Chevy Volt battery pack for off grid solar?
 

Yikes. I have the opportunity to buy a 2014 Chevy Volt battery pack for 1500 CAN.

Background:
As my FLA is dying (5 years of crappy performance was enough for me anyway) I thought. Gee. Why not go from 2kw of usable storage to 12!

So I looked at lifepo4. Easy to install into my current system. But $$$.

Now I have this chance to buy a Volt battery. The $/w is pretty good. You know. <$100/kw.

But I'm a writer. Not an engineer. My solar build (cough cough) has been a 5 year lesson in electronics. And I've learned a lot.

However. To retrofit a volt battery pack for off grid use ... I mean it sounds like fun. My FLA will easily last until Oct. Before the cloudy weather gets here. So I do have 4 months for the build. Still ...

Idea 1:
Take the pack apart and repurpose the cells at 48v.
Involves buying a 48v inverter. REC? bms.
Within my limited knowledge/skill set.

Idea 2:
Find a way to charge from AC. Keeping the charger and plug from the Volt. Involves finding an inverter for my solar panels (sunny boy?). Would work with my genny if bad stuff happens. Not sure at all about how the charger/wiring would work without all the brake regen etc. Could well be above my electronics ability (cough, seem to be catching a cold).

Ideas from 3:
Well. That's up to you'ze all. :o

At that price, I would go for it. The majority of your time will be spent disassembling buss connectors and testing cell banks. All this is DC - and safe.

There are a lot of people that are here on this site that can help you no matter what the direction you go.

Sounds like a FUN project and I think you are getting over your cold . . . .

No matter what, you are going to need a large multi kW inverter to convert that stored DC to 240 V, 60 Hz AC. But these are getting downright cheap.

I sure like the flexibility of using the already existing 240 V Chevy charging system already on board. In that case, little disassembly is required.

What do you know about this battery pack - was the Volt accident totaled and someone is parting it out?

Steve

That's a lot of juice.
48v option would work best I think, but how do you balance cells?

Well. I'm still in the fingers crossed stage. To be uncrossed the moment the pack is on the floor of my shop, top is off and I'm testing cells.

What I see right now looks good.

The plan:

Pull the 48v packs out and sell the two 24s. And maybe 2 of the 48s.

Say I keep 6 48s. That's 45ah at 48v x 6 modules for, um, should give me 13kw. With say a 50% dod and 50% for knees.

Allow me to start to rub my greedy little hands together. Bigger fridge. Internet on 24/7. TV binges well into the night. Midnight dishwasher, why not?

Now:

I will have to replace my inverter. Anyone for a TBS 12-1200? Beautiful inverter.

And ideas for a 48v inverter. I see some nice ones from Helios in China. Or that Victron 48-1600 looks like it would suit nicely.

Also debating the bms issue. A simple balancer with the big knees of dod and charge should work.

Looking at ideas to keep the costs down.

Here is a link that has been posted a couple times that might help with your build.

Use of Nissan Leaf battery in Solar installation. - My Nissan Leaf Forum

JJ

Thanks JJ. I have seen his post. Very interesting. I'm waiting until the battery pack is in my hands and then I will decide what kind of bms to use. The REC bms he uses is a top contender.

I am reading more and more about how GM handles the bms issue. They seem to count on the cells staying balanced after what I assume is a prebalance.

The voltages look to be a bit tricky too. Each pack uses 12 cells. So it appears so far that 49v is full charge. 38v at low. Makes it awkward to use with most inverters. So I will need a programmable inverter. Of course my morningstar solar controllers will have no problem with it.

Anyway. It's all moot until the battery is on the floor.

Here is some food for thought.
Schultz Engineering - Delta-11 Electric Motorcycle - Chapter 12 Adding Chevy Volt Batteries

Cool project post lots of pictures.

Thx Pinballlooking. I have seen his post and contacted him. He was nice enough to write a brief message back. Great build.

I pick up the pack Friday. I'm trying to control my excitement and failing. It's starting to feel a lot like <holiday in winter> and I'm five years old.

Currently (nope, never gets old) I'm looking at the Victron inverter series. The 48v inverter has the advantage of being programmable. And is capable of inverting down to 37v (3.1v/cell). Which given that I will charge to a max. 49v (4.1/cell). Gives me comfortable knees for my charge discharge cycle.

Porsche 914 Electric
is an interesting chevy volt tear down and bms add

2015 Montana 3611RL The Adventure Begins: Chevy Volt Lithium Battery Packs For My Montana RV
this guy bought volt batteries configured as 12v and now is making/made his own arduino based bms. I haven't had a chance to read it yet.

