Battery advice

[Cavemann]

Hi, I'm building a two wheel drive (hub motors) mountain bike for off-road, from a Pinnacle Lithium 3 frame.
I've got the rims/motors, controllers, display and throttle etc. I just need a battery.
I'm planning for a 48v 15-20Ah battery to sit as low as possible between the down-tube and seat tube.
I've heard that the individual cell make/type can play a big part in how well suited the battery is to an ebike, but I've got no real understanding of this, and looking online I don't know how to tell where to buy a good quality one.
Can anyone advise a good pre-made battery that will work well for my project?

 

[Woosh]

batteries are as good as the cells that they are made with.
Just ask your suppliers which cells they use in your battery. Cells are graded into batches. You want grade A cells too.
Stay away from pouch cells. They are much less safe compared to cylindrical cells. Cylindrical cells have steel case and anti-explosion devicce. In general, bigger cells are slightly better than smaller cells. 27100 (21mm x 70mm) are better than 18650 (18mm x 65mm) because you need fewer of the larger ones.
Also, choose a good brand for your charger.
Good brands means good quality control, important for this safety critical piece of equipment.
Finally, buy from a UK company. They generally have insurance, just in case.

 

[soundwave]

eBike Batteries

ebikebatteries.co.uk

they can custom build packs to any size and you can choose what cells are used but very busy atm

 

[saneagle]

Hi, I'm building a two wheel drive (hub motors) mountain bike for off-road, from a Pinnacle Lithium 3 frame.
I've got the rims/motors, controllers, display and throttle etc. I just need a battery.
I'm planning for a 48v 15-20Ah battery to sit as low as possible between the down-tube and seat tube.
I've heard that the individual cell make/type can play a big part in how well suited the battery is to an ebike, but I've got no real understanding of this, and looking online I don't know how to tell where to buy a good quality one.
Can anyone advise a good pre-made battery that will work well for my project?

I've built several two wheel drive ebikes. Unless you have a special reason for one, I wouldn't recommend it. They're good for mud, wet grass and snow as long as hills aren't too steep. The problem is that the torque from the back motor lifts the weight off the front one and so the torque from the front one makes it slip and spin. That effect increases as the steepness of any hill increases.

If you decide to go ahead with it, you'll need a special high current battery. Assuming each motor controller is a minimum of 15A, you'll need a battery that can provide 40A continuously, which rules out all the cheap ones.

 

[Cavemann]

I've built several two wheel drive ebikes. Unless you have a special reason for one, I wouldn't recommend it. They're good for mud, wet grass and snow as long as hills aren't too steep. The problem is that the torque from the back motor lifts the weight off the front one and so the torque from the front one makes it slip and spin. That effect increases as the steepness of any hill increases.

If you decide to go ahead with it, you'll need a special high current battery. Assuming each motor controller is a minimum of 15A, you'll need a battery that can provide 40A continuously, which rules out all the cheap ones.

That's good advice. I want two wheel drive mainly for unstable surfaces such as sand/gravel etc. However, based on what you've said I may mount the battery a bit further forward than planned to weigh the front down a bit more...

 

[matthewslack]

It'll be a learning experience for sure!

If both motors are controlled by the same pas and / or throttle all I can see is unpredictable behaviour in the low grip conditions you are targeting. Like having front and rear brakes on a single lever. Being able to modulate the brakes separately is vital on a two wheeler in challenging conditions.

There is a lot to be said for having a non- driven wheel, which will predictably not be sliding when the powered one is.

Be sure to report how well it works!

 

[WheezyRider]

Just stick a decent hub on the back and you will be fine. I have done some off road with a front wheel drive and it's ok, but on loose surfaces you have to be very careful and on steep inclines you have to shift a lot of weight over the front to stop it spinning. So if you had a hub on the back too, that would be losing traction, you'd have to be constantly shifting your weight around and when the wheel you steer with starts slipping it can get you into trouble. Two motors is not worth the hassle.

But hold on, the mid drive people will be along in a minute to push you in that direction

 

[saneagle]

To connect the throttle and/or PAS to both controllers, you wire it in the normal way to the first, then splice a wire to each of the throttle and PAS signal wires, and wire only those to the second controller's connectors, leaving off the ground and 5v wires.
'

 

[Cavemann]

eBike Batteries

ebikebatteries.co.uk

they can custom build packs to any size and you can choose what cells are used but very busy atm

The ebikebatteries.co.uk seem very expensive to me. Maybe you get what you pay for, but there's a lot even on Amazon with good reviews and about 50% of the cost. I'll post the one I'm looking at below...

 

[Woosh]

Read my post #2. The cheaper batteries on amazon, ebay, ali etc don't have cell brand and A grade.

 

[Cavemann]

I'm currently looking at the following:

https://www.amazon.co.uk/Battery-Lithium-Charger-Electric-Delivery/dp/B08SWM3Z6F?th=1

It claims to give 45A constant discharge, which is significantly more than I need, but good to have some overhead right.

Any advice pros/cons would be appreciated.

 

[Nealh]

EBike batteries use the very best cells.

Do your homework, visit the various forums to search for Unit Power Pack reviews.
That battery claims may or not be true, it suggests a LG 4800mah cell is used , try and find a 4800mah LG cell dat sheet ? They make 5000mah cells but not 4800mah.
You get what you pay for.

 

[Peter.Bridge]

I'm currently looking at the following:

https://www.amazon.co.uk/Battery-Lithium-Charger-Electric-Delivery/dp/B08SWM3Z6F?th=1

It claims to give 45A constant discharge, which is significantly more than I need, but good to have some overhead right.

Any advice pros/cons would be appreciated.

48V 19.2AH, LG21700 Cell, suitable for 250W 350W 500W 750W 1000W 1500W motor. Max Constant Discharge Current: 45A, Charger: 54.6V 3A. Discharge connector: XT60(Female &Male)

@Woosh can probably give you better advice but I think the LG 21700 cells are good (if the battery is really using them)
The slightly strange thing about that advert is there isn't an option "48V 19.2AH" It's as is they have copy and pasted the text from an earlier advert

maybe here

 

[soundwave]

jimmy uses only grade a cells and has a 30k spot welder and can use copper or silver connectors you get what you pay for.

my 500w bosch batts are 630 quid

 

[Peter.Bridge]

what does everyone think of these ?

 

[Nealh]

what does everyone think of these ?

They will be ok for a controller with max 25a rating.
The only unknown is the quality/grade of the cells used.

I bought a 14.5ah Panny PF battery off them some 4 years ago and it worked ok.

 

[Cavemann]

Based on your advice I've decided to go with just a rear hub motor and forget the front.
Thanks for convincing me @saneagle, @matthewslack and @WheezyRider , I think you've saved me from making a big mistake with this project.

 

[saneagle]

Based on your advice I've decided to go with just a rear hub motor and forget the front.
Thanks for convincing me @saneagle, @matthewslack and @WheezyRider , I think you've saved me from making a big mistake with this project.

It's simpler, cheaper, works better, and you can make it legal. Use any medium size geared "250w" hub-motor run it with 48v and 20A, and you should have all the power you need and remain legal.

 

[Az.]

Use any medium size geared "250w" hub-motor run it with 48v and 20A, and you should have all the power you need and remain legal.

Hmmm... Interesting... Is that really legal?

 

[Woosh]

Hmmm... Interesting... Is that really legal?

Two motors working at the same time? That not legal to start with. You would also increase risks - a two wheel drive is also the recipe for losing traction and steering.