First-timer getting down to business

[TylerDurden]

How much abuse could such a setup take in terms of deep discharges, and how quickly can they be recharged? And how on earth would I go about modifying the things into a setup like this properly? I assume all that extra little protection circuitry in the pack need to be preserved somehow. If you can explain to me how to take those packs and turn them into an easily-chargeable safe single battery pack, I'm all on board.

Here's one member who went full tilt: maytag

http://endless-sphere.com/forums/viewtopic.php?p=9329#9329

 

[xyster]

Why the Milwaukee over the DeWalt? I thought that a123s were the dog's bollocks and Emoli second-best.

That depends on how you weigh the relative importance of capacity and ease-of-charging versus cell life and high C rating (the drainrate). In real-world ebike conditions, emoli cells are each about 3.8v nominal and 2.6ah, whereas each A123 is about 3.2v nominal and 2.2ah. That difference adds up, and because the cells are both the same size, emoli packs can be made more compact. Emoli cells can be charged with unmodified RC or other common chargers for lithium cobalt cells. There's still few good charging options for A123's, but that will change soon. The A123's should live much longer though -- from the best info available, it sounds like about twice the cycle and calendar life of emoli's. However, both types live an exceptionally long life for a rechargeable battery (1000 deep cycles for the emoli versus 2000 for the A123...about).
Emoli's can be discharged continuously at 12C, the A123's at 30C. For an ebike sized pack, the difference matters little since a 10ah emoli pack can put out 120 amps -- far higher than any controller's current limit or ebike motor's ability to use those amps. In the RC world though, the little airplanes regularly pull 30C from a 1p A123 pack, so A123's are much preferred for powering that hobby.

The emoli's have been well tested and highly praised by Jondoh here, and Ypedal uses the same chemistry in a different brand and form. The A123's have likewise been well tested and received high praise. Myself and a couple others have argued that emoli's are being generally overlooked without good reason. Both cells have been very widely reviewed in the battery section of http://www.rcgroups.com.

And with the Milwaukee, one pack contains 7 cells with a nominal voltage of 4v, and approx. 3Ah per cell. With $500, that's 6 packs, 42 cells, for 540Wh. How much current can those Emoli discharge continuously? Because if they can handle a lot, I think that a 84V 6Ah 21s2p setup would be optimal as a starting point. I can always add more as future funds allow.

I agree with your 21s2p set up, which should provide 72 amps continuous without overheating or suffering damage -- good headroom for a 40 amp controller. You should read Jondoh's emoli pack build:
http://endless-sphere.com/forums/viewtopic.php?t=233&highlight=milwaukee
He runs 2, 7-cell packs in series. You might need to bypass the internal BMS (battery management system), or pull the cells out of the container completely if you want to put three of these packs in series because the BMS might not like that much voltage, although it does fine with two packs in series. The same thing has to be done with Dewalt/A123 packs, and isn't that difficult for someone who has some basic experience with electronics and soldering.

Amazon shows a shipping weight of 2.4lbs for one battery pack. That'd be ~10lbs after it is all packaged, providing 540Wh. For the same $500, I could make a 92v 8s 20Ah 1840Wh pack, weighing in at 112lbs. 1/3rd the capacity, at 1/11th the weight.

You mean by buying $500 of SLA instead? 112lbs...ha ha! Not feasible on a bicycle unless pulled in a trailer.

How much abuse could such a setup take in terms of deep discharges, and how quickly can they be recharged? And how on earth would I go about modifying the things into a setup like this properly? I assume all that extra little protection circuitry in the pack need to be preserved somehow. If you can explain to me how to take those packs and turn them into an easily-chargeable safe single battery pack, I'm all on board.

Lithium powertool batteries are made to handle deep discharges and lots of general electrical abuse. Myself and many others here can explain exactly how to build a pack with either one, but a lot of depends on some build preferences and specifics only you can answer. I would recommend doing some more reading here starting with Jondoh's build for emoli/whole pack systems, then going to GGoodrum's thread about A123 pack builds here:
http://endless-sphere.com/forums/viewtopic.php?t=2498
Then come back with any questions/concerns you still have.

 

[lazarus2405]

You mean by buying $500 of SLA instead? 112lbs...ha ha! Not feasible on a bicycle unless pulled in a trailer.

