"In vitro" test and break in proceurof repaired Ping battery

[liared]

I have just replaced a cell group and a v 2,5 BMS in a Ping 36V 20ah battery. The battery is still "opened up" so I have access to measurement of Volts et cetera directly on the battery.
Before I reseal the battery with new duct tape it would be nice to get the battery "in balance" - same Volt reading on all cell groups, all lights on the BMS shining red after charge et cetera.
I figure an "in vitro" setup simulating a real e-bike break in period use could be made before i seal the battery and remount it on the bike.
I have read that a simulated situation can be done by putting "load" on the battery using an electric hair dryer, light bulbs et cetera.
Problem is that I am an electric "dummie" so I want to ask expert people before I do something potentially stupid.
Suppose i attach an ordinary household hairdryer to the battery (rated European 230 Volt AC, 1200 Watt).
Will this simulate e bike use? Or will it demand too much current running from the battery (damaging it).
What do you suggest I use (preferably things i find in my household) in order to "break in" my battery "in vitro"?

 

[dogman dan]

Actually you just need to "break in" the new cells. So you could hook a 12v light bulb like a headlight or turn signal to just the new cells, then recharge it manually with a cell phone charger. Give it a few shallow cycles to wake up the lithium, then use the phone charger to try to get it close to the same as the other cells. ( or bring down the others with the light) Then put it on the ping charger.

Or you could just add two wires to the cell group that's new. Then charge it, and if needed, add a bit more to that group till the light goes on with the 4v charger. Then go for a short ride. Repeat, etc, till the battery is lighting up properly at the end of charge.

If I was building a battery, I'd want some extra balance plugs like lipos have. That way you could put an external balancer on it. You might consider that, since you have the hood up.

 

[liared]

Thanks for your advice Dogman,
I have however already attached/soldered in the new replacement cell group into my 36V 20Ah Ping battery.
Maybe the new ver. 2.5 BMS will do the balancing/break in job for me.
The original problem was that one cell group went bad (too low Voltage) causing the BMS to "shut down" the battery.
The battery was under warranty so Ping sent me new pouches and BMS (great support from Mr. Ping !!!). Ping wrote that a possible cause of the problem could be a BMS malfunction or a connection problem because of very thin balance wires that I had used to extend the original balance wires.
I found that replacing a cell group was not as difficult as I had thought.
The new cell group is currently 3.3 Volts whereas the other groups are 3.6 Volts.

]

 

[dogman dan]

Got a voltmeter then I suppose? The same places you touched the leads to measure that cell is where to attach a small 4 v charger, like a cell phone charger.

Carefully monitoring it, you can bring up the cell group, or discharge just that cell group with a light bulb to give it some light cycles.

Even though you are all soldered in in series, you can still charge or discharge any cell group by tapping in at the right spot.

Sould be easy to solder in two more wires, or just use the balance leads you have now to tie in a charger or bulb. Chances are, you can attach with a couple alligator clips pretty easy too. In the pic, it looks to me like the red and the black wires would be + and - of that new cell.

 

[liared]

Dogman,
I just got mail from Ping - it seems that You and Mr. Ping are "twin souls" in this matter - I have good reason to trust both of You !
Bengt

Hi Bengt,

1, You don’t need to remove the new cell group from the pack. You can charge the cell group just on the 6 and 7 solder blocks, or the sense wires if you have wrapped the pack. You can even charge them when the BMS is connected. So, as soon as it’s balanced, you can see the LED for the new cell group lights.

3, Yes, it will be achieved, but it will take really long time since the new cell group could be only 50% charged now, while the old cells have been fully charged.

I recommend you just charge the cell group through the 6 and 7 solder blocks.

Best regards,

Ping



From: Bengt Josefsson [mailto:bengt.josefsson@dobytec.se]
Sent: Saturday, October 30, 2010 2:21 AM
To: pingping227@hotmail.com
Subject: SV: Replacement BMS arrived

Regarding: ”You can manually balance them”
Ok Ping,
If I go for manually charging the cells/cell group as told by You:
1. Can that be done when the new cells/cell group is/are already soldered back onto the whole battery pack as it presently is -
(putting/soldering temporary charge wires to point 6 and 7 on the picture below)?

Or will I have to remove the new cell group from the pack before charging individually?

