Lithium Traction Pack From Scratch--Update

Not much progress here yet. Still trying to find enough time to test the cells, sort them, and then find a good way to assemble the packs.

A new problem with doing it is that the Sorenson I had been using to charge the batteries on CrazyBike2 before, and was going to use to charge up the NiMH packs (from deardancer) and test and charge the Li cells with, just sparked and smoked when I turned it on last night, even though it wasn't connected to any load yet. It's a linear supply, and does not require an external load to operate, so something must've died in it during power-on-surge. A transistor burned and a resistor smoked, and a couple of traces on the board's cardedge connector vaporised, too.

I've got three others (only 40V models) that are not working for various reasons, so I will need to check their boards for the values of parts, and then see if I can trace out enough of the circuit to ensure replacing the blown parts is all that will be needed, so I don't smoke more stuff when I turn it back on again. :roll:

Maybe I'll get the others fixed while I'm at it. :)

I did have another idea for charging the NiMH, though: I already had two little NiMH chargers for AA batteries, and I found another for a couple bucks at a thrift store, so now I could charge up to twelve cells at a time. All three chargers will charge either two or four cells at once. They are all microcontrollers or dedicated chip chargers, so they should be safe to use with any NiMH cells.

I am considering putting charging taps on every cell in the NiMH packs, in connectors of four cells, and one of two cells. Then put a mating connector wired to the contacts on each little charger so I could not only plug in to these cells, I could also still use them for the AA and AAA cells I already use them for (for my flashlights/headlights/taillights, etc. on the non-ebikes).

Then I would be able to charge three sets of cells in the packs at a time. On the 36V pack, that's 30 cells, so two charge cycles for 6 of the 7.5 sets in it, and one more charge cycle for the other set plus 2 cells. On the 24V pack that's 20 cells, so only two charge cycles total (one for 3 of the sets, and one for the 2 full and 1 half set).

The whole pack will not get that warm this way, and though I will have to manually plug and unplug the charging connectors after each cycle, it will let me safely charge the packs.

Well, assuming I don't burn out the chargers doing it; they only put out less than 500mA charge current. Well, one of them can put out almost an amp charging current if it's only charging two cells. I'll try it out with the cheap thrift store one first. It's the model down from one I already had, and is an Olympus BC-100.



I'm also considering taking a bunch of old celphones I have that are broken in various ways, and wiring them up to charge cells. They're all isolated from each other, so I could theoretically charge the pack "in place", with charging taps coming out of it for each cell, and a charging connector. It would never be a fast charge, but it would be possible, though a lot of work.

I would need to take the little BMS board off each celphone battery, and lay them all out on something flat. Then solder wires from the cell connection tabs to the interconnect that would go to my pack cells. More wires from each board's input connection tabs to the celphones themselves.

If I have enough celphones that actually give me a display (many have broken screens or even broken-off flip tops) then I can even monitor the charging process via the little battery meter on the displays. Not much of a meter, but better than nothing. :)

Chainrings Are All Evil

Actually, not so much evil, as just insufficient to handle the job on this bike. :( But first, some info and pics of the things I did to fix recent problems....

Considering what I started with, I decided to use an older less damaged wheel to redo. The pic below is of the one damaged almost three weeks ago. The bent axle is pretty clear

and you can even still see the rim bending a little, though I straightened it A LOT just to get it round and flat enough to roll down the road to get home.

The spoke hole damage is what forces me to change rims entirely:

Its' very bad, and holes all around the rim on the drive side are like that

where they started out flat/flush. None was actually pulled *out* of the rim, nor were any broken, but it's bad. I have not taken the cassette off to examine the hub. I just went ahead and redid the wheel using the old Roadmaster wheel that was last bent by a pothole (I think), and replaced it's bent axle with one from one of the Christmas parts bikes, and used a cassette from the other one.


An overview pic of the repaired bike (after today's failures but you can't see them in this pic):

I rode around the neighborhood for around 4 miles testing stuff out without any problems, coming back to the house after every little loop to check things, tie wires down, etc, as I made sure each thing worked.

The newly built wheel, using the stainless spokes. They seem to be doing better than previous ones, as I do not get the wheel flex I used to with the old thinner (and probably cheap steel) spokes that had been in that rim, when I turn, etc.

After a few miles the wheel needs semifinal truing (and will probably need it once more after a few more miles, as the spokes settle in).

The tire is not yet aired up in the pics above, which were taken with the bike upside down but camera held that way, too. :)

This is a chain deflector made to help hold the pedal chain about a millimeter away from the motor chain, as it intersects with it near the receiver rings, so they don't rub anymore.