I actually thought about that for a short time. My family owns an old canvas camping-type trailer designed to comfortably carry a kid and a cooler. I could load it up with 100lbs of batteries, hook that alternate power source to my controller, and make a Wal-Mart run for six cases of Gatorade. It sure beats having my roommate take me in his '72 Ford pickup.

Anyway, I saw that thread there, and that is exactly what I want to do. Keep the BMS and the entire housing intact, use the stock Milwaukee chargers for a fast, convenient, and robust way to get back on the road... And while I'd only have half a kWh, since the batteries are so light I'd be able to really use pedal power if need be. I even love the bit with replacement connector blocks to make a perfect connection. Just throw a pare of Powerpoles on each lead of the connector blocks...

It keeps getting better. Amazon sells sets of two batteries and a charger for $160. $80 a battery with a free high-quality warrantied 2-hour charger for every battery. I may be so giddy with this that I might just shell out for another three packs to make it a 3s3p 84V 9Ah setup... but that'd require me to dig a little into a student load, which is, um, not a wise choice. While the loan does cover living expenses such as the explicitly stated "transportation", no one wants to pay interest on batteries...

Anyway, thank you a bunch you two. You've helped me hammer out the very last question I had, and mad a Li convert out of me.

 

[xyster]

Anyway, I saw that thread there, and that is exactly what I want to do. Keep the BMS and the entire housing intact, use the stock Milwaukee chargers for a fast, convenient, and robust way to get back on the road...

Don't forget: nobody has tested the Milwaukee BMS with three V28 packs in series. From Jondoh's results, it's obviously OK with two in series (56 volts). You may have to bypass the BMS by tapping onto the main power leads from the cells, than running leads out the case. You could still keep the BMS otherwise intact, so as to have it balance the cells during charge normally, and allow normal connection to the stock Milwaukee charger.

...and mad a Li convert out of me.

Great -- another mad lithium convert is just what we need.

 

[lazarus2405]

Well, it'll still be a couple weeks before the funds are in place, but as soon as I have results, I'll be sure to share them. For now, we'll have to rely on theory...

As I understand it, each individual pack isn't being subjected to anything out of the norm. It's still only producing a 28V potential difference, and the current is nothing out of the ordinary.

So how does the BMS work? I understand that it balances the batteries while charging, and during deep discharges it shuts off cells that are relatively low to prevent a cell reversal. Is that all? I suppose this particular one has the extra doodad for its LED voltage indicator. What else does it do, and what role do the MOSFETS play?

 

[xyster]

As I understand it, each individual pack isn't being subjected to anything out of the norm. It's still only producing a 28V potential difference, and the current is nothing out of the ordinary.

So how does the BMS work? I understand that it balances the batteries while charging, and during deep discharges it shuts off cells that are relatively low to prevent a cell reversal. Is that all? I suppose this particular one has the extra doodad for its LED voltage indicator. What else does it do, and what role do the MOSFETS play?

I think you covered the bases as far as BMS functions. I'll leave the technical explanations to the analog electronics specialists (since I'm too dumb to explain), but note that the FETs (transistor like switches) are exposed on the external side to the full voltage of the whole pack power circuit, and are well known to fry when overvolted, as many people have fried their Dewalt pack BMS by wiring packs in series via the typical external connectors used to supply the powertool.

 

[lazarus2405]

So to prevent that from happening, I'd need to open up the case and solder leads between the batteries and the BMS, drill a little hole in the case for those wires, and put Anderson connectors on those wires. Then to charge the batteries I would use the BMS in the stock manner, but to drain them I would connect the batteries using those leads I soldered, which would bypass the BMS entirely.

Correct?

 

[xyster]

So to prevent that from happening, I'd need to open up the case and solder leads between the batteries and the BMS, drill a little hole in the case for those wires, and put Anderson connectors on those wires. Then to charge the batteries I would use the BMS in the stock manner, but to drain them I would connect the batteries using those leads I soldered, which would bypass the BMS entirely.

Correct?

Yep. I don't think you'd necessarily need to disconnect the add-on power leads from each other in order to charge -- but I'm not certain about that.

