which there is no disease.
-- Amps matter: most cigarette lighters can't produce much current.

I did my search and finish it with more question I have before I start lol!!
a lot a tread I found they don't recommend hooking directly a second battery ( like my setup ) without a charger... that why I was asking about this 12 to 12v battery charger

 

[comptiger5000]

I do like the 12V to 12V charger idea. IMO, it's better than just paralleling the battery to your existing system (as long as the 12V charger can move enough current for your needs), as non-identical batteries in parallel don't always charge as nicely as they could.

Plus, for those of us with temperature compensated alternators (my Jeep has a temp sensor in the battery tray and adjusts charging voltage accordingly), the charger can do a better job of getting the second battery the power it needs for a proper charge. In my case, when it's cold outside, I've seen 15+ volts to the battery. In the summer once the engine bay is heat soaked, it can be as low as 13.7 or so. Especially in the winter, if the battery being charged is warmer than the one in the engine bay, that's not ideal.

Not sure how many of those chargers are high power, but I know the Xantex Echo Charge (and probably a few others) will do 15A. IMO, that's good for an install in a trailer to charge the battery from the +12V line in the 7 pin connector (you'll have to run separate wiring if you need faster charging).

 

[DiploStrat]

I did my search and finish it with more question I have before I start lol!!
a lot a tread I found they don't recommend hooking directly a second battery ( like my setup ) without a charger... that why I was asking about this 12 to 12v battery charger

A B2B is very useful if your charge source does not produce the correct voltage for your battery. Classic case - Toyota that runs at 13.9v and most deep cycle lead acid batteries which want about 14.4v at 20C/70F. All B2B can boost voltage and some can drop it. All of them trade amps to get volts so they generally have a lower output.

If, on the other hand, your charge source produces the correct voltage for your battery, then a B2B won't do you any good.

Most multi-pin trailer plugs have very small wiring and will not produce a very high charge rate.

 

[madmaths]

https://www.caravanworld.com.au/features/1509/dc-dc-battery-chargers-explained

Sent from my SM-G925W8 using Tapatalk