How many of u run a dc circuit breaker on your ebikes?

[Guerney]

That's an awfully long video to watch. I thought it was done, and it turned out that was just the intro! I have to admit though, good sound! Maybe I should have been clearer right up front about the fact that I value my time (except when writing long-winded posts), hence the question about whether I really have to watch paint dry batteries charge. Maybe even more importantly the older I get the more I feel I can read faster than I can watch. Sorry to have made you make that video! I really appreciate the effort though.

Is there a kind soul who could watch that video and summarize it for luddites like me?

Until I get the all clear from somebody who watched this I guess I will charge outside.

Lol yes, I completely agree, it's far too long - I had to fit the visuals to the noises I had made a long time previously, but will redo the whole thing at some point in the (probably distant) future. However, there is an easy to skim thread linked above. A gizmo sets off a horn at a pre-defined temperature.

 

[Gruesome]

I must admit I clicked on that thread link, and it sounds like heaven for people who like to combine their hobbies of electronics tinkering and microcontroller programming and e-bike battery charging all into one, and like hell for those amongst us who have decided they are happier keeping these things well separated.
I do have a spare very loud 12V motorcycle compressor horn somewhere in the garage though.

 

[Guerney]

I must admit I clicked on that thread link, and it sounds like heaven for people who like to combine their hobbies of electronics tinkering and microcontroller programming and e-bike battery charging all into one, and like hell for those amongst us who have decided they are happier keeping these things well separated.
I do have a spare very loud 12V motorcycle compressor horn somewhere in the garage though.

There's no actual programming as such, just very easy to set settings - you can rig the thing up in next to no time. You'd have to buy the genuine article to interface and control with open source code, but the cheapo AliEpress ripoff copies work fine for this purpose.

 

[Diggs]

the question about whether I really have to watch paint dry batteries charge.

I hang remote interconnected wireless Smoke detectors above each charging station in the garage and basement and then again in the living areas of the house. If one detects something they all go off. I charge 52v packs in a latched metal box when charging in the basement but when vetting single cells I charge and discharge open on the bench under the smoke detector (with metal ash bucket and lid next to the bench).

 

[Guerney]

I hang remote interconnected wireless Smoke detectors above each charging station in the garage and basement and then again in the living areas of the house. If one detects something they all go off. I charge 52v packs in a latched metal box when charging in the basement but when vetting single cells I charge and discharge open on the bench under the smoke detector (with metal ash bucket and lid next to the bench).

Judging by videos of batteries bursting into flames I've seen, by the time there's (ignitable) smoke, it's too late to do anything but run. When the temperature activated siren sounds, I'll be throwing the as yet unlit battery out of a window, with the metal box I charge the battery in, using the shovel I charge my battery on. I think the GuerneyHome Ruination by Ebike Battery Fire Expulserating PreTerminator™®©℠ will buy me enough seconds to throw the damn thing safely out of my house.

 

[Diggs]

it's too late to do anything

Maybe, but I'll know it's happening within seconds. It's the compromise I'm comfortable with as I won't sit at the bench and watch 90 cells cycle one by one through the charge and discharge vetting process.

 

[Guerney]

Maybe, but I'll know it's happening within seconds. It's the compromise I'm comfortable with as I won't sit at the bench and watch 90 cells cycle one by one through the charge and discharge vetting process.

I don't watch it, I simply wait to hear the siren... which is my cue to throw the damn thing out ASAP before it burns my house down. Of course I'll pause for a moment of consideration, because batteries aren't free.

 

[Diggs]

...and please remember. Grin couldn't even force a quality cell into a thermo event as they are self-protected. These days I only buy new Panasonic cells which also gives me some peace of mind.

 

[Guerney]

...and please remember. Grin couldn't even force a quality cell into a thermo event as they are self-protected. These days I only buy new Panasonic cells which also gives me some peace of mind.

Clearly 60°C is too hot for Samsung 25R:

 

[Diggs]

That video is 8 years old. That's a long time in Lithium battery tech. Many things have changed including government specs and approvals on cells which pretty much forced the main players to up the safety game. From what I've seen, it's many of the marginal no-name cells that have caused much of the safety issues.

...and this is where I apologize for straying this thread away from dc circuit breakers.....

 

[Gruesome]

Well, before we meander back to breakers: isn't it a problem that only one cell in a pack might overheat, and if you don't have a temperature sensor right on that cell, you might not catch it until several/many cells are involved? Also, what is the probability of these events? Is it Space Shuttle level, 1% system failure rate per launch/charge, or much lower? I guess it must be much lower, otherwise cheap battery packs would all catch fire within 500 charge cycles. But is it a ten percent chance over the expected lifetime of a cheap pack (say, 1/100,000 per charge for a cheap cell, corresponding to about 1/1,000 for a pack), or much lower still?

