Tidal Force S-750 Build by mikeross

Nice build mikeross! The Tidal Force is so sweet. Great work on the battery by the way.

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Crimson Head: Thanks for the encouragement - right now it's a nice looking bike that won't go anywhere! :? The few miles I got on it before these battery problems cropped up were very nice, though.... I'm trying to not get frustrated - looking over the ES forum I can see that a lot of guys have had problems with new lithium battery packs - especially the Headway packs - I don't think anything major is wrong and eventually the pack will work great.....

I recently fixed my Headway pack, and I just _happened_ to buy the same replacement Signalab BMS from batteryspace.com.

It was after installing the new BMS and still getting crap mileage from the pack that I opened it a second time and bought a multimeter...

For you, does it happen to be cell #7 in series (it was at 2.4V for me while others were at 3.4V)? After I read the diagram, it occurred to me that the wiring on that cell was a bit out of order, though I can't recall exactly how anymore.

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Drewdiller: I'm not sure how to count the cells, but the low one is the cell on the top left of the stack of five cells behind the BMS - pretty easy to get at. I finally got the pack up to 40.6V after about a week (exaggeration) of charging, but when the charger is disconnected it only puts a flash on the CA then goes dead again - I'm thinking now another cell is out of whack and this one is virtually impossible to reach without tearing the whole pack apart. This is the one the black balancing wire (number 1?) goes to. I just got an individual cell charger off Ebay and am going to charge up this questionable cell via the balance wire before actually ripping the pack apart. Haven't yet had time to put the meter on the pack to verify, but ya, I'd like to get out and ride this bike some time soon. Fortunately for me my old Giant LaFree SLA is still chugging along, so at least I've got something to ride to work every day....

Oh yes, did you have kind of ho-hum performance before you got your pack sorted out? I was under-impressed with the performance so far. It was OK, but on one stretch I had a hard time keeping up with my wife who was riding the LaFree

If you remember anything more about the pack wiring needing a mod, let me know!

Mike

Ok, yeah, cell #1 is pretty hard to get at. It indeed has the black wire leading to the B- pad on the BMS.

frodus initially suggested that I check all cells for both (1) grossly different voltages and (2) voltage differences under load once step 1 was satisfied.

I basically realized I was in situation 1, and once I brought it up to bar with the others, there was no load voltage difference compared to the others. So that told me I had a cell that came uncharged, as opposed to situation 2 where a weak cell would need to be replaced no matter what (whew!).

Hope you don't have a weak cell! I wouldn't know what to do with those specially welded nickel strips that put the pack in series...

To charge the one cell, well, my single cell charger came with alligator clips, which weren't very useful, so I just used electrical tape to hold them in place.

To do that, I _did_ have to take the cells out of the sticky part of the battery box so I didn't make contact with the other six cell cluster. You're going to have to do the same, it sounds like. Don't worry: you'll break some of the foam, and it'll be slightly messy, but when you put it back together, it'll still stick just enough to be workable. It's a pretty awkward assembly, I was afraid of damaging the wires. YMMV, I had a different case than you, and my new BMS was slightly too large for it, I had to Dremel some slots in the case to make it fit.

I can't really make a fair claim to performance at the time when it was still being a bitch, because I was riding on studded tires in the snow at the time. ANY motor in that stuff makes you feel like you're going way too fast, but the same speed on pavement would feel slow.

drewdiller: Darn it, I was sure hoping to avoid taking that pack totally apart! Maybe I still can if that #1 cell will charge through the BMS wire with the single cell charger. I was thinking of hooking the positive charger wire to the BMS wire, then the negative charger wire directly to the pack negative on the BMS - that seems like it would work. I'm still hopeful - there has not been any trauma to this pack, so with a little luck maybe I'll fall into category #1 like you did. I don't even want to think about having to replace that one cell...

Thank you for the advice/info on this pack.

