Experiences with battery isolaters?

[danielgoldberg]

Our Bene has four battery banks. One for the genset start, one for the engine start, the house bank, and one for the bow thruster.

The genset is entirely on its own circuit, and is charged from the genset alternator. Not connected to anything else on the boat.

The engine start likewise is on its own circuit, but gets charged via echo chargers on the battery charger (Freedom 30) and the alternator.

The bow thruster battery is on the same circuit as the house, but it's isolated using an isolater so that it's charged whenever the house bank is charged, but in theory does not get drawn upon by house loads other than the bow thruster.

This is a bit more complicated that we've set up on prior boats. Generally, I've kept it to two banks -- one to start the engine and genset, and one for the house that ran everything, with the banks separated but capable of being linked together in the event we needed to start the engine with the house bank.

I prefer our "old" method, if only because it's a less complicated setup and less to go wrong. But, considering that the new boat is coming wired the way I describe above, I'm not going to redo it out of the box, and am going to try to live with it for a while. The main area of question I have is how effective is the isolater for the bow thruster battery likely to be? I'm not overly worried about drawing on the house bank while using the thruster (which shouldn't happen anyway I guess) because we're not likely to be using the thruster except when the engine is running. But, am I going to find myself with an undercharged bow thruster battery?

Oh, all are lead acid batteries. And in case it matters, the house bank is made up of 4 4D batteries, and the bow thruster is a Group 31.

Thanks to you electrical gurus.

[k1vsk]

Not sure how much simpler you could make it unless you started combining the currently isolated systems which inherently would add complications. Notwithstanding, the isolator, if it is a true isolator, will only allow current in one direction - toward the thruster battery during charging. You can't draw down the house bank by the demand created from the thruster.

What you should consider is trashing the isolator in favor of a relay (commonly referred to as a combiner) to obviate the inherent 0.7V loss through the isolator to the thruster battery causing constant undercharge.

[btrayfors]

Or, better, use a Xantrex EchoCharge (15A maximum current flow) or a Balmar DuoCharge (30A max). These work by sensing a charging current on the house batteries, then diverting a portion of it -- up to 15A or 30A, respectively -- to the other battery bank to be charged.

The banks are kept separate, no significant voltage drop, no in-rush current when the batteries are "combined", etc.

Both devices work very well...we've installed both on many clients boats. And, they're "smart"...they won't overcharge your batteries.

Bill

[danielgoldberg]

Originally Posted by btrayfors

Or, better, use a Xantrex EchoCharge (15A maximum current flow) or a Balmar DuoCharge (30A max). These work by sensing a charging current on the house batteries, then diverting a portion of it -- up to 15A or 30A, respectively -- to the other battery bank to be charged.

The banks are kept separate, no significant voltage drop, no in-rush current when the batteries are "combined", etc.

Both devices work very well...we've installed both on many clients boats. And, they're "smart"...they won't overcharge your batteries.

Bill

Thanks Bill. The concern I have with the duo charge is that I already need that to charge the engine start battery from the alternator. My understanding, which of course could be way wrong, is that you can't use the duo charge to charge three banks. We already are going to have it set up so that the thruster battery gets charged on the Xantrex echo charger (it will be charging the house with the primary, and there are two additional echo chargers, one for the engine and one for the thruster). The problem is that we rarely will be running the battery charger when the thruster is in use, and I'd really like to have the altnernator propping up the thruster battery.

[btrayfors]

Dan,

This is beginning to sound like a "Who's on first?" comedy routine :-)

Sorry, I don't follow your logic.

The EchoCharges and the Duo Charge should be set up to sense any charging voltage on the house batteries, and to bleed some of that off to charge whatever other batteries they're connected to.

If there's a charge on the house batteries from the alternator, the generator, the battery charger, a solar panel, a wind generator, or a hamster turning a little wheel....it doesn't matter...then the EchoCharge and the DuoCharge will handle the task of bleeding off some power to charge their batteries.

Am I missing something here?

Bill

[danielgoldberg]

All that's missing is us determining whether you're Abbott or if I'm Costello.

The issue is whether the echo/duo chargers can bleed off into more than one additional bank. If it turns out that we can use a Balmar duo charger to charge both of (i) the engine start battery, and (ii) the thruster battery, on top of our house bank getting charged by the alternator, then I guess that could be my solution.

But, my understanding is that the duo charger can bleed off current for charging only a second bank, not a second and a third.

[btrayfors]

Dan,

:-) :-)

Yes, the DuoCharge is meant to maintain ONE other battery or battery bank. The EchoCharge is also meant for one other battery.

I don't see why you couldn't use two such devices, though. I'd probably put an EchoCharge on my start battery (like I've had on my boat for several years now), since the start battery requires very little charging to stay topped off; and put the second device -- larger like the DuoCharge if you like -- on the bow thruster batteries, because they're likely to eat a lot more AH than your starter will take.

Note that when the bow thrusters are in use, or any other load exceeding 30A, the DuoCharge will not supply current but will shut down for a short time, then will test to see if the heavy load has been removed. If so, it will begin normal charging operation.

Bill

[sailingdog]

Some battery chargers are designed to handle multiple banks. For instance, the Xantrex Freedom 20 inverter/charger has two "echo" charger connection points, and can charge THREE banks without any trouble.

[danielgoldberg]

Originally Posted by sailingdog

Some battery chargers are designed to handle multiple banks. For instance, the Xantrex Freedom 20 inverter/charger has two "echo" charger connection points, and can charge THREE banks without any trouble.

Absolutely, and we'll be setting up our Freedom 30 to "echo" the engine start and the thruster battery. That's got limited usefulness to us, however, because we're not likely to have the genset, and thus the battery charger, running when we're using the thruster while maneuvering around docks and such. So, I really would like the have the thruster battery getting a charge from the engine alternator, as the engine will be running when the thruster is in use.

After doing some research and going round and round, I actually think Beneteau may have set it up in a reasonable manner (who'd a thunk it!) with the thruster battery connected to the house bank, but via an isolater so that it gets charge from whatever is charging the house bank, but it doesn't draw off of the house bank), so I think we're going to leave it for a while and see how it goes. If it turns out I don't like it, I think I'm just going to remove the thruster battery, get oversized cables and run the thruster off of the house bank. That way, I essentially have a two bank setup which is very easy to isolate and charge (leaving aside the genset start battery, which is going to live in its own universe).

[negrini]

Dan, you're not going to use your batt thruster that much, it is expected to be almost fully charged everytime you need, just like your engine batt. I think Beneteau did a good job here, as I don't like the idea of having the thruster on same house bank, indeed, I split my 3 banks into engine/resistive/inductive loads. Your thruster would generate a lot of noise in the line that could cause some disturbance on sensitive electronics, but that is just my crazy exageration and to be honest, water pumps and electric wc (and sometimes the fridge) used to mess my dvd, so I found a final solution.

BUT what I really designed wrong, was my genset having an isolated batt. Since its use is marginal if compared to engine, specially during winter, where we use the boat less frequently, no AC, short trips, etc ... I found it dead DOZEN times, that I just installed an isolattor from teh engine batt (just like your batt thruster) .... think about it.

BTW, saw your pics, how old's your boy ? My boy, 4 old, is very excited as our new Bene will arrive Charleston next Aug/12 after a long wait .....