Dual Alternator for Volvo Penata Diesel 2003 year 1989

"I need a 120 amp alternator t

"I need a 120 amp alternator to charge a 400ah house bank. I am considering a duel mount. I have the standard engine set-up with the stock 3/8” belt driving both the fresh water cooling pump and the existing alternator. My local Volvo shop says that changing from 50 to even 100 amps will cause too much tension for the water pump.

Does anyone have experience with Volvos additional top mounting alternator unit kit and bracket? The kit also comes with a Volvo standard 50amp alternator and a 3/8"-wide, and bolt-on 5” diameter pulley. Larger alternators require a ½” belt or wider.

I need some practical experience advice!

First, most simply, has anyone run a 120amp alternator on the existing mount with the stock 3/8” pulley and not wrecked the water pump bearings or seal? Has anyone upgraded to a 100amp alternator using the 3/8” belt and pulley and not wrecked the water pump bearings and seal? What has been your largest size upgrade 70 amps?

Second, similarly, has anyone run a 120amp alternator on the additional mount using the stock 3/8” pulley and not had to change the belt more than a few times?

Third, most properly, has anyone found a larger-width (1/2”) pulley from Volvo or aftermarket that can be installed using the stock threaded holes on the given engine pulley? This way a large alternator could be installed per guidelines.

Thank you, all advice and related experience welcome!

best regards!"

#1. what engine are we talking

#1. what engine are we talking about?
#2 1/2" belt on 3/8" pulley will just go away.
#3 that's one hell of a load. what are You doing?

"Thanks much,

Good questio

"Thanks much,

Good questions. Engine is a model 2000 3-cylinder known as a 2003. 400ah is pretty standard for a serious cruising boats of 33 feet. The actual daily burn is only 25-30% of that. It is recommended to discharge batteries to no more than 50% and to charge to 80% daily because of the absorption rate. Alternators should be from 25% to 40% of your bank so that charging time is only 1-1.5 hours. My daily load can be between 100 to 120 amps: counting electronics, running lights, radar, refrigerator, autopilot, etc.....Nigel Calder in his “Boatowner’s Mechanical and Electrical Manual” has great instructions on calculating all of this.

Regards,"

"I managed without any problem

"I managed without any problems 20.000 N m from Norway to Malaysia with my 3Gm Yanmar (28hp)and std factory alternator. Had a bank of 3 x 70Ah as house bank,1 x 70 as start. Running autopilot, navlights,fridge, radar when needed etc, but no air con!!!
I have seen and read most of the 'expert advices' including the one You mentioned. When it comes to charging batteries, the 'old' recomendation for std lead/acid is not to go above 10% amp charge of the battery capacity unless You want to 'boil' them. A std 55 amp alternator gives roughly 25Amps at 14 volts. When running radar, I allway let the engine idle around 1000rpm. My original battery pack lasted from 2002 until Dec last year, and then was replaced with a new set of std lead acids.
Look in the cruising harbors around the world and see what items cruisers are running around trying to repair: Charging equipment!!! Stay with the std and at least You have a hope of getting spares. Learn how to consume and recharge what You have and try to adjust to what You have within reason rather than 'kill' Your engine by making an electric powerplant out of it. Perhaps a solarpanel might be a better solution?"

"Morten,

Thank you for your

"Morten,

Thank you for your experience, what is the amperage on your alternator, 55 amps? Do you have a "smart" or "step" charging regulator? How is your starting battery wired and regulated?

best regards"

"It is the std Yanmar regulato

"It is the std Yanmar regulator, no fuzzy charging. The charge circuit is rather simple,Jeanneau factory standard. During charging (engine) both start and house bank are charged as one bank with an old fashioned relay kicking in when engine is started. In theory it give no charge voltage drop which a diode charge seperator will give. Browse my web page (click my name) and You find a rather complete test of the boat and trip. You may notice that I even brought a Honda 1000IE inverter, but that was more to the pleasure of others that had broken down their expencice and complicated charge systems and needed emergency recharge! I even have a 30W removable solarpanel which in general keeps the batteries (house bank) charged when I do not use the boat. Should I do any modifications in the system, I would probably change the nav lights to LED's. Present set up puls almost 35Amps during the night, LED's would pull less than 10!"

You can't run a 120 amp a

You can't run a 120 amp alt on a single 3/8 belt. You need a 1/2" or dual 3/8 belt setup. Sorry but I can't help with finding pulleys. I suggest an externally regulated alt with a 3 stage regulator like a Balmar unit.