Heart racing. Will Friday ever come? Will my girlfriend talk to me if I don't go help with the garden?

So. It's Friday. Drum roll.

The wrecking yard in far far far north Quebec was nice enough to deliver the pack 1/2 way to my house. They drove for 3.5 hours south. I drove 3.25 hours north. We met. Slid a pallet between two truck beds.

I drove home thinking. Please be 3. I gambled. No way to test it. Needless to say. First thing I get home. Tractor comes out. Fork lift bars go on. Pack gets carried to the tractor shed where it will reside while I work on it. I get the lid off. Out comes the voltage meter.

Front pack. 115.3v or 3.84 /cell. Middle pack. 92.1 or 3.84 / cell. Back pack. 161.4 or 3.84 / cell.

Huge sigh of relief. Minor dancing in the field.

So I now have a 2014 pack basically fully charged. All I need to do now is take it apart. Build/find a bms solution. Reconfigure my Morningstar solar controllers. Buy a Victron inverter. And a few other dozen things.

But that's a job for tomorrow.

Am now taking suggestions for BMS. I wouldn't mind trying an arduino atmini something. Anyone with ideas?

http://creektreat.ca/wp-content/uplo...m-1024x576.jpg

BMS musings:

After some initial research: Building my own BMS is probably a bit out of my time/capability ranges. Buying one does get pricey. So right now I'm leaning towards the basic cell monitoring with the option to turn on cell balancing. From what I've read, cell balancers gone bad kill more battery packs then packs left alone.

Some relatively inexpensive made in china offerings. Can anyone check my math/understanding. My brain is a bit fuddled lately. Lot going on besides the new battery fun.

Problem: What amp BMS do I need?

Given: 48v.

Max. of 2400 watts draw. Surge power for 10 secs or less. And usually a max of 1500-2000 sustained for more than a minute or two (vacuuming and the fridge starts and runs).

6 battery packs providing power.

So if I take: 48v with 2500w I have 50 amps draw.
Then I divide by 6 packs. And I end up with 8 amps draw.

If I consider expanding my system to two inverters. That might go 20 amps tops?

This is important as the BMS get more expensive per amperage.

Testing:

I haven't had the time to check the cell levels yet. Right now they look good as all the packs basically add up to 3.84/cell. Which might indicate that the cells are fairly well balanced.

Fun photos from the unload:

Here's the pack in the back. Of my truck.

http://creektreat.ca/wp-content/uplo...ehaslanded.jpg
The Eagle has landed

It was a bit tricky. The biggest battery was at the wrong end. I could slide the pallet in the bed but the tractor couldn't lift it. Finally, after three or four adjustments to the forks and then running the revs to the line. I got it up an inch. and very. very. very. slowly and carefully backed up. Heading for the shed.

http://creektreat.ca/wp-content/uplo...the-batt02.jpg
Lithium pack is out

The tractor really can't support the weight and the pack begins to drop. It's a race to see if I can get to the tractor-run-in before it droops to the ground.

http://creektreat.ca/wp-content/uplo...3a-768x442.jpg

Huzzah. Al pays for himself again. Always good to have a buddy who can lift 500 lbs with his two iron arms.

After a good battle with the cover. The important part. Testing voltages.

http://creektreat.ca/wp-content/uplo...testing123.jpg
Testing 1-2-3

As always. There's a bit more info at the blog.

***

Any body else with ideas re: BMS. Yes, No? Huh?

Check out this project it might interest you. He is using a Tesla battery pack.

https://teslamotorsclub.com/tmc/thre...e-heart.34531/

Thx for that. Totally insane amounts of power. I'll be amazingly happy with 8 kw usable. Forget 80.

I'm on that cusp, ya? SMA and others are just starting to get high voltage DC storage/use together. What a great inverter they have. But then the added hassle of charging. Looked at it. But it's pretty much "next year."

So it'll be 48v for me. And my next install. In 5 years. When I get restless. I'll look for a 500v system.

If a cell leveling system fails .. yes it can cause the very problem it is supposed to prevent .. Just a question of Mean Time Before Failure (MTBF) .. OEMs like Tesla, GM , etc... all have a high enough MTBF that their electronics fail very very rarely ... soo they all use cell level balancing & Monitoring.

Basic level would be a Battery Monitoring System that sends a 'top' signal at the top of charge .. to stop from over charging .. a 'bottom' signal on discharge , to prevent over discharge ... show you the current usage volt/amp/watt .. Do cumulative AH/Wh counting ... The Ah part makes a fairly easy fuel gauge as the Ah cycle efficiency is pretty high (around ~99%).

