New Renogy Battery-2-Battery Charger

[tx2sturgis]

I see that Renogy now has a reasonably priced, battery-2-battery charger, available in 20 amp and 40 amp models:

https://www.renogy.com/renogy-12v-dc-to-dc-on-board-battery-charger/

I have never used one, but one of these might work well in a dual-battery van-build.

 

[bullfrog]

Says it overcomes problems associated with long wiring runs. How the heck does it do that?

 

[highdesertranger]

"How the heck does it do that?"

marketing? LOL.

highdesertranger

 

[tx2sturgis]

Think of it as a power supply:

It regulates the output precisely, rather than passing along whatever the voltage and current is (with associated voltage drop) as with a long run from say, your alternator, to your coach batteries, at the back of an RV or van.

Just as important, it can charge a lithium battery house bank FROM a regular lead-acid starter battery and alternator.

 

[Weldman]

Consumes a half of an amp a hour on just sitting there not charging, better put a disconnect between it and the charging batteries.

 

[Seminole Wind]

just a programmable boost converter. not much range of voltage adjustment though

it is clearly superior to a direct connection from the alternator regardless of idolators or auto combiners

i have done several tests measuring the amps going from the alt to a second battery and it is pitiful. maybe get a spurt of 10 amps but then it settles down to a trickle of 5 amps or so and stays a good half volt under the starter battery.

but with a 20amp boost converter you get 20 amps constant current charge till it reaches the set point voltage even if it is higher than the source battery.

i am not sold on this particular product. too new, never been impressed with their line of products. ( good entry level stuff but not any more than that) it might be double the price but i would opt for a higher quality more controllable programmable unit like the sterling B2B chargers. or i would just get a $40 boost converter off amazon. ( i have a 22 amp one and love it)

i am happy to see more of these B2B products comming to market, more choice is always better

 

[tx2sturgis]

It is nice to see a mid-range product that addresses the issue of someone having a regular starter battery and alternator, and then adding lithium as a house battery, with a good way to charge that new lithium battery when driving. 

The applications for van-dwellers and retrofitting a motorhome with a lithium house-bank seem to be the sweet-spot for something like this.

Anyway, it was in an email I got from Renogy, and since it is new, I thought I'd start a thread about it.

I own and use a couple of low-range to mid-range Renogy solar charge controllers that seem to work well for me.

 

[mjbeam]

It is nice to see a mid-range product that addresses the issue of someone having a regular starter battery and alternator, and then adding lithium as a house battery, with a good way to charge that new lithium battery when driving. 

The applications for van-dwellers and retrofitting a motorhome with a lithium house-bank seem to be the sweet-spot for something like this.

Anyway, it was in an email I got from Renogy, and since it is new, I thought I'd start a thread about it.

I own and use a couple of low-range to mid-range Renogy solar charge controllers that seem to work well for me.

Thanks for posting this. I am working on a van build that I use as an office; batteries are primarily to power a laptop for 12-14 hours a day. Currently I recharge the batteries overnight with an Optima battery charger. I was going to install a battery isolator to partially recharge the batteries during my drive back and forth to work as the Optima charger doesn't always fully recharge the batteries overnight. This looks like it may be a better option than the isolator.

 

[Matlock]

snipped
I see that Renogy now has a reasonably priced, battery-2-battery charger, available in 20 amp and 40 amp models:
I have never used one, but one of these might work well in a dual-battery van-build.

ts2, thinking about getting one? I'd enjoy seeing the results hooked up to your LifePo4.

 

[tx2sturgis]

Ironically, I was looking at buying a B-2-B charger a few weeks ago, as I was incorporating a lithium battery alongside the 2 lead-acid batteries in my new trailer. LiFePo4 batteries prefer a different charge 'profile' and would not be fully charged if you simply 'parallel' them (with an isolator or a solenoid) with your other lead-acid batteries.

The $300-$500 price range of the quality units seemed a bit high for me, since I only need to replace small amounts of power consumed over many hours, running radio equipment. Plus, these types of buck-boost switching power supplies tend to be noisy in the RF spectrum, which might be an issue for my radio equipment.

If the duty cycle was different, and if I could perform a basic RF noise survey that shows low noise levels, I might have gone that route.

But, I found another solution, more reasonably priced, and suitable for my use, and I have incorporated those into the trailer. 

If I had known about or seen this Renogy B-2-B charger then, priced as it is, it might have been on the shopping list.

 

[mjbeam]

Could a solar charge controller be used like this unit? Connect the vehicle battery to the input of the charge controller where the solar panels would normally be connected? Or is 12-14V not enough for a solar charge controller to work with?

 

[tx2sturgis]

Using a PWM solar controller, the 12-13v input voltage will not be enough to charge a lithium battery. I have used a controller this way to 'maintain' a lead acid battery. 

An MPPT controller might charge an LFP battery IF it is designed to 'boost' low input voltage. There might be issues with voltage sags and spikes if it was used on the primary starter side of the vehicle/battery circuit. Mine was on a 'solar only' system.

Generally, if we use electronic devices for 'off-label' applications, we assume the risk of damage or failure.

I have not tried this myself so it would be best to look up the specs for the unit of interest or call the manufacturer/distributor.

.