Mike

Over the weekend, I tested and retested my battery pack - all cells were really close - right at 3.3V each - no low cells. However, whenever I would plug in the controller the thing would go dead - would not even light up the CA. I measured 1.2V across the BMS whenever the controller was plugged in. Also, if the charger was plugged in, everything lit up just fine. This caused me to think the BMS was cutting out even though the pack was balanced. Recalling a number of posts by forum gurus regarding the hassle and waste of BMS's, I decided to remove my new Signalab BMS and see what happened. Woot! Fires right up. Went for a nice ride on Sunday, which helped me feel better about things. Also, the BMS balance wire plug has been routed through the back of the battery case. For now, I am the BMS!

Still to go (Phase I) - rear fender, permanent mount for the motor controller, rear view mirror. I'll post some pics soon.

OK, one more thought. Previously, I have not ridden ebikes with hub motors except on rare occasions. My daily ride is a "pedelec" with the motor near the crank. There are two big differences between these two systems - one: you always have to hold a throttle position on the hub motor - very rarely necessary on the pedelec. Two: gears matter only to the rider on the hub motor - it is more or less direct drive/one speed; on the pedelec gears do matter - more like a car or motorcycle, you have to be in the right gear.

I'm still running without a BMS myself. I killed one cell, though. It was either a quality control problem with the cell or I pushed the bike too far. If you keep it within 50 %, use only about 1C discharge rate, you don't really need a BMS. You do have to be pretty deligent on the charging, though and make sure the cells are increasing in voltage if you bulk charge them but this can be solved by just buying all individual chargers or getting a unit that charges all the cells individually. I'm running at a 2C discharge rate, though so I'm basically pushing the pack pretty hard. I think if I had to do it over again, I would have gotten a controller that only was 20 amps instead of the 35 amp that I have.

Hi, Morph: Thanks for the info. I don't tend to run my bike very hard, just around-town riding, mostly flat terrain, pretty short trips. One interesting thing, I have a 20 amp controller, and was thinking it is a bit on the wimpy side - so was thinking of getting a 35 amp controller! Kind of the opposite of your experience.... I believe there are some programmable controllers out there - maybe that's a good way to go - then find a happy medium for your setup and riding style.

One thing has really got me stumped. No matter how long I leave this pack on the charger, it will not charge past about 3.3V/cell - it really hangs right at 39.6 volts for the entire pack. That's even using a single cell charger and charging through the balance wires. So, with either the Ping 5 amp charger (left on the pack for days) or the single cell charger, the highest its ever gotten is about 40 volts. The volt limits for this 12s Headway pack are 2.7v minimum and 3.65v maximum per cell, or an operating range of 32.4v to 43.8v, so say about 33v - 43v to be safe (and also measuring each cell to make sure they are all pretty close). Maybe it just needs a few more cycles on it, so my plan is to run out about 5-6 ah (or 50-60%), re-charge, then measure each cell individually. This pack is only on its second or third cycle, and I've read a lot of threads here on ES where guys had trouble early on with their packs, then they settled down after 10 cycles or so. Although I had two cells that were low compared to the other 10, they now all seem to stay pretty close to each other, just not at a very high voltage.

OK, finally got some photos. I'm calling this the *finished* version, although the to-do list is still pretty long...


Left side view. Note, the axiom bag is empty, battery is below in rack. Controller mounted in front of battery pack.


Right side view. Pretty cool chain guard.



Stuffed all the extra cables into that little seat bag. Looks cluttered from close up.

Mike

I guess *finished* is a relative term. This headway battery pack is driving me nuts. It conked out on me again and sure enough, that same weak cell was down to 1.9v - every other cell was at 3.2v to 3.4v. I put the single cell charger on the weak cell and in 15 minutes it was back up to about 3.2-3.4v. Then I put my Ping 5 amp charger on the whole pack and left it overnight. Voltage this morning = 39.6v. Not good. I don't understand what is keeping the pack from charging up - it doesn't get hot, or even warm while charging. There is no BMS, just straight from charger to battery pack. Output voltage from the Ping charger is 43.x volts (I forget exactly, but just what is marked on the charger as the correct voltage). Hmmm...... Tonight I'm going to put the single cell charger on one of the normal cells and leave it until it gets to 3.65v - even if it takes a week!

