Just wanted to ask how many of you are running bike on a 48 volt battery? I use a 36 volt and I am very happy with it however, I wondered if I should go for 48 volt on my next conversion.

 

Any thoughts?

I don't think there is anything "magical" about them, just the same cells in a different layout. Depends if you are heavy, climbing steep hills or towing or want to go faster. Is there any area you want to improve on your existing conversion ?

Just wanted to ask how many of you are running bike on a 48 volt battery? I use a 36 volt and I am very happy with it however, I wondered if I should go for 48 volt on my next conversion.

 

Any thoughts?

48v is more efficient, gives you more power and more torque. 36v is crap by comparison.

My xf07 hub wheel is amazing. I don't need more power. I wonder if there is any point in 48v. I guess hill climbing is the biggest benefit.

48v is more efficient

 

I could understand that with a 201 rpm @ 36v hub motor winding compared to a 201 rpm @ 48v hub motor winding, you are getting more power at a lower current, so more efficient.

 

But if you run a 201 rpm @ 36v motor at 48 v with a 26", 700c or 29" wheel and restrict it to 15.5 mph won't it be running at a lower point on the efficiency curve ?

Edited March 5, 20251 yr by Peter.Bridge

Anyone ever bought one of those 48v batteries off Amazon for £90 Ish and run.

I worry those are the batteries that cause problems?

I could understand that with a 201 rpm @ 36v hub motor winding compared to a 201 rpm @ 48v hub motor winding, you are getting more power at a lower current, so more efficient.

 

But if you run a 201 rpm @ 36v motor at 48 v with a 26", 700c or 29" wheel and restrict it to 15.5 mph won't it be running at a lower point on the efficiency curve ?

I already explained that in another thread a week ago or so. 48v gives more power and torque than 36v with the same current, so the motor will turn faster on the same hill, preventing it from struggling in an efficient way. That's the general case. There will always be something specific or unusual where one will be more efficient than the other.

 

Losses are related to the square of the current, so running with 30% less current for the same power from 48v will always be more efficient. That applies to battery internal losses as well as external ones.

I already explained that in another thread a week ago or so. 48v gives more power and torque than 36v with the same current, so the motor will turn faster on the same hill, preventing it from struggling in an efficient way. That's the general case. There will always be something specific or unusual where one will be more efficient than the other.

 

Yes - I remember.

 

So if a 36v hub motor has a "no load" max speed of 21 mph (say) and a restricted speed on the flat of 15.5 mph, it is running at 74% of its no load speed, which will usually be around peak efficiency ?

 

If you then use a 48V supply on the same motor then its "no load" max speed will be 28 mph. If it is restricted to 15.5 mph then it is running at 55% of it's no load speed, which will be less efficient ?

Anyone ever bought one of those 48v batteries off Amazon for £90 Ish and run.

I worry those are the batteries that cause problems?

 

I think I would stick to one of the suppliers that has been recommended here

Yes - I remember.

 

So if a 36v hub motor has a "no load" max speed of 21 mph (say) and a restricted speed on the flat of 15.5 mph, it is running at 74% of its no load speed, which will usually be around peak efficiency ?

 

If you then use a 48V supply on the same motor then its "no load" max speed will be 28 mph. If it is restricted to 15.5 mph then it is running at 55% of it's no load speed, which will be less efficient ?

The difference in efficiency would only show if the two systems were running at the same speed with the same current. The 48v system needs less current to run at 15 mph than the 36v system. All the simulator charts are done assuming full power is demanded. When you run the two simulations, you'll see what you explain, that the 48v system appears to be less efficient at low speed, but when you reduce the throttle to 75% on the 48v system to match the power of the 36v one, the two efficiency charts become virtually identical.

 

https://ebikes.ca/tools/simulator.html?bopen=true&batt_b=B4823_AC&throt_b=75

This one shows what I was originally explaining a bit better. The two motors both have 15A. You start both bikes up a 10% hill with max power all the way until the 36v one reaches its max speed of 14.6kph, then continues struggling at that speed with 63.3%efficiency. The 48v one with more power goes to 18.2kph with 65.8% efficiency, so faster and more efficient.

https://ebikes.ca/tools/simulator.html?bopen=true&batt_b=B4823_AC&throt_b=100&autothrot_b=false&grade=10&grade_b=10&cont=cust_15_70_0.03_V&cont_b=cust_15_70_0.03_V

Anyone ever bought one of those 48v batteries off Amazon for £90 Ish and run.

I worry those are the batteries that cause problems?

 

[mention=14891]billyboya[/mention]'s didn't last long on his electric moped - many of the same sellers on AliExpress use Amazon Marketplace. There's more than one thread about this.

 

https://www.pedelecs.co.uk/forum/threads/electric-moped-fault.43510/

The difference in efficiency would only show if the two systems were running at the same speed with the same current. The 48v system needs less current to run at 15 mph than the 36v system. All the simulator charts are done assuming full power is demanded. When you run the two simulations, you'll see what you explain, that the 48v system appears to be less efficient at low speed, but when you reduce the throttle to 75% on the 48v system to match the power of the 36v one, the two efficiency charts become virtually identical.

