Any issues with installing a 100 amp alternator?

[jim.facey@gmail.com]

I was given a used 100 amp Balmar alternator, from a hurricane Sandy boat casualty that had been installed on an A4. I am not an electrical expert and want to make sure this won’t cook my batteries. Currently run two group 24, deep cycle batts (new this year) with a 7 watt solar trickle panel someone gave me.
I have the Moyer 55 amp alternator now. Alternator is currently removed in advance of new water jacket plate installation.

Thanks in advance for any advice

[Mo]

Neil would be able to give you a definitive answer on that. I have a 100 amp on my engine and its been there 13 or 14 years. Never had a problem and it throws a charge back into my batteries in a hurry. In those years I've replaced my batteries once, about 5 years back. The voltage regulator should cut back the charge once they come up.

This year we did 16 days on the boat and had no issues. I bought a suitcase 2500 watt generator as a backup but only fired that up to use the vacuum cleaner....otherwise, that 100 amp kept my batteries up. I did motor 92 hrs in those 16 days.

Otherwise, for two or three day overnighter trips no problem. My auto pilot would be running while sailing, no engine, interior lights at night after the sun set. Then just before bed I'd start the engine for about 10 minutes and it would throw charge into the batteries. Next morning motor maybe 10 to 15 minutes to get out into wind again and then shut down. No problem with power for autopilot, and other electronics. I have 2 deep cycle 24's and never had the need to put a solar charger on there.

Keep on mind, people use their boats differently as well. I generally day sail, that is the majority of my usage of the boat. Engine runs for 5 minutes at the most to get away from the dock and the same to get back, give or take. Battery power hasn't been an issue.

[ndutton]

There are no practical issues with a 100 amp alternator on an Atomic 4 engine. The charge rate - - - directly correlated to the alternator load placed on the engine - - - is determined by the connected battery bank size and its state of charge. Boats our size simply don't have enough room for a battery bank of excessive size so that possible issue is a non-starter. As for state of charge, you shouldn't be discharging your batteries below 50% before recharging for their own health. If the battery bank needs 35 amps, the alternator delivers 35 amps regardless of its size and the battery's needs go down as its state of charge goes up.

I have a 105 amp alternator and a digital amp gauge monitoring its output. I do not recall ever seeing a charge rate greater than 50 amps and it was short lived as the battery (bank) state of charge came up.

[TimBSmith]

Related to your water jacket work.....

Hi Jim,

I am digging into my heavily scaled water jacket after layup this fall. Been studying threads. Welcome any pictures and experience insights you have from new water jacket install you are preparing for. All the best with alternator switch. I inherited a 100 Amp alternator on my Pearson 30. I trickle the batteries and some aux usb needs with a 100 watt solar panel. My batteries are group 24 lead deep cycle. No problems and alternator brings batteries up to charge smartly after cold weather, not much work as running and mooring load is light currently.

[joe_db]

Most Balmars do not have regulators. How your batteries fair is entirely dependent on what regulator you install and how you configure it.
I am using the ARS-5 set to gel charging parameters. It has a temperature sensor for the alternator and another one for the battery. Do you know if you got a regulator as well?

[jim.facey@gmail.com]

I do not know much about the alternator, I don’t have external regulation now and would just be swapping in the 100 amp unit.

[joe_db]

I do not know much about the alternator, I don’t have external regulation now and would just be swapping in the 100 amp unit.

If it is one of the more common Balmar alternators, without a regulator it will not do anything.

[joe_db]

FYI - Balmar install

https://www.moyermarineforum.com/forums/showthread.php?t=10322&highlight=balmar

[jim.facey@gmail.com]

Thanks for the replies, just had a mechanic friend look at it, turns out it’s not a Balmar, it just was in a Balmar box, it’s a used Motorola 100 amp with internal regulation and could be quite old. I have decided to keep it as a backup

[Al Schober]

Re: alternator: Agree that you won't need 100 amps. Doubt if a single Gp 24 will ever draw 20 amps.
Side plate: clean the bolt holes in the block and install studs. You can use the Moyer kit or make your own studs. A 12" length of stainless 5/16 all-thread is more than enough for 8 studs. Use JB Weld to set them. Use a tooth pick to put some into the female threads in the block and onto the end of each stud, then just thread them in to the proper standout.