12s8p charging configuration advice?

K

kristafervale

1 mW
Joined
Apr 2, 2015
Messages
16
Hello everyone,

First let me just say thank you to this amazing community for all the valuable information you all have collectively provided! I've done a lot of research in the past few weeks and over and over again the best information has come from reading all the really great posts here!

I'm in the process of putting together what I hope will be a reliable daily commuter bike for use in the San Francisco Bay area, which means quite a few major hill climbs every day. The main considerations for this first bike were cost and reliability not max speed etc.

For the Motor / Controller I went with this inexpensive ebay sale:
http://www.ebay.com/itm/221691273393?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT

I can't find any good information on what type of controller it uses, what kind of power the motor pulls at full throttle etc so any help in learning how I may go about figuring that out would be greatly appreciated!

Since I'm on a budget I decided to try and take on the task of building my own 12s8p battery pack out of some bulk cells I purchased from an ES member.

Here is a link to the spec sheet they sent me about the cells.
https://drive.google.com/file/d/0Bx2c0o3VP6lES0RKeFl2XzV6ZDRsMnozNUJ3SlY3U2pteEpV/view?usp=sharing

I plan on creating 12 8p packs out of these and then wiring them in series for the max 12s8p pack. I would like to balance charge these using an iMax B6AC v2 which I already had.
http://www.amazon.com/Genuine-SKYRC...8&qid=1429029610&sr=8-1&keywords=imax+b6ac+v2

I'm hoping to have as an end result something similar to what ES member patrick mahoney described in his post:
http://endless-sphere.com/forums/viewtopic.php?t=826

But I've hit a couple of questions now that I thought I would post here in hopes that they aren't too N00Bish. I've done some searching but can't seem to find the right information and with the risk involved hoped you all may be able to steer me in the right direction.

1.) Is going with a 12s8p setup the best way to go about making this pack? Is there some more optimal configuration I should consider?
2.) When creating these packs if I use a the above charger and a parallel charging board would there be any benefit to wiring anything in series during charging or would it be better to just charge the individual 8p packs 6 at a time?
3.) should each of the 12 8p packs have a BMS or should the entire 12s8p pack have a single BMS and am I right that I would only use that when riding, i.e. not when charging?
4.) if I do go with 12s8p my plan is to hard wire (soldier or spot weld) the 8p packs individually and then use wiring harnesses to create the discharge / charge wiring separately. I THINK that means that I just need a single JST connector on each 8p pack and then something to make 6s 16p configuration for charging is that right?
5.) Is there a learning resource, other than doing more searching here on the boards that anyone can point me to? I'd like to fully understand all the ins and outs of battery management and pack creation but the information does seem to be a bit scattered and in some cases contradictory. For example a lot of advice seems to be to make more series packs and wire those in parallel and vice versa lots of parallel packs then wired in series. Is there a gold standard or "right way" to do it?

Again, I apologize if this information is all out there already and I just failed in my attempts at research, even just links to existing information is greatly appreciated! Thanks!
 
With that charger, you will have to split it into two sections to charge it, each section will be 8p 6s.

It's going to take a looooong time to charge each section, so as soon as you can, get something faster. A 12s bms and a 5 amps charger to go with it would be your best long term solution I think.

But another option would be a 12s RC charger, like the thunder power, or the 14s hyperion.
 
QViGkZ5.jpg


here's my prototype 12s8p pack. there's a separate connector (not shown) that allows it to be broken into two separate 6s sections. could then be paralleled together to form a virtual 6s16p for charging on a 6s charger

a 50w charger will take something like 18hrs to charge it. not recommended. i use an icharger 106b+. there's also a clone of this charger at hobbyking for like half the price

the kit probably draws 22A max? so for 8p each cell only has to put out 2.75A. not a lot so you really don't have to use "high drain" panasonic CGR cells. my pack uses Samsung 26F cells, one of the cheapest cells available
 
For sure, it's going to be a slow charge with that 50w charger. But I seriously doubt that another 6s or 8s charger will be his best choice when he does fork out the cash for another charger.

Get a bulk charger and bms, or an RC charger able to charge and balance the whole pack.

Last, but not so good option, just a bulk charger, and only occasionally use the 50w charger just for balancing 6s at a time.
 
well we were on the same boat prior to my purchase of the 250w icharger. yeah i used charged that pack w/ an imax b6. had to leave it charging overnight (and then some), not safe...

i didn't want a BMS so decided to get the icharger. the turnigy clone is $43

http://hobbyking.com/hobbyking/store/__66718__Turnigy_Reaktor_250W_10A_1_6S_Balance_Charger.html

gives you more control over end voltage for better cycle life. "storage" mode. regen discharge mode allows me to draw power from the ebike battery to supplement my 12v solar setup. a bunch of other features. definitely worth the money. have no plans of using a BMS
 
Thanks guys I'll do some more research based on your suggestions.

