I have unlimited Tesla modules...could use help designing a RV system

[darkostoj]

Hey guys, first post here.

I own a salvage yard and we pretty much have unlimited tesla modules, we've taken apart a lot of these cars.

I know there may be better options out there from the research I've done, but I have these here...so it's hard to argue against using them.

The vehicle:
2017 F350 Dually with Cirrus 820 Truck camper.

I am going to build a custom flatbed that will house the batteries & inverter. I like the idea of having a mobile heavy duty truck/power station. I would like 3 outlet plugs (50amp RV plug, 30amp RV plug, 20 amp standard house plug). I'll just plug the camper shore power into the truck..I like the idea of not doing any custom work/fabrication to the camper itself.

I wanted to use the truck engine to recharge the modules with either a second engine mounted 24v alternator, 48v alternator, 240v generator.

So I guess my main questions are

1. Should I run the system as a 24v or 48v?
2. I hear the Tesla modules have their own issues, what are some things to watch out for to make sure the setup is done correctly?
3. Can I hook the alternator directly to the batteries for charging?
4. Do I need a special inverter to handle the specific tesla battery configuration?
5. How can I figure out how long it would take to charge the battery bank off the engine?
6. Any recommendations on how many kwh would be a good amount? My thought is the more the better so 8 would fit nicely for ~40kwh. Goal is to be able to fully run the a/c and other components on the camper for a full night minimum then have the truck be able to charge it during the day.
6. What other components would I need for a proper install?

Thanks!

 

[schmism]

50a@220v = 11000w IMHO this is well into the 48v territory. Whole house off grid inverters is what your looking at. Ones that support 120/220v generator input (with auto start) will push the pricetag of one of these up in the $5-8K range.

alternator based charging, if you went with a semi sized alternator 200a @24v = 4800w. 40kwh/4800 = ~8hrs charge time.

You'll need something that manages the chargeing of the tesla bats. your input power to the pack will need to be managed by this device. (so no the alternator can not be hooked directly to the bats)

 

[HRTKD]

Which engine do you have? The 6.7L or 6.2L? The 6.7L should have dual alternators and more amp output, possibly eliminating the need for a special alternator. You would not want to wire the alternator output directly into the batteries. Instead, you want a DC-DC charger that understands how to charge your specific battery chemistry.

 

[softdown]

Tesla uses great cells. Absolutely top tier performance wise. Each cell is fused so they are still pretty darned safe as lithium batteries go.

You still need to know what you are doing. Unless you have a lot of spare time and morbid curiosity it may behoove you to trade cells for usable battery packs - whatever your use may be.

I've been hard at it for a month - still feel like I need to learn a bit more before making my own packs with my spot welder. I enjoyed reading DIY Lithium Batteries by Micah Toll. Easy to understand - even fun to read. About $18 at you know where.

With your location these is a good chance a local poster could benefit both. Such 18650's are still the most common vehicle of the DIY type. Also - HB Powerwall and Ebikeschool on youtube.

PS - I'm in the market for such cells.

 

[tictag]

@darkostoj, have you considered selling them? I'm sure there would be people on here that may be interested. I'd buy one if I had more than two hayp'nies to rub together.

 

[Tball]

I’m with @tictag!

 

[softdown]

He never even told us where he is. I've seen so many one wonders stir things up and disappear forever it boggles the mind. I could also see a forum user creating the account to get folks excited about "unlimited Tesla cells" while snickering away. Of course anything is still possible.

 

[nosys70]

tesla pack need a lot of care to be operated properly.
if you can use several of them to spread load , then you can care less, because you won't put them in extreme situation.
but when they are in the car, the car is build around and bring a lot of safety (casing, cooling, management) that could disappear in a different setup.

 

[John Frum]

For real power https://www.youtube.com/channel/UCQSZW8-S__mjqXwzf9lCivw/videos

 

[mkaye]

look at this
https://view-naviontech.groups.io/g/discussion/topic/76479678

 

[Alonzo]

Why would there be "unlimited" modules available at a salvage yard. Is the "safest" car on the road getting into that many accidents, and all in that one area?

