Balance charger throws error message

[Harold in CR]

I have an Imax Eco six balance charger. Worked for approximately 3 minutes, then quit. It would boot up but only button that worked was the Battery Type choose left side of the charger location. So, being a long ways from Hobby King, I opened it up. On the back side of the circuit board, I found a slight charred section. Took the spy glass and found a tiny sliver of solder had touched the trace from a resistor leg solder point, possibly a ½Watt resistor. I'm not even close to being an electronics tech.

I scraped very carefully with a box cutter knife blade tip, and cleaned the area with a med soft toothbrush. Got the area cleaned as far as I could tell. While the case was open, I checked the touch pad button area, and found that when the charger was assembled, the ribbon from the touch pad to the circuit board had been pinched under a plastic stand off leg that supports the cover from flexing very much, and the ribbon has a burned spot, probably why that burned area on the back side of the board.

Before reassembly, I hooked the charger up to the power source and it booted up AND, I could change the battery settings.

Disconnected and went to the 5S pack of Leaf batteries I am trying to get balanced. Set the charger up for 1.5A and 5S 18.8V and started up the charger. It started working. After 10 seconds, it cut off with the Break Down error message on the screen.

I reset the Amps to 1.0 and restarted the charger. Same thing, 10 seconds and cuts off with the same error message. Reset it 1 more time, at .05A and started it up. 10 seconds and it cuts out, same message.

Can someone offer a little advice on what I might check, or even, what might be happening ?? Is it possible that resistor is not functioning correctly ?? I have another same type charger that I connected reverse polarity, that doesn't work, so, might be able to scrounge parts off of that, MAYBE.

I can take a couple photos, but, there is nothing that looks suspicious at this time ??

Thanks for any advice

Harold

 

[John in CR]

I doubt that little charger can balance those 30ah cells. That would take horrendously long anyway. Does it still work at all, ie charge on the +/- primary outputs? If so, then bulk charge first, but not at the max rate of the charger, and keep a little fan blowing on it. Once they get to 4.1 to 4.15V, then charge each individually using the li/lo setting to full charge. Once you top each off by single cell charging then they're balanced.

If the cells aren't permanently in series, then you can disconnect them and connect in parallel as long as the voltages aren't out too much. That will balance them, and you can single cell charge them all together at the same time to bring them up to a perfect balanced top of charge. On the next set you hack into that's the way to go. Any that are out by more than a few tenths of a volt, simply single cell charge them to get them closer to the others before paralleling them. It's good to do all of your cells at once with this approach. Then you can evaluate self discharge of those you don't use for a while. At least get them all in perfect balance that way first. Then you're assembling perfectly balanced cells, so you can just bulk charge them at the end checking for balance occasionally as they start to exceed 4V. Pay attention to any rising in voltage faster than the others, since those cells would be lower in capacity.

The only time I ever use the balance charge function of my RC chargers is with a single RC lipo pack that's already close to balance. Even when they are just 0.02V out it still takes a while. When a cell or 2 on my bikes get out of whack by 0.03 or so after bulk charging, I simply connect to the low cells individually and charge them to full charge by single cell charging.

If the cells are already connected in series, worst case you can charge them individually. Hopefully the charger still works on the main outputs and just the balance connection part is gone. If so you'll be just as well off, because the charge a little then bleed off a little from the high cells is a ridiculous way to balance charge, but that's exactly what those things do.

What are you using for the supply to the charger? I always use a 12V battery, and if it's going to require some ah's, then I connect my 12v lead charger to the battery at the same time so the battery acts as a buffer. I tried an RC charger connected directly to the car battery charger once and neither of the chargers liked that.

Don't forget to keep that RC charger cool. I put something under both sides of mine so air flows over the top and bottom of the case. Just like our motors and controllers, the cooler the better for chargers. I've used fans blowing on my bulk chargers too on unusually warm days where the charger's fan output feels warmer than usual.

Sorry I didn't understand what you were doing in terms of charging that set of Leaf cells. I would have told you then not to bother with the balance charge function and just bulk charge and then single cell charge each to balance. You would have finished long ago. Instead I was trying to remember controller wire colors from over a year ago.

