Just a breif update.

 

I have just passed the 250+ discharge point of these cells having used them for the last 13 months or so.

 

To date they have performed faultlessly in my application, retaining both charge and cells remaining balanced to within 10-20mv of each other (no BMS fitted).

 

Specs state that they will give 1000+ discharge cycles, which in my application would last me 4 years. The pack cost me about £70 to build + £50 for the chargers, though I have only used the Turnigy charger/balancer once when I first constructed the packs.

 

I agree my application is less common than many i.e. a daily 10 mile round commute on pretty flat terrain, but carrying two of these 12s1p packs may provide others more flexability. It seems the solution represents a good value for money option.

 

Maybe I won't be saying this in 3 years time :o

 

 

Regards

 

Jerry

Edited January 20, 201115 yr by jerrysimon

Thanks for the update Jerry Your set up does seem to be very good value and a realistic option.

 

John

There is an interesting article in that magazine being linked to in another thread page 46.

 

ExtraEnergy Magazine Issue 2 (english)

 

By chance, I am using my battery in a very simlar way to which they recommend.

 

I usually charge twice a day once at home and again i.e. before each journey either way. My battery is therefore never fully discharged, I am guessing about 1/2 to 2/3 before it is then recharged.

 

I am wondering if this also effects the balance of cells if no BMS is used

 

Regards

 

Jerry

It's good to hear your battery is holding up well. In particular as I use mine in almost exactly the same way!

What's better than my DIY A123 12s1p (2 *6s1p) pack ?

 

Two of them

 

http://farm6.static.flickr.com/5176/5425309652_593a5e1848_z.jpg

 

This turned up the other day (there is another one in the box) from my previous supplier. The only difference this time, is I got them to spot weld them up into two 6s1p in my previous flat parallel side by side config.

 

I have enough 6s pigtail balance taps and connetors left over from the last build I did over a year ago.

 

Not only will this provide me twice the range for those longer rides, but also keeping the same config profile of the 6s1p packs means I can swapped out between each of the single packs if one fails.

 

Regards

 

Jerry

Edited February 7, 201115 yr by jerrysimon

Nice !

 

Mhmm, green battery cells...

 

http://www.starstore.com/acatalog/retro-hulk-green-stat.jpg

 

Controller voltage ratings

 

I am really bad at these threads so tell me if i am doing it wrong.

 

as i am a beginner i have many questions but be patient.

 

Controllers, in particular for a 5year old Sprint initially NHMI. I want to build batteries for it but do not know the max voltage it is safe to use with this controller. Or the drop out voltage but this is less important.

 

What do they mean by "reboot", is it sw off and on again?

 

So much to learn, so little time.

 

Malcolm

Kinda of a double post (but you can't seem to edit old posts in this new forum software ?) from another project I did building an Ebike for my daughter with M.E. (CFS), but worth adding to this thread for completeness. This provides a more robust solution for the battery both in terms of a connector, isolating switch and enclosing the battery pack in a tupperwear container.

 

Here are some final pics of the battery and how I installed it inside a tupperwear box with a seperate switch and connector (Speakon 2 pole rated to 40amps) available form Maplin here.

 

http://farm4.static.flickr.com/3663/5800183637_087a6fa5c1_z.jpg

 

http://farm3.static.flickr.com/2302/5800183991_fbf1ab168a_z.jpg

 

http://farm3.static.flickr.com/2366/5800184337_cd00b50a45_z.jpg

 

Finally I had to make a seperate charger lead to enable it to be charged from my chargers with Deans connectors fitted.

 

http://farm3.static.flickr.com/2131/5800737994_f222341a58_z.jpg

 

Regards

 

Jerry

Edited June 5, 201114 yr by jerrysimon

Well after 22 months, 2500 miles and approx 500 charge cycles, one of my cells seems to have died

 

Interestingly the battery still worked ok on my 10 mile round commute but I had noticed a drop in power overall and sometimes for no reason it seemed to slow right down. Clearly there was a reason. I guess the low voltage cutout did not kick in because I have 12 cells ?

