GCinDC
100 MW
Were you able to diagnose the exact problem? I'd be very curious to know.
Glad to hear it wasn't worse!
Glad to hear it wasn't worse!
BIG LIPO EXPLOSION
- Thread starter LOWRACER
- Start date
John in CR
100 TW
neptronix said:
Been running my 1200W rated Chinese hubbies at 7500W+ for years without issue
liveforphysics
100 TW
So, let me get this all straight.
You drastically damage your cells from over-discharge, have a known battery-murdering-system on the pack which could/should have driven the first cell way out of balance in an over discharge situation, you begin charging your damaged pack at 2C and a cell vents smoke, you drop it into a trashcan of water and think the electrolysis bubbling (and destruction of the remaining cells) is further damage occuring for 3 days...
Then you make a thread called Big LiPo Explosion???
There is only 1 single BMS in the world that I would run on a pack, and it's made by Methods, and it's unfortunately $1,000usd. Every other BMS is more liability than an asset to your pack, some of them being well known battery murderers.
Never discharge below 3.5v. And if you're not racing, or doing something where you need every last possible watt-hour, don't charge over 4.125-4.15v.
You drastically damage your cells from over-discharge, have a known battery-murdering-system on the pack which could/should have driven the first cell way out of balance in an over discharge situation, you begin charging your damaged pack at 2C and a cell vents smoke, you drop it into a trashcan of water and think the electrolysis bubbling (and destruction of the remaining cells) is further damage occuring for 3 days...
Then you make a thread called Big LiPo Explosion???
There is only 1 single BMS in the world that I would run on a pack, and it's made by Methods, and it's unfortunately $1,000usd. Every other BMS is more liability than an asset to your pack, some of them being well known battery murderers.
Never discharge below 3.5v. And if you're not racing, or doing something where you need every last possible watt-hour, don't charge over 4.125-4.15v.
docnjoj
1 GW
Gentlemen! Once again I am seeing "experts" like Lowracer have an "unanticipated event" with LiPo. This scares the shit out of me! I realize Luke showed how safe this type of chemistry can be with his "extreme" films but here seems to be another example of batteries self destructing with no warning. This is the worst type of catastrophy and Lowracer could have lost his magnificent bike (not to mention his house). I charge my Pings indoors and I charge my Konions indoors and sleep well at night. If I get Lipo's they will be charged in a shed on a concrete pad. It is a annoyance to have to take them off the trike but one that seems necessary. Lowracer could have had an OSU moment if he decided to charge on the trike this time! Sheer luck that his wonderful vehicle lives! I don't like this at all!
otherDoc
otherDoc
dogman dan
1 PW
I didn't want to be the first to say it, but it seems to me at least one of the golden rules got broken.
One nice thing about charging the hard way, you do have the packs off the bike, can spot a puffy, and may even bother to see if any cells are below voltage and unsafe to use anymore.
31v, sounded low to me too.
One nice thing about charging the hard way, you do have the packs off the bike, can spot a puffy, and may even bother to see if any cells are below voltage and unsafe to use anymore.
31v, sounded low to me too.
oatnet
1 MW
Lowracer, I've been following your work with interest, and I am really glad you and your family are OK, that your House is OK, and your EV is OK. 
Sorry for the loss of your pack but now you can rebuild it with a less volatile chemistry, that requires less safety controls around charging/discharging, and be safer in the long run.
-JD
Sorry for the loss of your pack but now you can rebuild it with a less volatile chemistry, that requires less safety controls around charging/discharging, and be safer in the long run.-JD
oatnet
1 MW
dogman said:
If one's safety depends on keeping track of Golden Rules, it is precarious indeed. We all know Murphy's law, whatever can go wrong, will go wrong. Heck, I know better, but there have been a few times when I have plugged a battery in backwards and toasted stuff; basic, stupid stuff, I now better, but it happens. Rules get broken and forgotten all the time, and I'd betcha dollars to donuts that there are 6 newbies on this forum right now, reading about lipo and planning a build, who are ignorant of at least (1) of those rules. And I bet there are a handful of other golden rules we haven't thought of yet...
For example, after reading the links on the OSU Lipo Fire thread, I realized I had not thought about the danger of regen on a freshly-charged lipo pack. I never think about whether or not it is a good time to use my brakes, I just stop. Is that something lipo users think about already? It seems so complicated!
-JD
LOWRACER
100 W
GCinDC said:
The voltage of only one cell pack (3x4500mAh) slips away.
