increase volts, how and what will this do.

[sloth1178]

I've got a bafang rear hub motors rated at 36v 250w.

I'm interested in this add on
http://www.bmsbattery.com/111-12v

Adding this to my 36v battery I will get 48v. Is this all I need to do or will I also have to change the controller which is rated to 36v. If so can you recommend one please.

Also what will he the result of this mod? More power? More speed?

Thanks very much.

 

[Deleted member 4366]

You'll need a new controller too. I think you'd be better off getting a proper 48v battery. Charging and installation will be easier.

Increasing the voltage makes the motor spin faster and increases the torque. The down-side is that the motor will get hot if it struggles up a hill.

 

[danielrlee]

Hi Sloth. Have you confirmed yet that there is nothing else limiting your speed? If there is, no amount of extra volts will help.

Assuming there isn't any artificial speed limit in place, then yes, raising the voltage to 48v will raise your top speed by 33%. Whether your controller can take the extra voltage is another matter. You would need to look inside the controller to check the rating of a few components before knowing for sure.

Another question: Do you know how many amps your controller is currently operating at? A certain amount of power will be needed to reach the 20mph you appear to be aiming for. Also, what is the voltage of your 36v battery when hot off the charger?

EDIT: Scrap that. I've just done the maths and although not definate, I think your controller will likely need replacing.

 

[sloth1178]

Hi Sloth. Have you confirmed yet that there is nothing else limiting your speed? If there is, no amount of extra volts will help.

Assuming there isn't any artificial speed limit in place, then yes, raising the voltage to 48v will raise your top speed by 33%. Whether your controller can take the extra voltage is another matter. You would need to look inside the controller to check the rating of a few components before knowing for sure.

Another question: Do you know how many amps your controller is currently operating at? A certain amount of power will be needed to reach the 20mph you appear to be aiming for. Also, what is the voltage of your 36v battery when hot off the charger?

EDIT: Scrap that. I've just done the maths and although not definate, I think your controller will likely need replacing.

Thanks very much for your detailed reply.

I'm still unsure what is actually limiting the top speed. I think I have exhausted the display controller by playing with all of the settings which didn't seem to affect the speed.

I'm a total noob when it comes to these bikes lol.

I do have lots of 3s lipos (2200 to 5000) laying around and a couple of 2s (1000mah). Anything I can do with these to test anything?

What would I be looking for in the controller?

I have heard of soldering the shunt... Or something like that, what is this and what will it do for me?

Many thanks again for your help.

 

[Deleted member 4366]

You can connect 12S direct to your controller, but not a 48v battery. 12S should make your motor spin 20% faster without a speed limit. A different controller will show whether you have a limit or not.

 

[danielrlee]

Thanks very much for your detailed reply.

I'm still unsure what is actually limiting the top speed. I think I have exhausted the display controller by playing with all of the settings which didn't seem to affect the speed.

I'm a total noob when it comes to these bikes lol.

I do have lots of 3s lipos (2200 to 5000) laying around and a couple of 2s (1000mah). Anything I can do with these to test anything?

What would I be looking for in the controller?

I have heard of soldering the shunt... Or something like that, what is this and what will it do for me?

Many thanks again for your help.

What d8veh has said in the previous post is correct. 48v is a nominal rating - fully charged, you're looking at 57.6v which is likely more than a 36v controller can handle. The only way to tell for sure would to be to visually identify the rating of the input capacitors and FETs contained within.

If you can find a way to connect one of your 2S lipo packs in series with your 36v battery, you will be able to find out once and for all if there is a soft limit in place. If the motor runs quicker, the only limit is that of the operating voltage. Before doing so though, we need to know the voltage of your 36v pack so that when combined with the lipo, doesn't blow your controller. I suspect that hot off the charger it reads 43.2v.

Modifying the shunt will alter the power of the motor (acceleration) at the expense of range.

 

[sloth1178]

You can connect 12S direct to your controller, but not a 48v battery. 12S should make your motor spin 20% faster without a speed limit. A different controller will show whether you have a limit or not.

OK cool.

So if I bought a different controller and decided to stay at 36v but more amps, would this keep the topend the same but more torque?
Also with a new controller would I still be able to use my display? Is it all plug and play to a new controller?

 

[danielrlee]

Just to confirm, is this your bike?: http://www.voltbikes.co.uk/alpine-x-electric-mountain-bike.php

It says it's a lithium polymer battery which I wasn't expecting and possibly throws the voltage calculations out of whack. We really need to confirm the fully charged voltage of your battery before recommending any further course of action.

