48V vs 52V battery for Ultra 1000

[roshan]

Ok, this is simply not true.
(or not necessarily true)

It is depending on the BMS and most importantly, cells.

You're only looking at the voltage. Not the drain rate (amperage) of cells.

Just because the battery pack says 48V (54.6V), it doesn't mean they can provide equal amount of power (wattage) compare to other 48V.
Fact is, some 36V batteries can outperform some 48V batteries.
This is exactly why you can't just look at the voltage (V) and amperage (Ah) to determine the battery performance.

HillEater (ebike company in Canada) initially used their 36V pack because high quality cells can burst so much amperage, you don't NEED 48V or 52V to produce mere 850W or so.
However, I don't think consumers quite understood the concept of electrical engineering aspect of it, so it appeared that 36V battery was immediately dismissed as inferior version of "more powerful" 48V and 52V packs with cheaper cells (low burst / drain rate) from other ebike companies.
Yeah, 52V sounds more powerful than 36V, but in reality, if both bikes are producing 750W for example, virtually there's no difference.

( For those of you familiar with RC cars, did you notice Tamiya 7.2V RC cars are way faster, and batteries are way more powerful than Toys "R" Us 9.6V RC cars? )

Your argument of once it drops down to 46V, you will notice a big difference is because of crappy cells with low burst rate.
This is exactly why Tora (owner of Juiced Bikes) no longer cells 52V 21Ah battery pack, because it was packed with high capacity, but low burst rate cells.

As you probably know, wattage (W) = voltage (V) x amperage (Ah)
If the battery cells have low burst amperage rate, the wattage (W) will inevitably lower because of the voltage is at 46V.

For example, let's say your bike (controller) demands 750W in a given situation, to provide 750W of power, at fully charged at 54.6V, the battery only needs to provide 13.73A of amperage.
Okay, here's the thing, now assume the voltage dropped down to 46V, and the controller demands 750W of power, at 46V, the battery will need to provide 16.3A of amperage.
But what if the pack's max amperage rate was 15A? It can only provide 690W. Not 750W as demanded. This is exactly how you see the power drop.
(Yes, I know it could also depend on BMS and perhaps the controller used, but you get the idea)
But what if you use high quality cells, like 36V pack with powerful cells that can provide 30A power?
The fully charged 36V pack is 42V.
At 42V, to provide 750W of power, it needs to provide 17.85A of amperage, it is still a safe zone.
What if 36V battery voltage drops down to 32.4V? (near empty, 20%) it would have to provide 23.15A, which is far less than 30A max amperage.

This is exactly why you don't see power drop bikes equipped with high performance cells.

We use 18650GA cells that are rated for 10A continuous for each P circuit. The 52V 17.5ah and 48V 21ah pack both use 14s 6P and 13S 6P combination. So if you assume the cells are the same in both packs, they can easily do 60A draw. The BMS we use on our packs are rated for 45A and the Ultra motor only pulls 30A. So, if you assume the same motor, same cells, same current draw, and same voltage sag among two bikes, one with the 48V 21ah pack and one with 52V 17.5ah pack, you'll notice what I've said in my previous comment to be exactly true.

 

[Ebiker33]

Okay something isn't making sense.. did you mean 14S 5P and 13S 6P?

If both packs contain the same batteries, and if they both have the same 6P layout, they both should get the same Ah rating. (17.5Ah or 21Ah)
I'm assuming the 13S has 6P and 14S has 5P, judging by the amperage.

So 21Ah ÷ 6P = 3.5A and 17.5Ah ÷ 5P = 3.5A
Here, I got the same 3.5A, which is 3500mah

Okay so I will assume the pack comes with 18650 batteries, 3500mah, with 10A continuous as you said.

The combination:
14S 5P
13S 6P

(In this case, the 48V actually has a little advantage at 60A (6P) and 50A(5P) in terms of amperage)

which is,

(13S 6P): 48V x 21Ah = 1008Wh
(14S 5P): 52V x 17.5Ah = 910Wh

Motor spec:
According to you, 30A max

Question:
I thought the standard spec for was Bafang Ultra 1000W nominal, 1600W max?

At full charge:
48V battery, 1000W ÷ 54.6V = 18.31A
52V battery, 1000W ÷ 58.8V = 17.01A

48V battery, 1600W ÷ 54.6V = 29.30A
52V battery, 1600W ÷ 58.8V = 27.21A

At 20%:
48V battery, 1000W ÷ 42.1V = 23.75A
52V battery, 1000W ÷ 45.4V = 22.03A

48V battery, 1600W ÷ 42.1V = 38.00A
52V battery, 1600W ÷ 45.4V = 35.24A

So according to you, the BMS is rated for 45A max, but the motor is restricted to 30A max?

Are you sure? Because if that's true, at 20%, the motor can only produce:
With 48V battery: 42.1V x 30A = 1263W
With 52V battery: 45.4V x 30A = 1362W

^ above rating is MAX, not nominal. I don't know this for the fact, but nominal voltage "might" be lower.