It's made of a piece of my sister's discarded plastic cutting board (either teflon or nylon, don't know which but it works either way).

The clearance is VERY narrow.


I also decided to do the same where the pedal chain crosses under the motor hub axle, as sometimes in left turns the chain would rub and even catch.

Now it is MUCH quieter, meaning that it was rubbing against the motor chain a little bit even when it did not seem to be, and now is rubbing against the plastic but not making the little ticking sounds I could sometimes hear.

The clearance is a couple of millimeters.



The front brake really wasn't sufficient before, or wasnt' working well, not sure which. It had been a linear side-pull style, with the little metal noodle and all to redirect it to vertical. Now it is a set of center-pull, again off one of those parts bikes.

They're cheap brakes and I don't like them much. But they work better. Not good enough, but better. The hard part was that they require something external to the brake unit to push the cable housing against. Normally, that is a bracket that is part of the U of the fork, but that wasn't possible on this shock fork, or else pulling the brakes just compresses the shock, rather than braking!

The shock fork on that other bike has the bit built as part of the U, but that whole fork is flimsy--I can twist it with my hand, unlike this one, so I don't trust it on this heavy bike.

So I took a little black steel rackmount ear tab and bolted it to the brakemount/reflector hole on the U, then used a seatpost-mount tab for this style of brake off another bike, bolted sideways thru the rackmount ear upper hole. The bike cable housing is then pushing against the fork thru this, and it works very well with no visible flex.

It is still not enough braking power, and I still need something like disc brakes (possibly in addition to the rim brakes), once I can figure out how to design some, if I don't run across any on something scrapped out.

Another addition is a Stanley Tripod Flashlight. It's a Freecycle find, and was described as not working. Indeed it did not, when I got it, but a quick check inside found that one of the power wires to the LED board was never even soldered. The wire ran thru the hole, and there was hotglue from the factory to hold the wires down, but they missed soldering this one. Easily fixed, and voila!

For now it's just zip tied to my existing light.

It was daylight when I took the pics (noonish), so I don't yet have pics of it in the dark. I will have a separate post for it later. But it has a very good beam, though not nearly bright enough for most street use. For canal path or unlit roads, it would be fine, but where there are other light sources shutting down my eyes' ability to open up the iris, it's not enough to help very far away.

It lights up street signs EXCELLENTLY, though, when it is aimed high. Aimed normally, it'll show me the holes in the road fairly well at 20-30 feet.

Don't know battery life yet; it runs on 3AA batteries, and can have a set in each leg. Right now I have two sets of NiMH in there in parallel, one 2000mAh and one 2300mAh. The third leg holds a set of regular Duracell AAAs, with a piece of plastic keeping them from being used at the same time as the much lower voltage NiMHs. If the others die, I can take one out of each leg and pull the plastic out of the Duracell leg, and use them. Only doing this now because I don't know the lifespan of the light yet, and don't want it to suddenly die on me.

Once I figure out what the electronics driving the LED are, I may change it out for a brighter one I have, if they will handle the current it needs to draw and can be modified to do so.


As the Curtis is a 48V capable controller, I decided to also add the fourth battery:

For now it's just secured in the righthand cargo pod, until I can tell if it makes a difference. I have not yet wired in the chargers. This battery is wired in as the "top" of the pack.

While I was at it, I also wired the lights into the monitoring circuit, so the Turnigy meter can tell me about their usage. So far it takes about 350mA to run the CFLs at 48V, including the laptop adapter used as a DC-DC converter. It's only a little less on 36V. Turn signals take the same 2A-ish peak, dropping way down pretty quickly as they blink each time. The LED brake light is about 300mA by itself.


The curtis itself is mounted on the side. Even during a test where I put the front of the bike against a wall, and ran the motor at about half throttle, hard enough to spin the wheel in the dirt if I didn't lean on the bike, it didn't get even warm for the few minutes of the test. The motor itself warmed up quite a bit.

So either the Curtis is holding the heat inside due to the electrically-insulative pad it uses between the inside heatsinks and the case, or it simply isn't getting warm enough to notice.

The main keyswitch is this:

glued down into the top of the steering tube the handlebars mount to. Horizontal is off, and vertical is on. Have to turn it off to take the key out.

Since things fail, and I might need to reach it fast, I also wired this in series with the keyswitch:

It's the run switch from the old Honda scooter. I left the handgrip (throttle) off of the assembly, and just used it for the knob and the brake handle (and built-in weatherproof brake light switch).

