Warren's 350 MAC mid-drive (finally) recumbent

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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Re: mid-drive questions

Post by mi7d1 » Jan 03 2011 2:15pm

Warren, are you familiar with the Bicycle Speed and Power Calculator?

The original site is no longer online however one can still access it via the web archive's Wayback Machine.

Here's a link to the calculator;
http://web.archive.org/web/200802130942 ... espeed.htm

There are other calculators available elsewhere on the net but this one is my favorite.

Bill
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Re: mid-drive questions

Post by Warren » Jan 03 2011 2:36pm

Bill,

"are you familiar with the Bicycle Speed and Power Calculator?"

Yes. Have run numbers on several, but real live experience is always better.

My main question is still, "Is running higher voltage always better for overall efficiency?"

Warren

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Re: mid-drive questions

Post by Warren » Jan 03 2011 2:39pm

Bill,

This is the current link.

http://www.hembrow.eu/personal/kreuzotter/espeed.htm

Warren

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Re: mid-drive questions

Post by mi7d1 » Jan 03 2011 3:03pm

Warren wrote:Bill,

This is the current link.

http://www.hembrow.eu/personal/kreuzotter/espeed.htm

Warren
You got me there, I'd forgot to include that link also. One thing to not for the metric challenged is that the hembrow link is only in metric whereas the web archive link has the ability for bot metric and "Anglo-american units" The hembrow link has more velomobile types to choose from also.

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Re: mid-drive questions

Post by Warren » Jan 03 2011 3:23pm

Bill,

"web archive link has the ability for bot metric and "Anglo-american units"

Oh! That is handy. Afraid I still think in Anglo units. Doing the conversions is always a hassle.

My main question was probably just answered here.

http://www.elmoto.net/showthread.php?77 ... peed/page6

But I was hoping it would turn out otherwise. 36 volts would just make my life easier. :-(

Warren

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Re: mid-drive questions

Post by dumbass » Jan 03 2011 6:00pm

Warren wrote:Bill,

"are you familiar with the Bicycle Speed and Power Calculator?"

Yes. Have run numbers on several, but real live experience is always better.

My main question is still, "Is running higher voltage always better for overall efficiency?"

Warren
I tend to run low voltage (24) because it's easier to build and carry the packs. However, I think most will tell you it's better to run as high a voltage as you can carry. The higher the voltage the smaller wire you need. And because a lot of people tend to use small ga wire there is less chance of the wire being overloaded and therefore, wasting energy to heat. Remember while you are doing your calculation based on volts, amps or watts I think most would agree it's really the wattage output of the motor that really counts. A lot of people talk about upgrading a 24v Ezip for example to a 36v motor. The problem is the 36v motor is aproximatly the same RPM and the wattage when back calculated is the same as the 24v motor. Bottom line no real gain except for loses caused by small ga wire lose.

That's my thought anyway.......

Bob

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Re: mid-drive questions

Post by pdf » Jan 03 2011 9:58pm

You are running 36 volts, correct? With a 15 amp max, that is maybe 400 watts coming out of the motor, and another 100 watts from you. What kinds of speeds do you average with that power?
My bike does around 20-22 mph the way I have it set up now, I think. I tested it once but for the first 100 miles or so I had it set to 10 amps. I will check it again but I think it is around 20-22 mph. For me, speed is not what I am looking for, esp. in the winter. I can't generate heat fast enough when it is below 30 to stay warm if I go any faster, frankly. Anyway, my commute is only 6.5 miles one way and part of that is on a greenway with foot traffic and a lot of roots pushing up the pavement. If you drive more than 15 or so on a non-suspension bike, you will beat your brains nearly out. So I'd say it is around 20-22 mph top end. However, my bike is not geared for high top end either so I could be simply winding the motor out. I'll check it tomorrow on a flat stretch, although they are difficult to come by on my route.

And by the way, I would be very much surprised if I was putting out 100 W. I used to live under the illusion that I was adding significant effort, but ever since I had to hump it home when my battery died, I got a lesson about how much help I was providing and it wasn't much, apparently.

