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Open Roads Forum  >  Tech Issues

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

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theoldwizard1

SE MI

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Posted: 01/11/21 12:55pm Link  |  Quote  |  Print  |  Notify Moderator

otrfun wrote:

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.

How big is your current alternator ? It is probably sufficient to power a 60A DC-DC charger.

otrfun wrote:

Also have a question about how most DC-to-DC chargers operate.

Without getting into too many gory detail:

• Incoming DC is converted to AC by switching it on and off. This is done much faster than the 60Hz that we get from the power company so that they can uses smaller transformers.
• The transformer boosts this AC voltage to something higher than required to charge batteries (18VAC-24VAC ?)
• This AC voltage is converted back to DC
• Some kind of "smarts" controls the output DC voltage to the appropriate amount.

Gdetrailer

PA

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Posted: 01/11/21 01:02pm Link  |  Quote  |  Print  |  Notify Moderator

otrfun wrote:

jkwilson, thanks, good to know a dc-to-dc charger is capable of voltage compensation.

Gdetrailer, thanks for the explanation. I was aware of some of the various limitations and concerns which is why I posed my question. With dc-to-dc chargers becoming more mainstream and the Ram Cummins being one of the more popular TV's, I was hoping there may be more specific info in regards to what this alternator (and/or a Ford/Chevy HD alternator) is or is not capable of.

FWIW, I believe the stock alternator on a Ram Cummins is rated at 160-180a. Our truck came with the optional 220a alternator. Wouldn't this extra capacity significantly reduce (not eliminate) any concerns about an additional 60a load on this alternator---even at idle?


No "significant" reduction of "concerns", just means the alternator MIGHT be able to provide an additional "burst" of charging current.

Couple of things come into play with alternators, one is the small space provided for the alternator.

To allow for more current, the "windings" in the alternator must be considerably heavier (larger ga of wire). Heavier ga wire means LESS windings in a given space which means the alternator now must physically be larger (circling back to space limitations in the engine compartment) so, what typically happens is the alternator must spin faster with less windings meaning that they have to use a smaller pulley on the alternator to spin it faster..

I remember yrs ago, there used to be an outfit that sold "upgrade" windings for 1950's-1980's alternators which would take a 35A alternator and get you 45A-60A.. The drawback was the alternator was no longer able to generate enough voltage at idle that it would not charge at idle.. Lights dimmed every time you stopped and got bright every time you started moving.. Sometimes you could find a smaller pulley for the alternator and sometimes not..

More current also means that they will have to add several extra diodes in the output of the alternator or use higher current diodes, both of these outcomes requires more internal space in the alternator and additional cooling..

Now days, things have gotten a lot more complicated, most manufacturers have now put the body control computer in charge of the charging system and the body control computer now regulates what the alternator can and can't do.

While you can add in a heavy 12V load for short bursts, I would not really recommend do that for long periods of time like heavy charging of your RV battery under idle conditions..

The exceptions to that would be IF you have a "ambulance prep" type of package, the manufacturers will have modified the electrical system, body control computer and alternator for that type of heavy stationary use..

Something else to consider, prolonged idling of a Diesel can lead to "Wet stacking"..

theoldwizard1

SE MI

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Posted: 01/11/21 01:05pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

60 amps is probably higher than the designed add-on accessory load for the vehicle. Assuming it is a diesel the grid heater or glow plugs may also add significant 12v load. You could reduce the issue by not immediately turning on the A/C and running lights etc.

The opening statement is probably true. The good news is that the modern "smart charging" systems will increase the engine speed to get the most out of your alternator.

I don't know how DC-DC chargers control the current draw. As the input voltage goes down, the input current (amps) goes up. I am sure there is some smarts in the charger to prevent "bad things" from happening. The fuse in the charge line to your RV is the limiting factor. Typically 50A ?

Not running the A/C or turning on vehicle lights say for the first 10-15 minutes will help.

theoldwizard1

SE MI

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Posted: 01/11/21 01:16pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

I remember yrs ago, there used to be an outfit that sold "upgrade" windings for 1950's-1980's alternators which would take a 35A alternator and get you 45A-60A.

Quick Start High Output Alternators

Gdetrailer wrote:

More current also means that they will have to add several extra diodes in the output of the alternator or use higher current diodes, both of these outcomes requires more internal space in the alternator and additional cooling.

The same place sells external rectifiers (diodes). IMHO, they are not required. Higher current diodes are the same size (obviously up to some limit)

Gdetrailer wrote:

Now days, things have gotten a lot more complicated, most manufacturers have now put the body control computer in charge of the charging system and the body control computer now regulates what the alternator can and can't do.

Actually, my experience has been the powertrain control computer talks to the alternator, primarily because the alternator may request more engine speed.

Gdetrailer wrote:

While you can add in a heavy 12V load for short bursts, I would not really recommend do that for long periods of time like heavy charging of your RV battery under idle conditions.