 

Over the last week I had noticed that one of the cells voltages had been dropping. I test occasionally using the excellent little CellLog meter and here it shows the complete failure error. It was easy to identify which of the two 6s1p packs had failed and being a DIY pack, was just a case of then stripping one down to identify the suspect cell.

 

http://farm7.static.flickr.com/6176/6222725331_eb6265781c_b.jpg

 

Measuring 0.51 volts instead of the usual 3.3 volts!

 

http://farm7.static.flickr.com/6227/6223244092_781b810305_b.jpg

 

 

Cell removed and taps protected from shorts.

 

http://farm7.static.flickr.com/6173/6223244210_ac01767ac3_b.jpg

 

 

Regards

 

Jerry

Edited October 8, 201114 yr by jerrysimon

Ok battery pack rebuilt with a spare cell I had and hooked up for inital balancing.

 

http://farm7.static.flickr.com/6175/6222725689_9d688016de_b.jpg

 

I was told these were genuine cells but I noticed they seem to be double wrapped

 

I had hoped to get at least 1000 charge cycles and probably more. Anyway its good that they are DIY packs and thus I know how to dismantle and repair them. I had purchased a few spare cells when I first built them so I can replace any faulty ones as and when. I guess for the cost (about £40/6s1p pack) nearly two years use, still represents good value for money and its not as if the whole pack is wasted.

 

Will be interesting to see if another cell fails. I will keep you all posted.

 

PS I just went out for a test run and noticed a big difference in power

 

I guess as the failure was gradual I had not really noticed the drop in power.

 

Regards

 

Jerry

Edited October 8, 201114 yr by jerrysimon

I need your expert hands and tools to fix my pack!

(no sexual jokes please )

 

Seriously, one of my A123 cells died and I need to either (1) reactivate it by applying a high voltage for a short moment or (2) replace it. Either way, I am gutted because this type of repair is outside of my comfort zone (soldering plates on live high-discharge batteries). My charger/balancer also failed, I am not sure yet whether the Turnigy Accucel-6 is damaged, or if it is juste the main 12V power supply. And...my controller also seems to be kaput (I think it is the source of the original system breakdown...domino failure it seems). I need to get my hands dirty and find out what is going on!

 

http://www.pedelecs.co.uk/forum/electric-bicycles/6956-diy-stage-9-a123-nano-battery-pack-photos.html

Sorry to hear that Dan.

 

I rely on my bike every day, so glad I got it fixed. I do have my daughters pack now as well to fall back on if necessary.

 

Regards

 

Jerry

Damn looks like another cell has gone. Got to work ok, but lost some power towards the end of the ride and getting the same error on the CellLog.

 

Its the same 6s1p pack. Will be interesting to see which cell it is.

 

Regards

 

Jerry

Its a good job you have those extra cells knocking about. It sounds like its becoming a bit of an issue.

Still least your handy and rebuilding the cell packs.

 

Its something I looked at when I was opening up my old 36v battery but in the end there's just to many cells to contend with in the cheaper packs all at about 2ah each. Just amkes for loads of connections and getting at one cell is a nightmare.

 

Least your pack is managable. anything with 40+ cells is such a pain.

Yep it should not be too difficult to fix. Its charging now. The CellLog is not reading any errors and all the cells are at 3.38 with one at 3.35 so not sure what is going on.

 

Its the same 6s1p pack as before so ordering another one of those with welding tabs already fitted and connected up is pretty cheap. I still have two more spare single cells though

 

I do actually have another full 2*6s1p pack, buy my daughter is using that on her leccy bike a lot now so daren't take it.

 

I am pretty happy with almost two years use and my 4-500 charge cycles. Specs say these cells should be good for about 1000 charge cycles though.

 

One other thing, one of the cells in the suspect pack was definately slightly warm when I got to work this morning

 

Regards

 

Jerry

Edited October 10, 201114 yr by jerrysimon

It might be interesting to peel the wrapper off one of your dead cells to see if you get any clues as to whether it is a genuine A123 or not. I think I bought mine from the same supplier as you. They're all still fine though I've not used them in anger for several months. They did seem a bit too cheap to be genuine...

Are you using two packs together or just the one?

