Specialized Big Hit FSR

what a beauty. nice work mate.

Nice looking build , i will keep a eye on this Big Hit :lol:

So I have been procrastinating a bit, but I am getting small things done slowly.

I have been trying to work out which way to wire the pack.



the left way is much more prefered as it allows the packs to stand on their end, if I go the right method I will have to half the pack and lay them down.

There used to be heaps of threads about whether to parallel first/while series in the old days but I cant seem to find them anymore, I dont know if there was any consensus that this is wrong. The balance tabs will still be paralleled and I will be bulk charging the pack always, while using a hyperion checking/balancing the individual 12cells banks in between.

anyone else wire their pack this way?

from an electronics perspective I'd go with the right option to have as much power paralleling as possible to help keep it all even and flowing, but if you think the balance cables are enough to keep that in check(and theoriticaly should) then go with the left option. on the other hand you dont want to stress a wire on the balance lead if its paraleled with 2 cells 1 a bit under capacity and 1 over, it may stress the solder joins/wires / batery pcb. are you sure you cant position them how you want and parallel power and balance lead? also, just incase a power lead on one side isnt properly conected one day , that would probably cause a fire on the balance leads insulation while under high power consumption. I think you should fool proof it as much as possible, i have to do it for myself, too many drunk/tired electrical mistakes at my place..

I always build stuff on the protective side as well, but in this instance there just isn't room for either method. Realistically the problem is still there with 2 x 6s packs in parallel, there is no way to protect if one cell goes south. Though there is only the voltage gap between 6 cells not 24, a lot more possible cells to go wrong!

Im sure someone on here would of done it already, its so much easier.....I was expecting either a resounding 'no don't do that because X did it and FIRE' or a 'meh worked ok for me'. With the amount of 6s HK lipo packs floating around on bicycles surely someone??

Hey if u balance regularly and have cell monitors and do solid soldering with good insulation you should be fine.

I have also a question on my battery setup, can anyone say if this works or not. I have made a drawing in fritzing.
There are always two 6S 5Ah batterys parallel, which go in to an connector. So the batterys are not connected to 72V when the bike stands in the garage. When I want to drive I plug in an homemade connector which turnes the batterys in Serial mode like in the picture. Because my charger can only charge 6S batterys i have an other charging plug which connects all batterys in parallel. But I also need the balancer leads. So I have to connect the two batteries which are always parallel in the bike, but all balancer leads get only connected parallel if I plug in the charging connector.

so after having this for nearly 2 years I finally got around to wiring it up for a test....
[youtube]Gzue773rljM[/youtube]

hopefully it will be ride able tomorrow

F' yeah. keep going, that frame deserves to be a working bike.

paralel first then series is the consensus rodgah.

I'd make 4 blocks of 6s 2p each with one balance and a + and -. Then I'd arrange my contactor to split the pack when it was off giving me two chunks of 12s 2p to charge. I can then balance each 12s group with a Hyperion charger, or charge both at once with two Hyperions, or bulk charge at 100v and monitor/balance with cell logs.
If one cell goes south you will see it right away if you are using a Hyperion charger and the most you could kill is two cells, annoying but not much more expensive then one.
If you did 2 100v chunks there are no balancing options available to you beyond getting two hyperions and linking them together, or 4 of Hyenas balancers. Unless you plan to remove the packs for each ride and split them up. What charger are you planning to use?

I have permanently paralleled them together, then put them in series.

I use this to charge them;

http://www.bmsbattery.com/alloy-shell/457-alloy-shell-900w-lifepo4li-ionlead-acid-battery-ev-charger.html

Along with this BMS to balance them;

http://endless-sphere.com/forums/viewtopic.php?f=14&t=49820

pendragon8000 said:

F' yeah. keep going, that frame deserves to be a working bike.

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not wrong. its a beauty

I ended up wiring it up in parallel then series, and the balance tabs in parallel too, all going to 2x db25 connectors to suit my hyperion. It was a pain but it works now :lol: .

The forks need more air in them they are sagging below 50% travel when I sit on it, but apart from that its all perfect. The slow speed on the 3 speed switch is perfect for the girl friend, or anyone that wants to have a try. I dont have a lot of use for the speed that the 3rd speed gives you in most of my riding but I can see on the road it is a blast.

So I took the gopro out for a spin today....looks like i have to line up the camera more for standing up than sitting down. Enjoy......

[youtube]5QSQbD1ntK8[/youtube]

You've got those wheelies dialed.
Good to see you got it going. That cf side panel is a nice touch.

