disconnecting battery from controller or leaving plugged in

[TiagoSantos]

Howdy guys - rookie question, I'm sure. I was planning on leaving the battery plugged in to the controller all the time, and just switching the controller on/off. It's a cell man 12 fet infineon controller, if that matters.. Is that a good plan? The battery has a separate charging plug, so I assumed that's what the idea was, I can charge it with the 2nd plug and leave the main connector on the whole time.

A local buddy that has a similar setup has had it connected this way for a couple of months and it seems to be working fine, but he told me a couple days ago that he tried disconnecting the battery and the anderson connector poles (or the plastic, not sure) had melted and fused the black connectors together. Then tonight, I was doing some wiring clean up and noticed my black connectors (I had left the battery plugged in overnight) were much harder to pull apart than I remembered.

Whaddaya guys think?

 

[biohazardman]

You need a battery cutoff switch that will disconnect everything from the batts for safety reasons. I have used this type of switch at 66V for quite some time without failure. http://endless-sphere.com/forums/viewtopic.php?f=3&t=32463 Melting connectors means the connectors are loose or not the right amperage for the job. Anderson Powerpoles come in 15, 30 and 45 amp in the smaller size we often use on our e bikes. I just use the 45 amp connectors on the bike.

 

[wesnewell]

No, it's not a good plan. The controller draws power from the battery even if it's tuned off. You need to disconnect at least the positive side of the battery to avoid draining it to 0V and ruining your battery when left connected for long periods of time.

 

[dogman dan]

I agree, use the switch when popping into a store or something, but unplug when you park for all day at work or all night at home.

Not worth the risk of damaging a battery to save yourself the tiny inconvenience of unplugging. Big EV's just use a contactor to do the same thing, but no need for that with the small wires on a bike.

 

[GMUseless]

Like everyone else said, always unplug that batt. But, when you start doing so, you'll now be seeing a spark when you reconnect the batteries (as a result of the caps in your controller quickly charging.) Search on 'pre-charge resistor' to eliminate this sparking.

 

[TiagoSantos]

Thanks guys, I'll keep unplugging then. Cell man includes a pre-charge resistor circuit on all his batteries/controllers so no spark for me

Was hoping to take the bike into work for the first time this morning, but an unexpected vet trip last night left me with no time to test the bike properly. Can't afford to not get to work on time today, so it'll have to wait another day! Actually the e-bike stuff I'm sure is fine, it's the normal bike bits that I haven't dialed in yet hehe.. Disc brakes rubbing, derailleur needs adjusting, stuff like that. I rode BMX bikes all my life, all of this fancy braking and shifting stuff is new to me.

Thanks again!

 

[Ypedal]

Agreed with others above, pull the plug for safety's sake.

If the bike is used daily, it's not such a big deal but if you were to ride home and run the pack near empty, and then leave it sit for a long period ( days,weeks, months ) it can over-discharge the pack and kill it.

That, and un-suspecting kids or peeps may accidentally turn it on and WHAM into a wall or worse..

Would you leave your car keys in the ignition with the driver's door wide open all the time ?

I turned my mtb into a big BMX by removing the rear multi speed and installing a single, removed the derailleur cable .. removed front derailleur too.. single speed is all you need with enough power on tap.

 

[TiagoSantos]

A keyed switch is in the works, I have a small switch I pulled from a milling machine that will be perfect

Yeah I'm considering converting to single speed, but since it's a big heavy full suspension downhill bike, it would mean a horrible ride home were I to lose power or have trouble with the motor on the way home! I'll keep the gears for a while until I trust this thing a bit more. I don't have a front derailleur, just the 7 speed cassette in the rear.

Cheers!

 

[TheBeastie]

My current 36V life battery from BMSbattery has a keyswitch on it that fully turns off power. But I am close to building a lipo battery and haven't even thought about switches.
What about this? http://www.ebay.com.au/itm/AC-380V-40A-500V-20A-On-Off-Position-Power-Cut-off-Universal-Changeover-Switch-/200834167990?pt=AU_B_I_Electrical_Test_Equipment&hash=item2ec2a634b6
I don't understand how yanking power clips out to be more clean then using a switch like the above?

 

[Ypedal]

AC switches dont burn up ... but used with DC the arc caused by the inrush current from the controller's capacitors kills them off unless you setup a pre-charge resistor.

 

[TiagoSantos]

I'm sure a switch like the one above will have the same problems as plugging/unplugging anderson connectors, as far as arcing between contacts, etc. Except they'll be much easier to replace when it finally breaks down, and more convenient to use in the meantime. Replacing a switch involves removing two nuts, swapping the switch and tightening the nuts again. Replacing anderson connectors means cutting off the current connectors, hoping you left enough wire to strip and crimp new connectors onto, etc.

As far as AC vs DC, my understanding is that when you switch off AC current, it'll die off on the next up or down cycle (you know, 60Hz and all that) without trouble. But DC current is always trying to get somewhere, so when you flip the switch, all the electrons bunch up on one side of the switch, while the other electrons are running away from the other side of the switch. This creates a big imbalance that eventually makes the bunched up electrons jump across the gap - ZAAAAP. And yeah, when you plug it in initially, the caps want to charge up really quickly, same sort of thing but reversed, ZAAAAP.

 

[Rassy]

For my main on/off switch I've been using DC rated circuit breakers similar to this for about eight years without any failures yet. The ones I actually use were purchased from WE (We're Electric) and they are no longer in business. They were also used on some of the larger electric scooters. WE listed them as handy for those that didn't like to see the spark.
http://www.affordable-solar.com/store/dc-circuit-breakers/midnite-solar-100-amp-150-VDC-panel-mount-breaker

 

[dnmun]

your black andersons overheated because they are not seating properly on each other when connected. it is better to hard wire the connection if possible or do a better job with the anderson install if you need to remove the battery.

if you have a ping pack you can turn off the BMS circuit current and that disables the battery. it can be done with other BMSs too but is more complicated than the ping signalab. when the BMS is shut off there is no current flowing in or out of the battery.

alanB discovered the drain down resistors on the input caps that are now used on the lyen's controllers and the cheap controllers from yescomusa do not have a separate wire for the controller circuit current.

some controllers like the old infineon controllers did not have the drain down resistors on the input caps and the controller circuit current was delivered to the controller on a smaller red wire, separate from the large red wire that goes to the mosfets. if you put a switch in the small red wire that delivers the circuit current then there is no draining of the battery when the switch is off.

if you use the switch for the circuit current, and a switch on the BMS circuit current then you can trap the charge on the input caps when both are turned off so there is no inrush current when the BMS is turned on. then turn on the controller switch and go.

 

[John in CR]

BS, Leave it connected except when you leave the bike idle for weeks or months. Install a good fuse (allow headroom for current and correct voltage rating) on the battery lead close to your battery as your protection against shorts. The switch to power up the controller and your ebrake are all you need to cut power in the event of a throttle runaway condition failure. Battery mains only need to be interrupted with a brushless motor in the event of a short, which is the job of a fuse, and only a fuse or circuit breaker is appropriate. Unfortunately most around here don't use fuses. Switches on your mains or frequently disconnecting your battery mains increase the chance of failure.

I've left batteries connected for as long as 2 years and have gotten to where I solder connections instead of using connectors. The pack on my cargo bike has been connected for over a year, and the one on the bike my son was riding for the year he was down has been connected for a year and a half. Those are both hard wired. I use RC Lipo on my SuperV, so I did leave connectors on it's 2 packs...In case 1 goes up and somehow the fuses don't work, I want to be able to yank the mains for the other pack and maybe save it if I act quickly enough.

John