Even so, great idea... Lets do this with images... I'm using AAA cells for two simple reasons, one I have them lying around... Nad two it's easy to see wich way I turn them since they are not uniformly green... (BTW, yes I know AAA's are just 1.5V...)

These two cells are in series, making 3.3 + 3.3 = 6.6 V...


Here each two are in paralell, still making it 3.3V per pair, but with double the amount of energy...


These 4 cells are if you imagine buss-bars across + to -, a 4 cell string in series making 13.2V...


And this is the final pack configuration, the same as before but pairs connnected across both poles first, then the 4 packs in series like the image before...


Her you would have one wire coming out of each of the outer pairs, making the positive and negative pole sit on the top, each end...

 

So on the last two images, with the packs in series, you're only connecting one side of each battery (pack) to the next in series, correct? So the end result would be that it would essentially be the same as your first picture, just lined up in a more convenient way for our use (and four instead of two)...

Or are you connecting both sides of both (packs of) batteries... seems to me like this wouldn't work because everything is connected to everything and there would be no positive or negative pole anymore...

 

Half right... Picture three is a longer string of picture one, folded, just like you say...

Picture four is doing the same thing, using the pairs in picture two instead of individual cells... An each pair is connected at both ends...

Ie, you take this...


And "fold it" into this...


When you make pairs like this, and connecting both ends (+ to + and - to -) you are just making two small 3.3V cells into one larger cell, still the same 3.3V... Think about it in terms of water again... Two pipes along each other holds the same amount of potential, ie the same height, but double the volume... Put the two pipes together into one long pipe and you are making the potential higher, ie greater height, but here the anology isn't working 100% since you still double the volume with the water... Electrically you don't... Voltage increases but not the "volume" as in Ah...

 

Perfect! That's what I was trying to describe when I said stacked vertically...

And as a mechanical byproduct of the setup, if you were to not tape that group of cells in your last picture, but only leave them attached where you connected the 3.3v packs to each other, they would sort of unfold out (depending on the flexibility of the connector that you used). I'm just sort of "seeing" it mechanically, doesn't really have anything to do with the voltage, volume and that sort of thing.

I feel way better about why/what I am doing now...

And your explanation of cells out of balance and cells was great too... the reducing of the less charged cell by pairing it with a charged one and the overall effect of the loss of charge as a result.

So, when do I take my test? And is it multiple choice?

 

That's the beauty of cell balancing... If the difference is small to begin with, it get's smaller on it's own as long as you don't leave the middle portion of the charge... Ie don't charge or discharge completely...

But if it's large, it get's larger on it's own since at any one point where you even approach the edges of the middle portion one cell will actually hit the edge... do that enough times or a few times good and proper and you reverse a cell... Ie bad...

Yeah, but metal connectors doesn't really fold well... Plus it's not good for the cells to put loads on the endcaps... So in theory, yes... In practice, nope... Bad idea to fold stuff...

As for test, you do that when you crank your bike over, and I'd say it's a true or false one... Either you blow **** up, or you go riding...

 

This might help

Red is hooking the battery cells up in parallel increasing the capacity or amps the cell pack can put out. there would be a red connection at the bottom of the cells also.
Green is hooking the new cells up in series increasing the voltage of the cell pack has also with connections at the bottom.

I also have a question. can you just modify a dewalt charger to balance out the cell pack. sounds like that would be easy to do cut and extend the wires add clamps and should be a done deal. or maybe take the top of an old battery that you could just put in the charger with the extended wires with clamps on the end.

 

No, actually not helping... Sorry, but that's not right as in that picture... If you hook the same + end as the cable to the - cell beside it, the result will not be 13.2V... And is you connect all 4 across both top and bottom, you just shortcircuit them...



This is a correct image... The lines at the bottom are kind of "see through"...

Yeah, you can probably modify the DeWalt charger, but that is making things more compliated than it needs too be since you don't know how it works...

But if you do the configuration like we have talked about, you have essentially turned 8 cells in 4 by pairing them in paralell... Then just about any charger&balancer unit for RC products can actively balance it, as long as you pull out the wires for that... It will take a lot longer than the quick charge, and doing it that slow more than very periodically will damage the cells in other ways, but certainly doable...

Here is a bunch of them... http://shop.ebay.com/?_from=R40&_trk...22e+bike%22%29

But let me say it again... with 4 cells in a string, unless you intentionally try to get the cells unbalanced, they will stay in balance during normal usage... As long as they are resonably balanced when you first solder them up... As in, pair them, then temporarily connect ALL + to each other and ALL - to each other as well... Then leave them overnight before soldering... Good enough for our purposes...

