Help Please, Bike cutting Out

Hi All I have a new build and have been testing it and it keeps cutting out.

The setup is as follows:

Motor: QS 205 H50 3T V3

Controller: 24 FET
4115 MOSFET 84-132V Mark III High Endurance LYEN Edition Controller




BMS:


Battery: A123 prismatic pouch 20ah, 26s =85.8V (not sure on C rating but believe its high)


All the above are brand new

The bike has a 3 speed switch and on setting 1 and 2 all is fine, when I select position 3 and accelerate past 25mph approx the bike cuts out and I see on the Cycle Analyst (CA) "Low Voltage" and then completely shuts off.
I have tried it with the CA connected and also disconnected but it still cuts out.

Does anyone have any ideas of what i could tweak in the controller software maybe?

TIA

Mark

Can you check to see how many amps you are pulling from the battery before it cuts out? According to your battery spec sheet, the low voltage cutoff is ~ 2.00V per cell or 52V on your 26S pack. You controller is set to cut off at 55V. What is the voltage on your cycle analyst before it cuts out?

From the sounds of it you may be drawing too much juice from the battery. Once you check the voltage and amperes on the Cycle Analyst, you may have to decrease the rated current in the controller. Post you CA values and let us know.

will check it once the rain stops :?

I did just check the CA and Vmin was 10v but not sure when it takes the reading as something ie the controller/BMS shuts down the power.

As its a brand new battery pack do you think it needs a few cycles to get it up to full power ect?

Hi,
Check your battery cut off voltage setting on the CA (It's the 2nd page in where you set the battery type/number of cells/cut off voltage

and set it to 55v

Jonno

The bike cuts out with the CA disconnected, I did set the LVC in the CA to 55v the same as the controller, I read confusing lowest voltage figures for this type of battery some say 2.30v yet the data sheet says 2.00v.

Also when i purchased the controller from Edward Lyen he sent me the following statement about setting the LVC in the controller
"The low voltage cutoff formula for your high voltage controller. Program LVC (low voltage cutoff) = real (LVC) x 0.75. For example, real LVC for 24S lipo is 67.2 (24 cells x 2.8V per cell, then program LVC = (67.2)x 0.75 = 50.4. The maximum program regen voltage formula is (real regen x 0.75).

So the controller LVC should be 26 x2.30v=(59.80)x0.75=44.85v

or as per data sheet LVC shold be 26x2.00=(52.00)x0.75=39v (seems really low)

Any thoughts

Okay charged the bike up to 93.6v off the charger took it for a spin and it cut out when set at 55v and the CA read Vmin 79v so I assume it's not the LVC setting.

Another observation is that once its cut out the only way to reset the bike is to disconnect the battery from the BMS, maybe a stupid question is it safe to run the bike without the BMS inline and rely on the CA and controller settings to look after the max amps and LVC?

That means your BMS is cutting out, not the controller. The unplug resets the bms.

The CA can set max amps, and lvc for the whole pack. It will not do lvc for each cell like a bms can. You might have one bad cell, or even just one bad connection in the pack causing the sag. Bottom line, look at everything.

What's your max amps on the CA? That may tell you what amps your bms is cutting out at. That spec sheet is the cell, whats the spec on max amps on the bms?

Your battery spec sheet says 200 amps max continuos, 10c , but that does not mean 200 amps without sagging like grannies tits.

Just cruising at 30 mph though, that should not be much amps. Should only pull 10 amps once at 30. But can easily be a lot more getting to that speed. I'm wondering if you are running a false phase wire order, and drawing crazy amps when you try to accelerate or something. If you can't creep real slow up to 30 mph, then something is seriously wrong.

Might try limiting amps on the CA to 15, and see if you can at least reach 30 mph.

200 amps max from a 20 ah cell sounds a bit optimistic, using the rule cut all specs in half you'd likely get ok performance at 50 amps max. less than 5c in other words. BTW, 5c is f ing huge for many types of cells. I don't know anything about what you have, but it sounds like a lot! You might have some really optimistic specs there, like, specs for something, but not what you have.

I did set the controller to 20amps this morning and the CA read max amps at 42amps but it still cut out.

I have now disconnected the BMS and wired the battery direct to the controller and will see how it goes

Again it's pouring down with rain and better weather is due tomorrow so will try it then

Thanks

I hope the battery is what I think it is as I built it myself and the A123 cells were supplied by OSN power (could be fake)

IIRC, OSN was supplying "real" cells, but they were not new--they were recycled from salvaged/scrapped EV packs (the tabs are cut short). So the quality varies, depending on what those cells went thru before they were resold. I haven't personally dealt with any of those, but you can look up

OSN*

here on ES and find the posts and threads about them.


That said...you can check for voltage drop across your interconnects, which could cause the BMS or the controller to cut out if the total drop is enough.

Thanks amberwolf, the tabs were full tabs, I am going to try the bike less the BMS a little later and go from there, fingers crossed it the BMS tripping out

Thanks

Mark

You should also monitor the cell voltages under load (even if you can only do one at a time). Then you will know which one(s) is causing the BMS to trip.

If all the cell voltages are ok, then monitor the votlage across teh cell interconnects. If there is any voltage across them under load, then it's a bad connection and is too high a resistance.

So the bike worked fine with no BMS, I will try and rig something up to check each cell when under load and swap the culprit out

Thanks

One more thing that bugs me slightly is how sudden the power kicks in when I twist the throttle, is there a setting in the CA v2.4 that softens the initial power?

Thanks
Ps I did look in the manual but wasn't sure and didn't want to change anything before asking

So after some investigation I found there was a dead cell sitting at 0.00v.

Stripped the bad cell out the pack and replaced it with new cell, charged the pack using the BMS and went to bed.

Took the bike out for a 7 mile run without the BMS connected came home put it back on charge and thought I would check the individual voltages only to find 0v on cell 2 again.
I'm starting to think there's something wrong on channel 2 of the BMS.

Going to get it checked out on Monday at work!!!!!

It probably is a bad channel on the BMS, or a wiring issue on the balance wire for that group.

But:

When you put the new cell in, did you first charge it to the same state of charge as the rest of the cells?

If not, then you might have to let the system sit on the charger for days to weeks to bring that cell up to the level of the other cells.

If the cell was not charged at all when installed, and the other cells were mostly charged, and then you just let the charger run overnight, it would barely have any charge at all on that cell, because the balancing on typical BMS is really really slow.

Then test running it without a BMS means you don't even know if the new cell would have cutout due to low capacity/etc during the ride (unless you monitored it manually while riding).

If the cell wasn't charged enough and you ran it down on the test without knowing it, then it could've gone to (or below) 0V on it's own, and then the BMS might simply be refusing to charge the pack due to the below-LVC cell.

Yes the cell was charged to equal the voltage of the other cells.
Going to take a look at the BMS at a component level for that channel on Monday, have tried to contact Bestech who made the BMS but they are on holiday till the 25th of February.

If you have a meter that can read milliamps, you can put it in series with that cell's balance lead and see if there's any current flow when the cell has voltage on it that's below the HVC point--if there is, the channel is stuck on, and is draining that cell.