John (with fingers crossed that the RC charger still works on the primary output)

 

[Harold in CR]

Charger cuts out no matter what settings I put it on. It goes 10 seconds, EVERY time, then throws that error.

The cells we bought together I am not concerned about. They are all very close to 3.89 per cell. I have balance leads to all the cells, so I can use a cell tester 7 to check capacity and each cell voltage. Each pack is 5 cells. I had to wait for the extra module to get shipped down, after the rat incident. That's what is taking the time. Those cells are all right at 3.73. I had to change out 2 packs, so, that's what I single cell charged first, after rebuilding the packs.

For single cells, I hook a 6V 500ma phone charger right to the balance leads for the cell needing a boost. That works fine for me.

I have some access to most cells as singles, by carefully moving the connecting leads to one side. They are all connected as 20s at 84V. Then, I can clip jumper leads on the connections and connect the charger at 3.7 Lipo and 1.5A settings. Takes about 6 hours to get the cell up to match the rest. Then, I do the balance on the whole 5 cell pack at 2A. I still had lots of little things to do to the bike, so, I'm working on it as I charge. I also set the charger for 3 hour runs, and run one round after supper, from 6:30 or so, checking a couple times during that last run, before going to sleep.

I use a 500W computer power supply for the charger power leads. It does a fine job as far as I can tell. I have an old analog car battery charger that I have used, charging a bad car battery connected to the RC charger. That buffers the car charger. You might have a newer electronic pulse car charger that causes problems with the RC charger ?

I have 2 packs sitting at 20.43 V and 89% capacity, according to the cell meter 7. I bought 2 of them, but, of course one was DOA. The chargers, I bought 2 new ones to go with the one you gave me, so I could do 2-3 packs at a time, but, I old timered and connected it reverse polarity. It ticked and doesn't work. I asked for some coaching on the E-S but got no responses.

I need to verify the regen, because I need to use that for the downhill run at the beginning of my town runs. So, I imagine about 85% when leaving the house should be close. I will definitely check closer to be sure. I need to figure out how to use an Amp function to check the timing setting on the motor/controller, to be sure it is correct. All I have is a few mulitmeters with the amp part burned up. Not about to do that with the newer-better meter I have now.

Tomorrow late in the day, I may be able to hook up my paralleled 8 laptop chargers to do a whole pack charge, once I get the cells all reading very close to each other. These little eco 6's work pretty nice when a person is not in a big hurry. Also gives me time to try to think about screwing things up, before I get into trouble.

The frame was made to fit 6 packs of 21S 3P of A123 26650's. just worked out that the Leaf cells would just fit in there, so, I did them instead of the A123's.

About that bad touch pad that has the burned connecting ribbon. They actually ran the screw through that ribbon, when they closed up the case. The posts in there are where the screws go to hold the case closed.

Thanks John. Harold

 

[John in CR]

You live at the top of a hill, so you can't regen down, you fully charge your pack before leaving instead. I don't think that controller has regen anyway. To check, run the motor at speed and short the ebrake wires. If it has regen it will be obvious due to the greatly reduced rpm immediately. Plan on mechanical brakes to get down the hill, and a lot of, or mostly, rear brake getting down the rocky dirt roads. It's so easy to go down with too much front brake in loose rocks.

 

[Harold in CR]

You live at the top of a hill, so you can't regen down, you fully charge your pack before leaving instead.

I discussed this with you from the very beginning. We had agreed this is the way I have to do this. ??

Do you have a regen controller I can swap back to you ?? All this time waiting and planning and I still don't have what I need. I just need to get a moto or moped front brake cable to activate the drum brake on the front.

Much testing today, before it comes off the work bench.

 

[John in CR]

Just because regen inherently is anti-lock braking doesn't mean the wheel can't slide. For maximum range leaving the house with the battery is full is best, because the regen recovery of the decent to the main road will vary. No matter what you absolutely must have good mechanical brakes front and rear, so the difference is just wear and maintenance. I've got an extra set of the rear brake shoes, so that's not a concern. You have to go slow, and super slow on the rocky dirt section, so regen won't provide great force.

By front drum brake you mean for a motorcycle and no one of those little bike drum brakes, right? If it's a bicycle drum brake, maybe it's enough since you have the scooter rear drum too, but be cautious.

