dc to DC Renogy charger

[pianotuna]

Hi all,

I finally have the dc to DC 20 amp Renogy installed.

It works, but not quite as I expected.

It appears to not "like" solar much--cutting way back on amps, even though the dip switches are set to 14.7 volts output on the Renogy.

I do have manual control of the solenoid that feeds the Renogy.

It was distinctly NOT an easy install. The only place for it was under the passengers seat. I added some spacers under the unit as it appears there is an additional heat sink on the bottom of the unit.

Installation was with #8 wire.

I did turn the Renogy on after a night of boondocking where the "house" bank got down to 12.3 volts. At idle, charging was about 10 amps. At highway speed that went up to about 19 amps. I did not have a long drive that day.

I can still do a "poor man's" boost system should the starter battery ever be low.

The Renogy did stop the energy drain from the Telcom "house" jars to the engine. On the other hand, I could have done that with the original upgrade which gave me a dual charging path to the "house" bank--with manually controlled solenoids.

I think this may be the last "tech" upgrade I do.

[pianotuna]

Took the RV to storage today.

The rv had little solar charging since the 23. It is the 26 today.

The dc to DC charge was pumping 19.6 amps into the house bank.

[pianotuna]

Due to the first snow storm of the season, I did no further testing. This was the last trip for 2022.

3 semi's in the ditch is not a time to be a distracted driver.

I can say I'd definitely recommend a small dc to DC charger.

There were no signs of voltage drop on the Engine circuit. I knew before I started that the alternator was 130 amps with a 30% duty cycle.

[pianotuna]

I tried the dc to DC running the fridge on the dc setting (mine is a 3 way). I did it only for about 35 miles. It is a definite FAIL. When I plugged into shore power charging was at 34 amps.

[pianotuna]

Grit Dog,

I was moving from where I was boondocking to where I would be working. The speed limit is 10 mph as it is a College. I drove 3 blocks.

I drove about 50 miles and amps dropped to 12 (with about 5 additional from solar)

Then drove another 50 miles and amps dropped to 5 (with 4 additional from solar)

I'll have power tomorrow and the next 2 nights, too.

I may try running the fridge on DC during highway driving after the third night.

[Grit_dog]

pianotuna wrote:
Hi,

I boondocked and used the smaller inverter all night.

The dc to DC was doing 19 amps while engine was at idle.

Idling your Moho is more economical than firing up a little genny?
Or was it just a test run?

[pianotuna]

Hi,

I boondocked and used the smaller inverter all night.

The dc to DC was doing 19 amps while engine was at idle.

[time2roll]

pianotuna wrote:
The dc to DC charger is stand alone. I use a Blue Sky 30 amp charge controller. It is set at a lower output voltage than the Renogy.

[dodge_guy]

I think we are missing something here! You keep taking about the solar and the dc to dc charger, as the solar is hooked up to the dc to dc. As far as I know they are 2 different ways of charging. The solar should go directly through the mppt solar charger to the batteries and the dc to dc should be hooked up from the alternator to the house batteries.

We need a better/exact explanation of your system.

[pianotuna]

SJ-Chris wrote:
Just curious...What was the original motivation to add the DC to DC charger in the first place?

Are your RV house batteries lead acid? Or Lithium?

-Chris

The first battery bank was 875 amp-hours of marine jars. They charged from the alternator.

The replacement bank is reconditioned agm telcom batteries 556 amp-hours. They did not charge from the alternator. 3 or 4 amps would go to the starter battery. I replaced that with an AGM but that made no difference.

Lithium would be useless for me. Too many months of extreme cold.

The dc to DC does charge the telcom house bank.

[SJ-Chris]

Just curious...What was the original motivation to add the DC to DC charger in the first place?

Are your RV house batteries lead acid? Or Lithium? If Lithium I understand the need for the DC to DC charger, but in a post above it made reference to lead acid. If they are lead acid then I don't understand the need for this DC to DC charger.

Are you trying to run huge draws (ie. microwave or AC) while driving without using your generator? Seems like you could just run your generator while driving if this is the case.

Just curious. Sounds like it is generally doing what you expected so that's good.

-Chris

[pianotuna]

After the rv sat for 48 hours with solar active, the dc to DC charger was putting 12 amps into the house bank at city speeds (30 mph; 50 kph). The only draw on the bank was the fridge being run on propane. My gas valve is greedy and uses about 30 amp-hours per day.

The purpose of moving the rv was to fill up for fuel. About a 4 miles round trip. at the end 8 amps were going into the house bank.

[time2roll]

dodge guy wrote:
Did I read that right, you have the solar wired through the DC to DC? Why?

There is a Renogy DC-DC that has two input including alternator and solar.

https://www.renogy.com/dcc30s-12v-30a-dual-input-dc-dc-on-board-battery-charger-with-mppt/

[pianotuna]

dodge guy wrote:
Did I read that right, you have the solar wired through the DC to DC? Why?

No.

The solar is independent of the dc to DC, other than they both connect to the house battery bank. The solar does appear to cause the dc to DC charger to taper, even though the solar is a lower voltage. But it is early days--so that may not be correct.

The dc to DC is set to 14.7 volts (highest possible setting).

So far I'm happy with what the dc to DC is doing.

[dodge_guy]

Did I read that right, you have the solar wired through the DC to DC? Why?