60a DC-to-DC Charger Powered by 220a Alternator

[otrfun]

Thinking about installing a 60a dc-to-dc charger in our truck camper. Have plans to power it with the 220a alternator in our truck. Under a worst case scenario it could load the alternator with an additional 60a load for several hours. Any chance whatsoever it could damage the alternator with this kind of load--especially if the truck's two batteries are also discharged and pulling maximum charge current at the same time?

Also have a question about how most DC-to-DC chargers operate. Is the DC-to-DC charger output voltage limited to the maximum available input voltage (produced by the alternator)? Or, can/will the DC-to-DC charger step-up the input voltage from, say, 13.9v to 14.4v if need be?

[01tundra]

Our 12/12-18 Victron DC-DC charger outputs around 25A and the draw on the truck side is pushing 30A.

I ran a dedicated 4 AWG circuit since it's approximately 40 ft in length and I was afraid that there could be times when the alternator output dropped such that the input voltage would be below the minimum allowable with the factory 12 AWG charge wire. Victron recommends a minimum of 16 sqmm wire cross sectional area (approx. 5 AWG) for a 32 ft circuit length at 12V.

I used Anderson connectors for between the truck and trailer.

[CharlesinGA]

Five pages of posts and no one has mentioned this yet. You also could/should consider a larger alternator. Mechman makes SIX phase alternators (normal is three phase) and the six phase has twelve diodes. They have units up to about 370 amps (which would require an increase in the size of the alternator output to vehicle battery cable)

My RAM 2500 has a lowly 160 amp alternator and I am considering installing larger cables, Anderson connector, and DC-DC charger and more/larger batteries, next year. Part of the upgrade will be a Mechman Alternator.

https://www.mechman.com/

The DC=DC chargers, powered by 4 or 6 gauge cables from the vehicles batteries and connected to the trailer by Anderson connectors is becoming common and was pioneered by the Australians for their touring and offroad vehicles. It is a system that works well and eliminates the problems of the usually small power wire to the 7 pin (many vehicles cannot squeeze 10 good amps thru). I think the truck manufacturers installed the power to the 7 pin to charge the small SLA batteries used as emergency braking power on flat bed and cargo trailers and didn't expect to be charging huge banks of batteries in RV's

Charles

[otrfun]

noteven wrote:
otr - check on line for Ford’s upfitter or body builder manuals - I believe the electrical manual is separate from the chassis manual. There should be alternator output information there and/or a phone number to call.
I have a Renogy 40amp DC-DC charger on the project parts shelf. The literature for it states the input draw of the charger can be up to 1.5 times the output (60 amps for a 40 amps out model) and to size wiring accordingly.

Ray on the Love You RV u tube channel installed one and showed current measurements.

This device is connected to the starting battery not directly to the alternator.

Thanks, noteven! Good to know info. I saw Ray's demo/review of the Renogy dc2dc charger last week. Based on his vid the Renogy would appear to offer a good bit of good value for the money.

[noteven]

otr - check on line for Ford’s upfitter or body builder manuals - I believe the electrical manual is separate from the chassis manual. There should be alternator output information there and/or a phone number to call.
I have a Renogy 40amp DC-DC charger on the project parts shelf. The literature for it states the input draw of the charger can be up to 1.5 times the output (60 amps for a 40 amps out model) and to size wiring accordingly.

Ray on the Love You RV u tube channel installed one and showed current measurements.

This device is connected to the starting battery not directly to the alternator.

[otrfun]

S Davis wrote:
I have a digital volt meter to keep track of the truck voltage, it runs between 14.4 and 14.6 volts, I have driven up to about five hours straight and it never changes.

The battery voltage on our '16 Ram 3500 Cummins drops down to 13.9 - 14.0v once the batteries are fully charged. It typically takes at least an hour or so of steady freeway driving to get the batteries fully charged. Around town (which typically results in more battery loading and less charge time) the battery voltage hovers between 14.3 - 14.4v indicating the batteries are receiving a fair amount of charge current.

[RSD559]

I have the Renogy 50 amp DC2DC that I will be putting into my 2015 F-350. I'm connecting the relay that powers it to an upfitter switch. I only plan on using it when the truck is rolling, but plan on having the high idle set up as a just in case. Note on the Renogy 50 amp charger, if you have solar also connected to it, and there is voltage on the solar side, the charger will only charge 25 amps on the DC2DC side.

[S_Davis]

I have a digital volt meter to keep track of the truck voltage, it runs between 14.4 and 14.6 volts, I have driven up to about five hours straight and it never changes.

[StirCrazy]

S Davis wrote:

theoldwizard1 wrote:

deltabravo wrote:
Also, a major wiring upgrade will be needed.

This is how I did it

I VEHEMNTLY DISAGREE !

The whole point of a DC-DC charger is to NOT require oversized charging cables ! It boost the voltage at the RV battery to the correct voltage to charge the battery using the standard vehicle/trailer wiring !

Even with your large gauge wire, you should check the voltage at your campers battery after about 10 minutes of driving and at high idle. If the battery is say 80% SOC, the voltage at the camper battery should be >14.0V.

