Which battery for a 350 mid drive?

[xander02]

ADVICE NEEDED

Hi my daily commute is a fairly short 16km trip.

I want to know what is the smallest battery I can get away with for my 350W mid-drive motor (15ah TSDZ2 motor)? I have seen a 36v 6.8Ah bottle battery which is a nice compact size but I want to know if this would suffice for my needs? If so what sort of average range do you think i could get? The terrain is fairly flat and I would want to go 15-20mph max. I weight about 100kgs. I may plan to only use the motor one one leg of my commute (8kms).

The other alternative is to get a 36v 10.5ah battery but this is substantially larger and may be far too large for my actual needs.

Any help greatly appreciated

Thanks in advance.

 

[Kinninvie]

Best to buy the larger one as once you start riding you will want to go further.
Far cheaper than having to buy a bigger one later.
In my case I started with 10Ah which I thought was plenty but now I have 64Ah of batteries!

 

[xander02]

Best to buy the larger one as once you start riding you will want to go further.
Far cheaper than having to buy a bigger one later.
In my case I started with 10Ah which I thought was plenty but now I have 64Ah of batteries!

Thanks Kinninvie, I'm only going to be using this bike for commuting to and from work so my 16km round trip is unlikely to change. I have another bike for leisure and long distance riding at weekends.

In this instance do you think the 6.8ah will be ok on a 350w motor?

 

[anotherkiwi]

It depends on the cells inside we need to know how many of them and what type they are to give an opinion.

 

[xander02]

It depends on the cells inside we need to know how many of them and what type they are to give an opinion.

Thanks anotherkiwi, See battery info below:

Type: LiNiCoMn2O4 Battery Pack

1. Basic Characteristics

Weight = 1.4kg

Model- UPP-S001

Rated Voltage = 36V

Rated Capacity C1 = 6.8AH

Battery Resistance ≤100mΩ

Standard Charge Current= 2A

Max Charge Current = 5A

Max Charge Voltage =42V

Cell OverCharge Protection Voltage = 4.2V/Cell

Continuous Discharge Current = 20A
Peak Discharge Current = 50A
Discharge Cut-off Voltage = 30V

Cell Overdischarge Protection Voltage = 3.0V/cell

Ratio Discharge =

1C >96%C1
2C>93%C1
3C>90%C1

 

[KirstinS]

Many variables here e.g. How much effort you put in, wind, assistance setting etc.

Also, can this battery output enough amps to cope with the system demands ? Can you link the exact one ?

I would suggest it be a very close call for both ways . And I also suspect you won't want to pedal one way with a motor and battery weight

Totally draining lithium packs shortens their life too.

I have a 15ah battery for my commute bit never usemore than 10ah. My old 11ah pack died far quicker than the current one

 

[KirstinS]

Sorry my post above crossed

If your kit is 15a rated and battery 20a continuous you should be ok

You. Could always buy another charger and keep at work

 

[anotherkiwi]

It doesn't say how many cells there are in Series and in parallel and which brand they are. Just taking a quick guess that if it was made of Samsung 22F cells it won't be up to the task. Never believe the constant Amps output on the spec sheet, they are almost always over optimistic.

If you can find a small battery with 3P10S Samsung 30Q cells you will be in business, that would be small and light 9 Amps and capable of 15 A continuous over short hills.

 

[xander02]

Sorry my post above crossed

If your kit is 15a rated and battery 20a continuous you should be ok

You. Could always buy another charger and keep at work

thanks. I think i'm going to take the plunge and go with the 6.8ah battery. Yes, its a risk but it also looks far more stealthy which is the look i'm going for with the TSDZ2 motor.

 

[anotherkiwi]

thanks. I think i'm going to take the plunge and go with the 6.8ah battery. Yes, its a risk but it also looks far more stealthy which is the look i'm going for with the TSDZ2 motor.

That money would be better spent having someone build you a small battery with high power, high quality cells...

 

[xander02]

That money would be better spent having someone build you a small battery with high power, high quality cells...

any suggestions on who I could go to to get this done?

 

[Deleted member 4366]

When you run a battery at high current, the capacity is substantially reduced. I'd count on that battery giving you 5Ah rather than 6.8Ah.

You need 250w to cruise at 15 mph without pedalling, so that's 250wh to travel 15 miles at 15 mph. That's 17 Wh/m. 16km=10 miles, so you'd need 167 Wh to complete it. The 6.8Ah battery can give you approximately 180Wh, so you should be alright, bearing in mind that you will be pedalling as well. If you go to 20 mph, I'd say that the battery would run out. Basically, you'd have to adjust your speed and pedal effort according to how fast the battery goes down.

I'd ask the question, do you really need to save 1kg on the battery when you weigh 100kg? It would be a lot easier to eat salad for a week, which is what I did. I can now have a 137 aH battery without any additional weight from how I was at Xmas.

 

[anotherkiwi]

any suggestions on who I could go to to get this done?

https://www.bga-reworking.co.uk/e-bike-batteries.html

 

[KirstinS]

Jimmy at bga reworking
+44 208 361 1790

 

[KirstinS]

Never believe the constant Amps output on the spec sheet, they are almost always over optimistic.

Good point anotherkiwi

 

[Danidl]

ADVICE NEEDED

Hi my daily commute is a fairly short 16km trip.

I want to know what is the smallest battery I can get away with for my 350W mid-drive motor (15ah TSDZ2 motor)? I have seen a 36v 6.8Ah bottle battery which is a nice compact size but I want to know if this would suffice for my needs? If so what sort of average range do you think i could get? The terrain is fairly flat and I would want to go 15-20mph max. I weight about 100kgs. I may plan to only use the motor one one leg of my commute (8kms).

The other alternative is to get a 36v 10.5ah battery but this is substantially larger and may be far too large for my actual needs.

Any help greatly appreciated

Thanks in advance.

Get the bigger battery. Battery life is dependent on the number of charge discharge cycles. The matrix inside the cells of the battery physically changes shape from charge to discharge and this is the wear mechanism. If you recharge the bigger battery daily, the range of the discharge is less so they are partial discharges only and don't damage the battery as much. Also even when it loses capacity, it will still have a useful life for longer.