chevy volt 12s/18s charging & ballancing

[altermontrealiste]

Hi

For a long while, people have looked for options that are powerful and cheap for e-bikes ; a respectful bike in 2015 doesn't use lead-acid as there are good options for cheap lithium that are easy to set up. Buying cells that come from cars seems a good option (if you can find them ; they should become more and more accessible) and, having gone trough building a konion pack (learned a lot, but 20s/14p took me months) and having tested cells one per one, this looks easier ; quality of the cells is warrantied by conservative BMS settings (for the chevy volt). You can find some salvage cars for cheap in the usa, get the batts out and re-sell the parts to cover the cost .

A complete chevy volt pack is a T-shaped, 435#ish pack inside a fiberglass box ; one can easily remove the top and separate it in 3 blocks to transport in a car (all in an hour's time), and once it is skimmed of it's unneeded parts, you can lift them manually. Once home, you can separate it and have 12s and 6s packs just by unbolting. 12s (to upgrade 4 acid-lead 48v) and 18s (to upgrade 5 acid-lead 60v) 45Ah can easily be made. Nissan leaf modules look easier to work with but it's definitely not hard to work with chevy volt ones either ; plus, the cells are mounted on a liquid cooling/heating system (Québec winters need a heating system ; arduino+liquid pumps+DS18b20 = temperature monitoring and not far from temperature controll).

BUT, they don't have as much info on them as konions or hobbyking lipos : the ES community hasn't played enough with them yet I'm a curious noob, I have some questions, hence this thread to make sure I'm using them safely and don't end up burning my appt. Also, there are some contradictory infos on them...

Some threads already exist (http://www.diyelectriccar.com/forums/showthread.php/2012-chevy-volt-battery-93101.html), this one is about charging and ballancing 12s/18s packs


The challenge:
I want to design a suitable system to charge, ballance and monitor (for LVC) and stop discharge when at LVC. The less expensive, the better... but not sacrificing quality and, more importantly, battery durability. For a couple of reasons, commercial BMS don't seem to cut it.

Chemistry:
Hybridautocenter says they are LiMn2O4/LiNiO2 (no cobalt), other sources, like DocBass and http://batteryuniversity.com/learn/article/types_of_lithium_ion says it's NMC ; I don't know how having cobalt it will affect charging/discharging/ballancing.


Charging method
Charging a 45Ah pack will need a beefy p.supply, and most BMSs limit charge to max 10-15Ah... and the best commercial option without blowing the bank I found is 15Ah (greentime) ; 48v meanwells / server p.supply + Fechter's Mini Meanwell Limiter V.3 seem the way to go.

What would be maximum suitable charging C rate?


Ballancing method
dnmun told me (pm) "you will need a large balancing network since the cells are large" ; if I understand well, larger cells need larger resistors to drain more amps individually in case of pack imballance.
would a mod like http://endless-sphere.com/forums/viewtopic.php?f=14&t=31313 achaive that?

Konion cells (li-manganese) almost dont need constant ballancing ; how does it apply on chevy volt chemistry... is ballancing all the time necessary?

Has anyone used HobbyKing Battery Medics to ballance while charging? What about operation (discharge to ctrl, not discharge mode on battery medic)?


BMS plugs
each module (12s and 6s) has BMS plugs, worst case scenario, I could weld / glue ballance wires

does anyone have the pinout? does anyone know where to buy those plugs?

Thanks
Guillaume

 

[dnmun]

the sense wires should come with the BMS.

 

[altermontrealiste]

the sense wires should come with the BMS.

yes, definitely on the bms side ; on the batt side, the 6s and 12s packs have sense wire plugs already (my packs didn't come with the wires)

 

[liveforphysics]

You only need balancing to match the self-discharge rates and differences in coloumbic inefficiency.

For quality EV grade cells, this means you would likely have more balance current than you ever needed even if you only had say 5mA of bleed current. If you need more bleed current than that, you have a defective cell and it's going to gas out rapidly if it has that rapid of self-discharge.

 

[John in CR]

With the Volt modules I have on the way, I plan to just bulk charge to a conservative 4.1v/cell. I'll have cell level monitoring with low voltage alarms using $3 per 8 cell units from HobbyKing. Installing a switch on each negative of the monitor/alarms units turn them on and off, and use their connector to access cells that get out of whack. I've found that with conservative top of charge voltages and conservative depth of discharge (DOD) that a human BMS is lower risk than the multitude of failure points that come with BMS's. It does require paying attention and being familiar with your pack and its limits, which is why a system without a full control of the pack BMS cannot be sold to the general public.