Center is run, and up or down turns it off. Can be flicked with my thumb if needed.

Ideally I'd like to take the brake switches and wire them to a DPDT relay. One pole would be NC for the motor run line, in series with the keyswitch and the run/stop switch. The other would be NO for the brake lights themselves. It's just something I have to "get around to".


Mounted on the bottom/inside of that is the throttle pot. It's shown without the lever here for reasons best explained in a picture farther down.

Until I fab the other metal bracket for it, it's screwed in securely to the grip body on one end, and ziptie-clamped to the handlebars on the other end. It won't move in normal operation.

The lever runs parallel to the grip, so I can push it down with my thumb. To fully grab the brake handle requires letting go of the throttle, making it not quite impossible to power the motor while brakes are on, at least with the front brake and this hand. I could still do it using the rear brake and my left hand, of course, which is why I want to do the brake-cut-off relay.

But first, I have to makea new throttle pot clamp:

It's metal, not plastic, but it broke like plastic.

I can only assume I must have somehow tightened the set screws on it too much, although I am not sure how that would break it like this, something did. It came apart as I lightly pressed on it after I got home, so at least it didn't cause me a problem on the road. Since the spring return is done by pressing against this black piece, if it had happened on the road it would have left the throttle "stuck" in the last position, requiring that I manually grip the shaft and turn it.


Now for the ugly part. :(

Less than a mile or so into my trip, another of those half-second-to-destroy-things failures happened, again with the chain derailing, but this one was caused by my fiddling with what had been perfect alignment, in order to fix the pedal speed problem (having to pedal really painfully fast to help the motor at any high speeds), and the pedal-chain looseness problem due to being a half-link too long or short, because of tooth count on the pedal chainring.

I thought it was perfect this time, but apparently not. What basically happened was the motor chain derailed to the left of the motor receiver ring, got caught between the ring and the outer guard of the ring, which being not only metal but actually part of the crank spider meant that it was strong enough to then force the ring inward slightly.

The teeth on that ring must've caught the outer edge of the pedal chain, which then was pulled onto it, bending it in even further since like the motor chain it has no slack.

Then it bent the pedal ring outward, and the bike STOPPED. That all happened so fast I didnt' have time to prevent it, just like the other disasters of this type.

Fortunately the pedal ring is a 3-ring set now, so I was able to take the extra link back out of the pedal chain, put it on the middle ring, bend the motor ring back out of the way, set the rear drivetrain to the front granny ring, and pedal my way the rest of the way to work and then home later.


So I guess it's time to

A) make solid steel chainrings to use with the spiders (have to find some of my scrap plate steel of the right thickness, print a drill pattern from the computer and glue it on, then drill it out, file it, and then harden it somehow).

and

B) find a way to ensure perfect alignment. I don't really know how to do that, as I was SURE it was aligned already, and it worked for almost 5 miles with zero problems, then suddenly BLAM.

Nothing shifted around or is loose, either, even under motor tension, that I can see, but I know conditions while moving on the road are different.


Either way, I'm guessing it's getting time for CrazyBike3, 1000-mile mark or not. :(

2QD Still In Progress, Now Using Curtis 1204-410 Controller

Since I have had so very little time to work on anything recently, I haven't finished the 2QD controller repairs or the physical repairs to the bike (wheel, chain).

The major problems were just the power output section (bottom two MOSFETs blown, gate resistors burned open as they were designed to). But one minor problem that kept anything from working right was a 9.1V zener diode that was only allowing 1.45V! So there was no internal power supply to run the entire comparator and feedback/control section, which is the majority of the controller.

I fixed that by replacing the zener with a 5.6 and a 4.1 in series, which while higher than the original still allows it to work. This got the main section working again, and now I just need to finish the power section as described a couple of posts back. I have wanted to use a different case for a while, so now is my chance.

Since it is taking a while to figure out and then make the holders for the FETs to line them up and keep them tightly against the case inside, and to polish the aluminum and the FETs for flatness and smoothness (for better heat transfer, since I have to use thermally conductive / electrically insulative pads, too), I decided to take a quick look again at the Curtis 1204-410 I have had for a few months with little time to troubleshoot.

I let it sit on the bench powered on (but not doing anything as it doesn't respond to input), for a while, and suddenly it started working, the motor attached to it began slowly spinning (the throtle was just a regular pot set to barely on). Apparently once it got warm enough (from me having the oven on to warm up the room), a connection was made well enough to start working.

