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Help on increasing the amps on a 50 amp w/IR
By cpirao, Section Homebrewed Electricity Posted on Sun Mar 14, 2004 at 07:48:47 PM MST
Help on increasing the amps on a 50 amp w/IR

I apologize in advance for the length of this posting, but you will be helping me a great deal in advising me on my ordeal.
I currently have a Prestolite 50 amp alternator, with an internal regulator, on a Westerbeke 30b (27hp) marine engine, which apparently delivers a maximum of approx. 40 amps, per the Westerbeke dealer. There is nothing "marine-like" about this alternator from an electrical perspective -- it is from a practical standpoint an automotive alternator set-up.
My dilema began when I started my quest to increase the size of my battery bank (amp/hr) to aprox 220 amp hours. These are 2 deep cycle golf cart batteries connected in series to attain a 12V output. The problem is my alternator, I've been warned that given the size of the increased battery bank that my alternator will not be able to keep up with the demand of the batteries if drained enough, and will not recharge quickly enough. The dealer and others have told me that I should definitely replace the alternator. However, this has proven to be difficult (from a sizing limitation perspective) and expensive, since I would have to also modify the brackets.
My question therefore is, can I have an auto shop increase the amps output without increasing the dimensions (especially the depth) of the existing alternator? Would they also be able to remove the IR and provide me with the ability to use an external regulator for more efficient charging (should I do this?)? If not, should I be looking to also modify the existing regulator? Please help !!!
Apologies once again for the lengthy posting and thanks for sharing your much appreciated and much needed expertise
Rgds,
-Chuck

Help on increasing the amps on a 50 amp w/IR | 8 comments (8 topical)

Re: Help on increasing the amps on a 50 amp w/IR (3.00 / 0) (#9)
by fremont on Mon Jul 26, 2004 at 05:39:48 PM MST

Chuck -

Don't know if you ever solved your power problem. I the same motor with 380amps of house batteries and another 80 amp starter (which I often put in a series via switch). A couple of things...first, I chose AGM batteries which hold charge longer when not in use, but also can absorb charge quicker then wet cell batteries. Second, I added a Balmer high output alternator that can deliver roughly 70+ amps for a charge (reality is at 2400 rpm, will product between 50 to 55 amps charge - I have link 2000 monitor to measure ampage, voltage, etc.). As for the bracket, I had Annapolis Yacht Sales/service customize for me. It works great!

Re: Help on increasing the amps on a 50 amp w/IR (none / 0) (#1)
by Demetri on Sun Mar 14, 2004 at 08:07:05 PM MST

Depends on how long your run your engine. If all you do crank it up for 20 minutes to move it to a different dock in the same harbor when your batts are low, no it won't work. If you take it out for a day cruising, you'll be just fine. I used to fully charge dead semi truck batteries(four batts at about 80ah each) with a 55 amp Delco belted to a 3.8 hp Tecumseh. Works fine, just takes a bit of time.

Demetri
Uncommon sense required.

Re: Help on increasing the amps on a 50 amp w/IR (none / 0) (#2)
by bob g on Sun Mar 14, 2004 at 09:21:52 PM MST

one of the problems you will encounter with the alternator is the regulator itself.

most if not all vehicle alternators are designed to taper the charge rate back fairly quickly. it may start out charging at 40 or 50 amps but will quickly taper to probably 15 amps or less very quickly, perhaps as quickly as 15 minutes.

basically this type of automotive regulator is poor for your intended use, it is a comprimise designed to quickly put back the amount of current that was used to start the engine and then taper back dramatically to keep from boiling the battery. The design works well with starting type batteries but is less than optimum for deep cycle charging.

go back to you marine dealer and look into what is call a charge controller for your alternator. These units bypass or replace the internal regulator and will keep the charge rate up to the higher levels while monitoring the battery bank for voltage, and for temperature. With the more sophisticated control the alternator will charge at a much higher rate, while monitoring the battery temp and periodically testing voltage at the battery bank.

do a search on marine charge controllers and check up them..

for what you are trying to do this is a good fix.

bob g

Marine Charge Controllers (none / 0) (#3)
by Norm on Mon Mar 15, 2004 at 05:25:46 AM MST

Sounds like a good fix for a lot of us...especially newbies at charging deep cycle batteries.
( :>) Norm.
( :>) Norm
[ Parent ]

Re: Help on increasing the amps on a 50 amp w/IR (none / 0) (#5)
by finnsawyer on Mon Mar 15, 2004 at 11:30:30 AM MST

You may be able to get a higher output stator. Try National Automotive Lines Inc. at http://www.natauto.com. Or (more useful) 1-800-428-4300.
GeoM

Re: Help on increasing the amps on a 50 amp w/IR (none / 0) (#6)
by jubalearly on Mon Mar 15, 2004 at 04:23:00 PM MST

Chuck, if I'm not mistaken that is the standard small frame alternator used primarily by Ford. I would call a local alternator shop (rewind, also starters, ask the Napa dealer if you can't find one in the phone book). If so, they were built in that size up to 90-100 amps. It would be easy to find one in the 65-85 amp range. Try this page http://www.prestolite.com/literature/tech/alts/8lha_InstallationInstructions.pdf or http://www.prestolite.com/pgs_support/support_0.php
You may have to cut & paste to get those to work. But there is a cross reference on that site that may help. -RussH

Re: Help on increasing the amps on a 50 amp w/IR (none / 0) (#7)
by Hank on Tue Mar 16, 2004 at 01:01:01 PM MST

Just a word of caution,

When they say "Marine" that usually means it has been altered for corrosion protection but more importantly, relative to alternators, starter motors,etc. they have been shielded from producing sparks. Many a boat has been blown to hell because folks used automotive parts rather then marine.

If this is for a boat in an internal compartment do yourself a favor, stay with "marine" type parts. Unfortunatly they cost (unjustifiably) much more but your life may depend on it.

Re: Help on increasing the amps on a 50 amp w/IR (none / 0) (#8)
by cpirao on Tue Mar 16, 2004 at 06:53:37 PM MST

You are correct -- i didn't even consider that...

I think what I may do is install a battery bank monitor to gauge the performance of the existing alternator as it relates to the size of the upgraded amp size. I think then I may be in a better position to determine where to turn...

Thx so much for everyone's advise

[ Parent ]

Help on increasing the amps on a 50 amp w/IR | 8 comments (8 topical)

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