Generic OEM - Unicycle-A2

[John Eucist]

While we're posting videos with a bang.  This one is kind of funny. 

 

[esaj]

While the videos of exploding and combusting batteries are funny (when they do it on purpose), I still wonder what makes people try that?  How many limbs and eyes have been lost due to trying something like penetrating a battery or hitting it with a hammer... kind of reminds me of the guy who died trying to cut open a hand grenade with a circular saw:

This story was told at a symposium dinner, by two Austrian pathologists who work together in Germany. A deceased male was brought to them for a post mortem. He had suffered severe head trauma. According to police reports, the man wanted to see how a German World War II hand grenade was constructed. His curiosity led him to clamp the grenade in a vise, and cut a thin band around the center with a circular saw, so that he would be able to crack open the two halves. Unfortunately, the man cut a little too deep, and detonated the grenade. The pathologists stated that the man had very little brain material when he was brought to them; however, they were not sure if that was a result of the explosion!

[hobby16]

 

now I have to prepare Barbeque for quests, but I have my soldering iron near the barbequeu, so I might shunt while cooking

 

Ohh, by the way, the only charger I have is the one that came with unicycle..

Hope your bbq iron is not like this one : http://www.freeze.xtrweb.com/images/1-freeze-branding.jpg Not exactly the right model for precision work.

As to the "Charge Doctor", it's not a charger, just a gadget to monitor the charge. Look it up in this forum, there is a guy selling it. Trusty seller, I recommend you

[cg]

Hope your bbq iron is not like this one : http://www.freeze.xtrweb.com/images/1-freeze-branding.jpg Not exactly the right model for precision work.

As to the "Charge Doctor", it's not a charger, just a gadget to monitor the charge. Look it up in this forum, there is a guy selling it. Trusty seller, I recommend you

Not exactly, it's a 25W Weller, and it was impossible to use the existing soldering blobs, so weak.

 

But, now my wheel is shunted :), at it doesn't throw me off even thou I only have 15 working cells.

but it is impressive how much it is lacking power, I guess I should not ride it before I get the cell replaced.

[hobby16]

But, now my wheel is shunted :), at it doesn't throw me off even thou I only have 15 working cells.

but it is impressive how much it is lacking power, I guess I should not ride it before I get the cell replaced.

If you remove the defective cell and temporarily replace it by a wire, I think you'll have enough power to ride. But how the BMS would like such a "trick", especially when it must ensure balancing or overcharge protection, is another story. 

As to the soldering job , sorry, but I'll give you a F (like "fail" ) or more generously a B (like "because of the bbq iron m'am"). To avoid a "dry blob", the soldering point must melt enterily before applying fresh solder, so keep the iron on it as long as necessary (probably several minutes with your Weller). Don't be afraid to overheat (underheat & dry blob is a very common error for laymen).

[cg]

As to the soldering job , sorry, but I'll give you a F (like "fail" ) or more generously a B (like "because of the bbq iron m'am"). To avoid a "dry blob", the soldering point must melt enterily before applying fresh solder, so keep the iron on it as long as necessary (probably several minutes with your Weller). Don't be afraid to overheat (underheat & dry blob is a very common error for laymen).

Lol, I wasn't to impresses myself either when I looked at it today, I was hoping the angle of the picture was hiding the poor work.

[cg]

I have now ordered two of those Sony US18650V3 with Z-solder tags... can't wait to try them (not going to try replacing the dead cell by wire as suggested :P)

[Jason McNeil]

Carrying out an operation of this kind is damned impressive stuff! I constantly amazed at how proficient many eWheelers are in electronics & general troubleshooting. 

[cg]

Carrying out an operation of this kind is damned impressive stuff! I constantly amazed at how proficient many eWheelers are in electronics & general troubleshooting. 

I just hope it will work, but when did 'changing batteries' become so hard?

[Jason McNeil]

In a battery pack, isolating the defective cell, shunting the BMS, & soldering (especially batteries) for most people is not a trivial task. 

[cg]

In a battery pack, isolating the defective cell, shunting the BMS, & soldering (especially batteries) for most people is not a trivial task. 

I agree, but that is due to a design choice. Wouldn't it be nice if the BMS simply had a container where you could insert and remove the required 18650 batteries ?

I know, the only goal for those packs are they should be cheap, but I would certainly like a wheel where I could change the cells with ease.

