Parallel alternators

[Swla]

VanFan
Thanks for the input, that’s very similar to what I’m trying to accomplish. Do you have a link to show how you setup your viper autostart. I’ve read other places where they also used viper, but when I looked up viper products I didn’t see which unit or how to do it.

With your experience with your setup would you see a benefit for a larger alternator 48v and a larger battery bank. Or is there no actual need for it. For 1200 dollars more than the nations setup I could have a 48v 160 amp setup. One scenario I’m thinking is leaving 12 volt system completely separate to run all 12v equipment and a 48v system for AC. The door to separate your sleeping area is a fantastic idea that I’m going to use, thanks.

[booster]

For those looking at Vanfan's writeups, be aware that he is mixing amps with amp hours and using amps per hour which doesn't exist.


The alternators are producing amps of current at any given time.


Amp hours are what you battery stores as energy or the amount of power you use over time.



I assume when amps per hours used it really means amp hours per hour, as in what is recovered to the batteries.



When use is mentioned as 90 amps, I assume it is really meant to be 90ah per day.


We get this kind of mish mash of units all the time on here lately. If you are trying to explain the technical aspects of your sophisticated control and power system, you really need to use the correct units so we have a clue to what you are talking about.

[booster]

Originally Posted by Swla

VanFan
Thanks for the input, that’s very similar to what I’m trying to accomplish. Do you have a link to show how you setup your viper autostart. I’ve read other places where they also used viper, but when I looked up viper products I didn’t see which unit or how to do it.

With your experience with your setup would you see a benefit for a larger alternator 48v and a larger battery bank. Or is there no actual need for it. For 1200 dollars more than the nations setup I could have a 48v 160 amp setup. One scenario I’m thinking is leaving 12 volt system completely separate to run all 12v equipment and a 48v system for AC. The door to separate your sleeping area is a fantastic idea that I’m going to use, thanks.

IMO, having the 48v system is a big advantage for any high power use item, including the microwave, hair dryer, induction hot plate, etc, as all the line losses are going to be less and much less wire size needed. A 48 to 12vdc converter will take care of the normal 12v stuff which is usually well under 50 amps of 12v need. Even going to a 24v system is a big improvement, I think.



Adding a curtain or door of some sort is a very common thing done to increase the usable capacity and/or reduce the energy needed to condition the sleeping area, both for heating and cooling situations, and works well if it seals well. If you are claustrophobic, it might give some issues, though, for some people as the area gets pretty small.

[Swla]

I was thinking instead of a 48v to 12v converter just add a couple of house batteries to charge from stock 200amp alternator. Keep both systems independent and utilize both alternators, no sense in having extra charging capacity and not using it. I would be running engine to charge 48v batteries from 48v alternator which would simultaneously be charging 12v batteries from 12v alternator. 12v batteries wouldn’t need to be a huge ah total due to low power needs and frequent recharging from engine. What is your opinion on this setup.

[VanFan]

Originally Posted by booster

If they are not matched close enough to share the load one can max out and the other not put out much at all.

Interesting. Please educate me. Let's assume we have two alternators with different regulators (say one is the OEM unit controlled by internal regulator or by the on-board computer, and the other is an aftermarket unit controlled by an aftermarket regulator). What would cause the higher output of one to reduce the output of the other?

[booster]

Originally Posted by VanFan

Interesting. Please educate me. Let's assume we have two alternators with different regulators (say one is the OEM unit controlled by internal regulator or by the on-board computer, and the other is an aftermarket unit controlled by an aftermarket regulator). What would cause the higher output of one to reduce the output of the other?

If one is controlling at say 14.5v and the other at 13.8v the lower voltage one is basically going to have very low output or none if the 14.5v alternator is capable of handling the load by itself, allowing it to hold that higher voltage. Voltage is like water pressure, higher will shut off the lower one.


Most of the newer systems that are PCM controlled use some kind of smart charging profile in the voltage regulator area, as do many of the internal regulators. They turn the voltage up a down and also will change the output by increasing field current. If you have two regulators trying to figure out what is going on, they can easily wind up fighting with each other for control.



For a while we ran a single DC Power 250 amp XP series alternator with an internal regulator, which is Denso. It was interesting to see how it did things, as it was very obvious on the voltage gauge and amp gauge I have connected to monitor things. It would soft start, ramp up voltage to 14.5v and hold for a while then would start to fall back in voltage over time, slowly, probably based on field current needed to maintain voltage setting. What was really interesting is that it would periodically ramp the voltage back up, probably to see if the battery took current due to being discharging or such, and then would go immediately back on. If I turned on the headlights and heater fan while it was doing the check, it would stay high until I turned them off. Imagine have two of this kind of regulator doing this kind of stuff without getting in conflicts and you see why having both alternators controlled from a single regulator is a good idea. If the regulator had two independent field outputs controlled by the input information, you could use more mismatched alternators as long as the outputs could also be tuned independently. Most don't have independently settable field outputs, making close matching of alternators necessary.


If the OP does a higher voltage system, it gets to be a mute point, as the alternators have to be separate, so solves that issue completely.