PW Excel Coach Battery Voltage Monitoring
Using the four red LEDs on the monitor panel near the 2012 coach entrance door to check the coach battery voltage did not leave me with a good feeling. Even at 12.4 volts, all four lights were lit; at 12.0 volts, 3 lights were still on. A plug in digital voltmeter for the Winegard socket near the television seemed a good solution; as previously mentioned in the group.
Without much thought, I bought a Model 12-2020 meter distributed by Prime Products. It seemed to work well when the alternator or converter was charging the battery, but during discharge the digital display would “hang up” as the battery voltage continued to drop. Prime Products replaced the meter, but the second meter acted the same way.
I moved on to an Equus 3721 meter; it seems to be a good voltmeter.
I wanted to find out if the battery was being used when the red handled disconnect switch is off. With both cables disconnected from the positive terminal of the stock Interstate SRM-24 battery and the red switch off, a meter between the positive terminal and the two cables showed that .0096 amps were going somewhere. The generator start / run and alternator charge line circuits are always connected to the battery; the small draw could be in their direction.
Turning the red switch on, the current reading increased to .33 amps. Users of this current include DVD player, TV, CO / propane detector, thermostat, rear air bag electronics, added socket voltmeter, and the two reading light switch locators. This is the base line current before the occupant turns anything on in the coach; such as lighting.
The most common load on our battery includes the above baseline plus refrigerator control current while running on propane. With the refrigerator on propane, the total battery current comes up to .46 amps.
During the above baseline plus refrigerator configuration, the added voltmeter reads .1 volts below the completely unloaded battery voltage at 12.4 volts. This gives me a better feeling about the state of the battery.
The CO / propane detector draws about .07 amps, the added digital meter about .006 amps. The above values depend on battery voltage, meter calibrations, battery condition, and probably other things, but it gives me a way to judge what the battery condition is. When I turn on lights and add additional loads, the meter voltage does not easily relate to unloaded battery voltage. Adding a meter directly to the battery and turning the red switch off would seem a more accurate way to check on the battery.
As mentioned, my coach battery is always connected to the alternator charging relay and generator starting / run circuits. The red switch needs to be on to charge the battery from the generator or shore power. If the transfer switch is wired per documentation, when connected to shore power, and the generator is started, the generator will supply the coach.
The plug in meter is great for following the battery charging stages from the converter. It also shows how the alternator is doing. The Progressive Dynamics PD9245c power converter includes its “Charge Wizard” to more efficiently charge and protect the battery. When we return home from a trip where only the alternator has charged the coach battery while driving, and then plug in to shore power and turn the red switch on, the Wizard charges at 14.4 volts until he thinks that the battery is up to 90% of full charge. Then the Wizard sends 13.6 volts to the battery; for 30 hours if there is no significant usage of the battery. Then finally, the Wizard sends 13.2 volts to the battery for the Storage Mode. Two to three days have gone by to get to this point. But wait, when I check my battery’s voltage after unplugging the Wizard, it is closer to 13.0 volts, not the goal of 13.2 volts, based on the 2.2 volts per cell capability of lead – acid batteries over the years. I find that if I let the Wizard work his 13.2-volt Storage Mode magic for several more days, the battery ends up with a good-looking charge closer to 13.2 volts. This charge, including any surface charge, above the commonly seen 100% charge of 12.6 to 12.8 volts adds to the time I can run things; sort of like the icing on the cake. My original battery would not charge above 12.8 volts due to a weak cell, as related in my post “Mr. Monk and the Weak Interstate Battery”, 08/03/13
Related to above:
Each light fixture with its 12 LED light sources; about .25 amps load.
Each of the two refrigerator cooling fans shows .32 amps on its label.
Every 21 hours in the Storage Mode, the Wizard will put out 14.4 volts for 15 minutes to help reduce sulfating of the battery plates.
12 volt “noise” to the television can turn it on; out of its standby mode.
The television on/off touch area is sensitive. When screen is covered, the television can be on without my knowledge. Power use and heat issues.
The alternator can top off the battery as we drive from home to the campsite, 14+ volts.
