Did I kill all my LiPo??

[stuartjbecker]

I recently left my electric bike out in the garage plugged up to 28s 2p of LiPo battery (fourteen 4s1p Turnigy hardcase packs) for 3 weeks. I have a Crystalyte "on/off" switch hooked up to the controller that I am certain was switched to off. However, yesterday I brought them inside, and found that the pack totaled 8.5V, at only .3V per cell!!

How could this have happened when the controller (Lyen 12-4115) was switched to off? Could the switch have failed and left the controller on, sucking up the batteries for 3 weeks? See attached diagram of my setup; many thanks for everyone's input.



Uploaded with ImageShack.us

 

[rjoe]

The on/off switch only makes the controller inactive. The capacitors and other stuff are still sucking juice

 

[Trackman417]

For storage I take the positive plugs off, which have the precharge and the regular plug for easy connecting to the controller to see where the pack volatage is at.

 

[SamTexas]

The on/off switch only makes the controller inactive. The capacitors and other stuff are still sucking juice

Hmm... Not sure about this.
I have 3 Infineon controllers (ebikes.ca). No parasitic draw when they are turned off.

How could this have happened when the controller (Lyen 12-4115) was switched to off? Could the switch have failed and left the controller on, sucking up the batteries for 3 weeks?

Hopefully it's a defective switch or incorrect wiring. Else, it's pretty bad news for that Lyen controller.

 

[veloman]

I haven't done any tests over a day or two, but with the controller switch off, the amount of drain is so small that it would likely take a year to kill your battery. I've left my switch on overnight a few times, and it equates to a few more minutes on the charger. Not scientific though.

 

[Gregory]

Hi, first off I love your wood cad drawing!.

It will take you one minute to put your multimeter on amps, and insert it BETWEEN the on/off switch anderson. That will probably confirm the controller is slowly bleeding down the battery. I wouldn't have thought it was that much though.

You can test the switch using the ohms or continuity setting, but probably not the culprit.

Greg.

Edit: and yes the battery is killed.

 

[Hillhater]

You may have more knowledge and faith in technology etc, than i have...but...
I NEVER leave a lipo pack connected to ANYTHING ( bike , charger, switch, voltmeter, BMC, etc) for any longer than essential.
to leave a pack that size connected to the controller, unused in a garage for 3 weeks, ...makes me shiver !
....I would consider myself lucky it was only the pack that died !

 

[dnmun]

Alan B found a drain down resistor on the input caps so the battery continued to discharge through that drain down resistor. i think it was 2kR so you can estimate how long it would take to discharge your pack.

 

[SamTexas]

The on/off switch only makes the controller inactive. The capacitors and other stuff are still sucking juice

Which controller is this? A Lyen controller?

 

[stuartjbecker]

Thanks dnmun, just the answer I was looking for! Just to clarify: even if the small red wire which powers up the Lyen controller is disconnected, the drain down resistors will continue to discharge the battery? Seems that the switch I added would better be suited in series between the battery (+) and controller (+), to prevent this from happening...

If I do that, will I be safe from drain when switched off? I don't want to get this wrong again and toast another batch of batteries. I like to leave the batteries on the bike because it is a hassle and because I get a nasty spark when plugging up the battery to the controller (which has started to marr the connectors).

Thanks for your input.

 

[nechaus]

some super cheap brushless controllers can sometimes draw enough to kill your batteries if you leave it on after a big ride that used all all your juice.

iv left my bike for 2 days with a flat pack, forgot about charging, came back to a pack of fatties @ 0 volts,
that was a few years ago now, since that day i always disconnect my main power leads.. my kellys draw about 40 ma when left on.. not much at all..

 

[dnmun]

you can open the controller and unsolder the resistor like alan did. that solves the drain down problem on the mosfets.

you can use the precharging circuit too, or remove the resistor and leave the power side connected all the time so you don't have the connecting spark problem.

he is right, and on some of the cheap controllers you cannot even isolate and turn off the circuit current so you need a switch and precharge.

most controllers are about 50-60mA.

 

[miuan]

On all XieChang controllers that I've opened so far, the bleed resistor is called R203 and I always pop it off as soon as I can, although I always disconnect the battery leads when not using the bike. Please take care, since without R203 your caps will still be charged long after you unplug the battery, which can be dangerous if you open the controller. The best way to discharge it is leave the switch ON, so the linear regulators can take the charge away into the 12V rail.

 

[amberwolf]

To answer the question in the title of the thread itself, the unfortunate answer is probably "yes". I wouldn't expect it to be safe to recharge them after going down that far in voltage. They may well be *able* to recharge, but based on reports in threads listed here:
http://www.endless-sphere.com/w/index.php/Fires
I fully expect that at some point one or more of them will fail dramatically.

 

[dogman dan]

I agree, even if they could be revived, that lipo is now dangerous to charge. OUCH. But one ray of sunshine is they didn't catch fire while discharging that low.

 

[miuan]

You have to punish them too hard to make them explode. They will never catch fire if discharged at a low rate - the heat generated in the process is too low to cause anything.. they are also more likely to be successfully revived as long as high rate overdischarge hadn't left permanent damage to the cell chemistry.

 

[Bikemad]

my kellys draw about 40 ma when left on.. not much at all..

Although 40mA may seem insignificant, it's still more than enough to kill a fully charged 16Ah pack if you should accidentally leave it connected and turned on for three weeks.

16Ah/0.040A = 400hrs or 16 days and 16 hours.

Alan

 

[23skidoo]

Sympathies for the loss of Lipo.

Please let us know if you decide to risk charging them. Besides watching for immediate combustion, watch for puffing over the upcoming cycles.

Monitoring cell-level voltage after disconnecting for a while may give some idea if certain cells are viable, and exclude a measurement error.

Best wishes