Anyone researched Telsa's 7kW battery?

Really not too suitable for an RV as it is intended for grid tied and 240 volts AC. The $3000.00 cost does NOT include the inverter. It appears that the inverter is another $3000.00. By the time tax is paid we are at $1.00 per watt for this storage solution.

Further the voltage for the actual powerwall output from a dc to dc converter is between 350 and 400 volts.

It would seem to me that going for a 48 volt LI solution would be considerably cheaper. Stand alone cells are available at up to 1000 amp-hours @ 2.6 to 3.8 volts volts. 13 cells @ 400 amps would do 48 volts nicely. A good battery management system is needful given the cost per amp-hour.

We have a 17 KW battery in our EV. Its actually 20 but mercedes derates out of the box. It occupys a good portion of the bottom of the vehicle. It would be easy to fit in a motorhome. The trick would be to get the electronics together to invert the output to 120 volts. It will be interesting to see how EV battery packs make it to secondary markets as they are harvested from car wreck write offs of all the EV's that are making it to market now. Even some of the early Prius units from 12 years ago that only had 2 to 3 KW's will have market value. The first leafs with 24KW packs had some overheating issues in hot climates so a number of them will be getting changed out under warranty although I suspect nissan will be keeping them and recycling them. Gotta figure though. Take an electric smart car like ours. Its expected to lose 20 percent of its capacity over 10 years. So lets say in 15 years when the car is sold off and the battery pack still has 12 to 14 KW. There is already an industry springing up around re-purposing EV batteries. A 14 KW battery would still be a heck of an addition to an RV. Read air conditioning for an entire night with no running of the genny etc. Should be an interesting decade.

I think Tesla's battery technology would be a good fit with RV's. First it's not very efficient to store and use energy at either 6 or 12 volts. Higher voltages are much better from an I squared R loss point of view.

Charging them would be very easy when at a campground with full hookups. It would also be easy when traveling if the generator was used. Alternators could be designed to output 110 vac or lower voltage alternators could be used with dc to Ac converters to charge them while traveling.

Using the energy from a high voltage battery bank is much more efficient then 12, 24 or 48 volt battery banks.

Bottom line is storing and using energy at higher voltages is good. High tension lines are high voltage for a reason.

The battery is around 400 volts. They are working with Solar Edge and Fronius to produce inverters for it but they aren't available yet. When they are you probably could put one in an RV but it would be rather expensive.

KD4UPL wrote:
The battery is around 400 volts. They are working with Solar Edge and Fronius to produce inverters for it but they aren't available yet. When they are you probably could put one in an RV but it would be rather expensive.

I guess. But an Onan Diesel is around 10,000 bucks. Would you even need one?

If I was going over 1500 watts of solar I would be looking at Powerwall for an RV vs a half dozen L-16.

moved from technology corner

13 cells @ 400 amps works out to 48 volts. That yields 19200 watts of which 80% or 15360 watts is usable.

Since we don't have to worry about the 100% recharge (and in fact that 100% recharge may be bad for LI) that gives a rather nice cushion.

Roadpilot wrote:
Using the energy from a high voltage battery bank is much more efficient then (sic) 12, 24 or 48 volt battery banks.

Dang.. I guess I'm not done yet!

Not real sure about your statement. You'd have to kick 400v down to 120v.

I suspect the 400 volt level was chosen as a match for a 240 volt inverter, since the peak of 240 volts RMS is ~340 volts. A 200 volt battery would be a better match for the 120 volt inverters used in RVs. Since the inverters we now use have to first step the voltage up to at least 170 (for PSW), a high voltage battery would eliminate the efficiency loss of the voltage step up.