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Externally Regulated Alternator for Atomic 4

15K views 23 replies 8 participants last post by  Omatako 
#1 ·
I am looking for something in the 55Amp range thats externally regulated...

Problem is I dont want to spend the Balmar or AmplePower $$$.


I saw a few places selling internal to external conversion kits for other alternators.... does anyone have experience doing this on an atomic 4?

I don't even know which ones will fit... ( i know small case 1" foot 3/8" pulley thats all)
 
#2 ·
Take any 55A alternator to any competent shop, or read some of the 12v "bible" type books. It takes less than a half hour to open the alternator, loop out the field regulator wire, and set it up so it can be externally regulated or switched back to the internal as a backup.

Really not a big deal.
 
#4 ·
I am looking for something in the 55Amp range thats externally regulated...

Problem is I dont want to spend the Balmar or AmplePower $$$.

I saw a few places selling internal to external conversion kits for other alternators.... does anyone have experience doing this on an atomic 4?

I don't even know which ones will fit... ( i know small case 1" foot 3/8" pulley thats all)
What are you hoping to achieve? Do you have Gel batts or AGM's that need a certain charge voltage? What is the output voltage set at on your stock alternator? How many Ah's is your battery bank?
 
#7 ·
230Ah golf cart batteries. I want to use a 3 stage regulator on them to keep them charged properly.

I am thinking the limit, power and belt wise is going to be 65 amps for my A4, at cruising speed it will prolly be more like around 30 amp output.
 
#5 ·
the old motorolas and prestolites that came on the A-4 were 30-35 amp.

if its one of those, take it to a rebuild shop, they'll tweek it out for ya on the cheep. :) have 'em rebuild it, and put on a bigger regulator. (within reason, remember, its a single pulley alternator)
 
#10 ·
Good point Jim. I personally don't have a problem with in on a diesel...
Nor would I, from a purely safety standpoint... unless the boat also had a propane system.

... and I don't know what the risk is on a gas motor.
It takes very little evaporated gasoline to create the potential for a tremendous explosion. I don't recall for sure, but it's something like two table spoons of evaporated gasoline in an enclosed space has the explosive power of a half stick of dynamite, or something like that? It's nothing to mess with.

I prefer gasoline engines, because I've worked with them for... well, for a long time ;). But in a marine application I'm paranoid as hell.

Jim
 
#14 ·
considering the vast majority of cruisers rarely if ever make it into float voltage stage your stock regulator will be doing just about the same for you as a three stage will and will likely be good money wasted.
I've come to the opposite conclusion, that a smart regulator will give you the most bang for your buck. The wanted feature for a regulator on deep cell batteries is not the float charge, but the bulk and acceptance charge. Dumb regulators aren't set up to do that. When we went from an internally regulated "automotive" type regulator to a smart regulator, there were noticeably more amps going in for a longer period of time.
 
#15 ·
i am trying to be realistic with my boat use (mostly weekends, every so often during the week) but no real cruise more than a weekend.

i dont think i run the engine close to enough to properly charge the batteries whether it had a 3 stage or a single stage.


My alternator replacement I have lined up is a 65amp with a single stage regulator which supposedly puts out 14.8v (kinda high I thought). maybe with the voltage drop to the batteries themselves it wont be too bad.
 
#16 ·
If you start with a Delco CS130D alternator, rated for 100+ Amp service, you may find that you can get "100%" output at idle as well as cruising speed. You don't need to spin it up all the way, or use the full output. But these alternators were designed to provide full output by about 2000 shaft rpm while the bearings are so robust they can run at 15,000-18,000 rpm in continuous duty.

Bottom line, is that you can use a pulley large enough to get high output at idle speed, and still not harm the alternator at "battle speed". Even if you never let it develop the full output.

I'm sure there are others that have a wide rpm range, I just know this particular one has an exceptionally wide range.
 
#17 ·
If you start with a Delco CS130D alternator, rated for 100+ Amp service, you may find that you can get "100%" output ...
You don't get something for nothing. The power to supply that kind of charging current comes from engine load. Now I wouldn't swear to it, but I think I read (here, probably) where somebody had put a big ol' honkin' alternator on an A4 and found, when the batteries were heavily depleted, he didn't have enough reserve HP to drive the boat against certain wind and current conditions?

Jim
 
#18 ·
Certainly true, Jim. That's why, with or without the restrictor plate that many A4's originally shipped with to beat hp tariffs, I mention that you might not want to run a 100A alternator at full rating on that engine. If I've got the math right, 100A at 14.4V would be 1440W which would be about two horsepower, maybe 2.5hp including losses, which the engine should be able to spare most of the time.

