Hi, I'm new to the forum. I've read through the whole MX650 mods thread but didn't really find an answer to what I'm thinking of doing. I recently acquired a used MX500 with dead batteries but in otherwise excellent shape. I want to do the upgrade to 750W but I'm not really interested in doing the upgrade to 48V (don't want to worry about heat/buying new charger/buying 60amp switch/etc). Here's the setup I'm thinking of doing (from TNC):
-750W Motor - 36 Volts (Style: MY1020)
-36V Controller (Model CT-660B9) <--so I can still use brake cutoff
-3 X 12V18ah SLA batteries <--for longer range
I'm just wondering if I will notice some decent improvement in torque and range with this set up vs the stock 500 or 650 for that matter. I weigh about 190 lbs and am not interested in speed (17mph is fine with me). I just want to be able to ride around campsites and such with decent torque to get over small hills (and maybe pop some wheelies). I know everyone seems to think 48V over-volting is the way to go, but is sticking with 36V and uping to 750W with a controller to handle it going to show improvement over stock? thanks
It should improve it a little, but IMO that is a lot of money for an extra couple hundred watts. Amps is what makes heat more than voltage. And motors like to spin.
For example if you volt up and gear down a 48v 15a setup, it should run cooler than (and outperform) a 36v 20a setup even though the total wattage and mph are the same. And you're only out the price of a sprocket and 1 extra lead brick. No motor or controller to buy (you could even regear without touching the sprocket by swapping to a smaller rear wheel).
MECI has some cheap high tooth count sprockets, if you need hill power maybe one of those would work? Not sure as I am not familiar with mx components.
Think of the motor's wattage rating as the max wattage or power that you can run through it. Running a 500 watt 36v vs a 750 watt motor could be the exact same torque, it just means the 750 could potentially handle more. You will get the extra torque from the extra amps that the controller will give. If the controller is agressive enough and pulls too many amps for the 500watt then getting the 750 could be good, but if the controller isn't all too aggressive then the 750 may be pointless.
I would aggree that overvolting and regearing could be a good option. Cheaper, and then you can always put the original sprocket back on if you feel like getting some more top speed.
Thanks for the advice. I guess I'm just gonna go for the over-volt. I've been thinking of what I want to do and have come up with this:
$35 - 48V Controller (Model LB37) Yi-Yun Brand Controller
$75 - 36V 750W motor (~1000W @ 48V)
$92 - 4 x 12V12Ah battery
$40 - 48 Volt XLR Charger
$10 - Twist Throttle Cable with 48 Volt LED Meter
Not bad for under $300. Any thoughts on this set up. I know the LB37 is rated for >800W motors but this shouldn't matter because the 750W acts like a 1000W at 48V, right? Any other general thoughts on this setup. Thanks!
That could work. Honestly though for a $300 budget, I myself would retain the stock controller and motor and spend it all on (4) 6s 5ah lipo packs and an accucel-6 charger. That comes in right around 300 with shipping. This 2s2p 44.4v 10ah lipo pack will give more accel and range than a 48v 12ah sla pack because of V sag and peukurt, but the trade off is the fire risk with lipo.
The components inside your 36v controller are probably 63v and if so you could safely run at 48v of lead or 12s lipo. Only thing is the low voltage cutout wouldn't be right. Same with the throttle, it will probably work fine but the lights won't be right.
Wubba I think you could have one pretty sweet setup there. There are a few things I would like to mention though.
-You are correct in that overvolting a motor can make it act similar to one with a higher power rating, but even though it will act similar it isn't as strong. What I mean is if you have a 750 watt motor rated at 36 volts, once you go to 48 volts it will still take the same amps, but now multipy those by 48 instead of 36 (watts = voltage x amps) So the motor could actually be pulling 1000 watts, but it still isn't rated for it. So using a controller that sends higher amperage could possibly be a little bit of an issue depending on just how many amps it gives.
The other thing I would say is check the rpm on the current motor, check the rpm of the motor you are looking at, multiply that rpm by the amount you are going to overvolt, and realize that you may need to regear. I would expect to have to change a sprocket.
Last thing to consider, overvolting is good for increasing speed, can be a cheaper option, but it doesn't increase torque, and is somewhat of a risk. So if you aren't worried about extra speed, then you may want to consider not overvolting.
You could always get 3 batteries get it running, ride it a while, and then see what you like and what you don't, and then change what you don't like. In general that method seems to work best for modifying most things i think.
Overvolting doesn't increase torque? So when I pin it from a stop with a 60v 20a bike its the same torque after I step it down to 24v 20a because the amps are the same right? The ONLY benefit is an increase in top speed, no acceleration benefits? Remember, power is a function of torque.. they both go up and down together.