[dmethvin]

Every pressure-contact electrical joint is an opportunity for failure from vibration as you ride along on rough roads or wipe out. In my Fireweel the factory put a blob of hot glue on each board connector and ran a wire tie through the connector running to the motor hub. These batteries carry quite a bit of current so it's not quite the same as a couple of AA batteries in a remote control. When my remote stops working I whack it on the table to see if it's a bad connection. When your EUC batteries stop working it whacks you on the road.  

[hobby16]

I know, the only goal for those packs are they should be cheap, but I would certainly like a wheel where I could change the cells with ease.

A single cell failing is a rare occurrence, most of times, matched batteries age gracefully together, so I would prefer well soldered cells for more contact reliability (see dmethvin).

BTW, I've added your wheel to my archive list : http://hobby16e.neowp.fr/2015/07/19/a2-generic-bms-shunt/

The blog is brand new and still in construction.

[cg]

A single cell failing is a rare occurrence, most of times, matched batteries age gracefully together, so I would prefer well soldered cells for more contact reliability (see dmethvin).

I still think it should be possible to make a design where the contact is firm, just look at the plugs at your universal power supply (banana plugs)

 BTW, I've added your wheel to my archive list : http://hobby16e.neowp.fr/2015/07/19/a2-generic-bms-shunt/

The blog is brand new and still in construction.

Nice blog, when I have made a nicer soldering you should update the image

I got one stop closer to getting the battery out (@vee73 I know you told me to wait for the cell, I hope it doesn't ruin anything but I just could not hold myself back), the battery lock really sour:

I tried to get the battery out using one of those brackets that protects the slots in a PC, but that actually resulted in a small shorting giving some smoke for the battery, tomorrow I will try to get the battery out using dental-floss.

[esaj]

Hard to say from the picture, but it looks like it might have vented through the gasket seal? Internal short circuit?

 

[cg]

Hard to say from the picture, but it looks like it might have vented through the gasket seal? Internal short circuit?

I can confirm there was a lot of black goo... I think the battery died when I was going downhill with fairly empty battery, and at the end of the hill the slope changed to upwards. that was the first time the wheel cut-out.

[hobby16]

Hard to say from the picture, but it looks like it might have vented through the gasket seal? Internal short circuit?

On the 18650 cells, the + pole is very near to the - rim, they can touch each other easily, I have killed some cells like that when I was young and fooling around with laptop old battery packs.

cg made an (external) short when removing the spot welded tab.  Not something appreciated by the Lithium chemistry.

I hope the replacement new battery will be better treated

[cg]

On the 18650 cells, the + pole is very near to the - rim, they can touch each other easily, I have killed some cells like that when I was young and fooling around with laptop old battery packs.

cg made an (external) short when removing the spot welded tab.  Not something appreciated by the Lithium chemistry.

I hope the replacement new battery will be better treated

Hmm, is it in the same end of the same cell that there are both '+' and '-'?

The shorting was not during removal of the welded tab, the welded tab was removed with a small pliers.

The shorting was trying to get the battery released from the pack, I used the object between the printing board and the battery. Tomorrow I will try with dental-floss

[hobby16]

Nice blog, when I have made a nicer soldering you should update the image

Oh sure, I'll do. BTW, your images from the first page have disappeared (that's one of the reasons I've set up a blog, since I want to have a reliable repository for the data), so I still don't know if your A2 mainboard & batteries open from inside or outside. If you still have some images of the openings, can you please repost them, I'll add to my blog.

Hmm, is it in the same end of the same cell that there are both '+' and '-'?

Yes indeed.

Esaj's picture shows + and - are very close, that's a frequent source of short-circuit during manipulation & soldering.

[cg]

Oh sure, I'll do. BTW, your images from the first page have disappeared (that's one of the reasons I've set up a blog, since I want to have a reliable repository for the data), so I still don't know if your A2 mainboard & batteries open from inside or outside. If you still have some images of the openings, can you please repost them, I'll add to my blog.

Yes indeed.

Esaj's picture shows + and - are very close, that's a frequent source of short-circuit during manipulation & soldering.

I still have the images, I will have a look and edit the posts they are missing from.

regarding Esaj's picture, I don't see any '-' legend, can you tell me what color the '-' is?

[hobby16]

regarding Esaj's picture, I don't see any '-' legend, can you tell me what color the '-' is?

Red is + . Gray rim & casing is -. In esa's picture, + and - are close, but in a real cell, they can be still closer (less than 1 mm !).