Off the shelf example that looks at whole pack level (not cell level) for all of the above: EV-Display
w w w .electriccarpartscompany.com/EV-Display-Battery-Pack-Monitor-br-Voltmeter-Ammeter-Fuel-Gauge-br-2-inch-round-or-square-br-12V-24V-48V-72V-96V-120V-144V-br-5Ah-10Ah-20Ah-30Ah-40Ah-50Ah-60Ah-br-70Ah-100Ah-180Ah-200Ah-300Ah-br-3-external-outputs-USB-Serial-Port_p_134.html

(remove spaces between the w w w)

Cell level drift / imbalancing should be very slow .. a ~10 mA or so correction rate from a 24/7 device is plenty .. only need higher Amp for the main whole pack battery amps monitoring .. If you have Lithium cells going out of balance faster than that .. you have lithium cells that should be replaced.

One alternative .. that doesn't open the cell level failure risk .. is to only monitor the pack to see if there is an imbalance .. than you can manually fix/service that imbalance yourself ... that can be done very inexpensively and easily by comparing the voltages of the two half packs .. a perfectly balance pack .. the two halves should be the same voltage all the time , even under load .. if there is only a small resistance different between the two halves you can set up your comparor to have a 'fudge' factor .. like 1v or something .. only informing you if the difference between halves is greater than that .. Example of a simple circuit for that attached.

Ian, I am trying to keep it simple. And I see plenty of evidence online that good quality lithium cells stay in balance. But, but, but. So a part of me wants to do the simple and easy thing. Perhaps I could do a similar board dividing the pack into the 6 parallel units?

Here are three BMS solution providers I have contacted.

Supower. No documentation. Few reviews that I can find. 60 bucks a board at 60 amps delivered to my home. So 360 for the base BMS.

bestekpower has some BMS with communications boards. very poor documentation which ... but good reviews amongst the EV community.

great reviews. lots of users. good documentation
The REC BMS.
They have got back to me suggesting that I run the new Q BMS. I'll have more detail on that a bit later.

Simple to make .. or .. Simple to use ?
At some point one of those must be chosen as more important than the other.

I assumed simple to make .. That's why I suggested the two most simple options .. Basic EV-Display type whole pack and Batt-Bridge.

Batt-Bridge type half pack comparator .. as simple and inexpensive as it gets for informing you if the cells drift out of balance .. If it happens you can manually go in to service the pack .. if it happens often .. than you can always later add the cell level BMS.

EV-Display type simple basic meter to signal whole battery Top &/or Bottom .. and do Battery Ah/Wh counting.

Although it add complexity and cost .. if the MTBF rate is high enough for the cell level BMS .. Like those seen in OEM BEVs like Tesla's and such ... than it makes a lithium battery pack pretty much a 'black box' that just works , as that cell level BMS does any maintenance for you .. more complex system .. but less complex yearly maintenance/service .. ie .. less simple to make .. more simple to use.

- - - - - - - -

For parallel .. you have two main paths:

1. Parallel Cells:
   • Pros:
     1. 1 BMS cell circuit can monitor and service all the cells in parallel.
     2. Strong individual Cells can help carry weaker cells they are paralleled to.
   • Cons:
     1. If 1 of the cells in parallel isn't just weak .. but actually goes dead .. it will take all the other cells in parallel with it.
2. Parallel Subpacks:
   • Pros:
     1. If one cell isn't just weak but goes dead .. the BMS might be able to cut that subpack .. preventing the destruction of the others in the pack... Depending on the setup of the BMS.
   • Cons:
     1. To monitor and service each cell would require 1 BMS cell circuit for each and every individual cell.
     2. Strong individual Cells can not help carry weaker cells.

Not much to report. Except that my head is spinning. Also:

My Morningstar Tristar-mppt-60-150 controllers can be fiddled into charging Lithium. I'm getting that straightened out. They don't like to lose power. So the HVD contactor goes on the PV input line. LVD is handled by the inverter.

You can fiddle the charge voltages by using the RTS and fooling it into thinking it's very cold out. That way the charger stops charging earlier. Hmmm.

My size of system, even at LVD, lots of power left. HVD is my real concern. And I'm planning on charging to 80% for the first while to observe. May just leave it there.

REC BMS is about 700 euros once all the bits and bobs are in. Pretty sweet solution tho.

And I'm leaning more and more to cell monitoring with manual or occasional balancing.