I see you made a good impression on those kids near the end of the video haha! Nice wheelies man, and superb work on the bike!

the wheelies will get better, its been a few years since I have ridden anything that will wheelie, still getting used to balance point and power curve.

Im not happy with the birds nest behind the cover(as you could see), I think it needs work but then again thats what a 'cover' is for :lol: . Again I cant take credit for most of the work on this bike.....Paul AKA Timma has done an excellent job of the frame, the rest of it I just bolted together.

What happened to Paul? He's not been on here since 16/4.. pmed him 'cos he seemed pretty down after that break up afaik.

re: Timma... I spoke to him on the phone for the first time in months only few weeks ago, he's actually travelling pretty well, looking forward to catching up with him soon... Girlfriends come and go...e-bikes are forevaaaah!

KiM

rodgah said:

I always build stuff on the protective side as well, but in this instance there just isn't room for either method. Realistically the problem is still there with 2 x 6s packs in parallel, there is no way to protect if one cell goes south. Though there is only the voltage gap between 6 cells not 24, a lot more possible cells to go wrong!

Im sure someone on here would of done it already, its so much easier.....I was expecting either a resounding 'no don't do that because X did it and FIRE' or a 'meh worked ok for me'. With the amount of 6s HK lipo packs floating around on bicycles surely someone??

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meh worked for me.
satisfied? lol.

but seriosly, ive been running my 24s pack, half 5ah half 3ah for about 6+ months now. no issues, stays perfectly balanced. I recently had somehing go wrong with my controller (internal short, havent had time to investigate yet) and drew the pack down to about 2v per cell, but after recharging slowly they're still within 10mv. None of my wiring has ever felt above ambient, at rates up to 2c average, 5c burst... and I regularly check the cells after a ride.

I doubt they'll be any significant difference under load that would cause any notably currents to flow through the balance wires, unless a cell is dying already (in which case the discharge leads being paralleled wont make much difference anyway/be the least of your problems) or unless you're pulling massive C rates. even if you managed to get a deltaV between the packs of say, half a volt (which would be a problem on its own) you would see about 10a through your balance wires (assuming a total of 50mohm through the connectors etc), which they'd take for a short while without a problem (the BC(somehting... 450?) charger charges at 8a through the balance wires, and reports are that they get 'warm' after a full charge. It'd actually be a bit less than that, since the sag of your 'weak' pack would mean a lower full pack voltage on that half, and therefore your 'strong' pack would take more of the load.

Overall, I think the idea of paralleling the discharge wires is largely unnecessary. just means more connections, more resistance, heavier and bulkier packs, and more work... for little to no benefit.

edit
just did a quick test on a very basic equivilant circuit

the middle bottom cell has a higher IR (double that of its friends). ~200a flows in this circuit, ~100 from each set of seriesed batteries. under these conditions, just 3.5A was flowing between the two strings of cells. This is by no means a perfect representation, but gives some idea just how little power would flow 'sideways' - even with double the cell IR.

now that I think about it i should have added a bit more to each cell in series to simulate connectors between each 'pack', but I still doubt it'd make much difference.

sn0wchyld said:

meh worked for me

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ha knew someone would of, its just too tempting.

If the balance wires were left unconnected I think this would be a better solution if 1 cell did hit 0v, the difference between the 2 x 24s strings is made up by 23s slightly higher/lower V instead of 6s much higher/lower V. Even if the packs are in parallel the power is still going to be pulled more so from the stronger string of cells? So the discharge parallel connection makes little to no difference? that is a good simulation, assuming when plugging the packs all together they are matched fairly well (obviously) there is only going to be small currents through the balance leads, imagine if cells at 3.2V were parallel to 4.2V 7 wire foam cutter anyone.

If I was to redo the pack in this bike again I would think about using this method, but at the moment I cant be bothered, plus it makes using the hyperion to charge impossible. I ~could~ bulk charge while using the hyperion to balance the cells in 2 groups but that seems like more of a pain than what I already do.

rodgah said:

sn0wchyld said:

meh worked for me

Click to expand...

ha knew someone would of, its just too tempting.

If the balance wires were left unconnected I think this would be a better solution if 1 cell did hit 0v, the difference between the 2 x 24s strings is made up by 23s slightly higher/lower V instead of 6s much higher/lower V. Even if the packs are in parallel the power is still going to be pulled more so from the stronger string of cells? So the discharge parallel connection makes little to no difference? that is a good simulation, assuming when plugging the packs all together they are matched fairly well (obviously) there is only going to be small currents through the balance leads, imagine if cells at 3.2V were parallel to 4.2V 7 wire foam cutter anyone.

