125 amp alternator

I recently upgraded my battery bank to 8 golf cart batteries, its a little more than I need but I want to be able to spend the night without power and run both my fridges, icemaker and a small freezer. *
Of course I discovered that my alternators really are not big enough to charge the bank in a reasonable amount of time. I took a spare alternator to a local battery shop and asked him about getting a bigger one and taking that one on trade, he told me that he could take my 55 amp alternator and turn it into a 125 amp alternator for $140. Just thought I would share the information with you guys, I am going to install it today and test how many amps I really get out of it.
Has anyone else experimented with this?

So he*magically "turned" your 55 amp into a 125 amp???? Let's just say I'm doubtful A. that it'll produce that and/or B. it'll last.

Did you go to double belts? If not, it'll probably have such a load that it'll burn up a single belt in a heartbeat. All that amperage doesn't come free. How about ventilation? With the stock fan, it'll probably overheat and burn up.

Sorry I'm so negative, but sounds like you were sold a bill of goods on that one. There's a lot that goes into a high amperage alternator setup... check out Balmar's web site.

Negativity is good, it puts all different ideas out on the table to think about. No he didnt just magically wave a wand and say poof its 125 amp alternator.
They replace the stator, regulator*and the windings, its still a single belt. I will give it a try and see. I have done business with him in the past and always had good luck, it also has a warranty.
Even if it doesnt put out the full 125 amps, if I get 100 amps I will be happy. I really think you pay big bucks for Balmars name. Balmar also sells 100 and 110 amp alternators with a single pulley. I fired up the engine and put an amp probe on it and it showed 85 amps coming out of the alternator. I guess my point is if you can beef up two alternators for about $300 I would consider that before I spent $600 on a balmar.

Even if it doesnt put out the full 125 amps, if I get 100 amps I will be happy.

You can use a pipe wrench to drive a nail , abnd a rewinding will get a few more amps WHEN COOL.

The hassle with Alternators is the HOT (been on for 10 min ) rating is cooling dependant .
SO with a rewound you can get the old 55a that took cruise rpm , now lower , closer to idle.

So when you inch thru traffic that 200W boom box might not kill the battery , even with the lights on.

For a boat a rewind is not a solution (yes I was Balmar dealer , which then were simple rewinds from Les Tech) and they were not useful with a 3 stage regulator . Either the output was minor or they left with the smoke coming out.

The realistic HAMMER is simply a larger alt.

Yes its a bigger frame and will need 2 not 1 belt for 125+Amps of cont output.

A bit of welding for a bracket , and different front pulley from the engine folks is still cheaper than new batts every couple of years.

A truck supply will frequently have on sale (call ) a Prestolite 135A unit made by Leece Neville delivered with the pulley set of your selection.

FF

Having been down that road myself I have to agree that the single belt will not be satisfactory. It will run fine when you put it on and load it for a minute. It will seem to be just perfect until that morning when you get up and pull the anchor after 2 days on the hook. The batteries will be down and the alternator will try to charge them back up.

Even though you would be happy with 100 amps the alternator will try to put out 125 or whatever it's max amps is. The belt will squeal for a while while it overheats and eventually breaks. If you have a spare you will now be bobbing out in the middle somewhere replacing the belt so the water pump will turn again and not overheat the engine. If you don't have a spare then you'll get to meet the tow boat fellow.

Now the other thought might be to tighten up the belt so tight it can't slip. This puts so much pressure on the water pump bearings and the alternator bearings that they wear out prematurely. Maybe you're lucky enough to have a system where only the alternator is running on the belt and you'll only damage the bearings in it and could still drive home without a charging system. But you'll still be spending time replacing belts and not have a reliable system.

Ideally you want an alternator that gives you the rated output safely and without added maintenance. About 70 amps is the maximum for a single belt. The car manufacturers don't double belt high amperage alternators because they look "cool". They do it for reliability. I think most boaters agree that a breakdown on the water, even if you can fix it yourself, is not part of the cruising experience you look forward to.

Just my thoughts,
Ken Buck

2bucks wrote:

About 70 amps is the maximum for a single belt. The car manufacturers don't double belt high amperage alternators because they look "cool". They do it for reliability. I think most boaters agree that a breakdown on the water, even if you can fix it yourself, is not part of the cruising experience you look forward to.

