Rebuilding battery pack- spare cell testing

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Joshteacher
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Rebuilding battery pack- spare cell testing

Hi All, Happy New Year!

My range has been limited to about 12-15 miles on my 2008 VX-1, and I'd like to see about replacing some NIMH cells. I have come into possession of some replacement cells, but I think they are too far discharged. A few questions:

1. Is there any way I can recharge spare cells for testing without using the scooter's charger? A Freddy charger is not an option for me.

3. Some replacement cells have some dirt/dust on them. What's the best way to clean them off? A dry cloth only, or is there something else I can use?

4. Can I test a row of 8 cells with a 50w bulb? Can I just wire it up with a basic light bulb mount and wires on either end of the series?

Any help is greatly appreciated, thanks!

Frolle
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Re: Rebuilding battery pack- spare cell testing

1. Yes, it is. I would use a IMAX-charger, or similar.

3. I little water and dry with cloth wolud be fine. I'm not sure destilled water would make it better, but maybe..
The cells are sealed (wit a overpressure valve), so nothing can get in or out under normal usage.

4. Yes, you can use a 50W bulb, but eight full cells contains about 288Wh (1,2V x 30Ah x 8pcs.), so it will take 5-6h to empty them. But you can use more bulbs in parallel. And you have to messure every cell to se the status.

I have used a IMAX B8 charger from Hobbyking.com to test capacity of my cells, or to be more precise four of those chargers, this to speed up the process. There is the smaller IMAX B5 with built in powersupply also, but the discharge current is only 1 amp, instead of 5 amp on the B8.
The charger will give info about how much power that goes in to the battery, and how much was released.

All my cells was about 28-33Ah but one, witch was 18Ah.

I tested them all, four by four. Automatic charge and disharge. Marked every cell with a permanent filt pen with the capacity. The 18Ah cell was replaced.

I wold say a few of Imax B8 is VERY useful whe playing around with cells. It can charge up to 27 cells in serie.

// Frolle

Mik
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Re: Rebuilding battery pack- spare cell testing

I recently bought a SkyRC QUATTRO charger in addition to my existing RT808D charger.

I finally got around to install LogView and use it with the RT808D, the graphical display makes it much easier to spot the bad cells.

I have not really used these chargers for the Vectrix cells, it takes too long to discharge 30Ah or more at the maximum 1A DCG rate.

Ideally, you should charge and discharge each cell twice (or more) by itself, but doing it to 9- or 8-cell modules is also an option.

I have only used the chargers for Prius 6.5Ah cells, they can discharge 6 NiMH cells in series at 1A, but if I discharge 12 cells in series, the current drops to 0.6A.

A CBA3 works much better for cell discharging, because it can do it at higher currents.

This information may be used entirely at your own risk.

There is always a way if there is no other way!

Joshteacher
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Re: Rebuilding battery pack- spare cell testing

An update: I have tested all the spare cells and identified 21 as potential replacements. I used a 12V, 1.5A battery charger from a local auto parts store. Currently, I'm charging up the good cells in groups of 8 so that I can then check them on a load using a 12V bulb. Next week I'm opening up the battery pack on my scooter and testing all the cells to find the duds using the 12V bulb to load test. Any advice on swapping the cells? Can I put the replacements in the same spot as the duds, or would the cells benefit from a "rotation"?

ofx210p
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Re: Rebuilding battery pack- spare cell testing

Not sure if rotation has any benefit other than maybe top to bottom rotations but to remind you how to get the packs apart heres the link to the video for individual cell replacement.

http://www.youtube.com/watch?v=aNkiF1iS6hY

Aircon
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Re: Rebuilding battery pack- spare cell testing

I still have a full pack of original batteries sitting in my garage waiting to be thrown away. Last ride with them I did 40km. Someone come and take them!

I'm in Melbourne Aus.

Joshteacher
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Re: Rebuilding battery pack- spare cell testing

ofx210p- seriously, that video is gold! I used it to create my own rig to remove the good spare cells from the duds. Hopefully I can do a good job putting it all back together with the scooter battery pack.

ofx210p
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Re: Rebuilding battery pack- spare cell testing

I'm sure thats why we're all here - trying to spread best practises across the vectrix world.

R
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Re: Rebuilding battery pack- spare cell testing

Frolle, how do you test the capacity of the cells with the Imax B8? Do you log the data in a computer? how do you know the voltage of each cell during the cycling?

Joshteacher
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Re: Rebuilding battery pack- spare cell testing

An update: last week I pulled out the battery packs, and today was disassembling and testing the rows. Here's what I found: each one of the three right hand rows of the rear battery pack had three cells that need replacing. While I had each row powering a 50W bulb, I tested each cell with a voltmeter. Bad cells would send the needle going to the wrong direction! At first I thought I mixed up + and -, but no, those cells had reverse voltages. Thankfully, I only have to rebuild three rows to replace the duds. I ran the scooter down pretty low before I took out the battery, so I'm hoping there's enough when everything's put back together.

