Advice - Adding a booster battery ?

[bilabonic]

Hi all

Bikes been brill so far. Bafang rear wheel 500w with 36v/20ah battery from
BMS.

Is there a way I could add a 6cell booster battery as I have a charger and alarms/connectors etc.

Could I purchase a 6 cell battery or are supplied ones to high a voltage.

I am looking for more speed top end for about 10 miles if possible.

Thanks

 

[cwah]

I'm not sure if it's going to be easy as you have a BMS in your current battery.

What you can do is either:
- Replace the current BMS by a 48V one. Then re-solder your pack to increase voltage. It's going to be long and difficult. Especially if you start.

- Sell your current battery and buy another one. Maybe the simplest solution time wise.

 

[KirstinS]

You can add a booster battery - the exact limits of which depend on your contoller (I presume its a 500w controller of about 20a?), the c rating of batteries used, and the motor windings

I have a 250w 8fun motor and am using a 250w 17a KU65 contoller from BMS battery. I have a 36v bottle battery with panasonic 18650 cells inside (9ah)

I have a booster battery made of unknown brand 18650 that is about 11ah and 7.4v nominal.

So my bike is now 44.4v nominalm voltage ( or about 50v hot off charger)

The booster is connect in series, put into a seatpost bag and has a lipo voltage alarm

I charge my batteries separately using the charger that came with the bottle battery and an IMAX B6 for booster cells (also helpful for testing cells/charge/discharge and balance charge)

I now get 22mph real world speed hot off charge recduing down to about 18mph when battery drain. I dont want to be going faster than 22mph so for me its perfect

I like the fact I can plug the booster in or not - i like to keep things legal when taking the kids out


I'd have thought you could go to 48v quite happily and I'm informed, as a rule of thumb, you should expect about 10% speed increase per 3.7v nominal increase

The biggest problem for you might be what to make the booster battery out of. I have used 18650 cells similar to my main battery. They both suffer from sag under load as have about 1c rating.

I'm not sure what happens if you mistach c ratings. So if your main battery goves, say, 5c but you make a booster pack of 1c

cheers
K

 

[KirstinS]

I'm not sure if it's going to be easy as you have a BMS in your current battery.

What you can do is either:
- Replace the current BMS by a 48V one. Then re-solder your pack to increase voltage. It's going to be long and difficult. Especially if you start.

- Sell your current battery and buy another one. Maybe the simplest solution time wise.

If you charge them separatley then this doesnt matter EXCEPT that you will lose the low voltage cutoff

 

[trex]

If you can change your BB than you can fit an 8-Fun BBS01 crank drive kit. It'll give you 22mph on 12T rear sprocket @ 36V.

 

[103Alex1]

The controller is 30A not 20A.

If you can change your BB than you can fit an 8-Fun BBS01 crank drive kit. It'll give you 22mph on 12T rear sprocket @ 36V.

^^ Think he's already got about that speed but is looking for 30+mph assisted without losing the oomph of the 500W motor already fitted....

 

[Deleted member 4366]

The KU123 controller has 63v capacitors. I ran one a 64v, which worked OK, but there's no guarantee. The standard battery goes up to 42v, so you can add 21v more, which conveniently is 5S. After that, you need to change the main caps to 100v.

There's two things to look out for: Firstly, you need a monitoring system for the booster pack - a voltmeter and/or cell alarms; secondly, you need to ensure that your battery has a working LVCin the BMS. if you only add a 10aH booster, that won't be a problem because you'll never flatten your main battery, assuming that you always charge it when you charge the booster. You only have to connect the booster in series the right way round. Make your connections fail-safe or you could end up damaging something - You'd have an explosion if you did it with lipos.

Here's a 12v (3S) battery that has a BMS, charger and everything, so plug-and-play - just join it in series.
12V 20AH 500W E Bike E Bicycle Scooter Waterproof Lithium Battery and Charger | eBay

 

[Zebb]

Kirstins

quote/
I have a 250w 8fun motor and am using a 250w 17a KU65 contoller from BMS battery. I have a 36v bottle battery with panasonic 18650 cells inside (9ah)

I have a booster battery made of unknown brand 18650 that is about 11ah and 7.4v nominal.



