Renogy DC-DC 20/40/60A notes

[markopolo]

Some thoughts on additional automation for these units:

If the LC connection can be activated/deactivated when the unit is on then a $15 or so voltage comparative relay module could be used to reduce the Renogy output when alternator voltage drops due to heat or engine related loads. LC could automatically be turned on if alternator output voltage drops to say 13.6v for example. That should eliminate the drop down to 12V that Rowie has occasionally seen.

The D+ connection could also be activated by a voltage comparator relay module. You could set it that the Renogy only turns on and stays on if the system voltage is within a certain voltage range.

[rowiebowie]

Originally Posted by markopolo

Given that these units are boost/buck (step up/step down) the 40A probably meets the needs of most people that have single stock alternator equipped vans. The 40A might put as much as a 60A load on the system (according to the manual). The 60A might put as much as a 90A load on the system so maybe too much for several hours continuous run time.

I quite agree, given that it appears my 160A OEM alternator occassionally has trouble meeting charge demand while at idle with ac blowing high. In those rare instances I see a 1-2V drop in engine battery voltage. I assume it is being drawn down to assist the marginal alternator output, which quickly goes back to normal upon resuming our driving.

Or perhaps could it be the alternator cutting back current to protect itself from overheating since less air flow when stopped? I'll have to watch and see if is only happens in warm weather, but I just don't use alternator charging that much since we've mostly camped with full hookups since my litium upgrade. That will change when we venture our West again.

[themexicandoctor]

This is one of those Threads where I know;

1. This is the deep end of the Pool

2. Don't ask questions

3. Shut up & learn

4. At the end, a Golden Answer will appear.

5. If it doesn't, its from no fault of the members weighing in here

6. Instead its because like the 6 Million Dollar Man, the technology hasn't arrived yet.

[booster]

Originally Posted by rowiebowie

I quite agree, given that it appears my 160A OEM alternator occassionally has trouble meeting charge demand while at idle with ac blowing high. In those rare instances I see a 1-2V drop in engine battery voltage. I assume it is being drawn down to assist the marginal alternator output, which quickly goes back to normal upon resuming our driving.

Or perhaps could it be the alternator cutting back current to protect itself from overheating since less air flow when stopped? I'll have to watch and see if is only happens in warm weather, but I just don't use alternator charging that much since we've mostly camped with full hookups since my litium upgrade. That will change when we venture our West again.

A 160 amp alternator when hot is probably lucky to do 60 amps at idle, even if it is high idle with AC on. It is just not going to be able to keep up under those conditions.


The location of the Chevy alternator is in a quite bad spot for heat as almost all the air it gets is hot from coming through the hot end of the radiator. Water on that end is probably 220* on that end so air will probably be around 200* or more when sitting still. As soon as you are moving that airflow will increase and that will reduce the air temp through the radiator. Once the speed and engine rpm both increase the alternator will perform much better. Even a 280 amp alternator is tough to get 100 amps hot at idle with low idle speed in the 6.0 Chevies. Ours idles at 545rpm without the air on and a bit faster with it on.

[Napkintosh]

This thread is getting on in age, but does anyone know what the LC connection is actually supposed to connect to in order to begin limiting the connection? A ground? 12v? Something else?

The manual doesn't state it, not does anything else on the web I can find.

[hbn7hj]

I’ll vote for the Kisae DC to DC charger. When the source voltage drops it turns off. Not sure when this happens but somewhere between 12.0 and 12.6. It is in the manual.

[markopolo]

Originally Posted by Napkintosh

This thread is getting on in age, but does anyone know what the LC connection is actually supposed to connect to in order to begin limiting the connection? A ground? 12v? Something else?

The manual doesn't state it, not does anything else on the web I can find.

I recall that it's signal input like the D+ connection so +12V. You might be interested in this topic - https://www.classbforum.com/forums/f...way-11572.html - the addition of a $15 comparator module lets you control the Renogy unit as you think is best. You could have it turn on only if the system is 12.9V or above for example and automate current limiting as you desire. Fantastic combo IMO.

[Napkintosh]

Originally Posted by markopolo

I recall that it's signal input like the D+ connection so +12V. You might be interested in this topic - https://www.classbforum.com/forums/f...way-11572.html - the addition of a $15 comparator module lets you control the Renogy unit as you think is best. You could have it turn on only if the system is 12.9V or above for example and automate current limiting as you desire. Fantastic combo IMO.

Thanks for the tip, and the info. I think ultimately the comparator would be the way to go.

Do you think I could control both LC and D+ on a single unit? Switch space in my panel is already at a premium, and I'd love it if I could avoid using a spot for either.

[markopolo]

Two control modules would be needed for differing voltage triggers so as to get the greatest automatic control. It depends on what you want to do and the capacity of the Renogy unit as there likely would be different needs if using the 20A vs the 60A for example. You could reach out to reilym (Mike) for specific advice. His most recent post about the module is here: https://www.classbforum.com/forums/f...tml#post122952

There are likely lots of inexpensive modules that would do the required jobs but the the comparator probably allows the greatest flexibility of how to do it.

[Napkintosh]

I managed to digest the instructions and it seems you're right. I was confused about the number of input and output wires and was hoping that it might be able to control multiple output voltages but not quite in the way I wanted period.

[markopolo]

The Renogy unit's output voltage is controlled via its DIP switches. A few examples:

S5 - On
S1 - Off
S2 - On
S3 - Off
S4 - On
14.1V Absorption, 13.5V Float

S5 - off
S3 & S4 - both On
S1 & S2 - both Off
14.0V Absorption, no Float

S5: off
S1: on
S2: off
S3: on
S4: on
14.2V Absorption, no Float

I think the entire range of charging voltages is 13.2V to 14.7V on that line of Renogy DC/DC charge controllers so it's very customizable.