Let us know what you come up with for your situation.
-------------
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Re: mid-drive questions

Post by amberwolf » Jan 04 2011 2:19am

Regarding "is higher voltage always more efficient?": It depends. In general, I'd go with what's been said above, to go with the highest voltage you can carry, with a caveat:

--if the higher voltage ends up forcing your system to be too fast to use full throttle for the majority of your riding, then controller internal losses due to switching/etc at partial throttle may cause controller heating that could be a problem, depending on your climate and usage. I've experienced this already, damaging capacitors (fortunatley not FETs) in a controller while riding on a very hot day here in Phoenix, trying to run slower to keep the motor cooler and make my battery last longer, on a long-ish Freecycle pick-up run. Doing the exact same thing at full throttle did not have the same controller heating problems (although it certainly did heat the motor a lot more, as it had more load on it, and used battery faster).

If you're in colder areas, it may never be an issue, or you can ventilate the controller, with perhaps a temperature-controlled fan.

When running a mid-drive setup, it may not be an issue at all, as you can always just gear down the motor more before it enters the drivetrain, to compensate for the faster RPM it will have at a higher voltage.


--One other gotcha is that at higher voltages, the same controller FETs will have higher losses to RDSon/etc than at lower voltages, but this inefficiency may be made up for by the overall system efficiency at the higher speed--running the motor faster but geared down more means it will probably be spending a lot less time at low (inefficient and current-hungry) speeds, before reaching speeds at which it pulls much less current to do the same work.


pdf wrote:Well, color me dumbfounded. I am not sure why people have problems with the Stokemonkey setup.
Remember that my powerchair motor setup is not quite like a SM setup, as it's not driving the pedal crank directly, but rather a jackshaft that the pedal's chain happens to also be connected to (but still no FW on either one, so both drive each other). Also, the PC motor is capable of (at least) short bursts of power in the 150A+, 3500W+ range (possibly a lot higher, but that was perhaps the only folded-chainring event that I was able to record the current spike for). I can't even recall just at this moment if that was with the lower-power 300-350watt motor, or the bigger 600-650W one.

My pantleg issues are probably more because of it's semi-recumbent seating than anything else, as there's no chain guard on it and it runs for some length next to my leg. Problem was usually with wind catching it and pulling it in just below the knee area, on the seam, even with the end of it tucked into a sock or with a tie strap.

I daresay my experience is an exception rather than the rule, but I wanted to put the warning out there just in case. :)

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Re: mid-drive questions

Post by MitchJi » Jan 04 2011 3:58am

Hi Warren,
Warren wrote:A question for the electronic wizards. Is it always more efficient to run higher voltage?

I am thinking about going with a 36 volt, 30 ah pack, instead of 48 volts, and 20 ah. The lower motor rpm means I have more motor gearing options, with off-the-shelf bike sprockets and chainrings. Being able to run a bigger cog on the motor would be quieter, and mechanically more efficient. The lower motor rpm means the planetary gears should run quieter.

For a given watts/speed I would be pulling more amps from the pack, controller, and motor...electrically inefficient. But at the same speed on 36 volts, I won't be chopping the voltage back as much with the controller. Anybody know if that wouldn't that be electrically as efficient?...

But I was hoping it would turn out otherwise. 36 volts would just make my life easier. :-(
Some people have posted some pretty outstanding efficiency results with 36v systems. Matt's Catrike with an Astro 3220 gets about 11wh per mile and its a 44v nominal so I don't think the difference between 36v and 48v will make that big a difference so IMO if it makes things a lot easier I'd go with 36v. Neugart tech support told me that halving the speed of their planetary would make a "minimal difference" in noise.
Best Wishes!

Mitch


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Re: mid-drive questions

Post by pdf » Jan 04 2011 9:50am

OK. Tested my top speed this AM on about the only flat smooth section of my commute. It looks like 20.5 mph is about the top end at 15 amp. I did not do a rigorous test, but that is probably within 5% of what I would get by running the same course both ways and averaging.

Also, in terms of efficiency, I get between 1.8 and 2.2 mile/amp-hr at an average battery voltage of 37 volts or so. That is pretty good, I think. My commute is a hilly 13 miles round trip and I can do it twice without recharging with a 15 amp-hr battery, in case I forget. Which I used to do occassionally but nearly always remember to plug in now.

