i2 After more than 10 yrs, FINALLY got a Seg (with battery problems.)

[ions82]

Back around 2004, I was all hopped up on the idea of owning a Segway. A few years prior, I had managed to sustain a spinal cord injury that left me partially paralyzed. Having limited ambulation abilities, the Segway seemed a perfect fit. I was able to test-ride one when I met a really cool group of early adopters in NYC. Unfortunately, Segs have always been beyond my financial means.

Fast forwarding a decade or so, the enthusiasm for the possibility of owning a Segway had long since faded. Well, I was poking around in the Craigslist classifieds for bicycles (lifelong bike nut), and I stumbled across a post for a well-equipped Segway with a bad battery. The seller ended up giving it to me for a song. The deal of a lifetime, really. I now need to figure out what to do about the battery problem.

The unit is an i2, and I am not sure what year it is from. It doesn't appear to have seen much use. When I plug it in, one pack shows green while the other shows red. When I tried to swap the packs to see if the red light would folllow the pack, I found that the ball-end of an allen wrench had been broken off in one of the bolts. It led me to believe that the packs had never been removed (the yellow thread lock is pretty strong stuff.) I was able to get the packs off, and the red light did follow the pack from front to back.

When I checked the voltages, the green light shows 76V while the red lighter shows 64V. In some of the other threads that I read, dead packs were showing less than 10V. My friend and I are planning to put 70V at 100 mA into the pack to see if we can bring it up a little and get the on-board charger to bring it back to life. Being that it's already at 64V, is the problem less likely to be the state of charge but rather something in the PCB that is in the battery pack?

Please let me know if you can offer any advice as to whether or not this pack may be salvageable. I was expecting to see a much lower voltage on the red-light pack, so now I'm not sure what sort of problem I may be looking at. I've waited over ten years to finally own a Segway, so I can't wait to get this thing up and running. Thank you for any help, and my apologies for the long-winded post!

[ions82]

Upon doing a little more research, I am thinking that the battery in question may be toast. From what I read, it looks as though a high-voltage-but-not-charging state indicates that there is likely too much resistance in the battery circuit to properly charge. There are probably only one or two bad cells in most packs that get rebuilt. I'm thinking that I may have to, eventually, cough up for a new set of batteries. I'll have to save up to be able to spend that kind of coin. It's too bad that these packs aren't more user friendly and serviceable. Then again, considering the nature of Li-ion chemistry, I can understand why Segway wouldn't want people to be poking around inside a battery (without knowing exactly what they're doing.)

[Don M]

Batteries consist of 92 individual cells, 4 in parallel and 23 strings of 4 in series - About 3.3 volts for each paralleled set of 4, so if only one cell of the 4 shorts out, your max voltage is reduced by about 3.3 volts

You could have only 2 shorted cells in separate bundles of 4 cells and be down to around 70 volts and the BMS will not let it recharge in that condition. There are 'rebuilders' out there who will open up the pack, replace only the bad cells with identical cells scrounged from original Segway packs and epoxy it back together, giving you a little more life from your existing pack. It's not cheap though and an old battery probably isn't worth the investment

I would check the serial numbers on the battery pack, and if it's 8 or 10 years old, I wouldn't waste any money trying to fix it. The year of manufacture is the 5th and 6th digit after the 'C' on the serial number

You can buy a used pair, newer than your old ones for less than the $1800 a new pair would cost you - I just bought a pair of 2014 batteries (practically new, in Segway terms) for $900 shipped to me. You can probably find one older battery (a 2010 to 2012) for around $400 to $450 if you get lucky

Like you, we got a great deal on a pair of I2's so even if we have to spend some $$$ on newer batteries, they were still a good deal. You can post your I2's serial number here and someone will tell you what year it was manufactured

Good luck in your battery search - It appears we're competitors for the same scarce resource!

Don

[ions82]

That is some great insight, Don. It appears that these batteries were produced in July of 2010. So, not terribly old. However, it appears that even new-ish batteries can die prematurely. Well, "prematurely" in my mind. I'd like to think that a device such as the Segway wouldn't be so susceptible to these problems, but 92 batteries makes for a LOT of moving electrons. Plenty of potential for something to go awry.

Anyway, being a man of meager means (and the will to be self-sufficient) has got me wondering about the possibility of a DIY battery repair. My curiosity got the better of me, and I decided to have a look inside this problematic battery. Thus far, I've managed to remove the top "cover." I used a rotary tool (Dremel) with a router attachment. A 3/4" piece of bar stock fit perfectly as a guide, and a few passes with a tiny cutter separated the main seam along the battery (being very careful not to reach the BMS board that is just beneath that seam). Once that seam was removed, the rest just popped loose with the careful use of a small flathead screwdriver.