2. If I have to remove the new cell group from the pack for individual charging – is recommended to charge the cells in the cell group collectively or is it better if I also separate the cells charging the 4 cells individually?

3.If I go for trying to let the BMS get the cells in balance can I be sure that is achieved (although it might take some time)?
Or
May that result in the cell groups never come to proper balance causing the battery cut of prematurely giving me shorter electric assist range for my e-bike).
What do you recommend me to do?

(Constantly learning more about my battery)

Best greetings from
Bengt

 

[dnmun]

not sure i follow that, but to use a single cell charger you just clip the alligator clips from the single cell charger on each end of the pouches and then it will only charge that one cell up to the 3.6V of the others. you can use the 5V cell phone charger if you watch like a hawk and shut it off before it goes over 3.5V and let the BMS and charger finish balancing it. the voltage will climb straight up when it is charged so you really have to watch it second by second while on the cell phone charger. make sure to get the polarity right.

 

[liared]

if you watch like a hawk and shut it off before it goes over 3.5V and let the BMS and charger finish balancing it. the voltage will climb straight up when it is charged so you really have to watch it second by second while on the cell phone charger. make sure to get the polarity right.

"Watch like a hawk" sounds like a difficult/risky procedure.
I have had the cell phone charger attached to the low cell group now for almost an hour and the Volt reading has only climbed marginally (from 3.0 to 3.4).
If this is a typical constant charge rate I will have to wait for hours before I get close to 3.5 Volts.
Suppose I fail to stop charging in the right moment getting the cell group overcharged for 5 minutes. Would that permanently damage/spoil the cell group?
Anyone experienced the effect of a short overcharge time?
Maybe I should consider getting a single cell charger!?
I found this one on E-bay:
http://cgi.ebay.com/Charger-for-single-LiFePO4-TS-SE-cell-3-2V-3-65V-10A_W0QQitemZ120533675315QQcategoryZ48618QQcmdZViewItemQQ_trksidZp3286.m7QQ_trkparmsZalgo%3DLVI%26itu%3DUCI%26otn%3D3%26po%3DLVI%26ps%3D63%26clkid%3D4593762903954004526

Would this single cell charger be suitable in my situation?

 

[liared]

I have had the cell phone charger attached to the low cell group now for almost an hour and the Volt reading has only climbed marginally (from 3.0 to 3.4).

Sorry, what i wrote was wrong:
Should be "I have had the cell phone charger attached to the low cell group now for almost an hour and the Volt reading has only climbed marginally (from 3.30 to 3.34).

 

[dogman dan]

It'll take a few hours to charge if it's that low to start with. But it will also take a lot of time for the ping bms to bleed down the others too.

So you could try bringing down the other cells too, so you end up with a battery that is partialy charged but sort of balanced. Then put it on the ping charger.

Again, cycling the new pouch several times would help get it charging to the same level as the others. So you don't have to take the new cell all the way to the top to cycle it. Just get it nearly full charged, put the light bulb on it and discharge it just a little, and then charge some more.

It's true, the voltage of the cell will seem to sit there for a long long time, and when finally charged, it will shoot up fast. So you will have to be sure to look at it often, and catch that voltage rise before it's too high. Not fun, but worth it to save having to replace cells again.

A small charger that actually shuts itself off would be great, but that one looks like it would charge too fast to me.

 

[liared]

Just get it nearly full charged, put the light bulb on it and discharge it just a little

Thanks Dogman,
I am by and by getting the "picture" clear thanks to all the generous advice I get here (nice place!!). The new cell group is in this moment under charge with a cell phone charger. I see the voltage slowly rise - now 3.36 Volts - gone from 3.30 to 3.36 in almost 2 hours. I will try to cycle the new cell group a few times as you suggest. Just a question (I am not very good at "electrics"). If I use a light bulb for this- will it be Ok to use an ordinary household 230 Volt, 60 watt bulb (I am in Sweden/Europe) or should it be a 36 Volt bulb?
If I use an ordinary household bulb, I don’t expect it to shine when attached to a 36 Volt battery but the watt consumption will still be 60 watt??? - Thus not draining the cell group at too fast a speed??