Packs with well matched cells stay amazingly well balanced with conservative use. Until now I've never even bothered with live cell monitoring. I'd check cell voltages occasionally, and only have to bring out of whack cells into balance maybe once or twice a year. I'm adding the cell voltage display and alarm units now more for the cool factor for those who look at my bikes than out of actual need. I have some deep discharge rides coming up, so I will need for that, because I plan to fully discharge one pack before switching to the other pack.

 

[parabellum]

With the Volt modules I have on the way, I plan to just bulk charge to a conservative 4.1v/cell. I'll have cell level monitoring with low voltage alarms using $3 per 8 cell units from HobbyKing. Installing a switch on each negative of the monitor/alarms units turn them on and off, and use their connector to access cells that get out of whack. I've found that with conservative top of charge voltages and conservative depth of discharge (DOD) that a human BMS is lower risk than the multitude of failure points that come with BMS's. It does require paying attention and being familiar with your pack and its limits, which is why a system without a full control of the pack BMS cannot be sold to the general public.

Packs with well matched cells stay amazingly well balanced with conservative use. Until now I've never even bothered with live cell monitoring. I'd check cell voltages occasionally, and only have to bring out of whack cells into balance maybe once or twice a year. I'm adding the cell voltage display and alarm units now more for the cool factor for those who look at my bikes than out of actual need. I have some deep discharge rides coming up, so I will need for that, because I plan to fully discharge one pack before switching to the other pack.

John, can you link mentioned voltage alarm? Have you tested drain on connected channels while first negative is off?

 

[liveforphysics]

I had voltage monitors kill a number of my RC packs. Use caution with anything you plug into your cells for long periods.

 

[dnmun]

Otmar's hack for the depletion mode mosfet to allow the cellogs to pull power from the top cell in the 8S cellog was a work of genius. on richard's cellog hack thread. that keeps the cellog drain from imbalancing the battery by insuring that the power for the cellog is shared by all cells measured.

 

[altermontrealiste]

[...] say 5mA of bleed current. If you need more bleed current than that, you have a defective cell and it's going to gas out rapidly if it has that rapid of self-discharge.

That makes it clear for me on BMS bleed current having no relation to cell Ah (ie, bigger cells won't need more drain current)

 

[altermontrealiste]

With the Volt modules I have on the way, I plan to just bulk charge to a conservative 4.1v/cell. I'll have cell level monitoring with low voltage alarms using $3 per 8 cell units from HobbyKing. Installing a switch on each negative of the monitor/alarms units turn them on and off, and use their connector to access cells that get out of whack. I've found that with conservative top of charge voltages and conservative depth of discharge (DOD) that a human BMS is lower risk than the multitude of failure points that come with BMS's. It does require paying attention and being familiar with your pack and its limits, which is why a system without a full control of the pack BMS cannot be sold to the general public.

Packs with well matched cells stay amazingly well balanced with conservative use. Until now I've never even bothered with live cell monitoring. I'd check cell voltages occasionally, and only have to bring out of whack cells into balance maybe once or twice a year. I'm adding the cell voltage display and alarm units now more for the cool factor for those who look at my bikes than out of actual need. I have some deep discharge rides coming up, so I will need for that, because I plan to fully discharge one pack before switching to the other pack.

If I understand well, and if I get a p.supply that is precise enough, I would bulk charge them at 4.08v/cell and finish it off with RC charger on ballance mode up to 4.1v/cell ; that should be sufficient to keep them ballanced and not explode while riding?

No need for constant ballancing
"human BMS is lower risk than the multitude of failure points that come with [electronic] BMS's"

"well matched cells stay amazingly well balanced with conservative use"
besides not charging too much and discharging beyond say 3,3v, what would be convenient for discharge amperage (I read 200A on HAC) and charge amperage (no more than 1c/45Ah?)

HobbyKing™ Cell Checker with Low Voltage Alarm could be hacked to achivate a relay/opto with the battery wire on NC

if ballance current dont need to be higher than smller cells, O2Micro OZ890 chip could do a nice job and help monitor cells with an arduino

 

[veloman]

I have one of these modules and the cells came perfectly balance and so far are staying so after a month of conservative use. My Leaf Modules are also staying extremely well balanced. I don't use a BMS on either.

 

[999zip999]

Where are you located ? 45ah is big on a bike.

 

[altermontrealiste]

Where are you located ? 45ah is big on a bike.