Mike

I'm also using the same Headway battery and also found one cell very low after having the battery sit unused since purchase; was your low cell the 6th cell - counting up from 0 volts?

Hi, SunCoaster: I *think* it is the same cell. I also think there are two designs for this pack - one design with two stacks of 6 cells and another design (the one I have) with two stacks of 5 cells and the last two cells crosswise in front. The one that is crapped out on me is the top, left cell on the 5-stack in the middle of the pack (looking at the open pack from the BMS end). To me, it would be cell #7, but that's starting counting at one.

The symptoms I'm experiencing are these: First - the pack came pretty well charged and I rode it around for maybe 4-5 miles with no problem. Then the BMS (the Ping replacement - never did use the original BMS) cut the pack off. This cell was way low (below the 2.7v limit), the rest were all at something like 3.2v. Put the pack on the charger for a LONG time - days. Pack balanced, but all cells are only at something like 3.4v - not nearly fully charged. Go out for a ride, get about 2 miles down the road, the BMS shuts the pack off again. Same cell is low (but not below 2.7v this time). Charge like mad, all cells remain at about 3.4v. Remove BMS, wire everything together straight through (with bigger wire, too). Go for a ride, get about 2 miles down the road, pack starts to fail again, so I head home (pedaling mostly). The same weak cell is at 1.9v, the rest are at about 3.2v to 3.3v.

I can put a single cell charger on the weak cell and it will charge up to 3.2-3.4v in maybe 15 minutes. For some reason, I can not get any of the cells to charge beyond about 3.42v. This weekend I'm going to leave my single cell charger on longer and see if I can get them all up to > 3.5v. I'm not giving up on that one weak cell yet, but my current thought is that it is somehow screwing up the whole pack.

I have not yet contacted EVComponents - they may have an easy answer. I keep thinking this is just new-pack problems that will iron out, but that one cell may need to be replaced (whew, that won't be easy!).

mikeross said:

I have not yet contacted EVComponents - they may have an easy answer.

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Sorry Mike, but I don't think there's an EVComponents anymore. Most of the employees left last month and they are closing down. Maybe the ES member "Frodus" could give you some help troubleshooting. He's an ex-employee of EVComponents and is quite active here.

http://endless-sphere.com/forums/viewtopic.php?f=1&t=18005&p=262456#p262456

Yeah, frodus was helpful to me.

if a cell is going to 1.9V, its a dud.... you should replace it immediately.

Remember guys "Your battery pack is only as strong as its weakest cell"....

Basically, it will charge/discharge faster than the others because of a difference of IR. It may have a higher IR, which would cause it to lose energy due to heat dissipation, i.e. it will discharge quicker at the same overall current draw as the rest of the cells. The range for these cells is 2V (which I don't recommend) and 3.65V. 1.9V is too low.

Also, just because it doesn't hit 3.65V doesn't mean its not charging. A cell stops charging when its current draw goes to zero. You can fully charge a cell at 3.4V the same as 3.65, but it might take longer. The way to tell if a cell is charge is to see if the current being drawn from the charger is zero (this is for a single cell only, not the entire pack).

Bike looks nice Mike very clean on the install. A bit heavy in the back end I would bet. My first was that way too but got used to it and had no problems other than feeling a bit of frame twist around sharper corners at higher speeds. You did a great job hope you get the battery thing werqed out.

Sorry Mike, but I don't think there's an EVComponents anymore.

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El-Steak: That is unwelcome news. But it does explain why I haven't received a reply to my inquiry regarding the battery pack.

if a cell is going to 1.9V, its a dud.... you should replace it immediately.

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frodus: Two things about this pack I don't understand. First, why did it not charge beyond 39.6v total for the whole pack? The charger outputs 43.something volts. Second, the cell that is currently fried is the number 2 cell. Up to this point, it was always the number 7 cell that was low. Do you think it's possible they are both bad?

Also, does anyone have an idea where or how I might replace those two cells? This pack is welded together, so I'm not sure how in the heck to even start.