My view on regen and steep hills has evolved, especially after having to walk my bike a few kilometers down an extremely steep road. Something I wasn't considering before is the efficiency of regen. As speed gets lower I'm sure efficiency of regen gets lower too, just like during acceleration. That means whatever braking work is done by regen the % of it turning into heat in the wiring and controller gets higher as you go slower. I've never had a heat failure from regen, but all of my prolonged regen use going down long hills has been with low force regen.

The time I had to walk the bike down, my mechanical brakes were insufficient and I was extremely concerned about brake fade. Maybe regen would have kept the speed low enough for the very curvy road, but I was too chicken to find out, since it did little at the safe speed I used for the few hundred meters. I was barely able to get the bike stopped. My other example that highlights my concern is toward the end of an extremely hard ride my motor had warmed up to 100°C. The ride home from that point was all downhill, a modest hill I ride frequently and coming down regen keeps speed in check just fine with braking between 1/3 and 1/2 of the way down as needed with speeds of 40ish mph. Since I was paying attention to temps on that ride, I was expecting my ventilated motor to cool significantly by the time I got home, especially since I was alternating regen between the 2 controllers. The temp stayed exactly the same until I got to flat road and continued past my house to see how quickly the motor cooled with moderate riding on the flats.

Does regen create dangerous heat as some have claimed? I don't know at this point, but I hate for you to be the guinea pig to find out the hard way.

Your steep rocky section where you'll rely a lot on the rear brake is quite short, and then the paved road down to the 2 lane highway will be front brake mostly, so I'm not worried about extreme heat to the motor shell and magnets from the motor's drum brake. With mechanical braking on the way down the stator should still be nice and cool, so the shell should cool quickly.

With regen braking, you'd have it switched to low speed for more braking force, and you'd ride the regen brake almost all the way down and add mechanical braking as needed. I believe that low will give regen better efficiency at a given speed just like it does under power going up hill. Will it lead to a lot of motor heat? I don't know, but I'm slightly more concerned about a moderate power controller being up to the task. Where regen is a big safety factor is coming down hills on an ebike with bicycle brakes at speeds well above what you'll be at, and bicycle brakes can fade very quickly using them to keep speed in check and then have a need to brake hard. That's because regen works great for keeping speed down on modest grades, so the mechanical brakes are fresh and cool for hard braking. Your paved hill is steep enough, curvy enough, and a far less than ideal surface, that you'll need to keep speeds way down, which is where regen doesn't work as well, and mechanical brakes don't have to dissipate energy as quickly, so they're less likely to fade.

It's an interesting topic to explore, but I'd have to do some serious experimenting before being able to say "yeah, let regen do as much work as possible on the way down your hill." like I used to think up until late last year.

 

[Harold in CR]

Does regen create dangerous heat as some have claimed? I don't know at this point, but I hate for you to be the guinea pig to find out the hard way.

Exactly my point. The heat from coasting HAS to go someplace,

By front drum brake you mean for a motorcycle and no one of those little bike drum brakes, right?

Moped front drum brake. Have a Yamahopper 14" front wheel with drum brake assembly. Also bought a spare set of shoes for that brake.

With regen braking, you'd have it switched to low speed for more braking force, and you'd ride the regen brake almost all the way down and add mechanical braking as needed. I believe that low will give regen better efficiency at a given speed just like it does under power going up hill.

My thoughts exactly. Will find out soon enough. Have 3 packs sitting at 87% charge and 20.43V. Got the whole pack charger out, but, there is something screwy going on with the 4th pack. 1 cell goes higher and one cell goes lower ?? Other 3 cells are at 3.965-66 Have to investigate. Right now, I'm equalizing those 2 cells. Then, go back to balance mode and see what happens. Might have to remove the pack and see if something is slightly shorted between 2 cells. When I do a VOM Voltage check on the balance plug contacts, they all read close enough. Charger and cell tester both indicate one cell at 3.76 and one at 4.17. ??

Thanks, John Harold

 

[John in CR]

Does regen create dangerous heat as some have claimed? I don't know at this point, but I hate for you to be the guinea pig to find out the hard way.

Exactly my point. The heat from coasting HAS to go someplace

Not sure what you mean "heat from coasting". When coasting the energy goes back to the wind depending on speed, some to friction in tires and bearings, and a negligible amount in the motor from still having some iron losses with the motor turning but not powered.