 

[schmism]

Why would there be "unlimited" modules available at a salvage yard. Is the "safest" car on the road getting into that many accidents, and all in that one area?

"safest" typically means the the occupants in these cars, received fewer injuries when involved in accidents on avg than people driving other cars.

That says nothing about how frequently Tesla are involved in accidents. (at fault or not)

The other reason they wind up at the salvage yard, they have a high likely hood to be "totaled" by insurance companies is they are more expensive to repair. Many of the parts only come from Tesla, and are typically only repaired at Tesla service centers. This is seen in the very expensive insurance rates for them to the point that Tesla started offering car insurance (initially just for Teslas) through just last year.

 

[Alonzo]

"safest" typically means the the occupants in these cars, received fewer injuries when involved in accidents on avg than people driving other cars.

That says nothing about how frequently Tesla are involved in accidents. (at fault or not)

The other reason they wind up at the salvage yard, they have a high likely hood to be "totaled" by insurance companies is they are more expensive to repair. Many of the parts only come from Tesla, and are typically only repaired at Tesla service centers. This is seen in the very expensive insurance rates for them to the point that Tesla started offering car insurance (initially just for Teslas) through just last year.

I was being sarcastic with the safest comment. I've read so many Tesla owners brag about how it's almost impossible to have a wreck with the autopilot system, etc. Seriously though, I didn't think there were enough Teslas on the road to provide an unlimited supply at a single salvage yard. Maybe he's getting them from other yards around the country.

 

[darkostoj]

Which engine do you have? The 6.7L or 6.2L? The 6.7L should have dual alternators and more amp output, possibly eliminating the need for a special alternator. You would not want to wire the alternator output directly into the batteries. Instead, you want a DC-DC charger that understands how to charge your specific battery chemistry.

It's the 6.7L It does have dual alternators. So the Tesla batteries need a specific charge profile that can be attained through a DC-DC charger? Is there one specifically for a Tesla out there?

@darkostoj, have you considered selling them? I'm sure there would be people on here that may be interested. I'd buy one if I had more than two hayp'nies to rub together.

Yes, we sell them all the time. I didn't want to post anything since I'm not sure how the rules work on the board here.

He never even told us where he is. I've seen so many one wonders stir things up and disappear forever it boggles the mind. I could also see a forum user creating the account to get folks excited about "unlimited Tesla cells" while snickering away. Of course anything is still possible.

In Detroit.

Why would there be "unlimited" modules available at a salvage yard. Is the "safest" car on the road getting into that many accidents, and all in that one area?

I used the "Unlimited" title to get more clicks. We buy vehicles all over the country and ship them into our shop at Detroit.

For real power https://www.youtube.com/channel/UCQSZW8-S__mjqXwzf9lCivw/videos

I am looking into this, but its very expensive. There are a few different companies out there that do PTO generators.

 

[HRTKD]

It's the 6.7L It does have dual alternators. So the Tesla batteries need a specific charge profile that can be attained through a DC-DC charger? Is there one specifically for a Tesla out there?

I'm not familiar enough with Tesla battery packs to recommend a DC-DC charger. I know just enough to know that if the truck is going to be the main charging method, the charge from the 7-pin connection isn't going to cut it for two reasons.
1) The 7-pin connection will never give you more than 30 amps on a modern Super Duty. Real world numbers come in closer to 20 amps.
2) The charge profile from the alternator is OK for a lead acid battery, but not a Lithium type battery.

 

[HaldorEE]

Why would there be "unlimited" modules available at a salvage yard. Is the "safest" car on the road getting into that many accidents, and all in that one area?

"Fire Sale"?

 

[Dzl]

Yes, we sell them all the time. I didn't want to post anything since I'm not sure how the rules work on the board here.