Final note - Justin at ebikes.ca sent me directions to convert my controller to 24v. I had a 24v pack for my other bike, but starting today it's on this one.

Thanks you guys for the helpful information - this part of building an ebike kind of sucks.

Mike

mikeross said:

if a cell is going to 1.9V, its a dud.... you should replace it immediately.

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frodus: Two things about this pack I don't understand. First, why did it not charge beyond 39.6v total for the whole pack? The charger outputs 43.something volts. Second, the cell that is currently fried is the number 2 cell. Up to this point, it was always the number 7 cell that was low. Do you think it's possible they are both bad?

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As far as why it didn't charge beyond 39.6V, its likely because the BMS told the charger to cut out because ONE of the cells reaches HVC and turns off the charger input. The charger may SAY that it puts out 43.something but what do you actually measure on its output while charging?

Second, the cell that is 1.9V is fried. If number 7 cell was really low too, then its likely both are bad.

Do this. Fully charge the pack, test the cell voltages. Next let it sit for a day or two, measure the voltage on each cell. Then take it out for a spin until you reach LVC, and quickly measure the cell voltages.

If one seems high on charge, and low on discharge, its likely got a problem. you shouldn't be going below 2.5-2.7V with your setup.

Then take it out for a spin until you reach LVC, and quickly measure the cell voltages.

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frodus: No can do. The pack is totally dead at this point - it won't even light up the CA. Cell number 2 does not read anything - my multi-meter just puts out random numbers like it does when you first turn it on (i.e. no voltage measured - or is that infinite voltage measured...). When I get home tonight I'll measure the individual cell voltages again - it has been sitting for about a week since its last charge. I'm pretty sure that there is one totally dead cell and one weak cell at this point.

I'll also test the charger voltage when it's under load - it has only been measured while just sitting there plugged in. I've never seen a single cell on this pack go over about 3.4v max - either with the single cell charger or with the 5a Ping charger.

Thanks for your help!!!

Mike

Bike looks nice Mike very clean on the install. A bit heavy in the back end I would bet. My first was that way too but got used to it and had no problems other than feeling a bit of frame twist around sharper corners at higher speeds. You did a great job hope you get the battery thing werqed out.

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Hey, thanks biohazardman. Overall, I am happy with the bike. Yes, it is a bit heavy in the rear end. It isn't as bad as I thought, but you can feel it if you try zipping around the corners. The battery is not all that heavy - especially compared to lead acid batteries. I have seen some guys put the battery over the front forks, but I really prefer the way this battery sits inside the rear rack. Now to get the dang thing to work... :?

Mike

hey, no problem....

If you're reading a bunch of random numbers, the cell is probably open.... and not giving any voltage. It'l need replacing. The other low cell should be replaced as well. Its a PITA, but you can cut out the welded cell, and get another cell and solder it, but you need to be quick and have a hot iron. Get them direct from headway or Victoria.

Testing a charger under no load tells you nothing because a charger when connected to a battery tries to PULL the voltage of the cell up to that 43.something Volts, the further it is away, the more current it draws, but the charger voltage should read the same as the pack voltage. The pack PULLS the the voltage of the charger down, so the only time you'll see full volts on the charger, is when the battery is fully charged... and it sounds like one cell or two is keeping it from charging all the way.

I'm surprised that your cells don't go over 3.4V.... even with a single cell charger... I wonder if your multimeter is shot... those single cells usually go up to 3.6-3.7V.

The 43.something Volt charger you have looks at the total voltage in series. You could get 90% of your cells at 3.4V, but the last ones may be way overcharged... but the charger doesn't know this until the BMS cuts out because of HVC. If you keep hitting HVC, then shunting, then enabling the charger, hitting HVC, then shunting, you'll eventually just stop because those 2-3 cells keep hitting LVC, and the rest will NEVER charge.

Does your multimeter have "autoranging" turned on when testing cells? On my DVM (radio shack junk) I set it to the 4v limit and get the best resolution.

