Dual Alternator Setup - Express 3500

[karma]

Hi, I have a 2013 Express 3500 Diesel. The engine has provision for installing a second alternator, I have the hardware to install it. My question is about how to wire the second alternator.

I'm wanting this 2nd alternator to charge the lithium battery bank via a Victron DC to DC converter. Should I keep the alternator as a standalone independent of vehicles ECM telling it how much voltage to make? Also have the alternator switched via ignition.

Any one done this on a Express or Savana van?

[Scalf77]

If going with a totally separate then you will need to use a external alternator regulator, such as Wakespeed WS500 or Balmar MC-618-H instead of connecting via a DC to DC charger

If integrating into your existing van electrical then you could use the DC to DC between the start battery and house batteries.

[karma]

Originally Posted by Scalf77

If going with a totally separate then you will need to use a external alternator regulator, such as Wakespeed WS500 or Balmar MC-618-H instead of connecting via a DC to DC charger

If integrating into your existing van electrical then you could use the DC to DC between the start battery and house batteries.

Thank you. If going with the van's existing electrical and letting the ECM excite the second alternator. Can there be a scenario where the ECM can limit voltage of the 2nd alternator to the house batteries based on feedback from the primary alternator?

[Scalf77]

So if controlled by the ECM there would be an expectation that the second alternator would be connected to the primary system. How they share resources could be done in a couple of ways. the easiest would be to just split the load.

I know on the Ford Transit dual 250 amp system, the second alternator is turned on primarily during low idle and if based on temp of primary alt.

The house battery load is never really seen by the alternator system, instead you will see a load from the DC to DC. It will be based on the capabilities and settings of the charger.

If using the second alternator independently then of course your output will be based on your settings of the controller and output of the alternator. Some care needs to be made that you do not provide more charge then the battery bank is allowed. ( This means you should take into account any solar charging at the time also)

With a independent system you are not putting any additional strain on your van alternator system.

[Pntyrmvr]

Hi.

I have a second alternator added in my van that exclusively charges the house battery. I use the exact same alternator as the engine battery system alternator so I can swap them in emergencies as long as I swap the driver too.

The key here is to put a relay that stops the house battery from feeding the house/auxiliary/second alternator's field circuit when the engine is off. Mine draws about 5 amps and that will drain the house battery. Just wire in a relay that cuts the feed to the field when the ignition key is not in the run position.

I used an adjustable Mopar style regulator and set it to the needed float voltage for the house battery with the engine running and all 3 big drawing appliances on- about 28 amps. (I run all 3 on propane when stopped so the battery runs lighting and cell phone charging only once parked.)

The battery is a 200 amp hour monster non vented beast (146 lbs) that is very fussy on maximum charge voltage. I got it free. 13.8 volts max seems low but it works.

Modern alternators use the PCM to set charging voltage via pulse width modulation. To use a modern one with the old school adjustable regulator you need to swap out the driver on the back of the alternator for one that is analog.

Call National Quick Start and tell them what you want to do. 616-785-7990

For belt length I used a ratchet strap wound around all the pulleys while the tensioner was pinned in the middle of its range. I ended up with the longest 7 rib belt made and had to downsize one idler for a perfect length.

Good luck with it.

G