I'm in Montréal

45Ah is indeed big for a pedal-bike, but it goes well on a 48v/60v e-scooter that has 4 to 5 22ah lead-acid ; could be nice on a e-moto

 

[altermontrealiste]

I have one of these modules and the cells came perfectly balance and so far are staying so after a month of conservative use. My Leaf Modules are also staying extremely well balanced. I don't use a BMS on either.

Great ; that's reassuring

When we talk about conservative use, is it only HV and LV?

Not too afraid about overdischarge (48v@200A cont. / 350A burst for >9.5KW) on a 500ish watts vehicule.

I suspect charging too hard will use the cells more ; what would be maximum / conservative / minimal charging amperage?

 

[veloman]

I've been using it on my wife's scooter which pulls 75amps peak, maybe 40a during most riding. I charge using a very slow 2amp rate charger I put together using laptop style power supplies, max 48.4v. Controller cuts out at 42v (3.5v/cell) so it's pretty safe I think. The battery gauge (48v sla) seems to work very well for this 12s lithium pack. Halfway is about 50% charge, maybe 60%.

These modules would be my first choice for building an emoto again. As long as the 45/90v configuration works. Cells already welded together, with balance plug. Less work than the Leaf modules.

 

[altermontrealiste]

I charge using a very slow 2amp rate charger, max 48.4v.

These modules would be my first choice for building an emoto again. As long as the 45/90v configuration works. Cells already welded together, with balance plug. Less work than the Leaf modules.

2 amps for a 45Ah seemed to me to be almost too low to charge (would fill it up in 22,5h...) ; anyone tried with more?

Balance plug is a nice feature... or would be if I had tought to buy them too (seller seemed to want to keep em) ; does anyone know where to buy some cables or, even better, buy just the plug?

 

[liveforphysics]

I charge using a very slow 2amp rate charger, max 48.4v.

These modules would be my first choice for building an emoto again. As long as the 45/90v configuration works. Cells already welded together, with balance plug. Less work than the Leaf modules.

2 amps for a 45Ah seemed to me to be almost too low to charge (would fill it up in 22,5h...) ; anyone tried with more?

Balance plug is a nice feature... or would be if I had tought to buy them too (seller seemed to want to keep em) ; does anyone know where to buy some cables or, even better, buy just the plug?

In the LEAF Nissan cells handle a CHAdeMO dumping 125A into them for the lower ~70% of the cell capacity, then it tapers to something like 50A charge for 70% to 100%.

 

[veloman]

I charge using a very slow 2amp rate charger, max 48.4v.

These modules would be my first choice for building an emoto again. As long as the 45/90v configuration works. Cells already welded together, with balance plug. Less work than the Leaf modules.

2 amps for a 45Ah seemed to me to be almost too low to charge (would fill it up in 22,5h...) ; anyone tried with more?

Balance plug is a nice feature... or would be if I had tought to buy them too (seller seemed to want to keep em) ; does anyone know where to buy some cables or, even better, buy just the plug?

The only reason I am charging at 2a is because that's what I had available in my junk pile - and it works. It gets plugged in overnight, and rarely use a full charge, so it doesn't matter. Call me cheap, but I don't spend money if I don't have to.

Mine from HAC came with the orange balance plug wire. I just attached JST-XH balance leads to it. Way cleaner than routing 13 wires myself around the cell tabs. It's already done on the Volt module. Check ebay for the plug.

 

[altermontrealiste]

I charge using a very slow 2amp rate charger, max 48.4v.

These modules would be my first choice for building an emoto again. As long as the 45/90v configuration works. Cells already welded together, with balance plug. Less work than the Leaf modules.

2 amps for a 45Ah seemed to me to be almost too low to charge (would fill it up in 22,5h...) ; anyone tried with more?

Balance plug is a nice feature... or would be if I had tought to buy them too (seller seemed to want to keep em) ; does anyone know where to buy some cables or, even better, buy just the plug?

The only reason I am charging at 2a is because that's what I had available in my junk pile - and it works. It gets plugged in overnight, and rarely use a full charge, so it doesn't matter. Call me cheap, but I don't spend money if I don't have to.

Mine from HAC came with the orange balance plug wire. I just attached JST-XH balance leads to it. Way cleaner than routing 13 wires myself around the cell tabs. It's already done on the Volt module. Check ebay for the plug.

Laptop charger look like an interesting sollution : they are widely available, could almost get them for free. Will invest to have a charging setup that goes the full potential, but seems a good idea to start. Can almost any laptop charger, put in series to have a convenient voltage, do the job (aka cc/cv algorithm)?

