Alternator load from Renogy RBC50D1S Real World?

[Buster1903]

I am trying to figure out how much of a load a Renogy RBC50D1S will put on my alternator.
I have a 2007 Honda Civic with a 90 amp alternator. But it’s 14 years old.
I have read several threads and the Renogy spec sheet but I might be more confused now than when I started.

I have a good Optima starting battery in my civic and I will be charging a SOK 100ah LiFePo4 battery in my tiny travel trailer. And I have a Dokio 160W portable solar panel (plan to up grade solar soon).
I bought the 50amp model over the 30amp for future capacity and it was on flash sale ($189), but not a good deal if I burn up my alternator.

Help.

 

[HRTKD]

If your LiFePO4 battery has a low state of charge, it could take the entire 50 amps that the Renogy device can output. The 50 amp output will most likely (90% chance) draw more than 50 amps from your car's system.

1. I think you should have gone with the 30 amp DC-DC charger
2. I hope your wiring is up to the task of that many amps
3. The PV system's output may help mitigate the need for so much power from the car

 

[Buster1903]

If your LiFePO4 battery has a low state of charge, it could take the entire 50 amps that the Renogy device can output. The 50 amp output will most likely (90% chance) draw more than 50 amps from your car's system.

1. I think you should have gone with the 30 amp DC-DC charger
2. I hope your wiring is up to the task of that many amps
3. The PV system's output may help mitigate the need for so much power from the car

Thanks HRTKD, I will be retuning the RBC50D1S. And now I'm even questioning the 30amp version. The simplicity of these is attractive but Renogy's stat sheet is vague and misleading.
I do not have wiring yet, still planning system. I will get wiring last to best fit it.
And my current PV will only be possible when my rig is parked, even mounted panels would only help with good sun.
This was a knee-jerk buy when I saw it on sale. Hoped I could make it work.

 

[John Frum]

Get a dc clamp meter with peak feature and test.

 

[Buster1903]

I assume the "Victron Energy Orion-Tr IP43 12/12-Volt 18 amp" is a solid solution in my situation. Then learn about duel-charging options.
I'm not worried about slower charging as the house battery is mostly for entertainment and the health of the tow vehicle is absolutely the priority.

Anyone have suggestions?

 

[Buster1903]

Get a dc clamp meter with peak feature and test.

Yeah but at 50+amps I could burn up the alternator just doing the test.

 

[John Frum]

Yeah but at 50+amps I could burn up the alternator just doing the test.

The first test would be how much your car draws with all the accessories on from the alternator.
That will give you some idea how much excess capacity there is.

 

[HRTKD]

I assume the "Victron Energy Orion-Tr IP43 12/12-Volt 18 amp" is a solid solution in my situation. Then learn about duel-charging options.
I'm not worried about slower charging as the house battery is mostly for entertainment and the health of the tow vehicle is absolutely the priority.

Anyone have suggestions?

I would take a 20 year old Victron device over a brand new Renogy any day of the week. The 18 amp rating is more reasonable for your situation.

 

[Buster1903]

The first test would be how much your car draws with all the accessories on from the alternator.
That will give you some idea how much excess capacity there is.

ok, I get it. But I think it's a no brainer at this point for the 50amp charger, but I will still check the excess capacity. That's just a good idea! thank you

 

[John Frum]

ok, I get it. but I think it's a no brainer at this point for the 50amp charger, but I will still check the excess capacity. That's just a good idea! thank you

Whatever dc 2 dc charger you use I would suggest you rig it to not charge when the engine is idling.
The alternator can't cool itself well at low rpm.
Some folks have had success by putting a switch in series with the ign circuit so that they can administratively enable the dc2dc charger after they are up to road speed and the starter battery has had a chance to top off.
The downside is that the driver has to remember to turn the switch on and off.

 

[HRTKD]

The Victron DC-DC charger (not sure this applies to all their models, of course) has a voltage sense that picks up if the alternator is active or not. Maybe it is a parameter that can be set to ensure you're not drawing a load at idle. Just throwing that out there. I don't use a charge from the tow vehicle with my RV trailer's LiFePO4, so I have no experience with this.

