Arkmundi's saga making & maintaining an A123 AMP20 battery

[arkmundi]

Update June-2013
Several things together - long trip, running down battery as much as I was comfortable with -and- charge it up with a kill-a-watt meter attached. Results:

• I ran it down about 15 amp-hour, or close to the expected capacity, figuring that to be about 18-19ah
• I was pleasantly surprised that even towards the end of my run, the voltage held; when I got back home it was around 39 volts still; I'd expected it to be down around 34-36 volts
• checked each cell and lol, they were all around 3.3 volts, within the spec; lowest was 3.2 volts; that was the most amazing stat, as with my prior experience and running without a BMS, I would have thought some greater range and that I might see a cell or two below 3.0 volts
• I got a kill-a-watt meter to plug my charger into, so I'd know exactly how many kwh it takes to charge up; this charge, for ~15ah replacement charge took 0.41 kwh
• I pay around 19 cents a kwh for my power at National Grid, using the Mass Consumer Energy greenstart label, so that's about 8 cents for that run
• I'm consistently getting about 1 mile per amp-hour on average, for my terrain and weight; so I'm figuring about 0.5 cents per mile; compare that to my Ford Escape Hybrid at around 30 miles to the gallon at current $3.524 per gallon, or 11.7 cents per mile
• like for those who want the hard facts on why local travel via ebike
• this run was down to Union Station for the train into Boston, then up to the State House to lobby my senator for H.2935Transition to a Clean Energy Commonwealth, then through the Emerald Necklace Parkway to the the Museum of Fine Arts to see the new film One Track Heart, the story of Krishna Das, then back onto the beautifully marked bike lanes of Boston to catch the train back to Worcester and home
• I love being more or less retired from working too much without children or grand-children or other relational preoccupations, so I can do what I want!
• I had no fewer than 5 kudos from people on the street for my bike; It's because of that crazy Cree blue LED light, back mounted, so its shinning directly on the hub motor, highlighing it - people know its an ebike just with a glance; one guy at the Backbay station: "I want that bike!" Look I'm not used to that kinda praise. No one for instance has ever said "I want that body" or "I want that mind" or "I want those clothes" or any such. But my ebike, yea, they want that!

Note - figure .05 kwh/ah

 

[arkmundi]

Luggage carrier
From another post about the Aosom bicycle cargo trailer:

http://www.aosom.com/d-2404/Aosom-Bike-Bicycle-Cargo-Trailer-Yellow.html
... which I purchased through Amazon for $90
One of the nice things about this trailer are its quick release wheels, intended to compactify for storage, but which means I can re-purpose the wheel assembly for:

As with every aspect of this saga in making a workable ebike, I don't seem to have the knack for getting it right the first time. So, several attempts and failures and re-tries. The two details that needed working through were the axle assembly and the hitch.

Final detail on the axle required going with square steel tube, cut to 22", with a round copper pipe flange on the inside, cut for the quick-release bolt. This then attaches to the luggage bag with two bolts. Final detail on the hitch was two pieces: 1> an aluminum bar that extends the rack backwards and keeps the luggage handle above the wheel, and 2> a hitch so the weight of the luggage carrier is held by wire directly to the rack.

Works like a champ now! So, I'm done with backpacks and what not. It all goes into this nifty carrier. And when I'm at my destination, it quickly unhitches and acts just like any number of wheeled luggage carriers, just with bigger wheels.

 

[docnjoj]

Ya gotta get a trike!
otherDoc

 

[arkmundi]

Ya gotta get a trike!
otherDoc

No way! There's a logic at work here. I use bike, bus & train to cover the full gamet of my travel needs. So the whole contraption has to go on, without protest from the drivers/attendants. The trike WON"T WORK! Our RTA allows bikes - they have a carrier for two bikes on the front of the bus. I've put my ebike on without incident. Same with the MBTA commuter train to Boston. My contraption I believe will work out OK. The next test is on the bus - to see if my 30 inches of wheel base will go up the bus steps and into the aisle.

 

[arkmundi]

4th of July Sacred Interdependence Day
Alright then, making some progress on my solar ebike roadshow. Aiming to inspire the next generation at their high value, high consciousness art faire July 4th to 7th at Earthlands. For those not yet aware, Earthlands is a long standing non-profit, get people back to Nature place in Petersham, the greenest place in Massachusetts. That's because Harvard has its forest research center there, and then along comes the Trustees of Reservations, the first conservation land trust in the world, and the Commonwealth with state forest and conservation areas. All that lead to a town that has 60%+ permanently protected wild lands. Most of the rest are traditional New England family farms. The Heartbeat Collective is an urban eco-village group of artisians and other new-types looking to make a better world.

