How to incorporate dual alternators

[mhiscox]

I also vote for a second alternator dedicated to the house batteries, which was the setup I ran on my Unimog camper. However, my second alternator was run off a separate short belt driven by a separate crank pulley mounted in front of the main pulley. I've no idea whether this is practical in your truck, but it is worth investigating as I believe this would be considered "best practice" when possible.

A second point worth noting is that most automotive alternators do indeed do poorly at deep-cycle battery charging, but it is possible to buy a marine-quality second alternator (Balmar is perhaps the most widely cited brand) that will do very well at charging the house battery bank. These alternators can be sized to match the battery bank size, which means they'll routinely be more like 70 amps than 150+, and they are very well built. Sadly, though, that's reflected in the pricing.

A setup that had a dedicated, properly sized, high quality alternator driven of a separate belt would be tough to beat if it was practical for your truck.

[witt]

Yeah, a separate belt/pulley would be ideal, but that would definitely require some non-standard modifications to the engine.

I'm running into two issues here:

If I install a Ford alternator (or an aftermarket alternator designed for the engine), the physical installation should be straightforward. However, the smart regulators (from Balmar and Sterling power) require a connection to the field terminal of the alternator. Do all alternators have that externally accessible? I found a wiring diagram for the Ford dual alternator setup conveniently posted online: http://www.powerstroke.org/forum/99-...out-there.html. Any idea which of the terminals on the alternator in that diagram is the field terminal?

Or if I go with a Balmar alternator and regulator, the wiring connections should be straightforward since they're designed to work together, but the physical installation would probably be harder since the alternator isn't designed for my engine.

I'm thinking that if I can figure out how to wire the regulator to an alternator that is designed for my truck, that would be the easier and cheaper way to go.

Thanks very much for everyone's input on this!

[dwh]

In that schematic, the field is controlled by the "sensing and switching circuits" (the (presumably internal) regulator).

The connections are A, B+ and I. The diagram has those labeled inside the border of the unit. But at the lower right, it looks like the wiring of the field coil connects to something that is outside the border and not labeled. Looks like an "O". [EDIT: I see they have the same dealy for the B+ connection...so yea...it might be...]

No idea what that is supposed to mean in that diagram. Could be an external field connection but no way to know without seeing the alternator itself.


Even if your alternator doesn't have an external field connection, it probably wouldn't be a big deal to have an alternator shop add a connector for you.

I'd call up or drop by a local alternator rebuild shop. In Denver...dunno. Maybe these guys?

http://www.yellowpages.com/denver-co...71?lid=5957771

[witt]

dwh,

Thanks for taking a look at that! I also sent the question to Belmar tech support and got a confirmation:

"Automotive alternators are internally regulated. You will need to take the Ford alternator to a shop and have them disconnect the internal regulator and bring the field wire out. The field wire can then be connected to the field output of the MC-614. The 614 would be just fine for your application. As to pricing, it would be best to contact one of our dealers in your area or find them on line."

[Ozrockrat]

OK I will play the devil's advocate here! Stick with a completely standard ford installation. You get the system monitoring of both alternators. Carry a spare "Short" belt in case of failure (although I have never seen an alternator catastrophically fail without plenty of warning. The only thing that will cause you to stop running is a failed bearing/seized alternator). You get to hear about that long before it goes to a seized state. If it happens put the short belt on (maybe move the 2nd alternator into the primary position).

Then do not run house batteries, parallel up the whole bank but install low voltage cutout master for all house equipment (I use mine to isolate all power when leaving the van parked for any length of time, Thieves would need to know how to turn the isolator on to get the van running). Ford also has a high idle option so that if you need a lot of power you can be running the engine at a ramped up idle as required for the current draw. (winching, battery charging, run the espresso machine for everyone )

Benefits

1. Quicker replenishment of all batteries.
2. Larger capacity for winching, engine starting.
3. Spreads load across all batteries evenly.
4. Less time in the critical discharge state resulting in longer battery life.
5. Any ford guy will know what he is looking at if you ever have problems.
6. Lowest cost solution gets you more fuel and miles traveled.
7. System monitoring of both alternators (can read the ford codes to see if there are problems)
8. Standard parts available from anywhere.

[mhiscox]

Ford also has a high idle option so that if you need a lot of power you can be running the engine at a ramped up idle as required for the current draw.

A small point that has nothing to do with the main argument:

I don't know enough about big Ford trucks to know if my experience is relevant, but for what it's worth . . . I paid considerable extra money to add high idle programming to my Sprinter camper so I could recharge the house battery bank off the alternator. But after a couple of experiments, I never used it because the noise of running my engine at 2K rpms with no load for many minutes was so annoying when camping. I ended up just carrying a small Honda generator and found that much less intrusive.

[witt]

Not sure about using all of the batteries in one bank - seems like I'd have to replace my two starting batteries with dual-purpose starting / deep-cycle batteries, and even then I'd be afraid to draw them down very far for fear of not being able to start the truck. Keeping it all stock Ford is appealing though.

I definitely agree about not wanting to idle the truck to re-charge the batteries. Had to do that with a previous vehicle, and found it annoying to me and anyone camped nearby (if we were staying somewhere for more than a couple of days there were usually other people around). The high-idle setting would be useful for winching, but I'm not a hard core wheeler, and may not even fit a winch.

In any case, I'm also going to put in some solar for when we're parked for a few days. We won't have domestic A/C or a microwave, so hopefully we won't need a generator.

[dwh]

The 3-stage external regulator from Sterling says it piggy-backs on the existing voltage regulator and if it detects an internal fault, shuts itself down and lets the stock regulator take over.

For that, you'd have the alternator shop add external connection, but you wouldn't disconnect the internal regulator as Balmer recommended.


(The Sterling has also got temperature compensation for the battery charging, and a temp sensor for the alternator as well. And an available remote control and monitoring panel.)

[FellowTraveler]

I fabricated second alternator/generator brackets for my 6.5 NAVISTAR its the top right unit they are controlled by ECU w/pulse width modulation(PWM) built into factory regulators then I did my own high idle PTO switch w/3 settings 1k, 1.3k and 1.6k all wiring is over built.

In the even of an alternator/generator bearing going south I just remove the long 2 alt/gen drive belt then bad alt/gen then top r/s1999 K2500 Burb 003.jpg idler pulley and make sure the good alt/gen is mounted at lower l/s of my diesel then attach the stock drive belt and go on my way, I like redundant.1999 K2500 Burb 001.jpg

[witt]

So after reading everyone's input (thanks!) and doing a bunch of research, I decided to skip the whole dual alternator thing, and go with a single high output / heavy duty replacement, as fastlane suggested at the top of this thread. My reasons are:

1. The second alternator runs off the engine's main serpentine belt, which is longer with the dual-alt setup. That means that even if I want to just bypass one of them temporarily, I have to replace the belt, and have a spare in the shorter length with me.

2. The second alternator seems pretty difficult to get to to install or replace - it would be easier to replace the one in the primary position

3. Expense of installing the dual setup would be more than using a single high-output (I'd be hiring someone to do it for me.)

Thanks again for all of the suggestions.