Anybody with a good idea for a cheap 72 (6p12s) cell monitor(s) that's accurate? And reports to a PC?

Whoops. Let me start with the REC BMS. Not 700 Euros. 470 Euros. 700 Canadian. Whew.

And Tear Down Begins!

Can't begin to express the pleasure I derive from taking something so beautiful apart. Really put together so nicely. And all the bits and bobs are so well thought out.

http://creektreat.ca/wp-content/uplo...ssingtooth.jpg
Somebody's missing a tooth

Basically it was: take the connecting power cables off. Negative first! Disconnect the various control/BMS lines. Disconnect the cooling/heating hoses.

I take the smallest pack out first. So that's 2 48v packs tied together for 96. I test. The battery is at 92. It has dropped .1v since I first tested. I take the plastic cap off. Each cell tests at exactly 3.83. That's .01v lower than my initial bulk measurement (all cells together / 24).

http://creektreat.ca/wp-content/uplo...cv-pop-top.jpg
Top popped

This also lets me know that the cells are balanced. Bonus.

I then fiddle the lock down. Wow. Nicely done. And with only one bleeding knuckle I lift the pack out. Carry it to the bench. Battery on the bench baby!

http://creektreat.ca/wp-content/uplo...onthebench.jpg
Battery on the bench!

Man. I can lift 4 kws of storage power. And look at the size. Still. I was breathing pretty hard after the lift and carry. Smile. Yes. It was because of the weight.

I'll toss in one more. The BMS. Looks like 4 sections. Two control the two 12s packs. One is the master. The other? No idea. Maybe a section for the 24 that goes unused? Or is used in the big pack. Seeing as they are modular. Guess I'll find out when I get those apart.

http://creektreat.ca/wp-content/uplo.../06/cv-bms.jpg

Enjoy.

I love the pictures keep them coming and the great information.
Great project you have going.

Well. My lack of electronic experience is starting to show. I slowly wander through the world of BMS, BMU, Masters and Slaves etc etc.

I have discovered I can read the cell voltages direct from the BMS wiring harness. And there's a temp wire (I hope to read).

I found a manual for the 2012 with pin out diagrams for all the harnesses. I'm hoping they don't change with the 2014. Not counting on that as the 2013/14 got an upgraded chemistry.

One thing to ponder, for those of you who are more adept, note the BMS board has no big heat dissipating resistors. Do you think chip and resistor are on the cell? The harness diagram shows 1 - temp line, 1 "low register" and 6 to 12 cell voltages lines. Nothing else.

I have learned that Chevy went with passive balancing.

So the plan(s) right now are:
a)
- read and monitor the voltages
- balance manually as req. This gives me the advantage of reducing high cells or charging low cells. A simple RC balancer/charger might suffice.

Online reliable sources continue to point to high quality cells from LG, well maintained = very low cell drift.

b) the cost of a fancy BMS is the price of the battery pack and up. So I'm waiting to hear from China.

Charging:

After some odd research I have ascertained (to a reasonable level) that the Morningstar TS-MPPT-60 will support the voltage range I need. Morningstar is now claiming on their website that the battery chemistry is supported.

Further on the RTS hack. I still don't understand it. But you can set your BMS trigger alarm to switch on a resistor on the RTS that dramatically lowers or shuts off the controller. Thus saving contactor drama or having to shut down the whole system.

The Victron inverters continue to be the leading contender. Not just the very low idle draw, but the very low LVD. 37v. Which is suitable for a battery pack where the nominal voltage is 45.6. Fully charged is 50.4. And I'm really looking at operating between cell voltages of 3.4 and 4. Or 41 to 48v. Give or take a few hundredths of a volt.

It's been a wonderful adventure. Learning something new every day. Moving along much faster than I had planned. My start date was end of September. Looking more at July sometime now. And I could start charging today.

Sorry. No pics for today.

Right. So. I have had a lovely chat with Joe at Morningstar. On the website the controllers I have are said to support the Volt lithium chemistry.

Well. One way to find out. A back and forth with Joe. I pick voltages (conservative) that should suit the Volts charge characteristics. I download the new MS View. Very nice I must say. Input the updated values. Set the dip switches. Flash the eeprom. Easy peasy.

http://creektreat.ca/wp-content/uplo...ingstest01.jpg

The controller is now reading the first of the new battery packs.

Now: One step forward and one step back ...

As I've already torn one 2x48 pack out I figured. Hey. Why not use these packs for testing. So I double check the cell voltages. 23 cells check out at 3.83 or 3.84. Cell 12, pack one, 3.68.