Define "heavy" ? If the typical vehicle load, at idle, is 40 A and you have an alternator capable of 100A, the alternator will just call for more engine speed. (Alternator don't reach max capacity until about 2000 engine RPM.)

Most trailer tow packages include a heavy duty alternator. If not, that is a good upgrade.

S Davis

Western WA

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Posted: 01/11/21 01:51pm Link  |  Quote  |  Print  |  Notify Moderator

I am running the 50 amp Redarc and everything has been working great. I am adding another pair of batteries and another 50 amp charger for 100amps total. I also have the snow plow prep on my 2019 Chevrolet with a 220amp alternator.

otrfun

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Posted: 01/11/21 02:48pm Link  |  Quote  |  Print  |  Notify Moderator

S Davis wrote:

I am running the 50 amp Redarc and everything has been working great. I am adding another pair of batteries and another 50 amp charger for 100amps total. I also have the snow plow prep on my 2019 Chevrolet with a 220amp alternator.
Thank you, S Davis!!! I was so hoping to hear from someone who had actually tried this. As I mentioned earlier, I also have a 220a alternator on my truck. Good to hear you had good results at 50a. It'll be interesting to hear how things go with 100a.

Do you primarily charge while you're on the road? Or, do you sometimes park and charge? If so, for how long? Are you able to obtain a full 50a while your truck is at a standard idle (vs. a fast idle)?

Gdetrailer

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Posted: 01/11/21 03:56pm Link  |  Quote  |  Print  |  Notify Moderator

theoldwizard1 wrote:


Define "heavy" ? If the typical vehicle load, at idle, is 40 A and you have an alternator capable of 100A, the alternator will just call for more engine speed. (Alternator don't reach max capacity until about 2000 engine RPM.)

Most trailer tow packages include a heavy duty alternator. If not, that is a good upgrade.


Alternator IS NOT going to "call" for more "engine speed", alternator is extremely tiny "load", so small it is insignificant..

Not sure how much HP you believe an alternator is going to need but 220A 12V alternator is 2,640 watts..

General rule is 746W is equivalent to 1 HP..

Using the general rule a 220A 12V alternator is going to need a max of 3.5 HP from an engine capable of 300+ HP which is about 1% of that engine..

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..

I think your assumptions that the body control or engine control is going to automatically "boost" the idle JUST FOR THE ALTERNATOR is wrong.

Manufacturers do not even do that for the A/C compressor (RPMs DO drop when the A/C compressor turns on at idle, typically a 50 RPM drop in idle speed).

Now if you are talking an "Ambulance or Emergency" prepped vehicle, that IS a different beast, those vehicles ARE modified and certified for those types of use where they may have special critical power needs..

pianotuna

Regina, SK, Canada

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Posted: 01/11/21 04:06pm Link  |  Quote  |  Print  |  Notify Moderator

Hi,

It makes no sense to me to idle a 300 hp engine to end up with 3.5 hp of output. I don't think the diodes in the alternator will "like it", either.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

grizzzman

salt lake city, Utah

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Posted: 01/11/21 04:13pm Link  |  Quote  |  Print  |  Notify Moderator

Like a 300 horse engine is producing anything near that at idle......
I have a 40 amp DC to DC charger. It is a buck-boost device. At 14 volts input will output 40 amps at 14.7 cost is 50 amps input. At 12.7 volts (gotta love "smart" charging) 34 amps at 14.2 volts. The 220 amp alt handled both at idle without issue.

* This post was edited 01/11/21 04:21pm by grizzzman *


2019 Ford F150 EcoBoost SuperCrew
2016 Rockwood Mini Lite 2504S. TM2030 SC2030
640 Watts Solar. Costco CG2 208 AH and Lifepo4 3P4S 150 AH Hybrid. TS60 Morningstar SCC.Renolagy DC to DC charger. 2000 Watt Inverter.
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NRALIFR

Truck Camping Out West

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Posted: 01/11/21 04:34pm Link  |  Quote  |  Print  |  Notify Moderator

otr, one thing you might look in to is whether there are any stationary power features that can be enabled on your truck that specifically pertain to managing the alternator output when idling.

On Ford superduties, there’s a feature called “Battery Charge Protect” that enables the ECM to monitor the battery voltage when the parking brake is set, and the transmission is in Park, and it will vary the engine RPM from 600-1200 while large power loads are on the charging system. This is for using inverters, DC-DC chargers, etc while idling the engine. The ECM also monitors the engine temperature while in this mode, and won’t let the engine overheat.

I have it enabled on my truck, and I use one of the up-fitter switches to turn it on. It does work, and I use it occasionally. It’s a little better than a high-idle tune on a programmer because it only does what’s necessary to maintain good battery voltage. But if your truck doesn’t have anything like that then I would look at getting a high-idle tuner if you intend to stationary charge using the truck. Doing that occasionally is your choice. Of course, if you need to do it a lot it may make more sense to buy a small generator. But, I try not to tell other people how to spend their money or use their equipment. As long as you’re paying your way, it’s your choice.

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