# Brushless DC Electric Motor - wiring and energizing - front wheel 26' bldc electric bicycle motor

#### RandyFL

Joined Aug 28, 2014
127
I have on order a ...
Premium 48V 1000W 26” Electronic Bike Conversion Kit with Motor Front Wheel Hub Speed Controller

I was thinking about buying a 12 volt car battery ( heavy ) to power it. But starting thinking about " how do I turn the battery into 48 volts " in series 4 auto batteries are extremely heavy but 48 volts and a lot of current … 1. question - how would I turn a 12 volt car battery ( with lots of current ) into 48 volts wouldn't I need some way of limiting the current ( current divider ? ). 2. question - shouldn't there be a fuse ( somewhere ) from over powering the motor ( from burning up ) 3. smaller 12 volt batteries in series would provide the 48 volts but the electric bike wouldn't go very far... I guess the ideal thing would be to turn a single 12 volt car battery into 48 volts and limiting the current ( and test how far it goes ).

#### Dodgydave

Joined Jun 22, 2012
9,861
48V @1KW is 20.8 Amps, so you can use a 12V battery and DC converter upto 48V @21A or more, which is going to draw 83Amps!!! or a 48V battery capable of giving 21Amp.

Whichever you choose, 1KW is quite large for a battery to compete with.

#### RandyFL

Joined Aug 28, 2014
127
48V @1KW is 20.8 Amps, so you can use a 12V battery and DC converter upto 48V @21A or more, which is going to draw 83Amps!!! or a 48V battery capable of giving 21Amp.

Whichever you choose, 1KW is quite large for a battery to compete with.
Which is why I was thinking of an auto 12 volt battery

#### RichardO

Joined May 4, 2013
2,271
3. smaller 12 volt batteries in series would provide the 48 volts but the electric bike wouldn't go very far... I guess the ideal thing would be to turn a single 12 volt car battery into 48 volts and limiting the current ( and test how far it goes ).
Remember that what determines the range is the watt-hours, not the amps and volts alone.

It will be much easier (and, likely more efficient) to use 4 12-volt batteries.

#### RandyFL

Joined Aug 28, 2014
127
Remember that what determines the range is the watt-hours, not the amps and volts alone.

It will be much easier (and, likely more efficient) to use 4 12-volt batteries.
I agree ... but wouldn’t smaller batteries not go as far?

#### RichardO

Joined May 4, 2013
2,271
I agree ... but wouldn’t smaller batteries not go as far?
Run the numbers of one large battery compared to 4 small batteries with the same *total* watt-hours of capacity.

If the mass of the 4 smaller batteries is about the same as a single battery then the range will be about the same.

The trade off is packaging efficiency of 4 batteries versus the efficiency of one battery and a 12-volt to 48-volt converter.

#### RandyFL

Joined Aug 28, 2014
127
Is there going to be current limiting by way of the controller that comes with the motor?

#### RandyFL

Joined Aug 28, 2014
127
I guess trying both... 4 smaller batteries and/or a 12 to 48 volt converter.
The 4 batteries solution is going to heat up the motor : and/or the 12 - 48 converter is going to heat up.

#### RandyFL

Joined Aug 28, 2014
127
48V @1KW is 20.8 Amps, so you can use a 12V battery and DC converter upto 48V @21A or more, which is going to draw 83Amps!!! or a 48V battery capable of giving 21Amp.

Whichever you choose, 1KW is quite large for a battery to compete with.
Just bought the bike motor with controller and 2 dc to 48dc volt converters ( in case the 1st one burns up ) maxim wattage 1200 ( converters ). Will try the converters first as I have several auto batteries laying around in the garage somewhere...
R

#### RichardO

Joined May 4, 2013
2,271
Will try the converters first as I have several auto batteries laying around in the garage somewhere...
R
The car batteries will work for "bench testing". Unless they are sealed, the car batteries will likely drip acid when you lean the bike.

#### RandyFL

Joined Aug 28, 2014
127
The car batteries will work for "bench testing". Unless they are sealed, the car batteries will likely drip acid when you lean the bike.
It’s my wife’s bike so I would step thru it instead of leaning it to get on...
How do compare a car battery to 12 volt 12 ah... I’m used to a car battery that’s 12 volt dc with 500 - 600 cca ( cold cranking amps ). I understand the concept in amp hours but I’m not sure about doing ....

1 auto = 4 - 6 12 volt ah batteries?
R

#### shortbus

Joined Sep 30, 2009
8,190
Don't know the answer to you question above, but don't think a car battery is the way to go for your motor. Most hings like this that use a lead acid type battery, like say a trolling motor, use what is called a deep cycle battery, if you want the battery to last.

#### RandyFL

Joined Aug 28, 2014
127
Don't know the answer to you question above, but don't think a car battery is the way to go for your motor. Most hings like this that use a lead acid type battery, like say a trolling motor, use what is called a deep cycle battery, if you want the battery to last.
Absolutely. Agreed. I’m walking thru this blindly. Any recommendations or pointers r greatly appreciated. As I understand it ( so far ) car batteries is probably the worst way to go. But are great for bench testing.

#### shortbus

Joined Sep 30, 2009
8,190
But are great for bench testing.
As long as you don't discharge them below ~10V. That is considered flat for a car battery.

#### RandyFL

Joined Aug 28, 2014
127
As long as you don't discharge them below ~10V. That is considered flat for a car battery.
Thanx. What happens to a car battery just sitting on a block of wood for a period of time say like a year...
Will it still hold a charge or do they self destruct?

#### shortbus

Joined Sep 30, 2009
8,190
Thanx. What happens to a car battery just sitting on a block of wood for a period of time say like a year...
Will it still hold a charge or do they self destruct?
My experience is, it's a toss up. Think it depends on how good a shape it was when taken out of the car and stored. And if you have a 'modern' "smart" charger, you may have to jumper the old battery to a running car to get the voltage back up to the point that the "smart" charger will even try to charge it.

#### RandyFL

Joined Aug 28, 2014
127
My experience is, it's a toss up. Think it depends on how good a shape it was when taken out of the car and stored. And if you have a 'modern' "smart" charger, you may have to jumper the old battery to a running car to get the voltage back up to the point that the "smart" charger will even try to charge it.
I have like 3 or 4 auto batteries that I have laying around in the garage in various “ states “. That I could prolly bench test this contraption, that arrived on my front door today. Just for giggles I googled up battery pack. And found a battery pack ( stand alone item ) that’s 48v , 1000 watt and 20 ah

#### oz93666

Joined Sep 7, 2010
737
Lead acid batteries are never used for e bikes they would weigh too much. And when the bike falls over because it's top heavy you have sulphuric acid everywhere ... lead acid is FOUR times more heavy than the Li-ion of the same capacity .. there's not much difference in the price .... many youtube videos on making these ebike battery packs from 18650 cells , or you can just buy them ready made.

Edit ... just seen you already have some lead acid already ... the only way to do this is to have a small trailer you tow behind the bike with all the batteries in it ... it would be easier to use Li -ion