IIRC the A4 was derated to something like 15hp with the restrictor plate, and if someone had an old one in a bigger boat, with low compression and whatnot...

The point being, all alternators are not the same and picking one that can be mated up for your whole engine speed range SHOULD be possible.
 
#19 ·
Are extenral regs really necessary . . .

I'm busy rebuilding a genset that had a proprietary alt on it and I have removed that for a range of reasons and am replacing it with two ordinary alts.

Without wanting to go in a long description or explanation, the only alts that I could find with a reasonable output that would fit into the available space were Bosch units that have a continuous rating of 125amps per unit and I will be running two of them.

They have internal regulators that will have the old problem of tapering the charge off long before the batteries reach float and I was contemplating having them modified for an external reg and then using a NextStep or similar.

I have more recently been wondering if, given the fact that the genset can run for longer without being a noise nuisance and using significantly less diesel, I shouldn't just leave the regulators the way they are and charge for an hour longer. It's all about money at the end of it all.

What do the experts think?
 
#20 ·
Are external regs really necessary . . .

for all applications?

I'm busy rebuilding a genset that had a proprietary alt on it and I have removed that for a range of reasons and am replacing it with two ordinary alts.

Without wanting to go in a long description or explanation, the only alts that I could find with a reasonable output that would fit into the available space were Bosch units that have a continuous rating of 125amps per unit and I will be running two of them.

They have internal regulators that will have the old problem of tapering the charge off long before the batteries reach float and I was contemplating having them modified for an external reg and then using a Next Step or similar.

I have more recently been wondering if, given the fact that the genset can run for longer without being a noise nuisance and using significantly less diesel, I shouldn't just leave the regulators the way they are and charge for an hour longer. It's all about money at the end of it all.

What do the experts think?
 
#22 ·
They have internal regulators that will have the old problem of tapering the charge off long before the batteries reach float and I was contemplating having them modified for an external reg and then using a Next Step or similar.
Most internal regs these days are set at higher than the old 13.8 that gave them the "tapering charge" moniker. Some internal regulators turn off and on when this set point is reached based on battery need. Some do not turn on and off and will continue to put out a very small amperage, based on acceptance, usually under 1% of bank capacity, at the voltage set point.

Many I have measured are set at 14.2-14.4. I have done side by side comparisons of the identical alt running a stock but adjustable reg (the Leece-Neville reg pictured earlier) vs. a multi-stage reg set at the same voltage and they both performed within minutes of each other. I have had three Balmar regulators fail so had lots of opportunity to compare back and forth between the dumb regulator and the "smart" one.

Single stage regs simply try and reach a voltage set point but until that point will output what the batts will accept. From 50% SOC to 80% +/- SOC, the rage most cruisers are using, the dumb regulator will perform nearly identically as a smart one. At about 80% the older style regs with a set point of 13.8 will not fully charge the batt unless you ran it for a LONG time but one set at 14.2 will..

Those Bosch alts may be set at 14.2-14.4.. Of course if you run AGM or Gel batts a multi-stage reg is a very worth while investment..
 
#21 · (Edited)
I can speak highly of Ample Power. It is still on there and still charging after 18 years. It has probably worked out cheaper in the long run.

I had a reserve 100 A alternator (not Ample Power) that lasted one afternoon. I kid you not. One afternoon. It cost me $75 back in 1982. I never even pulled much load off it, perhaps 50 A, and not for long.

I have no latent interest in Ample Power.
 
#23 ·
I'd suggest it isn't just the voltage that's to be looked at. For instance, the Delcotron's will *only* put out 14.3-14.4 volts, no matter what the battery voltage is. There are other alternators that work the same way, using pulse width modulated DC and only putting out 14.4 volts and varying the "number of zaps per second" that they give the battery. So while the alternator is running, a simple voltmeter may only see 14.4 regardless of battery voltage.

IIRC a conventional car alternator cuts down to about 10% of full output within 15 minutes, so running it for an extra hour might mean you have run it for 3x-4x as long as you could have run it, with a real regulator applying full output for a much shorter period. I'd go for external regulation, or at least find out for sure how your Bosches were making decisions, and perhaps just install a manual override so you could get full charging from them. (i.e. fool the sensing wire, and in the alternator outputs are combined, make sure there's just one sensing wire controlling them both.)
 
#24 ·
Thanks for that - so I will continue to develop the genset mods with the alts the way they are then when it's running is the time to do some tests and then decide on the mode of regulation.

I have no gel or AGM, only flooded cells (Trojan 105's).
 
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