Dual alternators

[missouri_dave]

I see the truck manufacturers all have an optional dual alternator package available. From the point of view of a tow vehicle pulling a TT, is this desirable? What are the benefits here?

[travelnutz]

I had ordered my crew cab LB 4X4 Chevy Duramax with dual alternators and here's why. At idle I get twice as many amps going to the RV batteries thru my added high amp slide switch and the truck ignition switch current controlled added relay and thru the #2 fine strand welder cable I ran back along the truck's frame to the trucks bed and the 2 additional group 31 big deep cycle batteries in the bed side. Fused at both ends with 80 amp marine exterior replaceable fuses. From there, 2 same cables (1+ and 1-) go back to the 5th wheel also to brass studs with stainless wingnuts and they go to a 500 amp marine barrel rotary switch on the 5th wheel which has 5 more of the same batteries in the front of the 5th wheel compartment.

These added #2 cables now supply massive 12V DC amps to the 7 large deep cycle batteries (provides 1575 minutes of a 23 amp draw) recharged from the dual alternators and it powers the 2500 watt inverter also in the 5th wheel front compartment. Also supplies the RV's 12V DC circuits. For inverter 110V AC in the 5th wheel, I installed 2 110V AC #14 separate circuit lines from the inverter to 3 mounted duplex outlets on each line and look just like the OEM outlets on each line thru out the 5th wheel (12 additional 110V AC outlets). They are labeled "Inverter". Thus, I have gobs of 12V DC and 110V AC in our 5th wheel with or without being on shore power and the batteries recharge real fast at the truck engine idle too and extremely fast when driving.

Not hard to do and not that expensive either. Also works fantastic with the big Lance TC when on the truck as it has a 1500 watt inverter and thus 3 big deep cycle batteries (675 minutes at a 23 amp draw) to power the TC and the inverter too.

Just a simple extension patch cord from the added inverter line outlet silently powers the microwave or coffee maker etc when it's wanted with no shore power or needing to start the onboard generator that's on each RV and all with no sound. Also the onboard generators will recharge the RV batteries fast thru the 55 amp RV converters if needed. It's called having all the bases covered and having your cake and eating it too. Yup, being a retired engineer, I love to design, make, and do things to make life and RV'ing better anywhere anytime and being TRUELY totally self-contained or just plug into shore power if it's available. Pampered old farts we are but we like it!!!

Did I say it works perfect and so versatile??? My system is now nearly 20 years old, been move from one truck to another, and have never even blow a fuse yet, and will be moved again if I purchase a new truck but this truck would have to wear out first, and not likely in my lifetime as it only has about 200,000 miles on it now of all RV use only as we have other vehicle to use for other needs. Love my dual alternators and will have them again!!!

[KD4UPL]

If you have a winch, off road lights, big stereo, 12v compressor, big inverter, lots of two way radios, etc. I'd get dual alt. There's really no negative other than cost. If you run a heavier charge line to the trailer a big depleted battery bank can draw a lot of power. If you don't upgrade the charge line and don't add electrical accesories I don't see much benefit.

[GordonThree]

missouri dave wrote:
I feel like an idiot. I didn't think of that. I was wondering more if there was a way to get it to charge the camper batteries while going down the road.

just charge yes... at what rate?? could be a mystery.

if you don't have a bank, well, don't bother with any of this.

now... lets say you have a 2nd alternator installed and can get it separated from the computer... you could run yourself a nice heavy welding cable from an isolator off that alternator (please don't use a diode, use a solenoid or mosfet switch) all the way back to your trailer battery bank.

you could also run a lighter piece of wire from the bank to the alternator's voltage regulator input (or just put a rheostat on it so you can dial-a-voltage)

[austingta]

missouri dave wrote:
I feel like an idiot. I didn't think of that. I was wondering more if there was a way to get it to charge the camper batteries while going down the road.

I researched this very topic here at some length last year and got some good insight. My Denali had dual alternators capable of 380A total charging.

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29105807.cfm

[pianotuna]

Consider adding an external diode to the existing alternator.

[missouri_dave]

I feel like an idiot. I didn't think of that. I was wondering more if there was a way to get it to charge the camper batteries while going down the road.

[agesilaus]

As far as I can tell with dual alternators if one fails you can run on the other one. So it seems to be for vehicles that must keep going, emergency services for example. I just got the heavy duty alternator.

I just looked online and it seems as tho these are for very heavy loads, once again emergency vehicles running lots of aux loads like those strobe lights or tow trucks that need the extra power to run various equip.