Magudaman has done this with 4 A123 packs:
http://endless-sphere.com/forums/viewtopic.php?t=1311&start=15

 

[xyster]

And here's a step-by-step disassembly guide for Milwaukee V28 packs (obviously you wouldn't have to go as far as this person did):
http://www.rcgroups.com/forums/showthread.php?t=508443

 

[lazarus2405]

Again, you've been extremely helpful over the last day. It looks like that will be exactly what I will do, and it won't really add too much work to the project since it eliminates the need to order the "replacement" connector blocks. As long as I can keep everything intact for easy charging, I'll be a happy camper.

Now, since I will not be using the BMS while discharging, what precautions will I need to take to prevent cell reversal?

 

[xyster]

Now, since I will not be using the BMS while discharging, what precautions will I need to take to prevent cell reversal?

Excellent question. There are a couple good methods for monitoring and/or automatically cutting off power when the batteries are discharged beyond a certain point -- which, as you probably, is communicated by the battery's voltage.

Basic options:
1) You can modify the controller's low-voltage cutoff (LVC). Power will be automatically cut at the set point.

2) You can use a voltmeter, or something like ebikes.ca's CycleAnalyst (which has a voltmeter), to monitor the voltage yourself, and stop using power at a certain point. This is what I do using a cheap panel-type voltmeter.

3) Design your own LVC to put on your pack that either monitors the whole pack voltage, or each cell in series individually.

4) Some combination.

For longest pack life, and lowest risk of fatal cell reversal, emoli's should not be discharged beyond 3.70 volts each. If you need to push it, 3.60 volts is OK, but voltage can tank extremely fast beyond this point, and since the cells aren't being balanced on discharged, some cells will be below this point already while the cells on average are at or above this point. The voltage should be assessed with the cells "at rest" meaning not under load, which can be accomplished by letting off the throttle and looking at the voltmeter reading. Your prospective pack can be discharged most safely to 77.70 volts (21 X 3.7v).

Here's a capacity versus voltage graph for these cells under various loads. The resting voltage curve, not plotted, would lie slightly above the first 1C curve.

 

[lazarus2405]

How does one modify a Clyte controller's LVC, and how difficult is it? I imagine it involves opening it up and playing with a potentiometer or something. Not something I would want to do mid-ride, or of I wanted to make a quick trip using a different battery setup.

I have been definately planning on using CycleAnalyst, so that's just one more use. Handy indeed.

Thanks for that graph. I was about to ask for one of those After having spent so much time familiarizing myself with B&B's spec pages for their SLAs and Justin's graphs for his nickel packs, I wanted to compare their discharge profiles to that of the E-Molis.

How do operating temperature and charging temperature affect these LiMns? With the air turning colder in Oklahoma, I understand that lithium cells are not susceptible to the loss of capacity at low temperatures which SLAs undergo because of their liquid nature. What is the optimum operating temperature of these cells? About 100F?

I went to my local Radio Shack today to grab a multimeter, solder, flux, and 10 gauge wire. Rado Shack is not the place I remember when I was a kid. It went something like this:
- "Speaker wire?"
"No, 10 gauge wire"
-"What for?"
"To carry a lot of amps. It's for a project."
-"(yelling to the associate) Bob, we got any 10 gauge?"
-"(audibly laughs) 10 gauge? What for?!"

Anyway, I'm planning on getting some soldering practice in tonight. I've never soldered anything to carry more than an amp, so what should I know?

A 30w iron should be fine, correct?

The procedure to join two wires is to strip em, tin the tip of the iron, tin both exposed wires, and join them, correct? Can I cover permanent splices with a few layers of normal average electric tape, or will something like that melt and burn?

Also, if I ever want to take the packs apart and solder them in a different configuration, what is the procedure for soldering wire directly to a cell? I've read that doing so improperly can easily damage them, and I'd rather not kill a $10 cell on my first try.

 

[fechter]

Depending on the variety of the controller, you should find something about the LVC resistors in this thread:
http://endless-sphere.com/forums/viewtopic.php?t=764

I'm still a bit confused about what the actual resistance values are supposed to be, and it seems to vary quite a bit depending on the controller flavor.

You could add a potentiometer in place of a fixed resistor to make the LVC adjustable. Using the CA to adjust the LVC would be much easier.