I wouldnt expect as many life cycles if your making the cells push 4c or 3c. Least with a larger pack your not stressing the cells out so much. Which would show up the weak ones pretty quickly.

 

Maybe one of the connections isn't quite there or the repair?

Yes Pedalo I just read that the genuine ones will have A123 Systems stamped on the metal casing. I will check tonight.

 

I think they are genuine. You can get even cheaper ones that are marked as DeWalt rejects.

 

I have just recharged the pack and all seems ok. I will attach the CellLog and put it in logging mode for when I cycle home, as this will then show me what is happening throughout the ride.

 

Regards

 

Jerry

I use two 6s1p packs connected together in series. I am pulling no more than 10 amps in any one burst and mostly only 6 amps. These cells are rated to something like continuous discharge of 30C, 69 amps (60C, 138 amp bursts!) so I am well within specs.

 

The connections are fine. I suspect a second cell is dying. I will check tonight.

 

As I said for about £40 for each 6s1p pack, a couple cells in one pack failing after 4-500 charge cycles, 22 months and nearly 2500 miles means I don't feel too cheated

 

 

Regards

 

Jerry

Edited October 10, 201114 yr by jerrysimon

Ok battery seemed to perform ok on the way home and cells were failry balanced (within 100mV) at the end with no errors

 

Attached is the result from the CellLog displayed using the program LogView. Note the CellLog meter is attached to only one of the two 6s1p packs i.e. the one with the suspect cell.

 

The ride time is showed on the scale along the bottom i.e. 26m40s. The overall drop in voltage of the whole pack (big blue wavy line, scaled on the left) is shown for the whole ride. The individual six cell voltages are the ones at the top, scaled on the right. Five of the cells are pretty much aligned apart from cell three (green line) which is about 0.1 volt down on the others. I am pretty sure this is the same cell that I swapped out, though can't confirm unless I take the pack apart again.

 

I am going to run it all again tomorrow to see what happens. The new cell might just take a few charges to sync in with the others ?

 

Ps It appears that these are genuine A123 cells, certainly from checking on line and taking off the green outer wrapper of the failed cell to check.

 

Regards

 

Jerry

Edited October 10, 201114 yr by jerrysimon

New cell will probably need a few cycles to ensure it gets to full capacity and discharge levels.

So your guess of it settling in sounds about right

Well the same thing happened again this morning on the way to work. I definately put more load on the pack on way to work (it was very windy again) than on the way home.

 

This time I caught it on the CellLog as shown below viewed in LogView. Again the blue line is the overall pack voltage and the pink line is cell three starting off low and dropping in voltage till eventually it dies completely.

 

I took the pack apart and it is the new replaced cell that has failed

 

I wonder if I have just used a duff cell by chance. I have another couple of spares so will fit one of those. Not sure if to try a few more cycles first. Strangely it does recover when I recharge it. I must admit to being a little confused about the whole thing. I would not have thought a new cell would struggle in an older pack.

 

Regards

 

Jerry

Edited October 11, 201114 yr by jerrysimon

You have to take them under load though unfortuantly. Its clearly not up to the job.

Keep on it it may get better with a bit more cycles under it belt. But looking at that graph its not looking good.

Thanks Scott. I was chatting with one of the electrical engineers at work. He liked my graphs. He has suggested charging the single cell extra on its own to make sure it is fully charged before I put any load on it. I think one of the problems is that I may have put the cell into the pack in an unmatched charge state.

 

As you can see even when the pack is fully charged its still the lowest cell, voltage wise.

 

He also said when it dies the other cells effectively push charge back through it the other way, causing it to warm slightly and probably making things worse.

 

He said the battery pack has held up remarkably well and I have more than got my monies worth. Anything extra is just a bonus

 

Regards

 

Jerry

Edited October 11, 201114 yr by jerrysimon

Thats eactly correct. The other cells will try compensate and put chage back into the cell to get it up to the same voltage. Hence if cells or packs are not withing a few 100mah the current flow causes the weaker cell alot of stress. Making things even worse.

 

I would have throught your changing process and balance charge would have brought the cell back in line?

 

Or do you not have a balance charger?

 

 

Might be a long process but once its done hopefully the cell should perform.