Thunder Sky + Fechter/Goodrum BMS + PakTrakr + Zaurus = ???

Cool strobe effect.
If you're seeing 82v without the BMS, then that would be close to the peak voltage I'd guess. That should be fine.

The charger behavior is a bit strange, and I could imagine that the off pulse might reset the auto cutoff if all the cells ever come up. My cheap chinese charger does a similar thing, but at a higher frequency. The auto cutoff works OK on mine as the charger maintains enough current to keep the control circuit alive.

You've discovered one useful feature of the BMS circuit by locating which cell is out of whack.
If that cell is damaged, it may never behave properly. Seems like a cell could easily go over voltage and fry without a BMS.
 
fechter said:
Cool strobe effect.
Click to expand...

Yes - easy to spot! It looks the same in person, BTW. :)

fechter said:
You've discovered one useful feature of the BMS circuit by locating which cell is out of whack.
If that cell is damaged, it may never behave properly. Seems like a cell could easily go over voltage and fry without a BMS.
Click to expand...

I'm happy with the way the BMS works here. Here's another twist...

I got the first and second BMS latch tonight - but couldn't finish the charge THRU the BMS. The TS charger wouldn't run thru the BMS at this point - too many shunts on for it to be comfortable - so I cheated. I left the BMS plugged-in, with the jumper on the charge input to keep the control circuit on. I connected the TS charger to the pack positive and negative - around the BMS, not thru it. That allowed the BMS's shunts to keep the cells down, allowed monitoring the charge with the shunt LEDs, and when the last cell got 'there' the BMS latched green.

video clip of the BMS thru the last pulse is here: http://www.rechargeablelithiumpower.com/media/Latch_on_Pulse.wmv 65MB, 5 minutes

It took a bit of help with a 2A charger to finish-off the pack. Here's the result:

View attachment Assorted_Charges640.jpg

No - charging around the BMS doesn't stop the charge. Since the TS charger is 'comfortable' with its 2A/2 min pulses, and the shunts keep the cells from overcharge, what would it hurt if the charger runs another 8 hours in this condition? That's the datalogging that's going on tonight.
 
There should be some way to fool the charger and run through the bms. One idea might be to place a resistor across the FET (drain to source) so the load never drops. If you use the right resistor value, the current through it after the auto shutoff trips will be lower than what the shunts take.

Another possibility would be to put a resistor across the charger output to keep a load on it. This would allow the BMS to completely shut off at end of charge. You'd want to use the highest value that works. This would probably need to be a BIG resistor that gets pretty hot.

Yet another possibility would be to interface the BMS to the charger's PWM circuit. This would be complicated, but would probably be the most efficient. Hacking the charger to prevent the pulsing might be an option too.
 
The charger merrily pulsed along for more than 12 hours last night connected to the pack. The shunts kept everything below 4V. If nothing else, this gives me a 'plug in and forget' option that I can walk away from and trust that it's working and that the battery is safe - and I like that a lot.

Thanks Fechter - excellent suggestions. I'll open the charger for a look, but need to do some riding first.
 
What a difference a charge makes!

Here are voltage drop images for the pack - first significantly unbalanced, then nearly a full charge.

View attachment first_ride.jpg

View attachment first_charged_ride.jpg

Pre-ride resting voltages for the unbalanced pack ranged from 3.29 to 3.38V, while the nearly-balanced pack ranged from 3.45 to 3.73V. One thing about these cells compared to A123 and PSI cells is they don't seem to keep their surface charge as readily - the downward curve in the 2nd chart before the ride was from the pack sitting there with only the 4-9mA load of the PakTrakr remotes on them.

The cells that dropped the lowest under a 100A (1.6C) load were the same in each - cells 4 and 18.

This is a new pack - not even one complete cycle on them yet. I think I'll need to keep an eye on 4 and 18 as the pack breaks-in.
 
Looks good, Andy. :)

BTW, the ability to hold a surface charge is more a function of the brand, and/or how the cells are made, than the quality or health of the cells. PSI cells, which are very good (10C...), can't hold a surface charge at all, even brand new. a123s, if healthy, can hold a surface charge over 3.6V almost indefinitely. Not sure about any other types, as these are all I have/use.

-- Gary
 
No, I don't have the BMS in the bike permanently. No, I don't yet have a way to interface the LVC signal from the BMS to this bike. But I will soon...

