Wiring Path From Charger to Cranking Battery

[mkendrick]

We have discovered that there is no charge making it from a relatively new (May 2016) Mastervolt 12/20-3 battery charger to the cranking battery. We tested the charger and it is putting out a charge. We then put a volt meter on the tips of the [disconnected] brown wiring going to the battery and found no juice. This leads us to believe that the wiring is faulty. The next thing we need to know is the path of the wiring. Does anyone know how the wiring from the battery to the battery charger is laid? Is there an alternate route that we may use to get the charger back to doing what it is suppose to do? Any advice regarding this problem would be greatly appreciated.

[Aurelia]

The location of your charger would help us guess the wiring run. Ours was mounted originally in an interior Port side cabinet and ran rearward along that side of the cabin and cockpit to the Batteries in the Port Stern corner.

Also, the charger make appear to be charging, but without a battery connected to the leads, many chargers will not send a current anywhere.

Test the Battery voltage first, then connect those leads to the battery, watch the charger and give it a minute, and test for power flow again at that now connected battery.

Greg

[thataway]

The Mastervolt would be an add on--not a factory item. Who did it may have used the original wiring, or had used new wiring. Not only where is the charger but where is the battery. Usually the wiring is most direct--it will go into a loom. If the boat has 110 V from the factory, the original charger is most likely under a dinette seat, or under the galley.

Agree with Greg--Tell us where the charger is. I always carry about 20 feet of wire for testing (and some more for repairs if needed). Disconnect the wiring you have at the charger. You can take a "jumper" from the Plus and negative of the charger to the battery--for this you can use cheap #14 automotive wiring. If you were going to put in new wiring (which I probably would do, since the factory wiring is not heavy enough for that charger), I would use at least #12, duplex red/yellow; in vinyl sheath. (Ancor tinned, marine wire, or equivalent). Use a good ratchet swagger, and use adhesive lined shrink fittings or heat shrink each connetion--use some conductive non corrosive grease under each terminal. Be sure that the ring is the correct size (5/16 or 3/8 on the battery terminal, and #10 or what screw size on the output--it could be a clamp type--in that case I would tin the end of the wire with solder.

It may well be that there is a bad ground connection--I have found that just as often as it was a bad wire. Corrosion is the biggest electrical problem we see. At one of the gatherings, I found every single electrical problem was due to increased resistance due to corrosion of some degree.

Learning to use a good digital volt meter is one of the primary skills for electrical and electronics trouble shooting. Having jumper wires (I have alligator clips on the end of mine, so it is fast to do the trouble shooting.)

[mkendrick]

Greg and Bob: The charger is located on the port side in the same cabinet as the hot water heater. The cranking battery is on the port stern side of the boat.

Nice to know that the charger may not send a current unless it is connected. Also great to know that the factory wiring is not heavy enough to handle the Mastervolt.

The person who installed the Mastervolt charger documented the steps he took and the veteran boat mechanic I have helping me says he connected the charger correctly.

Unless the corrosion is on a hidden wire I don't think we have corrosion anywhere else due to annual cleaning of all connections and busbars and covered with electrical grease.

I just tested both batteries and they are now carrying 12.5 volts.

Don't have a lot of faith due to recent history that this charge will hold we have decided to replace the wiring once we know where the wiring is now located.

Can't thank you guys enough for the help you have given. Hopefully, the new wiring will fix the problem.

[thataway]

12.5 volts is not quite a fully charged battery. It should read 12.6 (AGM read 12.7) at rest. With the charger working, the float voltage should be 13.1 to 13.3.

The factory wiring will work (assuming the wiring is intact)--but you will have some voltage drop. I would rather have #10 or #12.

[Aurelia]

If you don't see the wiring along the cockpit port side, open the floor inspection hatches in the cockpit as they may have run the wiring over the gas tank rearward. The front corner of the cockpit where you have the small step, is a removable part that may shed some light on your wiring location as well.

Greg

[colbysmith]