So I'm putting together my solar panel and charge controller (thread: which battery chemistry is best for solar charging?. Should be able to ride with this 120watt 12volt panel doing duty the whole way. The Genasun charge controller is a MPPT boost controller which will boost from 12v to 41.8, nominally 36v, a perfect charge for my pack. More latter when I've seen it in action.

 

[miro13car]

Arkmundi,
great posts of yours.
I also ride on A123 20Ah cells 12S and can confirm what you write, it seems those A123 sabilize to 39V minutes after ride even after 15Ah used.
I would not ride on the on the motor you ride , I prefer more sophisticated and smooth computerized USA - designed self contained ebike drives /riding experience is all to me/.
But your enthusiasm is inspiration for me.
Also want to get to solar panel charging.
In your update June 2013 you say
" on average one mile per amphour"
is it not mistake some kind?

 

[arkmundi]

I also ride on A123 20Ah cells 12S and can confirm what you write, it seems those A123 sabilize to 39V minutes after ride even after 15Ah used.

Great to know that there are others in the small sub-community dedicated to the very best current battery tech.

I would not ride on the on the motor you ride , I prefer more sophisticated and smooth computerized USA - designed self contained ebike drives /riding experience is all to me/.

Can you be more explicit about the motors you're using and like? I'm always shopping for the next venture. FYI, I've go 30 people signed up for my ebike workshop, starting late summer and going through the fall. So I'd like a list of the best price/performance motors available from reputable vendors.

But your enthusiasm is inspiration for me. Also want to get to solar panel charging.

I just got back from my inaugural run of a solar ebike and my enthusiasm right now is off the charts. Exhilarating to the extreme. Ran into people I know on Highland street, stopped to chat and show off and everyone is amazed that its possible to have a solar ebike, and independence from the great empire.

In your update June 2013 you say "on average one mile per amp-hour" is it not mistake some kind?

No. Its a rule of thumb that I'm using. My pack is 20ah and I expect 16 miles on it without a recharge, taking it down to roughly 20% of capacity. That's about 1 mile per amp-hour, accounting for starts & stops, hills, etc.

 

[999zip999]

Love.

 

[arkmundi]

So I'm putting together my solar panel and charge controller (thread: which battery chemistry is best for solar charging?. Should be able to ride with this 120watt 12volt panel doing duty the whole way. The Genasun charge controller is a MPPT boost controller which will boost from 12v to 41.8, nominally 36v, a perfect charge for my pack.

Alright then, got everything wired, packed and tight, ready to roll. Rolled right into the 350ma.org People's Assembly at Worcester State for demo. Figured nice place to showcase and TEST. 6 hours of the panel in the sun. I disconnected the battery from controller. So the only things connected were the panel, the battery and the solar charge controller. What I expected was a full charge and plenty of zip to go. I didn't charge the battery last night like I usually do, so the battery was down probably to around 70% of capacity.

What I got when I started back home was a slushy assist from the hub, like the battery were low or missing a cell. Hmmm, I thought all the way back. Then I checked each cell voltage, all around 3.3 and one cell was 0.0. That's in zip. Whaaatttt the frelling frack is that jack? Its not only like I got no charge at all from the panel, but it sucked one cell dry!!!!!! If the solar charge happened as advertized, then all cells would be up to an average of 3.48v or 3.5v to 3.6v as is typical for this pack and the pack in the range of 41.8 as the solar charge controller was supposedly designed for.

Help!

 

[winkinatcha]

'Kay... really dumb question, but did you/do you have a diode so that the batteries can't discharge back through the solar cells?

Joe

 

[arkmundi]

The solar charge controller is advanced circuitry, so yes, will not theoretically discharge back to the panels. I've initiated a technical consult. What I expect is that the solar panel is insufficient to the task, that the thresholds are too low. I went with a smallish, light panel that is only 26" wide, so it pulls nicely behind a bike. Alt-E and Genasun both know what I'm attempting, but its still a bit of a gamble. I also suspect that its the solar charger itself that drained the one cell, that I've had to replace. I'll know more after next week about whether my application will work or not.

 

[winkinatcha]

Cool man...
On the few projects that I've done with small scale solar, I always put a diode in between the panel and whatever is downline to stop discharge back through the panel... Whether this is technically correct or even applicable in your case I don't know.

