Princeton university did a cost comparison between solar storage systems in 2013. Even then it was cheaper on a per cycle basis to use lithium.

Lithium battery prices have plummeted since.

One thing, don't compare horses to cars. Lead acid has serious draw backs for SESS. High self-discharge. Poor charge/discharge efficiency. The need to keep the pack fully charged. Low/short lifespan. The list goes on.

The benefits of lithium are not just lower cost. Its also a much easier and user friendly chemistry.

I have just gone 5 days without a complete recharge. Yesterday. A sunny day, I still didn't make full charge. I ran the dishwasher and a wide variety of tools. Using some 8kw of power, most of it from my solar panels. I did manage to recharge the batteries close to full.

You could never get away with that with Lead.

That's why I went on this journey. To find a better battery solution. It ain't perfect. But lithium makes lead obsolete.

When the automobile came out horses had been used for transportation for hundreds of years. Didn't make a difference.

Well. I got an email earlier this week from one of my fellow chevy volt experimenters. Not sure what happened but he had his cells go wildly out of whack.

After some months of no real voltage change this happened.

(Note: For all measurements, the module was almost fully charged, to within .5 V of 48 volts. The fellow, we'll call him A. Has 1 module that he uses in his tiny house for lights, radio, monitoring. I cannot say there were no external factors influencing the cell voltages [ie. putting a load on just one cell through a cell voltage monitor or ...])

As of 48 hours ago his cells measured:

1st 6 cells Diff=.05v
2nd 6 cells Diff=.3v

He uses a 6S monitor. It has proven reliable and accurate, verified with a voltmeter.

.3v is a lot. .05 is when I like to start balancing for sure.

Solution:

I rented him a "redwing" bms and after 24 hrs he reports

24 hours ago:

1st 6 cells Diff=.06v
2nd 6 cells Diff=.1v

Today he reported:

1st 6 cells Diff=.042v
2nd 6 cells Diff=.023v

Hmmm. I've gone 16 months without any real shift in cell balance/voltage variance. Can anyone else report on this?

Very glad to have the BMS to reestablish safe voltage balances. And let this serve notice to anyone using Volt modules. Monitor your cells!

Final update on the cell balance anomoly:

After a week of RedWing BMS use he reports
.009v difference.

Perfect result.

We will now be monitoring to watch if the cells go back out of balance.

Any update on your system? How low have you taken the pack down too?
Looking at doing 10 of these batteries for a peak load reducing system. 17.4kw array.
If anyone else has done this I would like to hear from you.
Thanks Neal

Being inspired by Creeky's experiences and others such as Mark Osborne and devildestiny555 on YouTube, I also took the plunge into the rabbit hole to use EV batteries for off grid use.

I expanded my 4kwh of 2 Chevy Volt modules that I used to test proof of concept, and added complete Volt and Nissan Leaf packs to an awesome 44kwh total storage solution. I am currently using 840w of Solyndra panels to top them off with a Victron 150/35 controller. I have a 8.1kw of panels in my garage to be setup for off grid use in this system (totally overkill for my application...but I got them on sale for .13/watt). I am using two PIP 5048 inverter/chargers in parallel for 8kw of off grid power. The inverters are cross wired to two 5000w transformers to give me split-phase 240/120.

I have been running this setup for 3 months now and could not be happier. I know technology changes with the wind, but if anyone is considering lead acid for a large storage solution...please think again. The advantages of lithium...and relatively inexpensive EV batteries repurposed...are too great!