Every time I connect my battery (48v) to the bike it makes a big spark in the plug (XT90)
I know the spark is normal but the question is if this can damage my controller and if I should do something to correct this like installing a switch?
I've never lost a controller running that way for many, many years up to 62V. Higher voltages tend to be more significant and better served with a pre-charge circuit. Common topic for many years now.
One thing that seems to help minimize the size of spark is keeping metal contacts completely free and clean of oil, grease, wax, etc. An Alcohol wash may be worth a try.
You will probably not damage the controller, but your plug will get worn out fast.
There are different solutions for this unpleasant thing.
Model airplane guys with 12s setups or similar often use a "preload cable". Its basically a thin cable with a resistor.
They connect the battery to the esc with that cable which is just a parallell cable to the main power cables.
The resistor prevents a big spark but still equals voltage for the main plugs.
I have also seen connectors with the above functionality prebuilt.
I use a big marine power switch for my 12s battery. Its unclear how the switch likes the job tho.
It might get worn out as I am guessing sparks are flying inside it since its made for 12v.
But so far so good.
This is the reason why I prefer Anderson power pole connectors for that plug. They scorch the tips, but on full insertion they make clean contact. I've never bothered with the pre charge circuit, even at 72v.
If I connect and have the switch on the ON position it does the same but when I have the switch on the OFF position there is no spark when plugging the battery pack. A cheaper option is having a on/off switch.
Every time I connect my battery (48v) to the bike it makes a big spark in the plug (XT90)
I know the spark is normal but the question is if this can damage my controller and if I should do something to correct this like installing a switch?
you will not destroy the controller but the electrolytic caps inside of them will get weaker if you dont precharge them.
The best way to eliminate the sparks are antispark connectors or a precharge circuit with mosfets (also can turn it on with a keyswitch if you want).
the connectors i use look like this:
they are also available in 4mm or 8mm for lower or higher loads. On one connector there are a few resistors (about 30 ohms) on a ring seperated from the real connector. The bigger the voltage and the more µF the caps have the longer you sould stay on the ring before plug them completely together.
That's a very simple looking resistor setup. Where exactly do you get those?
Folks like me aren't into soldering up tiny stuff very much. Bigger things I can still see, like those bullets are no problem. Half my preference for andersons is I can just crimp em.
The thing I keep wondering is why don't controllers come with something built in if it's all that damaging to a good cap. I don't doubt defective ones blow.
take a look at some RC-model shops. They should have such antispark bullets.
On low power controller you can simple plug them together as it is usual. On my 18 Fet with 90volt battery i have to stay >2seconds on the ring to sure have no sparks.
Okey dokey, soon as my city has one, I could do that. I was hoping you had a web link to some. The places I used to look at a lot, EP Buddy, or Hobby King, didn't seem to have them. I'll just go googling then.
I never had any problems myself, even with my 120v controller. I admit you do learn to give em a quick brush, then push in all the way. I'd like to have the source handy for the noobs I respond to so much.
Back from google land, Here's the USA sellers of the item.
http://www.jetiusa.com/dealers.php
One's only 400 miles from me. 10 bucks for the item from them, plus another 9 for shipping unless I spend more. Cheap compared to a new controller. I like the item, it looks very convenient to use.
Good drawing Wesnewell, and this is what I recommend everybody do if they are getting sparking when connecting their battery to their load, and in any system over~40V or so. We are guarding against damage to the connectors, and in some cases control electronics from a spike of inrush current when making that connection. If you have contactors (relays) making these connections, damage to the contacts--shortening their useful life dramatically or even welding them together--can occur if not using a proper precharge circuit. In car systems running at hundreds of Volts, this becomes a critical function to get right.
An on/off switch for the controller may be a good option in an ebike system, but bear in mind that the switch should be rated for whatever abuse you're trying to keep off the power connector. The switch just moves the problem downstream, it doesn't eliminate the root cause of the phenomenon. Only proper precharge can do that.
EDIT: 150 Ohms is a pretty big value for a precharge resistor (looking again at Wes's drawing). Typical EV packs I've worked with have values in the range of 25 Ohms or less, though they may be enormous power resistors. The optimum value is found by measuring the capacitance on the HV bus and tailoring the resistor to meet a target precharge time. Ideally, precharge the HV bus to 95% of the operating voltage before making the main connection.
Hey,
found another nice antispark connectors. I use them on my bike. They have 7mm and are rated for 180/300A.
Care should be taken to not wet the thread on the bullets when soldering. Otherwise you will not be able to screw on the plastic housing..
The current inrush demonstrated by the spark wears on the capacitors over time, but that's a relatively minor issue. The significant issue with disconnecting batteries all the time is pushing the failure rate to or near 100%. Imagine the fire rate with cars if drivers manually connected their fuel line every time they needed to use their car. This is about the same thing. Fiddling with battery connections is a crappy, dangerous, and unnecessarily expensive hobby.
The current inrush demonstrated by the spark wears on the capacitors over time, but that's a relatively minor issue. The significant issue with disconnecting batteries all the time is pushing the failure rate to or near 100%. Imagine the fire rate with cars if drivers manually connected their fuel line every time they needed to use their car. This is about the same thing. Fiddling with battery connections is a crappy, dangerous, and unnecessarily expensive hobby.
dont talk so pessimistic for example i turn on my bike with a keyswitch and a masterswitch. even with a masterswitch you need some connectors. the antispark resistor also works like a fuse in the case if the bullets come together..
eBikes aren't cars. Using RC Lipo I simply don't like anything left connected to battery and the only way to do high voltage/current DC switching properly requires way too much time, cost and trouble for my simple needs.