Overclocker is there some downside to using the cells I have? Does the high discharge rating mean they are somehow not suited for the kit I have?
 
A 12s8p pack of those cells is about 850wh. Using a 50W 6s charger will take ~9 hours to charge each half, so 18 hours to charge it all from empty. If you want to use an rc balance charger to charge, I'd suggest getting a 12s charger like this or similar;
http://www.hobbypartz.com/75p-1220-charger.html?gclid=CNa3z9_N57ICFayPPAod10MAPw
It will charge and balance the whole pack in ~3 hours. Otherwise just get a 12s lipo bms and bulk charger. That may be cheaper, and will make charging easier.
 
you should build the battery up as a serial pack first, 12S1P and then combine the 8 packs together in parallel through the sense wires.

the parallel connection can be very small. 26-22 AWG is adequate.

if you build it as 8P first then it is impossible to isolate the bad can when you have to repair it. which you will, and soon.
 
kristafervale said:
1.) Is going with a 12s8p setup the best way to go about making this pack? Is there some more optimal configuration I should consider?
2.) When creating these packs if I use a the above charger and a parallel charging board would there be any benefit to wiring anything in series during charging or would it be better to just charge the individual 8p packs 6 at a time?
3.) should each of the 12 8p packs have a BMS or should the entire 12s8p pack have a single BMS and am I right that I would only use that when riding, i.e. not when charging?
4.) if I do go with 12s8p my plan is to hard wire (soldier or spot weld) the 8p packs individually and then use wiring harnesses to create the discharge / charge wiring separately. I THINK that means that I just need a single JST connector on each 8p pack and then something to make 6s 16p configuration for charging is that right?
5.) Is there a learning resource, other than doing more searching here on the boards that anyone can point me to? I'd like to fully understand all the ins and outs of battery management and pack creation but the information does seem to be a bit scattered and in some cases contradictory. For example a lot of advice seems to be to make more series packs and wire those in parallel and vice versa lots of parallel packs then wired in series. Is there a gold standard or "right way" to do it?
Click to expand...

1) optimal configuration depends on your space, and how much amps do you want to feed your controller.

2) It would be 6 at a time, you can parallel packs for charging but not in series. And the packs will not charge balanced

3) You can and must do it with only one 12s BMS :wink:

4) misunderstood from my side.

5) I have this, but is related only to 18650 packs http://endless-sphere.com/forums/viewtopic.php?f=14&t=68005
 
8P is not a pack. it is a mistake.

you will not be able to charge a battery of this size with the little imaX charger. use a regular lipo BMS and charge with a regular charger.

you are new and inexperienced like the people giving you advice. if you build the pack as 8P then you will not be able to repair it when one can goes flat and shorts.

no matter how much i emphasize this it keeps coming back to people doing the wrong thing when they build the pack.

there are people who have built the parallel packs using doubled up 12AWG wire with huge amounts of solder and all for no reason since the current does not flow in parallel through the pack. it flows in series. it is as if people have no comprehension of the physical laws that determine how current flows.
 
Thanks everyone the advice is making me feel a little more confident starting this project.

dnmun,
I hear what you are saying and will start trying to layout what the 8 X 12s1p in parallel will look like from a wiring standpoint. I am worried that my inexperience and lack of general knowledge will lead me to miss-connect the Parallel part after the 12s1p's are all complete. Any advice or links to learning resources would be greatly appreciated!

Would this (or something similar) be the right BMS for the job?
http://www.batterysupports.com/44v-...-lithium-ion-lipolymer-battery-bms-p-393.html

Can you point me to a "regular charger"? I'm unclear what that means, sorry for the n00b questions and thanks for the help!
 
The hills of San Francisco will be hard on a battery. Even with the needed pedaling it Will take.
To ride and enjoy you will need a strong battery overrated for your needs.
If if do you want to build a battery I would do it as my second battery and it will be a hobby to get all the pieces all the parts and the bike up and running.
You will save money and be on the road buying a Good plug and play battery with bms and the right matching charger.
This way you can take time to learn how a 48v ebike battery works. Which is a learning experience in it self. That many have failed at. A battery may sound simple and easy to you try to get it to work for 3 or more months.
So don't waste time and money on cheap dream buattery that will cost you the same and no guarantee to work.
Buy a Good plug and play battery and get on the road and enjoy.
 
Welcome to ES and good to see another eBiker in the area here.

