Constant short circuiting of batteries to controller. SPARKZ

[ebike_rocket]

Hi everyone,

I'm working on my second ebike build. It's a 36 volt system, 500 watts. I have three SLA batteries rated at 12 volts, 17AH each wired in series, with positives going to negatives. I have an ebay bought conversion kit. The kit is rated at 36 volts, and again 500 watts. When I first installed the kit, the batteries were undercharged, and I didn't get any sparkz shorting out between the connector, which is a computer cable wired to a two slot connector into the controller. But, now, after fully recharging my batteries with a smart charger, every time I connect the computer cable, it shorts out, leaving carbon on the make end on the negative side, and melting rubber and plastic, and probably leaving carbon on the female side. The fuse which is a 30 amp fuse, is located on the negative cable. I used a multimeter to check the voltage of the total bank, and it's 38 volts.

What can I do to stop the shorting out of the cables? I thought at first it was a short circuit in the cable, but checking the cables show no such thing. I find it interesting that the short constantly happens at the computer cable attachment. The computer cable attachment is the same thing that you'd find in the back of your computer, a three prong connection. There's no ground wire on the system, and like I said, I didn't have this problem when the battery bank was under charged.
Is there a safety circuit I can construct to ensure the voltages are always at 36 volts, is it because the batteries show up as 38 and the system is 36, or am I missing something?

 

[amberwolf]

Take a look around the forum for "precharge" circuits, and use one of those.

Also, 38V for 3x 12V SLA is not fully charged; usually a minimum of 13.1 to 13.6V is fully charged for a 12V SLA.

 

[Rassy]

Welcome to the forum Rocket.

On my first kit, a WE 36V brushed setup, they used phono plugs for the charger. Those plugs were not made for high voltage and would easily cross short when plugging in the charger, resulting in burns on the plugs. My guess is that the connector you are using is not up to the task and when the capacitor tries to fill a short occurs. While a pre-charger for the capacitor might solve the problem, I would also consider using a heavier duty connector.

Also, instead of using a pre-charger, I have been using a DC breaker as an on/off switch. The spark still occurs within the breaker, but does not damage it, (and you can't see it, etc.) These breakers are commonly used on the larger electric scooters and available from the scooter parts places.

 

[ZOMGVTEK]

On that low voltage you shouldn't need a precharge. Generally the low end systems use a 15A IEC, which is very low quality chinese garbage. Replace the power connectors on the controller and battery with something like a 45A Anderson Power Pole thats designed to deal with arcs.

Also, nothing is actually shorting, correct? You are simply using this term to describe the high inrush current when you connect your fully charged pack to the controller? As long as the bike works after the IEC is plugged in, and no fuses are blown, its fine. Generally the fuse holders that come with those kits are trash, and its not a bad idea to replace or remove that, depending on how your setup and use.

 

[ebike_rocket]

Thanks for the welcome, folks.

ZOMGVTEK - Well, I don't think anything is shorting. What I'm observing is a large spark, or a spark sound, and then a good amount of smoke when I plug in the thick computer cable male and female ends together to connect the battery bank into the controller. I've now terminated both cables that I have available, so I think I'm going to have to find an alternative to manual plugging and pulling... Anyway, the negative terminus is the one that sparks, and it results in full carbonization of the male and female ends, resulting in no current flow whatsoever. Just in case, I did a volt meter check of the load in the controller cable that connects to the computer cable that connects (I know, cheap chinese material is convoluted. I'm just starting in on this stuff), to the battery bank. There's a load resistance of about 30-50 k ohms. Nothing seems unusual, and it seems equivalent to my 48 volt system controller load.

Rassy - DC breaker. Got any particular websites where I can order one of those?

Also, I was thinking of wiring up a relay to take care of the problem, like and auto relay with a switch, or to just get a switch, but Ihave a feeling the switch, no matter how heavy duty, is gonna burn out.

 

[sangesf]

I bet ya a million dollars, he's got the polarity reversed!
(Notice he says the "fuse is on the 'negative side'". Normally fuses are on the positive side)

 

[ebike_rocket]

I bet ya a million dollars, he's got the polarity reversed!
(Notice he says the "fuse is on the 'negative side'". Normally fuses are on the positive side)

Actually, that's how the kit came, with the fuse box on the black cable (negative) terminal.

Dang, if that's the case, this really is a badly put together kit...