Joe

 

[arkmundi]

A123 AMP20 cell diagnostics
The dialog is part of my saga - was a great deal more involved than I presumed - and very useful. Sometimes a guy stumbles upon a gem of useful insight. Here's the synopsis:

• I now have a near 50% failure rate on my A123 AMP20 12S pack and that's a bit troubling
• wb9k shows up on the forum, a guy who works for A123 and has a great deal of insight into these cells and how to construct good battery packs from them
• provided a good opportunity to tap the expert on why such a high failure rate
• we'll never know for sure, but most probably a combination of "grey market cells" and not quite succeeding at the human BMS thing - monitoring, charging and discharging the cells within their range of tolerance
• a hard recommendation to do balance charging, forcing an evaluation of equipment, purchase and setup
• bought a Thunder 1220 balance charger and a T350 power supply from Hobbypartz.com to do the job right
• meaning putting in a set of balance leads to each cell
• thereby also allowing installation of my 2-Celllogs 8, which I'd had lying around
• which allowed active monitoring of each of the 12 cells in my battery pack as it was being bulk charged by my 6 amp Smart Charger from Batteryspace
• showing that one cell in the pack was spiking high when being charged, >3.81V
• confirming wb9k's suspicion: that due to variable cell internal resistance, its possible to overcharge some cells in the pack, which will eventually lead to cell failure
• meaning it'd be possible to simply set the Celllog alarms to sound on "High Voltage"; the settings allow for a High (3.62V), Low (2.50V) and Difference (0.5V) ; the delta is between the highest and lowest cells in the pack (really 6 cell spanned by 2 Celllogs)
• and pull the plug on the charger early, before it would ordinarily shut itself off (around 42V)
• thereby preventing the MOST LIKELY scenario for cell failure in my setup

So I just did that after today's ride and it worked like a charm! Means no cell will be charged higher than what the cells can handle. So that's how I'll be charging most of the time. And if I can get my Thunder 1220 working, will also do that periodically, though at this time, I do not believe my pack is out of balance.

Its the variable IR between the cells that's the controlling factor during charge/discharge. I did the grey market purchase (Victpower), so got what I got. A better "matched" battery pack would do a charge/discharge/charge test, under controlled conditions, with the right equipment, to accurately measure IR and then match cells accordingly. I'm not there, nor likely will ever be.

 

[wb9k]

Arkmundi,

I'm very happy to have been of help. Kudos to you and so many others here for your persistence! Hopefully the more information you have, the less painful your projects will become.

 

[999zip999]

Ark you got the 15.50 usd cells with short tabs that had been cut out of a working battery. Right ?

 

[miro13car]

I am really surprised by his failure rate,
I also bought from Victpower but new full tab cells, QC rejected, I am sure but new.
Also been using in 12S configuration with no BMS , just 17A BMS battery charger and Battery doctors.
i SIMPLY connect charger /with voltage set up at 42.2V by blue pot on the charger board/ , connect battery doctors , press 3.60V discharge on them and observe cells voltages while charging,
sometimes I would get 3.70V at most and quickly turned charger off. My rate failure is zero.
now THE MOST INTERESTING:
at the moment I turn charger off cell voltages varies wildly from 3.40 something to 3.60 something
, I do not do any balancing at all, I just start to ride and 2-3km into ride I check cell voltages and VIOLA - ALL cells reads 3.32V - 3.33V exactely at the worst, but most of the time they read 3.33V exactely ALL of them. All 12S cells power EPLUS ebike drive.

 

[999zip999]

I belive if charge to 3.45v is a about as full as they like but can be charge to 3.8v with not a problem but that's Zip guess.

 

[arkmundi]

I am really surprised by his failure rate,
I also bought from Victpower but new full tab cells, QC rejected, I am sure but new.
Also been using in 12S configuration with no BMS , just 17A BMS battery charger and Battery doctors.
i SIMPLY connect charger /with voltage set up at 42.2V by blue pot on the charger board/ , connect battery doctors , press 3.60V discharge on them and observe cells voltages while charging,
sometimes I would get 3.70V at most and quickly turned charger off. My rate failure is zero.
now THE MOST INTERESTING:
at the moment I turn charger off cell voltages varies wildly from 3.40 something to 3.60 something
, I do not do any balancing at all, I just start to ride and 2-3km into ride I check cell voltages and VIOLA - ALL cells reads 3.32V - 3.33V exactely at the worst, but most of the time they read 3.33V exactely ALL of them. All 12S cells power EPLUS ebike drive.

Yes, that's what I'm doing now. And that was my mistake previously, not doing that. I'd monitor voltage after a ride, bulk charge, and monitor voltage after the charger stopped - all appeared OK. But missing during the charge, this spike up into the danger range. wb9k suggested that over time this can lead to cell failure. As I continue to monitor with Celllogs, I notice that it is the SAME cell that spkes up, so one cell that has the <correction> highest resistance, so spikes. That suggests my experience that only one cell would fail at a time.

And yes, my grey market cells from Victpower were the half-tab, cut out of battery pack. They were apparently for a while selling "new, full-tab", but when I bought them, they only had the half-tab cells. Then they must of hit the bottom of the pile.