I'm not saying my shopping list is right for anybody else.. just saying thats what I would do with my 300 bucks. Imo thats a lot of cash to blow on a little razor. You want to make sure you're not buying replacments for something that would've worked fine to begin with.
And just for the record I'd bet your motor will have no problem with the extra power. I ran a 24v motor/controller on more than double the voltage before without issue. Just be aware of the components and use some common sense. Take it easy when applicable, like on steep hills.
And if the motor does somehow go out, then you can upgrade. Like you were going to anyway.
A 12ah 48v SLA pack is heavy and bulky also.. if that is an issue for your bike. The 44.4v 10ah lipo pack would be 6" x 4" x 4" and around 7 pounds total!!!!!
I've gone ahead and ordered all of the parts I listed above. I got a good deal from TNC with combined shipping. I have another question though. Now that I've upgraded my system to 48V with a 50A controller (LB37), what is the proper fuse to use? The stock MX500 uses an inline 30A blade type fuse. Do I need to upgrade to a 50A? Will a Maxi blade type fuse work (I noticed they're rated for 32V), or do I need and AGU style fuse? I noticed on the MX650 thread that they mention using a 50A fuse for their 100A controllers (half the rating). Does this mean my existing 30A is suitable for my 50A controller (more than half the rating). Thanks
I have received all the stuff I ordered and have the bike about 90% assembled. Man that motor screams! I'm having one (possible) major problem. I bought a 48V 2A charger off eBay48V Volt battery Charger for Electric Scooter ATV BC05:eBay Motors (item 250451914369 end time Sep-22-09 20:19:05 PDT), but I think it may be "over-charging" my batteries. I received the (4) 12V 12ah today and wired them up in series on the bike. I plugged in the charger and after about 20 minutes, I could hear the batteries boiling and fizzing (although they did not get hot at all). I'm wondering if this is normal for new batteries. One thing that concerns me is that the charger puts out about 58.4V when charging. Does this seem a little high to anyone? I've read that SLA batteries will boil off the electrolyte around 14.3V. Does anyone know what the proper charging voltage should be for a 48V system (seems like it should be more like 54-56)? Thanks
The peak voltage is about right but it sounds like it might not be kicking down into float mode. If that is the case its bad, but I would expect them to get hot if its overcharging them..
I individually balance charge mine with 14.7v each brick (58.8 total), but they go down to like 13.6v each a few minutes after the chargers shut off. I've never heard bubbling or fizzing, but maybe I'm just not listening as well as you? I'll put my ear to them next charge.
You're skeeering me, I ordered a $20 48v ebay charger a week back. I've got my fingers crossed that I won't have problems!
I also have a 36v motor running on 48v, so I know what you mean by 'screams.' When they spin out at the new higher max rpm it sounds good the first time you hear it! And its not just about the higher max speed.. with lead v.sag can be a huge issue with acceleration. When you up volt a brick, no matter how much your Vsag is, it will never sag all the way down to where you were before.
Lucky for us right now the 48v parts are 'commodity' components. 60 or 72v parts are coming down in cost, but they are still relatively uncommon and expensive. Makes good sense to take advantage of the commodity status of these 48v components at upgrade time.
Kind of like LCD TV's or monitors for computers. If you bought a 22" or 24" flat monitor a few years ago you PAID dearly for it, now its the 'sweet spot' or best bang for buck in sq. inches. If you want to get the best bargains you have to flow with the market, not fight against it. Anyway, obviously I think you made a wise choice upvolting, I'll stop rambling now.
sorry, not trying to scare you. I'm going to do some more testing today. I'm hoping it's just that they overfill the batteries with electrolyte at the factory and that the bubbling and fizzing sounds are just the batteries releasing gasses to get to a comfortable equilibrium condition. I might also try discharging the batteries for a while (they are definitely full now @ ~53V when taken off the charger) and then recharge them. I did hook up the multimeter while charging for a few minutes. The charger outputs a really high pitched hum until the voltage reaches the ~58.3V maximum, then the hum stops (I'm guessing the charger is switching into float mode?). Anyone else have this issue? I've read where people have experienced this before and after a few charge/discharge cycles it went away. Again, since the batteries/charger/controller/wires aren't getting hot (or even warm for that matter), is it safe assuming they're not overcharging or being damaged? thanks for all the help so far.
For $20 I'm not too worried. Like I said, I'm stoked the 48v stuff is this cheap now..
You know what I use an accucel-6 to balance charge our sla. I don't think its a constant voltage charger like yours may be, so don't take my word for it 14.7v is normal for a CV charger.
Re: MX500 to 750 only 36V (NOT 48V)? 
