Some Questions About Which Redarc B2B To Purchase

[chet6.7]

I am reading the specs on these two chargers,
https://www.redarc.com.au/in-vehicle-battery-charger-40a,and,
https://www.redarc.com.au/40ain-vehicle-battery-chargermppt-regulator-low-voltage-version
Does a 2014 Ram truck have an "ECU-controlled variable voltage alternator?" If it does,is the REDARC BCDC1240-LV best choice?

That is correct - the right B2B will charge from both solar and the starter battery, the CTEK gives you 20A, the REDARC 40A. The biggest drawback to a B2B is that they are one way devices; a solar or shore charger connected to the camper battery will not charge the starter battery and you cannot use the camper battery to jump start yourself without some extra effort. (And one of the reasons that bi directional charging is so slick is that it greatly reduces the chance that you will have to self jump!)

Would you recommend the Blue Sea ACR over the https://www.redarc.com.au/dual-sense-smart-start-sbi-12v-100a. I am leaning toward the Blue Sea ACR for the self jumping capability.

What is the best way to charge the starting batteries and the Northstar batteries in the battery bank from shore power? Will a battery charger connected to the starting batteries charge the battery bank as well,or will it be necessary to charge the battery bank separately?
I am not an over-lander,I travel between two locations,and make day trips from home base.Shore power will be the main charging source as my day trips will not be long enough to fully charge the batteries.
I do not have solar yet,and if/when I get SP it will be one panel,the truck is under a carport at home,so again, shore power.
Thanks.

 

[john61ct]

Best ACR on the planet: ​ https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

And for DC-DC, best is Sterling's BB series, apparently Charles has a 180A version coming out soon.

Fully custom adjustable setpoints so work with any batt chemistry including LFP.

Also control over amps to protect the upstream power source.

 

[martnH]

The redarc BCDC is only 40A
It's only a baby.

Your alternator can probably output 150 Amps....

I will use a simple relay style system than these amature BCDCs

Unless you get a commercial BCDC rated at 100amps and that would be fast charging

Sent from my LG-H870DS using Tapatalk

 

[dwh]

I am reading the specs on these two chargers,
https://www.redarc.com.au/in-vehicle-battery-charger-40a,and,
https://www.redarc.com.au/40ain-vehicle-battery-chargermppt-regulator-low-voltage-version
Does a 2014 Ram truck have an "ECU-controlled variable voltage alternator?" If it does,is the REDARC BCDC1240-LV best choice?

Either one will work. I doubt you'd need the LV version.

Would you recommend the Blue Sea ACR over the https://www.redarc.com.au/dual-sense-smart-start-sbi-12v-100a. I am leaning toward the Blue Sea ACR for the self jumping capability.

Yes. Because...see next section...

What is the best way to charge the starting batteries and the Northstar batteries in the battery bank from shore power? Will a battery charger connected to the starting batteries charge the battery bank as well,or will it be necessary to charge the battery bank separately?

The Redarc will have an ignition wire so it's turned off when the ignition switch is off. The ACR is on all the time.

So if you hook a battery charger to the engine battery when the truck is parked, the Redarc won't charge the house battery.

But the ACR will. When it senses a rising voltage on one side, it will tie the batteries so both get charged.

For that matter, you could hook both the battery charger and the solar to either battery, and the dual-sensing ACR will tie the batteries whenever charging happens from any source and both will get charged.

 

[dwh]

Your alternator can probably output 150 Amps....

...but your batteries probably can't accept that many amps.

A) Only a large lead-acid battery bank will allow that many amps to flow.

B) And even then, only for a while. Half-hour, hour, maybe an hour and a half. Then the battery voltage and resistance will rise and start choking off the amp flow.

C) But even if you had a couple of 100ah LiFePo4 batteries that could actually allow up to 200a to flow and max out the 150a alternator - the alternator would overheat.