I will attach 2x 6s ballance wires on the plug : found http://www.digikey.ca/product-search/en?x=0&y=0&lang=en&site=ca&KeyWords=0015247180 that has been identified on another thread as suitable... but I might just solder wires on the plug.

 

[altermontrealiste]

I charge using a very slow 2amp rate charger, max 48.4v.

These modules would be my first choice for building an emoto again. As long as the 45/90v configuration works. Cells already welded together, with balance plug. Less work than the Leaf modules.

2 amps for a 45Ah seemed to me to be almost too low to charge (would fill it up in 22,5h...) ; anyone tried with more?

Balance plug is a nice feature... or would be if I had tought to buy them too (seller seemed to want to keep em) ; does anyone know where to buy some cables or, even better, buy just the plug?

In the LEAF Nissan cells handle a CHAdeMO dumping 125A into them for the lower ~70% of the cell capacity, then it tapers to something like 50A charge for 70% to 100%.

If I got the correct data for Leaf cells (66Ah), 125A is 1,9C for the lower 70% (cc phase of charging?), is that to say one could charge a 12s45Ah chevy volt up to 85A cc phase then (when at, say 3,9v/cell) limit current to 40Ah for 3,9v/cell up to 4,1v/cell?

 

[veloman]

I've been using laptop style supplies for a few years (put two in series with a 48v sla charger for a 24s lifepo4 pack).

It works. but I am not an expert on charging. There a million different laptop supplies out there. Not all will work in series. I think if they come without a ground wire (AC 2 plug instead of 3), then they should work in series. Add up total voltage and current is limited to the lowest amp supply. I got a box of them from a friend for free, and a few at yard sales etc. Lots on ebay for under $10ea shipped. But really, there is no value, you should be able to get them for next to nothing. There's just so many out there. That's why I use them.

I just bought some Meanwell supplies to charge my Leaf pack at 14a. Teslanv has some. Probably the best charging setup for your money, and it being good quality.

 

[JoeReal]

Hey guys,

I just got my Leaf packs set up (pack 1- 6 modules pack 2- 5 modules) now I want to top balance them individually. I only have a iMax B6 at the moment; I'm not sure what the best charge rate would be best to charge from 3.75 to 4.1V. C/10? I've never used a Lipo balancer before, so any help would be greatly appreciated. I am also not sure how to set the max voltage.

Thanks,
Joe

 

[altermontrealiste]

Hey guys,

I just got my Leaf packs set up (pack 1- 6 modules pack 2- 5 modules) now I want to top balance them individually. I only have a iMax B6 at the moment; I'm not sure what the best charge rate would be best to charge from 3.75 to 4.1V. C/10? I've never used a Lipo balancer before, so any help would be greatly appreciated. I am also not sure how to set the max voltage.

Thanks,
Joe

I would bulk charge to 4,08v/cell, under 4,1v/cell (you could bulk charge to 45v for your example), then use the ballance charger at 4,1v/cell (choose li-io mode) ; bulk is quicker and you could inject 20A-bulk in your leaf cells, iMax B6 will take longer, but will adjust charging for you.

c/10 charging is good for lead-acid ; lithium can charge 0,7c, maybe more : that is one info I would like to confirm with the site's gurus concerning chevy volt and nissan leaf modules

 

[JoeReal]

I would bulk charge to 4,08v/cell, under 4,1v/cell (you could bulk charge to 45v for your example), then use the ballance charger at 4,1v/cell (choose li-io mode) ; bulk is quicker and you could inject 20A-bulk in your leaf cells, iMax B6 will take longer, but will adjust charging for you.

c/10 charging is good for lead-acid ; lithium can charge 0,7c, maybe more : that is one info I would like to confirm with the site's gurus concerning chevy volt and nissan leaf modules

Thanks for the info altermontrealiste!

OK, so I tried bulk charging my 49.2V pack with a 48V 7.2 amp power supply, but the power supply keeps shutting off on thermal overload... I guess I need to look into getting/making current regulator, hopefully one I can adjust. Any ideas?

I'm now using a 24V power supply pot'd down to 20V, I have it connected to two and a half modules at 4.0V each cell. It seems to be doing well; not overheating, cells steadily increasing in voltage.

I am charging one cell with the iMax B6, also doing well, using the Li-Io setting @ 4.1V. Taking forever, but it feels good to see some steady increases.

Any ideas would be greatly appreciated.

Thanks for the help guys.

 

[dnmun]

how do you know the power supply is shutting down for overheating? does the fan turn on at all?

how can you charge a 49V battery with a 48V power supply? 12S of lithium ion should be charged to 50.4V also.