If you're talking about regen, the work of braking either goes back into the battery or heat in the motor, wires, and controller. Very low efficiency at very low speeds may be why regen turns off below certain speeds, and the low pole count of these motors makes that cutoff at higher rpm.

One interesting thing is how well the plug braking works on some controllers I have. I just have to be careful not to ride the plug braking button from high speed all the way down. I did pop a controller doing that, but then proceeded to use them pretty much like I use regen for a year and nothing got any hotter than now. I wouldn't use it in your situation though, except on just the rocky dirt part down to the pulperia. I feels nicer than regen because the braking goes all the way to zero and the taper of the braking force is flatter and more natural.

 

[Harold in CR]

If you're talking about regen, the work of braking either goes back into the battery or heat in the motor, wires, and controller.

Exactly what I was referring to, windings and magnets heating up excessively, if the regen is not capable with this controller.

"plug braking", something I have to research more.

Have a mystery with the last 5 cell pack. Celltester says one cell is down to 3.0v and one is up to 4.75v. Charger kicks off saying cell V is too high. BUT, I use the VOM on the contacts of the balance connector, unplugged from the charger, and 4 cells are 3.95v and one is 3.75v. ??? Can't see 3.0v no matter how I use the VOM.

Tomorrow, pull that pack and check individual cells.

 

[John in CR]

If you're talking about regen, the work of braking either goes back into the battery or heat in the motor, wires, and controller.

Exactly what I was referring to, windings and magnets heating up excessively, if the regen is not capable with this controller.

You lost me. If there isn't regen, then there isn't motor heating going downhill. Coasting makes so little heat you can ignore it. Low or hi going downhill will make 0 difference without regen. It will be nothing like descending in a car in first vs second. The cogging resistance is there, but that reaches a plateau pretty quickly and isn't much at all. Maybe you're thinking of when you were riding my cargo bike. It's set for slip charge regen, so you let off the throttle and regen braking starts automatically.

Regarding plug braking, you don't want to do that down your 4.5 kilometer hill, because it dissipates heat only in the wires. While you'd put much of the heat in higher resistance wires outside of the motor to sink to the frame or an added piece of metal, heat may still build up in the motor. You don't want a controller that does it either, so no 18fet Greentimes for you.

You have drum brakes front and back made for scooters and mopeds that weigh 200-300lbs, and you really don't want to try to top your battery off with an unknown regen charge to start every ride. Plus batteries can't take a CC charge near the top of their SOC. They want current tapering off applying a constant voltage. Regen won't do that though, so what will happen is that reverse sag during regen will push battery voltage well above your top of charge target voltage. That's no good for batteries. Plus you want to be at home for top of charge so you can check balance and deal with issues there.

No, the more I think about it, you're the rare case who shouldn't have regen, because you live at the top of a hill. There's no pleasant riding place up there, so what would you do if you accidentally fully charged your battery? It's begging for a catastrophic failure compared to the very minor failures you've encountered so far, though I guess a psychotic rat snacking on your pouch batteries to get his lithium fix is pretty catastrophic. :lol:

Another thing that sucks is that you have no decent road for testing, because flat or uphill is the proper test ride route, so it's easy to get home. Plan ahead and start making nice with a neighbor with a pickup truck, because if you don't have it lined up ahead of time sure as sh1t you'll have a problem at the bottom of the hill. It's just like the only way to prevent rain is by carrying an umbrella, and pushing it up that hill would be a nightmare.

Oh, just a reminder, do not try to ride without at least one for on the peg or pedal. You have far less control of the bike with both feet down. That's for full stops only. Feet don't work like training wheels as tempting as that might be.

 

[Harold in CR]

so you let off the throttle and regen braking starts automatically

====Exactly.

I figure I can take numerous readings as I go down hill WITH regen, to find out at what CAPACITY the pack has, both, before starting out, AND, at different distances going down hill. I can do many testes to see what is near enough for regen to put energy back into the pack.

Going to Monterrey, I have some decent hills to cgo up and down, so, putting anything into the pack will help to NOT have to charge in town. That route will be 90% of what I will be riding. I'm confident I can get a comfortable set up for long distances to Monterrey. Up here, on top, it will be less than 3Km trips. The motor, with the controller disconnected, DOES have slight cogging. I just can't see a reason to not use it.

