Battery charger upgrade on 3 bank battery system

[newbie-]

I have a 30 year old battery charger. It works just fine but I also picked up a new Magnum charger for a great price. I have 3 battery banks.

- Generator
- House
- Engine

House and Engine banks have a crossover switch generally set to OFF. The generator is separate and the generator has a smaller battery. Engine and house are 8D batteries.

My 30 year old charger is a 3 bank battery charger. So I believe it maintains all 3 banks separately. I suppose this allows for the use of different types of batteries as out of the factory.

The Magnum charger/inverter I purchased only has connections for 1 battery bank. And now it's sinking in that this may not work at all for me. Appears that I need a 3 bank charger for this system.

Is there a way to use the single bank Magnum charger? Or do I need to start over?

If I do need to start over.. I'd be really interested in what you guys recommend for a 3 bank solution.

[Stu Jackson]

Multiple bank chargers are becoming rarer these days but still made.


But you don't need one. You can use switches or VSRs (voltage sensitive relays). Yandina makes an automatic combiner which has a lifetime warranty and is bulletproof. Google Yandina combiner. BlueSea makes whast they call their ACR (automatic combining relays) a little more complicated, same concept.


You charge the house bank and use the combiner to charge the start bank when charging source is present, i.e., plugged in or alternator.


Don't know about the gen., I don't have one and don't know. Someone else will.

[Joh.Ghurt]

There are a few house battery chargers which have a secondary output for the starter battery. This might work well in your situation. Look in the caravan section for something like the Dometic MCA1215 or MCA1225 perfectcharge

Multiple battery charger systems often have the limitation, that all of them need to be of the same type and have the same charging profile. For this reason, it's often hard to charge your AGM and regular starter battery at the same time. I needed one of those, as I have 3 separate house banks and 2 starter batteries (motor and generator).

[newbie-]

Thanks. Researching all the suggestions.

I'm a little surprised the solution isn't more obvious and clear cut. I'm guessing the vast majority of all of us here have at least two banks of batteries. House and engine start. I'd almost expect for every charger to at least support these two.

[wingssail]

Originally Posted by newbie-

Thanks. Researching all the suggestions.

I'm a little surprised the solution isn't more obvious and clear cut. I'm guessing the vast majority of all of us here have at least two banks of batteries. House and engine start. I'd almost expect for every charger to at least support these two.

Essentially it requires two chargers to charge two different types (chemistry) of batteries simultaneously. At least two sensor sections, two voltage output sections, two timing sections, etc. Probably some sophisticated circuitry could handle it all but it seems a bit complicated and expensive. (Actually, when it comes to boats complicated and expensive seems to be an attraction. People brag about how fancy their equipment is.)

VSR's and ACR's, and various combiners face the same problem when connecting various chemistry batteries. At least DC to DC units only have to control one battery.

In my case, even with similar battery types in the house battery and secondary battery (engine start) I do not depend on a charger or combiner or voltage sensitive relay to control simultaneous charging. I do them separately and I manage it myself. When one battery it charged I switch the charger to the other battery. For your usage I would either have three chargers or use VSR switched. it seems a lot to manage manually.

[Joh.Ghurt]

Or you get a dual charger house / starter and combine the starter batteries with a VSR. That seems to be the most economic solution.

[sailingchiro]

I purchased ProMariner ProSport 20+ Gen 3, 12/24/36 Volt, 20 Amp, 3 Bank Marine Bat Charger recently. You have the choice of using 1, 2, or 3 banks. It wasn't terribly expensive. I only use 2 banks and has been fine.

[smac999]

You use both. You need to run new ac and dc wires to the inverter anyways. So just leave the old one as is.


Through I would replace the old charger with a new 3 bank.

[vpbarkley]

A DC to DC charger can charge bank 2 from bank 1.
A DC to DC charger can charge bank 3 from bank 1.
Each of the banks can be different chemistries.

I eliminated the generator bank on my boat. The engine, generator, windlass and bow thruster now use the same bank. That bank can be backed up by the house bank if necessary.

[bcboomer]

Blue Sea make an excellent 3 bank charger that is designed with an extra charge level called pre-float. I bought mine 6 years ago based on Rod Collins review. (Maine Sail, now Marine How To). Lots of adjustments although only 1 chemistry at a time.

[newbie-]

I've thought about eliminating the genset battery. It would get shed some weight too. But it's nice to have the genset start and charge everything if both house and engine got drained somehow. I.E. Someone forgot to shut off the crossover.

On shore power all the 12V electronics are powered by the battery/charging system. That's all the lighting, plotters, AIS, NMEA electronics, etc.. Some of the chargers are only 20A and that doesn't seem like it's enough to power DC circuits AND charge batteries.

Any thoughts on how many amps is a good range for a charger? I'm guessing at least 100A.

[bcboomer]

I have the Blue Sea 40 amp but I don't run any of the electronics while on shore power. It never works very hard.
You need to make a list of everything that uses 12 volts.
Your fridge will probably be the biggest draw while in the marina.
Assuming LED lighting you won't use much.
Your battery chemistry can influence the size of charger you need.













y

[newbie-]

Agreed.. I'll have to do the marhs to figure that out..

Fridge is 120v/12VDC so shouldn't be a problem.

But the electronics, routers, modems, monitoring equipment, audio, vhf, USB outlets, etc are all on 12v. I also want to make sure all 6 bilge pumps have plenty of power reserves.

[bcboomer]

Pretty fancy!
What is your boat?
How big is your battery bank?

[sailcrazy]

We initially had a similar setup....until 1 of the 8Ds shorted out and overheated, and using a cradle to lift that 170lbs of lead and sulfuric acid out of the boat-it slipped and fell back down! Never again! Now we use 6 Trojan T-105s, connected as 3 "batteries" and wired to a busbar for house power. We use a regular start battery for engine and genset starting, and it's recharged via a Balmar Duo-Charge off the house 3-batt system. In addition to the engine alternator, solar, and windgen all going to the 3-batt bank, we use a 3-battery ProMariner charger, with a separate let to each of the 3 "batteries individually. Sys works good, and has ever since I dreamed it up and installed it in 2002.