The comparator(s) or other module(s) add-on(s) let you automate and customize the Renogy unit's turn on and turn off voltage and lets you limit the Renogy unit's output current when desired.

[Emjayare]

I have chosen the Renogy 40amp DC to DC charger to supplement the charging of the 2, 100 amp hr AGM batteries on our 2015 Winnebago Travato 59k. After installing 2500 watt pure sine wave inverter for the microwave, it became clear that a lot of driving was required to recharge the house batteries. I see that the Renogy charger has an isolator and advises that any existing isolator be disconnected. The existing isolator ( picture attached) has 3 circuit breakers wired to it and a plug with 3 wires on the bottom. The wiring diagram from Winnebago (attached) does not help me figure out how to wire the Renogy unit. If anyone is familiar with this isolator it would be very helpful to get any suggestions on disconnecting it. Great forum, thanks.

[markopolo]

If it were my coach, I wouldn't change any of what is in the images you posted. The setup lets you start the generator from house batteries and the generator could be used to charge a low chassis battery (with ignition on) it appears.

Actually, I don't really see a pressing need for the 40A Renogy unit on a 200Ah AGM house battery RV.

It would technically be an upgrade in that it would limit coach battery charging to a maximum of 40A (20% of the combined 20Hr rating) and provide a better charging profile than alternator-only control (if programmed optimally). It might also be a bit of a downgrade because of that same 40A limitation because it could take longer to get the batteries through the bulk charge phase. It's better to think of the Renogy unit as a charge controller rather than a supplement. If the alternator was previously capable of charging the house batteries at 75A then the insertion of the 40A Renogy unit would prevent that fast charging and only permit 40A to pass.

If I was determined to install it then I'd probably work back upstream from house batteries to see if the Renogy could be inserted somewhere but also placed inside the coach as it is not a waterproof unit. I'd use a voltage trigger to turn the Renogy on and off to not have to run an ignition switched wire. I would leave all of what was shown in the images as is. The "isolator" shown is a solenoid and there would be little voltage drop through it. Traditional diode based isolators create substantial voltage drop so they should be removed if installing a Renogy unit.

[booster]

The whole limiting of battery charging current has gotten a lot more interest since the lithium batteries have gotten more popular and will often accept to much current for the wiring and/alternator to handle.


On a AGM bank, it is a bit less obvious of a need, I think. I would say it is almost totally dependent on the the components other than the batteries.


Based on what I have tested and seen our 440ah bank of Lifelines a 200ah bank would probably accept somewhere around 150 amps if charge if started at 80% discharged. That takes much larger cable than the typical #4 we have seen in many AGM banks from the OEMs. They often limit with the 80 amp auto reset breakers, so they can endlessly cycle on and off until the charge gets high enough, and the alternator hot enough, to get down to the 80 amp level. We heard this quite often when Roadtrek went to 200ah AGMs in place of the previous, lower acceptance, wet cells they had been using.



We also have seen that our Lifelines will get overly warm when charged at over about .4C, or 80 amps for a 200 amp bank.



Lifeline actually recommends using .4C for charging from more than 50% discharged for better battery life.


The Chevy alternators were 145 amps which would probably do 110 amps hot, and 20 amps of so goes to run the van leaving 90 amps. Running that high for long periods would probably result in it turning itself down if you were lucky, or getting shorter alternator life if you are not.


Based on the above, I would probably say using one of the 75 amp split charge dividers that are available (I don't recall the mfg though, and think it is 75 amps) would be appropriate for a 200 amp AGM bank with 4ga or larger wiring and maybe a bit of testing to see how hot a 145 amp alternator would get. Most new vans seem to be coming with bigger alternators now, so less of an issue at 75-80 amps.


40 amps would be on the low side for me, especially since it will pull maybe another 10 amps due to efficiency of the B to B charger from the alternator.



I would be OK with alternator charge profile as long as there was a shutoff when the batteries got full to prevent overcharging them on long drives.


Lots of ways to go and probably a lot of them will work fine for many users.

[markopolo]

For the 2015 Travato:
-SOLENOID-SEALED 8188-01-000 - 100 Amp continuous, 500 Amp intermittent
-CABLE ASM-STARTER (RED) 185087-01-063 - 1 Gauge battery cable - 150 amp
-CABLE ASM-COACH BATTERY (YEL) 141415-52-022 - 1 Gauge battery cable - 150 amp

[booster]

Originally Posted by markopolo

For the 2015 Travato:
-SOLENOID-SEALED 8188-01-000 - 100 Amp continuous, 500 Amp intermittent
-CABLE ASM-STARTER (RED) 185087-01-063 - 1 Gauge battery cable - 150 amp
-CABLE ASM-COACH BATTERY (YEL) 141415-52-022 - 1 Gauge battery cable - 150 amp

Good information, did it say what the alternator is?

[markopolo]

I don't have that info but it's probably 180A. I looked through some older forum posts and it looks like the 220A option came after 2015.

[booster]

I think this is current limiting splitter/isolator we have been told limits current rather than just cutting out, but it doesn't specifically say so.


Looks like 40 or 90 amps, though, not 75.


https://www.mastervolt.com/products/...e-mate-pro-90/

[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

[markopolo]

Just an update about the Renogy units.

Originally Posted by markopolo

#1 - LC connection - that connection is used to limit current. Charging amperage is limited to 12.5% of the rated input for the 20A and 40A models and 50% for the 60A model. The 60A model can function like a 30A model for example.......

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