I will wait to charge that pack. I'm trying to either borrow a programmable charger or buy one. Next on the list I guess.

Okay. Test #1 complete. A complete success. At aprox. 10 a.m. my batteries reached 48.26, went into absorb and then float.

http://creektreat.ca/wp-content/uplo...stcomplete.jpg

Unfortunately, duty called, and I missed the "absorb" phase. I have it set for 15 minutes.

This is tough as I was hoping to track the amperage at which it went out of absorb. I had thought the % of amp charge it went into vs exited absorb might have indicated the level of charge attained.

However, the voltmeter reads 4.02 on all cells. This is the exact setting I had hoped to attain.

Huzzah. Huzzah. Huzzah.

It appears that it took a titch over 700 watts to charge from 45.83 to 48.26. Very interesting given that it is a 2.2 kw battery. So 3.83/cell was basically at 50-60% charged. I think my 4.02 is about 80% charged.

And, I'm a bit "wowzah", as a .2 cell voltage change indicates 700 watts of storage. When I multiply by 6 packs. That's 4,200 watts of power. Or two full days of use for me.

Now to find the right inverter. Finish tearing down the pack. Charge up the batteries. Top balancing to 4.02. Yar. Matey. Grab your cutlass we're going overboard.

PS-as the charge seems to have balanced the cells. I am going to try the out of balance pack tomorrow. maybe. See if the charge improves the voltage discrepancy between cells. Again. Triple checked this a.m. All cells but one read 3.83. One reads 3.68. Dang.

I tore down the second segment. 120v nominal now 2x48 and 1x24. Tomorrow I test charge the 2x48s.

I also tested all the other cells very carefully. They all come in at 3.83 or 3.84. So the low cell is the only one. Whew.

For the pic of the day. The second part of the BMS. What are those big green things do you suppose?

http://creektreat.ca/wp-content/uplo.../cv-bms-02.jpg

Oh,

The big green things that look like electrolytic capacitors (but are not)? They might be reference cells or cabatteries.

The way the wires come out, they could be inductors. Don't look like any wire wound resistors I have seen.

Took some time to read your blog - very impressive. Keep up the work!

Steve

Thx for the vote of encouragement Steve. The blog is my message to my self 50 years ago. Smile. (Kind of kidding).

I've found some hints online that the BMS is on its own bus/communications network. Evidently I can fire it up if I find the right power connectors. Takes 12v power. We'll see what comes of that. I cannot program. And what I know about CAN is that its spelled c-a-n.

RESULTS: Day two. Charge tests.

As noted, I hooked up 2 x 48 to the controller. Well. Surprise. Surprise. The two batteries charged with 1370 watts. That's 685/pack. Within 25w of the previous single pack (710).

If that isn't good enough. Idle/power load on the TS with ethernet is about 75w/day. So most of that missing 25w can be attributed to the additional load of 1 battery vs 2 carrying the controller.

All 24 cells come in at 4.02. Exactly on target. There is startlingly little capacity fade. After charging (I tried 30 min absorb, seems to have made 0 difference) the battery stays at the charge as set on the controller.

I now have 3 of six packs ready for launch.

I have the inverter (a test inverter, small Victron) coming. I am contemplating doing two isolated installations. Or tough out the low power inverter until something better comes along.

I have 5 meter long M6 threaded rods coming. This will allow me to assemble the reconfigured packs.

Getting there.

What happens to time? It runs along. Gallops at times. Yet here I am. Still working. Getting things done between events. One step at a time.

The M6 rod came in. Threaded the packs together.

http://creektreat.ca/wp-content/uplo...eadedrod01.jpg

I know what you're saying. Wow Creek, Nice rod threading jig.

First discharge test. All continues to perform as per spec. Lovely when research works out.

Okay. So then the Ammeter/Voltmeter thingamabob came in. Complete with shunt. 18 bucks. Sheesh. Not sure how accurate it is. Seems to measure a bit off when compared to the Morningstar voltage report and what my Voltmeter says. Still.

http://creektreat.ca/wp-content/uplo...etertest01.jpg

So. Plug in the Victron 48-1200. Wire up the shunt. Turn all on. Run a drain test. Well. It's summer. Plug in the big screen and watch a movie. What you see above is the idle draw on the Victron along with the idle on the TV (off).

TV draws up to 280w and after two hours the ammeter records 518 used. Battery voltage is 45.72 the next morning. Interestingly the voltmeter says 45.8 and the morningstar says 45.83. Eh. Good enough for the funny papers.