I moved my bike maintenance stand outside - still under cover, but away from the house - since the garage gets too hot in summer, and charge there as well. One kWh is about the stored energy in a quarter pint of gasoline, so it is not that bad. Might smolder a lot longer though....

 

[Guerney]

Well, before we meander back to breakers: isn't it a problem that only one cell in a pack might overheat, and if you don't have a temperature sensor right on that cell, you might not catch it until several/many cells are involved?

The sensor is situated in the middle of the top of the battery case - I'm counting on heat rising via convection from an overheating cell or cells. I set the alarm to sound a few degrees above normal charging temperature, so hope to be alerted well before ignitable smoke appears aflame. I've also placed a smoke detector inside the metal box I charge my battery in, on the shovel I charge the battery on, next to the window I'll throw the battery out of.

Also, what is the probability of these events? Is it Space Shuttle level, 1% system failure rate per launch/charge, or much lower? I guess it must be much lower, otherwise cheap battery packs would all catch fire within 500 charge cycles. But is it a ten percent chance over the expected lifetime of a cheap pack (say, 1/100,000 per charge for a cheap cell, corresponding to about 1/1,000 for a pack), or much lower still?

I don't know what the probability is, because fire brigades in the UK don't yet have such ebike battery ignition and home ruination by conflagration events categorised in their data collection databases - rather too new for bureaucracy; more tickboxes required. But I do know most ebike batteries are charged inside the home, where they can do the most damage to life and property. I assembled this gizmo to scratch an itch, because I know for certain I'd regret having thought about setting it up, and never having done so, if something awful sparked a personal homelessness crisis all of a sudden unexpectedly, especially considering it's all so cheap. Expect the unexpected is my motto, or that could be a ninja thing. I am not a ninja, I wear too much hiviz.

The chemistry of NASA's lithium-ion battery packs is not the same as used in ebike batteries.

 

[Gruesome]

I agree that it's easy to set up if you have the ingredients already. Not sure about there being much convection inside a pack, and cell heat capacity being relatively high (800 J/kg/K, I've read) the cell zombie catastrophe (one cell biting all its neigbors) might be well on its way before a temperature sensor catches it. I don't know. Small pressure sensors are also pretty cheap, e.g. Bosch BME280 and similar, for some there exist ready-made Adafruit plugin boards. That way you could catch the venting of the first runaway cell.
Can you charge on a window sill?

You misunderstood my space shuttle comment; nothing to do with battery packs in space. The overall system failure rate per launch was projected to be 1%, and that's what it turned out to be. Something to be aware of before you accept that free ticket for a quick hop to space....

 

[Guerney]

Can you charge on a window sill?

At the moment, I charge directly underneath with the battery inside a metal box on a shovel. I can chuck it out within seconds of hearing the siren.

I agree that it's easy to set up if you have the ingredients already. Not sure about there being much convection inside a pack, and cell heat capacity being relatively high (800 J/kg/K, I've read) the cell zombie catastrophe (one cell biting all its neigbors) might be well on its way before a temperature sensor catches it. I don't know.

I don't know either, but contrary to my expectations, the temperature rise displayed while charging changes fast - I had tried using the thermocouple on a Neoteck DMM previously, and it didn't detect any change at all, so didn't hold out much hope. Happily the temperature detection function of the STC-1000 is much more sensitive. I guess you'll have to try it yourself. Like I said, it's cheap and easy to set up. I do think it'll give me tens of seconds of advance warning. If not, the smoke alarm will activate quickly in such a small space, and it'll be rapidly thrown out of the window.

 

[Gruesome]

Cool. Somewhere I still have my brewing and lagering temperature control setup, using cheap thermostats with relay output (to control the primary side of a good size Peltier power supply). That should be enough to switch a charging supply.





















You also implicitly answered my question about the DC breaker...: since I already have it, why not wire it in?
After all things can go wrong, and the breaker should both protect the battery and provide a quick manual way to electrically disconnect it should things go haywire.

 

[99t4]

Would it make sense to put one of these DC breakers in line with the battery, near the battery, to protect against shorts?

All my batteries have fuses. Maybe yours does too? How would this be better than a fuse? What are you thinking might short circuit?

