Can’t Wait For (Or Afford) A Tesla Powerwall? Why Not Build Your Own For $300?

DEC 30 2015 BY JAY COLE 49

Don't Have $3,000 Or More Than A Year To Burn? You Could Try To "Build Your Own" Powerwall

Don’t Have $3,000 Or More Than A Year To Burn? You Could Try To “Build Your Own” Powerwall

Not so long ago (well, 7 months ago) Tesla Energy announced the “Powerwall” energy storage solutions to quite a lot of fanfare.

The Tesla units comes in both a 7 kWh and 10 kWh version (details), priced from $3,000 to $3,500; which quite honestly for the sleek enclosure, and Tesla Enegy packaging cache, seems like a pretty decent deal to us.

That being said, the product was/is not exactly coming to market quickly (it is just now shortly arriving to a select few lucky customers).

Place a new order, and well, you are probably looking at ~2017 as a reasonable delivery window.

So if you are a little handy (and also little cheap), Jeru Garcia – of whom you might remember from “all-electic Samba” fame, walks us through a DIY ESS project that shows for those those willing to buy second hand batteries, there is a way to acquire the same basic system (complete with 18650 laptop cells) as the Tesla Powerwall for about $300 today.

Fair disclosure:  We are going to go ahead and assume that if your time is worthless and you aren’t interested in pesky certifications, then this is a raging good deal.

However, the total hours one would expect to spend on this project as a DIY assignment from front to back, would make it a pretty big money-loser in the long run, over just buying an “out of the box” solution from Tesla Energy, or any number of other residential battery back-up solution providers…but might still be a fun project though!

Hat tip to offib!

Categories: Battery Tech, Charging, General, Tesla

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49 Comments on "Can’t Wait For (Or Afford) A Tesla Powerwall? Why Not Build Your Own For $300?"

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The biggest problem I have with this is the lack of any protection circuitry, a BMS, temperature failsafes, under/over charge etc.

A Li-Ion without a BMS is a fire hazard.

And then you still don’t have any controller that proactively controls the amount of charge or discharge.

Still, a 48 Volt system (11S or 12S) would make the most sense for grid applications. Below 50 Volts DC is still considered “safe” as to not electrocute yourself, so there’s that.

And a 11S system should stay well within the limits that you could actually salvage UPS systems for charging and discharging. Some of the large UPS’s can be salvaged for a decent 3kW (modified) sine wave inverter. The only problem with that is controlling the amount of power you would want to feed into the grid.

Basically, it’s complicated, and that part is missing 🙂

Do you know where we could find out about these protections?

Another question I have is he doesn’t say anything about the way the cells are assembled into the bricks – is that frame something he made, or is it purchased?

You can buy many different versions of these:

I’ve used them in a few diy projects to make the final product look tidy. I liked them.

He has an older video that describes how he assembled the cells into a module (or brick). He mentioned it at the beginning.


I wouldn’t do this as not likely to live long using various age cells.
No BMS especially for mixed cells is not good.
And it only takes 1 over or under charging to kill them or worse, catch fire.
A far better idea is buy an EV pack or modules that are equal, high quality enough so you can use a lower cost BMS but unless you know batteries, electronics, I don’t suggest it now.
I’d go cellphone tower lead battery take outs used about $30/kwhr/ each/4 yrs or new$80/kwhr golf cart batteries about 6 yrs for now until lithium drops to under $200/kwhr retail, about 2-3 yrs.
I’m doing a Volt module pack for my EV’s but next will be for my home. But I have 45 yrs in batteries, electronics.

The lower cost of lead-acid doesn’t look so good after the better life cycles of lithium. Correct?

At $350/kwhr for lithium and no real reliable BMS, controllers for them available lead still wins as you get 3 sets of them and they are 100% recycled by law.
Fact is most are on their 15th, 20th recycle by now. So one could say they have unlimited life.
But as lithium gets under $200/kwhr retail because of it’s longer cycle life and as the electronics matures lithium is the choice. I expect that in 2 yrs.
Myself I’m doing used Volt battery pack modules that meet the $200/kwhr price but I’m a expert in it.
My guess in a yr or so electronic kits that convert whole sealed EV packs to this will make them available to the masses.
And 200 mile range EV’s will become bidirectional both taking and supplying power.
One could charge the EV at a fast charger then plug the house into it. It’s what I did when the power went out for 3 days.