Note: for this test I use the first battery I charged. Initially my settings used a 15 minute absorb period. The battery sat for 10 hours attached to the solar controller. So powering the controller overnight. The battery then sat for almost two weeks. Time is moving by.

Next morning I recharge the battery. I'm now using a 30 minute absorb. By the end of the absorb its only asking for 30 watts to maintain 48.26. So I think I have the absorb time dialed.

(I find very interesting that when charging the battery was cheerfully drinking all my pollen / dust clad panels were putting out. 550 watts. When the battery hit absorb voltage the power drawn dropped almost immediately to 250. Then tapered to 30. I missed the final number, but only by a few minutes. If you've charged lead acid you know how wild that is.)

Summing up:

The initial charge used 710 watts from 3.83/cell voltage. Recharge from 3.8v/cell was 650.

So one 48v battery (nominal 2.125kw) used 650 watts between miscellaneous loads. And recharged that amount in 1 and half hours. Primarily due to very dirty panels.

Right. On to battery installation.


http://creektreat.ca/wp-content/uplo...batterybox.jpg

Keeping with the light on the earth, recycle, reuse, repurpose theme. I use the pallet the battery came on, some left over 1/2" plywood scraps, to build the battery box.

And now I'm off to make some battery cables. Wish me luck.

PS-as always, more pics online. And even more detail (;)

All right. Long day yesterday culminated in

http://creektreat.ca/wp-content/uplo...th-victory.jpg

Took a bit of fiddle faddling, but with the help of an able assistant insulation was cut. Old batteries were moved. New to me batteries were placed.

And 12.75kw (nominal of course at 3.8v) at 48v of lithium storage is in place.

I had thought to get this done by September. But my lead acid began to show serious signs of decay. And, hey, it was Canada Day coming up. So I set that as my deadline and voila.

http://creektreat.ca/wp-content/uplo.../lith-live.jpg

Canada's first lithium based recycled Chevy Volt SESS launches. Huzzah!

Dude, that's awesome.

I love this project. Great work.

It is truly rewarding to take a risk and come out with a win.

Early days. Well. Day. One day of recorded input/output. But the increased efficiency is startling. I love the near absence of voltage drop on surge. My lights used to flicker noticeably when the fridge kicked on. Not sure if it's the lack of voltage drop or the easier time the 48v inverter has converting to 120v.

Ran the dishwasher. And the fridge still kicked on. I was worried that going down a bit in power with the relatively small Victron might cause problems there. But nope. So all is well on Creeky's camp.

I'm also kind of shocked how bad the lead plates in the old batts are. When I checked them last summer they were pretty clean. But not anymore. So I'm going to take them to the recycle depot next week. I had thought someone else might get a few more years out of them ... uh. no.

Still on the hunt for a BMS solution. I'm probably going active. I think I have it figured out wiring wise. Basically 12s6p. Kind of funny. Each battery is 3p per cell. In 12s. And i'm going to balance the 6p tied together in 1 12s string.

Makes my pack 3p12s6p?

The morningstar controllers are both working to spec. Wiring all tested out perfect. All batteries were 47.6 after the first night of discharge. Pack recharged in 2 hours. So all is good there.

At 12v I was over paneled (1kw per 60a controller) to compensate for late fall/early winter cloud. Now I'm getting the full 1kw out of each set. Should be interesting when the cold season comes to see what maximum watts I can pull.

I think I have more "float" voltage adjustments to try. Along with wiring clean up and installation fiddle faddlin' to do.

But she's up and running. Feels good.

Check with the hybrid and EV bicycle builders. They regularly use 48V packs.

Thanks NiHaoMike. I have been into the endless-sphere and diyelectriccar sites. Lots of info there. (where's the head spinning icon?)

I like this BMS the best so far. Based on the TI bq 96940. I don't know that they are actually shipping it. I would like to find someone who would sell me 1. These guys seem to want sales in the 1,000s.

Bigmouse on diyelectriccar posts pics of his reading of the OEM BMS. I can see how that might work.

IamIan pointed out a great idea for me. And I will be looking at this simpler solution. Thanks again IamIan. Took awhile for what you wrote to sink in. Super appreciated.

Initially of course I'm going to monitor cell voltages. If, as it appears is the case, all the voltages remain more or less in balance. I will keep to a more manual course.

I'm traveling a lot this summer. Which is getting awkward. I just started the system and already I'm away for three days. Would kind of like to be closer at hand to monitor and correct. Oh well. Fingers crossed. "Cloud" monitoring is probably next.