The balancer couldn't hold the voltage of 4.2Volt and the cells are blowing up more and more until
it catch fire.
Now the LiPo Pack is solding himself, the 8mm brass bolts are so hot, they cause a short circuit to the
neighborhood! Then the cells around are blowing up and the chain reaction begins!
To slack this fire isn't easy. This remembers me @Fukushima's Nuke.....
I don't wanna have a nuke in my garden and decided me to dive the lipo under water.
I know from the reaction Lithium and water, but under water isn't oxygen.
No oxygen= no combustion!
It don't cool down as I expected. It takes 3 days...
LOWRACER
100 W
dogman said:
If you are running a 37V nominal voltage system,
at 31Volts the controller turn off, that's safety system against undervoltage!
You can only restart controller if there are 33Volt.
liveforphysics
100 TW
oatnet said:
It was 18650 laptop cells in the OSU pack.
Likewise, we've still had more LiFePO4 fires, including A123, headways, ping packs, etc here than any other battery type.
If you're storing energy, it can and sometimes will go wrong.
Powerful batteries, even powerful things are not well suited for everyone.
Doctorbass
100 GW
Like other said, i'm glad it's only the pack that is damaged and caugh fire.. and not the nice garage you have and the house and everything!
On my side, i'm running lipo since 1 year now and i appreciate them.. but since i received.. i have 24h/24 the fear about lipo fire in my house or garage.. I worrie about one of these bad event that could occur.
With LiFePo4 A123 or LiMn konion cells i never felt that...
But yes Lipo have better energy desity and great chrge discharge rate and this is the only reasons why i was finally tempted to get some.
I have 600Ah out of my 15Ah 88V lipo pack and i NEVER used any BMS.
It is simple.. All 12 packs ( 24s3P) are connected in bank of 3 parallel 6s pack thru the balance connectors and the main lead.
I occasionally balance them with a single 6s hyperion balancer that alrady proven me that it can balance with in the 2mV accuracy over all the cells. I just disconnect all 6s bank from the 24s serie and put them in parallel. to balance 60Ah6s pack during couples of hours while top charging them to 4.200V to ensure that if they reach 4.200V they will all be at that voltage.. but since i cahrge the pack to 4.15V per cell the 50mV margin is another protection.
I always bulk charge them in 12s 6p ( 50.4V 30Ah) with my 1650Watts DC output meanwell beast power supply to 49.8V.
NO HVC and no bleeding balance resistor...
And i never discharge under 84V ( 3.5V per cell) by the controller limited lvc.
All the cells remain with in the 30mV difference on all the pack for around 10 cycles of 80% dod
The pack is really powerfull and max amp hour i discharge is 13Ah out of 15.
One day i left my ebike i my friend's garage and forgot the controlelr powered ON during two weeks... this slowly bleeded the cells down to 1.8V !
But since it happened with very slow rate ( around 70mA from the controller regulator ) the cells wan not really dmaged and i tested all them and just one cells was at 4.5Ah out of 5.. all the rest was stll at 5Ah.
BUt.. yes.. I still dont use a BMS on my 1.3kWh pack and i worrie a bit about that... I would install the Gary V2.6V on it .. just to accelerate the balancing process i do every 10 cycles... I installed 10 turn pot to carefuly trim the bleeding voltage to 4.150V on a ll 24 channels.. but still not installed it on the pack...
I plan also to add another 6s 15Ah for a total of 30s 15Ah for my 140km/h attempt.. My kelly accept up to 136V and 220A so i still have a little margin.
Lowracer, I think that was probably caused the cell to puff is charging at 2C the pack that had ultra low cells voltage.
The internal resistance of these cells low voltage cells at that low SOC is like 2 to 10 time higher and will dissipate alot more heat.. encouraging the cell to puff..
It is recommandd to bring the cells at a minimum voltage before cahrging at higher current.. ex.. on the LiFePO4, it's often 2.7 to 3.0V.. .I would say that with lipo it is probably at around 3.5-3.6V that we can push the rated max charging current.
EX.. I charge my pack in parallel at 36A and it's a 30Ah ( 2 x parallel 12s) so it'S around 1.25C and never get any problem.
My pack is surrounded of 1/8 thick aluminum wich keep all ths cells compressed together and force against the puffing possibility... and keep the internal resistance of the pack very low as it should.
it's like the metal can that have the cylindrical cells .. it help keeping the cells i good shape and not to puff.
As i explaned alot of time what make the celsl to catch in fire is the internal short caused by the deformation of the pouch.
