Single or Multi bank charger with 1/Both/2 Use Switch

Maine Sail · Feb 22, 2015

Ebbing Lattitude said:
I have been digging through, and expect there is, but haven't found a specific post or topic on the appropriate charger configuration when following the 'use switch' recommendations for the 1/both/2 switch.

On my previous boat, which did not have an on board charger, I had wired her following the recommendations on wiring alternator directly to house, and using an ACR for charging the backup/ starter battery. This worked out very well, and I am now building upon that experience.

Where I am unsure on direction, is in this configuration, do I need a 2 or more bank charger, or is a single bank charger sufficient? I purchased my new Freedom 32 in the fall, and it has an old Flyback charger, which I have read the warnings about and I'm looking to replace.

Maine, if you've posted on this previously, would appreciate pointer to the article(s), or otherwise, your experience in this regard.

Just do what you did on the last boat. You only need a single bank charger if you use an ACR to charge the start battery. Feed charger direct to house bank and the ACR will take care of the start battery. This allows you to turn off the battery switch when you leave the boat but still have charging to both banks.

wheatfieldcrows · Feb 23, 2015

I have a lead acid starter battery and an AGM house battery on a dual bank charger when shore-side and the two banks are combined via an ACR when running the engine. Because the dual bank charger runs different charge profiles and equalization on the two different battery types (supposedly), I installed a relay that disables the ACR by disconnecting its DC neutral whenever the charger's AC circuit is energized. Obviously simpler to just use the single bank charger and an ACR, but not too much extra effort involved to let two banks be maintained individually when on shore-power.

Maine Sail · Feb 23, 2015

wheatfieldcrows said:
I have a lead acid starter battery and an AGM house battery on a dual bank charger when shore-side and the two banks are combined via an ACR when running the engine. Because the dual bank charger runs different charge profiles and equalization on the two different battery types (supposedly), I installed a relay that disables the ACR by disconnecting its DC neutral whenever the charger's AC circuit is energized. Obviously simpler to just use the single bank charger and an ACR, but not too much extra effort involved to let two banks be maintained individually when on shore-power.

Most multi-bank chargers one run voltage profile, have one power supply and treat all batteries with the same charge profile. They nly isolate the outputs via diodes to prevent back drain between banks. There are a very select few chargers that have true multiple outputs & multiple charge profiles but they are pretty rare. Tell use mode, brand etc. and we can tell you what you have...

wheatfieldcrows · Feb 23, 2015

I have a NOCO Genius GEN2 20 Amp 2-Bank Waterproof Smart On-Board Battery Charger. It supposedly "alters the charging process based on organic battery feedback." A little hard to believe and like you said may only do that for both banks at a time but the relay was easy enough to add. It does go into float mode for the starter while still in bulk mode charging the house battery. It would seem that combining the banks would screw up the voltage sensing by which it knows to quit bulk charging. Something I've worried about with the ACR is overcharging the starter battery when away from shore power. Given that the starter battery is hopefully never deeply discharged, does the ACR result in the starter battery being overcharged when the house bank is deeply discharged to something like 60% of capacity?

Stu Jackson · Feb 23, 2015

wheatfieldcrows said:
Something I've worried about with the ACR is overcharging the starter battery when away from shore power. Given that the starter battery is hopefully never deeply discharged, does the ACR result in the starter battery being overcharged when the house bank is deeply discharged to something like 60% of capacity?

Overcharging with Combiners or ACRs The MYTH:
http://c34.org/bbs/index.php/topic,7052.0.html

wheatfieldcrows · Feb 23, 2015

Good to know, thanks Stu. Would this mean that combining different size/type batteries into a single bank is also ok? I've heard that you should only use banks of batteries that are all the same type and size.

Stu Jackson · Feb 23, 2015

wheatfieldcrows said:
Good to know, thanks Stu. Would this mean that combining different size/type batteries into a single bank is also ok? I've heard that you should only use banks of batteries that are all the same type and size.

That's true, but not in the same bank. If your start/reserve bank requires a slightly higher voltage than your house bank, then it should be just fine. I understand people mix sometimes 'cuz their reserve is in a hard-to-get-to place and they stick an AGM there. Gels, of course, require a LOWER voltage and so shouldn't be mixed with wet cells.

The best resource I've found for battery charging voltages (in addition, of course, to the battery manufacturer's recommendations) is in the Balmar regulator manuals. www.balmar.net, download and read the MC-614 manual, it has a whole table of base recommendations for different battery types.

Maine Sail · Feb 23, 2015

wheatfieldcrows said:
I have a NOCO Genius GEN2 20 Amp 2-Bank Waterproof Smart On-Board Battery Charger. It supposedly "alters the charging process based on organic battery feedback." A little hard to believe and like you said may only do that for both banks at a time but the relay was easy enough to add. It does go into float mode for the starter while still in bulk mode charging the house battery. It would seem that combining the banks would screw up the voltage sensing by which it knows to quit bulk charging. Something I've worried about with the ACR is overcharging the starter battery when away from shore power. Given that the starter battery is hopefully never deeply discharged, does the ACR result in the starter battery being overcharged when the house bank is deeply discharged to something like 60% of capacity?

The Noco's are interesting in that they do have two dual outputs but they really lack any programability (because they are waterproof) so the batteries really need to fall into the 14.4 - 14.6V range in order to work well with them.

They are not well suited to GEL, obviously, but they can work for most AGM and flooded batteries, though Trojan and other deep cycle batteries prefer 14.7V - 14.8V.

Their water proof chargers also don't have temp compensation and don't do a true float. They cycle in and out of absorption and key back on at somewhere around 12.8V and go back to 14.4 - 14.6V, then eventually shut off again, drop to 12.8V and repeat the process.

Not the best choice for a boat running dock side DC loads but reasonable enough for charging unloaded batteries...... Also you don't really get a 20A charger you get a 10A & 10A but the start battery is taking 0.2A, or it is off, so the other 10A goes to waste. A dedicated 20A distributed by demand charger would give 19.8A to house and the 0.2A to the start via the ACR.

The ACR will not cause issues unless you are mixing GEL (14.1V) and AGM or GEL and flooded because one bank will either be over or under charged.

wheatfieldcrows · Feb 23, 2015

Totally agree that the Noco doesn't function as a dc power supply for house loads dockside. Thanks so much for your comments, I'm storing them for my next boat.

Benny17441 · Feb 24, 2015

The battery switch is to direct power to the loads and charging current from the alternator. Connect the charger output leads directly to the battery banks, with fuses of course.

JK_Boston_Catalina310 · Feb 25, 2015

Benny17441 said:
The battery switch is to direct power to the loads and charging current from the alternator.

If you are going to install an ACR, then run the alternator lead directly to the house/primary bank as well. Then the ACR can direct that charge current too. And you don't have to worry about switching for alternator charge current. If you do this, remember to fuse it appropriately and it's a good idea to add a service disconnect switch.