I have the lifepo4 battery pack 36v, can i add a 7.4v lithium pack in series to mine would that be a problem
having two different kinds of batterys.

Thanks

 

[trex]

The controller is 30A not 20A.



^^ Think he's already got about that speed but is looking for 30+mph assisted without losing the oomph of the 500W motor already fitted....

Just found a very read on endless sphere about baby boomers the bell curve of riding speed.. we sooner or later will have a few close shave moments.

Endless-sphere.com • View topic - New Bafang Crank-drives

 

[KirstinS]

Kirstins

quote/
I have a 250w 8fun motor and am using a 250w 17a KU65 contoller from BMS battery. I have a 36v bottle battery with panasonic 18650 cells inside (9ah)

I have a booster battery made of unknown brand 18650 that is about 11ah and 7.4v nominal.



I have the lifepo4 battery pack 36v, can i add a 7.4v lithium pack in series to mine would that be a problem
having two different kinds of batterys.

Thanks

I'm afraid I have never got to the bottom of that question . The general rule seems to be dont mix chemistries. On the other hand people have on Endless Sphere forum. I just dont undertand the various risks

I stuck to same chemistry - maybe you could too and just buy a lifepo4 booster. For example

3s 20000mAh LiFePO4 Battery Pack

The main reason i was drawn to the booster rather than simply get a battery of increased voltage was the cheap cost of doing so. Buying a premade booster pack rather removes that cost advantage

Same goes for Lipo - I've no idea if that can be mixed with Li-ion 18650 either and they are, at least, the same nominal voltage

 

[Zebb]

I'm afraid I have never got to the bottom of that question . The general rule seems to be dont mix chemistries. On the other hand people have on Endless Sphere forum. I just dont undertand the various risks

I stuck to same chemistry - maybe you could too and just buy a lifepo4 booster. For example

3s 20000mAh LiFePO4 Battery Pack

The main reason i was drawn to the booster rather than simply get a battery of increased voltage was the cheap cost of doing so. Buying a premade booster pack rather removes that cost advantage

Same goes for Lipo - I've no idea if that can be mixed with Li-ion 18650 either and they are, at least, the same nominal voltage

I appreciate the reply and help many thanks, I couldn't find a definite answer either so was why
I asked.

Again. Thank you.

 

[KirstinS]

I appreciate the reply and help many thanks, I couldn't find a definite answer either so was why
I asked.

Again. Thank you.

And if you ever do get one - please share !

 

[bilabonic]

Some great options guys cheers.

I honestly think my best option is to sell my cell pro 6 charger. My harnesses to put six, six cell batteries in series/parallel. Sell my current battery and get a 48v one from BMS.

My only problem would be the dimensions ?

I would also most probably upgrade the rear wheel to the 36v/500w, 270 rpm.

I have mate who would buy my kit off me at the price I paid.

 

[103Alex1]

Some great options guys cheers.

I honestly think my best option is to sell my cell pro 6 charger. My harnesses to put six, six cell batteries in series/parallel. Sell my current battery and get a 48v one from BMS.

My only problem would be the dimensions ?

I would also most probably upgrade the rear wheel to the 36v/500w, 270 rpm.

I have mate who would buy my kit off me at the price I paid.

^^ getting the complete battery instead sounds very sensible to me if you can flog the 1st kit. Be interested to see how the CST motor performs at 48V and the range you get off it. If you're going to keep going with the eBiking, why not get a Cycle Analyst - it really is a very useful/interesting thing and you get real time display of the W actually drawn as well as all the usual speed/Wh consumed stats too.

You'd get about the same Wh off a 15Ah 48V battery as a 20Ah 36V one .... but maybe having the 20Ah 48V one would be helpful if you intend using the bike at higher speeds. Maybe someone on here has bought the 48V one and can let you know the physical dimensions ?