I'm trying to leave some loads (the fridge, internet 24/7, lights) on the batteries so they don't remain too fully charged. Trying for that 5,000 discharges range. Smile. And on that note, I have found some graphs/charts that indicate it's best to keep your discharge to 3.4/cell for longest life. I am set up at 3.2. Will be keeping an eye on that. Of course, to date, my lowest discharge is 3.8.

Looking forward to charting solar watts in/power out and voltages with more data points than day 1.

Introducing the cell log 8

Initially I clipped the wrong fin and had inserted the dang thing upside down. And for this reason the reader didn't work? Okay. Well. I clipped the other fin this time. And looked carefully at the picture of the fellow on endless-sphere using his cell log 8. Voila.

I can now measure up to 8 cell voltages at a time. My plan is to take pictures with my camera. And then track. Certainly should speed monitoring.

http://creektreat.ca/wp-content/uplo...6/07/batt1.jpg

Here's a pic of the "bad" battery readout. Turns out 3 cells are low by .2v. That's a lot really. Yet the cell voltage isn't dropping and the cells seem unharmed by the crash. Was there a problem with the OEM battery charge/monitoring? Who can say.

So I am going to charge to balance and then exercise the battery some to see if I can return it to normal function.

That would be 2.125kw of sweet.

Note: this battery is not part of my install. ;)

Very nice progress.

I'm not sure if they ever fixed it, but the cell log 8 does not pull evenly from all cells (assuming 8 are connected). I believe cell 7 and 8 are not drawn off of, so it will create an imbalance over time. There is a modification online to fix this and it is pretty easy to do.

Thx for the tip on the draw. I didn't buy the 8s. I bought the 8m. It doesn't log. Just gives the voltages. Appears accurate right out of the box. Short term use and manual monitoring. Don't want to do that long term. :)

Update: Ran a load test yesterday. Basically ran my loads, (a/c on; TV; internet; lights; fridge) for a full day from the completion of the absorb cycle around 11 a.m. to 9 a.m. today. Took about 5400 watts to fully recharge (includes daily use). Voltage went from 48.32 to 45.48 overnight and back to 48.32.

That's pretty close to 2 days of "winter" use. So have to say I'm happy with the results of this test. 5kw draw down and recharged by noon. That'll do.

The Victron inverter is too small. Watching TV (49" cfl based LCD tv) with the a/c running, internet on (700w load): when the fridge kicks on I got a "beep" from the laptop running the Netflix movie. Everything keeps going. But it probably indicates a load max. ;)

Time for a led lcd tv I guess. Really could use a bigger inverter. Say 2000w. Or 2200. I love the no load draw on the Victron. I mean 10 watts/hr? But a bit more surge for the fridge would be nice. Waiting for Victron or similar to do a 60hz model.

What about multiple inverters? Dedicate a 100V/50Hz unit to motors and that will reduce power usage of those loads by about 17%.

That's what I've been thinking about. Multiple inverters. Not sure how to isolate the two inverters tho.

Guess i need something else to research. Or wait until somebody releases a parallel inverter for 60hz.

Ran my first full pack voltage monitor. The widest variance on cell voltage between all six batteries (72 cells) is .01v. This is within an acceptable range.

Most of the cells are within .003 of each other.

Will monitor weekly and track. Very nice that I've been able to plug in the OEM cable and read from that with the cell log 8. I take a pic of each battery readout and then compare at my leisure.

Have adjusted my float voltage. Still not quite right. So will be adjusting that.

Continuing to note exceptional efficiency. Have not used the gas stove as I have the induction stove top going. Very efficient. Coffee was ready this morning in record time. A/C running from 2 till 8-9 pm. Internet on 24/5 now.

Had a wonderful adventure with making a mess of port forwarding. I would like to be able to monitor the batteries remotely. Well. Let's just say after two hours I was relieved to be back where I started.

I had a nice adventure recently. You see I have one bad battery out of the Volt pack I acquired. This 48v battery has one cell at 3.62 while all the other cells come in at 3.83.

What to do?

Well. I went to see John. The rocket scientist. He's a tech from back in the day, when Canada's NRC was launching rockets into space.

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Beasties

Now he's this pushing 80, fit and full of laughter, single fella with his dog. He supplements his pension by fixing radios. Old radios. Radios the size of apartment fridges with fancy wood cabinets and tubes. Radios so old they were made in places like London Ontario or Utica NY.

So who better to call on to see about this wonky celled battery?

