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Joff

IPS 122 tilt forward on acceleration

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Most of the cells were 3.9   The lowest (which I think is the new one) was 3.87 and the highest was 3.95  That seems like a narrow range, but I don't know what the spec is or how hard the BMS had to work to get that narrow range. 

 

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The gap in voltages is too high to what I experienced (+- 0.02v i.e. 0.04 v gap). I think your new cells are charging slower (lower current) than the rest so most probably the old ones are getting to 4.1 quickly and then the charging is shut off. once it is shut off balancing is transferring some energy back to the less charged batteries. did you allow the batteries to rest for a few hours connected to the board and try checking the voltages again?

I suspect that the new ones taking less charging current are probably indicating to the BMS that they can't take much more due to low current supplied on them (which might not be the case) When the engineers get back after spring festival I will try to get back to you with a formal answer as I don't know the exact working method of their BMS

PS 26 minutes riding wouldn't take much to charge it back. I think it should charge in max 2hours from a battery pack with minimal voltage (shown empty) on the original charger

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8 hours ago, IPS Malta said:

I think your new cells are charging slower (lower current)

I was thinking because the new ones have more capacity, they take longer to fill. Good to know that such a small difference matters. After  filling the battery with a direct connection, the new ones were  0.15v short of the others. I then charged that pair by itself to match the rest.  It would be some work, but I could replace all the cells with new for less than the cost of a board. I have a kingsong 18ay for my main euc, so doing a weird thing to charge the IPS isn't a problem for now. Get those intermittent problems figured out before dumping more money!

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9 hours ago, IPS Malta said:

did you allow the batteries to rest for a few hours connected to the board and try checking the voltages again?

I will try that in the future!

 

9 hours ago, IPS Malta said:

When the engineers get back after spring festival I will try to get back to you with a formal answer

Might they know the specs of the original cells? Maybe replacement cells with less capacity would be a better match!

Thank you!

 

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On 15/12/2017 at 4:35 PM, Joff said:

I recently purchased a used IPS 122 on ebay.  I have several Electric unicycles already (including a kingsong 18) but I figured for $ 227, why not?  I really don't like the feel of it. It tilts forward a lot on acceleration.  I feel like I am going up on my tippy toes to stay on. On bumpy ground, it can tilt so far forward that the front edge of the plastic fender catches on the ground and I have to hop off!  On slowing down it, it tilts back. I don't mind having tilt back at high speed to keep me from going too fast,  but I really don't want all this tilting back and forth at low speed. Is there any benefit to it? It does not have bluetooth. Can the motherboard be swapped with one that does have bluetooth, and if it can, would I be able to adjust the ride feel as I can on my Kingsong?

I've bought IPS121 with same characteristics as your two years ago. I have your same problems. It's uncomfortable to use. Tiltback is too pronunciated, and get worse when battery is under 50% or similar. Also mine does not have BT and has 19kmh limit. And no way to change mainboard with same model doing 30kmh and BT. But going 19kmh on this wheel is quite painful. If you search, I wrote some messages about two years ago. Also I posted the procedure to calibrate the wheel. You could set some degrees forward to have lesser tiltback when you go at about 15 kmh. Anyway 227$ is also OK, it's a robust wheel, but I paid it 780€ two years ago, and it was not the latest wheel on market.

Edited by fabio70mi
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Thank you Fabio, for taking the time to write as much as you have on the subject.   I read a lot of your posts when I was trying to figure out what was going on with this, even before I started posting about mine. I used your info to re-calibrate the balance. I have not experienced any pain.  After replacing two bad cells in the battery and recalibrating the balance,  I am actually very happy with how it feels. I have not tried to go fast on it yet,  but it is great for going forward and backwards, tight figure 8's  maneuvering on my Patio. I have a Kingsong 18 for road use. I'm in a rough area of Baltimore and I figure the extra speed could come in handy for outrunning petty thieves! 

