Solar Charging Question: Wiring Configuration for two six-volt batteries

[MikeB]

I just installed two AM100-M, 80 watt solar panels with a HPVB-22B controller on our 17-foot Escape with two six-volt batteries. I wired the 12-volt contoller using the standard wiring configuration for two six-volt batteries in series: postive from the controller to positive for battery #1, negative from the controller to negative for battery #2, and bridge wire from negative on battery #1 to positive on battery #2. The controller reads 12+ volts, confirming wiring configuration is correct. (This is the same wiring configuration I use to charge the two six-volt batteries with an AC powered 12-volt charger in the garage.)

However, when I hook up the trailer wiring in conjunction with the charging system wiring (positive and negative from trailer to positive and negative on both 6-volt batteries), I get excessive sparking. Both wiring systems work OK independently, but not together. For those that have wired charging systems on the Escape with two six-volt batteries, "How did you wire your 12-volt contoller with your two six-volt batteries?". I need to troubleshoot the problem this week. We leave for a one month boondocking trip next weekend.

[GaryH]

If you're getting the sparking, it usually means something is turned on at the time. Could be the fridge, smoke detector, or really just anything else. You could tell this by (with battery & 120V disconnected) checking with an ohm meter, & turning switches on & off. Probably nothing to worry about though.

[keager]

Your hookup sounds correct. The two 6V batteries wired in series is a 12V battery, so, that part makes no difference. If you are plugged into shore AC power your trailer converter battery charger will be active. If you have sunlight on the panels the solar controller (another battery charger) will also be active. The sparks may be the result of having the two battery chargers at different voltages (setpoints will always be somewhat different) as you connect them together. It may not be harmful, but, I don't like the idea of having two chargers active on the same battery. While I don't know without understanding the design of the two controllers, I suspect one would cause the other to shut down without any harm (who knows, they might even share the load, seems unlikely though). At any rate, in my trailer I never plug the solar panels into the solar controller if I have shore AC power hooked up and vice versa. It just seems to me to be a bad practice to have the two battery chargers fighting over what voltage the battery should be at. Of course, at night it wouldn't matter ... 8)

Bill

[MikeB]

Minor sparks generally mean something is turned on. Excessive sparks usually mean charges in opposition. When hooking up a second 12-volt charger to two six-volt batteries you have a 50/50 chance of selecting the correct positive to positive and negative to negative configuration. I happen to choose the wrong configuration. In this case I chose positive to positive post on passenger side battery and negative to negative post on driver side battery.

Fortunately, a good friend of mine partially runs his yacht maintenance service out of my garage. It's always nice to have a certified marine electrician just hanging around the house when you need one.

We opened the breaker panel in the trailer and traced the wiring from the panel to the batteries. Three wires exit the panel, one positive, one negative, and one ground. Four wires attach to the batteries, one positive wire and one negative wire for each battery. The configuration is positive from the trailer to positive post on the driver side battery, negative from the trailer to the negative post on the passenger side battery, and ground wire split to the negative post on the driver side battery and positive post on the passenger side battery. The ground wire creates the bridge that puts the two six-volt batteries in series to create twelve volts.

We just reversed the wiring from the solar charger to match the configuration of the trailer. Both chargers now have positive from the trailer to positive post on the driver side battery and negative from the trailer to the negative post on the passenger side battery. We also reversed my bridge wire so that the negative on the driver side is connected to the positve on the passenger side. We also removed the the ground wire from the trailer that split to the negative post on the driver side battery and positive post on the passenger side battery. Having two bridge wires in the system is redundant. Both systems now work independently and together.

The HPVB-22B charger can be switched from "Dry Camp Mode" to "Shore Power Mode" when plugged in to AC. However, its probably best to just turn off the HPVB-22B charger . Hopefully I described everything properly. It's more difficult keeping my positives and negatives straight when writing than when wiring.