Renogy DC-DC 20/40/60A notes

[markopolo]

Originally Posted by Emjayare

Thankyou for all the info. Before I read that the existing isolator had to be removed I had planned the Dc to Dc charger install adjacent to the inverter, (under the drivers side bed). I have attached the drawing I did at that time. I think I would add a remote switch for the charger rather than the ignition switch. From what you folks are saying though I am questioning my wisdom. I had read that the alternator was not setup to charge the house batteries and that's why it was taking so long to charge. Is that incorrect? Thanks

With adequately sized wiring, Renogy 40A would need more than 50A fuse on the input. Manual indicates 60A. 50A on output is OK.

It takes a long time to charge lead acid batteries.

Do you known what voltage your alternator outputs? It'll vary but are you seeing over 14V for example?

[booster]

Originally Posted by markopolo

Just an update about the Renogy units.



In the current manual, the LC connect current limiting is listed as 50% for all three models now.

Is LC an input that could be put on a dash switch? If so, that would be useful feature, I think for the OP if he had a 60 amp. Use 60 amp setting for the first 20 minutes or so and then go to 30 for the rest, or even back to 60 after the alternator cools off a bit if you will only driving a short time.

[markopolo]

Yes, LC could be controlled through a dash switch. It just needs to see +12V to activate as far as I know.

[booster]

Originally Posted by markopolo

Yes, LC could be controlled through a dash switch. It just needs to see +12V to activate as far as I know.

That would be a good option to use, I think, to help alternator and battery life for some systems. We do similar in our much larger 440ah bank with two parallel alternators feeding them and the engine. Our output is infinitely setable in two steps so we have it set to 180 amps on high and 120 amps on low and use it as described in the suggestion above, but in normal use we rarely need to use the 180 setting as we don't normally have a lot of capacity to make up as the solar does quite well. When I first installed it, I had it set at 280 amps and 180 amps and it was never off of 180 amps so I changed it.

[Emjayare]

Marcopolo, I was pondering your idea that the chassis battery could be charged by the generator with the ignition on. I haven't tried that but what I do have is a 'boost' switch which lets me use the house batteries to boost the starting battery. I assumed that was what the relay on the left of the isolator is for. It's a bit useless however since it doesn't work if the chassis battery is dead, only if its weak!

[JohnnyFry]

I would make an additional point to Boosters excellent post. The self resetting breakers are not really designed to control charge current on a continuous basis; they are designed to disconnect due to an occasional overload condition, Using them as a current regulator in this way shortens their life expectancy considerably. It is not a big deal to change out the one under the hood, but changing the rear one on my 2008C210P is a serious PITA as it is mounted in a small metal connection box under the chassis.

[JohnnyFry]

I use a separator relay in the same way, as a booster. I did take the activation current from the house battery, however.

[markopolo]

Originally Posted by Emjayare

Marcopolo, I was pondering your idea that the chassis battery could be charged by the generator with the ignition on. I haven't tried that but what I do have is a 'boost' switch which lets me use the house batteries to boost the starting battery. I assumed that was what the relay on the left of the isolator is for. It's a bit useless however since it doesn't work if the chassis battery is dead, only if its weak!

I was guessing at the ability to charge a low chassis battery via the genset as there is a path shown in the schematic. It has to go through the solenoid so there needs to be enough voltage to drive the coil so I figured it would be for a low battery and not work with a dead battery. With the common chassis ground, I'd think that the solenoid coil could be driven via house battery voltage for boosting the battery but have never tried that so just an assumption.

Are those parts easily accessible or under the coach? If accessible then a short temporary jumper cable on the outer solenoid posts could join house & chassis batteries for boosting the battery.

[markopolo]

Just some notes:

There are many similarities (operational and specification) between these Renogy unit and Dometic's Perfectpower line: https://www.dometic.com/assets/19/93...9-07_71993.pdf

also, IUoU battery charging - https://en.wikipedia.org/wiki/IUoU_battery_charging

The absorption mode is Uo. Time and current both can initiate the transition to U (float) mode. The Renogy manual lists the max time at 3 hours but doesn't mention the amperage trigger. From the manual: "Heavier battery discharge may set controller back to Bulk/Absorption" would seem to confirm that Uo to U & U to Uo are triggered by current. It would be nice to know what the amperage trigger value is. It shouldn't be too difficult to figure that out.

[Emjayare]

Marcopolo, not sure about the alternator output. The voltmeter I have on the battery is normally off, I just turn it on to check the battery before I start. Will leave it on while driving to check the output. There is not a great deal of ground clearance under the van so its a bit of a wiggle to get at but if needed it's doable. Thanks for the tip, a lot easier the trying to run a jumper from the house battery to the chassis battery!

[larrylwill]

I have a similar problem, but I have a 2019 RT with a UHG (2nd Alternator) that puts out 280 amps. I put in a DIY 280Amp lifepo2 battery and 150 Amp BMS but I cant charge the battery from the Alternator, the BMS disconnects. I read 14.7v out of the alternator and 14.4 out of the BMS. My starter battery is charged by the 1st alternator and the 2nd is just for house batteries. I looked into a Renogy 60A dc to dc but really seems a waist. I also have a Voltstart and had hoped to use the AC at night and let the voltstart start the engine to recharge the batteries but at 60 Amps it would run all night to get them charged compared just the alternator. I noticed that the alternator only outputs 280 amps for a few munits before dropping to 120-140 to complete the charge. Right now Im in limbo as to what is a good solution.

[hbn7hj]

Originally Posted by larrylwill

I have a similar problem, but I have a 2019 RT with a UHG (2nd Alternator) that puts out 280 amps. I put in a DIY 280Amp lifepo2 battery and 150 Amp BMS but I cant charge the battery from the Alternator, the BMS disconnects. I read 14.7v out of the alternator and 14.4 out of the BMS. My starter battery is charged by the 1st alternator and the 2nd is just for house batteries. I looked into a Renogy 60A dc to dc but really seems a waist. I also have a Voltstart and had hoped to use the AC at night and let the voltstart start the engine to recharge the batteries but at 60 Amps it would run all night to get them charged compared just the alternator. I noticed that the alternator only outputs 280 amps for a few munits before dropping to 120-140 to complete the charge. Right now Im in limbo as to what is a good solution.

Just an opinion but to me the answer is obvious. Put in the 60 amp DC to DC charger and don’t think about the A/C overnight till you try what you have. If it is Diesel they really don’t do well idling long term anyhow. If you want A/C it is shore power.

[larrylwill]

Gas burner. Yes I could then might as well sell if possible my 2nd $900 alternator. I lived with 1 battery for 20 years.

[hbn7hj]

Keep the alternator, add a second DC to DC charger along with a battery or two.

I have 400 amp hours of lithium charged by an Onan at a rate of 120 amps. Works very, very well with short generator runs as yours would be.

I run electric mattress pads, satellite TV. I received Starlink but haven’t turned it on yet. Latest info from others say 5 amps at 12 volts. We will see. Would like to charge at 200 amps but haven’t figured out how to do that.

My 12 volt chargers are not additive. I suspect multiple DC to DC chargers would not be either.

Put A/C by battery in the long term project category.