300 Amp Excessive Amperage Alternator

[mersberg]

I bougth one used and mounted it to my Ex. I upgraded all the cables to 2/0 welding cable. I get 12.5 volts with the ign off. Ign on I get 13.6 volts. When I turn the lights and AC on I get between 13.2 down to 12.5 volts and the idle drops, if I rev the RPMs to 3000, I get about 13.4 volts. I can never get above 14 volts. Is the rectifier bad ? I believe the regulator is good because it charges the battery but just not as much. I could be wrong but I'm not certain. Could I replace the rectifier or even upgrade the diode(s) in the rectifier with better diodes and still maintain the 300 amps? I know RJMInjection sells 200 amp rectifiers that you could swap out with your 3G alternator and make it a 200 amp but I need all 300 amps for my amp setup.
http://rjminjectiontech.com/?p=7
http://fullsizebronco.com/forum/showthread.php?t=114609

 

[BrooklynBay]

Have the alternator tested instead of replacing parts at random.

 

[gijoecam]

300A continuous?? That seems like an awful lot, even for an amp setup. You need to consider additional batteries and capacitors to store that kind of energy. There's no way an alternator at idle is going to be able to supply that amount of current, and even if there was, there's no way it's going to feed that kind of current into a battery without the battery exploding.

-Joe

 

[mersberg]

Talked to Nate at EA and he'll replace the rectifier for $80shipped . I have 2
8D Batteried hooked up to a Phoenix Gold isolator. I have a Red Top up front for the starting and OEM electronics. I need about 290 amps for my setup. I really wanted to run 2 alternators and as you know there is not enough space. In my resaerch of alternator repair I found a couple options to rebuild to higher output 3G alternator. WAI a alternator company that owns Transpo another alternator company , sells 240 amp stators with upgraded rectifier, according to Troy of their Tech section told me that all I would need to upgrade my stock 3G alternator to a high output alt is to replace the stator and rectifier and keep the OEM rotor and regulator. So thats another option for us 3G owners.
http://www.wai-wetherill.com/products/partimage.cfm?wai_num=27-212-240
http://www.wai-wetherill.com/products/partimage.cfm?wai_num=FR2023SP

 

[PowerFord]

Explorer Alternator- 300 Amp Alternator or Not?

I joined this Forum in order to response to the question of a 300 amp alternator. I suspect that the alternator that mersberg bought is not a 300 amp alternator at all. I've experienced many suppliers of so called high amp alternators that claim that their alternators put out 300 amps and they might if the engine is reved up to 4000 rpm. But don't put out anything at idle. This sounds like the case if you only have 12.5V at idle. I would bet the stock alternator would perform better at idle- install it and see. The only TRUE 300 amp alternators I found were in a hybrid design from the guys at Nations High Amp Alternators They know Fords very well with there background in the Limo industry. If you have a serious need for power check these alternators out ---FAD ALTERNATOR I have a 2003 Explorer 4.6L that has a computer controlled alternator and their unit was compatible with the vehicle system. The alternator was massive compared to the 200 amp alternator I had purchased that was the same size as the stock 130 amp and the alternator did not fall on its face at idle. I ran both a 1/0 output with 300 amp fuse and 1/0 ground cable to alternator. No probems so far and Adam was very helpful an knowledgeable on the phone. I hope this helps.

 

[Doubt Incarnate]

smaller pulley?

 

[PowerFord]

300 Amp Alternator Smaller Pulley Help in OUtPUT

Most high amp alternators I've ever used did come with a smaller diameter pulley than stock. Smaller pulley=more rpms at the alternator=more amps at idle. --- Voltage is another thing though. If your alternator only goes to 13.2-13.5 even when its reved up you may have a problem. Most OEM voltage regulators will charge about 14.5 -14.7 cold and 13.9-14.25 hot. Compare the cold Volts to the hot volts- The cold volts will always be higher. The only way to get around that is to install an external voltage regulator that has an adjustment. Higher voltage- especially when hot will not be good for your battery unless you have an agm or sealed non acid battery.

 

[joecrna]

Been doing a ton of work with batteries and charging systems (solar, wind, generator, alternator and shore power) on an RV lately. The above voltages all seem correct. Having said that, my Ex shows 13.68 volts at idle and 3000 rpm. That battery survives fine but 13.6 volts is more of a float charge. At acceptance it should be closer to 14.4v and at a bulk charge rate even higher.

Your original question points to a poorly functioning regulator. The voltage drop under load (lights and AC) should be very temporary and then return to baseline. If it doesn't, you aren't putting out the required amperage either. I've seen 300 amp alternators on big rigs (measured with a Dakota Digital ampmeter) but seldom do "high output" automotive alternators ever deliver anywhere near their rated power.

For a stereo system to require 300 amps continuos you'd be putting out 3700 to 4000 watts continuous. WOW!! At transients definitly but continuous? My Cinepro at home only handles 3000w continuous. You've got one radical system. You definitly need caps for the transients and more batteries.

Please tell me, why do the audio guys all use gel cell or occasionally AGM batteries. I know they mount in any direction but they really aren't ideal for this use. They are extremely sensative to charging voltages and drain. That is if you want them to last. A couple golf cart, or better yet fork lift batteries, would give you 230-350 amp hours. Depending on the brand, thats an hour or more of continuous drain at max volume with your system. No need for a larger alterator at all. Yes they are a little bigger and heavier but it seems like an easier solution. There must be a reason. If anyone knows, please enlighten me.

 

[mersberg]

Well this is not for a stereo system, its for a communication system. I am going to get this Excessive Amperage alternator repaired I will be happy as long as it puts out anything over 220 amps. I am lookin at taking my Compressor out and fabbing some brackets to put the EA alt in its place and split duties for the 2 alts.

 

[XxxMonoxideChild]

my advanced auto alt puts out a very solid 14.6v at a normal idle. and thats with a OHm meter reading it.

possibly the rest of your wiring is slacking, and needs to be updated also?

 

[budwich]

My take... you need to checking things with "no load", "moderate load" and "high load". When you are just "communicating" with your AC and headlights... , you shouldn't be seeing the kinds of drops that you are experiencing if things are working.... probably an alternator issue ... BUT loads from "dead cells" in battery packs can also be an issue along with poor (resistive under "electrical stress") connections. Start checking things by going first with just "stock load"... light load... (ie. one primary battery and lights / AC.... no isolator, no battery "string"). Take measurements at idle and then at rev. Repeat the test by adding the isolate only and one battery. Again take measurements and compare. Then repeat with the other battery (this will help rule out a battery cell issue). Finally, put your "system" totally back and take measurements and compare. Hopefully with the added info, you will be able to narrow down "weaknesses" / problems. As was mentioned, I think that your are expecting a "little much" out of your alternator without a corresponding "battery sink" to help the load.