Battery Capacity

[dwest100]

Three batteries, all 52v, all 10ah.
One= 50 amp
One= 25 amp
One= 20 amp
Thus all have 520wh of capacity, correct?

So what is the advantage of the 50amp over the 20 amp?

Given a ride drawing a constant 2amps and 110watts, which battery will provide the most repetitions of the ride? How do you calculate this?

Thanks!

 

[lnanek]

I think I limited my controller to 20A max once. Could only reach 20MPH whereas normally it can do 30MPH. I wouldn't buy a battery that weak, personally. If you have some non-ebike usage that only ever draws 2A, all three of those batteries will perform the same. Just because they have the capacity to discharge more amps at once without overheating doesn't mean you have to.

 

[dwest100]

The example is for the sake of simplicity.
So why would I buy the more expensive 50amp battery vs the 20 amp, given they perform the same at the given example?

 

[dwest100]

It appears I would look for higher ah if I want more repetitions of said ride before recharging. Correct?

 

[electric_nz]

Higher current rating will usually mean more expensive newer cells with lower internal resistance. Often they are the kind used in power tools and well suited to high power motors. They will sag less under load, run cooler and quite likely have a longer usable lifespan. Try to find out what cells are in each one and search for the data sheet.

 

[dwest100]

Higher current rating will usually mean more expensive newer cells with lower internal resistance. Often they are the kind used in power tools and well suited to high power motors. They will sag less under load, run cooler and quite likely have a longer usable lifespan. Try to find out what cells are in each one and search for the data sheet.

Thanks but this isn’t relevant to my questions. I already have the batteries sourced.

 

[TDA78]

Given a ride drawing a constant 2amps and 110watts, which battery will provide the most repetitions of the ride? How do you calculate this?

Go with the highest energy density cell that supports your current requirements for the greatest cycle and calendar life.

Read the last paragraph here.

 

[electric_nz]

Voltage sag is very relevant- high internal resistance cells will hit low voltage cutoff under load much earlier; as the voltage will drop more. Compare the curves for the cells.

 

[dwest100]

Thanks again TDA78 and electric_nz, but your answers aren’t addressing my original questions in the very first post.

 

[Chalo]

Thanks again TDA78 and electric_nz, but your answers aren’t addressing my original questions in the very first post.

They answered your second and third questions. The answer to the first one is "nominally, yes, but".

If you can't hear answers, don't ask questions.

 

[TDA78]

Three batteries, all 52v, all 10ah.
One= 50 amp
One= 25 amp
One= 20 amp
Thus all have 520wh of capacity, correct?

So what is the advantage of the 50amp over the 20 amp?

Given a ride drawing a constant 2amps and 110watts, which battery will provide the most repetitions of the ride? How do you calculate this?

Do these three packs have the same cells but differently rated BMS modules? If so, the highest current rated BMS will have the lowest resistance and be slightly more efficient for more ride time.

 

[docw009]

If you really had a 52V10AH battery capable of 50A, its advantage is you can pull 50A. To realize this battery, you need high current cells. In general, these will last longer in this application because they will not heat up as much as lower current cells. If you can afford the cost of this battery, and need more than 25A, there you go, The tradeoff is that I doubt you will get 10AH out of the battery. The AH ratings are taken at low currents, and drop really fast when you run so high.

I am skeptical though, It would be far easier for the seller to simple double up on the cell count and sell a 52V20AH battery for customers that need 50A. You can put a 50A battery into the same form factor as a 25A battery, using more expensive cells, but the internal nickel interconnects, BMS. and associated wires need to be increased substantially, I don't think your typical chinese battery maker has the manufacuring equipement or the interest to really carry this out, In short, I think there's some lying going about if someone quotes a 50A 52v10AH battery.

 

[dwest100]

They answered your second and third questions. The answer to the first one is "nominally, yes, but".

If you can't hear answers, don't ask questions.

No need to be rude. Purposely simple questions deserve purposely simple answers. Thus not requiring discernment of irrelevant additional material.

The first responder accurately provided the answer to question 1. They would all perform the same because they all have the same amp hour capacity.

And thank you for your reply that serves no purpose other than repeating the first response (which I understood) and making an unnecessary rude suggestion.

Exactly what I was trying to avoid.

 

[dwest100]

Do these three packs have the same cells but differently rated BMS modules? If so, the highest current rated BMS will have the lowest resistance and be slightly more efficient for more ride tim

Do these three packs have the same cells but differently rated BMS modules? If so, the highest current rated BMS will have the lowest resistance and be slightly more efficient for more ride time.Again, for simplicity, all are identical except their amp ratings.

 

[dwest100]

Again, for simplicity, all are identical except their amp ratings.

 

[dwest100]

If you really had a 52V10AH battery capable of 50A, its advantage is you can pull 50A. To realize this battery, you need high current cells. In general, these will last longer in this application because they will not heat up as much as lower current cells. If you can afford the cost of this battery, and need more than 25A, there you go, The tradeoff is that I doubt you will get 10AH out of the battery. The AH ratings are taken at low currents, and drop really fast when you run so high.

I am skeptical though, It would be far easier for the seller to simple double up on the cell count and sell a 52V20AH battery for customers that need 50A. You can put a 50A battery into the same form factor as a 25A battery, using more expensive cells, but the internal nickel interconnects, BMS. and associated wires need to be increased substantially, I don't think your typical chinese battery maker has the manufacuring equipement or the interest to really carry this out, In short, I think there's some lying going about if someone quotes a 50A 52v10AH

Voltage sag is very relevant- high internal resistance cells will hit low voltage cutoff under load much earlier; as the voltage will drop more. Compare the curves for the cells.

Not relevant to my very simple questions. Regardless of the technical facts the batteries will perform the same for the given ride, given they are equal in every way other than amps.