We have an old cellphone, and a neighbor with a pickup, so, I'm pretty set for that.

Still can't find the problem with this one pack. Charge a single cell and things seem OK. Get close enough to the rest to try balance charge, and, the one cell goes lower and the next goes higher ?? Still, the VOM says things are close enough to be balancing ??
Guess I need a 60V controller so I can, at least ride the damn thing.

 

[John in CR]

Cogging can't be "used" for anything. It's like saying you're going to "use" the friction of your rolling tires or friction in your bearings. The forces and energy related to cogging can never go back into your battery whether you have regen or not. It's simply parasitic loss.

Do you have the CA that I gave you working? You really do need that, because having that climb to get home means you have to know capacity and usage and with pretty good accuracy what is required to climb that hill.

Simply let go of ideas about regen for now. Even if you had it, you couldn't use it on your initial decent. Sure you'd get some benefit from it on the later hills, but it's likely to be less recovery than you think. While I've gotten in excess of 20% as a regen %, that was always on local rides on good streets I know intimately with very low force regen. I was familiar enough with the rig and specific roads that I understood the speeds and distances to let off the throttle and start regen with hardly any use of mechanical brakes the entire ride. You won't be able to duplicate that or even come close. With your riding in a rural area my guess would be around 5%, because you will be using mechanical brakes...a lot. Your battery reserve should be at least 4-6 times that, so let go of the ideas about regen until you're buying a new controller for backup. For maximum range, you fully charge your battery before leaving the house.

Focus on getting your battery right, and once you think it's right test it with the bike under load. It's sounds like you have a cold solder joint or something. I have any clue what you've done with those modules, since at one point you were talking about even removing the plastic dividers stuck pretty firmly on the cells, and that kind of stuff or bending or changing the shape or surface of the cells in any way disturbs their fine delicate layers inside reducing cell life and capacity. Proper compression flat to the cell face is a must too. What this means is that once your pack is working and connections proven, then you have to do a capacity test. You've gotta know what the capacity of the worst cell is, because that's the capacity of your pack.

Since you can't just call home and say "Honey, I ran out of juice on my bike. Can you hop in the truck and come rescue me? Out in the boonies I doubt you can call a taxi, and I'm not sure there's enough traffic to count on a truck passing by and paying him to be your flat bed tow truck (I've done that before). Unless you have a friends at the bottom of the hill in both directions or be able to count on a recharge, paid or free, then the cost of running out of juice is so high that you absolutely must know your pack and energy requirements of getting home, and maintain a conservative max DOD.

Based on statements like "these cells are charged to 89%" just by looking at voltage tells me you're headed for trouble. You can't know SOC looking at voltage unless your pack is fully charged. A 50% DOD is somewhere around nominal voltage, but which voltage? Voltage varies with both load and SOC. I'd learn my pack's true capacity, and stop and check at rest voltages at say each 5ah during the capacity discharge test. That will help you start developing a "feel", so you can let off the throttle and glance at voltage, and know where you stand. Then a properly calibrated CA will be icing on the cake.

Also, you'll really need to carry a charger with you, so as soon as you're up and running and know that the ebike thing is going to work for you, then order an extra charger or 2. Without the ability to recharge, an ebike is dead in the water, and if you're frequently traveling with your charger then failure risk is substantial, not to mention the significant risk due to dirty electricity out there.

Get that battery going, and if that cell is dead just clip it's connection and by-pass it with a thick wire and use 19s and get that think rolling.

 

[Harold in CR]

Battery pack is now repaired. I use a Celltester 7 that shows capacity in % of the 5 cell packs and each cell in that pack. Is it dead accurate ?? probably not, but, if it's consistant, for now, it will do what I need.

Should have the battery installed later today, and MAYBE get a ride.

I have been VERY careful with handling the individual cells. They have always been picked up on edge and laid flat and weighted when I'm not working on them. They will be on edge in the fiberglass boxes I made for each pack, with carpet underlayment on the bottom of each box to cushion the cells. Then, I will have compression on each pack.

I can never explain things so people understand me, so, I will just do what I know is safe and not damaging the cells.