I think efficiency for an ebike in average use is dependent mostly on how much you can keep the motor in the high efficiency part of its performance curve. If you bog a motor down up a steep hill a lot or at speeds where air resistance is significant, your efficiency will suffer. I can see this on my watt-meter very easily. Note that even in the example with high current electric motorcycles you cited, the difference in power is only around 10% but the difference in voltage was around 30%. I think for practical usage, whatever system keeps your motor at its most efficienct part of the power curve is going to give you the most efficiency. All things being equal, the higher voltage will give you a higher efficiency. But that assumes an equal efficiency from the controller.

The way I operate my ebike, I use the throttle as pretty much an on-off switch. Particularly in the winter with heavy gloves, it isn't practical to tune the throttle very accurately anyway. What happens when I ride is that the current goes up and down, usually between about 8 amps and 15 amps, to match the load and motor speed. The bike speed doesn't change that much and my pedaling effort doesn't seem to either. It isn't like a motorcycle throttle where a little throttle change makes a significant difference in the speed. Of course, the motor is very much smaller than a motorcycle engine and due to the hilly terrain, I am pretty much going up and down the whole time. If you rode on a very flat smooth road for a long time, the throttle setting might make more of a difference when it came to equilibrium. As it is, even if I held the throttle constant at some intermediate setting, the bike speed be changing a lot due to the terrain.
-------------
Jamis Commuter 1.0/Xtracycle Stokemonkey 36V LiFePO4, 15 ahr
Giant Boulder 9C 8x8, 48v, 10 Ahr LiMn from ebikes.ca

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Re: mid-drive questions

Post by Warren » Jan 04 2011 12:13pm

Guys,

Thanks for all the great info.

I will be riding out in the country on smooth, rolling roads...very few stops. I plan to run it flat out, with a Ping 48 volt, 20 or 30 ah pack, CA set to 15 amps max., shifting to maintain the same cadence. My bike will be lighter, and more aero than a hybrid/extracycle, and running 28-40 mm wide slicks. I will be using the pedelec sensor, and brake switches. Don't want to put any undue strain on the planetary gears/drivetrain.

Sounds like I should have no trouble averaging 20 mph...40-60 mile...depending on which pack I end up with. Am I crazy to expect this kind of performance? I got 17 mph average for 15+ miles on a 24 volt, 10 ah, 250 watt max, hub motor, sit-up, comfort bike that I worked on for a customer. That was in freezing temps, with sleet and snow.

The motor, controller, pedelec sensor, brake levers, throttle, spare gears are on the way! Once I get all the hardware mounted, I'd like to at least test it on a trainer with some lead acids, to make sure all is working, before I order the pack. Let's see...pull the batteries from the wife's and my car...maybe the neighbor's cars too. Way too big to ride, but OK for a bench test. :-)

Warren

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Re: mid-drive questions

Post by pdf » Jan 04 2011 2:34pm

I am on an Xtracycle with a very upright rider position. If I can do better than 20 on my setup, you can easily do that as long as you are not running fat studded tires, which you aren't. About any setup will give you that so just get the speed in the sweet spot and you are good to go.

What motor/controller did you get? Let us know how it works out for you.
-------------
Jamis Commuter 1.0/Xtracycle Stokemonkey 36V LiFePO4, 15 ahr
Giant Boulder 9C 8x8, 48v, 10 Ahr LiMn from ebikes.ca

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Re: mid-drive questions

Post by katou » Jan 04 2011 2:40pm

PDF Wrote:
"1.8 and 2.2 mile/amp-hr at an average battery voltage of 37 volts"

37v at 1 amp for 1 hr = 37 watt hours
v x a x hr = watt hours

2 miles (average 1.8, 2.2) for 37 wh = 1 mile for 18wh

or 18 wh/mile

This is in line with the efficiencies I've noted for the better setups. A good ballpark for a well-running, efficient setup is 15-20 wh/mile from my reading.

For Matt to get 11 wh/mile, well, that is exceptional. I hope that when I get my RC setup on the road I can do half as well. I'm sure that most of his success is due to high quality machining on his bores, good bearings and a high eff. motor to start with. The rest is magic.

Katou

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Re: mid-drive questions

Post by MitchJi » Jan 04 2011 4:19pm

Hi Katou,
katou wrote:... A good ballpark for a well-running, efficient setup is 15-20 wh/mile from my reading.