 

[ZOMGVTEK]

I'm not really clear on whats going on. You say the plug sparks and smokes a bit. Does the bike work? Where the fuse is means very little. If its just sparking a bit on the connection, but otherwise works, replace the plug with something that isn't junk. This is sparking and smoking every time you plug it in? Reversed polarity should let some magic smoke out of the controller, or blow the fuse/wires. At the very least the controller would blow up silently, but then it should no longer spark when you reconnect the battery. If its sparking every time, its probably OK there, just a bad connection.

If the bike never worked yet, it wouldn't be out of the question that the polarity is reversed. The + is going to a red wire, and the - to a black? I don't know much about your setup, but I would assume reversed polarity isn't the issue.

 

[ebike_rocket]

I'm not really clear on whats going on. You say the plug sparks and smokes a bit. Does the bike work? Where the fuse is means very little. If its just sparking a bit on the connection, but otherwise works, replace the plug with something that isn't junk. This is sparking and smoking every time you plug it in? Reversed polarity should let some magic smoke out of the controller, or blow the fuse/wires. At the very least the controller would blow up silently, but then it should no longer spark when you reconnect the battery. If its sparking every time, its probably OK there, just a bad connection.

If the bike never worked yet, it wouldn't be out of the question that the polarity is reversed. The + is going to a red wire, and the - to a black? I don't know much about your setup, but I would assume reversed polarity isn't the issue.

No, the bike doesn't work after the plug is in. I'm pretty sure it's because of the plug connector destruction when I last tried to plug the plugs together. I've never observed the controller sparking. Also the fuses haven't blown, but they're 30 amp fuses, which is equipped on the black wire (and which the manual designated as the negative terminal wire). The bike worked earlier with the same configuration, but when it was at a lower voltage (one of the cells was bad).

I'm pretty sure that nothing was reversed at this point based on what you're saying.

So, I'm going with these recommendations, get a Anderson connector set from Mouser.com, and a DC breaker from a scooter supply place that can handle 40 amps. This sound about the right approach? Also, what qauge wire do you folks usually use for wiring batteries and in general with this kind of amperage? aka 36-72 volts. I'm looking at getting a supply, because I have another light electric vehicle idea I want to get to work on with my 48 volt setup.

 

[ZOMGVTEK]

What you really need to do is ensure the controller is getting power. A way to measure power is really great for troubleshooting problems and such. You can hardwire the controller to the battery temporarily and see if that does anything. Since you had it working before, but on a lower voltage, I assume the rest of the setup is good to go and probably works? The controller is rated for the voltage you are putting at it? The throttle is good, the halls are connected? Are there any lights inside the controller? Can you run your old battery and see if it runs on that lower voltage?

I would run a meter between the controller and battery, and see if its taking any power. If its reading something like .01-.1A at idle, the controller is probably on. If its reading 0.00A, something is wrong. If the controller IS on, you need to find out why the motor wont spin. If the controller isn't on, you need to look into what you did before that caused it to no longer work. DC breakers aren't a bad idea, but its not really critical in your setup. Quality connectors always are. I would order 10 pairs of them from eBay or something, since it tends to be cheaper. You really should replace all cheap connectors that have any real power going through them. This would be the phase wires going to the motor, and the power coming from the battery to the controller. You should be able to change your charger plug to a power pole as well, but I don't know what your setup looks like or how you charge.

 

[Rassy]

Rassy - DC breaker. Got any particular websites where I can order one of those?

This is one I've used. In about 4 years of almost daily use I've never had one of these fail yet. I don't depend on them as fuse substitutes, but just as a good on/off switch.

http://www.werelectrified.com/Bike-Electrified-Breaker-Switch-p/breaker%20switch.htm

 

[ebike_rocket]

Say,

Would a car stereo amp, 40 amp rated work as well? It's got waterproof features on it.

 

[dnmun]

i don't understand your problem. do you really have a short circuit or is the spark from plugging in the controller? you can leave the large red wire and black wire connected to the controller all the time and then put your switch on the small red wire that carries the controller circuit current. no need for big switches or fuses at all. if it is just charging up of the controller caps that is creating the spark.

 

[ebike_rocket]

i don't understand your problem. do you really have a short circuit or is the spark from plugging in the controller? you can leave the large red wire and black wire connected to the controller all the time and then put your switch on the small red wire that carries the controller circuit current. no need for big switches or fuses at all. if it is just charging up of the controller caps that is creating the spark.

It's from plugging in the battery bank cable into the cable the leads to the controller. The spark happens at the terminal plugs joining the negative wires (which is attached to the negative terminus of the serially wired battery bank). Incidentally, the fuse box was factory installed on the negative wire.