The cycle analyst is extremely fine soldering needed and there are several legs on each chip to be soldered, without getting cold joints. When I feel steady enough, I will try to change out those 2 chips. I can do hammering and then fine soldering in the same day. Body gets used to one thing and doesn't change back quickly.

 

[amberwolf]

Does regen create dangerous heat as some have claimed? I don't know at this point, but I hate for you to be the guinea pig to find out the hard way.

I don't remember who it was, but someone on ES actually overheated a motor and damaged something (insulation? Halls? I forget) a couple years or so ago, braking all the way down a mountain path/road.


It depends on how the controller creates the regen voltage as to how hot the motor might get during braking vs motor use: Since typically regen isn't putting more than a couple hundred watts back into the battery for more than a few seconds, this doesn't usually matter.

If you're doing it down a long hill, htough, it could, especially if you're going to need to hit the motor hard with accleration currents after you're down the hill and have to ride around in traffic with stops/starts, and/or climb the (a) hill again before there's time for the motor to cool.

If the controller is creating regen voltage by simply letting the motor's overspeed flow back into the battery, then it should just the wattage going back in that you see on teh meter that is being procesed in the motor, and that won't be a lot.

But if hte controller is doing it by shorting the windings over and over to get pulses of higher voltage when it releases the short, then during the shorts it's getting some very very high currents, albeit for very short periods. You'd have to actually be measuring at the phases to tell what those currents are.

If it's shorting out the FETs completely (plug braking) then both controller and mtoro could get pretty hot pretty quick, even assuming it's limiting the shorted current to the max the controller could normally do for acceleration. I expect most of the heat would be in the controller, though.


Actual heating amounts you'd have to measure for your controller/motor/hill, though.

Low or hi going downhill will make 0 difference without regen.

Unless your speed is so great that the motor is generating a voltage much higher than your battery, in which case it could be flowing backward thru the FETs in teh controller (thru body diodes) into the pack, and that will create some heat in the controller itself (maybe a little in the motor but mostly the controller).

Feet don't work like training wheels as tempting as that might be.

Well, maybe you could wear rollerblades? :lol:

(no, I wouldn't wanna try that either!)

 

[John in CR]

AW,

I think you're leaving out efficiency. Just like when under power, efficiency of regen must change with rpm too.

Going downhill without regen can't do anything to create problematic heat in our hubmotors. The overspeed stuff sounds like urban myth, because I've gone down long hills at high rates of speed both just coasting, and with the throttle pegged to WOT due to slip charge regen activation. I've done it lots of times with no significant heating noted or blown controllers when I was still trying to stretch the limits of cheap controllers with no regen.

 

[amberwolf]

I think you're leaving out efficiency. Just like when under power, efficiency of regen must change with rpm too.

That's true--I forgot about that.

Going downhill without regen can't do anything to create problematic heat in our hubmotors. The overspeed stuff sounds like urban myth, because I've gone down long hills at high rates of speed both just coasting, and with the throttle pegged to WOT due to slip charge regen activation. I've done it lots of times with no significant heating noted or blown controllers when I was still trying to stretch the limits of cheap controllers with no regen.

Well, it depends on your controller and motor combination, I guess, and your battery voltage? I am not really sure.

I've not much experience with it, only one time riding The Velcro Eclipse down a steep hill and letting it coast at whatever speed it could reach without braking (only mechanicals on that bike, I don't think I ever set regen up on it). I don't remember the speed I reached, but it was faster than I could get to with the old 36V NiMH pack I was using with it, on the 9C 2807 in 26" wheel. At some point I felt more vibration from the motor, and a sound as if it were regen braking, but I wasn't. The controller was warm after I reached the bottom, but shouldn't have been. So I assumed (yeah, I know) that this was what I'd read mentioned regarding that type of "overspeed generation". I only had the WattsUp on it so I didn't get any reverse current readings, and don't know if it actually was feeding power back into the pack.


I can't find the post in the TVE thread, so I guess I didn't post about that ride (actually it looks like I didn't post about hardly anything I did with it in it's short life). I didn't use the bike much beyond testing it out, cuz I much prefer CB2's riding position/etc., and it was only meant ot be a spare bike, so I never repeated the experiment. I sitl lhave the basic bike but all the stuff has been redistributed to other bikes and/or broken....