For reference promotions, advertisement, selling stuff, is fine, so long as it is in the proper section and not spammed (if you are a business I believe that would be the "corporate corner")

 

[tictag]

1. Should I run the system as a 24v or 48v?

You mentioned, "I would like 3 outlet plugs (50amp RV plug, 30amp RV plug, 20 amp standard house plug).". In order to supply all outputs simultaneous at their rated loads you would need an inverter(s) capable of supplying 100A + 25% wiggle-room at 110V or 13,750W. That is a very, very big power demand, but let's roll with it...

Cables above 250A start getting very big, and very expensive, very quickly. 250A at 48V (nominal) only gets you to 12,000W so, unless you want to go up to 96V (niche) then you're looking at at least two inverters sharing the load. 24V (nominal) is, imho, simply not an option for this application.

2. I hear the Tesla modules have their own issues, what are some things to watch out for to make sure the setup is done correctly?

According to Wikipedia, the Model S battery contains 16 modules, each made up from 6S74P NCA cells. NCA cells have a nominal voltage of 3.6V so each module would be 21.6V (nominal). NCA chemistry requires a charging voltage of 4.20V so each module should be charged to 25.2V at no more than 0.7C according to here. The Tesla Model S battery is 85kWh, so each module is 5,313Wh, meaning maximum charge current is 172A.

With so many individual cells, a per-cell BMS is never going to practically work so I would recommend a typical 6S Lithium Ion (not LiFePO4!!) BMS capable of supporting the maximum discharge current for the chemistry of 246A (i.e. 1C) balancing each string as if it were one cell. If you're buying a cheap BMS, I would recommend de-rating by it at least 30%, so 320A.

3. Can I hook the alternator directly to the batteries for charging?

No. You'll need to go via a DC-DC charger such as the Victron, Stirling Power, RedArc etc. Be sure to avoid over-loading your alternator - remember the alternator will also be charging your starter battery immediately after starting, and that's when you'll have low revs and, therefore, minimum cooling. Watch this for further info. Whatever charger you choose, ensure you can adjust the charging parameters as above.

4. Do I need a special inverter to handle the specific tesla battery configuration?

No, just make sure that it can provide it's rated output across the full operating range of the module(s) i.e. 18V - 25.2V (i.e. 3.0V per string to 4.2V per string). Well, I guess, yes, in that case! What I mean is, the inverter does not care it's a Tesla battery.

5. How can I figure out how long it would take to charge the battery bank off the engine?

Let's say your alternator can safely supply 50A to the DC-DC charger without cooking itself, assuming your alternator runs at 12V (nominal), that's 600W so ignoring losses it would take 8.9 hours to re-charge a 5,313Wh module from empty to full (5,313Wh / 600W = 8.9h). But this is not a useful metric because you will only need to charge whatever you consume. Consume 1,000Wh and it'll take 1.7h etc.

6. Any recommendations on how many kwh would be a good amount? My thought is the more the better so 8 would fit nicely for ~40kwh. Goal is to be able to fully run the a/c and other components on the camper for a full night minimum then have the truck be able to charge it during the day.

Not sure I understand this. Is this consumption in addition to whatever is being supplied via the three outlets discussed above?

Either way, an A/C typically requires around 1,000W in operation, so a fully charged 5,313Wh module would power this for around 5.3 hours (ignoring losses).

6. What other components would I need for a proper install?

That's too big a question for now, and I'm very tired!

Good luck with your project.

 

[Zil]

I didn't think Tesla made that many vehicles in total for there to be many available in any one wrecking yard.

 

[electric]

Each cell is fused so they are still pretty darned safe as lithium batteries go.

This is a very dangerous statement. Fuse only protects from short circuit, not from overcharge or overdischarge. These cells can quickly turn into firecrackers if you mismanage or mishandle them and fuse won't do a thing about it.
Additional risk comes from re-configuring existing modules for different voltages/capacities, i.e. trying to separate cells and weld cells in different layouts. Don't do it unless you are prepared to extinguish a serious fire with lots of water.