In the meantime I had received my "cell log 8M." This contraption lets me measure 8 of 12 cells at a time.

And it shows I don't have one wonky cell. But 3. Yikes.

It also shows that the cells aren't losing power. They are as stable as all the other cells. It's just that they're exactly .2v lower than the other cells.

Huh?

I won't go on and on with the details ;). Suffice it to say that John and I start out with a small constant current power supply. Hooked it up to wonky cell 1 and 2. 7.45v. And set it to 2.5 amps.

Well. Two hours and supper and lawn mowing and ... later. The battery cells had risen from 3.62 to 3.75. A bit more than 1/2 way.

Well this won't do.

So John dusts off the beast. A huge ancient unregulated power supply capable of kicking out 20 amps.

He asks me, do you think the battery can handle it?

Yup I say. Pretty sure. Theoretically I should be able to charge at 45 amps safely. And 135 amps if I'm feeling lucky.

Then he gets out this lovely long piece of plastic. We'll put this .5 ohm load in between the charger and the battery for safety. He says.

You can see it on the table in the photo. It's the long white bar
wrapped with ni-cor wire. Or more commonly known as the wire that your toaster uses to burn your toast.

I'm supressing laughter already when we get all hooked up. Only one sparkle event as the attachment clips are so big. Pieces of wood are found to use to insulate between cells.

Alright says John. Here we go. Click. Nothing. He turns the dial and spins the knob. Nope. Nothing.

A short (heh heh) examination of the beastie reveals that the knob screws are loose. So some tightening goes on. Then, as seen in the pic, the "warning light" falls off.

Now that is funny. And we share a chuckle.

Finally, drum roll please, the switch is flicked. The knob is dialed up. Success. The light on the resistor goes on and the cell log begins to show power climbing in cell 3.

So. Long story short. The charge up of the cells 1, 2 and 3 (according to the cell log) is complete. After 3 days the voltage remains stable. I will try charging the whole battery now. Early impressions are that the battery is stable and the problem lay elsewhere.

Which is great 2.125kw news. The cause of the low cell voltage is a mystery. Bad BMS?

It was a most pleasurable adventure. With drama. Things fixed. Ancient equipment dusted off and put to good service.

Oh. And John shared with me pics from our rocketry program circa 1968. Very cool. There's a good one of him assembling a silver zinc battery. Which he discharged to 0 before charging to the specified voltage (2.something). And used potassium hydroxide for the electrolyte.

Neat.

Nice story. I really like this project.

Thx Pinballlooking. Its been a pleasure reading your journey as well. (One thing I noticed about the Volt batteries, as posted above, is there were 3 low cells on one battery. After charging and watching they've held up perfectly. Leading one to wonder why they were so low. And even more so, consider if it was the BMS or volt charger at fault. Something for Volt owners to wonder at also.) smile.

On with the show

So after 27 days I have sent 112kw of solar power to the batteries. I have sent 94kw of solar power to my inverter. And I have done some very bad math.

I take an average of 7 days of charging back when I had the batteries under testing. There were days when the batteries being charged for the first time then sat, hooked up to the solar charger, and then topped up the next day.

This average indicates a solar controller daily load of 130w per controller.

Hence, (18kw of loss - 7kw for the 2 solar controllers load) * 92% for inverter/cable loss = 80% system efficiency.

And it would appear the batteries are aprox 91% efficient.

Note: take none of this too seriously. The solar controller(s) load could be off by a factor of 1.5. And there are other problems. Accuracy of the $18 ammeter by ex.

Yet for all intents

However, be that as it may, and all that. Total battery voltage variance is now at .02v.

Cell balancing?

I appear to have found a simple method of using high cells to top up low cell voltage. both lowering high cells and boosting low cells. So cell balancing in a very hands on way. More on that after further testing.

My quest for a balancer/bms continues. I found some really good docs on the balancing/bms chips that the Volt uses. I haven't had time to read them yet.

Update complete!

PS-still gives me a tingle when I, as I did last night, turn on the dishwasher before going to bed. After watching TV or listening to music late into the eve. Huzzah.

PPS-yesterday was cloudy in the a.m. with full sun bursting onto the panels at peak generating time. My "summer angle" set of 1kw of 8 year old panels delivered 965 watts. Interesting given a) age of the panels; b) haze/dirt affecting the solar gain c) the high temp of the panels on a very hot afternoon d) prorated at 20% efficiency loss over 25 years should mean that the panel set is only capable of delivering 930 watts peak.

I would say 965 is full on original power spec given the panel temp and conditions.