I use the Meanwell LED supplies to charge my 2kWh pack. You probably want a serious charger for a big pack. The RC chargers are good for initial charging and periodic balancing, but you may need something that can charge the pack in a few hours for normal use.
 
thanks Alan, I'll look into that charger, and thanks for the welcome as well. :)

999zip999 I may well do as you suggest at the end of the day, but learning this technology is half of why I wanted to build the e-bike so if I can get it working it'll be good. If it fails (and I don't kill myself or burn anything down) then I'll definitely take your advice and look to buy a pre-made battery / charger. Thx!
 
Lots of arguments for p first, or s first. And valid reasons for each approach. A dead cell in the middle of a pack will be hard to find and remove, no matter whether you do series first, or you do parallel first. For sure, you do want to avoid making a huge block of cells you can never get a dud cell out of. Start with sections, p or s, and do some testing before you create a giant pile of cells you cannot disassemble.

Worth considering to make the pack in segments you can work with, perhaps pull out 4 cells at a time to test or replace later.

4p sections? then if you need to remove a cell, you pull out 4 cells, rather than 8. Not saying plugs every 4 cells, just a wire you can clip and reattach with a crimp or a solder.

If you do series first, then the maximum you can charge with your current charger is 6s. So a pile of 6s 1 p packs could make some sense.

Bear in mind, my advice is amateur. I've never built a pack from round cells myself. But I've seen some real birth defects here, including packs build by large companies. The last thing I'd recommend is soldering a pack from 18650's. Very easy to ruin all or at least many the cells in the soldering.
 
Don't underestimate the effort of making a good pack. There's a reason they cost a lot.

Test each cell thoroughly first. It is vital to avoid pack building with weak cells.
Parallel tested cells into replaceable sub-modules. Have a few spares. Swap a suspect module, tear it apart for cell repair offline.
Weld don't solder.
 
I reread your post and you have already bought a bunch of cells. So what kind of cells are these and how many have you bought. Are they new what brand and how do you plan on joining them together.
 
so how does one go about isolating a bad can when all 8 are spot welded to each other in parallel. how do you cut apart a big parallel strap that is spot welded to each can with no space between them to insert a cutting tool to cut the parallel strap. at least if you solder them you can unsolder them. spot welded in parallel is terminal and a total fail.

has anyone who told you to build the battery in parallel first ever had to repair a battery with a dead cell in the middle? anyone?

i have no idea why people feel the need to do stuff the same old way because that is how the chinese battery manufacturers build them. to me the mistake is obvious, but i repair batteries instead of throwing them away and buying a new one. so my perspective is totally different.
 
Dnmun your method is easier to find a bad cell. But is harder on each cell for most ebikes and the cells most people use. If you use a high grade A123 or similar quality cell you can get away with it.
But using a generic Chinese cell or laptop cell No. You will be looking for the bad cell every 2~3 months.
So what cells are we talking about ? We need an answer first.
 
999zip999 said:
Dnmun your method is easier to find a bad cell. But is harder on each cell for most ebikes and the cells most people use. If you use a high grade A123 or similar quality cell you can get away with it.
But using a generic Chinese cell or laptop cell No. You will be looking for the bad cell every 2~3 months.
So what cells are we talking about ? We need an answer first.
Click to expand...


Agreed. As long as you proper source and vet your cells, why would a single cell in parallel string go bad? It's being propped up by the other 7.
 
Hi 999zip999
I reread your post and you have already bought a bunch of cells. So what kind of cells are these and how many have you bought. Are they new what brand and how do you plan on joining them together
Click to expand...
So what cells are we talking about ? We need an answer first.
Click to expand...

I have 100 cells which have the markings indicating they are supposedly Panasonic item number CRG18650DA. They all tested at exactly 3.6v when I received them. The seller was advertising on this forum and told me that the cells were new from the factory. He provided me a .pdf of the spec sheet for the cells which is what I posted on this link.

https://drive.google.com/file/d/0Bx2c0o3VP6lES0RKeFl2XzV6ZDRsMnozNUJ3SlY3U2pteEpV/view

I can do either weld or soldier was planning on soldier because:
1.) I'm new but understand heat to be a major issue with batteries
2.) The spot welder I'm planning on using is a DIY I made since I can't afford / justify the price of a new one yet.
3.) I've never used a spot welder before.
4.) If a cell goes bad I figured UN-soldiering would be easier.

Totally appreciate all the advice and even the series vs parallel debate is informative thanks everyone!
 
If using an iron. A big old style 85watt or bigger. Cleaned and tinned witha a wet sponge to wipe tip.
Gasket on all pos. ends
Use Real flux lightly with a free chop stick or.
Tin first lightly. Don't flood.
Cool fast.
look at Drk angle thread. Except I like parallel than series.
Caution whole case is neg. even the ring of case around top of positive end.
 
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