Electrical tape should be fine for insulating a soldered connection.

Soldering directly to a battery is risky. You need to avoid heating the innards of the battery to the point something fails (like low melting temp plastic insulators used on the top). The best thing is to have welded tabs, and you can solder to the tabs.

If you want to attempt soldering directly to the can, you need enough heat to do the job very quickly and limit the heating time to 5-10 seconds. A 30w iron might not do it. Sanding, flux, and tinning are all recommended.

Yes, Radio Shaft is a pretty sad place these days for builders.

 

[vanilla ice]

Internet killed the radio star.

Remote controlled toys and cell phones, its all I see.

 

[lazarus2405]

The best thing is to have welded tabs, and you can solder to the tabs.

Noted. The Milwaukee packs, like others, have spot-welded tabs to connect the cells. Cut em and solder wire to the tabs.

 

[xyster]

The author of that disassembly thread posted videos here:
http://www.swift-tuning.com/e-moli.php

The pics didn't show the tabs completely enough, but there's gotta be two with wires already soldered for the power leads to the BMS. I'd try to either fold those tabs over your extra power leads and then solder, or if I couldn't do that, strip a little off the native power leads and wrap my leads around it, then solder to connect the two, making certain my leads were also soldered all the way to the tab. Super floppy "spaghetti wire" makes any battery pack job much easier as the soldered connection is much less likely to break when the wire is moved, or vibrated over time. There's not many places that carry it. Here's where I get mine:
http://www.cheapbatterypacks.com/?sid=875992&pgid=wire
For power leads, use the 12 gauge stuff.
You'll probably need a better soldering iron. Even the best RS irons are PoS. Mine melted on me. After that I bought a 100/140w Weller iron from Home Depot for like $40, and haven't had any problems with it. Use pretty much any rosin core solder.

Yah, Radioshack was cool when I was a kid too. I used to hang out there for hours programming in BASIC their demonstration TRS-80s. I had all their electronics kits, and an RS RC car. They used to have a great selection of components from whence I'd buy stuff to mod my car, bug my parents bedroom, jam the neighbor's radio, etc... Now it's just cell phones and consumer electronics crap we can buy at like a hundred other places within a block radius.

 

[TylerDurden]

You can get pretty good wire at discount auto supply stores these days, since high-power car-audio is popular. The hobby stores are pretty good for connectors and small fabrication materials.

Neither kind of joint is the cheapest way, but they offer cash&carry when you don't want to wait for UPS.

An old-fashioned radio & electronics joint is rare these days. RS doesn't even carry R/C stuff anymore.

 

[lazarus2405]

You'll probably need a better soldering iron. Even the best RS irons are PoS. Mine melted on me.

I'll practice with what I've got and let you know. If it dies, well, it wasn't exactly a big investment. I know my father has a big soldering gun I could use, but I get the feeling that it would be overkill. I'm not planning on replacing MOSFETs, but I think I'd like to try this mod:

http://endless-sphere.com/forums/viewtopic.php?t=764&postdays=0&postorder=asc&start=56

I took my bike in today to get looked at. My front braked do not use calipers, but rather have mounts and are welded to the fork and activated by pulling two cables and applying pressure to both sides of the rim. It has no mount on the front for any kind of aftermarket caliper. However, one of these brakes broke off in a crash about three months ago. One LBS told me that my only option was to get a replacement welded on, which after parts and service would cost upwards of $90. Considering that that was about what I paid for the bike (used) originally, I was not thrilled. This place was one that catered very heavily to the lycra crowd and whose employees had mandatory intricately-groomed goatees.

I went to a different shop about a mile away, where the employees drank soda instead of organic papaya grapefruit persimmon sorts of things. The guy I talked to suggested just buying a whole front fork with really strong calipers for ~$40 parts and labor. So far so good.

I was told that because my bike uses an older 1" threaded tube, and most MTBs now use 1 1/8" (or something similar) tubes, I would have an extremely hard time finding a fork designed for discs, and that the only ones these days that used front disc brakes in 1" front fork tubes were designed for 700c touring bikes and thus expensive new and impossible to find used.