 

[dwest100]

Not relevant to my very simple questions. Regardless of the technical facts the batteries will perform the same for the given ride, given they are equal in every way other than amps.

All said batteries can be purchased here. I am not lying.

52v Batteries

52v Batteries Batteries from Electrify Bike Company utilize the latest 21700 cell technology from the leading brands making safe Lithium Ion cells. We use top-of-the-line high-capacity/high-power cells from Samsung, Panasonic, and LG. You won't find batteries of the same size with higher...

www.electrifybike.com

 

[TDA78]

All said batteries can be purchased here. I am not lying.

52v Batteries

52v Batteries Batteries from Electrify Bike Company utilize the latest 21700 cell technology from the leading brands making safe Lithium Ion cells. We use top-of-the-line high-capacity/high-power cells from Samsung, Panasonic, and LG. You won't find batteries of the same size with higher...

www.electrifybike.com

The 50A and 25A packs use different cells, which is very relevant. I can't find the 20A pack. For your low current requirements, I recommend the 25A pack made with 50G cells. It will give you nearly identical run time and last for many more charge cycles. The 50S cells have a much shorter lifespan.

 

[docw009]

Those look like good batteries, not cheap stuff, Should have posted that first, By the way. I have the 52V6AH made with Samsung 30Q, although I bought it six years ago from another seller. Very good battery, and still tests out at an honest 6AH after all these years. When I use it, I only pull 6-8A out of it on my bike, but I have seen it max out at 25A.,.

 

[dwest100]

TDA78, The 20amp version I already own and was replaced by the 25amp you saw.

I arrived at the same conclusion as you when Inanek answered my original questions with no concerns for technical details of cells, origin of cells, etc.

That answer being:
No significant difference in the number of the example trip repetitions between the three since they all have the same amp hour rating. A higher amp hour rating would provide more example trip repetitions. Battery amp ratings have no effect on repetitions of the provided trip example.

Granted, there are lots of technical battery variables that exist. But for the purpose of the average buyer purchasing a replacement battery for his bicycle, from the three examples provided, none of the provided technical data are relevant to the questions.

Purposely simple, structured questions require purposely simple answers. That avoids needless analysis of unnecessarily complicated answers.

Thanks for your answers except of course the rude one.

 

[dwest100]

Those look like good batteries, not cheap stuff, Should have posted that first, By the way. I have the 52V6AH made with Samsung 30Q, although I bought it six years ago from another seller. Very good battery, and still tests out at an honest 6AH after all these years. When I use it, I only pull 6-8A out of it on my bike, but I have seen it max out at 25A.,.

Not necessary to detail my selected battery examples or provide links for an expert to arrive at an answer based on the simple structured questions.

People complicate answers to simple questions unnecessarily for some reason. Inanek was the only one who actually answered the questions without unnecessary technical data.

I seriously doubt I will ever care about the tech data variables provided by everyone.

I purposely stated a simple, structured scenario, with three simple questions. No background or links necessary. My point of providing simple answers to simple questions is only reinforced by observing the length of this thread lol!

Thanks again for all the answers, except the rude one of course.

 

[eMark]

Three batteries, all 52v, all 10ah.
One= 50 amp (Maximum Continuous Dischrge? - Is the BMS and Controller rated for a 50amp MCD?)
One= 25 amp ( " - " 25amp MCD)
One= 20 amp ( " - " 20amp MCD)
Thus all have 520wh of capacity, correct? (assumng each battery is actually identical in it's wh rating)

So what is the advantage of the 50amp over the 20 amp? (50amp has less IR so capable of higher speeds with a Controller designed to handle 40amp without overheating either the battery, BMS, Controller..

Given a ride drawing a constant 2amps and 110watts, which battery will provide the most repetitions of the ride?

When you say "repetitions" do you mean "cycle life" ? That depends on the quality of the cells, battery fab, and charging voltage. Also storage condition of battery when not used.

How do you calculate this?

It;s by trial runs as there are too many variables for a formula.

Your casual easy going ride on level urban terrain will average say 4-6 amps depending on your bike's effeciency, your weight, wind, etc and desired speed (for example 6-10mph).

 

[TDA78]

I purposely stated a simple, structured scenario, with three simple questions. No background or links necessary. My point of providing simple answers to simple questions is only reinforced by observing the length of this thread lol!

It's an unusual approach. I mentor budding electrical engineers who ask the wrong questions all the time. I always appreciate too much information over what they think is a concise question.

 

[amberwolf]

Three batteries, all 52v, all 10ah.
One= 50 amp
One= 25 amp
One= 20 amp
Thus all have 520wh of capacity, correct?

So what is the advantage of the 50amp over the 20 amp?

Assuming it is correctly rated based on it's actual capability, and not just a BMS rating, a battery with a higher A rating (current output capability) is able to supply more current with less voltage sag than one with a lower A rating.

The less voltage sag, the more total watts you get out of the battery and thus available to the system (A x V = W).

The more total watts, the more can be used and the less that is wasted.

Given a ride drawing a constant 2amps and 110watts, which battery will provide the most repetitions of the ride? How do you calculate this?

Given the three batteries above, assuming all are actually capable of the current listed with minimal voltage sag, then at 2A they would all perform effectively the same.

If you were approaching the rating of one pack, then the higher A pack(s) would perform better as they would have less losses inside the cells, less heating, and less wasted power, so there is more available to use in the system for a longer time.

How much longer...depends on each battery's specific losses, how much voltage sag at the specific current used.

Watts is A x V, so the more voltage sag the less V you get out of the pack, and the more V & A "used up" inside the pack as watts of heat.

 

[dwest100]

Excellent information well stated.
Thank you.