Tesla Model S Battery for home Solar. BMS?

[Olle]

I am buying a couple of salvage Tesla battery modules to get 10 kWh back up for my home solar system. Would love PowerWall but won't get one for these reasons:

• Only available as a pair or more, which is really too much for me.
• Available with complete Tesla systems only, which I don't need.
• Not patient enough to wait through the backlog, trying to finish by end of this year.

I read WK057's BMS thread with great interest. It explained that the BMS don't activate when Modules are stand alone and so he had to make his own BMS boards. That was a couple of years ago.

Question for the forum: Does anyone know if BMS still doesn't activate alone with later year packs? If yes, is there a way around it, could you connect the cell groups to a third party of the shelf BMS? Or does anyone sell these replacement boards?


Not sure if this is the correct forum, mods feel free to move if you find a better one.

 

[David99]

Jason made his own BMS and posted a video on his YouTube just recently.

 

[Olle]

Jason made his own BMS and posted a video on his YouTube just recently.

very cool! That's exactly what I want, but for two modules not 36 . EVTV seems to have a nice unit: TeslaModuleController3.50.pdf

 

[sublimaze1]

Old thread - new twist (sorry for the hijack - mods, please move if you wish).

I am getting up on mileage (nearing 150k) and to the best of my calculations, have lost about 4.9% total chargeable capacity Truthfully, I do not see that as too bad at all.

Trade on my car might be decent, but there are things that need looked at (pano roof needs fixed, wheels have some chips, etc). Where am I going with this???

* If it up and gives me a major failure (e.g. motor dies, an accident that is a total, etc.) I am going to have it towed to my barn and begin the process of removing the pack.

* Not sure if I would pull the pack and use it as a whole, using the evtv Tesla pack controller or

* Remove each of the 16 ~5kw individual units and use them with a off-the-shelf controller and inverter, panels, etc.

As I see it, the batteries in this thing are quite robust and in their current state, with a healthy array of PV panels would power my house with no problem. In fact, if I only used half the modules (8) in a 4S2P fashion, I would be able to produce a 48V system, that would also be able to give 240/110 while allowing me to use the second (8) when the first become dead-cell replete.

Now, I still have a few years left in my 2012 85, so I have all the time in the world and have no sense of urgency (this is more of a tinker plan than anything else). So the outlying questions are:

1) Do I configure this as an off-grid system, and construct it, say, in a large unit (gun safe, container, pod, etc) with the intent of plopping it down on my "retirement lot in Central America"

or

2) Configure it as tie-in here locally, with the future intent of converting it to off-grid later.

As much as I don't want this to sound pretentious, it is not currently a financial issue as much as it is a lifestyle issue. I'd be running a freezer and a fridge, as well as a high SEER split AC system (probably three unit), so it is going to have to be robust (bigger controller, etc.)

Like I said above, the math shows 85kw pack, now at roughly 75 (I did calculations in 2012 which approximated the pack's useful capacity at 80.5kw, so I am throwing down a conservative figure for current day/date. Split that in half at about 37.5 and drop 20% for margin. That lets me guestimate 30kw of power to use per charged pack.

Nobody can really guess how many cycles I would have left, but having two packs gives me twice the longevity. (I'd say the chances of the battery dying before I die is about 50/50)

So the post is here, probably fraught with errors and bad predictions, as well as unknown factors which (I am sure) someone will be quick to exploit.

And please do so.

Either way, I am in possession of the most costly part of the solar power system (the batteries) and now I just need to think my way through the rest.

WJ

 

[miimura]

I would not reserve half the pack for future use. Instead I would put the whole pack into use and just cycle it in a smaller window. In the long run, I think you would be better off unless you're periodically monitoring the modules that are idle on the shelf. Also, 1/2 depth cycling will last more than twice as long.