You can buy a BMS for $200, no need to rant.

Still, a powerwall, or any other commercial version is insanely expensive.

Considering I’m allready paying up to € 8000 for my solar panels, I’m not prepared to dish out this much money to pay for Elon Musks third mansion

I once gave myself an electric shock trying to change a thermostat. I would like a Tesla Powerwall, and if I get one it will stay firmly within its enclosure without any interference from me.

I found this article about the economics of the powerwall in Australia. doesn’t apear to make sense at the moment.

I was just thinking how tragic it could be if one of these wall mounted units burst
Into flames? What kind of fire proofing is built into the Powerwall housing?

Well, I guess if you took a massive swing at the Tesla Powerwall with a sharpened Pick or a sharp and heavy Axe, you could penetrate the shell and maybe rupture some cells, then you could video it for sharing on YouTube!

I think that would be a reasonable approximation of the car incidents that had fires on the Model S battery, but I have not heard of any since the Titanium Front of the pack Shield was added.

With the Tesla built system, there is a good bet it uses their experience in battery management from the cars they biilt.

The personal built one is another matter! If I wass building such a system, it would use LiFePO4, since it is more stable and needs less cells since they come in larger capacity per cell. So, even if I then added thermal and energy management, the amount of sensors would be fewer. It would still cost nearly the same as the powerwall thoigh!

You can use Roxul products to insulate the interior.

No battery thermal management ? No BMS system? This is nothing compared to a real powerwall.

Tesla is a good deal ….Not to mention its all engineered Properly & all brand New!

Not Discredit the builder…He is awessome & I wish I were Capable of doing that ,Cuz I would.,if I could …Good work Dude!

How to make your own death trap?

This guy is awesome. Way to go!

To all the naysayers here, yeah, not everything is going to be as safe and sterile as a pre-packaged product. Now go put your bubble-wrap suit back on and get back under the table. 😛

You might be underestimating the scope of the risk here. Then again, every Darwin award winner has probably heard such negativity and worked hard to overcome such naysayers in order to win. You go get ’em, tiger!

Ehm, this thing hangs of a wall inside your house or garage. Your electrical car wil likely sit on the driveway outside.

It only takes one overcharge or undercharge to bring out the worst in Lithium Cells and burn your house down. A wooden case is not really the recommended enclosure for this 😉

This reminds me of the guy on the web promoting DIY solar systems a couple of years ago.
He would sell you an info. package that “they” didn’t want you to know about, that would get you off grid, running your appliances etc. for about $200.

Turned out to be instructions for cobbling together a solar panel from scrounged scrap solar cell bits.
Inverter? What’s that? Need more than one solar panel? Who knew?
Racking? Cabling? Fusing? Electrical codes? Meh!

Enough said.

Since he says it’s so low cost and easy maybe he will sell some for $500 each…..I think I’ll stay with my V2G from my EV.

Jim, You have V2G? What type?

Awsome project
I am not going to get all crazy mad at this guy because it’s not a real power wall or as good as a real power all of coarse it’s not
Let’s take a deep breath

I would personally like to see this done with the old Nissan leaf battery

There is a guy on TMC that did this with two old Tesla car batteries.

Leaf battery chemistry is not a (toxic and hard to extinguish) as big fire hazard as current Model S chemistry that requires active cooling to stay within temperature limits, which would be extra hassle. I think they are also cheaper per kWh in junkyards.

It is a bit crazy to assemble such blocks in your own garage and leave them plugged and unattended at night. Thermal runaway, fire and small explosion is real possibility in lithium batteries. I don’t think insurance company would pay for it, and local firemen would not be happy to extinguish lithium battery fire, more likely they would not know how and would not be ready for it.

DIY complex electrical projects are cool, but not without risk. That said, enjoy the music video:

Cool band all together!

What this really shows you is the huge mark up Tesla is getting on their power walls. In that they are most likely making the cells a lot cheaper then this guy bought them.

The biggest trouble though is I would buy the power wall from Tesla to avoid something breaking down and burning down my house.