Just my thoughts,
Ken Buck

Click to expand...

Balmars FAQ page states 110 amps is ok with a single belt. I kind of doubt I will see the full 125 amps out of this alternator.

From Balmars site: (http://www.balmar.net/Page46-faq.html) "Keep in mind, the width of the belt limits that belt's horsepower capacity. As a result, any belt -- no matter what quality it might be -- will fail before its time when the alternator load exceeds the belt's capacity. Once again, if the belt is narrower than 7/16", the maximum amperage load we can safely carry is 80 amps. If the belt is 1/2" wide, 110 amps is our upper limit. Any alternator in excess of 110-amp output will require dual belts."

Assuming that you have 1/2" belts Balmar says 110 amp is the "upper limit", which for me is different than "ok". No big deal, just your interpretation is different than mine. I guess I didn't understand how you planned to limit your 125 amp alternator to 110 amps, the upper limit for a single belt.

I'll be very interested in how this works for you long term. It looks to me like you have 3 people telling you it won't work out well. Maybe you'll prove us wrong.

Ken Buck

As a result, any belt -- no matter what quality it might be -- will fail before its time when the alternator load exceeds the belt's capacity.

AHHH what they didn't bother to tell was that when the belt fails , it doesnt SNAP.

It stretches and becomes soft from the heat of friction , the friction of slipping on the Smallest pulley.

That happens to usually BE the alternator , where the extra heat absorbed by the pulley , adds to the heat load of the hard working rewind.

SO belt failure usually means the smoke comes out of the fried Alt.

A 4 inch pulley solves the contact area hassle , but the lower speed running harms the charge rate Big time!

FF

Double sheaves, double belt?

DS

This would increase the contact surface on the smaller pulley, thus reducing the chance for slipage. Of course room to mount it would be a factor.

If you intend to USE 125A for hours of charging"

"Double sheaves, double belt? was your best answer.

FF

What I found out this weekend while testing this alternator is after the batteries were down to 12.0-12.1 volts, I fired up the engines and the beefed up alternator went up to 90 amps, stock alternator was about 45 amps. Then 60 minutes of run time the beefed up alternator was backed down to 78 amps and the stock alternator was down to 35 amps. *

*
IMO for $140 it works pretty darn well, it seems to be putting out twice the power of the stock alternator. I currently cruise at 1750 RPM with the stock crank pulley on a 80HP Lehman and the alternators have a 2.5 inch pulleys on them
I will keep a close eye on the belt. I currently use the Gates green stripe belts and I have seen the posts on Trawler Forum about the Gates Predator Kevlar belts. *I did not hear any slipping with this belt and the belt is not over tightened. I will be putting it to a good test pretty soon, boating season is in full force here on the weekends for me and I have a 10 day trip planned next month that will have quite a few stops at anchor or without dock*power.

Another response I received from Trawler Forum that seems promising.

*
I am using a single belt for the alternator running off a multi-sheaved pulley on my crankshaft.* I still use the standard Lehman single belt pulley arrangement that drives my fw pump and my small alternator that charges my starting bank and provides tach readings. Hope this answers your question.* Also, there is no "Mr." before my nickname "Tator" .

Troy Leek <troy994719@hotmail.com> wrote:
Mr. Tator
Are you using a dual belt set up or a single?
*
Troy





> Date: Mon, 31 Mar 2008 10:32:21 -0700
> From: pattitator@yahoo.com
> To: trawlers-and-trawlering@lists.samurai.com
> Subject: T&T: Beefing up Stock Alternator
>
> I would like to tell my experience with running a small frame 150amp Xena alternator with a single belt on our boat in Alaska.
>
> The alternator is sheaved off of the crankcase of our Lehman 120 with a Gates Greenstripe belt. We pull about 140amps out of it at 1600 rpm for hours. We currently have around 800 hours on the setup and have been extremely happy with both the alternator and the belting. We have no sign of belt wear. In fact, I will be adding an additional alternator to the other engine this year. The owner of Xena recommended this setup as the tightness (number of degrees around the alternator pulley) of the wrap coming directly off the crankshaft would give us enough grab. I can't remember the size of the crankcase pulley, but the alternator pulley is around 2.75". I am also unsure of the exact belt width, but I am sure it is at least 1/2" perhaps 5/8". We use an Xantrex three stage regulator. Later, Tator

So you really got a 90 amp alternator... I'd ask for a discount since it didn't hit the 125 amp mark as he promised.