However, some great no-spark connector products/ideas. Thanks!!!
Madin88, it's not pessimism just reality. I'm not arguing against connectors, just regularly disconnecting them. Getting away from virtually guaranteed failure in favor of a low chance of failure that's also far more convenient is just common sense.
Ykick, that fear is a carryover from brushed motors, where you must be able to cut power mains because a failure can result in a runaway condition. With our brushless controllers power only needs to be cut to the MCU, a less than 100mA supply with separate wiring typically supplied on our controllers. That's easily handled with a keyswitch that also adds a level of security. With the MCU turned off the string of switches (the mosfets) controlling the power mains flow can't start switching on their own. While your bike is parked a double failure would be required in both high and low side fets to create a short, and even if that did happen they'd act like a fuse anyway and immediately blow. I have a box of failed controllers, and not a single one resulted in a sustained short of the battery mains. I don't think it's even possible, so why again do you think your battery needs to be disconnected? If you have a drain-down resistor, remove it, and remember to take care and drain and short the caps if you're taking the controller apart.
There's all this baseless fear causing people to go to significant inconvenience, yet I doubt even 1 in 10 include a proper fuse in their system and that IS something to be afraid of, especially with so many of us running quite lethal voltages.
My precharge works great, however, I'm curious if the Jeti or AS150 connectors will work well on 24s lipo. Certainly looks like an easy solution which wasn't available a few years back.
Definitely. I have a few 100 ohm resistors laying around so one is always easy to find that once every year or two that I need to reconnect my battery pack. They're useful in that they help you make sure you don't have a short, because if the resistor heats up quickly you know something is wrong and don't complete the connection. I also find it even more important to drain caps when a controller comes off, because if you screw up and let the leads touch that spark goes off like a fire cracker. The larger the controller and caps, the bigger the crack.
@ John
the Adaptto controller i use unfortunately doesn't have a ignition wire for powering on the mcu, so i have to disconnect battery every time with a masterswitch.
For the case the masterswitch blow up, i can disconnect it and plug the battery direct to the controller. To drain caps on controller side you can also simply plug them together.
wesnewell said:
My precharge works great, however, I'm curious if the Jeti or AS150 connectors will work well on 24s lipo. Certainly looks like an easy solution which wasn't available a few years back.
The Jeti 5,5mm do have about 30 ohm and they work well on my 22s liIon pack. Just stay about 2sec on the "precharge ring" before completely plug them together and you will never see a spark.
The AS connectors i measured about 5ohm so precharge should go even faster. Maybe there will be a tiny spark at high volts because 5ohm are very low..
One time i forgot to plug the Jeti bullets completely together. I sit on my bike and pushed the throttle. The motor turned a little and voltage dropped quickly to low cutoff.
The plug was a bit warm but no damage to the resistors
Thanks. I ordered the AS150 (AX150) from HK yesterday to test. Hope it's more than 5 ohm. I'm afraid it will still spark badly on 24s. I use 150 ohm now which works good from 12 -24s lipo.
Got the ones from HK in today. Across resistor only measured 5 ohm on mu cheap DVM, but that's about the same as I got with my 40 yr old rat shack analog meter too. I'll try one when I get a chance, which may be a while as I've got other things to do, but I'm not too optimistic since I use 150 ohm 10W resistors in my circuit. The connectors screw into the housing, which makes it nice, and when you put them together, the plastic housing will shield any spark if it's not big enough to melt them.
Got the ones from HK in today. Across resistor only measured 5 ohm on mu cheap DVM, but that's about the same as I got with my 40 yr old rat shack analog meter too. I'll try one when I get a chance, which may be a while as I've got other things to do, but I'm not too optimistic since I use 150 ohm 10W resistors in my circuit. The connectors screw into the housing, which makes it nice, and when you put them together, the plastic housing will shield any spark if it's not big enough to melt them.
i never tested the antispark function before on these connectors, because i have a precharge circuit with keyswitch. yesterday i did a test which was very dissapointing:
pack 85V. controller has about 3000µF capacitance. while plug them together there was a little spark on tip of the bullet. ok no big problem. i put them complete together and everything worked well (no more sparking).
I did a second test and ohh.. no little sparking on the tip. something wrong?? when put them complete togehter it sparks that much my connecors almost melt tegether!!
measured the resistor: it was dead
I hope the caps in controller are not hurt - what do you think? Are they got weakened?
took the resistor out of the bullet:
dead and broken. it also seems to be very fragile mechanically.
Don't use these cheap crap AS150 connectors for precharge at that high volatages/capacitance, or better don't even buy them! 5 Ohm is much to low!
better go with Jeti 5,5mm (36 Ohm) or Jeti 8mm (30 Ohm) for higher current. Theire smd resistors should withstand precharge well at higher volts and even don't get warm.
How about using a POST-charge resistor? When you shut off the pack a high ohm resistor stays connected. I just tried a 1000 ohm and it was too small. maybe 5000 or 10k would do it. keeps the caps charged, but could NOT drain the pack even if shorted(for a VERY LONG time.)
My bike has been apart for a month and the caps were 14.8v down from 37. Took 2 seconds for the 1000 ohm to bring it to 37. So if i decide to turn off the pack for storage safety, ....
I use a master power switch with a KEY. This is for anti-theft, and a no spark resistor on my mbike built in 2006. Controller still has charged caps! 7 yrs ! no sparks! Walmart had master power key switch for $10 in auto dept. I got it on the web for $4.
