Separate Alternator Rectifier For HOUSE Batteries

Count your rectifiers. If there are four pairs, OEM is obviously rectifying that termination. I personally disfavor unbalanced phases for the sake of the voltage regulator even if it is ECU contained. To keep this a bit less technical I have seen overheated phase windings due to a disordered phase 4 conductor. With a principal loading route still connected a total phase connection does not exist but amplified phase inequality due to small #1 vs Large #2 over long periods of time have impacts. I used to use TO5 30-amp rectifiers both anode and cathode connections to fully rectify the stator on Ford 3G and 4G units.

Disregard above question. I just realized that the pair of leads that is second from the right is attached to the "W" terminal which is often said to be an unrectified AC output for tachometer use. I guess that it is a fourth winding loop just for tachometer purposes. The other three pairs must be the 3 phases of AC generatedd in the stator.

I know this is an old post, but I am trying to figure out the wiring of my alternator to external rectifier.

Alternator is Mitsubishi 12 volt 115 Amp.

The stator has four pairs of coated wires attached to the rectifier bridge/voltage regulator/brush holder.

See photo of stator and (edit) FOUR wire pairs at .

Assuming it is a 3 phase output, how do I identify the three pairs that give the input to the rectifier and what is the fourth pair all about?

Thanks for any help

All is needed is an adequate 3-phase bridge rectifier with insulated base to affix to a finned heat sink.

Three phase terminals.

One positive terminal

One negative terminal.

If the rectifier has alternate or additional terminals, skip it. For all intents and purposes it is a gizmo not the real thing. I've perused eBay and saw lots of nice rectifier bridges. Plain 5-terminals.

MEXICOWANDERER wrote:
I've been venting about these things for years on this forum. The alternator 3 stator leads are tapped inside the alternator. Depending on the power rating of the alternator (3) 8 gauge or 6 gauge wires are run from the alternator to near the house batteries. ...


External Rectifier

Mex-

I’m cornfuzed, again. Looking at the wire diagram in the link, I see 6 wires (ignition included) needed to remote the Quicktifier. Which also brings up the question, why the need to connect the DC output of the box to the DC output of the alternator? Buffering?

TIA

What is this guy? An idiot?

Those four base mounting slots are to affix the rectifier bridge to a heat sink. A real one. A finned aluminum sink the size of a 120-amp rectifier-type battery isolator. The base of the rectifier bridge is insulated so no worries about stray voltage. ALLELECTRONICS.COM sells a nice large heat sink that would work fine. Use transistor/CPU thermal grease to thermally bond the rectifier bridge to the heat sink. Do not mount with fins vertical. If you have an alternator with a rectified wye stator use a pair of full wave bridge rectifiers to rectify the wye.on your new package. You'll gain a substantial amount of amperage
These are fun projects.

And don't forget to twist the three stator wires between the alt and remote rectifier. Electronic noise cancelling.

This is the bridge rectifier i want to use. I would like to avoid fans for cooling. Its claimed by the seller that it dosent require heat sinking. (Not sure thaat i buy that) But a heat sink is no biggie. So say the house batteries are at 12.2 and the engine battery is 12.5 Is the regulator going to see the 12.2 at the extra rectifier? Or will it see 12.5 or split the voltage bias? Here is the rectifier i plan to use.

Rectifier

With (3) 6AWG stator leads and the remote rectifier mounted a couple of feet away from the house batteries you can pass 200-amperes 20-feet with insignificant voltage drop.

House battery alt VR sensing is common on cruising sailboats but degradation of sensing voltage can play hell with a lot of stuff in an automotive system. At the least an overcompensation of falsely low sensed voltage can cause the ECU to go open-loop.

Remember, you can leave the vehicle rectifiers silicon and piggyback Schottky across silicon for the house rectifier. This usually yields an .8 vdc increase to the paralleled rectifier house batteries. Don't skimp on rectifiers! 70-amp DO-5 silicon paired with a 70-amp Schottky gives good safety margins. For class, triple the rectifiers by adding MOTOROLA MR-2535 AVALANCHE rectifiers which are the size of a 3-amp axial. Add a 470 and a .47 uf electrolytic cap on the OUTside of the rectifier housing. A brushless ball-bearing fan saves a lot of heatsink size. With 3-amp axial diodes, rectify two stator phases for totally automatic fan operation.

MEXICOWANDERER wrote:
I've been venting about these things for years on this forum. The alternator 3 stator leads are tapped inside the alternator. Depending on the power rating of the alternator (3) 8 gauge or 6 gauge wires are run from the alternator to near the house batteries. This box is installed and wired. The alternator will run about 25% cooler,the regulator and the rectifiers inside the alternator have all the heat relieved and the alternator will last a lot longer. These things are great, with a proven track record of improving alternator reliability and much improved charging ability to motorhome house batteries. The link points to a reasonably-priced external rectifier. The rectifiers in the alternator continues to power the chassis.


External Rectifier

Remote Mounted Alternator Rectifier

A separate additional rectifier relieves a great heat load off of a vehicle's alternator. What it does is develop DC power from the AC (stator) windings in the alternator. Exactly like the "diodes" do inside the alternator.

With a SECOND rectifier, an individual can power the house batteries. If the alternator is being used to say charge house batteries at 90 amps and recharge the engine starting battery at 25 amps, the alternator's "diodes" need only deal with 25 amperes of current passing through them. Instead of heating incoming air 40C over ambient, the temperature increase would be <5C over ambient.

The house batteries thence need no isolator. No solenoid, no blocking diodes, switches, or yadda. There is zero voltage drop, except of course at wire terminations and fasteners.

Voltage Regulation is automatically controlled because the AC leads present exactly the same voltage to alternator and remote mounted rectifier "diodes".

I have manufactured my own separate rectifier systems for 30 years. Only I take it one step further: I eliminate the alternator rectifier bridge as well to increase air flow.

I would personally choose the higher rated rectifier in the link above and then limit the permissible amperage to 130. The built-in fan would be the weak link, and by limiting amperage it would allow convection to help cool the aluminuim heat sinks.

MEX if i were to run a additional #2 wire from the alt to the selunoid would this cause the voltage to be senced by the house batteries? The idea is to have the house battery voltage control the regulator at the alt. Also paralling two 200 amp rectifiers off of ebay. They claim it dosent require heat sinks. Do you believe this would work?

MEXICOWANDERER wrote:
You may gain 30-amps. Most alternator voltage regulators use a thermistor in the integral voltage sense lead circuit. Start up cold regulated voltage set point may be 14.2 when the alternator gets hot the voltage may slump to 13.6. A cooler alternator is a happier alternator. Feeding ambient air forced with a fan through a duct tube to the rear of an alternator is a good though impractical sounding idea. But I like it :)

I was thinking of a 3 in flex duct running to the front grill to the alternator no fan like a CAI.