 

[A.Justice]

Whatever dc 2 dc charger you use I would suggest you rig it to not charge when the engine is idling.
The alternator can't cool itself well at low rpm.
Some folks have had success by putting a switch in series with the ign circuit so that they can administratively enable the dc2dc charger after they are up to road speed and the starter battery has had a chance to top off.
The downside is that the driver has to remember to turn the switch on and off.

I do this with my "shore power" Renogy DC to DC setup with a server rack PSU. I switch the charger on when I need power, rather than have it always charging. When I eventually wire it up to my car battery I'll keep the switch so I can completely control at what times I charge (I'd rather not charge in heavy summer traffic or while idling).

I wonder if we could use some type of sensor to turn it on when the car is above a certain speed? ? I do have a cheapo Bluetooth OBD2 reader that is capable of live raw data output, the app shows all of my dash gauges (and a bunch of other useful information, air flow, fuel system pressure, timing, etc).

Maybe a little adafruit or pi (or whatever cheap, tiny, Linux computer has Bluetooth), connected to a relay on the charger.

 

[Stepandwolf]

Do the DC>DC have a way to monitor the alt voltage and react accordingly. Seems that with high draws or low charging, the voltage would drop below a level the charger takes juice. When it senses more voltage available, it could then draw some power. I was reading about one, perhaps the Victron, that does sense ability to safely draw power.

 

[John Frum]

I do this with my "shore power" Renogy DC to DC setup with a server rack PSU. I switch the charger on when I need power, rather than have it always charging. When I eventually wire it up to my car battery I'll keep the switch so I can completely control at what times I charge (I'd rather not charge in heavy summer traffic or while idling).

I wonder if we could use some type of sensor to turn it on when the car is above a certain speed? ? I do have a cheapo Bluetooth OBD2 reader that is capable of live raw data output, the app shows all of my dash gauges (and a bunch of other useful information, air flow, fuel system pressure, timing, etc).

Maybe a little adafruit or pi (or whatever cheap, tiny, Linux computer has Bluetooth), connected to a relay on the charger.

Maybe some way to determine when the car is in road gear and/or overdrive.

 

[Stepandwolf]

Maybe some way to determine when the car is is road gear and/or overdrive.

Some of us never get in overdrive, i.e. if pulling a trailer and you are in "tow mode".

 

[Bubba1]

I'm going with a low out put victron. 9 amp $65

 

[Buster1903]

At this point the Renogy RBC50D1S is on it's way back. Renogy "no hassle returns" = Big pain in the ass!

Victron Energy Orion-Tr IP43 12/12-Volt 18 amp and a duel charging set up (Hope this does not get to complicated or costly) is the way I'm headed. I think 18amps is a load my Alt can handle at any time. I really try to follow the KISS principal.
If I'm (or you're) worried about the alt. The inline switch seems simple. For an automatic/self-sensing solution (not simple). How about a Temp switch mounted to the alt itself with a rely to disconnect the system. A little old school but, alt overheating is what we are worried about.

 

[Buster1903]

An explanation of how an alternator works is missing form the conversation.

(this is my understanding form experience, if you really know better or have a good link to explanation feel free to speak up)
An Alt acts as a constant voltage source. It will try to maintain 13.6 volts-ish as best it can.
If your vehicle is running and the voltage is dropping below this, the Alt is already working at full capacity. Any voltage sensing cut off while the engine is running would be a last line of safety ie. fuse blowing. It may not be a good way to limit alt work load.

 

[Sirtate]

Some of us never get in overdrive, i.e. if pulling a trailer and you are in "tow mode".

There is a Starter interlock switch in Automatic Transmissions to keep you from grinding the starter gears to smithereens while in gear, it only allows voltage from the starter position on the key to flow if the transmission is in "Neutral" or "Park"... perhaps that could be the "gatekeeper"...
If accessory voltage is present (radio is ON), and the interlock switch is open, power flows to the charger... a MOSFeT solid state relay could do this, a quick search showed one that will trigger at 12v, and can switch 150a... https://www.thomasnet.com/catalogs/...50100-mosfet-technology-dc-solid-state-relay/

If the car is a manual transmission, a simple switch on the parking brake could do the job...

Either way, this would keep the alternator from being forced to charge the house batts while parked.

 

[Stepandwolf]

Some people may choose to increase the idle speed and use the charger while parked. Reminds me of my first cruise control, a snow scrapper between the seat and the pedal.