 

I bad thought I had it right the first time then thought about it again and got it wrong by adding to many green wires sorry you can see I edited it two times should have left it alone the first time lol. I only clam to have a high school science education. Does it mater where you make the connection with the green and red wires ( does it have to be in the middle ) just thinking it would be easier to have one solder joint with two connections instead of 3 joints and don’t see why it would mater where you grab the electricity from as long as it is in the right sequence of keeping the paired cells in series + to – to + to - again.

As for the DeWalt charger I just happen to have a bunch of them as most people who do a lot of home remodeling they are handy tools and you get a charger when ever you buy one. I have never owed an rc unit at all but they look like a lot of fun.

Down the road if you make up a bunch of these packs again I would be interested in getting one think it would save me money as you say the dewalt batteries are not as good ( I only need the 8 ) I would also like to get one of your charge indicators at the same time to save on shipping. If I remember right you mounted the lights in the tachometer and it looked like a well thought up integrated ad on.

Thomas

 

Hey, it was close... And besides, with them in your hand you would probably have seen you error before making the shortcircuit... Things are usually more obvious once you have them in hand...

Well, no there is no difference as to where you put the "green" connector, on the side or in the middle is the same... Just as long as you don't overheat the cells by the soldering, and at that point it becomes about the same difficulty all over...

Actually the DeWalt cells are pretty good quality for the cost, better than the copies and rejects, but not as good as the new cells...

Hmm... how many chargers do you have? more than you need? I could dissect one and see if it's easy to re-build to our purpose...

It seems like there are more interested in getting the packs already made and skipping the soldering, so if enough people want's in (even number of pack/cells for the bulk order) I'll gladly do it... I'll put you on the "possible" list...

Yeah, I can easily make the charge indicator with the LED's on short leads so you can sneak them into the cluster somewhere and hide the circuit in the back, that's how I did mine...

 

I dont mind doing the soldering was just thinking of cost and quality if you get a batch of cells and the shipping is not bad i would be in for some as a pack or just the cells. pm me with you address and I will see what it will cost to send you a charger if you dont mind one of my older ones. or one that will just do a 14.4 battery.

 

Sorry for not staying up to date on this thread!

The problem I had with my pack was that a cell died. This is not uncommon with these cells as A123 makes two different versions and I'm using the cheaper ones (from eBay). I found the dead cell and have replaced it. It's now charging up to full pack voltage but I haven't had a chance to test it on the bike yet. It's December and my bikes are hibernating!

Failures like this are not unheard of with the Speedcell packs, which use the same cells. I'm assuming the Turntech packs are the same, as would be anything made from eBay-purchased cells. I keep the heat off in my shop unless I'm in there, so it can get into single digits quite often. I'm being told that's what killed my battery but I don't know if I'm buying it 100%. Lithium chemistry cells don't like the cold from a power output perspective, that's for sure. Just to be sure I'm keeping my pack inside my house until spring when I can test it some more.

 

Actually, the A123 cells have no problems being thrown in a freezer for all they care, as long as they are charged when they go in there... So I wouldn't buy into that if I where you... My RC packs was kept in the shop well below freezing the last winter and it made no difference... But they get discharged "faster" in that condition, so they might not be more than half charged come spring...

As far as power output when it's cold, they are to some extent "self heating" ie once the crank have made a full rotation or so, the current throughput have heated the cells and they crank just as well as a hot summer day... So as long as you have that reserve, they will crank the bike or car or whatever down to about -30C ie at the point where you might need to thaw out the oil...

One thing that is more likely to have killed that cell of yours is cell-reversal, ie the cells became to unbalanced and then was run flat once to much and one cell switched polarity and becomes junk...

 

Well, if enough are interested to get the price down I'll probably do another order come the new year, once people's wallets have recouperated from X-mas...

As for chargers/balancers... Well only if you have one to spare that that isn't used or even busted... I have an drop-shipper for my eBay purchases, I'll PM that address to you...

EDIT:

Never mind the charger... A little research and I found a way to combine a few ideas to a balancer/voltage guard... It still "top-balancing" the cells which I generally dislike, but if set at 3.4-3.5V instead of the 3.6-3.7V that a fully charged A123 cell will reach they should keep you in the "happy zone"... It's manual, ie it doesn't cut the charge voltage, instead it will light a LED and you disconnect the charger and it will balance out the cells... When that's done, you start charging until another LED lights up... Repeat... Once all 4 LEDs light up, you have the set voltage in all cells of the pack...

Cost should be about $4 per cell, so $16 for a 4 cell pack, make that $20 though, so I'm not making promises I can't keep... Ie that is a 4S1P (4 actual cells) or a 4S2P pack (8 actual cells in pairs of two) and it should handle up to 3A charging voltage... Also it needs a "dumb" charger, not a computer controlled "smart" charger that will be throughoutly confused by this and end up overcharging it severely...

I still say that you will never need it... But if anyone want's it, I'll gladly build it... I'll need one component that I don't have at home, so I'll test my prototype tomorrow...