Just kidding of course! A lot of difference in belt driving a 90 amp vs. 125 amp though....

Thats true, i am curious if its not spinning fast enough to make 125 amps.
With the amp probe it would put 55 amps out at 1000 RPM and go up with with the RPM's. 2000*RPM was as*high as I measured it at. I guess this would be a question to ask the guy that built it.
I really feel a little safer leaving it at just below 100 amps for a while and test this setup.

That's always been my understanding about the amp ratings on alternators, is that is would be rpm dependant. You could no doubt change to a smaller pulley on the alt and get the 125 amps, but why do that when 90 amps for that money is a bargain!

By the time I get back, You'll have this all tested out and I can try it. It's good not to be the guiena pig this time!

Seems to me that I read somewhere that the conversion to a higer amp alternator was accomplished by going to a higher ampacity on the diodes.
Yes? No?

In this alternator the diodes were also replaced, sorry if I forgot to mention that.

I know some of you showed some concern about the single belt setup on this alternator, so I have kept a close eye on it. Just a quick update it has 100 hours on it now and still looks new.

-- Edited by troy994719 at 13:20, 2008-06-20

Wow, that's a lot of hours. 100 hours in 2 1/2 months. You must be really cruising. It's too bad you weren't able to hit your goal of 100 amps much less the promised 125. 90 amps for an hour is good though and not eating the belt in 100 hours of use is even better. Your pulleys must be in great shape. I suppose the usage is important too. Are you cruising and plugging in each night or on the hook using battery power? If the batteries aren't down when you're cruising then the alternator is just loafing topping off what power you use under way and not really pumping out big amperage which is what would eat the belt.

Are you still guessing it's the pulley size that is limiting your output to 3/4 of what was promised?

I know, lot's of questions, but if you're onto something then maybe we can all learn.

Ken

Ken
*
I was on a 10 day trip that added 60 hours on the boat real fast, unfortunately I am back to the real world of working now!!!
The pulley might be the problem, although I dont know if the single belt can handle the load of 125 amps. The alternator shop did not ask me about RPM, if he had a gas engine in mind or possibly a diesel like Yanmars that turn higher RPM's that could cut down on output. If 90 is all I can get then I will take it. Next time I am down by his shop I will ask him.

I have ran the boat on batteries*tied up*without shore power while traveling,*running two DC refrigerators,the icemaker and freezer*off the inverter. The voltmeter was down to 12.1-12.2 range which means they were pretty much 50% discharged. I have 8 golf cart batteries, so the alternator was defiantly working hard. Its probably not as nice as a big Balmar with a three stage regulator but its a cost feasible idea for boaters on a budget. I am thinking about having the other one rebuilt the same way.



*

Unfortuniatly the alt industry gets away with rating their products cold,

after it works for even 5 min the hot rating is about 25% less than the cold rating.

FF

If I recall right he only got 90 amps even when cold, but it sounds like he has some good ventilation since it stayed at 90 for an hour.

Ken

Hi, I have a 165amp Delco Si either a 21 or a 27 that I ran on my Man with a 3/8 inch single belt/balmar ars4 regulator--high reading 65 amps on the link monitor. Now the same unit is on the Deere with a 8 row serpintine belt and it see's 90 amps on the monitor. Better grip

I dont know anything about the RPMs on a Deere, but you might want to check the ratio of the main crank pulley to the alternator pulley, it would be a shame to let a 165 amp alternator only run 90 amps!! If it was grip related and the old setup was slipping you would probably hear some squealing or at least see some black dust from belt wear.

You need a few things to get full output.

Obviously the alternator has to be 100% - all good diodes, brushes, etc.