 

[dnmun]

i had seen that charger on ebay and lost the link. thought it was a deal myself. i have used the voltfreaks single cell charger and have now ruined 2 of them and was thinking i wanted to buy that 10A single cell charger for the thunderskys. not only is it faster but i figured it would have the output protected better than the voltfreaks charger.

the terminal voltage does not change linearly with charge accumulation like with a chemical cell. this is lithium ion storage and when the cathode lattice has filled with ions and the new ones have no place to go then they make a mess. when this happens then the voltage changes from about 3.7V to 4V with only about 200mA in a few seconds. 4 volts is really too much for the lifepo4 cells, even if they don't pop and burn.

 

[999zip999]

Ping has a small single cell charger for 7usd. 3.88v

 

[liveforphysics]

I have had the cell phone charger attached to the low cell group now for almost an hour and the Volt reading has only climbed marginally (from 3.0 to 3.4).

Sorry, what i wrote was wrong:
Should be "I have had the cell phone charger attached to the low cell group now for almost an hour and the Volt reading has only climbed marginally (from 3.30 to 3.34).

It's doing fine then. Leave it be, and it will finish.

Going from 3.3-3.4 with LiFePO4 will take the bulk of the time. Going from 3.4-3.7 will go very quickly.

 

[dnmun]

if you have one low cell group that you just replaced you could pull the rest of the battery down to that level too, before you charged it.

i plug my load heaters into an extension cord with anderson connectors soldered to the male legs of the extension cord so i can plug it into the output of my turnigy watt meter i use..

use a jumper with alligator clips on one end to deans female connector to match the input of my watt meter. clip the legs across the battery terminals up to the point of the new pouch and discharge it down to the same voltage, do the same for the section of the battery above. then all is close at the bottom and should charge up together.

 

[webfootguy]

Ping has a small single cell charger for 7usd. 3.88v

Link?

 

[999zip999]

Webfootguy, www.pingping227@hotmail.com - Liping@signalab.net or pingping227. That's my computer skills. Yea I sould have got 2. A little green light red when charging 7usd perfect. Ping has a lot of things if you know what to ask. I guess to much to list. Buy a ping and join the ping family like Li Dogman ect.

 

[liared]

Case report on my cell group replacement story - mail just sent to Li PIng !
-----------------------------------
Hi again Ping,
Good news so far!!!!
After ”massaging” the battery “in vitro” about 10 times/cycles by using a cell phone charger to gradually build up voltage in the new cell group combined by draining the battery now and then with car light bulbs acting as load and followed by full charging cycles with my ordinary Ping charger:
VOILA!
All 12 leds are now glowing beautifully red on the BMS.
I was almost giving up – thinking something was wrong with my setup/procedure but perseverance and sticking to your advice finally seems to have paid off!
I will now seal my reconditioned battery temporary and make a test run on my e-bike hoping it will give me about the same range as before the cutout incident.
I am thinking of attaching/soldering in extra measure/charging wires from each cell group spot that will end up outside the battery –That way I figure I can easily check voltages in the battery (without cutting off the BMS plastic cover) and also inject an extra individual charge if a cell group goes low in the future. Do you think that is a good idea?
Sincerely
Bengt
-------------------------

 

[liared]

After "balancing/tuning in" the replaced cell group using a cell phone charger following advice from Ping and from members on this forum I also attached/soldered extra measure wires from each of the 12 measure points at the top of the opened up battery.
These 12 wires end up outside the battery (well shielded and covered at the outside end) . This way I can measure Volts for each cell group without taking off the plastic cover on the BMS.
These extra wires also let me charge an individual cell group if that will be needed in the future.
The split 36 V 20ah Ping is now back on my E-bike having regained its previous power.
Considering that I had never before seen the inside of a Ping e-bike battery and that I am/was a non-educated person when it comes to electric matters:
Help from this forum and Mr. Pings excellent support were the crucial factors that made possible what I feared was too advanced for me!
Thanks for your advice!

 

[999zip999]

Liared, Good job I sould have listen to Dogman and left my old send wires connected for balance and single cell charging. So how hard will it be to take it apart again. again ? Is your new cell a little off on the voltmeter ? Little higher then a little lower on the charger before the does it's balance thing ? Mine end up at 3.58v 3.59v.

 

[liared]

Is your new cell a little off on the voltmeter ? Little higher then a little lower on the charger before the does it's balance thing ? Mine end up at 3.58v 3.59v.

After a full charge and disconnected charger and after the BMS has turned off all the 12 "full charge" red LED lights all my cell groups (including the new replacement one) show an identical voltage of 3.55.