We have one 100 watt panel, connected with 6’ of 10 AWG to the combiner box.From the box there is 15’ #6 to the MPPT charger, and an inline breaker before and after the charger.From the charger, there is 18” #6 to the battery bank.
Our budget did not include name brand panels or charger, so now I am wondering if the system is working correctly.Each morning the system is charging at 13.2 volts, but about 11am, it goes into bulk charge at 14.5 volts and 1.5 amps.It does this for about 1 hr, then reduces back down and lets the battery go into -1.5 amps for 10-15 min.The only big 12v draw on the system is the propane heater fan each morning…but this is ended by 11am.
My concern is the bulk charging every morning, but it has only been two days. What is the correct charging profile when connected to shore power?
Existing 12v system:
We have 4 Interstate 6v batteries and existing 120v charger and are staying at a RV park with shore power.We have a Trimetric battery monitor and prior to the solar install it read the battery system was 100% charged, and charging at storage level, 13.2 volts. (We’re been here a few weeks)
Thanks!
bjoyce said
03:06 PM Dec 26, 2013
Sounds like your controller is working. This is typical of a controller that does a mini-equalization daily, which some think is a good idea and others say it makes little difference. You set your charging profile based on the battery type, which is the charging voltage, float voltage, equalization voltage and the temperature compensation adjustment. You should check with Interstate for their recommendation for your particular battery model, it is probably on their website. If you have temperature compensation, you could see even higher voltages in cold weather.
Edit: More info from http://www.amsolar.com/home/amr/page_21: All lead-acid batteries begin gassing ('boiling') between 14.1 and 14.4 volts when the batteries are at 25'C (77'F) degrees Farenheit. (note: some batteries want to be pushed to 14.6 to 14.8 volts). It is important to note that this gassing threshold changes as the temperature of the battery changes. The gassing threshold is reached at a lower voltage when the batteries are hotter, and it is reached at a higher voltage when the batteries are colder. It is also important to realize that RV batteries are exposed to widely varying temperatures as they are not in climate controlled, insulated compartments. This dictates the need to include temperature compensation into the charging strategy.
You will probably need to add distilled water to your batteries more often with these daily charge cycles.
-- Edited by bjoyce on Thursday 26th of December 2013 03:12:00 PM
cep1 said
04:03 PM Dec 26, 2013
Thanks for the quick reply and info...
I do have a temp sensor with the charger, and the area we are in is cold at night, 40s, and much hotter in the day, Las Vegas, so this should help.
I find the different voltage used by the charger strange. Right now, 2pm, it is at 13.8 volts and .6 amps at 75 degrees. I thought it be more consistent: Float 13.4, bulk 14.6
Bill and Linda said
04:22 PM Dec 26, 2013
Chris:
I think this is working to its capability. The charge rate you will see will be based on the current draw / demand from other 12 volt items in the trailer that are demanding power. As you will recall, the trailer will draw between .6 and 1.5 amps “just sitting there.” The amount of charge you will see on the Trimetric will vary depending on the amount of sunlight, the condition of charge of the batteries and the amount of current (amps) left over so to speak after the current draw of the trailer is satisfied.Putting all these variables together you can see charge rates vary all the time even from minute to minute.
The fact you see 14.6 volts tells us the solar charger is working assuming there is no shore power charger working.
With a 100 watt panel the most charge theoretically possible at 14.6 volt is 6.8 amps (100 / 14.6 = ~6.8) and that is assuming no cable losses and no demand from the trailer for current.
The voltages you see changing are likewise an indication the controller is doing its job.
I think you’re good.
Happy New Year to the both of you.
Bill and Linda
cep1 said
05:07 PM Dec 26, 2013
Thanks Bill for explaining the variation. That makes sense now. I was just worried that the Chinese charger was going to cook my batteries.
For Christmas, we purchased and installed a new 100 watt MPPT solar system. http://shop.windynation.com/jzv/p/339/100+Watt%2C+12+Volt+Polycrystalline+Solar+Panel+%2B+MPPT+Charge+Controller+Complete+Kit+for+RV%27s%2C+Boats+and+Off-Grid+Applications?p=YzE9OA==
Solar:
We have one 100 watt panel, connected with 6’ of 10 AWG to the combiner box. From the box there is 15’ #6 to the MPPT charger, and an inline breaker before and after the charger. From the charger, there is 18” #6 to the battery bank.
Our budget did not include name brand panels or charger, so now I am wondering if the system is working correctly. Each morning the system is charging at 13.2 volts, but about 11am, it goes into bulk charge at 14.5 volts and 1.5 amps. It does this for about 1 hr, then reduces back down and lets the battery go into -1.5 amps for 10-15 min. The only big 12v draw on the system is the propane heater fan each morning…but this is ended by 11am.
My concern is the bulk charging every morning, but it has only been two days. What is the correct charging profile when connected to shore power?
Existing 12v system:
We have 4 Interstate 6v batteries and existing 120v charger and are staying at a RV park with shore power. We have a Trimetric battery monitor and prior to the solar install it read the battery system was 100% charged, and charging at storage level, 13.2 volts. (We’re been here a few weeks)
Thanks!
Sounds like your controller is working. This is typical of a controller that does a mini-equalization daily, which some think is a good idea and others say it makes little difference. You set your charging profile based on the battery type, which is the charging voltage, float voltage, equalization voltage and the temperature compensation adjustment. You should check with Interstate for their recommendation for your particular battery model, it is probably on their website. If you have temperature compensation, you could see even higher voltages in cold weather.
Edit: More info from http://www.amsolar.com/home/amr/page_21: All lead-acid batteries begin gassing ('boiling') between 14.1 and 14.4 volts when the batteries are at 25'C (77'F) degrees Farenheit. (note: some batteries want to be pushed to 14.6 to 14.8 volts). It is important to note that this gassing threshold changes as the temperature of the battery changes. The gassing threshold is reached at a lower voltage when the batteries are hotter, and it is reached at a higher voltage when the batteries are colder. It is also important to realize that RV batteries are exposed to widely varying temperatures as they are not in climate controlled, insulated compartments. This dictates the need to include temperature compensation into the charging strategy.
You will probably need to add distilled water to your batteries more often with these daily charge cycles.
-- Edited by bjoyce on Thursday 26th of December 2013 03:12:00 PM
I do have a temp sensor with the charger, and the area we are in is cold at night, 40s, and much hotter in the day, Las Vegas, so this should help.
I find the different voltage used by the charger strange. Right now, 2pm, it is at 13.8 volts and .6 amps at 75 degrees. I thought it be more consistent: Float 13.4, bulk 14.6
Chris:
I think this is working to its capability. The charge rate you will see will be based on the current draw / demand from other 12 volt items in the trailer that are demanding power. As you will recall, the trailer will draw between .6 and 1.5 amps “just sitting there.” The amount of charge you will see on the Trimetric will vary depending on the amount of sunlight, the condition of charge of the batteries and the amount of current (amps) left over so to speak after the current draw of the trailer is satisfied. Putting all these variables together you can see charge rates vary all the time even from minute to minute.
The fact you see 14.6 volts tells us the solar charger is working assuming there is no shore power charger working.
With a 100 watt panel the most charge theoretically possible at 14.6 volt is 6.8 amps (100 / 14.6 = ~6.8) and that is assuming no cable losses and no demand from the trailer for current.
The voltages you see changing are likewise an indication the controller is doing its job.
I think you’re good.
Happy New Year to the both of you.
Bill and Linda
Happy New Year to you two, too.