 

https://ebikes.ca/tools/simulator.html?bopen=true&batt_b=B4823_AC&throt_b=75

 

Thanks [mention=3847]saneagle[/mention] - that was very interesting, I changed the motor to an XF07 and then a AKM G75 with 20" wheels and used 15A and 18A controllers and played with the gradient and the throttle (current based throttle) and as you say for the same speed, for the same gradient the motor running at 36V and at 48v had nearly identical efficiency (even at really low speeds). It showed the 36V one a tiny bit - 0.5% more efficient in most of the scenarios I tried. Of course the motor running at 48V had a higher top speed when the 36V "topped out" at its maximum speed and better hill climbing ability because it had more power - so I couldn't find any downsides ! I'm convinced now

Anyone ever bought one of those 48v batteries off Amazon for £90 Ish and run.

I worry those are the batteries that cause problems?

Put a link up, otherwise advice is guesswork. £90 for how many Wh or Ah? Ebike battery or just 48V battery?

 

You get what you pay for, so likely to be a pile of crap, but year by year prices are coming down.

 

For a hub motor, the bigger the battery capacity the longer it will last (and I don't mean range, I mean number of charge cycles) because the load per cell is lower. Hub motors make heavy demand on the battery on hills. Going too small or too crap is a false economy.

I started ebiking on both 36V and 48V batteries. While there is more power on 48V, I'm happy with performance of my hubmotors with dual voltage KT 20A controllers at 36V since our average speed is under 13 mph, 20 km/hour. However, I thought our 48V midmotors TSDZ2 and BBS02B were too weak on 36V.

 

I still use 36V batteries on my 20" bikes. I only see 30 km/hour on those bikes going downhill.

I started ebiking on both 36V and 48V batteries. While there is more power on 48V, I'm happy with performance of my hubmotors with dual voltage KT 20A controllers at 36V since our average speed is under 13 mph, 20 km/hour. However, I thought our 48V midmotors TSDZ2 and BBS02B were too weak on 36V.

 

I still use 36V batteries on my 20" bikes. I only see 30 km/hour on those bikes going downhill.

My bike is 36volt and I have 3 batteries with a 15 amp controller going to a 3 way splitter/balancer the balancer handles up-to 72 volt but I would like to try a 48 battery from my wife’s bike , what controller have you got model wise as I would like to be able to run both voltages of needed.

[mention=34503]matthewslack[/mention]

 

Here is link. Would you use a battery like this?

 

https://amzn.eu/d/93P5z0z

[mention=34503]matthewslack[/mention]

 

Here is link. Would you use a battery like this?

 

https://amzn.eu/d/93P5z0z

 

No, I'm no expert but I think it can't be 48V 30Ah 13s3p, maybe 10Ah - well dodgy

3sp 10.5ah at most with 18650 cells, cells will be low brand China or just fake copies filled with sawdust and other materials. Most likely the battery capacity is 3ah.

My bike is 36volt and I have 3 batteries with a 15 amp controller going to a 3 way splitter/balancer the balancer handles up-to 72 volt but I would like to try a 48 battery from my wife’s bike , what controller have you got model wise as I would like to be able to run both voltages of needed.

I think you might be misunderstanding something. That splitter is normally so that you can add another 36v battery in parallel, so the voltage will still be 36v, not 72v. You have to look at the controller to see what voltage is written on it. If it says 36v, you can't fit a 48v one. if it says 36v/48v, you can, but then you need to change the voltage setting in the LCD.

 

I don't know your bike, so I might be wrong, but you can confirm either way by looking at the controller.

At 72v he sure would make the controller pop.

[mention=34503]matthewslack[/mention]

 

Here is link. Would you use a battery like this?

 

https://amzn.eu/d/93P5z0z

Not a chance. An uncased block of cells is immediately unsafe, and the bigger it is the worse it is in a crash. The nonsense claim about capacity indicates unscrupulous seller/maker targeting minimum price above all other issues.

 

Buy one good battery, not too small for your motor's demands, and overall you will spend less money.

I think you might be misunderstanding something. That splitter is normally so that you can add another 36v battery in parallel, so the voltage will still be 36v, not 72v. You have to look at the controller to see what voltage is written on it. If it says 36v, you can't fit a 48v one. if it says 36v/48v, you can, but then you need to change the voltage setting in the LCD.

 

I don't know your bike, so I might be wrong, but you can confirm either way by looking at the controller.

this is the balancer/splitter i have fitted with my standard 21ah slideout underseat battery a hailong 21ah on the bottle bracket and a yose 21ah triangle in the middle under crossbars all 3 batteries are 36 volt but the splitter will handle up to 3x 72 volt ones all batteries have to be the same voltages i am sorry for not explainlng more as i have 3 x 48 volt batteries for my wifes bike so i seen in the post that the user had a kt dual voltage controller so in theory i was thinking i could fit another balancer for 48volts and use 48 volts in hilly areas then switch back to 36volts on the flat that was my thinking more torque for hills ?

You would be carrying so much battery weight if you take both 36 and 48V systems with you!

You would be carrying so much battery weight if you take both 36 and 48V systems with you!