So keeping the pouch compressed really help!.. at least.. it work for me. :wink:
Something strange i observed is that the pack seem to cool down faster wen it charge!.. than when just leave it alone withot any action..... just like if the cell charging chemical process would make a thermal reaction that absorb heat,,,
As long as i charge my lipo pack as i become more and more convinced about that observation.. someone can explain?
that could be a solution to cool down a pack i fire !.. i'm kidding! :lol:
Doc
On my side, i'm running lipo since 1 year now and i appreciate them.. but since i received.. i have 24h/24 the fear about lipo fire in my house or garage.. I worrie about one of these bad event that could occur.
With LiFePo4 A123 or LiMn konion cells i never felt that...
But yes Lipo have better energy desity and great chrge discharge rate and this is the only reasons why i was finally tempted to get some.
I have 600Ah out of my 15Ah 88V lipo pack and i NEVER used any BMS.
It is simple.. All 12 packs ( 24s3P) are connected in bank of 3 parallel 6s pack thru the balance connectors and the main lead.
I occasionally balance them with a single 6s hyperion balancer that alrady proven me that it can balance with in the 2mV accuracy over all the cells. I just disconnect all 6s bank from the 24s serie and put them in parallel. to balance 60Ah6s pack during couples of hours while top charging them to 4.200V to ensure that if they reach 4.200V they will all be at that voltage.. but since i cahrge the pack to 4.15V per cell the 50mV margin is another protection.
I always bulk charge them in 12s 6p ( 50.4V 30Ah) with my 1650Watts DC output meanwell beast power supply to 49.8V.
NO HVC and no bleeding balance resistor...
And i never discharge under 84V ( 3.5V per cell) by the controller limited lvc.
All the cells remain with in the 30mV difference on all the pack for around 10 cycles of 80% dod
The pack is really powerfull and max amp hour i discharge is 13Ah out of 15.
One day i left my ebike i my friend's garage and forgot the controlelr powered ON during two weeks... this slowly bleeded the cells down to 1.8V !
But since it happened with very slow rate ( around 70mA from the controller regulator ) the cells wan not really dmaged and i tested all them and just one cells was at 4.5Ah out of 5.. all the rest was stll at 5Ah.
BUt.. yes.. I still dont use a BMS on my 1.3kWh pack and i worrie a bit about that... I would install the Gary V2.6V on it .. just to accelerate the balancing process i do every 10 cycles... I installed 10 turn pot to carefuly trim the bleeding voltage to 4.150V on a ll 24 channels.. but still not installed it on the pack...
I plan also to add another 6s 15Ah for a total of 30s 15Ah for my 140km/h attempt.. My kelly accept up to 136V and 220A so i still have a little margin.
Lowracer, I think that was probably caused the cell to puff is charging at 2C the pack that had ultra low cells voltage.
The internal resistance of these cells low voltage cells at that low SOC is like 2 to 10 time higher and will dissipate alot more heat.. encouraging the cell to puff..
It is recommandd to bring the cells at a minimum voltage before cahrging at higher current.. ex.. on the LiFePO4, it's often 2.7 to 3.0V.. .I would say that with lipo it is probably at around 3.5-3.6V that we can push the rated max charging current.
EX.. I charge my pack in parallel at 36A and it's a 30Ah ( 2 x parallel 12s) so it'S around 1.25C and never get any problem.
My pack is surrounded of 1/8 thick aluminum wich keep all ths cells compressed together and force against the puffing possibility... and keep the internal resistance of the pack very low as it should.
it's like the metal can that have the cylindrical cells .. it help keeping the cells i good shape and not to puff.
As i explaned alot of time what make the celsl to catch in fire is the internal short caused by the deformation of the pouch.
So keeping the pouch compressed really help!.. at least.. it work for me. :wink:
Something strange i observed is that the pack seem to cool down faster wen it charge!.. than when just leave it alone withot any action..... just like if the cell charging chemical process would make a thermal reaction that absorb heat,,,
As long as i charge my lipo pack as i become more and more convinced about that observation.. someone can explain?
that could be a solution to cool down a pack i fire !.. i'm kidding! :lol:
Doc
theRealFury
10 kW
LOWRACER said:
Yea, but your using lipo.. lipo isnt 37v nominal, its more like 38.5 or 39v nominal, you should have an LVC with that of ~34.5v (35v minus a little sag for under load) 31v is not a safe cut off voltage for 10s lipo im afraid. at 31v you are already well over the lipo cliff and with an average of 3.1v per cell you only have a very slight cell imbalance to go until one or more of the cells drop below 3v and get damaged. I run with audiable cell level lowvoltage buzzers set to 3.5v per cell, as soon as any cell hits 3.5v anyone within 100meters of my bike knows i hit LVC. When that happens i just turn the power off and slow boat it home.
