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Topic: House Batteries (Read 1500 times) previous topic - next topic

Re: House Batteries

Reply #25 –
Worth it. FYI: I just saw a video from Mortons on the Move about using a 5 KWH Tesla battery at:

Overview of the Tesla Lithium Battery Module We are Installing in our RV -...

Here was my reply:

Mortons on the Move  Thanks for your video and reply. From one electrical engineer to another, I encourage you to do a service for all the RVers out there and perform a worse-cast power usage analysis. This would include:

1. Constantly running 24 Volt to 12 Volt converter and/or inverter with it's related losses
2. 30% loss of battery capacity after a certain amount of time: 3-8 years.
3. Running the battery DOD (Depth of Discharge) between 20 and 80 to maximize longevity
4. Boondocking under trees
5. Freezing temperatures and running battery and other heaters, like water pipe and waste water tank heaters.
    Keeping the pipes from freezing can use a lot of electricity.
6. Cloudy skies
7. Using high-powered appliances after dark.
8. Running a residential fridge.
9. Under-powered or dirty solar array. Use MPPT charger output power, not input power. I recommend 1200 watts minimum of input power. 1900 watts of input is preferable because there is alway loss due to sun angle, dirty panels and solar charger losses.

I have a 9.2KWH 48Volt pack with 1.9KW solar and the battery has gone flat on several occasions. I recommend that modern RV batteries have about 20KWH based on my real-world experience of one year with our system. This involved driving the rig at 55MPH at 10 degrees F and boondocking at Mammoth Cave, Big Bend and Death Valley National Parks.

That said, RVers can certainly live with 5KWH by cutting down on the power consumption, especially when the above worst-case conditions occur. This would require a compromise, which many power-hungry Americans will not be comfortable with. If an RVer "cooks on it" after dark, which to me means using a large electric appliance like an 1500 Watt electric stove or convection oven, it can take a dramatic toll on the batteries. My LiFePO4 batteries used to throw error codes in the Orion BMS because the cell voltage would drop to 2.9 Volts during heavy discharge. I resolved this by lowering the "weak cell" threshold to 2.3 Volts to account for heavy loads. So now we try to use our 1500 Watt convection oven when the sun is shining.
1997 U270 34FT Build 5140 Cummins 8.3 Allison 3060R
Solar 1920Watts, 14KWH lithium. Orion BMS.
 

Re: House Batteries

Reply #26 –
Quote from: Tim –
Worth it. FYI: I just saw a video from Mortons on the Move about using a 5 KWH Tesla battery
Cool video!  Thanks for the link.  I will watch the rest of the series, just for general interest.  Not a conversion I would attempt...too complicated.

If you used two of the Tesla batteries and wanted to "display" them, you could make a coffee table top out of them!  Great conversation piece!
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"