[cg]

Red is + . Gray rim & casing is -. In esa's picture, + and - are close, but in a real cell, they can be still closer (less than 1 mm !).

That is good to know, and a bit horrifying,

anyway, I have re-added the missing pictures, but there is no picture of the battery compartment, only the controller compartment. I can make some better pictures when I have made some progress with the wheel, currently I left it at work.

[cg]

Success, I am driving my wheel again

One of my colleagues brought this cell from a salvaged laptop battery

I forgot to note-down what was written on it, but I looked it up while working, and it was some Sony gr18650 (2xxxmAh)

The voltage when I got the battery was around 3.2V, I charged it using the power supply in the picture, but since I don't really know what I am doing, I didn't dare charge it to much, I stopped when the battery was around 4.1V... In a minute dropped to 3.85V and the stayed stable.

To exchange the battery, I had to get a block of 8 batteries out since it has to be soldered on both sides, first I carefully noted the orientation.

The side that I took out was soldered to these points

The batteries was glued, so taking the bad battery out of the series leaved some scars on the 'good' batteries that I had healed using some tape

The battery pack with the replaced battery:

and, the battery pack, good as new

+ wheel

Before wrapping the battery, I charged the pack using the wheels charger, to my discomfort the new battery did not charge to 4.2V but around 3.9V (I think it was higher than what I had achieved with my manual charging, but thinking of it I am a bit in doubt),

I have been driving the wheel for some time today, I have 3 diodes turned on on the 4 diode charge indicator, so almost full battery, the wheel is handling OK, I am still a bit uncomfortable about going to fast since I now two times have experiences the cut-out from the BMS, (it didn't cut out, and it is still shunted)

 

I would not have done this without your advice.

 

edit:

by the way, what are your thoughts on the fact that the battery seems to have a lower voltage than 4.2?

[esaj]

Success, I am driving my wheel again

Congratulations!

The voltage when I got the battery was around 3.2V, I charged it using the power supply in the picture, but since I don't really know what I am doing, I didn't dare charge it to much, I stopped when the battery was around 4.1V... In a minute dropped to 3.85V and the stayed stable.

Around 4.2V +- 0.05V (4.15...4.25V) is usually the max voltage for most Li-Ion cells (but not LiFePo!). Do not overcharge and definitely don't use high charge current, unless you know the cell characteristics (how much is the max charge current). My guess is that the old laptop cells is very worn and cannot hold the full charge (full voltage) anymore.

 

Before wrapping the battery, I charged the pack using the wheels charger, to my discomfort the new battery did not charge to 4.2V but around 3.9V (I think it was higher than what I had achieved with my manual charging, but thinking of it I am a bit in doubt),

I have been driving the wheel for some time today, I have 3 diodes turned on on the 4 diode charge indicator, so almost full battery, the wheel is handling OK, I am still a bit uncomfortable about going to fast since I now two times have experiences the cut-out from the BMS, (it didn't cut out, and it is still shunted)

 

edit:

by the way, what are your thoughts on the fact that the battery seems to have a lower voltage than 4.2?

The less charge the battery-pack/cell has, the lower the voltage (that's how the battery displays/leds in the wheels work, they measure the total voltage of the battery pack, not real "charge"), and the single cell with "under-voltage" drops the voltage of the entire pack. Can't say if that can do any harm, or how it affects the pack that one of the cells also (probably) has different characteristics...

This is mostly guesswork on my part, @hobby16 probably knows a lot better.

 

[hobby16]

 

by the way, what are your thoughts on the fact that the battery seems to have a lower voltage than 4.2?

Nice repair ! A voltage dropping below 4.2V after removing the charger means the battery has lost some capacity. Which is natural coming from a salvaged part. Remember that from now on, when the BMS will perform balancing, it will discharge all cells to the voltage of cell of lowest voltage, not an optimal situation since the excess charge in good cells will be wasted for nothing by the BMS for the sake of balancing.  So charge up to 80% most of the times to avoid triggering balancing too often. Ideally, you should check the total Wh you can charge and if the capacity is too far from 130Wh, restart the repair with a better cell.

Your BMS won't cut anymore, try as hard as you can, you'll see this problem is no more and you can enjoy the wheel with confidence.

BTW, here is the update post of your mod on my blog (the thing about the heat sink may interest you) : http://hobby16.neowp.fr/2015/07/21/a2-generic-bms-shunt/