 

[Deleted member 4366]

Kirstins

quote/
I have a 250w 8fun motor and am using a 250w 17a KU65 contoller from BMS battery. I have a 36v bottle battery with panasonic 18650 cells inside (9ah)

I have a booster battery made of unknown brand 18650 that is about 11ah and 7.4v nominal.



I have the lifepo4 battery pack 36v, can i add a 7.4v lithium pack in series to mine would that be a problem
having two different kinds of batterys.

Thanks

The answer is yes. It shouldn't make any difference what chemistry you have when the batteries are in series, but you must monitor the booster pack. Ideally, you want to have a booster pack with more aH than the main battery, and you need to check that your main battery's BMS shuts it down at about 30v, bearing in mind that your controller will cut off at 31v, so you need some way of running it down without the controller, bearing in mind that if the BMS doesn't have LVC, you can damage it by going below 30v. Alternatively you can assume that your BMS doesn't shut off, and use a voltmeter to monitor each pack until you're sure. The problem is that your main pack mustn't go below 30v and the booster 6v, which makes 36v. The controller won't shut off until 31v, which is too low.

 

[bilabonic]

^^ getting the complete battery instead sounds very sensible to me if you can flog the 1st kit. Be interested to see how the CST motor performs at 48V and the range you get off it. If you're going to keep going with the eBiking, why not get a Cycle Analyst - it really is a very useful/interesting thing and you get real time display of the W actually drawn as well as all the usual speed/Wh consumed stats too.

You'd get about the same Wh off a 15Ah 48V battery as a 20Ah 36V one .... but maybe having the 20Ah 48V one would be helpful if you intend using the bike at higher speeds. Maybe someone on here has bought the 48V one and can let you know the physical dimensions ?

Getting the dimensions would be great, if BMS even have a standard though ??

I have seen these on Ebay BUT the output current seems very low -

48V 15AH Portable LiFePO4 Li-ion Rechargeable Battery for Electric BIKE Scooter | eBay

 

[Zebb]

The answer is yes. It shouldn't make any difference what chemistry you have when the batteries are in series, but you must monitor the booster pack. Ideally, you want to have a booster pack with more aH than the main battery, and you need to check that your main battery's BMS shuts it down at about 30v, bearing in mind that your controller will cut off at 31v, so you need some way of running it down without the controller, bearing in mind that if the BMS doesn't have LVC, you can damage it by going below 30v. Alternatively you can assume that your BMS doesn't shut off, and use a voltmeter to monitor each pack until you're sure. The problem is that your main pack mustn't go below 30v and the booster 6v, which makes 36v. The controller won't shut off until 31v, which is too low.

Thank you once again for your input.! I take on board all you say and fully understand. It's very much appreciated.

 

[Deleted member 4366]

Getting the dimensions would be great, if BMS even have a standard though ??

I have seen these on Ebay BUT the output current seems very low -

48V 15AH Portable LiFePO4 Li-ion Rechargeable Battery for Electric BIKE Scooter | eBay

That battery's 20 amp continuous, which normally means 40 amp burst; However, I wouldn't recommend that type because they have lots of cells welded together, and are easily damaged.

I just stumbled on this supplier if you want to be a guinea pig:
holidayrc28 | eBay

 

[103Alex1]

I just stumbled on this supplier if you want to be a guinea pig:
holidayrc28 | eBay

... even has dimensions on that one . You could always ask Frank @ Xipi if he'd sell you a battery ... I think most of his are 48V and they get used for backpack versions so must be available separately from the cubes.

 

[bilabonic]

That battery's 20 amp continuous, which normally means 40 amp burst; However, I wouldn't recommend that type because they have lots of cells welded together, and are easily damaged.

I just stumbled on this supplier if you want to be a guinea pig:
holidayrc28 | eBay

I've fitted a loads of those plastic junction boxes they have used to house the cells over the years.

Wonder how much it would actually cost to make yourself buying cells/BMS ?