The tape Vectrix uses to connect the black battery shells, is that just 2 inch electrical tape? I'm trying to find it here in Los Angeles. Any advice would be appreciated.

Frolle
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Re: Rebuilding battery pack- spare cell testing

R:
I just set the B8 to stop dis-charge at 0.9 (or was it 1.0V..), and I choose the cycle-program.
Then the battety is fylly charged using DeltaV algoritm, then it is dis-charged to the pre defined voltage.
Then you can se on the mA-counter how much went in to the cell, and how much was drained from it.
Most of my cells had a capacity of 28-29 Ah, a few little more then 30, and one at 18Ah, which was replaced.
I did set the cut-off in the charger to 45000mA, so it could not charge more then 45Ah in to my empty cells.

Now I use this for checking the helth from time to time:
http://visforvoltage.org/forum/12349-monitor-cell-balance-status-three-three-50-solution.

Joshteacher:
Any good tape will do.
Can you not get the cells to be non-reverted, and test the capacity?
If you are lucky, they are not damaged.

Joshteacher
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Re: Rebuilding battery pack- spare cell testing

Frolle: I don't know how to get the cells non-reverted. I'm pretty limited on the equipment I have to use. An IMAX charger isn't available to me. Any suggestions would be appreciated!

Mik
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Re: Rebuilding battery pack- spare cell testing

An update: last week I pulled out the battery packs, and today was disassembling and testing the rows. Here's what I found: each one of the three right hand rows of the rear battery pack had three cells that need replacing. While I had each row powering a 50W bulb, I tested each cell with a voltmeter. Bad cells would send the needle going to the wrong direction! At first I thought I mixed up + and -, but no, those cells had reverse voltages. Thankfully, I only have to rebuild three rows to replace the duds. I ran the scooter down pretty low before I took out the battery, so I'm hoping there's enough when everything's put back together.

The tape Vectrix uses to connect the black battery shells, is that just 2 inch electrical tape? I'm trying to find it here in Los Angeles. Any advice would be appreciated.

You need to at least check for swollen cells in addition to the very basic test you have done. You will probably find a swollen cell (or several) among those that were reversing under the small load, so then you will know what to look for in the rest of the battery pack. You can feel the swelling better than seeing it when you run a finger along the sides of a module.

This information may be used entirely at your own risk.

There is always a way if there is no other way!

Joshteacher
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Re: Rebuilding battery pack- spare cell testing

Even if a cell has a good voltage reading under a small load, how bad of a problem is the swelling? Compared to a reversed voltage, is it worse? I've seen some swollen cells perform decently under the light bulb load, but I won't have enough spares to replace them too.

Mik
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Re: Rebuilding battery pack- spare cell testing

Even if a cell has a good voltage reading under a small load, how bad of a problem is the swelling? Compared to a reversed voltage, is it worse? I've seen some swollen cells perform decently under the light bulb load, but I won't have enough spares to replace them too.

Then, I'm sorry to say, you need to do more testing so that you can avoid discarding any good cells while leaving bad cells in.

In my experience, swelling is the easiest and most reliable indicator of a bad cell. I found no cells that were badly damaged that were not also swollen, and I found that practically all cells that were swollen showed problems when being tested with more in-depth methods than the one you have done so far.

The only alternative that I can think of would be to somehow get more good cells and replace all swollen and all "reversing under small load at unknown SOC cells".

I think that if you throw out the cells that you identified in your discharge test and leave the swollen ones in, you will almost certainly have a poor result. However, you will still have the cells to do it all over again if you want to try it.

Good luck, Mik

This information may be used entirely at your own risk.

There is always a way if there is no other way!

Joshteacher
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Re: Rebuilding battery pack- spare cell testing

UPDATE: I finished the rebuild about a month ago and I have increased my range! I definitely am not at what a fully restored battery should be, but I have enough juice to go faster, and I've shaved 5-6 minutes off of my commute. This is exactly what I was hoping to accomplish, so I'm very satisfied with the results. Thank you, thank you, thank you to everyone who chimed in and gave your input. Maybe by next summer I'll have an IMAX charger and do a better job of ridding the battery of swollen cells. This is a very encouraging group, and I appreciate your expertise and willingness to help!

ofx210p
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Re: Rebuilding battery pack- spare cell testing

I have to ask - what is the range now ?
Oh and congratulations !

Joshteacher
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Re: Rebuilding battery pack- spare cell testing

I haven't taken a fully charged ride down to the red light yet, but I'm estimating from my voltage after the 13 mile commute that I can go about 20 miles with judicious riding on the streets (not exceeding 30 mph).

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