Second Battery Powered ARB Compressor

[regriff]

I have a 100ah Lithium Ion Phosphate battery (2nd battery) connected to my starter battery through a DCDC charger with a 50 amp max charging current. My ARB single compressor is mounted in close proximity to the 2nd battery. I'd like to wire the compressor to the 2nd battery. The ARB single compressor has a max load of 32 amps and an under load of 25.2 amps.

Given that the max load and under load of the compressor are significantly under the max charging current of the charger, is it safe to assume the compressor will function properly if connected to the 2nd battery and that the draw from the compressor will not drain the 2nd battery if the compressor is only on when the engine is running? Any other pros or cons I'm not considering?

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[Reinen]

The battery specifications should have a Maximum Continuous Discharge Current rating. That's what you can't exceed. However it's typically double that of the Max Charging Current. So if Max Charging is 50A then it can likely discharge at 100A. But don't assume that, double check.

I wouldn't worry about draining the battery as you can recharge it faster than you're discharging it with the 32A compressor. Airing up doesn't take that long.

You'll have to check the manual of your DCtoDC charger about charging the battery while under load. Technically, you can't charge and discharge a battery at the same time. You're effectively charging the battery (less) and powering the compressor with the DCtoDC charger. So see what the charger manual says about that. You may find that it will be easier on your charger if you power the compressor only using the 2nd battery and then recharging it afterwards.

 

[J0E]

Curious why you are mixing battery chemistries? I never mix LA with

In my trailer I have two 12V 100Ah LiFePO4 in series to a pure wave inverter and one LA connected to a cheapo inverter.

I don't think you should have any problem with that size battery. I have four tiny Ryobi 18 V compressors I air up all four 37's from 10 PSI to 32 PSI each with a Lithium-Ion 4.0 Ah Battery. When I get home they read 75% and I through them all on the superCharger. I could easily air up all four with one 6 Ah battery, wouldn't even need my 9 Ah batt.

I'm going dual LA batteries for running my winch when it's pulling > 240 amps. With LA you don't worry about charging while under load, just touch the buttons so the Tazer bumps the RPM to 2,000. My 12K superwinch can pull over 350 amps.

 

[regriff]

Thank you for the reply! I should have included that additional information. Apologies. I am switching out my existing 100ah SOK battery for two smaller batteries that will fit under the cargo area in the back of my JLU. The max charge is 50A and a max discharge of 50A. I will be running two 50ah batteries in parallel to achieve the 100ah's I require. The DCDC charger

I have a 100ah Lithium Ion Phosphate battery (2nd battery) connected to my starter battery through a DCDC charger with a 50 amp max charging current. My ARB single compressor is mounted in close proximity to the 2nd battery. I'd like to wire the compressor to the 2nd battery. The ARB single compressor has a max load of 32 amps and an under load of 25.2 amps.

Given that the max load and under load of the compressor are significantly under the max charging current of the charger, is it safe to assume the compressor will function properly if connected to the 2nd battery and that the draw from the compressor will not drain the 2nd battery if the compressor is only on when the engine is running? Any other pros or cons I'm not considering?

Thank you for the reply! I should have included that additional information. Apologies. I am switching out my existing 100ah LiFePO4 SOK battery for two smaller batteries (both LiFePO4) that will fit under the cargo area in the back of my JLU. The max charge is 50A and a max discharge is 50A. I will be running the two 50ah batteries in parallel to achieve the 100ah's I require. The DCDC charger (Renogy 50 Amp DC-DC Charger) indicates you can charge the battery while under load, but it's generally not recommended.

 

[regriff]

Curious why you are mixing battery chemistries? I never mix LA with

In my trailer I have two 12V 100Ah LiFePO4 in series to a pure wave inverter and one LA connected to a cheapo inverter.

I don't think you should have any problem with that size battery. I have four tiny Ryobi 18 V compressors I air up all four 37's from 10 PSI to 32 PSI each with a Lithium-Ion 4.0 Ah Battery. When I get home they read 75% and I through them all on the superCharger. I could easily air up all four with one 6 Ah battery, wouldn't even need my 9 Ah batt.

I'm going dual LA batteries for running my winch when it's pulling > 240 amps. With LA you don't worry about charging while under load, just touch the buttons so the Tazer bumps the RPM to 2,000. My 12K superwinch can pull over 350 amps.

