To get the voltage needed

Ok thats great - i dont quite understand the 52 / 65 cells part, is this still or a 48V battery, better yet if you can point me in right direction where to get one

Also i was reading a 52V battery would get more speed and i se these with 20ah, would that be worth it if im changing battery anyway?

 

thanks again,

Ian.

To get the 48 volts needed, you need 13 cells connected in series for a battery.

To get the current needed, you need each "cell" to be made up of several "actual" cells (individual 18650 cells).

To find out how many, simply divide the total number of cells by 13 for a 48 volt battery, or 10 for a 36 volt battery.

52/13= 4 individual cells in each "cell"

65/13= 5 cells in each "cell" E.G. More current can be safely drawn!!

The more cells in parallel, the higher the current, so a 48 volt battery with 78 cells in total, will have 6 individual cells in parallel!

You might like to peruse this link, though I am not suggesting you make your own battery!

What is also VERY important, is the quality of the cells and the quality of the BMS, both are adequately explained in the link, which is for a 36 volt battery, but the principle remains the same.

Panasonic sell "graded cells", which have been selected to be as close a "match" in all characteristics as possible, so that the BMS has significantly less work to do!

This link might also be of interest too:-

http://www.ebikeschool.com/how-to-build-a-diy-electric-bicycle-lithium-battery-from-18650-cells/

If you ever need to buy a BMS for a 36 volt battery, it has to cover 10 cells. If you want one for a 48 volt battery, it has to cover 13 cells. They are NOT the same!!

The link above covers it quite well I find.

Wiring of the BMS MUST be accurately carried out, so I do not recommend anyone with no electrical knowledge trying to do this, NEVER EVER!!

But for the qualified people, they are available for very little money, contrary to what some people believe here, in different voltages and currents.

If you ever need to pick one, pick the correct voltage first and then go for a higher current version than you actually need! It will run cooler and last longer.

Here are two examples for 36 volt batteries:-

https://www.banggood.com/36V-10S-Li-ion-Lipolymer-Battery-25A-60A-BMS-Battery-Protection-Board-for-Ebike-Ebicycle-p-1339566.html?rmmds=search&ID=554014&cur_warehouse=CN

This BMS is high quality, very good for ebike, scooter,eboard. it designed to durable for big current. It have 25A and 60A versions, please select the one you needed. Protection board with overcharge protection, over discharge protection, over current protection, short circuit protection, temperature protection.

Chinese English, but it covers all the important stuff, as does the 48 volt version below in four different current ranges!

Here for 48 volts:-

https://www.banggood.com/Same-Port-13S-48V-2535A45A60A-BMS-PCB-Li-ion-Battery-Protection-Board-For-Electric-Bike-Ebike-p-1332093.html?rmmds=search&ID=47606&cur_warehouse=CN

For under US$30!!

If you have any further questions, just ask.

regards

Andy

PS. Do not attempt to build your own battery without a battery qualified person holding your hand. It can get VERY fraught! I am VERY qualified, but prefer to invest more money in a battery with well known high quality cells from Panasonic....

PPS. I forgot, more cells in each "cell" allow more current as I said, and a greater range too. Sorry!!

PPPS. Watch this:-

http://www.ebikeschool.com/how-to-build-a-diy-electric-bicycle-lithium-battery-from-18650-cells/

And this:-

Edited March 9, 20197 yr by Andy-Mat

We normally refer to the capacity of a battery as being the charge between the low cutoff and the high cutoff. That's 100% capacity.

 

Say you had a 10Ah battery or a 400Wh one, 80% would be after it was down 2Ah and 80Wh respectively from fully charged. 20% would be 8Ah and 320Wh down. You'd have to measure those values with a wattmeter and see at which voltage those points occur. You can't scale the voltage because it's not linear. It goes down rapidly at first, then for the larger part is a ramp, then it starts to accelerate downwards towards the end. If you scaledthe voltage to 80% and 20%, it would be equivalent to capacities of around 90% and 7%.

 

It's all academic because you should only chage an ebike battery to 100%, i.e. to when the charger gives the green light.

 

By using the 80% 20% rule, you not only kill your battery, but you give up 40% of its capacity or effectively increase your mass per amp-hour by 40%, in which case, it would be much better to get a LiFePO4 battery, which will last four times as long for the same cost and weight without all the messing about.

I saw the results of an experiment where they tested the 80% rule, and it literally doubled the charge cycles they got from 800 for 100% every time to 1600 for 80 percent. As I understand it, it is best to charge fully every now and then to let the BMS balance the cells etc, but it's better for the battery not to be charged to 100% most of the time, and you definitely don't want to leave it at 100 for any length of time.

I saw the results of an experiment where they tested the 80% rule, and it literally doubled the charge cycles they got from 800 for 100% every time to 1600 for 80 percent. As I understand it, it is best to charge fully every now and then to let the BMS balance the cells etc, but it's better for the battery not to be charged to 100% most of the time, and you definitely don't want to leave it at 100 for any length of time.

That test wasn't on a conventional electric bike battery, and no, you can't balance the battery by occasionally charging to 100% because the balancing happens too slowly. It works on the basis of a little and often, so it can't keep up if you don't do it on every charge.

 

If you really want to try 80% charging, you need to buy a customisable BMS. They are available, but quite expensive. Then you need to remove the old BMS and wire in your new one. You also need to adjust your charger to hold the constant 80% voltage.

 

When you've done all that, you can tell us how much longer your battery lasted and whether it's economically viable considering the costs of the BMS and charger.

 

As I said in my previous post, by using the 80/20 rule, you end up with a battery that's effectively 50% heavier compared with a battery of the same useable capacity, in which case, you'd be better off getting a LiFePO4 one, which will last four times as long without all the inconvenience and expense.

Edited April 1, 20197 yr by vfr400

That test wasn't on a conventional electric bike battery, and no, you can't balance the battery by occasionally charging to 100% because the balancing happens too slowly. It works on the basis of a little and often, so it can't keep up if you don't do it on every charge.

 

If you really want to try 80% charging, you need to buy a customisable BMS. They are available, but quite expensive. Then you need to remove the old BMS and wire in your new one. You also need to adjust your charger to hold the constant 80% voltage.

 

When you've done all that, you can tell us how much longer your battery lasted and whether it's economically viable considering the costs of the BMS and charger.

 

As I said in my previous post, by using the 80/20 rule, you end up with a battery that's effectively 50% heavier compared with a battery of the same useable capacity, in which case, you'd be better off getting a LiFePO4 one, which will last four times as long without all the inconvenience and expense.

 

Thanks for the clarification.

 

What do you think about the other info I found about not leaving the battery at 100% for too long?

Thanks for the clarification.

 

What do you think about the other info I found about not leaving the battery at 100% for too long?

That's probably good advice. I personally don't believe it's anything to panic about. It's not like it will kill your battery if you leave it fully charged.