There are six interconnect wires between the Curtis logic board and it's power board. Two carry B+ and two ground, and the other two carry signals. One is the PWM output to the FETs, and the other looks like a feedback from the FETs as it is time-shifted just a tiny bit late (which I can barely see at all with my old 531A), but identical to the PWM waveform.

The solder joints on them must've been flexed or vibrated enough to crack them, so they would only make connections good enough to work when warm or hot. Over 85F, anyway. Under that, they might work and might not. I reflowed the solder and now they always work.

Since it's a 36-48V 225A controller for brushed PMDC motors, it can be used in place of the 2QD, so for now I put it on CrazyBike2 and verified it works with the bike. I can use it until I finish the 2QD rehousing.

Now I need to build a new rear wheel, move the chain and some shifters and stuff from one of the spare bikes I got for parts from someone for Christmas, and finalize the new throttle control setup, and CB2 will be ready to ride more than just for tests.

I also cobbled together this temporary throttle lever and mounting, for using a powerchair's spring-return throttle on CB2.

The spring is so strong that without a pretty long lever, I cannot keep it pressed down for very long. Sorry the pic is so dark, but the flash keeps shining off the metal and the camera autodarkens the rest of it to compensate. :(

The aluminum bars are just end-pieces, uncut, off the rackmount fan enclosure from the same old studio-type Sony VTR the gray transistors from the last post are from. I'll probably wind up modifying a brake lever setup to use for this instead, as it will already be designed to clamp to the handlebar, and it has a long pivot arm.

Optionally, I considered using a lever-style shifter, but it is more complicated to set up for this, and it is also a much shorter lever.

UPS And PC Power Supply Parts Bonanza

A bit of salvaging of some old computer power supplies and UPSs (most of which were found in alleys or roadside on bulk trash days, over the last few months, but sat "intact" until now due to lack of time) netted me several pounds of parts (not counting the toroids or transformers!), including the stuff shown in the pics below.

Bunches of small value caps, diodes, zeners, transistors, mounting screws, heatsinks and clips (and thermal pads), and lots of resistors not yet taken off the boards (not in pic), several TL431A and some LM317


Some very old 100V+ Vce type transistors in PNP and NPN, off some boards from a Sony VTR (I never saw the VTR, just the boards)

They'll be used to replace some lower voltage 2222's on my 2QD so I can up it to 48V+ usability.

Bunches of small signal transistors, 50V Vce types, a bit better than the 2222 but not much.


A few beefy dual-diode (common cathode) units, one of them up to 40V at 50A!

Also about three times that many smaller TO220 versions of these, mostly in the 40V 3A range. All can be used with heatsinks to parallel unequally-charged battery packs in a pinch.

Of course, there are lots of large caps, too, in low and high voltages, and many form factors.

MOSFETs; lots of them, too, though mostly lower-voltage types, and generally fairly high RDSon.

Some IC's, too. Optoisolators, LM339 and LM324 chips, other single or double op-amp chips, some logic chips (74x series), some "house branded" chips in the UPSs which probably means they're ROMs or pre-programmed MCUs. Some standard PWM SMPS control chips, might be adaptable as controller chips.

Transformers, connectors, toroids, cables, wire, heatsinks, switches, LEDs, etc. Fans, too, but the fans are all defective. They might have usable hall sensors in them, though, as long as I don't need linear sensors (they're more likley to be switching types).

Most of the desoldering was done by carefully using a very small propane torch to heat the thru-hole lead areas, while gently tapping the PCB on the bench (outside, so any fumes would not suffocate me). Some things required a solder-sucker and regular soldering iron.

I should be able to build up my other 2QD controller out of what's there, plus have plenty left over for other projects for a while to come, such as a BLDC controller.

There are LOTS of electronics that have all this stuff salvageable if you have time to do it. I generally spend only a minute or two at a time, over days or weeks, and end up with what looks like "Christmas at the parts store". :) Even if only half the parts worked when done, it'd have saved me enough money it'd stil be worth it.

2QD Repairs, Modifications, Thoughts, Part 2, Used NiMH Packs

Some pics of the modification/repair in progress.

This is the old Jensen inverter case:

The three long caps "below" it are the ones from the UPS. The smaller one to their right is the one I originally had on the 2QD, and it has been getting hot with generous motor use.