Not related to above:
I found a 120 v.a.c. duplex receptacle behind the microwave. This has been a good place to plug in battery chargers; the item being charged usually fits on the little shelf above the driver’s left shoulder. Out of the way.
Chuck Sorensen
Buellton, California
2012 Excel TS
Without much thought, I bought a Model 12-2020 meter distributed by Prime Products. It seemed to work well when the alternator or converter was charging the battery, but during discharge the digital display would “hang up” as the battery voltage continued to drop. Prime Products replaced the meter, but the second meter acted the same way.
I moved on to an Equus 3721 meter; it seems to be a good voltmeter.
I wanted to find out if the battery was being used when the red handled disconnect switch is off. With both cables disconnected from the positive terminal of the stock Interstate SRM-24 battery and the red switch off, a meter between the positive terminal and the two cables showed that .0096 amps were going somewhere. The generator start / run and alternator charge line circuits are always connected to the battery; the small draw could be in their direction.
Turning the red switch on, the current reading increased to .33 amps. Users of this current include DVD player, TV, CO / propane detector, thermostat, rear air bag electronics, added socket voltmeter, and the two reading light switch locators. This is the base line current before the occupant turns anything on in the coach; such as lighting.
The most common load on our battery includes the above baseline plus refrigerator control current while running on propane. With the refrigerator on propane, the total battery current comes up to .46 amps.
During the above baseline plus refrigerator configuration, the added voltmeter reads .1 volts below the completely unloaded battery voltage at 12.4 volts. This gives me a better feeling about the state of the battery.
The CO / propane detector draws about .07 amps, the added digital meter about .006 amps. The above values depend on battery voltage, meter calibrations, battery condition, and probably other things, but it gives me a way to judge what the battery condition is. When I turn on lights and add additional loads, the meter voltage does not easily relate to unloaded battery voltage. Adding a meter directly to the battery and turning the red switch off would seem a more accurate way to check on the battery.
As mentioned, my coach battery is always connected to the alternator charging relay and generator starting / run circuits. The red switch needs to be on to charge the battery from the generator or shore power. If the transfer switch is wired per documentation, when connected to shore power, and the generator is started, the generator will supply the coach.
The plug in meter is great for following the battery charging stages from the converter. It also shows how the alternator is doing. The Progressive Dynamics PD9245c power converter includes its “Charge Wizard” to more efficiently charge and protect the battery. When we return home from a trip where only the alternator has charged the coach battery while driving, and then plug in to shore power and turn the red switch on, the Wizard charges at 14.4 volts until he thinks that the battery is up to 90% of full charge. Then the Wizard sends 13.6 volts to the battery; for 30 hours if there is no significant usage of the battery. Then finally, the Wizard sends 13.2 volts to the battery for the Storage Mode. Two to three days have gone by to get to this point. But wait, when I check my battery’s voltage after unplugging the Wizard, it is closer to 13.0 volts, not the goal of 13.2 volts, based on the 2.2 volts per cell capability of lead – acid batteries over the years. I find that if I let the Wizard work his 13.2-volt Storage Mode magic for several more days, the battery ends up with a good-looking charge closer to 13.2 volts. This charge, including any surface charge, above the commonly seen 100% charge of 12.6 to 12.8 volts adds to the time I can run things; sort of like the icing on the cake. My original battery would not charge above 12.8 volts due to a weak cell, as related in my post “Mr. Monk and the Weak Interstate Battery”, 08/03/13
Related to above:
Each light fixture with its 12 LED light sources; about .25 amps load.
Each of the two refrigerator cooling fans shows .32 amps on its label.
Every 21 hours in the Storage Mode, the Wizard will put out 14.4 volts for 15 minutes to help reduce sulfating of the battery plates.
12 volt “noise” to the television can turn it on; out of its standby mode.
The television on/off touch area is sensitive. When screen is covered, the television can be on without my knowledge. Power use and heat issues.
The alternator can top off the battery as we drive from home to the campsite, 14+ volts.
Not related to above:
I found a 120 v.a.c. duplex receptacle behind the microwave. This has been a good place to plug in battery chargers; the item being charged usually fits on the little shelf above the driver’s left shoulder. Out of the way.
Chuck Sorensen
Buellton, California
2012 Excel TS