 

[dnmun]

so you really don't have problem. no short like the title said.......

 

[ebike_rocket]

so you really don't have problem. no short like the title said.......

Well, now that I understand it better after talking with you folks, yes it's not a short.

But the bike doesn't work because the spark completely melts/carbonizes the contact.

 

[Solcar]

I might be inclined to splice into the main power wires with lighter wires on each side of the connector and add another connector that can be less heavy duty as well. Place a power resistor in series with the +lead going to the smaller connector. It will let the bulk capacitors charge up more slowly when you plug together the small connector first. After a few seconds the big connector gets plugged in. Actually, just normal hand movement time is a long enough wait if the resistor value is well chosen.

 

[sangesf]

so you really don't have problem. no short like the title said.......

Well, now that I understand it better after talking with you folks, yes it's not a short.

But the bike doesn't work because the spark completely melts/carbonizes the contact.

They must be some TINY connectors...
I've NEVER seen a "plug in spark" bother the PC type connectors...
I really think you have the polarity backwards...

Have you checked the polarity yet? If not, do that NOW!

 

[dogman dan]

Yes, polarity could be backwards. So get a voltmeter and learn to check polarity with it. It sounds like just the normal spark when a controller is plugged in to me. Just the battery filling the capacitors in the controller. Some kits do come with stuff crummy enough to melt on 36v.

Once you get a good solid connection from battery to controller, with polarity right, we can start hunting for the other crummy connector, that is the real reason the bike doesn't run. Lots of times, a new kit won't work, and it's because a contact in some other connector is backed out of the plug housing. There's a lot of wires.

 

[dnmun]

he has a voltmeter. but no pictures, just a long running description of this computer wire. why people don't just hard wire and leave all the plugs out is silly, imo. adding a fuse is just more ways to lose power too. solder it all up with 12G wire and put the controller circuit current on a switch to keep it from draining the pack.

 

[vanilla ice]

Something is very wrong with your setup. A small spark is normal but not a huge connector eating spark. That only happens when something is screwy.

Like AW says, your 12v batteries should be like 13.6 volts each when they are charged up. It is normal for them to be over 12 volts.

 

[parabellum]

ebike_rocket. You should get this setup to run first and then start any thinking about pre charge or switches. I hate to think that it is already Game Over. Few pictures or short video can be a helper/saver, if there still something to save.

 

[ebike_rocket]

It's working! It's working. I followed some recommendations, and it has an Anderson connector for the battery pack to the cable connecting to the controller. I also put an inline escooter circuit breaker. I still get a spark, but the Anderson plugs seem to be able to take it.

That said, I'm not fond of using Anderson plugs. I have to TIE them together to keep them hooked up! Is there a more elegant method to do this? And what kind of switch can handle that voltage and current, cause I don't want to have to plug it in every time I want to take the bike out. It'd be nice to plug it in and switch it off.

Thanks for the help by the way to every one!

Now, that said, I DID, just out of curiousity, reverse the polarity and connect it to my 48 volt controller, with, ahhh, spectacular results. I now know not to do that again.
So, if anyone has any info on how to repair a 48 volt controller, I'm all eyes.

But 36Volt 500 watt proto 2 is up and running!

 

[amberwolf]

If your controller has a thin red wire that has to be hooked up to power to turn on the controller, then put a switch on that wire, because it can be *any* switch.

Just make sure to always keep the battery on the charger when not in use, if usage is irregular, or else disconnect the andersons if it will not be used for a few days. If it's used and recharged every day, it will not drain enough power to worry about.

 

[sangesf]

It's working! It's working. I followed some recommendations, and it has an Anderson connector for the battery pack to the cable connecting to the controller. I also put an inline escooter circuit breaker. I still get a spark, but the Anderson plugs seem to be able to take it.

That said, I'm not fond of using Anderson plugs. I have to TIE them together to keep them hooked up! Is there a more elegant method to do this? And what kind of switch can handle that voltage and current, cause I don't want to have to plug it in every time I want to take the bike out. It'd be nice to plug it in and switch it off.

Thanks for the help by the way to every one!

Now, that said, I DID, just out of curiousity, reverse the polarity and connect it to my 48 volt controller, with, ahhh, spectacular results. I now know not to do that again.
So, if anyone has any info on how to repair a 48 volt controller, I'm all eyes.

But 36Volt 500 watt proto 2 is up and running!

I told you to CHECK polarity, NOT hook up...
Oh my, controller is fried!