Chevy Volt battery pack for off grid solar?

[creeky]

Originally Posted by jjackstone

Ah, maybe you're only measuring what goes back into the batteries each day since you are off grid. JJ

You got it JJ. I'm usually recharged before noon. Most of my power use is during the sunny times.

In fact. My solar production will drop now that I don't need the a/c. During the transition to the new battery I was able to get by with just 1 kw.

Sadly Oct/Nov/Dec are very cloudy in my area. And I need the extra kw then.

[creeky]

A note on lithium:

I just microwaved some stuff for a snack. 5 minutes of microwave time.

Battery pack voltage pre-microwave. 47.95. Post microwave. 47.79.

Amount of voltage sag. None observed.

I'm only posting this to bug guys with lead acid battery packs. smile.

[randen]

Creeky

It very good that your having some good results with your pack. Thanks for sending over the bits. I'm still accommodating the 2 Chev volt packs for the truck.

The aluminum box will contain about 5 kws and will be placed where the spare tire went between the frame rails.

The OEM battery box will be placed between the frame rails ahead of the rear axle.

The focus right now is plumbing for liquid cooling/heating the packs. Followed by the installation of the main contactors.

Thanks again for sending the pcs.

Randen

[creeky]

Looks awesome Randen. That is going to be some incredible truck. You'll have to capture some smoke off of the tires on the first drive and send it to me.

Happy to see some of the excess parts from my pack finding a new life. I'm thinking I will turn the old shell into bird or bat houses. But that's a project somewhere in the future.

Happy to report I had my first heavy use (tv, dishwasher, etc) but low sun day. Made almost 8 kw on the sunny day following (not home at the time) easily refilling the batteries.

[CFECO]

Great story! I am building an Electric off road buggy using Motorcycle suspensions, golf cart drivetrain ( For Now) and a Chevy volt battery ( 48v) for power. I have one 48v section which I am also trying to use for my camp trailer "House Battery," using a 48v to 12v voltage reducer. Anyway if you have any 48v battery sections left over I would be interested in them...

[creeky]

CFECO I have two 48s left over. Not sure if I'm hanging on to them for other projects or selling them. But AZ is a llloooonnnnggggg way away from me. Not economical to ship.

Look forward to seeing your build tho. I'm going to have a poke at a small "solar barge." In part so I can dock at my girlfriends and get around the dock regulations. Smile.

I have started doing a bit of research on building a trike. I look forward to seeing how your build goes together.

[creeky]

Btw. It's a dark and cloudy day here. At mid afternoon the sun started breaking through the cloud. I saw 1068w from an 8 year old 1kw panel set. Angle set to 30 degrees. So not optimal for this time of year at my latitude.

Kind of interesting. As I've noted elsewhere. The "rated" max for panels this age should be 930w.

Maybe lens flare off a cloud edge amping up the solar incidence?

Also. I'm fully charged at mid day. Seems like all it took was a bit of breaking cloud. Lithium rules!

[creeky]

Quick update: 4 months.

Perfect, even astounding performance. I have had up to 5 days in a row at less than fully charged. While I reduced use to 2-2.5 kw/day the pack only went as low as 43.5v. With 48v "fully charged." My low cutoff is 40.5. One sunny day and I was fully recharged.

This 5 day gap is primarily due to the efficiency with which the batteries recharge.

By ex. After 3 days of not being fully charged. Down to 44.5 at the lowest. I ran the dishwasher on a partially sunny day. The system made just over 6kw off my 2kw panels. And finished fully charging under better sun the next day.

This kind of use is just not done with lead. Absolutely proves lead is dead.

Morningstar controllers continue to work well. I am seeing a few anomalies. Including odd resets (with no reset actually occurring), loss of internet connection (stats still available via MSView), temp reading popping up to 25 and then returning to actual. Yet the wires are attached securely. Meh. Its still charging perfectly, charge values have not changed.

With the onset of winter and short days comes freezing temps. The batteries (off grid application) are stored in an out building with no heat.

A hacked together box of polyiso insulation and R values around R30 along with the inverter being inside the box has been enough to keep battery temperatures around the 10C mark. Yesterday I sealed the box better with some spray foam. I did have considerable gaps at one corner. Just in time for two weeks of cold sub 0 weather. Should be interesting to watch.

Sadly, I'm traveling this winter. I will be unable to monitor the performance of the insulation and inverter heater setup in keeping the batteries above 5C during the depths of winter as I will be shutting the system down.

Still. How nice is that. Just discharge to 3.85/cell then shut down and leave it. Take that lead!!!

[stevehull]

Creeky - good to hear from you about the update. Chuckled to read "lead is dead" . . . . (and I agree).

Regarding keeping the batteries from freezing. Can you install them such that you get some ground heat? I realize that your deep ground temp in your Canadian "tundra" is probably 40 F (?).

Thought experiment . . . Am thinking of a box on the ground with 1/2 inch foam insulation below it. Above the box and on the sides are 6 inches of foam insulation (much more insulation). The net gradient of heat will be up from the ground, into the box, with little heat escaping.

We all know that the Li-ion batteries suffer terribly from cold - and the colder it gets, the worse it gets. Is it possible to build such a physical box that keeps cells above 32 F (0 C)?

That all said, how much heat (i**R) is "generated" during charging and discharging. Can wrapping all up in R30 trap that heat?

Great project!

Steve

[creeky]

Steve. Great idea about the basement storage. Sadly, my property is river bottom. In the spring I get significant ground water. The soil is very soft. If you drive into my back field the only thing keeping you up is the grass mat. It's a pretty cool feeling.

I'll digress. Last spring my insurance agent came into the back field and parked in front of a straw bale thinking that it was a sign of a parking area. Sadly it was a sign that the area in front of it was grass free. She sunk up to her axles. I wasn't home. She had to walk the mile to the neighbors to get a tractor to get her out. ha ha ha. I laugh.

Thus, I am unable to build a basement or cooler room. That would be ideal. And I recommend that to anyone doing solar. Put your batteries in the basement!

So far my polyiso box is working. I'm running the experiment for a wee bit longer. So we'll see what we see.

Notes:

1) I have seen no heating from battery use (unlike lead where I could keep the batteries warm just by running a heavy load). Previous to the box building if I ran the dishwasher, batteries that were 10C to start were 10C to finish. This surprised me.

Now that I've boxed the batteries I saw 10C to start and 12C to finish. I think this is due to the inverter being in the box. Even at 94% efficient it is generating considerable heat. Over a 100 watts of heat from one cycle of the dishwasher. Another 100 watts should be lost to heat daily with regular use. A good insulated box and I might be worrying mostly about keeping it cool. (I jest of course).

2) according to the literature lithium batteries see very little degradation of useful power with temp change. Very much unlike lead. However at below 5C you will get increased degradation of the anode material. Effectively shortening the lifespan of the battery. Hence the need to keep your batteries warm.

Dendrites be damned. Looking forward to seeing that problem fixed.