An end view of the box with all the controller parts loosely fit inside it (except for MOSFETs)

The two large holes on this end used to house the AC outlets on the inverter. The switch on the right is one I've had laying around unused for around 15 or 20 years; bought at Radio Shack for some forgotten purpose. ;) It has an orange LED in it that will be used at VERY low brightness (20K resistor) to tell me if the controller is powered on and the throttle connected, and not open-circuit.

With the case open, you can see the general fit of parts. The three caps with the main power supply wires feeding between them will fit on one end/side. The MOSFETs will be clamped to the left side, and hand-wired to the PCB.

The PCB will fit in as seen above, and is cut down from it's original length to do so.

Another shot of the layout.


The 2QD PCB freshly cut.

It is separated just at the gate resistors for the lower leg of the half-bridge, as that is the length needed to fit inside the Jensen case.

The MOSFET end can be used as-is to keep the MOSFETs together, and easy to mount to the wall of the case.

They do still have to be electrically insulated from the case, as their heatsinks are electrically active and different parts of the circuit.

I am not sure when I will finish it and get CrazyBike2 back on the road for the 30 miles it needs to get to 1000 miles, as time is a scarce commodity right now.



To add to my growing collection of power sources, a couple of NiMH packs arrived tonight:

USPS kind of squished the package but didn't damage the contents.

They did put a nice notice about the oopsie, under the shrink wrap plastic they put on to hold it together.


The packs themselves:

The white one is a Sanforce 24V pack. The green one is a 36V pack from a Giant Suede.

I know that the 24V pack was damaged a bit by a thermal issue during charging, so it reportedly now has voltage sag if more than 7A is drawn from it, even at full charge. It's made of 10 super-F cells of 13Ah each. It's charging rate is 1/10C, for 16 hours. Don't know the original discharge rating, but now it's about 0.5C.

The 36V pack's original specs were 12 pounds, 9Ah, rechargeable in 4 hours (so charging at about 4.5A or 0.5C), and originally drove a 240W hub motor. Don't know what it's discharge rating is.

I dont' have a NiMH charger, so will have to use the Sorenson and careful monitoring for now.

I'm considering putting them in series for a 60V pack, then modding a 2QD for that high a voltage operation, and putting them on DayGlo Avenger along with one of the various motors I have around here, with appropriate reduction system. There's a 1/3HP 100VDC weedeater motor I might try, or perhaps a couple of my radiator fan motors in series. Have to see how things work out with CB2 first.

2QD Repairs, Modifications, Thoughts

The repair of the controller has turned into a modification session, too. So it is taking considerably longer than I originally expected or intended.

I'm upping it to 48V capability, changing out a few transistors and whatnot, as well as installing the whole thing into a better case that will provide heatsinking over it's whole surface. The case used to be for a Jensen 300W car AC inverter that doesn't output anything, which I gave up on fixing for now (I can always rehouse it later).

The extruded aluminum case is not very large but is big enough to hold the 2QD board with the power end cut off, 3 very tall low-ESR caps (75V 1500uF each) off that giant UPS board instead of the dinky one I could fit on the 2QD PCB, so much better power filtering, and plenty of surface area to bolt multiple MOSFETs to. Plus I can seal it up for watertightness and still vent all the heat outward, unlike the plastic PacTec project box I had it in before, with the tiny heatsink out the end of it.

I'm still waffling back and forth on whether to just use the TO220 style FDP038AN06 FETs I already use, or the higher-power-handling but higher RDSon TO264 style NTY100N10 FETs I used so well for so long on the original rebuilt ScootNGo controller.

Either way, I have to hand-wire the FETs to the control PCB, as there is no way to fit the whole PCB in there in a way that lets me bolt the FETs directly to the casing, without removing the FETs from the PCB. So I cut the entire end of it off from the gate resistors on, and will just run wires to each FET and then bolt them to the inside of the case, using insulating pads to keep them electrically isolated between the upper and lower halves of the halfbridge.

The case also has a spot for an automotive blade fuse. I am not using it now, but I may wire it in later, once I have an easy way to set a limit for the current on the 2QD. Right now the 2QD limits current via a voltage drop measured across the MOSFETs, so it depends on their RDSon. Since the RDSon of the MOSFETs I am using now is so low, around 3.5mOhms (actually half that since I've got parallel pairs), the current limit is apparently very high. Beyond 153 Amps, at least.

There is a current limit fine adjust resistor, and it's coarse adjust next to it, so I just have to figure out the circuit so I can work out what potentiometer I can install there to give me a good range of limitation I can use, for as low as 5A to as high as 50A (more if I have MOSFETs installed that can handle that). Then I can also use this to test for various different limitations, such as batteries that can't supply as much current, like my Li-Ion and a pair of well-used NiMH packs someone on ES is sending me (which might put out 7A on a good day).