Let's say a 150a alternator. That's the "max cold" output rating. Most also have a "max hot" rating which is typically 80% of max cold. And it will get hot. So really, it's a 120a (hot, continuous) alternator.

Which also has to run the truck. That alone can be anywhere up to 80a - 100a depending on conditions. Which leaves 20a - 40a capacity available to charge an aux battery.

Hence the 20a CTEK, the 25a or 40a Redarc, the 15a, 30a or 50a Sterlings.

100a @ 14v is 1400w. The 40a Redarc draws 600w.

 

[DiploStrat]

...
Would you recommend the Blue Sea ACR over the https://www.redarc.com.au/dual-sense-smart-start-sbi-12v-100a. I am leaning toward the Blue Sea ACR for the self jumping capability.
...

The question, as always, is whether your vehicle's charging system delivers the proper voltage for your battery(s). Grossly, if your charging voltage runs at over 14v at 20C/70F, then you probably have no need for a B2B to boost the voltage. If, on the other hand, your vehicle runs at under 14v, then you will probably never fully charge your batteries. In this case, a B2B might be a good idea.

If you plan to rely on shore power, then an intelligent/voltage sensing relay might be an excellent choice because it will share the shore charge with the starter battery.

N.B. Self jump is a nice feature, but, if you charge your batteries correctly, you will probably never really need it. The Blue Sea comes with an override switch, with the RECARC you have to buy it separately. Either way, both can be set up to self-jump.

See dwh's posts for other details. Dirty secret - lead acid batteries charge slowly because their internal voltage rises quickly. Even with the biggest wires, as a practical matter, most of the time your actual charge rate will be around 50A.

FWIW, should you choose to use a RECARC, your question is moot as this is the only model that they sell in the US, and it can handle any voltage: https://redarcelectronics.com/products/dual_input_40a_in-vehicle_dc_battery_charger

 

[chet6.7]

Either one will work. I doubt you'd need the LV version.







Yes. Because...see next section...




The Redarc will have an ignition wire so it's turned off when the ignition switch is off. The ACR is on all the time.

So if you hook a battery charger to the engine battery when the truck is parked, the Redarc won't charge the house battery.

But the ACR will. When it senses a rising voltage on one side, it will tie the batteries so both get charged.

For that matter, you could hook both the battery charger and the solar to either battery, and the dual-sensing ACR will tie the batteries whenever charging happens from any source and both will get charged.

Thank you for the information.

 

[chet6.7]

The question, as always, is whether your vehicle's charging system delivers the proper voltage for your battery(s). Grossly, if your charging voltage runs at over 14v at 20C/70F, then you probably have no need for a B2B to boost the voltage. If, on the other hand, your vehicle runs at under 14v, then you will probably never fully charge your batteries. In this case, a B2B might be a good idea.

If you plan to rely on shore power, then an intelligent/voltage sensing relay might be an excellent choice because it will share the shore charge with the starter battery.

N.B. Self jump is a nice feature, but, if you charge your batteries correctly, you will probably never really need it. The Blue Sea comes with an override switch, with the RECARC you have to buy it separately. Either way, both can be set up to self-jump.

See dwh's posts for other details. Dirty secret - lead acid batteries charge slowly because their internal voltage rises quickly. Even with the biggest wires, as a practical matter, most of the time your actual charge rate will be around 50A.

FWIW, should you choose to use a RECARC, your question is moot as this is the only model that they sell in the US, and it can handle any voltage: https://redarcelectronics.com/products/dual_input_40a_in-vehicle_dc_battery_charger

My 180 amp alternator puts out 14V at idle,so I will give it a try without the B2B.
I agree about the self jump feature,but,as they say, better to have it and not need it ect.

Thank you for the information.

 

[chet6.7]

Best ACR on the planet: ​ https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

And for DC-DC, best is Sterling's BB series, apparently Charles has a 180A version coming out soon.

Fully custom adjustable setpoints so work with any batt chemistry including LFP.

Also control over amps to protect the upstream power source.

Thanks for the info.