Opinions about overvolting my 36v motor with a 48v battery?

[kmxtornado]

I've read that I can overvolt with a battery 1.5x the size of the motor. I've recently done it on my mini escooter and it's worked wonders. Curious if I can do it on my full size diamond frame upright bicycle that I've already put a conversion on. The bike we're talking about is this one:
http://www.youtube.com/watch?feature=player_embedded&v=NR5dYytiIcA. I'm sure there are technical details that I should be aware of that make this true/false. Can you please advise me here?

I have a Mini Might 36v motor from Hitekbikes:
http://www.hightekbikes.com/geared-hub-motor-kits.html

And a 36v 10ah LiFePo4 battery from the same retailer (whom I'm plenty happy with by the way), but I'm thinking of ditching the battery for a 48v 10ah one that'll give me a boost in power and top speed. Forget the "Why are you doing this?" questions. Please just discuss any concerns I should be aware of as far as the compatibility. I pedal through every hill and don't rely on the motor/battery alone to take me up inclines. I won't be at top speed the majority of the time. It's just nice to be able to go in fast bursts every so often. If I replaced my 36v battery with a 48v will I blow up my motor in no time?

Your thoughts are welcomed. Thanks in advance for your input. Oh and how much faster can I expect to go if I used a 48v battery if I'm now going 20mph max using the 36v one?

 

[dogman dan]

Not likely to damage the motor, but the extra wattage could heat the motor faster going up steeper hills. Don't go and upgrade the amps at the same time, and you should be ok. Typically about 4 mph faster.

 

[Drunkskunk]

Why are you doing this??
....couldn't resist.

Go for it. It should be fine. A few risks, so just be aware of them.
1) the motor can overheat faster with the bigger battery. Just be contious that you can over heat it faster than you could before.
2) the controller might not handle the higher voltage. most will, a few won't. but you can verify the capacitors are rated for 63 volts before you hook it up.
3) The LVC will be for the 36 volt battery, so you can damage the 48 volt if you let it get too low. Just be aware that the saftey net is off.
4) The EV grin you suffered at 36v may now become permanent.

 

[motomech]

I've read that I can overvolt with a battery 1.5x the size of the motor. I've recently done it on my mini escooter and it's worked wonders. Curious if I can do it on my full size diamond frame upright bicycle that I've already put a conversion on. The bike we're talking about is this one:
http://www.youtube.com/watch?feature=player_embedded&v=NR5dYytiIcA. I'm sure there are technical details that I should be aware of that make this true/false. Can you please advise me here?

I have a Mini Might 36v motor from Hitekbikes:
http://www.hightekbikes.com/geared-hub-motor-kits.html

And a 36v 10ah LiFePo4 battery from the same retailer (whom I'm plenty happy with by the way), but I'm thinking of ditching the battery for a 48v 10ah one that'll give me a boost in power and top speed. Forget the "Why are you doing this?" questions. Please just discuss any concerns I should be aware of as far as the compatibility. I pedal through every hill and don't rely on the motor/battery alone to take me up inclines. I won't be at top speed the majority of the time. It's just nice to be able to go in fast bursts every so often. If I replaced my 36v battery with a 48v will I blow up my motor in no time?

Your thoughts are welcomed. Thanks in advance for your input. Oh and how much faster can I expect to go if I used a 48v battery if I'm now going 20mph max using the 36v one?

Forget the "Why are you doing this?" questions. Please just discuss any concerns I should be aware of as far as the compatibility..

Getting a little bossy aren't we?

Why are you doing this? Posting this question that is. There have been numerous discussions concerning this that you have been in on.
Oh well, I like talking about mini-motors and perhaps there are some noobies wondering about this at the moment, so here goes.
Judging by the posts on the Amped Bikes forum, at least half the conversions using the MXUS geared mini-motor start out at 48Volts. I did, and 1000 miles later, the motor runs fine. With the stock 17 Amp controller, on the flat, no wind, no pedal, I see 23 to 24 mph. That is a MTB, 26" wheels, road tires and a bike/rider weight approaching 300 lb.s.
The more accurate question would be; How much power can a 3 Kg. geared motor sustain before damage occures and how would be the nature of that damage?
And to answer that, we need to look at the whole picture, which is Wattage[V X A = W]
The MXUS has been tested to destruction, by Mukeefer. I don't remember the exact figures, but I think he had taken it up to 18S Lipo and Amperage up in the high 20's. He was hitting speeds well into the 30's mph, so at least 1700 Watts sustained. He didn't elaborate on what happened to the motor, but we know from others, most notably Russell with his smaller Bafang, that the Halls, or more specifily, the Hall wires are the most vulnerble items. Then probably the Phase wires would melt. Strangely enough, although the MXUS gears have been described as "delicate", we haven't seen broken gears yet.
Lately, I've been running the MXUS on 12S[44.4V nom.] and 23 Amps[38 peak!], so peak wattage in the range of 1000 Watts, without issues. But this is light duty riding, no long sustained hills or high ambient temps. The steepest hill around me is 12.5 % and a 1/2 mile long. Intsead of the struggling[with me pedaling for all I'm worth]at 9 mph, it charges up at 13-14 mph[still pedaling]. At the top, the motor isn't even warm.
So to answer the original question, yes, 48 Volts with the stock controller, is well within the capibilites of the MXUS geared motor.