It has to turn fast enough. 5000 RPM is a good target. You can figure that out by your cruise engine RPM multiplied by the ratio between the crank and alternator pulleys. A 3 or 4 to one ratio is going to be necessary for the tractor engine derivatives (Lehman, Deere, Perks, etc). But you have to be certian not to overspeed the alternator at engine redline.

The belt has to make it turn fast enough. Sometimes they'll make dust if they're slipping, sometimes they'll just glaze over and look just fine. If you have an external fan on the alternator and you can grab the fan and manage to get the alternator to turn, it's going to slip. Above 100 amps, dual belts are a good call if you're using V belts (I don't know what the power transmission capabilities of the flat serpentine belts are).

Using a handheld optical tach isn't a bad idea - measure the alternator speed at full load after it's run for a few minutes.

Then there's the regulator, the field voltage, and the wire between the alternator and the battery. To get full output, the regulator ideally should sense voltage at the battery, not at the alternator (like most internal regulators will). The field voltage is the voltage between the field termal and the alternator case - so if there is any resistance on the alternator ground path, that reduces the field voltage. For example, .01 ohm of resistance (which is very, very little) causes a half volt drop at 50 amps ... so the alternator case is actually at .5 volts, and the field voltage is reduced accordingly. With the alternator running at full output (or as full as you can get it), measure the voltage between the alternator case and the battery ground. Any drop there will result in a drop of output current. A solid ground wire between the alternator case and the main ground buss isn't a bad idea even if there's a solid ground to the engine block.

Finally, there's the wire between the alternator output and the main bus. A remote sensing regulator can compensate for voltage drop here, but only to a point. If you have drop, you're burning up a portion of your power output from the alternator and just turning it into heat. At 100 amps or more, #4 wire with properly installed terminals at each end carrying the alternator output is not overkill.

Temperature of the alternator is important, as FF points out. The magnetic characteristics of the rotor (which is just a spinning electomagnet) get worse as it gets hotter, and it gets hotter the higher the output. Plus the life of the diode assembly is inversely proportional to the temperature. If it's possible to duct some cool engine space intake air (without salt spray) to the alternator, it'll be just that much happier.

Finally (I've rambled too long, I know) -- conversion to a higher amp alternator is more than increasing the diode capacity. The rotor and stator magnetics have to be bigger in order to create enough magnetic flux to induce the greator current. The stator windings have to be big enough to carry the current without melting. Only then does the capacity of the diodes come into play.

" Sometimes they'll make dust if they're slipping, sometimes they'll just glaze over and look just fine."

Most alts are lost from belt slip as the HEAT of the small pulley is directed back to the front bearing ( which may be under high load to stop the belt slippage) and the front bearing is lost , or the extra heat wipes out something else.

FF.

I just joined this forum this morning and should sit in the background for a while, but...................

Increased battery charging capacity is not cheap or easy and must be designed with your boat's requirements*in mind.*I seem to need 200*amps per day on my GB-42 because**I am frequently an anchored out liveaboard.* Therefore I need to quickly charge my house bank to run my DC reefer and freezer not to mention my Sat TV and other goodies.* Last winter I left RI and headed down to the Bahamas and 7 months later returned home.**

My house bank of four 6 volt deep cycle batteries is primarily charged by a Balmar 200 amp large frame alternator which is double belted off the back end of my 110volt 8KW genset.* This alternator charges through a Xantrex smart regulator monitored by an XBM monitor.* The maximum hot charge I get is 140 amps which is darn good in my mind.* On my trip I ran the generator about 2 hours a day.* At the same time, I heated my water and charged my flashlights, I-POD and whatnot.**I also have a 1KW invertor to power my TV and microwave.

Just an idea.*

Howard*

The problem is unless a bank is HUGE , the recharge at 70% and up gets really slow.

I suggest you read Pro Boat Builder June /July 08 the Nigel Calder article on gen sets.

At the end there is a good look at more modern batteries that would perhaps with great expense allow you to reduce charge times greatly.

Batteries (wet ) haven't improved in 110 years , lets hope the vast sums being diverted into this research and Mfg facilities will help.

" I need to quickly charge my house bank to run my DC reefer and freezer"

Our solution was an RV propane reefer , mounted properly , so months of no powerhose and anchor out live aboard are possible in silence.

FF