The one good reason for having one, is to occasionally balance the pack off the bike... Say once every other month or so or at spring & fall... But using it on every charge is pointless, and since we are charging on the bike also impossible...

 

[quote=Tweety;288391]Actually guys, I don't like being the "know it all wiseguy", but it seems we are getting into the field of misinformation now...
+1
bought one of the(123) battery Tweety build a month ago. Been riding to work, and the weekends in 15-30 degree temperatures, running powered-"grip warmers, heated vest" - and this past weekend -The battery(and charging system) carried "grip warmers, and two heated vests(my wife(thearpy)ha ha. Plus the 2001 Shawk has this clock pulling on it all the time...
I believe it is a 8 cell battery- (yet ask Tweety)
Just a supporting input....

 

Yep, it's an 8 cell 4S2P battery... Thanks for the props...

 

Well... Since we are discussing balancers and chargers... Let me make it more clear what I'm talking about when I say you don't need a balancer when using it on a bike...

This is where we start, with 8 cells... They all have different capacity... Ie they aren't completely identical... Now as I'm making a visual representation, I'm obviously exagarating the difference so it can be seen... Real life % is smaller...

What we do then, is to match them up in 4 pairs that are as equal as possible (or for the quick and dirty, just pair them)... The two cells paired together will balance each other... When one becomes more charged than the other, that transfers over until they are both equal... The transfer is small and completely harmless... It also means that they run out at the same time since they will be in balance at all times... But these pairs all have different capacity between them... One pair will be the weaker pair, running out before the others...

Regardless of that, we string them together to make a 12V equivalent pack...

 

Now that we have these 4 pairs, we string them together and charge them up...

If we charge them on the bike, they remain in the same balance as when they started...

If we put them on a balancer & charger or use a BMS system, they get balanced... There are two ways of balancing the cells...

Top Balancing - meaning they are even at the top end, all of them reach full at the same time... This is the easy way of balancing stuff... You just bring out a wire from each cell and charge them indiviually until all of them are completely full...

This is the way DeWalt balance them... This is the way a lot of people balance them...

And this is in my mind about as intelligent as setting them on fire with a blowtorch... You WILL end up with damaged cells sooner or later...

There is a reason why people do it though... This is the only way you can balance cells while charging them...

The reason you will damage the cells asre pretty obvious when you look at a visual image of it... Topbalancing means the top end is level... And that means the bottom end is jagged...

The cell with the least capacity runs out first, but there is still energy in the pack, so it keeps pumping out power... That means the now empty cell is destroyed...It is used as a conduit for the energy, not delivering energy... That means you reverse the polarity of it and it becomes useless... In a 4S2P soldered pack that means 2 of the 8 cells are now just along for the ride as dead weight...

 

The next option is Bottom Balancing - this cannot, in any way, be done at charging... It is impossible... But it is the smart way of balancing the cells... Ie doing it this way you will not damage the cells...

The reason for this becomes equally apparent when you see it visually... The bottom edge is straight, with the jagged edge at the top... No matter how you try, the energy will drain out, leaving all cells to run flat at the same time...

Meaning all of them hit the "knee" on the charge curve at the same time and the pack drops well below 12V, and in that way actually protects itself in some small way... The reason is that no bike will run or turn over very well at ~10V and you will notice it...

The only way to achive this is with a BMS, a Battery Monitoring or Management System... A smart circuit that sits in the bike or the battery and monitors energy, and balances the cells actively, the same way each pair passively and automatically does by them selves... The result is that any small imbalances disapears and the pack runs out evenly...

You cannot make this happen by charging alone... If you use a BMonS (Battery Monitoring System) you can collect data while running and use that to charge them in balance this way, though...

All of this costs stupid amounts of money...

 

The best option, the option I recommend, has really nothing to do with balancing, or charging, but more common sense...

The basic premise is that the cells are safe from harm as long as all of them contain energy... Ie if they all run out at different times this is bad, and if they all run out at the same time this is good...

But what if they run out at different times, but you keep them in the "safe zone"... Ie never charge them 100% (top balancing) or discharge them 100% (bottom balancing)... Ie none of the above...



If you keep it inside the green lines, no cell ever runs out... No cell is ever charged to 100%... And no cell will become a conduit for the other cells, making it reverse poles...

So how do you do this? It's easier than you might think... Charge all cells almost full, and cycle this with discharge two or three times to make the chemistry active and all cells be "awake"... Discharge them until they are all completely the same, ie at the bottom knee... 2.8-2,9V is safe... Pick a number and make them all the same... Then charge them all to the upper knee, ie at 3.4-3.5V...

Now solder them together, stick them in a bike and go riding...

As long as you ride the bike, ie not torture it on a dyno, let it sit an idle on the sidestand with the highbeam on or whatever dumbass move you can think up, it will never run flat and never charge 100%... It will stay in the safe zone, and the cells will never be damaged...