It scares me to reply on fancy shunt bms's or even just capacitor BMS's with all their PCB traces and oodles of wires, if just 1 wire snaps or come loose or just one bump causes a PCB trace to fracture then your compromised and things like this can happen.
If you ever do go lipo again i would say forget BMS's. A CA and some LV buzzers are all you need.. that and balance charging at 1c rate every cycle with a charger with temp monitor.
Glad you were OK and you are back on the road again, I have to say though...fat lot of good the BMS did? and another example why I dont use them on any of my packs, I hope others learn from this, you can add in more points of failure to a battery system by constructing a BMS around a pack that is largely untested and unproven, I never have anything connected to my packs when they are not being used.
BMS, cell monitors LVC boards are all well and good for some but they must IMHO be left off the packs when not in use, no system is foolproof though and cheap Chinese chargers can malfunction as we have already seen, I think the rules on charging and discharging and the general treat it like a can of petrol rule apply no matter what chemistry.
Store your batteries like you would a can of petrol, treat it like a can of petrol when you use it, fit a smoke alarm as you have done here, charge on a metallic bench or use a fireproof blanket, charge away from anything combustible, yada yada yada, folks must get this in to their heads before one chemistry gets dissed in favour of another one, no chemistry is 100% safe and one being on paper being less likely to go up in smoke than another makes no difference, treat any chemistry even down to lead acid batteries the same way and we need not worry, ever!
You just have to remember that you could loose your pack, currently with the price of RC Lipo thats not going to finish you financially, well for most folks anyway, and if it is a concern minimise the damage by storing and or mounting packs around the bike (dont keep all your eggs in 1 basket) Only fit a BMS if you know of a proven one and only use it if you think it is worth the cost of saving your pack remembering no BMS can stop this kind of thing happening and sometimes can cause cells to drain down and die.
I fully understand the need to use BMS systems in larger vehicles or TTXGP bikes etc but for performance ebikers I think they cause more problems, that said I dont think Lipo is for none techie newbies either as to run Lipo with no BMS you have to have a modicum of understanding to avoid the problems that we have already seen here.
BMS, cell monitors LVC boards are all well and good for some but they must IMHO be left off the packs when not in use, no system is foolproof though and cheap Chinese chargers can malfunction as we have already seen, I think the rules on charging and discharging and the general treat it like a can of petrol rule apply no matter what chemistry.
Store your batteries like you would a can of petrol, treat it like a can of petrol when you use it, fit a smoke alarm as you have done here, charge on a metallic bench or use a fireproof blanket, charge away from anything combustible, yada yada yada, folks must get this in to their heads before one chemistry gets dissed in favour of another one, no chemistry is 100% safe and one being on paper being less likely to go up in smoke than another makes no difference, treat any chemistry even down to lead acid batteries the same way and we need not worry, ever!
You just have to remember that you could loose your pack, currently with the price of RC Lipo thats not going to finish you financially, well for most folks anyway, and if it is a concern minimise the damage by storing and or mounting packs around the bike (dont keep all your eggs in 1 basket) Only fit a BMS if you know of a proven one and only use it if you think it is worth the cost of saving your pack remembering no BMS can stop this kind of thing happening and sometimes can cause cells to drain down and die.
I fully understand the need to use BMS systems in larger vehicles or TTXGP bikes etc but for performance ebikers I think they cause more problems, that said I dont think Lipo is for none techie newbies either as to run Lipo with no BMS you have to have a modicum of understanding to avoid the problems that we have already seen here.
LOWRACER
100 W
Doctorbass said:
The old LiPo is toasted, here the new one:
[youtube]5PryI-zfUwg[/youtube]
parabellum
1 MW
Sorry to her your loss Lowracer, good it only took your Lipos.
Once I back charged Nanotech Lipos (I forgot I used 1(2s) sub pack to run a ventilator for few hours, it was almost empty as I started my ride), I noticed that as I came home, i cut it out of the main pack (was only duct tape) and noticed that original shrink plastic was deforming/melting (it was very hot and puffy). I just throw it in to my freezer. Next time I will put in on the charger instead!Doctorbass said:
liveforphysics
100 TW
Charging is an endothermic process (absorbs energy in the form of heat from the outside world to function, making it cool down).