Apparently, the next step will be the cut all the wires along the edge that connect the BMS to the cell packs. Then, it can be lifted off to expose the packs. From what I've read, those are tough to get out. After reading through a thread on Endless-Sphere that illustrated a Seg battery disassembly, I am thinking that a DIY rebuild may be a bit beyond my skill set.

As for the rebuilders that are out there... I was under the impression that some of them use all new cells when rebuilding packs. Has anyone with a rebuilt battery ever taken a look inside to see what sort of work was done? Completely rebuilding a pack seems like a heck of a lot of work, and not all 18650 cells are created equal.

One thing is for sure, the battery packs are certainly the Achilles heel for the Segway. One bad apple/cell in the whole bunch, and the giant is brought down.

[Don M]

You are correct - Not all new 18650 cells are the same - It would not surprise me at all to learn that Valence rigorously tests thousands of cells to get 92 which are closely matched for use in a single battery - The remaining cells may be sold for someone else to use . . . . battery rebuilders?

I think the battery packs are of high quality and last a long time . . . . *if* they are properly cared for and recharged periodically (once a month or so) every month of their life. From what I understand, if you leave them connected to the Segway and don't periodically recharge them, the Info-Key communication system eventually pulls the batteries flat and that can ruin them to where they won't take a charge

I have one 2006 battery, one 2007 battery and one 2008 battery, all of which will give me 15 miles of range or more, but they are getting up in age and I'm going to replace them before they fail. I don't think leaving the Segway plugged in 24/7 is the best idea, but it's far better to do it that way than to not plug it in regularly to recharge

Series paralleling 18650 cells isn't a problem if they are quality, well matched cells. The Tesla Model S has an 85 KW battery made up of 96 groups of 74 cells each using the same 18650 cells used in our Segway battery packs - We have 92 cells per battery, they have 7,104 cells in series parallel and don't have battery longevity problems Pictures here: https://teslamotorsclub.com/tmc/thre...ry-pack.34934/

Pack - 16 modules wired in series. 403V fully charged.
Module - One of the 16 liquid cooled sets of cells that has a BMS board attached to it with a fully charged output of 25.2V from six sub-groups wired in series.
Sub-group - One of the six sets of cells within a module. These are all connected in parallel to form a high capacity 4.2V battery (fully charged). These appear to consist of about 74 individual cells. There are 96 total sub-groups.

Don

[ions82]

It seems that Segway Inc. may've really done themselves a disservice with these batteries. In looking around, I can't believe how many machines I've seen for sale with dead batteries. The packs are made up of a bunch of smaller groups of cells. Reasonable engineering would've made each of those individual groups serviceable/replaceable. So, instead of replacing a huge pack of 46 cells, it could simply be a matter of replacing a group of 8. Having dead machines that are only a few years old is pretty bad for business. Japanese auto makers became the worldwide leader through reliability. Segway almost seemed doomed from the get-go with $2,000 battery packs that were dying in just a few years. Imagine if brand new Japanese automobiles (in the 70s and 80s) had blown motors within the first five years of ownership. The entire country would currently be in poverty as their auto and machinery industry would've died in no time.

Anyway, these are thoughts that I've had after carefully disassembling the bad battery pack that came with the Segway I just bought. What a nightmare. It has virtually NO serviceability designed into it. Unless one is already a professional battery builder, trying to tackle it as DIY would be a fool's errand. I've decided to sell the good pack (along with as many other things as I can let go of) in an effort to buy new batteries. After all these years, at least I HAVE a Segway. Now, if I can just get it going!

[Don M]

Originally Posted by Don M

Batteries consist of 92 individual cells, 4 in parallel and 23 strings of 4 in series - About 3.3 volts for each paralleled set of 4, so if only one cell of the 4 shorts out, your max voltage is reduced by about 3.3 volts

Reading the Tesla thread, a shorted cell is very unlikely to lower the pack voltage as I suggested here - In the Tesla pack every one of the 7,104 cells has a fusable link attached to it, so a shorted cell blows it's fuse and doesn't affect the voltage of the pack as a whole. Since they are paralleling 74 18650 cells, a shorted cell just lowers the capacity of that bank of 74 down to a bank of 73

I have no idea how this works in Segway packs, but there are folks here who rebuild packs and they will know. I love battery pack discussions . . . . I learn something new every day!

Don