For Matt to get 11 wh/mile, well, that is exceptional. I hope that when I get my RC setup on the road I can do half as well. I'm sure that most of his success is due to high quality machining on his bores, good bearings and a high eff. motor to start with. The rest is magic.
A lot of his success is due to the reclining riding position (his recumbent and the trike are both better than 15-20 wh/mile:
http://www.endless-sphere.com/forums/vi ... 0&p=291025
etard wrote:How does this trike compare to your original recumbent in terms of efficiency, power, and ride?
Matt wrote:Here are a few comparisons;

Actionbent Midracer--- 13wh per mile at 20mph.
CT700--- 11wh per mile at 20mph.
Midracer--- 48 pounds.
CT700--- 60 pounds? (still have to weigh it)
I'm sure he could do even better if he were driving through the gears as Warren intends to do.

Marcus sent me this via email about a Saturday ride on a Pi (I'm not sure if it was a 10ah or 20ah battery):
The attached elevation map encapsulates my Saturday ride: 26 miles, 6200' elevation gain total, averaging 18 mph.

This was done on a N.A. + CA legal Pi, e.g., 36V LiION, 500 Watt rated BLDC, 8 speed Shimano and a 44t front ring.
Image
Last edited by MitchJi on Jan 04 2011 4:28pm, edited 1 time in total.
Best Wishes!

Mitch


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Re: mid-drive questions

Post by Warren » Jan 04 2011 4:23pm

Katou,

"15-20 wh/mile'

Yes. This fits with what I have read.

pdf,

"What motor/controller did you get?'

MAC 350 front motor, and 25 amp Infineon controller with 6 IRFB4110 fets.

The recumbent is an old Linear, LWB folder, like this one.

http://www.flickr.com/photos/coalandice ... /lightbox/

The Linear has gone through several manufacturers, and refinements. The new ones from Bicycle Man are orders of magnitude better than the old one I bought used. But the beauty of the old ones is, they make great test mules, as everything is bolted on to a square extruded beam. The beam has flanges which everything clamps to.

For this build, it will have the cranks mounted on top of the frame beam, just behind the head tube. This will get me as far forward as possible, and allow the seat to be laid way back. Kind of like this.

http://www.bikeweb.com/node/302

If I like it, I will probably build something more durable.

Here is just one configuration I have put it in.

Warren
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Re: mid-drive questions

Post by Warren » Jan 20 2011 11:17am

I got my 350 watt MAC front motor, and Infineon controller with 6 (25a) IRFB4110 fets, from cell_man, Paul, the other day. Half way around the world, to my door, in a week and a half. What a world.

So now I need a battery pack. It still appears a Ping is my best choice for reasonable weight/price for low C draw, long endurance riding. The 48 volt, 20 Ah pack is his cheapest per kWh. But this quote has me worried.

"My ping 36v charges to 45-47 v depending on which charger I use. I don't recall exactly what the lvc cut off is, but it's pretty close to 36v. Maybe 34 or 35? So you'd get all 15 ah out of it. Most of the ride is done with the battery at about 40 v."

Since I am planning to run a Stokemonkey-style setup, with gearing limited to standard bike stuff, cadence becomes a concern. I have been figuring 48 volts (3 volts per cell) all along. But it sounds like, at least at the kind of C I will be pulling, the Pings run 10 % higher (3.3 volts per cell).

Ten per cent higher cadence is too much for me....48 volts was already pushing my limit. I know I will have to back off on the throttle setting. My question is this.

Which will be most efficient overall...to run a so-called 48 volt pack at 75% throttle most of the time, or run a so-called 36 volt pack at full throttle most of the time?

And yes...I realize I asked a very similar question before. :-(

Warren

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Re: mid-drive questions

Post by pdf » Jan 24 2011 3:49pm

Which will be most efficient overall...to run a so-called 48 volt pack at 75% throttle most of the time, or run a so-called 36 volt pack at full throttle most of the time?
Good question. I run a Stokemonkey myself.
Not sure I have the definitive answer, but using the simulator at ebike.ca, I did the following:
1) picked a random motor and controller
2) found the speed at max efficiency for 36V
3) made the battery 48v and tuned the throttle until I got the max efficiency at the speed found in 2 above.