Most batteries have high enough internal resistance that charging makes a net increase in temp. Good LiPo cools when charged.
Parabellum- Your example of deep over-discharge would be a risky time to start a fast charge.
Most batteries have high enough internal resistance that charging makes a net increase in temp. Good LiPo cools when charged.
Parabellum- Your example of deep over-discharge would be a risky time to start a fast charge.
Except...if the lithium becomes freed from whatever other bonds it has during the fire, it will bond to the oxygen in the water, releasing still more energy in the process. I don't know if tha'ts possible in the case of the cells you have there.LOWRACER said:
Also, it *might* be possible for parts of the water to become dissociated into O and H by electric currents passing thru tiny amounts of the water (after it's become contaminated enough by conductive stuff from the fire/etc.), from the cells that are still intact enough to have voltage across them. I don't know if it would be enough, as I can't remember enough of my chemistry classes, and I was never that good with the math part, anyway.
IF that happened, you'd have a bit of free oxygen to then combine with hydrogen and/or other things in the still-burning parts of the cells.
Plus as the water becomes more and more contaminated with metals and salts and whatnot, it'll be more conductive, possibly eventually to where it essentially shorts across any cells (via deposits on the PCB traces or the cell casings) that were still intact, and causes *them* to burn, especially if they were already still hot from the fires near them.
Hard to know exactly what happened in there, without doing it on purpose with monitoring equipment in place.
I definitely feel for you, losing the pack, though. I can't imagine how I'd deal with such a loss, especially without any backup packs.
liveforphysics
100 TW
There is no metalic lithium in a lithium polymer battery. It's all in salts that don't react with water.
It bubbles for the same reason anything with voltage on it bubbles in water, electrolysis. Things with lots of voltage and surface area and current can bubble up a storm.
It bubbles for the same reason anything with voltage on it bubbles in water, electrolysis. Things with lots of voltage and surface area and current can bubble up a storm.
I guess I was just thinking that if the heat of the fire, combined with the energy stored within the cells, were able to break down the salts into something else while in combination with the water, it could cause an exothermic reaction while combining the lithium with the oxygen, or something similar. I should stop speculating, since it's been too long since HS chemistry, and I really can't remember the types of reactions and energy states well enough anymore.liveforphysics said:
ALso, I meant to point out to Lowracer previously that most standing water does have free oxygen in it, at least near the surface, where air has been dissolved into the water. If the water is turbulent, especially at the air/water barrier, there can be a LOT of oxygen mixed into the water.
This guide lists lipo swelling as a safety feature of sorts! Hahah
I wish cells had integrated wireless zigbee-like current,voltage,temp,and pressure sensors. One day.
http://www.micro-power.com/userfiles/file/wp_polymer_final-1274743697.pdf
"Over-discharge damage is an issue for all Li-ion cells but the resultant gassing in Lithium polymer cells is more obvious. When the cell voltage drops too low (~1.5V), reactions at the anode start to produce gas. As the voltage continues to drop under 1V, copper from the anode current collector starts to dissolve and will short out the cell. Over-discharge should be prevented by the BMU.
Overcharge is similar. Gassing occurs at the cathode as the electrolyte starts to decompose at high voltage (~4.6V). Cylindrical cells have integral pressure activated current interrupt devices (CIDs) to stop the overcharge when the gas pressure builds. Polymer cells do not have any CID. Although their swelling helps to prevent further overcharge by increasing the cell impedance, this should only be a final failsafe. An external thermal fuse is usually added for overcharge protection, in addition to the control by the charger and BMU.
An external short circuit can cause swelling due to heat and over-discharge. Cylindrical cells have an integral PTC (positive thermal coefficient), a device that expands and creates high impedance when it is heated or self-heats due to the high currents experienced during an external short circuit. Polymer cells do not have this integral PTC so an external PTC or thermal fuse can be added for shorting protection."
Note lipo has no CID or PTC safety features like cyclindral cells, but also realize these safety features don't work very well in high power apps.
I wish cells had integrated wireless zigbee-like current,voltage,temp,and pressure sensors. One day.
http://www.micro-power.com/userfiles/file/wp_polymer_final-1274743697.pdf
"Over-discharge damage is an issue for all Li-ion cells but the resultant gassing in Lithium polymer cells is more obvious. When the cell voltage drops too low (~1.5V), reactions at the anode start to produce gas. As the voltage continues to drop under 1V, copper from the anode current collector starts to dissolve and will short out the cell. Over-discharge should be prevented by the BMU.