Rode a hard 42 miles on the bike today. This was the first full discharge on the pack; took it down until the 52.5V controller LVC tripped. Felt the 4-5 pulses per second from the controller - I don't need to do that again. 1/4 mile from home and wishing I had pedals. No, dammit, I'm NOT going to push it down the road - it's going in under its own power! :twisted:

Here are the pictures of the pack voltages for the last 10 miles of the ride:

Lowest cell in this set of 5 was 2.45V
View attachment RemC.jpg

Lowest cell in this set of 8 was 2.41V
View attachment 2

Lowest cell in this set of 8 was 1.68V; the next two were 2.26V
View attachment RemA.jpg

Here's a look at all 21 cells and the discharge current. Max draw was 107A.
View attachment 21cells_current.jpg

Controller LVC is 'pack average' and is not good enough to keep the cells from being damaged. 52.5V for 21 cells is 2.5V. While a nice number, it's only useful if the pack is perfectly balanced near the end of the discharge.

It's time for the LVC...
 
Cool graphs 8)

The low one on remote A looks like it was hating life toward the end there.

It will be interesting to see if that's the same cell that takes longer to balance or if it lights up first when charging.
 
can you tell which cell dropped down to 1.68V? is that #4 or 18? what voltage did it return to with the load off? that is the biggest battery i have seen, 4.5kWh.

your power consumption is in the range of the old honda insight which was about 110wH/mile. impressive setup, really nice.

can you determine internal resistance on individual cells with a load through an ammeter or watts up? that would be interesting to know too. especially if you have one or two cells with lower capacity.
 
Nope - it was not a happy cell! The factory is replacing damaged cells thru a 2 year warranty. I wonder how much damage a consistent diet of overcharging and undercharging will do... :(

Yes - the lowest cell was number 18 in the pack. The next two are 17 and 19. It took just over 2 1/2 minutes for the cell to recover to 2.5V.

This was the first full discharge on the pack so the 'cell health analysis' is just beginning. Cell 18 has already jumped onto the 'radar screen' though...

Power consumption was the name of yesterday's ride - jackrabbit starts, wide-open throttle, little to no coasting, heavy braking, etc. Triggered the motor overheat for the first time... I'm still trying to get the feel for the bike and 'exercise' some electrons to get the pack broken in.

Next comes the learning to get toward max range - without having to let it cool or reset the circuit breaker. :) Max range at 25mph should be around 85 miles.

Yes - internal resistance measurement is an option, but I haven't tested the cells yet. I could have cycled the pack a few times, checked capacity on the CBA, and used the LaMantia to check initial cell resistance, but it took enough good riding weather to get the wiring installed and the BMS built. :wink: More testing will happen once the pack's broken in.

The bike is a Chinese-made 5000W scooter, the XM-5000Li.

I need to do some testing on the brake inhibit signals - I want to know if the brake switches activate the brake lights directly, or if the controller handles that. I might have to use a small relay for the LVC function.
 
Love the scooter. :) Just curious, though, why 21 cells? We typically use 16 cells for "48V" systems, 20 for "60V" systems and 24 for "72V" setups, mainly because the CC/CV crossover points are roughly the same for 48V/60V/72V SLA setups.

-- Gary
 
Hello AndyH - what motor and controller were you using? I might have missed it.

Yep - I have had a loose switch cause me to pedal a 5304 and two 36V 10-12 ah packs - no fun at all :x

DK
 
GGoodrum said:
Love the scooter. :) Just curious, though, why 21 cells? We typically use 16 cells for "48V" systems, 20 for "60V" systems and 24 for "72V" setups, mainly because the CC/CV crossover points are roughly the same for 48V/60V/72V SLA setups.

-- Gary
Click to expand...

I don't know Gary. Could be a space challenge - the bike has a 2-layer pack and all the 'easy' space has been filled. I could pull the under-seat storage bin and strap in another 3-pack of cells. Since I bought rather than built, I don't yet have the details or limits of the controller and motor, so I'll leave it as-is until I know more. The 24S6P PSI upgrade is still a few miles off, but might need to happen at some point. :wink:
 
Deepkimchi said:
what motor and controller were you using?
Click to expand...

So far we do not have any significant info on the motor or the controller
used in the X-Treme (API) XM-5000Li "motorcycle" (with scooter body style).