Also, I would use an inverter system that can do grid tied and off-grid. The ones Jason chose (Outback Radian 8kW 120/240V) are very flexible and high quality. The only problem is that the AC voltage sags at the low end of the 12S battery voltage range. If you're not going to fully discharge the pack then it's not an issue. However, the EVTV approach using the whole intact pack has its merits too. However, the strategy is basically to power all of your loads from the inverter and only use the grid to charge the batteries when you don't have enough local generation. The Radians are more flexible and you can use smaller inverters and let the grid pick up demand peaks.

 

[sublimaze1]

I would not reserve half the pack for future use. Instead I would put the whole pack into use and just cycle it in a smaller window. In the long run, I think you would be better off unless you're periodically monitoring the modules that are idle on the shelf. Also, 1/2 depth cycling will last more than twice as long.

Also, I would use an inverter system that can do grid tied and off-grid. The ones Jason chose (Outback Radian 8kW 120/240V) are very flexible and high quality. The only problem is that the AC voltage sags at the low end of the 12S battery voltage range. If you're not going to fully discharge the pack then it's not an issue. However, the EVTV approach using the whole intact pack has its merits too. However, the strategy is basically to power all of your loads from the inverter and only use the grid to charge the batteries when you don't have enough local generation. The Radians are more flexible and you can use smaller inverters and let the grid pick up demand peaks.

Thank you. These are the good points I need to hear (and understand) as I move toward this. Now, more twist:

If I have a large enough solar panel array, and I have this large storage capacity, aside from fault or failure, what is the advantage to grid tie? This, also, assumes I have a large enough inverter (eg: sungoldpower 15,000W 48v) to handle large loads (AC, dryer, etc) while having a petrol generator (with electric start) as backup.

My tendencies now, are to lean off-grid, as part of the flexibility I wish to have is, say, to live in a location that has no utilities (obviously) but, as well, live where I want without relying on someone elses electric grid.

I like the idea of short cycling the packs and just using them all (except maybe minus two of them that I would re-work to power my golf cart)

Two more thoughts:

1) 48V runs cooler than 24V ... yes? no?

2) I have heard that, since the module is not a true 24V module (it is 22.8V) that there is less of a range of charge/discharge functionality. I would "guess" that by short cycling a humongous pack, that would be less of an issue, but I ask for opinions and thoughts.

WJ

 

[miimura]

If you are in a location (or want to move to one) that does not have any utility service, the considerations are very different. Generator backup will likely be necessary to make it through periods of low generation. Consider using a PHEV or hybrid car as a backup power source because the efficiency and emissions controls are better than anything stationary. It also avoids the duplicate ICE if you use the vehicle for routine transportation.

1) Higher voltage naturally uses less amperage for the same power, so has less resistive losses and requires smaller cabling.

2) Inverters normally have a low voltage cut-off to protect the battery system. Good ones have configurable limits. Some also have a low voltage limit, below which they cannot produce nominal AC power. If you have a large pack and can stay in the upper portion, you will be staying away from these low pack voltage issues.

 

[L-P-G]

I am buying a couple of salvage Tesla battery modules to get 10 kWh back up for my home solar system. Would love PowerWall but won't get one for these reasons:

• Only available as a pair or more, which is really too much for me.
• Available with complete Tesla systems only, which I don't need.
• Not patient enough to wait through the backlog, trying to finish by end of this year.

I read WK057's BMS thread with great interest. It explained that the BMS don't activate when Modules are stand alone and so he had to make his own BMS boards. That was a couple of years ago.

Question for the forum: Does anyone know if BMS still doesn't activate alone with later year packs? If yes, is there a way around it, could you connect the cell groups to a third party of the shelf BMS? Or does anyone sell these replacement boards?


Not sure if this is the correct forum, mods feel free to move if you find a better one.

The BMS boards still behave the same way on later packs, you need a controller to activate the balancing function.

I have that EVTV controller you linked for that function, here's my build thread.

Building my own pseudo(Powerwall)

It's expensive and after I had my system up and running I found out that inside the EVTV controller it just runs this open source code
collin80/TeslaBMS

Also you could go instead with the SimpBMS as it performs the same function (no contactor though) and it's only $399 I believe