Need help with DIY battery pack.

I've read/watch many of the contents regarding making DIY battery packs for ebikes ect...

For the most part the configuration that most people choose is some where along the line of a pack in combination of series + parallel connection to get the desire voltage and amp.

However that type of configuration requires balance charging, which i find is too complicated for me.

Personally I like to do this:
I would create a pack of parallel circuit of 10 batteries (so it is still 4V), wire this all up I have a very high capacity 4V pack with a positive and negative lead.

I would make multiple of these packs and connect them in series to get the desire voltage. The + and - lead out are removable (plug and play sort of thing).

My question is, do i still need to balance charge a pack of batteries in parallel like the one I describe above? If I don't, then what is the easiest solution to charge such a battery pack?

Is there a charger that will charge multiple of these parallel battery pack at the same time?

Thanks everyone, I'm new at this and I just want to make something that's as flexible as possible .

The paralleled batteries will each appear as a single large battery. If you are running them in series, they should be balanced (or at least monitored). There is no way to get around that with 'clever' wiring. A bad cell is a bad cell and it will have negative consequences in your pack. If you've got a ton of smaller cells paralleled together, you increase the odds of acquiring a bad cell, although the outcome will be less catastrophic because the other paralleled cells will help to regulate its voltage.

I am in the same page as you are. If you charge them in series, you should balance charge them for safety and to prolong the battery life.

If you charge the packs in parrallel, you can charge them as 1S and no balancing would be needed. What charger do you have in mind? The time and hassel you will have to go through to charge individual 1S packs, you would be better off to include balance leads.

Cheers.

PS: What is your Motor volt requirement? 24v/36v?

My line of thought is that I don't want to deal with balance charging, and charging individual packs isn't that bad (easier to monitor too)

if I'm doing an ebike, I'm probably going to sit around 36V, which is roughly 10 packs of batteries in parallel wire in a series.

I'm actually working on getting some 12V or 9V for LED lightning and flash powering for photography .

I have not picked a charger yet, I figured that if I don't need balance charging, I can get away with a simpler charger (or rather multiple simpler chargers), and charge the batteries up that way.

How do you imagine charging 10 separate batteries simultaneously and how is this in any way easier than just balancing using balance leads?

I would recommend 24 volts. I just got my 24 volt Leed eBike kit put together, and it way exceeded my expectation.

Attached an image of my 24 volt Bafang 8Fun rear wheel motor.

FYI: you probably will need a new charger. The stand alone charger will not deliver enough juice. It probably will take couple of hours just to charge 1S4P or more. 10P could take days

Balance charging isn't at all difficult. You will figure it out in time. The other option would be to invest in RC lipo batteries, but do so at your own risk. I wanted to take the RC lipo route, but the packs aren't nearly as reliable as lico cells.

is there a good tutorial for balance charging with wire hook up? i saw some tutorial but got confused

It's a lot easier and you will not be saving money building a battery. Get a readily made plug and play battery and charger matched to your kits demands for your battery. Matched battery to controller. Important. How can work cheaper then a Chinese. Remember he knows more.

clockwork247 said:

is there a good tutorial for balance charging with wire hook up? i saw some tutorial but got confused

Click to expand...

Its very easy. eg. if you are working on 24 volt motor kit, you may want to use 7S to get a nominal voltage of 25.9 volts (3.7v x 7).

you will need a JST type balance lead for 7S (or 10S if you decide to go for 36 volts). You can get these JST balance leads off Ebay.

You can design your batteries by using example on this site (unfortunately, it only lets you configure up to 5S, but you get the idea): http://scriptasylum.com/rc_speed/lipo.html

I have attached an image. (Basically one lead from each of the battery positive+ terminal, but only one negative (-) lead is required to be plugged into the JST balancer plug on your charger. Your voltage reading at full charge on each of the balance leads will be as follows:

Cell 1s: 4.2v
Cell 2s: 8.4v
Cell 3s: 12.6v
Cell 4s: 16.8v
Cell 5s: 21.0v
Cell 6s: 25.2v
Cell 7s: 29.4v

Hope this helps.

FYI Dont forget to invest in a volt-meter as well. Be very careful as not to short anything out. These batteries are extremely dangerous. I myself have bought my 1st pack from the vendor. You really wont be saving much in the short term. You will also have to invest in a battery spot welder. Soldering li-ions can damage the chemistry inside.

It would help if you can tell us where you live. Plus what are you running. Important.

it is not even worth wasting your time to build a pack if it is not protected and balanced by a BMS. if you cannot charge to full charge you don't even get the stored power back out.

if you build a pack from used laptop cells and no BMS it is just useless weight that will be over discharged and ruined in just few cycles if you last that long.

Is there a cheap source for premade battery?

If I was to DIY battery packs, I'm having issues with an easy method to bulk test, have anyone ever discharge these battery using resistor? those are cheap enough (a 10W is less than 50 cents), I can discharge and use a hobby charger to recharge it backup to know the capacity left on each cell (it would take a long time but i don't have to sit and wait for it).

clockwork247 said:

If I was to DIY battery packs, I'm having issues with an easy method to bulk test, have anyone ever discharge these battery using resistor? those are cheap enough (a 10W is less than 50 cents), I can discharge and use a hobby charger to recharge it backup to know the capacity left on each cell (it would take a long time but i don't have to sit and wait for it).

Click to expand...

You can use your B6 to do a quick discharge/capacity test. This probably isn't the most accurate method, but it will give you a rough idea.

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