 

[kmxtornado]

Not trying to be bossy at all. Sorry if it came off that way. Just wanted to keep the topic on track. Perhaps putting my statement out there just made everyone more curious. So first off, this is why I want to do it:

1. Just because. I've got the mod bug. I mod everything in my garage: recumbent tricycles, bicycles, motor scooters, electric scooters and now electric bikes. I guess it's a hobby and I love making things "better" than they were.

2. Spoiled by the electric assist of my 36v setup already and I'm just greedy. I want more. I also got spoiled by overvolting my mini foldable escooter. The benefits were amazing when I went from a 24v SLA to a 36v LiFePo4 battery. The results were just awesome and I'd like to mimmick it on the upright standard DF bike.

3. The benefit of the ebike now is that I can go the same speed as I can while pedaling hard except w/o pedaling and sweating. I can wear regular clothes when riding w/o looking like I need to hit the showers when I arrive at my destination. It would just be nice to have the ebike go faster than I can push it as a Human Powered Vehicle.

I gotta look up what Phase wires are. 12.5% grade is fairly steep! I don't think I'll be going that much and I'll always be pedaling so I'm hoping the over heating of the motor won't be a problem. We got crazy hills here, but most of them aren't very long. More like rolling hills than mountains.

Why are you doing this??
....couldn't resist.

Go for it. It should be fine. A few risks, so just be aware of them.
1) the motor can overheat faster with the bigger battery. Just be contious that you can over heat it faster than you could before.
2) the controller might not handle the higher voltage. most will, a few won't. but you can verify the capacitors are rated for 63 volts before you hook it up.
3) The LVC will be for the 36 volt battery, so you can damage the 48 volt if you let it get too low. Just be aware that the saftey net is off.
4) The EV grin you suffered at 36v may now become permanent.

Thanks for the quick "to-the-point" answers with a bit of humor.
2) How do I verify the capacitors are rated for 63 volts? And why 63v? Aren't I going for 48v?
3) I gotta look up what LVC is.
4) I'm all for it.

Not likely to damage the motor, but the extra wattage could heat the motor faster going up steeper hills. Don't go and upgrade the amps at the same time, and you should be ok. Typically about 4 mph faster.

Only 4mph faster? Ugh. That's 20% which is quite high, but at $450 for the 48v 10ah LiFePo4 battery, that's pretty steep. I was hoping to get at least 26-28mph. I'm 145lbs. The bike's a smaller frame, Trek 700 with mountain bike tires.

 

[neptronix]

Do it.
If your controller blows, get one that can handle it.
If your tiny little motor blows, get a bigger one that can handle more power.

 

[dogman dan]

About 4v per 12v added has always been my experience. Not much more unless the motor winding is very fast to begin with, then maybe 5 mph more per 12v.

You want real speed, you need a new motor made to take a bit more wattage, like a Mac 6t or 7t. Then 48v will get you to 30. I wouldn't advise 60v on the tiny motor unless rides are very very short.

63v caps in "48v" controllers because 48v lifepo4 may charge to 60v. Open the controller, look for little cans with numbers on them. Likely they will say 50v or 63v.

LVC is low voltage cutoff. Set at perhaps 32v on a 36v controller, it would not be high enough to save a 48v battery with no bms.

 

[dnmun]

yes, you do not want a 48V controller with a 48V lifepo4 pack.

you can open the controller and adjust the input power resistors if needed, and all the 36V controllers have 63V caps.

there is another thread with sun-thing lifepo4 packs really cheap.

http://www.ebay.com/itm/LiFePO4-48V-20AH-Battery-5A-Charger-BMS-Rechargeable-By-Sea-7-8-Weeks-E-Bike-New-/130642199626?pt=AU_Electronics_Batteries_Chargers&hash=item1e6ae1c44a#ht_2111wt_922

 

[wesnewell]

The motors don't care about voltage. 36V@40A is the same as 72V@20A as far as the motor is concerned, 1440W from each. As for the motor, your only concern is how many watts you can put into for how long before you burn it up. As long as your controller will accept a 48V pack, there shouldn't be a problem. The only down side would be that the 36V controllers lvc will be too low for a 48V pack, so you can't count on it to protect from over discharge unless you change it. Probably not a problem if you plan on using a pack with a bms, but will be if not. I just use a voltmeter to monitor my voltage using lipo. Most controllers LVC are set for SLA batteries anyway, and are pretty much useless with lithium unless configure you lithium pack to work with the set lvc or can change the lvc. I don't put more than 4 times the rated watts into my motor for more than a couple of minutes and it's never been a problem.

 

[dnmun]

yes, i am talking about lifepo4. a 16S pack can ideally discharge down to about 32V so a 40.5V LVC on a 48V controller will restrict the amount of power your 48V lifepo4 pack can deliver. so 36V controller unless you can reprogram the 40.5V LVC of the 48 volt SLA model.