 

[sloth1178]

What d8veh has said in the previous post is correct. 48v is a nominal rating - fully charged, you're looking at 57.6v which is likely more than a 36v controller can handle. The only way to tell for sure would to be to visually identify the rating of the input capacitors and FETs contained within.

If you can find a way to connect one of your 2S lipo packs in series with your 36v battery, you will be able to find out once and for all if there is a soft limit in place. If the motor runs quicker, the only limit is that of the operating voltage. Before doing so though, we need to know the voltage of your 36v pack so that when combined with the lipo, doesn't blow your controller. I suspect that hot off the charger it reads 43.2v.

Modifying the shunt will alter the power of the motor (acceleration) at the expense of range.

Brill, I think I understand now.
I'm starting to think now that rather than spending loads of money to get higher topend the best thing to do would be to do a free mode and do something to the shunt (what ever that is lol).

Is there a limit to how far I can go or is it a fixed amount or.. I dunno lol. Any guides on what to do to this shunt thingy

 

[sloth1178]

Just to confirm, is this your bike?: http://www.voltbikes.co.uk/alpine-x-electric-mountain-bike.php

It says it's a lithium polymer battery which I wasn't expecting and possibly throws the voltage calculations out of whack. We really need to confirm the fully charged voltage of your battery before recommending any further course of action.

I will test and find out the voltage, I'll have to try and find a volt meter somewhere

Yes, sorry, it is a lipo pack.

 

[sloth1178]

[quote="danielrlee, post: 233090, member: 8220"
Modifying the shunt will alter the power of the motor (acceleration) at the expense of range.[/quote]
I like this idea

 

[Deleted member 4366]

You don't need to measure the battery voltage. It'll be 42v.

You could use a 2S lipo just to test the speed of the motor. It's best to do it with the wheel off the ground. See what the maximum speed is, then add in the 2S pack to see if the wheel spins 20% faster.

Soldering the shunt gets you more torque, but not more speed. If you do decide to solder it, try about 20% of its length first.

 

[sloth1178]

You don't need to measure the battery voltage. It'll be 42v.

You could use a 2S lipo just to test the speed of the motor. It's best to do it with the wheel off the ground. See what the maximum speed is, then add in the 2S pack to see if the wheel spins 20% faster.

Soldering the shunt gets you more torque, but not more speed. If you do decide to solder it, try about 20% of its length first.

Sorry, what do you mean by 20% of its length? Total noob here. If I find the shunt do you mean put globs of solder 20% across its length making it much fatter on that bit? If so how big a glob should it be. Sorry for being thick.

 

[sloth1178]

You don't need to measure the battery voltage. It'll be 42v.

You could use a 2S lipo just to test the speed of the motor. It's best to do it with the wheel off the ground. See what the maximum speed is, then add in the 2S pack to see if the wheel spins 20% faster.

Soldering the shunt gets you more torque, but not more speed. If you do decide to solder it, try about 20% of its length first.

Also how will I know how far I can go without killing anything? If I solder 20% and it feels good can I solder the whole thing? Bigger and bigger. Can of worms me thinks.

 

[Deleted member 4366]

How much you solder depends on how much risk you want to take of having to buy a new controller or motor. You need a wattmeter to tell how far you've gone, and you need to know your start point too. Without that, you have to stick to the minimum.

Some controllers have solid state shunts that can't be soldered, but there's still things you can do.

If you're lucky, it'll be like this:

Before



After

 

[sloth1178]

How much you solder depends on how much risk you want to take of having to buy a new controller or motor. You need a wattmeter to tell how far you've gone, and you need to know your start point too. Without that, you have to stick to the minimum.

Some controllers have solid state shunts that can't be soldered, but there's still things you can do.

If you're lucky, it'll be like this:

Before



After

Thanks very much. Exactly what I was looking for. With just that little bit of soldering how many more amps did this give you? Also was it very noticeable on the bike and in what situations?

 

[awol]

Thanks very much. Exactly what I was looking for. With just that little bit of soldering how many more amps did this give you? Also was it very noticeable on the bike and in what situations?

I soldered my controllers shunt as in the photo's and the amps increased about 4or5 amps which made a noticeable difference.

 

[Deleted member 4366]

The one in the photos increased from 15 to 18 amps, which gives a 20% improvement in torque. This allowed it to climb 20% steeper hills, and gave it better acceleration. It doesn't change the top speed unless your motor doesn't have enough power to reach its top speed. It would also deplete the battery up to 20% faster.

Your average 10ah battery can only give about 18 amps, so be careful not to go further than that unless you have a better battery.