Thanks for the reply. I have my LA starter battery connected to the DC-DC charger, which is connected to the LiFePO4 batteries. The charger can handle that chemistry. I opted for LiFePO4 for the second battery for weight and capacity when powering camp accessories. Only recently did I consider powering my air compressor with it, as it is only a few inches from the second battery.

 

[GATORB8]

I’d agree, and no reason to waste the gas. I can air up 37s from 14-30 in about 6 minuites with my ARB single. Even pulling 40 amps, that’s 4 AH of usage, which you’ll probably replace before you get to the closest on-ramp.

 

[regriff]

I’d agree, and no reason to waste the gas. I can air up 37s from 14-30 in about 6 minuites with my ARB single. Even pulling 40 amps, that’s 4 AH of usage, which you’ll probably replace before you get to the closest on-ramp.

Thanks for the details. Those are good metrics to consider. 4ah is definitely trivial considering airing up usually is followed with long stretches of highway and battery charging.

 

[GATORB8]

Thanks for the details. Those are good metrics to consider. 4ah is definitely trivial considering airing up usually is followed with long stretches of highway and battery charging.

Highly recommend you buy/build a 4 tire system if you don’t have one. Nice to set and forget it.

Great thing about the DCDC is the power you can pull to refill as long as you have the extra amps to play with.

Edit: Side note, check the recommended charging amps for the battery bms’s, you may want to trim to make it easier to fill them and extend life. My 100s recommend 20 Amp charging each for best fill. Not sure if the Renogy DCDC will adjust like my Renogy Inverter/Charger will.

 

[regriff]

Highly recommend you buy/build a 4 tire system if you don’t have one. Nice to set and forget it.

Great thing about the DCDC is the power you can pull to refill as long as you have the extra amps to play with.

Edit: Side note, check the recommended charging amps for the battery bms’s, you may want to trim to make it easier to fill them and extend life. My 100s recommend 20 Amp charging each for best fill. Not sure if the Renogy DCDC will adjust like my Renogy Inverter/Charger will.

It's definitely on the list of considerations. Living on the east coast I rarely air down unless I'm beach bound. I've been through MD, PA, VA, WV, NC, SC, GA, and FL and have never had a need to air down. Would it have helped a few times? Sure. But sometimes timing and being lazy win the argument. Most of the use my onboard air system receives is either a random visit from a family member needing air in their tire or me helping someone at the gas station being forced to pay for air.

 

[J0E]

Thanks for the reply. I have my LA starter battery connected to the DC-DC charger, which is connected to the LiFePO4 batteries. The charger can handle that chemistry. I opted for LiFePO4 for the second battery for weight and capacity when powering camp accessories. Only recently did I consider powering my air compressor with it, as it is only a few inches from the second battery.

Good reasons. The LiFePO4 has twice the capacity, you can run it from 100% to 80%. LA you can't run below 50% without significantly degrading the battery. On my RV and my EV, I typically keep the battery in the 30% to 80% range for maximum life. Given you don't go camping every day, it's fine to charge it to 100%. We drive the EV every day so I rarely go above 80%.

It's definitely on the list of considerations. Living on the east coast I rarely air down unless I'm beach bound. I've been through MD, PA, VA, WV, NC, SC, GA, and FL and have never had a need to air down. Would it have helped a few times? Sure. But sometimes timing and being lazy win the argument. Most of the use my onboard air system receives is either a random visit from a family member needing air in their tire or me helping someone at the gas station being forced to pay for air.

If you're on a rough road, air down really makes for a better ride. Every weekend I announce, air down for better traction. My wife says, no, air down for better ride.

 

[regriff]

Good reasons. The LiFePO4 has twice the capacity, you can run it from 100% to 80%. LA you can't run below 50% without significantly degrading the battery. On my RV and my EV, I typically keep the battery in the 30% to 80% range for maximum life. Given you don't go camping every day, it's fine to charge it to 100%. We drive the EV every day so I rarely go above 80%.




If you're on a rough road, air down really makes for a better ride. Every weekend I announce, air down for better traction. My wife says, no, air down for better ride.

I definitely do not go camping every day. Wish I could. I do have a kill switch on the starter battery to disconnect the second battery in the rear, but otherwise it would basically be at 100% all the time, except for when I can get out to camp.

I totally get the value of airing down, and am equipped to do so, but alas, I'm mostly too lazy to do it. For sure when I dedicate several hours to rough terrain, I air down. Just not a lot of those trips near my home base. So it's soccer balls and Good Samaritan acts for my air compressor!

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