If I was to redo the pack in this bike again I would think about using this method, but at the moment I cant be bothered, plus it makes using the hyperion to charge impossible. I ~could~ bulk charge while using the hyperion to balance the cells in 2 groups but that seems like more of a pain than what I already do.

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wire foam cutter? probably not. hot wires? possible, damage to cells? probably a little.... think about it... its only 1v difference per cell - if you have a 50mohm connection thats ~16.5A that's flowing. i^2r=16.5w... and at 16A your high cell is going to empty quickly, and your low cell charge quickly, and the amp rate will taper off as this happens.

wait... its even less, because its 2 50mohm connections - one at each end, so its only about 9A that will be flowing between the cells and 9w of heat, peak, less than a 2c charge rate for a 5ah cell. none of it is something to make a habit of, but a once off is unlikely to cause any notable damage, even to your wires or connectors.

doing this with more than 1 series of cell out of balance with its 'partner' would cause more issues/higher power flow, particularly if connecting the lower R discharge leads+connectors, but again, its probably not quite as bad as you'd imagine. certainly less than i thought it'd be!!

otherwise yea, 1 dead cell is not going to take out its 'partner', but if you're paralleling them to charge anyway then your more likely to cause a fire at that point, trying to dump amps from your ~3.6+v cell into your ~1v dead cell. better off to keep an eye on internal resistance and ending voltage of each paralleled cell group to spot any runts. you could put a low value resistor (<.5 ohms) if your're really worried about this, but that could cause weird issues with balancing and IR calculations. A low voltage light globe might be better. if it lights up, you know you have an issue, but with balance currents its resistance should stay low enough not to have a significant effect (no guarantees though, im just guesstimating here!)

[youtube]4GfPT5eq0Ys[/youtube]

still shit, I completely appreciate the effort that goes into making videos and the pro's make it look so easy, ah well.

I loosened a few or maybe all of the spokes doing what I did today.....do people loctite their nipples :wink: or just put up with tightening them every so often? I have been doing them up tight enough that when plucked they make a nice note, then match every spoke to that and the wheel comes out pretty true. Im a little hesitant to do them up any tighter for fear of cracking the rim.....#12 spokes .

enjoy!

rodgah said:

....do people loctite their nipples :wink: or just put up with tightening them every so often? I have been doing them up tight enough that when plucked they make a nice note, then match every spoke to that and the wheel comes out pretty true. Im a little hesitant to do them up any tighter for fear of cracking the rim.....#12 spokes .

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nice video! i have so much footage, but still never post any videos as i hate editing it. i just don't have a feeling for video editing.
regarding spokes: i laced both wheels. double cross front wheel, radial laced rear wheel (20"). i did around 1000km and checked tension frequently but didn't have to tight a single nipple since. rims are true still. i did tighten the front wheel's spokes a bit because i thought that those where a bit soft. all of them half a turn. but i could have gone w/o that as well. i'm afraid they have a too high tension from the very beginning - and hope that the rims will not collapse *ggg*

edit: seeing you pulling wheelies with ease i will stop working now, drive home, and take my 4x 6s lipo packs, put them in series and remove the heavy 24s lifepo pack from my handle bar box. i want my bike to do wheelies as well. you have a 3525 and 26" wheels and i have 3540 and 20" wheels. with the weight in front removed and 100v and 40a this must work

Nice video man! Now you only need to "kill your baby" and only keep the best moments, and do audio synk, puting the drops in the music at the same times as the stair drops! liked the use of some still shots with software pans, adds some good dynamics. Nice wheelies BTW

izeman said:

26" wheels

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24" with 3.0 tyres, and dont quote me but I think my middle speed is programmed as 100% and probably 50a. All things considered I dont see why it wouldnt wheelie...

bzhwindtalker said:

Nice video man! Now you only need to "kill your baby" and only keep the best moments, and do audio synk, puting the drops in the music at the same times as the stair drops! liked the use of some still shots with software pans, adds some good dynamics. Nice wheelies BTW

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your onto it, I think I just lack the quality and quantity of decent footage to do something good with. Audio syncing and more complex renders will have to wait till I get a new computer as its painfully slow to get right. You noticed the software crop and pan??.....I shot in 2.7k and then zoomed in to give ~1080p. It actually turned out pretty good for my crappy pc which makes me wonder how many real editors use it instead of panning camera mounts. And on the topic of mounts I think Ill have to buy a tripod of some description to get closer...