Solar Questions
I'm interested in adding solar power and lithium batteries to our trailer, but I'm getting lost in the weeds. For starters I calculated what I think would be our worst case power need (without u...
Forum Discussion
Sorry I made a typo....Boob Docker, you are correct, I read that you can get 30 AMP-Hours per day and not 30 Amps from a 100 Watt panel.....my bad. Is that a realistic assumption?
We have the typical RV propane/electric Dometic frig. The manual claims it draws 3 amps of DC power. I assume that is the DC draw when using propane....correct?
As for my power calculation, I wasn't planning to run the heat all day, just a couple of hours in the evening and morning if needed. We also have a small propane heater that we could use also. Having said that, we have no intention of camping off grid in really cold weather.
If we do get lithium batteries, I was planning to install them inside the trailer somewhere, possibly into the bottom of a lightly used cabinet or under the bed, but not outside. I know that I'd have to run all new wires. I read that these types of cells don't give off gasses like lead acid cells and they don't like to get very cold. So I thought putting them inside wasn't a bad idea. I also read that most lithium batteries have battery management systems (BMS) built in to them that allow you to almost fully drain the battery. From what I read the BMS will shut the power down before any damage can occur to the cell. So I was thinking that I count on getting 80 to 90 amp hours from a 100 AH cell. Is that not the case?
Based upon some of your responses I re-looked over my numbers thinking that I was way too high. Unfortunately I didn't have the frig running 24 hours, so my estimate went up! My new calculation is 180 Amp-Hours per day, so I'd assume 200 AH for safety. I included my power estimate below. I got most of power consumption numbers from the manual or off the appliances directly. Our TV and DVD only gave AC watts, so I had to convert them into DC watts. I read somewhere that you can get a fairly good approximation of DC watts by dividing the AC watts by 0.80. Is this true? So our TV and DVD draw a total of 72 watts of AC power. 72/0.8 = 90.75 DC watts. DC Amps = DC Watts/ 12 Volts. So 90.75/12 = 7.5 amps of DC. So if watch TV for 4 hours that equates to 30.25 AH of DC. If these number look off (high or low) let me know. The frig and the furnace seem to be the real draw. We are relatively new RVers so we're still learning.
TV & DVD = 30.3 AH (using and inverter for 4 hours)
Misc Lights = 5.0 AH
Furnace = 48.0 AH (4 hours at 12 amps)
Dometic Frig = 72.0 AH (24 hours at 3 amps)
Water Heater = 6.0 AH (6 amps for 1 hour)
Water Pump = 7.0 AH (7 amps for 1 hour)
Power Vents = 5.0 AH (5 amps for 1 hour)
Misc loads = 7.2 AH (LP and smoke detector, power awning use, antenna booster, etc)
Total: 180.5 AH
Assuming my power estimate is reasonable, how many 100 AH lithium batteries be needed to handle that load?
I am leaning towards a MPPT controller and pure sign wave inverter for the TV and DVD player, but I don't have any details on which I'd buy.
Lastly, I should have mentioned that we are definitely getting an inverter generator within the next few months. I'm leaning towards a 2000-2500 Watt unit just so I can lift it. The larger units (3000 Watt and up) are just too heavy. So I may even buy two smaller units and run them in parallel, so have AC.
I'm just starting to investigate solar and Lithium batteries. I agree that lithium's are so so expensive right now, I keep hoping that the prices to come down.
Thanks for all of your info!
We have the typical RV propane/electric Dometic frig. The manual claims it draws 3 amps of DC power. I assume that is the DC draw when using propane....correct?
As for my power calculation, I wasn't planning to run the heat all day, just a couple of hours in the evening and morning if needed. We also have a small propane heater that we could use also. Having said that, we have no intention of camping off grid in really cold weather.
If we do get lithium batteries, I was planning to install them inside the trailer somewhere, possibly into the bottom of a lightly used cabinet or under the bed, but not outside. I know that I'd have to run all new wires. I read that these types of cells don't give off gasses like lead acid cells and they don't like to get very cold. So I thought putting them inside wasn't a bad idea. I also read that most lithium batteries have battery management systems (BMS) built in to them that allow you to almost fully drain the battery. From what I read the BMS will shut the power down before any damage can occur to the cell. So I was thinking that I count on getting 80 to 90 amp hours from a 100 AH cell. Is that not the case?
Based upon some of your responses I re-looked over my numbers thinking that I was way too high. Unfortunately I didn't have the frig running 24 hours, so my estimate went up! My new calculation is 180 Amp-Hours per day, so I'd assume 200 AH for safety. I included my power estimate below. I got most of power consumption numbers from the manual or off the appliances directly. Our TV and DVD only gave AC watts, so I had to convert them into DC watts. I read somewhere that you can get a fairly good approximation of DC watts by dividing the AC watts by 0.80. Is this true? So our TV and DVD draw a total of 72 watts of AC power. 72/0.8 = 90.75 DC watts. DC Amps = DC Watts/ 12 Volts. So 90.75/12 = 7.5 amps of DC. So if watch TV for 4 hours that equates to 30.25 AH of DC. If these number look off (high or low) let me know. The frig and the furnace seem to be the real draw. We are relatively new RVers so we're still learning.
TV & DVD = 30.3 AH (using and inverter for 4 hours)
Misc Lights = 5.0 AH
Furnace = 48.0 AH (4 hours at 12 amps)
Dometic Frig = 72.0 AH (24 hours at 3 amps)
Water Heater = 6.0 AH (6 amps for 1 hour)
Water Pump = 7.0 AH (7 amps for 1 hour)
Power Vents = 5.0 AH (5 amps for 1 hour)
Misc loads = 7.2 AH (LP and smoke detector, power awning use, antenna booster, etc)
Total: 180.5 AH
Assuming my power estimate is reasonable, how many 100 AH lithium batteries be needed to handle that load?
I am leaning towards a MPPT controller and pure sign wave inverter for the TV and DVD player, but I don't have any details on which I'd buy.
Lastly, I should have mentioned that we are definitely getting an inverter generator within the next few months. I'm leaning towards a 2000-2500 Watt unit just so I can lift it. The larger units (3000 Watt and up) are just too heavy. So I may even buy two smaller units and run them in parallel, so have AC.
I'm just starting to investigate solar and Lithium batteries. I agree that lithium's are so so expensive right now, I keep hoping that the prices to come down.
Thanks for all of your info!