 

[Gruesome]

This would not replace any fuses or other protections already in place. I don't know what's in my battery pack(s), and I'm not intending to open them willy-nilly. The breaker would protect against any shorts downstream of the breaker. So would a fuse.
The same breaker is pretty reliable (as an on/off switch, haven't tested the current limiting function) on my motorbike (12V system).

A few examples for potential short locations, just off the top of my head: after a fall, while sliding along the pavement, a short of the wires, with insulation now partially scraped off, directly against each other or against the bicycle or rear rack frame that the wires were secured to. A short where the wires enter the controller enclosure. A short on the controller circuit board, due to a loose wire or metal piece rattling around. Wires coming loose and getting mangled between chain and chainring, or chain and sprocket. Ok, the last two require special talent in wire routing
I'm sure there are more possibilities, the beauty is the breaker does not need to know about them

 

[Diggs]

Just an observation. I don't run any fuses or breakers anywhere. I run two batteries in parallel (52v, 16 and 18 ah) plugged directly into each other. They both run the same BMSs (2 separate BMSs). Yes, I'm probably setting myself up for an incident but has not been an issue on the road in 6 years. I had a direct short once while working on the bench with one of the packs. It instantly melted the 12 ga. wire off the XT90 connector. Acted like a heavy fuse. I have messed with breakers and fuses (the ones I have are shown below) and they were more problems than I wanted to mess with so I gave up. (Please save your breath on warnings and condescension. You're entirely right!).

I'm not recommending anyone doing this. Just relating my experiences and what I am comfortable with.

@add - For the knowledge base: The bottom holder kept overheating at the base legs of the fuse. Cleaning, crimping, dialectic grease were all temporary fixes. The middle holder (above) had trouble with water egress and connections at the end due to vibration. The top (above) circuit breaker was a challenge to find some place to put/mount it and keeping it's lugs insulated was more of a challenge than I thought it would be. Any one of these probably could have been made to work but as I said, I got tired of messing with it (and that was about 8,500 miles ago).

 

[Gruesome]

Just an observation. I don't run any fuses or breakers anywhere. I run two batteries in parallel (52v, 16 and 18 ah) plugged directly into each other. They both run the same BMSs (2 separate BMSs). Yes, I'm probably setting myself up for an incident but has not been an issue on the road in 6 years. I had a direct short once while working on the bench with one of the packs. It instantly melted the 12 ga. wire off the XT90 connector. Acted like a heavy fuse. I have messed with breakers and fuses (the ones I have are shown below) and they were more problems than I wanted to mess with so I gave up. (Please save your breath on warnings and condescension. You're entirely right!).

I'm not recommending anyone doing this. Just relating my experiences and what I am comfortable with.

@add - For the knowledge base: The bottom holder kept overheating at the base legs of the fuse. Cleaning, crimping, dialectic grease were all temporary fixes. The middle holder (above) had trouble with water egress and connections at the end due to vibration. The top (above) circuit breaker was a challenge to find some place to put/mount it and keeping it's lugs insulated was more of a challenge than I thought it would be. Any one of these probably could have been made to work but as I said, I got tired of messing with it (and that was about 8,500 miles ago).

Thanks, that's the type of input I was hoping for. Interesting (in a bad way) that the bottom fuse holder would overheat! The connections on the middle holder seem the same as on my motorbike's breaker (the one I am intending to use for the e-bike). Maybe bicycle vibrations are worse, due to thinner tires, no suspension and lower mass? I had naively assumed that if it works on a motorbike it should work on a bicycle. Maybe that's not true.

And good point about assembly (or any time one fiddles with the setup) being the most likely occasion for a short.

 

[Diggs]

The connections on the middle holder seem the same as on my motorbike's breaker

I had it out in the open and inline without much support. I should have tinned the 12 ga. wires which is small for that fuse holder and it frayed off at one end and leaked at the other. Supported correctly with the right gage wires and restraining the wires it could be a good alternative.

 

[99t4]

Interesting (in a bad way) that the bottom fuse holder would overheat!

Has been reported more than a few times on this forum.

Using your desired circuit breaker as an everyday power switch might not hold up. Most circuit breakers are not designed for that service level usage.

 

[E-HP]

Thanks, that's the type of input I was hoping for. Interesting (in a bad way) that the bottom fuse holder would overheat!

They look beefy and robust at first glance, the the actual connectors have bottlenecks where you're pushing a lot of amps through some very narrow/thin pieces of copper. In a lot of the examples posted on ES, the fuse is intact, except for the plastic being melted from the holder heating up. The holder basically becomes the fuse.