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I've run it long enough to have a feel for what is going on.  I don't think there are any intermittent connectivity issues. it works fine if I don't push it too hard. It runs down to about 60volts. and then blinks and beeps. fun time is over. Then it will charge to 62.3 volts and no more. I figured it was a battery cell balance issue. First time, I thought  the new pair of batteries were higher after the battery ran down and lower after recharging. This time they were a little higher than the others after charging. I saw 3.83, 3.9, 3.9, 3.87, 3.9, 3.87, 3.87, 3.9, 4.02, 3.9, 3.88, 3.89, 3.91  and 3.92  again, 62.3 total volts  So why is it charging no further? The main board has 67 volts going to it. The bms built in to the board is not charging it further.   Maybe the new pair is too much higher than the others? So I ran it from 4.02 down  to 3.89   Put it on the charger and it looked like it was charging but not for long, - a minute or two. still 62.3v

So was it the lowest voltage keeping the thing from charging? 3.83 was the lowest, I charged that one up to 3.9.  put the charger on the whole EUC again still stuck at 62.3 I could charge the thing with a direct connection to the power wires of the battery, but I figure it is good to get the thing to work as it was originally intended for safety reasons. Will the bms be able to protect the battery if I am running power direct  to the battery? Kinda doubt it. 

I received a shipment of 32,  2500mah 20 amp replacement batteries for building a replacement battery. I'm still not sure if building a new battery will fix the problem though. The voltage across the cells seems close enough and that makes me think it is a BMS/charging problem - the BMS is built into the main board, so I don't want to build a battery for a euc that needs an expensive and hard to find main board. Hmm..

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I checked on my IPS i5 (i don't think they changed the logic of the BMS much) but on a full charge from like 5days ago batteries on the app show 4.08 and 4.09v on all cells (20700 not 18650 but since they are on same chemistry I assume same voltages). I don't think there's an easy way to build a temporary battery without welding them.

At best see that you can raise individually the voltages of the cells to 4.05 at least. if you're using an RC charger, that should stop if they are not taking enough current (meaning full) if that's the case on a lower than 4.02v, that cell is very degraded and most likely the cause. If I get to this stage personally I would build the new battery as you already had dead cells, some would have been identified as aged batteries, the rest won't last long and you will have to open again and do all this testing process again. I will try to confirm with IPS when they are back from holidays with regards.

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Thank you for taking the time to check your voltages! I find that encouraging, that your numbers are so close.  It does not absolutely  rule out that my BMS has a problem that causes my cells to be less balanced, but it looks like making a new battery is a reasonable plan.  I have some  8 and 11 pin connectors on order. I figure I'll make a copy of the old battery before dismantling it so I can check my work against it.  

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On a BT version of IPS, you can check the Voltages of each cell individually from the APP. You have like a matrix of 4x4  (16 cells) with separate voltages, so that was no big deal.:) One reason for being so close is that my i5 is not that old, but even on my LHOTZ and Zero there were very close. When I get back to my country I will check on them as they might differ after a long time not having proper battery cycles and will keep you guys updated on 8 months rest would result in them.

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I built a new battery, and carefully labeled all the pairs of cells in the old and new battery and transferred the wires one by one to  make sure everything was wired properly.  The new cells came  with about 3.5 volts each. When I put the unicycle on the charger, it took some charge, but not nearly enough.  I put a charger directly on the battery output and it charged up to 67.2 and the balance on the individual cells was perfect.  The Unicycle  ran fine, but only until the voltage got down to 66.1 then it beeps and the "on/off" button blinks twice green and twice red, over and over.  if I turn it off and restart it seems normal for 15 seconds, then beeps and blinks. I thought maybe a balance wire is not reaching the BMS on the main board, so I checked them at the board and they all are good. 4.13 on every cell pair. 

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I decided to try to write a email to the IPS website and see if the can tell me where I can buy a main board. I turned the thing on to see how long it takes before it starts beeping. first try 15 seconds. Second try it didn't beep after 20 seconds so I rode it for 2 minutes  and then it started beeping. Battery still has good charge, 65.9 volts and between 4.10 and 4.11 on all the cells. After checking voltages, I can turned it on again. Over 10 minutes without beeping just sitting there. A puzzling problem, for sure!

 

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I found I can simulate the problem by disconnecting one of the connectors to the bms.  15 seconds after disconnecting it I get the same beeping and flashing switch as I get when it is having the problem. 

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IPS will send me a new board, one with bluetooth for $250 with free shipping.  I would do that , but now it is working perfectly. I can leave it on for hours and I took a mile ride with no troubles. It even seems to charge ok.

 

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