Which on board charger?

[Dave22q]

Boat occasionally used non 10-15 day cruises but mostly day sail with slip power. Have generator which I use to top up on cruises. Batteries are 1 starting, 3 house all AGM group 31. Old charger, prosport 20 (2 bank), may need to be replaced. I gets hot attempting to charge new fully charged batteries so I shut it down. It is wired 1 zone to 2 house batteries and the second to the 3-rd house battery. I am thinking 20A/ 10 per zone is plenty for an on board charger. Charging time is not a big concern. Anything less than 12 hours would probably be fine.

I am interested in thoughts on the need for a 2 or 3 zone charger and specific brand/model suggestions/ experiences. I am willing to buy what I need but hate to overspend when not necessary. My electrical expertise is limited and I am much more interested in making a good decision then extending my technical knowledge.

[a64pilot]

I have two, a 60 amp Sterling pro charge ultra and a Magnum inverter / charger at 125 amp.
I'd look at an inverter / charger as they are sure nice to have, and with an AGM bank to take full advantage of an AGM bank, you need a BIG charger. Cuts down on gen run time.
For just a charger I'm impressed with the Sterling

Sterling is three bank, Magnum charges one bank, whatever it is connected to.


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[athene]

I'd endorse the Sterling Pro Ultra (see https://cdn.shopify.com/s/files/1/06...76cfc5.pdf?706 for product info). The 20A model has three outputs, so you could even use it for keeping your starter battery fully charged as well.

It has a pre-programmed charging mode for AGM batteries and also temperature compensation, which is vital if you're going to leave the charger on for long periods while away from the boat. However, it also has an automatic desulphation mode, which you may or may not want to switch off for your own AGMs.

If you go for it, it's worth also fitting the remote display panel so you can see what's going on at a glance.

GORDON KNIGHT

[Stu Jackson]

Wiring a new charger From Maine Sail:

Marine Battery Chargers - Installation Tips & Considerations | SailboatOwners.com Forums and

Installing A Marine Battery Charger Photo Gallery by Compass Marine How To at pbase.com

[skipmac]

Unless your three house batteries are really small I would go much larger than 20 amps for a charger. I have a 70 amp and wouldn't mind 100. Especially with AGMs that can take a lot of charge the more you can get the better.

[a64pilot]

Originally Posted by skipmac

Unless your three house batteries are really small I would go much larger than 20 amps for a charger. I have a 70 amp and wouldn't mind 100. Especially with AGMs that can take a lot of charge the more you can get the better.

Bingo, if you go the Sterling route get the 60 as it's the biggest.
My AGM bank will accept both the 125 amp and the 60 amp charger in bulk charge at 185 amps for quite awhile, and supposedly high amp charging is good for AGM's, not bad on them.
Besides he said he charges with a generator, you can shorten generator run time some with a big charger, depending on if your going for 100% charge or not.

[smac999]

with an on board gen 20a is way to small. you're not even charging the batteries while using the boat with gen running. probably barley breaking even. get a 60a+