The efficiency in the second case was virtually the same in both cases, maybe 1% less. Not sure this is the best test, but it's the best I can think of.
-------------
Jamis Commuter 1.0/Xtracycle Stokemonkey 36V LiFePO4, 15 ahr
Giant Boulder 9C 8x8, 48v, 10 Ahr LiMn from ebikes.ca

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Re: mid-drive questions

Post by Warren » Jan 24 2011 6:02pm

pdf,

"using the simulator at ebike.ca...efficiency in the second case was virtually the same in both cases, maybe 1% less"

So you are saying the model suggests that the 36 volt system at WOT, is at least as efficient as the 48 volt system, at the same speed. That was my guess.

I am sure that some controllers are more efficient than others, but my guess (based on my vast ignorance) was that the little extra heat loss from the higher current of the 36 volt system would be roughly equal to the losses in the FETs.

I suppose if I was trying to run huge power through those little wires the situation would be different. But then the motor, controller, and Ping pack wouldn't be up to that anyway.

Thanks, Warren

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Re: mid-drive questions

Post by pdf » Jan 25 2011 1:24pm

Warren,

Yes, you interpreted my somewhat screwed up message correctly. What I meant to say is
"using the simulator at ebike.ca the efficiency in the second case was virtually the same as that in the first case, maybe 1% less"

What I don't know is how much of the losses you mentioned are modeled and how well. So if there were conditions that are extreme in either case, it would probably not be a valid condition. As long as you are not subjecting the motor to excessive loads, I'd be the simulator results are probably reasonably accurate and the difference between the two senarios is minimal.

The one thing that struck me is that, on my system at least, it is pretty tricky to hold the throttle at a particular setting that is not all on or all off. What I do (because I have a system that works through the cranks) is to find a gear where I am going the correct speed with the trottle pretty much wide open. If I had to go a long way holding the throttle for a particular voltage, it might be tricky. However, the average ebike is not a muscle-bike and small perturbations in wind and grade will make the bike slow down and speed up anyway so even if you manage to hold the trottle in the same place, I would predict you would find the speed going up and down anyway. That is my opinion and worth what you paid for it.
-------------
Jamis Commuter 1.0/Xtracycle Stokemonkey 36V LiFePO4, 15 ahr
Giant Boulder 9C 8x8, 48v, 10 Ahr LiMn from ebikes.ca

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Re: mid-drive questions

Post by Warren » Jan 25 2011 10:21pm

pdf,

"What I do (because I have a system that works through the cranks) is to find a gear where I am going the correct speed with the trottle pretty much wide open."

Yes. That is what I will be doing.

Thanks, Warren

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Re: mid-drive questions

Post by Warren » Jul 27 2011 4:06pm

Guys,

I'm a little slow...OK, a lot slow. Anyway, I have finally gotten the bike to the point that I am wiring things up. I bought a bunch of Anderson Powerpole 15/30/45 amp connectors, and the tool. I know the hotrod types here think they are too wimpy, but I see Ecospeed, and several others are using them. I don't plan to run more than 15 amps through anything, and the controller limit is 25 amps.

I have several questions for the electronic wizards here. The Infineon controller, from cell_man, has a little red wire from the controller wired to the positive wire coming in from the battery. My understanding is that putting a switch in this wire will allow shutting down the controller. Is this correct?

From the size of the wire, I'd guess it is only turning on the FET's, and is not carrying any real current. Would the smallest spst toggle switch from Radio Shack be sufficient?

I will be putting a 30 amp spade fuse, in an Anderson inline fuse holder. Is this sufficient? Any reason to run the 40 amp that came with it?

This fuse holder setup actually fuses both the positive, and negative lines from the battery. Any pros/cons to running them both?

CA suggests a switch after the fuse, to cut off power to the CA. Would a 20 amp, 125 volt, 3/4 hp, spst switch be sufficient, as long as I don't switch it while the motor is running?

How about just unplugging the Anderson connector? Seems like it works pretty nicely. Would it be up to repeated connecting/disconnecting?

Last question. With the little switch to the controller turned off, would there be any arcing when I plug things up. I've heard on the high voltage systems, you need to put something across the plug to prevent arcing. Will this be necessary with 36 volt, 30 amp Ping pack, and my little controller?

Thanks in advance, Warren

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Re: mid-drive questions

Post by amberwolf » Jul 27 2011 4:41pm

Warren wrote:I bought a bunch of Anderson Powerpole 15/30/45 amp connectors, and the tool. I know the hotrod types here think they are too wimpy, but I see Ecospeed, and several others are using them. I don't plan to run more than 15 amps through anything, and the controller limit is 25 amps.
They'd be fine for anything under their rating. If you got the 15A version, that's at the limit, but if you got the 30 or 45A contacts, you're well within their limits.