According to the schematic circuit in the manual (could be incorrect):
There is a 12-volt control line that is normally open (presumably low) that
will be connected to +12v by the brake switches, the kick stand switch, or
the motor over-temperature sensor switch. The controller uses this same
+12v signal to activate its motor-cutoff function. This also turns on the
"Diagnostics 1" LED in the Instriment Cluster.
NOTE: The connection must be able to supply enough current to turn on the
three bright brake lamps that appear to be directly connected to this same circuit.

The motor description is just "High efficiency 5000W brushless Hub Motor".
There is an "engine number" stamped in the rim of the motor cover.
Mine is 8 characters, "08N023nn", where the last two "nn" are also digits.

The controller is referred to one place in the manual as "Digital Controller".

From the same schematic, the Throttle appears to have a 3-wire connection,
presumably "ground", +XX volts, and the variable "control" voltage back
to the controller.
 
fechter said:
You might find some additional information about the XM-5000 on the other forum:
http://visforvoltage.org/
Click to expand...

It looks like there are only a handfull of these in the wild so far. Garygid and I appear to have gotten the first ones out. There's another in East TN, and a couple in service with the police in Reno and possibly Vegas.

The BMS is doing an excellent job keeping the cells from being overcharged. The TS charger's 1.6A to 2A pulses take awhile to bring the lower cells up, but they do get there. I'm to the point of being completely comfortable to ride, plug in, and leave the garage until the next day.

The next step will be to make a set of leads for the dual 50V 5A power supply. That should allow a fairly quick charge to 80% with the 15A TS charger, then finish up thru the BMS at 5A for finish and balancing.

This paper on charging: Building Battery Webinar made an interesting point on slides 33-35 - that cells charged to the same level may not reach LVC at the same time. Interesting! 'Balancing' doesn't have to mean 'just at the top'! Hmmm... I have one cell that's a bit of an under-achiever, and two others that are slightly below the pack. What if I adjust the shunt voltage a bit to add some extra charge to the low cell? Can I 'trial and error' my way to a better balanced pack as it reaches cut-off?
 
Andy, what I've found with some of my a123-based packs that have a mix of healthy and "under achiever"/stressed cells, is that as long as you are doing cell-level LVC protection, and you let each cell get a "full" charge each time, for whatever full means for that cell, and you let it get full at its own pace, how well balanced the cells are is irrelevant. This is really what the BMS is designed to do, and nothing more.

-- gary
 
pgt400 said:
Andy, during a full discharge do you know how many AH you get from the 60ah cells? With all tht data you have I'm sure you do, maybe I missed it.
Click to expand...

Not yet - I've only got one full discharge so far - and a bunch of short trips. I'll run some CBA cycles on a couple of single cells, and want to get internal resistance as well. I'll feel more comfortable about full discharges once I get cell-level LVC.
 
GGoodrum said:
Andy, what I've found with some of my a123-based packs that have a mix of healthy and "under achiever"/stressed cells, is that as long as you are doing cell-level LVC protection, and you let each cell get a "full" charge each time, for whatever full means for that cell, and you let it get full at its own pace, how well balanced the cells are is irrelevant. This is really what the BMS is designed to do, and nothing more.

-- gary
Click to expand...

Hi Gary,

Absolutely - I'm not suggesting the BMS should do anything it's not designed to do. I just noticed, though, that the 'stock' BMS shunts at a range of voltages - 3.65 to 3.72V - across the pack. What I'm going to do is look at the cell that sags the deepest 'on the road' and make sure it's closer to 3.72V rather than 3.65. It won't hurt anything, and might help.

Andy
 
Hi Ross,

The blocks are the AT-CFB8 from Wiring Products Ltd. in Sparks NV. They're solid/substantial-feeling boxes. They use 1/4 inch spade connectors on the bottom, and there's plenty of room for standard connectors.

I wanted to use insulated connections and needed to make some room for them. A slight twist on the lug and the insulated connectors worked great.

http://www.wiringproducts.com/contents/en-us/d136.html (Third item down the page.)

View attachment fuse_block_twist.jpg

View attachment fuse_blocks.jpg
 
GGoodrum said:
Love the scooter. :) Just curious, though, why 21 cells? We typically use 16 cells for "48V" systems, 20 for "60V" systems and 24 for "72V" setups, mainly because the CC/CV crossover points are roughly the same for 48V/60V/72V SLA setups.

-- Gary
Click to expand...

Gary,

Max voltage for the controller is reported to be 80V. I'm getting some motor overheat issues when I push the bike hard. I suspect (but still cannot confirm) that it's a 20S/"60V" system that has an extra cell so it will hit 60mph.

Andy
 
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