Energy Storage System Using a Salvaged Leaf Battery


One could use a salvage battery pack from a Tesla or a Volt. The only problem is that those packs are liquid cooled and who wants to mess with that for an ESS (energy storage system).

However, Leaf modules are perfect for an ESS. Each Module has 4 cells with 2 hooked in series. Put 7 of these modules together and one has 48 Volts. They make a really sano ESS as shown in figure 1 and 2.

Editor’s Note: This article is credit to the Nissan Leaf Forum. The particular post is from a gentleman in Norway with the handle offpist. So hat tip to “offpist” for letting us share it.

Rack Of LEAF Batteries (Fig 1)

Rack Of LEAF Batteries (Fig 1)

Fig 2

Fig 2

The handy Norwegian used a server cabinet to mount the cells. The cabinet has a glass door and cooling fans on top as shown in figure 3.

Cooling Fans Help Regulate Temperature (Fig 3)

Cooling Fans Help Regulate Temperature (Fig 3)

Not all of us live in California that has great TOU rates for putting kwh’s into the grid during peak. In fact utilities are on a campaign to charge more for using the grid as a storage battery. Here in Arizona, my utility has just started charging for Net metering – although the Arizona utility commission scaled back their rate request from the original  $120/month they wanted to charge. In addition my utility now pays me only 2 cents per kwh for banked kwh’s I have not used at the end of the year.

All utilities in the US are not the same. One on the writers here (Mark H) has a looming end to his good net metering rates and is also seriously considering a big battery for his PV system as a result.

If one could pick up a good deal on a salvage Leaf pack then one could have a dynamite little ESS for less $/kwh than lead acid. The person in this case paid $2,000 for the whole pack so on a per kwh basis the energy storage is very reasonably priced (even less than lead acid).

Of course the devil is in the details. You also need lots of other stuff to create your AC coupled “Island” as show in figure 4.

SMA System (Fig 4)

SMA System (Fig 4)

Personally, I would like to make a smaller version of this ESS. I think around 6 kwh’s would be perfect for a portable battery/ inverter system used for emergency power. I am seriously considering this as a compliment to the DC tap I explained in a previous article “Getting your Solar Array to Work when the Grid is down”.

What do you readers think? Is this a cool thing to do with salvage Leaf batteries? I think it’s a slam dunk answer yes.

Cheers Leaf Heads   ☺

Categories: General


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23 Comments on "Energy Storage System Using a Salvaged Leaf Battery"

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Tesla batteries need liquid cooling to handle charging rates up to 120 kW and discharge rates up to 320 kW.

Liquid cooling is apparently not needed for Tesla batteries in home energy storage service, which involves much lower power rates.

Here’s an example of an 85 kWh battery from a wrecked Model S being set up for off-grid solar storage. With no liquid cooling, FLIR measurements showed that the re-purposed battery modules had almost no change in temperature even after an hour discharging at 18 kW.

I can’t help but wonder if it even needs to be this complicated. I know that many solar panels come with inverters to convert the DC voltage from the panels to AC voltage for your house, but I see two inverters here when it shouldn’t be hard to match the battery voltage to the solar panel output voltage. Wiring a single inverter in parallel to this system should ensure that only power not used by your house goes into your batteries.

On top of that, there should be hardware built into the Leaf that you can use for voltage regulation, battery balancing, charging, and all that fun stuff (which is usually a pain in the butt for people building their own batteries). There’s little doubt that the salvage yard where the batteries came from would be happy to let you pay for these items too. You might even be able to score the hardware that lets you monitor the state of charge, plus that touch-screen that ties it all together. 🙂

Or maybe I’m wrong and I don’t know what I’m talking about. It’s the internet after all. 🙂

We’ve got two cabinet mounted PbA battery backups in our datacenter to provide intermediate power to cover the time it takes for our ATS to kick over to generator power. They cost a hell of a lot more than $2000 each and have very low energy density and capacity (only about 20 minutes worth of power for four host cabinets and two VMAX cabinets).

Someone should source used LEAF packs and start producing a product for environmentally conscious corporations and home owners. I can say that wheeling a massive cabinet full of lead acid batteries up a ramp into a floating-floored datacenter is not fun.

Deep charge Lead acid batteries are not particularly cheap for energy storage solutions. That is because they have low cycle life even with 50 % DOD. 50 % DOD in practice doubles the cost per kWh of Lead acid batteries compared to their name plate capacity.

In additions there are concerns with low efficiency, low calendar life and often need for maintenance and need for ventilation due to hydrogen leaks.

Therefore in practice lead acid batteries are about twice as expensive as ferro-phosphorus lithium ion batteries. And for this ultra cheap salvaged do-it-yourself energy storage solution, we really cannot even compare the prices!

My big question is, where are you going to get a charge controller for the Li packs? Lead acid controllers abound, but I have never heard tell of a commercial Li pack controller that isn’t in a car.

I’m confident Tesla with it’s new giga factory will also creat a disruptive grid solution for the masses. As states like Arizona do all they can to discourage renewable energy solutions, tesla will offer a solution.