 

[wb9k]

I am really surprised by his failure rate,
I also bought from Victpower but new full tab cells, QC rejected, I am sure but new.
Also been using in 12S configuration with no BMS , just 17A BMS battery charger and Battery doctors.
i SIMPLY connect charger /with voltage set up at 42.2V by blue pot on the charger board/ , connect battery doctors , press 3.60V discharge on them and observe cells voltages while charging,
sometimes I would get 3.70V at most and quickly turned charger off. My rate failure is zero.
now THE MOST INTERESTING:
at the moment I turn charger off cell voltages varies wildly from 3.40 something to 3.60 something
, I do not do any balancing at all, I just start to ride and 2-3km into ride I check cell voltages and VIOLA - ALL cells reads 3.32V - 3.33V exactely at the worst, but most of the time they read 3.33V exactely ALL of them. All 12S cells power EPLUS ebike drive.

Yes, that's what I'm doing now. And that was my mistake previously, not doing that. I'd monitor voltage after a ride, bulk charge, and monitor voltage after the charger stopped - all appeared OK. But missing during the charge, this spike up into the danger range. wb9k suggested that over time this can lead to cell failure. As I continue to monitor with Celllogs, I notice that it is the SAME cell that spkes up, so one cell that has the least resistance, so spikes. That suggests my experience that only one cell would fail at a time.

And yes, my grey market cells from Victpower were the half-tab, cut out of battery pack. They were apparently for a while selling "new, full-tab", but when I bought them, they only had the half-tab cells. Then they must of hit the bottom of the pile.

Actually, the cell that hits HVC first has higher internal resistance, not lower. Probably also has lower capacity--they tend to go together. Extended charge times above 3.6 Volts cause Li plating in the cell, which directly causes permanent impedance rise and capacity loss. If your cell comes to rest above 3.60 you are overcharged, and Li continues to plate in the cell until the Voltage is pulled back below 3.60.

 

[arkmundi]

Actually, the cell that hits HVC first has higher internal resistance, not lower. Probably also has lower capacity--they tend to go together. Extended charge times above 3.6 Volts cause Li plating in the cell, which directly causes permanent impedance rise and capacity loss. If your cell comes to rest above 3.60 you are overcharged, and Li continues to plate in the cell until the Voltage is pulled back below 3.60.

Thanks for the correction. So now, with a 3.62V high voltage alarm set on my Celllogs, when pulling the plug on the charger, it immediately comes to rest in the 3.50 to 3.56V range. I'm not using the Thunder 1220 right now because I sent it back to HobbyPartz for testing - they think its the PSU. Apparently **ERROR**car batt. empty can be triggered by too high PSU voltage too and that's what the tech suspects.

 

[wb9k]

Actually, the cell that hits HVC first has higher internal resistance, not lower. Probably also has lower capacity--they tend to go together. Extended charge times above 3.6 Volts cause Li plating in the cell, which directly causes permanent impedance rise and capacity loss. If your cell comes to rest above 3.60 you are overcharged, and Li continues to plate in the cell until the Voltage is pulled back below 3.60.

Thanks for the correction. So now, with a 3.62V high voltage alarm set on my Celllogs, when pulling the plug on the charger, it immediately comes to rest in the 3.50 to 3.56V range. I'm not using the Thunder 1220 right now because I sent it back to HobbyPartz for testing - they think its the PSU. Apparently **ERROR**car batt. empty can be triggered by too high PSU voltage too and that's what the tech suspects.

Sounds like you've got a good charging routine worked out now. Good luck with the Thunder......

 

[999zip999]

I didn't mean to charge to 3.8v. Just it would not kill it. I balance charge to 3.59v.

P.s. I had to clean up that sentence.

 

[ejonesss]

are these ok for charging these cells?

https://p10.secure.hostingprod.com/@www.voltphreaks.com/ssl/catalog/product_info.php?cPath=3&products_id=60

i am using them to charge the lifebatt/psi 40138 cells

 

[arkmundi]

Voltphreaks?

are these ok for charging these cells?

https://p10.secure.hostingprod.com/@www.voltphreaks.com/ssl/catalog/product_info.php?cPath=3&products_id=60

i am using them to charge the lifebatt/psi 40138 cells

I got one as a trial, tried and discarded as a grade of "cheap chinese chargers" to be avoided at all costs. Invest in quality LiFePO4 cells AND a quality charger! Doing cheap doesn't really work.

 

[ejonesss]

you never heard of Voltphreaks? they have been around for a while and i am using 16 of their chargers wich was recommended by other users on the board back in 2008 to 2010 range

Voltphreaks?

are these ok for charging these cells?

https://p10.secure.hostingprod.com/@www.voltphreaks.com/ssl/catalog/product_info.php?cPath=3&products_id=60

i am using them to charge the lifebatt/psi 40138 cells

I got one as a trial, tried and discarded as a grade of "cheap chinese chargers" to be avoided at all costs. Invest in quality LiFePO4 cells AND a quality charger! Doing cheap doesn't really work.