Perhaps something like 789W nominal for 48V (42.1V) and 851W nominal for 52V (45.4V)?
^ the above nominal ratings are my complete amateur estimates, based on the stock ratio of 1000W nominal & 1600W max.

I might have missed something I'm not an engineer, so if anyone has any corrections, please feel free

Chart that I used to determine voltage:

(Link Removed - No Longer Exists)

I appreciate the chart, it helps me to understand why it is not good to ride your Ebike until it's 100% dead, if you have a second with you swap it out when it gets low.
Also the advantage of a 52V for a larger motor like an ultra, for example with only 30% left you are still at 47V, so basically it' like having a 48V for the whole range of battery charge.

 

[Deafcat]

The ultra will actually run 1700W peak with full charge 52V, which is pretty awesome. As for the rest of the debate, what Roshan and Timpo have pointed out are both generally correct: less amp draw at given motor output gives the 52V a slight advantage most of the time, so long as good cells are used in the pack. The last remaining challenge is to fit extra cells into the pack, to allow for 6P 52V construction (21+Ah). 84 cell packs are pretty rare currently!

 

[pennybags]

The last remaining challenge is to fit extra cells into the pack, to allow for 6P 52V construction (21+Ah). 84 cell packs are pretty rare currently!

Excellent stuff.

I believe the Watt Wagons ‘Titan’ pack has 84cells, 30Q (https://wattwagons.com/collections/battery/products/titan)

Is that the same pack as yours? More choices are obviously better.

 

[Ironcopelev]

I'm looking at placing an order for the Ultra 1000 once they get back in stock and noticed that BikTrix has added an option today for a 52V 17.5Ah battery.

What would the benefit be for a 52V 17.5Ah battery versus the 48V 21Ah battery?

Based on BikTrix website the 52V has about a 5 mile LESS range than the 48V.

I just ordered the bpm 1000 watt 48v/21a
Step thru e bike is good purchase?

 

[roshan]

Ok, this is simply not true.
(or not necessarily true)

It is depending on the BMS and most importantly, cells.

You're only looking at the voltage. Not the drain rate (amperage) of cells.

Just because the battery pack says 48V (54.6V), it doesn't mean they can provide equal amount of power (wattage) compare to other 48V.
Fact is, some 36V batteries can outperform some 48V batteries.
This is exactly why you can't just look at the voltage (V) and amperage (Ah) to determine the battery performance.

HillEater (ebike company in Canada) initially used their 36V pack because high quality cells can burst so much amperage, you don't NEED 48V or 52V to produce mere 850W or so.
However, I don't think consumers quite understood the concept of electrical engineering aspect of it, so it appeared that 36V battery was immediately dismissed as inferior version of "more powerful" 48V and 52V packs with cheaper cells (low burst / drain rate) from other ebike companies.
Yeah, 52V sounds more powerful than 36V, but in reality, if both bikes are producing 750W for example, virtually there's no difference.

( For those of you familiar with RC cars, did you notice Tamiya 7.2V RC cars are way faster, and batteries are way more powerful than Toys "R" Us 9.6V RC cars? )

Your argument of once it drops down to 46V, you will notice a big difference is because of crappy cells with low burst rate.
This is exactly why Tora (owner of Juiced Bikes) no longer cells 52V 21Ah battery pack, because it was packed with high capacity, but low burst rate cells.

As you probably know, wattage (W) = voltage (V) x amperage (Ah)
If the battery cells have low burst amperage rate, the wattage (W) will inevitably lower because of the voltage is at 46V.

For example, let's say your bike (controller) demands 750W in a given situation, to provide 750W of power, at fully charged at 54.6V, the battery only needs to provide 13.73A of amperage.
Okay, here's the thing, now assume the voltage dropped down to 46V, and the controller demands 750W of power, at 46V, the battery will need to provide 16.3A of amperage.
But what if the pack's max amperage rate was 15A? It can only provide 690W. Not 750W as demanded. This is exactly how you see the power drop.
(Yes, I know it could also depend on BMS and perhaps the controller used, but you get the idea)
But what if you use high quality cells, like 36V pack with powerful cells that can provide 30A power?
The fully charged 36V pack is 42V.
At 42V, to provide 750W of power, it needs to provide 17.85A of amperage, it is still a safe zone.
What if 36V battery voltage drops down to 32.4V? (near empty, 20%) it would have to provide 23.15A, which is far less than 30A max amperage.

This is exactly why you don't see power drop bikes equipped with high performance cells.

We use the same cells on both packs rated for 10A peak each (which means that on the 48V 21ah pack, it can support up to 60A (6P x 10A) and on the 52V 17.5Ah pack up to 50A (5P x 10A) draw). BMSs on our packs are 45A rated. Motors are rated for peak 30A.

 

[roshan]

I just ordered the bpm 1000 watt 48v/21a
Step thru e bike is good purchase?

You'll find out very soon

 

[lordnox09]

Having both the 21ah and the 52v the ride is more enjoyable the whole time with the 52v it just has more power for this particular motor when the 21ah gets below 46 it just does not have the same power to pull the bike the same way and the range seems to be the same for both I seem to get about 30-35km but I like the throttle a little too much