Also so I can test for how well it performs at the actual legal max of 750W. ;)

I've also been charging all the SLAs I have around here for the last week or more. Some of the UPS ones simply won't charge well, but I am still letting them trickle charge in hopes they might recover at least a bit. I think that with the two newer ones that came in that most recent powerchair case, I will have 7 good ones in the 17Ah range, and 2 not very good ones, and one dead one. Plus the three 31Ah U1s I'd started with but changed out due to weight when I got the 17Ah UPS batteries. One U1 seems a little weaker than the other two.

I haven't done a full discharge test on any of them yet, but will do that using the Turnigy meter to get an idea of how many Ah I can realistically expect out of each one, including the three already on the bike.

More Batteries, More Boxes, More Chargers.

Recently donated was another pair of old wheelchair batteries in their box with a charger. All of these are useful, as the batteries are the same size as my 12V 17Ah, but they are 20Ah. The box is an interestingly useful shape, split to lock in over a central electrical connection, but in this case it is wide enough to fit over a top tube! The charger is a 4A 24V charger almost identical to the 3A charger I already have.

First, there is the possibility now to hook up both chargers like this:

if I change the pack to a 48V using four SLAs instead of the three I currently use. I was planning on that anyway, with the fourth to go in the rear triangle once the suspension is done. This would let me simply plug in wherever, and charge up the batteries unattended with the automatic chargers' own 3-stage normal charging, instead of the two ways I do it now.

At home, for overnight charging, I set the big heavy Sorenson for 44.5V and max current, then plug it into the pack in place of the motor controller.

On longer trips where I can recharge along the way, I carry the 3A 24V charger, which is only a couple of pounds, along with an Anderson that has a jumper wire across it. Since it only charges two at a time, I unplug one battery and plug in the jumper in it's place, then plug the charger in place of the motor controller. Every 30 minutes to two hours, I move the jumper to a different battery connection, so that all three get a part of a charge cycle. It is not optimal by any means, but it extends my range some.


Thew new stuff:

The new batteries are 20Ah,

But it is the same size and about the same wieght as the 17Ah:

The battery box opened up

and the handle on it's top is removable.

If I cut out the part where the charger connector went (an XLR), up to the bottom lip of the cover, then put an upside-down "U" of aluminum sheet in there to help restiffen the case, the box can be placed across the top of the top tube just behind the headstock, at the front of the bike.

This would put about 30 pounds up there, so it will definitely change the way it handles, and will probably take out most of the shock absorption the shock fork gives me now.

If I used this box I would put the fourth battery plus the rearmost of the three existing ones in this, moving much more weight up front to balance the bike, which would help especially when I am going to carry cargo.

However, I could also make it so these are optional batteries only used for additional range. To do this, I would keep all three existing batteries where they are, and add two new ones in this, plus a third new one in the rear triangle. All three new ones would be wired in parallel with the existing ones, as a second 36V string. A mostly-removable wire harness would need to be made that leaves extra Andersons hanging at front and back always on the bike for the other batteries to just plug into, so that I could add or remove the extra ones quickly as needed.


This would still leave me with the problem of charging them, as there would still be sets of three. However, they can be charged in pairs at least, so an automatically-rotating charger is possible but would involve heavy-duty relays/contactors or cabling (which would also be required to auto-rotate as I currently do manually, as motor power would have to flow thru some parts of the current system).

So, to charge them in pairs like this, I could simply use a timer that every 10 to 30 minutes or so would switch from the first pair to the second to the third and back to the first, switching a set of high-power relays in at least one case, though low-power could be used for the other two pairs.


For the "bottom" pair in each triplet, simply switching a low-power relay on across each one pair to engage the charger would work.

For the "top" battery in each triplet, it is harder, as they cannot directly be connected in series. First their parallel-ish connection (both positives wired together) must be changed to series (positive of one to negative of second, opposite pos/neg then connected to the charger).

That one requires a heavy duty contactor to open between the positives of each battery and the rest of the bike. Then a second (low-power) contactor to close that connects the batteries in series, and also to the charger.

The heavy-duty contactor is the issue, as it must be able to handle 100+ Amp surges during motor operation (though it does not ever have to make/break during load).

So it is much easier to go to 48V and get only one extra battery's worth of power, for now. At least until I get the Li-Ion packs finished (they are not yet started for lack of a BMS).