I should repeat the experiment using CB2 itself down that 7th street on North Mountain, cuz that's the steepest in this part of town. When I first built CB2 before it had cargo pods and motors, I tested it down that hill and almost broke 40MPH down it. Was fun, but scary with all the traffic around me. One little oops and SPLAT could've happened. :lol: Maybe late late at night with no one around? (it's usually a very busy street all day) Will have to wait till I have a better front tire anyway.


Anyway, I guess it's just way-OT speculation at this point.

 

[John in CR]

How is there going to be reverse current, since the switches are off? If they weren't then that would put the phases in a short condition and plug braking would result. Justin says the parasitic iron losses we feel as cogging taper to a fixed amount, and we feel that when we pedal only with a DD motor. We also feel how little the force is by the way we can coast for pretty long distances. Your vibration seems more likely to be from an out of balance wheel, but I guess anything is possible. Even downhill I've never gone faster than my no load speed, and if Harold goes even close to his no-load down those roads he'll kill himself. If it's something I've not seen, then I need a plausible explanation. You know a lot more about electronics, so even if there is high voltage, how is current going to flow through mosfets that are turned off?

edit- please don't go flying downhill on some busy street on your low speed ebikes to find out.

 

[amberwolf]

How is there going to be reverse current, since the switches are off?
<snip>
You know a lot more about electronics, so even if there is high voltage, how is current going to flow through mosfets that are turned off?

I suppose it would be thru the parasitic body diodes, which are an often unfortunate part of how a FET is created (sometimes they're very useful, though sometimes it'd be really nice if they didnt' exist--for instance in a power switch, you need two FETs "in series" source-to-source or drain-to-drain to block both polarities, if you want to prevent a battery from charging *or* discharging when "off", becuase the parasitic diodes will allow current flow in one direction even with the FET off if you only have one. A diode could be used for one polarity if you never want current to flow the other way, but if it's in a battery's BMS or something like that, you can't do that unless you ahve two separate current paths).


There's probably better descriptions of how MOSFETs do what they do, but here's the first link I found:
http://reibot.org/2011/09/06/a-beginners-guide-to-the-mosfet/
This one
http://en.wikipedia.org/wiki/Power_MOSFET#Body_diode
is kinda technical beyond me for it's explanation, and doesn't really say more than the first one for the subject. I couldn't quickly find any others that didn't just dive right into engineering jargon that wasnt' helpful to explain it.

EDIT (added): There's also a few mentions of "body diode" here on ES, in some technical discussions of various things (including htat back-to-back FET thing I mentioned above, in a precharge circuit):
http://www.endless-sphere.com/forums/search.php?keywords=%22body+diode%22&terms=all&author=&sc=1&sf=all&sk=t&sd=d&sr=posts&st=0&ch=300&t=0&submit=Search
Maybe they will explain it better than I have (which is probalby not very well).

If they weren't then that would put the phases in a short condition and plug braking would result. Justin says the parasitic iron losses we feel as cogging taper to a fixed amount, and we feel that when we pedal only with a DD motor. We also feel how little the force is by the way we can coast for pretty long distances. Your vibration seems more likely to be from an out of balance wheel, but I guess anything is possible. Even downhill I've never gone faster than my no load speed, and if Harold goes even close to his no-load down those roads he'll kill himself. If it's something I've not seen, then I need a plausible explanation.

Unfortunatley I don't know for sure what it was, just that given the limited evidence I had from the single trip, the best-fit theory that I could think of was that of voltage higher than present battery voltage being generated by the motor, fed back thru controller FETs' body diodes into the pack. I suppose it could be something else, but I don't know what else it might've been.

All of my wheels are probably unbalanced :lol: but that definitely wasnt' the vibration I felt (because that is different). What it actually was I don't know for certain, though, just that I do think it was that current fed back into the pack.

edit- please don't go flying downhill on some busy street on your low speed ebikes to find out.

Oh, I won't do it on a busy street...only if I can find a time when that street is *not* busy, preferably not occupied at all. It's downhill with no side-streets feeding into or out of it for the one stretch I've ridden before on various bikes (used to do it on a pedal bike just for fun when I was much younger and more resilient, and probably dumber. :lol.