Anyone using a Dc to Dc charger for a second battery?

[bsteg7]

I think "ignition" refers to the old school keyed ignition switch position. When you stuck the key in and tuned it one or two positions the 'ignition' circuit was on, including ACC. I don't think it is referring to an 'engine running' circuit. When the ignition circuit is on it allows you to do things that drain the battery like radio, power windows, AC, sunroof etc. The assumption is that you will either start the engine or drain the battery. I have used the 5th wire in the aux group labeled ignition and it behaves in this manner. Push the start button without your foot on the brake and the 'ignition' circuit is live along with the radio, etc. but the engine is not running.

There is an ignition wire in the dash that feeds the head unit. There are 'ignition' adapters that you can use that work great if you do not have the factory aux switch option.

https://www.quadratec.com/p/quadratec/12-volt-power-adapter-jeep-wrangler-jl

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[teamblkdog]

What's wrong with using a dc to dc charger for second, I mean third battery in the bed to take the load off the alternator? I dont have the upgraded alternator. How is that inefficient? And if I want to add solar panels down the road it seems like the better route.

I have this setup using a Redarc BCDC1240D charging a 100 Ah 12V LiFePO4 Deep Cycle Battery through the alternator while driving or through (2) 100W solar panels when parked in sun. Works great.

 

[Radio Guy]

A DC to DC inverter seems ok for charging a battery at the rear of the truck since that battery will never charge the same as up front using an isolator due to the long cable lengths and loss to the rear. Slight problem is the DC converter is not 100% efficient and will take more power to charge the battery than the battery gets during charging.

I would limit power to the DC charging converter except when the engine is running or you could possibly use a battery isolator off the alternator with one side going to the existing battery(s) and the other to the input of the DC converter so its only powered when the alternator is running. In all cases I would put the DC converter right at the remote battery so its sensing circuits will charge properly.

 

[bsteg7]

I would limit power to the DC charging converter except when the engine is running or you could possibly use a battery isolator off the alternator with one side going to the existing battery(s) and the other to the input of the DC converter so its only powered when the alternator is running. In all cases I would put the DC converter right at the remote battery so its sensing circuits will charge properly.

Question: How would a battery isolator determine a smart alternator is running? Smart alternators do not have a consistent output. Often the output is off ie when accelerating.

Question: Where do you find this 'engine running' wire?

For me I am just going to connect the DC to DC charger smart alternator lead to the standard, old fashioned, ignition (ACC) circuit as the instructions clarify. I will note that if I turn the ignition on without starting the engine the radio, power windows, air conditioner and my DC to DC charger will all be draining the starter battery with no alternator on.

 

[Radio Guy]

A battery isolator at the alternator will only send power to the DC converter when the vehicle is running and the alternator is outputting power. When the vehicle is off the battery isolator prevents any power being taken from the main battery to the DC converter.

Question: How would a battery isolator determine a smart alternator is running? Smart alternators do not have a consistent output. Often the output is off ie when accelerating.

Question: Where do you find this 'engine running' wire?

For me I am just going to connect the DC to DC charger smart alternator lead to the standard, old fashioned, ignition (ACC) circuit as the instructions clarify. I will note that if I turn the ignition on without starting the engine the radio, power windows, air conditioner and my DC to DC charger will all be draining the starter battery with no alternator on.

 

[SelfmodJT]

So I've been doing more research on what battery to purchase for this set up. So it seems like the optimum temperture for lifepo4 batteries are above 32 degrees. They say not to charge them or discharge them below 32 degrees. The only ones I see that wont have the temperature issues are Relion batteries. Look up what they cost for a 200ah battery, lol. I'm budgeting no more then 1200 for a battery. I was going to have the accessory battery in my truck bed but now idk because it will def drop below 32 degrees. I know most people dont go camping in the winter and you can pull out the battery and leave it in your garage but I was planning to do a cross country trip and I will be in each state 1 to 2 weeks. Have you guys considered the temperature variable for this setup?

 

[Radio Guy]

What's the problem when they get cold? Are the AH specs reduced and you can use it with less capacity or is it an absolute no and the battery will be damaged, etc?

So I've been doing more research on what battery to purchase for this set up. So it seems like the optimum temperture for lifepo4 batteries are above 32 degrees. They say not to charge them or discharge them below 32 degrees. The only ones I see that wont have the temperature issues are Relion batteries. Look up what they cost for a 200ah battery, lol. I'm budgeting no more then 1200 for a battery. I was going to have the accessory battery in my truck bed but now idk because it will def drop below 32 degrees. I know most people dont go camping in the winter and you can pull out the battery and leave it in your garage but I was planning to do a cross country trip and I will be in each state 1 to 2 weeks. Have you guys considered the temperature variable for this setup?

 

[SelfmodJT]

What's the problem when they get cold? Are the AH specs reduced and you can use it with less capacity or is it an absolute no and the battery will be damaged, etc?

Supposedly, most nice batteries will have a bms temperture shutoff protection. I know the battery under the hood will eventually get heat from the engine but a battery in the bed will not. Yes, the battery will potentially be damaged and i doubt warranty will cover it.

 

[bsteg7]

Supposedly, most nice batteries will have a bms temperture shutoff protection. I know the battery under the hood will eventually get heat from the engine but a battery in the bed will not. Yes, the battery will potentially be damaged and i doubt warranty will cover it.

The cheapies dont have low temp cutoff. Chances are slim I would need to charge below freezing in California but just in case I went with the SOK because they do include low temp cutoff. Great low cost battery!

 

[SelfmodJT]

I guess you dont need a fridge at 32 degrees

The cheapies dont have low temp cutoff. Chances are slim I would need to charge below freezing in California but just in case I went with the SOK because they do include low temp cutoff. Great low cost battery!

Lol, actually watched that video last night. I guess it doesnt matter if your fridge doesnt work when its below 32 degress outside.

 

[SelfmodJT]

I guess you dont need a fridge at 32 degrees

Lol, actually watched that video last night. I guess it doesnt matter if your fridge doesnt work when its below 32 degress outside.

I think I'm going with the sok battery as well. Hows it working for you? I'm also going to make a smaller 50ah battery system under the backseat for a backup in cold weather. That should be sufficient during cold weather.

 

[bsteg7]

So I did some research on that charger, what is the best connection for that blue wire for ignition that senses the voltage? Getting different answers.

I wouldn't use the Renogy. There are issues. This video shows the ignition lead you are asking about. The manual says nothing about voltage sense on this lead. This 50A charger only puts out 15A when in dual mode. My brother runs a separate Victron DC to DC from the alternator and Victron Solar charge controller and that's a nice setup. The Victron stuff has BT and a nice app. Also the devices 'network' to each other.

 

[Oak]

Redarc is 10% off for labor day - getting ready to install my bcdc and you can get battleborn 100 amp lithium battery at $799 from $950 right now. no tax or shipping.

https://battlebornbatteries.com/product/12v-lifepo4-deep-cycle-battery/

 

[Donkey Fluffer]

I've been running the Renogy 50amp model for over a year now. Also have 200 watts of solar going into the DC to DC charger. My fridge has run the entire year through all 4 seasons (Virginia).

 

[LaterGator]

I've been running the Renogy 50amp model for over a year now. Also have 200 watts of solar going into the DC to DC charger. My fridge has run the entire year through all 4 seasons (Virginia).

Where did you tap in for the ignition sensing wire?

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