E Bike Battery

[Wendelspanswick]

I'm building a 1500 Watt 48V E Bike on a budget and trying to work out how many batteries I need to make up a battery pack.
I've found a cheap source of Samsung 18650 cells that are rated at 2600 mah and a 3.7v nominal output and although I can work out how many cells in series (13) to give me roughly 48V I'm struggling to work out how many to parallel together to give me 1500 watts.

 

[Wendelspanswick]

I've just found the data sheet for the batteries and it states a maximum discharge rate of 5200 mah.

 

[Wendelspanswick]

So by my maths I would need 6 cells in parallel to give me 31 amps!
1500w ÷ 48V = 31.25 amps
6 x 5200 mah = 32.2 amps
6 x 13 = 72 cells
72 X 47 grams = 3.384 kg

 

[Wallace]

Is that enough to spin the tyre from a stand still?

 

[Wendelspanswick]

Looks like I'd be better off getting some more expensive batteries but with a higher discharge rate, there are batteries with a 15amp maximum discharge current so I'd only need 26 cells instead of 72.
Samsung inr18650 30Q.

 

[Wendelspanswick]

Is that enough to spin the tyre from a stand still?

No idea, the hub kit is £169, the batteries should cost about £80, the BMS (battery management system) is about £10 and a charger is about £20.
So for about £300 I should have a ridiculously powerful ebike.

 

[J1nx]

The 30Q is an excellent cell, watch the temperatures if you are DIYing a pack and hitting high continuous discharge. I’d be inclined to go 3 parallel with decent spacing if possible.

 

[Wendelspanswick]

Has anyone used the solderless battery clips to make battery packs up?
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/123355950954

 

[angellonewolf]

^^^ prob work but more resistance than a solder joint i would expect

 

[Burdekin]

I have a mate who know all about this stuff, would you like to me to ask him if I can pass on his details? This is his build and he knows all about the battery side of things. https://endless-sphere.com/forums/viewtopic.php?t=75457

 

[Wendelspanswick]

I have a mate who know all about this stuff, would you like to me to ask him if I can pass on his details? This is his build and he knows all about the battery side of things. https://endless-sphere.com/forums/viewtopic.php?t=75457

Yes please.

 

[frank horton]

have a 36volt elec bike.....the lith batt's were junk so used 3x12v, gel wheel chair batt's........similar size and do the job well......
main benefit's, cost and can use a normal battery charger.......

 

[J1nx]

Not sure who you use as a supplier but I’ve been happy with nkon.nl, they will weld tabs on for a fee, adds up if you buying a lot but it’s done properly.

 

[knighty]

what voltage are you going to run? voltage pretty much = top speed

you're better off getting some lipo packs from hobby king

https://hobbyking.com/en_us/batteries-chargers/batteries/lipo.html?wrh=1

they sell the connectors etc. to wire them all up too

it depends a bit on the motor (how many poles etc.) but 72v tops out about 40mph for most motors

the more storage (ah) you have the better, does the batteries no good running them too low, and gives you a bit more head room too

some of those hobby king cells have crazy amp ratings... my nephews bike (72v 20ah) is good for 2600amps (apparently)

 

[Burdekin]

Yes please.

Emailed him but not heard back unfortunately.

 

[wookie]

No idea, the hub kit is £169, the batteries should cost about £80, the BMS (battery management system) is about £10 and a charger is about £20.
So for about £300 I should have a ridiculously powerful ebike.

Not quite up to the Stealth B52 bomber bike as that has a 6.2Kw motor, but then again that costs a heck of a lot more than your £300.

Will yours be road legal ? it used to be max 250w motor and no assist above 15mph unless things have changed ?

Personally I think those limits are ludicrously stupid but that doesn't change the fact you need a licence, insurance etc just like you need with a motorbike.

 

[Wendelspanswick]

Not quite up to the Stealth B52 bomber bike as that has a 6.2Kw motor, but then again that costs a heck of a lot more than your £300.

Will yours be road legal ? it used to be max 250w motor and no assist above 15mph unless things have changed ?

Personally I think those limits are ludicrously stupid but that doesn't change the fact you need a licence, insurance etc just like you need with a motorbike.

The legal limit is still 250w, I plan to use mine to get me from home over the common (I have commoners rights) to my small holding so no public roads involved.
If I drive I have to go around the common and it's 10 miles each way and about 30 minutes, if I go over the common it's about 6 miles and should take about 15 to 20 minutes.

 

[wookie]

^ @Wendelspanswick I'm glad you know the rules and regs, I wasn't trying to be a spoilsport, I personally think electric bikes are a fantastic idea, the more powerful the better, I just didn't want you getting into trouble through not knowing about the legalities of them.

 

[knighty]

^ @Wendelspanswick I just didn't want you getting into trouble through not knowing about the legalities of them.

I was worried about that too.... but it's ok... all my bikes have had stickers on them saying they're 200watts 15mph....