If you accidentally run it flat, charge it a little, to about the middle of the charge curve, start the bike and go riding... The cells are now bottom balanced... Whohoo! good for us... But they will slowly drift towards middle balance on their own... Ie small differences...

If you however put the pack on a charger and fill it up... Well, we did figure out that top balancing was a bad idea, right?! So don't... OK?

 

End result... You don't need a balancer... You don't need a fancy charger...

You do however need a "dumb" 14.4V 0.5-5A powersupply for emergency charging... A basic cheap as dirt SLA charger with no buttons what-so-ever that provides above 0.5A qualifies...

And if you want to be extra safe... You need balancing taps on the cells so you can do that same balancing act as I described above for assembly once each season or soo... For that you need a top-balancing charger with individual voltage control and an adjustable cut-off... Ie run the pack down to below 50%, charge it until each cell individually hits the knee, not 100% like all chargers comes pre-set for... Such a charger cost enough to buy you three packs...

I can however build that balancing circuit as a passive, manual one... And you can use it manually with that "dumb" charger... Like I said <$20 for it... But do you really need it? Nope...

My own personal pack has the balancing taps, for testing... It has kept to middle balance pretty stubbornly throughout it's lifetime... And the only time it need a little help was when I deliberately tried to kill it... Running it flat by mistake from the PITA killswitch only meant it needed 4-5 riding cycles to get back to it's own internal balance...

 

All very interesting and informative - but I think it is taking time away from the GEAR POSITION display!

Get back on it and I'll leave this thread alone!

 

Well... since the PCB's are at the manufacturer being produced, all I can do with that is sit on my *** and wait... And seeing as it's some stupid holiday, well... You figure it out...

 

so tweety when you construct the packs yourself you match the cells right? what if the cells were not matched well? does your safe margin , the "middle zone" become a smaller range that you can stay within?

 

Yep, I match them as best as possible... The thing is, when I do this, I order 50 or 100 cells so I got a few to choose from and I'm working with cells of good quality... Plus I match the pairs as good as possible, the result is that some packs have a slightly smaller capacity and others have a slightly larger, but the difference is almost unmeasurable... The reason is that I value the balance over the actual capacity since the difference there is small enough that it's not making any difference in usage, it probably equivalent to 2-3 seconds of running your headlight...

The effective safe range for a cell is roughly 90% of the capacity... Ie the top and bottom 5% is "unusable"... If you want to increase battery life, you make that 80%, making it 10% each end... With a charging system in good working order, you will stay above the bottom 10% without any problems unless you mistreat the pack... The top is the same, as long as your charging system isn't overcharging (Bad R/R) or you manage to do long hauls at contant throttle, maximum efficient RPM for the R/R... Which would mean one stupendeous coincidence...

The actual variance on the cells I have measured are less than 2%, mostly around 1%... So with good quality cells the range is basically the same... With DeWalt cells, I'd say it's possible it's going to be a bit more, say <5%... Still within the margins...

What does become a problem is that with a DeWalt pack you have less cells to work with... So yeah, the band is a bit more narrow... Also, your methodology and tools for measuring... Like I have said before... I'm an EE, and I have a bit more accurate tools than the average multimeter to use...

But if you do charge them cell by cell, like described, at constant current and voltage and measure the time to charge knee-to-knee, you get a good enough number for matching them up... That makes the pack hard to kill, but might not give you the last Ampere minute or so of capacity...

BTW, the short answer... Yes, but the difference is very, very small if you do it right, and resonably small even if you just slap them together... The effective safe zone is the middle 80% of the smallest capacity pair...

 

my next question is if you switch your rr to a fet system from a diode then you might be charging at a higher voltage and could this not damage the pack? does running a fet rr change the story for the worse? it also sounds like doing this on a touring bike may be a problem no?

 

tweety, others, any insight on this? thanks

 

The LiFePO4 packs run at a higher voltage than a lead acid cell battery, so I don't think it would be a big deal.

When you say a FET system charges at a higher voltage, what is the actual value?

 

I can't recall exactly, I think it was tweety tha tmight have said in a different thread regarding rr's that it provides a higher and more consistent voltage. I can't recall the exact value, i'm sure that it would vary from unit to unit...sorry

 

If it's an r/r designed for a lead acid battery then it would be just fine for the Lithium pack.

 

Well... No... The fact that it's a Mosfet design has absolutely nothing to do with the voltage... You can make a Mosfet R/R at just about any voltage you like... It's a matter of how you design it...

But it will give you slightly higher voltage than the OEM VTR one... Ie the correct voltage for a lead acid cell, which the OEM one doesn't give you... And since the LiFePo4 does use a higher voltage, no it doesn't harm it, it prefers it...

BTW for reference, the R1 R/R uses Mosfet's...