Tesla is less than $200 per kWh. His used cells were about $50 per kWh. The battery gigafactory will drop the price to around $100 to $140 per kWh. So not a lot of profit until the gigafactory is at full capacity and full production.

Not a powerwall. 4.4 kWh versus 7 kWh for Tesla. That said, nice video showing his home project. I’d be curious to know how well it works over time.

I would love to own the 7 or 10 kilowatt power wall in that it would be a lot cleaner then owning a gas powered generator for those two to eight hour power outages.


Cleaner and Quieter,,,Yes and delightful relief for 2-8 hours, but then what?

An expensive, $3,000-$4,000 power wall just can’t beat a $500, sinewave inverter/generator converted to run on natural gas and or propane.
This too is an equally fun DIY project.

You need to maintain such generators or you may find that they don’t run even for 5 minutes when you will actually need them.

I can get solar power in an emergency a lot easier than natural gas or propane.

If the power outage happens at noon.

but can you take it with you in your car?

Easy peeeezy!

One of these BMS…

One of these Contactor 24VDC coil 400A…

7 of these Thermal Switches…

8 of these LiFeYPo4…

Orient all 8 LiFeYPo4 cells in a series stack.
Sandwich one thermal switch between each cell (with heat sink compund) and wire each thermal switch in series. You should have a thermal switch in between every cell.
Connect all 8 cells in series (1S1P) via buss bars.
Wire BMS board according to instructions.
Wire the contactors load connectors to the BMS (-) out terminal in series.
Wire the thermal switch bank so it is in series with the contactors control coil and the BMS (-) output and battery (+) output. This will shut off the contactor if any switch is triggered.
Connect your load (Puresine Inverter 8KW 120VAC?) to the (-) out of the contactor and the (+) out from the battery.

Somwhere in there you might want a manual Kill switch to take the entire pack offline.
You can also rig a PWM controlled set of cooling fans that is thermally adjusted with a thermister.

Thats the cliffs note version on how to build a theoretical 7.6KWh bigass brick that is thermally heat protected and cell managed/protected for HVC/LVC & Max C rate.

Thanks capt jack. doesn’t look like time needs to be “worthless”, to do this. At $3,000 – $300 cost difference, those with a few brain cells can probably succeed. The rest? Yup, bubble suit.

8 of these LiFeYPo4 Price $279.50 each.

This guy repeatedly confuses kW (power) with kWh (energy). I have difficulty taking anyone seriously in this business when they can’t get the absolute basics right. And don’t cry “just a silly mistake” to me. At this level of DIY, you should live and breathe kW vs kWh.

I have the same problem.
Confusing different basic things isn’t good for clarity or trust.
Get down to basics, don’t do that unless you’re totally aware of the risk, which are greater than the video might suggest.

I would NOT advise buying 18650 batteries on ebay. If you buy the straight cells, most of them are Chinese junk usually with names like ultrafire, etc. They often have half or less of the capacity of a good Panasonic battery but they advertise them as having 4x the capacity.

If you do what this guy says and buy used laptop batteries then you are going to have a bunch of cells that are at end of life or vastly degraded capacity. balancing them would be a nightmare.

A li-ion battery pack made of used cells and doesn’t have a BMS (Battery Management System)?

Wow, just wow. This should come with a very clear “DANGER! SEVERE FIRE HAZARD!” warning.

Properly made, properly balanced li-ion battery packs use cells carefully chosen to have the exact same voltage, and use a BMS to ensure that all cells are charged and discharged to the exact same voltage.

Using second-hand cells from different sources, it’s going to be virtually impossible to build a balanced pack, and without a BMS, there is a major risk of either completely exhausting the pack, prematurely aging it, or on the other hand either overcharging it or charging too fast… either of which would cause a fire.

Anybody who builds a jury-rigged li-ion battery pack according to these instructions would be well advised to put the pack outside, well away from the house, on a concrete pad, so that when (probably not if) the pack catches fire, it won’t burn down their house.

some other guy doing same thing but with the fail safes on youtube – looks like he is only a few months into it with a bit to go..

Why not make a technical drawing and have a techy look at it. Now I read some comments, those comments could be useful for improvements.

All this talk of fire. Show me an example(s) of someone who has built one of these, and has caught fire? BMS and thermal management is simple to add.