Part of the problem I think some of those having melted PPs are seeing is the very thick wires going into the shells are not allowing the contacts to float inside them, and so they can't make flat parallel contact with the other end. They're forced to some angled contact, so only an edge or even a point is making contact, and the resistance is very high, so they get hot, and melt the shells. As soon as that starts happening, the amount of contact (if any) is a wild guess that probably changes with temperature.

My understanding is that putting a switch in this wire will allow shutting down the controller. Is this correct?
Yes.

Would the smallest spst toggle switch from Radio Shack be sufficient?
Yes. I doubt there is more than a quarter amp on that wire, worst case.
I will be putting a 30 amp spade fuse, in an Anderson inline fuse holder.
If you are sure that you don't want to ever pull more than the 25A controller limit for any length of time, 30A or less would be good. The idea is to fuse just above what your max allowable current should be, so that if it goes above that for any appreciable time it blows and saves your system.

If it's a FET short or motor short causing FET overcurrent, the fuse won't blow in time to save anything inside the controller anyway, so that doesnt' matter, but if it's a wiring short between controller and battery, for instance, or the short inside the controller, it'll save the battery and the wiring between fuse and battery.

Fuse ought to go as close to the battery as possible, so that any shorts to frame or elsewhere would be beyond the fuse.

This fuse holder setup actually fuses both the positive, and negative lines from the battery. Any pros/cons to running them both?
So there are two separate fuses? Theoretically, a short on either line would still blow just one fuse, so there's not really a need for two. But if your battery could theoretically get shorted to the frame at some place other than pack ends (mid-pack, for instance), having a fuse at each end could prevent a lengthy short between that mid-pack point and either end. Without a fuse on each end, the mid-pack short to the unfused end would go unchecked until something else burned thru.

CA suggests a switch after the fuse, to cut off power to the CA. Would a 20 amp, 125 volt, 3/4 hp, spst switch be sufficient, as long as I don't switch it while the motor is running?
Is that 20A at AC or DC? Need to be sure you rate it at DC, at the DC voltage you're using. The current rating ought to be higher than the max current you're going to be pulling thru the switch.
How about just unplugging the Anderson connector? Seems like it works pretty nicely. Would it be up to repeated connecting/disconnecting?
THey're made for lots of cycles, and are cheap enough to replace when you do wear one out. I disconnect/reconnect my PP and MP andersons for charging each time, so that's a minimum of one cycle per day. I also disconnect my 12V system's PPs at each stop on a trip, as I have no switch on that system, and don't want someone to accidentally turn on one of my lights and leave it on, killing the 12V battery. (I should put in a switch but time hasn't permitted).

With the little switch to the controller turned off, would there be any arcing when I plug things up.
[/quote]
Probably, but you may not notice it.

Warren   100 kW

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Re: mid-drive questions

Post by Warren » Jul 29 2011 9:49am

amberwolf,

" If you got the 15A version, that's at the limit, but if you got the 30 or 45A contacts, you're well within their limits."

Actually, the contacts are the same on all three. It is only the crimp lug, where the wire goes in, that is different. I got a bag of 15's, and a bag of 30's. Will probably order a bag of 45's, as the 10 gauge wire on the fuse is a real squeeze into the 30 amp crimp.

And yes, they have a double fuse.

http://www.powerwerx.com/fuse-holders-f ... gauge.html

The wires are tightly zip tied together, probably to avoid that contact twisting you mentioned. I will be doing this to all my connections also, to hopefully avoid twisting.

Warren

Warren   100 kW

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Re: mid-drive questions

Post by Warren » Jul 29 2011 9:56am

Dang! I just found these.

http://www.andersonpower.com/products/p ... rpole.html

They would eliminate any concern over twisting, and keep all the other neat Powerpole features. 30 amp rating would be plenty for me.

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amberwolf   100 GW

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Re: mid-drive questions

Post by amberwolf » Jul 29 2011 3:49pm

Are those new? I don't recall ever seeing them in my many explorations of their site.

And it appears you're right about the current rating. My bad. :(

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