If you have 2 mutimeters... you could test the charger's voltage output while also checking the current, that would tell you if indeed anything is flowing from the charger to the pack.

I've seen these EvComponents batteries do somthing simliar (regardless of BMS type) where they match the charger voltage, taper properly through the process (to /20 I think) and then cutout and go green but the pack drops down 2v almost as soon as the charger cuts out (within 3 minutes or so)...

I've also seen the chargers hold their 43.x volts but only to a 1A current draw which is not sufficient really to top off the LiFePo4 cells...

Either of the above could be the cause or neither... just hope it helps!

-Mike

Does your multimeter have "autoranging" turned on when testing cells?

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Bingo, Mike! I have a pretty decent Greenlee multimeter, but apparently need more instruction on how to use it. My dead cell is actually measuring right at 198 mV (i.e. not Volts). You have to wait something like 2 seconds for the multi-meter to switch ranges and settle down to give you a reading. This, coupled with trying to read through the balance wires, being totally frustrated, and I definitely did not get that cell measured right.

Last night I took the battery pack completely apart so I could measure the cells directly. Number 2 cell is definitely a goner. I'm looking around for some replacement cells now. Hopefully, the advice from frodus will work and I'll be able to solder a couple new cells into the pack.

OK, so something funny happened. I had the battery pack all apart and laying out on my work area in my garage. Took off my watch and ring. Got a screwdriver to try and pry the dead cell loose - pretty tight quarters. Seriously, it looks like I am working on a bomb. I get the screwdriver about 1/4 inch away from the cell and my wife (who is coming home from work) hits the remote for the garage door! ZZZaaappp!!!! I jumped at least a foot! Then I realized what it was, and that I hadn't been electrocuted after all.......

Yesterday I read some threads on the EV Components business meltdown. There are some guys who sent them major bucks and did not get their orders filled. They are out all their money and they got nothing. Zip. Nada. I really hope those orders will get filled for those guys, or they will get their money refunded. It made me realize I got a crappy pack with a couple bad cells, but it could have been a lot worse! Putting in my order a month later and I would have had nothing. So, for me at least, I'll be happy just trying to put this pack right.

I'll try and post some photos of the disassembled pack. The cells are Headway 38120 (as opposed to 38120S - screw terminals). At least I've learned that much.

Mike

Mike,

I was going to post I've never tested a LiFePo4 cell at 0mv or open connection, they always show somthing minimal... figured the autorange was the issue = )_

I hear ya on the lucky timing, your right it could be worse... trick will be sourcing replacement cells, maybe post up a WTB for how many you got and then be thankful for those with worse who will split out and sell cells from their mostly crud packs

-Mike

Just a quick update. Following frodus' advice, I *bravely* got out my screwdriver over the weekend and removed the two suspect cells from my battery pack. It really wasn't that hard to pry the tabs off and remove them. Cell #2 is toast - the single cell charger light won't even switch from green to red - i.e. it doesn't even detect a battery is connected. I stuck cell #7 on the single cell charger, and it charged to 3.63v in about 15 minutes or so. This is the very first cell on this pack that would charge beyond 3.4v. Thinking the bad cells were now gone from the pack, I again tried placing the single cell charger on the remaining 10 cells, one at a time. So far, I've gone through about 4 of the cells, and not a single one of them will charge beyond 3.4v - no matter how long I leave the charger on. This time I'm connecting the charger directly to the cells, not using the balancing wires at all. There is something definitely wrong with this pack still. I'm starting to wonder if it is worth spending another $100 or so to replace bad cells, or just cut my losses and go on to Plan "B".

The used 24v pack that is on the bike temporarily has given me close to 5ah so far without a problem. Sure glad there aren't any steep hills here, though.

Mike:

Just posted my build. Take a look:

http://endless-sphere.com/forums/viewtopic.php?f=6&t=19201&p=279870#p279870

I have found some Headways will peak up to 2.65 volts on the single cell charger, but then drop down to 3.4 volts (still connected to the charger) after the charger stops charging (reached the full charge state).

you mean peak at 3.65V?