Since I will no longer be putting 100lbs of batteries on the bike, I think that braking will be less of an issue, but I still want to have as much braking as I can get. What advice would you folks give? Is there a place online that I could perhaps find a way to put discs on the front without welding? And am I placing too much emphasis on discs as opposed to calipers?

 

[fechter]

Even disc brakes can fade on a steep hill. I think they're better in the rain and certainly better if you're riding through deep mud.

You could try the experimental dynamic motor braking idea. It won't stop the bike, but will assist the friction brakes. It might work well on extended downhills.

 

[TylerDurden]

A soldering gun might be just the ticket... I use one for soldering directly to cells.

If you can solder, you can braze. It's pretty simple, and you can use mapp-gas (oxy/acet is faster tho).

I'm ruminating on the hydraulic/compressed-air regen system for hills: >50% efficiency would be nice.

8)

 

[lazarus2405]

The only steep downhill I can think of in my area is right on my way from campus to the shopping center, which I ride about once a week or so. The moderate downhill is immediately followed by a steep uphill (and of course vice versa on the return). My kinetic energy from not braking through the downhill will speed me up the uphill, where I'll be going just as fast as when I started (minus wind and rolling resistances). That, my friends, is true regenerative braking.

Mud? Pah, the only offroading I'll be doing will be to dodge pedestrians who get in my bike lanes. The key is to just barely clip them with your handlebar mirror so that they get the message.

My concern over braking is primarily over safety in traffic. I guess it won't be too big of a deal, on dry flat ground.

Tyler, the difference is that I can solder in my dorm room.

I want to mount my controller facing the wind on the bottom tube of the front triangle. Can I waterproof it with hot-melt glue?

How on earth can I waterproof my throttle?

How will the motor itself handle the rain? Just heavy rain, not driving through two-foot-deep puddles.

 

[TylerDurden]

If you are a lowly undergrad, you might take a technical-theater course and get access to all the tools and training to build about anything except batteries...that's the chem dept.

 

[OneEye]

On the campuses I went to school it was always the mechanical engineering and mechanical engineering technology students that got to play with the complete metal fabrication workshop. Seems like every year one of the ME's was doing a "better" recumbent bicycle or other small vehicle as their senior project.

What did the CE's get to do if they wanted to have fun? That's right, CONCRETE CANOE. Somehow I never was interested. I almost changed majors just based on that.

 

[TylerDurden]

^^^ :lol: :lol: ^^^

 

[xyster]

The only steep downhill I can think of in my area is right on my way from campus to the shopping center, which I ride about once a week or so. The moderate downhill is immediately followed by a steep uphill (and of course vice versa on the return). My kinetic energy from not braking through the downhill will speed me up the uphill, where I'll be going just as fast as when I started (minus wind and rolling resistances). That, my friends, is true regenerative braking.

Mud? Pah, the only offroading I'll be doing will be to dodge pedestrians who get in my bike lanes. The key is to just barely clip them with your handlebar mirror so that they get the message.

What's your major? You're a very good writer ... for your age. :wink:

I want to mount my controller facing the wind on the bottom tube of the front triangle. Can I waterproof it with hot-melt glue?

Yes, and some people do. I prefer silicon glue in the form of cheap clear 100% silicon bathroom/kitchen caulking. The silicon isn't very heat sensitive, seals well, but peels away easily when need be. Don't forget a squirt of whatever you choose around the wire exit points, and even around on/off switch as water tends to run down wires into holes, and that switch is not otherwise sealed. I regularly ride in pouring rain. I just keep the switch on all the time, and sealed completely, while using a 24v80a relay on my battery box for the main power switch. This also has the advantage of acting as a kill switch in case of an emergency -- such as a throttle that's stuck wide open, as has been known to happen, particularly when wet, particularly LED gauge type throttles.

How on earth can I waterproof my throttle?

Probably lots of ways. I sealed the seams and the wire exit points with silicon glue, then wrapped the outer casing in duct tape hooded such that the seam between the body and the handlegrip is protected from rain, but the twisting action remains unconstrained.

How will the motor itself handle the rain? Just heavy rain, not driving through two-foot-deep puddles.

Motor should be fine so long as the wire exit points are also sealed well. One guy here posted a video of himself riding his hubmotor completely underwater.