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Author Topic:   Battery charger connections
conch posted 03-06-2010 07:49 AM ET (US)   Profile for conch   Send Email to conch  
I recently replaced my onboard hard wired 110/12v charger. My question is what is the preferred wiring for the positive 12v leads to the batteries? Presently (and I think original)wiring takes each positive lead from the charger to the on/off battery switch for each starting battery.Each switch must be ON to charge the battery from shorepower.Should the output positive leads from the charger go directly to the battery and NOT through the respective on/off switches?

jimh posted 03-06-2010 10:16 AM ET (US)     Profile for jimh  Send Email to jimh     
Regarding how the leads from an on board 120-VAC battery charger ought to be connected to the boat battery, and if the connection should be made via the primary power distribution ON-OFF switch:

On my boat I have installed a 120-VAC battery charger. The leads from the charger connect directly to the battery terminals. The setting of the boat primary power distribution ON-OFF switch does not affect the connection of the battery charger.

The only drawback that I can see to the arrangement I just described might be the chance that a very small reverse current flow though the charger would very slowly discharge the battery over long periods when the boat was idle but the charger was not powered ON. A very small reverse current flow from the battery back through the charger could, over a long period (perhaps six months), reduce the charge on the battery. Other than this, I do not see any drawback.

conch posted 03-06-2010 10:47 AM ET (US)     Profile for conch  Send Email to conch     
Thanks Jim,the only other reason I could think of was since there is presently no house battery,that the chargers 12v output could be used at the dock with the starting batteries unaffected to power all 12v house loads.

I plan on adding at least one house battery in the future so I installed a three bank 30amp hard wired charger from Charles Industries,totally quiet,no more loud hum.A very nice product.

To combine the start batteries if needed I have a paralleling switch at the helm.


jimh posted 03-06-2010 11:50 AM ET (US)     Profile for jimh  Send Email to jimh     
By the way, there might be other drawbacks to the arrangement I described that I just have not thought of.

In general I would say there are many ways to interconnect circuit elements on a boat. There may not be only one best way that fits all situations or applications. The overriding concern should be for safety. A circuit arrangement should avoid creating the possibility of dangerous connections if certain switches were set in a certain way. But as long a circuit arrangement does not contain inherent hazards like that, whatever works in a particular installation is probably fine.

conch posted 03-06-2010 12:17 PM ET (US)     Profile for conch  Send Email to conch     
Jim,I agree.Although I have 40 amp circuit breakers within a few inches of the wire termination at the on/off battery switch,it is nice to be able to shut off those 12v 8 gauge wires from stern to bow for maintenance etc. without having to disconnect them from the battery posts.
number9 posted 03-06-2010 11:51 PM ET (US)     Profile for number9  Send Email to number9     
I found this information in the Owners manual for my Guest two bank charger. Some of their chargers come in OEM version without output breakers. The last paragraph may apply to most chargers? Some to keep in mind when charging.

If the charger is not quipped with DC out put circuit breakers the ABYC requires an appropriate fuse installed on the positive battery connection within 6" of the positive battery terminal.

Output Cable Fusing: Guest recommends that all chargers be installed with an in-line fuse on each DC positive output per ABYC standards.

If the Guest Cruising Series charger does not come equipped with circuit breakers, an inline fuse must be installed in series with each DC positive output cable to the battery. This is to prevent catastrophic destruction of the charger in the event of reverse polarity connection.

2633A Connection Warnings: Do NOT connect the outputs of the 2633A in series or in parallel while charger is AC powered ON. Charge separate battery systems only. While charger is AC powered on, battery switch must be set to “OFF”, “1”, or “2”, not “both”.

jimh posted 03-07-2010 12:52 AM ET (US)     Profile for jimh  Send Email to jimh     
In my boat installation there is a fuse in the positive lead of the battery charger cable that connects to the positive post. Most chargers are configured this way. Thanks for the mention of the ABYC specification.
Bulldog posted 03-07-2010 03:55 PM ET (US)     Profile for Bulldog  Send Email to Bulldog     
Replying to your first post, I would take the battery charger connection to the battery terminals before the switch, use a fuse in the positive line. Option would also be to go to the battery switch, but hook the charger to the load side (battery side) of the switch, so when the battery switch is off there is no power going to boat circuits. If you had your boat plugged in and working on it, turning the battery switch off would kill everything , the way your boat is presently wired the charger would still be in the circuit even with the battery switch off......Jack
conch posted 03-08-2010 10:31 AM ET (US)     Profile for conch  Send Email to conch     
To be clear,I do have a 40 amp fuse within 6 inches of the charger termination at the on/off battery switch per ABYC requirments.
Jack(Bulldog) I think I will rewire as you suggest once I've added a house battery. Also moving the ring terminal positive lead from one side of the switch to the other will be very simple for me.Good idea.
Thanks Chuck
Bulldog posted 03-11-2010 07:50 PM ET (US)     Profile for Bulldog  Send Email to Bulldog     
Your welcome Chuck, your boat is my favorite model, just wish they made a smaller version for trailering easier. Someday I'll have a place on the Chesapeake with a dock......jack

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