I think some of your info is not accurate, you keep talking in these threads about smart charging and the ECM controlling voltage and now engine RPM. You have been stating that you can’t use vehicle charging effectively because the charging system will lower the voltage after a few minutes to 13 volts or so, now I will state here I don’t know about Ford or Dodge/Ram but all of my Chevrolet HD trucks since 2003 do not do this, the alternator keeps voltage steady all the time, I can drive for hours and it never changes.

My ford will, but only if the batteries are topped off, if there is a draw on the batteries the voltage will stay up untill the battery is charged. this type of system was not on the fords untill .. I want to say around 2011ish, probably be simular with the gm. I dont see the battery guage move inside the truck as they are just an idiot guage, but if I watch the multimeter in the driveway after a while it will drop off to cover just the accessories you have running and a trickel to the batteries to keep them topped off. makes batteries last longer I guess.

Steve

[pianotuna]

Hi all,

Here is what happens on my class C e-450 v-10.

I sometimes use the water heater on the electric setting while driving at highway speeds (50 mph).

After 20 minutes the voltage starts to sag.

I then turn OFF the inverter which stops charging.

After 40 minutes I turn back on. After a time the voltage drop reaches 12.3 and I turn off the inverter.

[S_Davis]

theoldwizard1 wrote:

deltabravo wrote:
Also, a major wiring upgrade will be needed.

This is how I did it

I VEHEMNTLY DISAGREE !

The whole point of a DC-DC charger is to NOT require oversized charging cables ! It boost the voltage at the RV battery to the correct voltage to charge the battery using the standard vehicle/trailer wiring !

Even with your large gauge wire, you should check the voltage at your campers battery after about 10 minutes of driving and at high idle. If the battery is say 80% SOC, the voltage at the camper battery should be >14.0V.

I think some of your info is not accurate, you keep talking in these threads about smart charging and the ECM controlling voltage and now engine RPM. You have been stating that you can’t use vehicle charging effectively because the charging system will lower the voltage after a few minutes to 13 volts or so, now I will state here I don’t know about Ford or Dodge/Ram but all of my Chevrolet HD trucks since 2003 do not do this, the alternator keeps voltage steady all the time, I can drive for hours and it never changes.

This has been on four different Chevrolet trucks including a 2003 2500 HD gas truck and three 2500 HD diesel trucks, 2009, 2013 and 2019, so when you are making a blanket statement that something will not work because of smart charging you are misleading people IMHO. Also as stated before in this thread all the dc to dc chargers I looked at for my install recommend larger wire from the vehicle charging system, now admittedly I was only looking at 40 amp or larger dc to dc chargers. I am not trying to start an argument just stating my experience with GM HD trucks.

[NRALIFR]

Here’s a YouTube video of a guy demonstrating BCP on his F250 Superduty. Not sure what year exactly his truck is, if he said it I missed it. But, based on the grill style, I’d say is in the 2012-2016 range. This is how my truck behaves with BCP enabled.

The drop in RPM’s when BCP is first engaged is normal. The Ford tech that helped me with mine initially thought something was wrong when we first engaged it because the RPM on my 2010 F450 would go UP when BCP was engaged. It took a phone call to his support line to find out that it was working as designed.

BCP Demo

:):)

[NRALIFR]

theoldwizard1 wrote:

deltabravo wrote:
Also, a major wiring upgrade will be needed.

This is how I did it

I VEHEMNTLY DISAGREE !

The whole point of a DC-DC charger is to NOT require oversized charging cables ! It boost the voltage at the RV battery to the correct voltage to charge the battery using the standard vehicle/trailer wiring !

Even with your large gauge wire, you should check the voltage at your campers battery after about 10 minutes of driving and at high idle. If the battery is say 80% SOC, the voltage at the camper battery should be >14.0V.

Wiz, the standard trailer plug is only rated for 30 amps continuous, and I don’t think it’s even good for that. I’ve seen too many of them melted to believe they can sustain 30 amps.

The manufacturers all have wire gauge recommendations based on the length of the run and the DC charger output. For any DC charger over about 15-20 amps, you will very quickly exceed the capability of the standard trailer circuit.

I would recommend following the manufacturers recommendations for the input wires and fuses to the DC-DC charger you’re installing. The instructions for the 40 amp Redarc I’m using recommend 4 awg wires for the length of my circuit, which is between 25 and 30 feet.

:):)

[time2roll]

Gdetrailer wrote:
If a 300HP engine cannot stand a 3.5 HP (1%) alternator load without the need to alter the RPM it is time to scrap that engine design, it is junk..

This is about alternator RPM required to produce the power... not the capability of the engine.

[theoldwizard1]

deltabravo wrote:
Also, a major wiring upgrade will be needed.

This is how I did it

I VEHEMNTLY DISAGREE !

The whole point of a DC-DC charger is to NOT require oversized charging cables ! It boost the voltage at the RV battery to the correct voltage to charge the battery using the standard vehicle/trailer wiring !

Even with your large gauge wire, you should check the voltage at your campers battery after about 10 minutes of driving and at high idle. If the battery is say 80% SOC, the voltage at the camper battery should be >14.0V.