Overcharge is similar. Gassing occurs at the cathode as the electrolyte starts to decompose at high voltage (~4.6V). Cylindrical cells have integral pressure activated current interrupt devices (CIDs) to stop the overcharge when the gas pressure builds. Polymer cells do not have any CID. Although their swelling helps to prevent further overcharge by increasing the cell impedance, this should only be a final failsafe. An external thermal fuse is usually added for overcharge protection, in addition to the control by the charger and BMU.
An external short circuit can cause swelling due to heat and over-discharge. Cylindrical cells have an integral PTC (positive thermal coefficient), a device that expands and creates high impedance when it is heated or self-heats due to the high currents experienced during an external short circuit. Polymer cells do not have this integral PTC so an external PTC or thermal fuse can be added for shorting protection."
Note lipo has no CID or PTC safety features like cyclindral cells, but also realize these safety features don't work very well in high power apps.
Doctorbass
100 GW
LOWRACER said:
Nooooh!!!!
Chris you are moving from 37V to 116V ???
Yeah Baby!!.. let's get ready to rumble!!!
WELCOME TO THE REAL WORLD OF POWERFULL EBIKE !!!
NOw i can say that the great 5404 you are lucky to have ( i would have nee dto pay it like 950$ shipped to Canada) will wake up like it deserve!!!
37V compare to 116V is nothing on a 04 winding!!!
That will give you MONSTRUOUS power Chris.. so i sugget to move to POWER gadually and go step by step and increase the controlelr current a bit each time... otherwise you might be affraid!!... or have heart attack!!.. or instanous non needed lifting on your face while accelerating
Doc
oatnet
1 MW
liveforphysics said:
Luke, you are muddying the waters again. Please point to the LifePO4 fires that were caused by an Endothermic reaction, like the lipo fires we have been seeing. That aspect of the chemistry is the incremental hazard at issue.
The OSU thread had a link to some safety document that I think was for the circuit, which referenced an EARLIER failure, where Regen on a full pack ignited it, but they were able to dump the warp core before the vehicle went up. No reference on the battery make, so not necessarily 18650 cells. :wink:
RVD
1 kW
i am definitely a newbie but i haven't even had a cell come close to having a puffy yet by being overly cautious..
1) i use a hyperion 1420i charger and set it to charge up to 85%. this results in each cell being 4.10-4.12. the variation isn't that some cells are 4.10 and some are 4.12 but that usually when i charge all cells are 4.10 or all cells are 4.11 or all cells are 4.12. there is some variance but 85% is good and comfortable for me.
2) i ride my bike to work (16 miles). i have a 14s3p pack so it has 15ah. i use around 9ah-11ah each way. when i charge at work, i simply charge at 14s with the leads. however, i charge under my desk with my legs a few inches away. scary?
3) when i get home, i do a balance charge as 12s and then 2s
4) when i charge, i only charge a 1C max. due to other limitations, i actually charge at a much slower rate. my 12s packs charges at around 9amps, 14s pack charges at 8amps, 2s pack charges at 10 amps. i ok with the charge taking time in exchange for safety.
5) i run low voltage buzzer/horn/blinker type things on each 6s3p (2 of them). i can visually see if any cells are going down.
6) the lowest i have ever run down a cell is 3.71v. the highest i have ever charged a cell is 4.12v.
7) i have anderson connectors and i have clips to hold the andersons in place so that any lipo shouldn't inadvertently fall out.
8) i have voltage monitors for every pack (9 of them). this allows me to visually see what the cell voltages are for every cell in my pack. however, i stopped using this. i just have all of my balance tabs in parallel and use a battery medic to analyze each 6s3p, 6s3p, 2s3p pack's parallel balance tab. i check before charging.
9) every night after charging, i store my lipos in a fireproof safe. every morning, i take them out of the fireproof safe to put them on my bike. all lipos are enclosed with floor tile wrapped with duct tape for protections and then put into a hard plastic container (similar to hard tupperware) for additional protection.
in my opinion, i feel like in many ways i am overly cautious. but i haven't had any issues yet or come close.
however, i am a bit wary of charging at work. i can't think of any other way to charge at work though. i simply charge under my desk and work...within about 2 hours the batteries are all charged up. i am thinking that maybe i should balance charge at work too rather than just every day at home (so balance every time instead of every other charge). however, doing that requires me to split up the cells a little bit into 12s3p and 2s3p.
i don't have a smoke alarm or fire extinguisher near my charging area. i charge at home next to my wife's car in the garage near my other bikes, etc. a fire would probably be really bad. i'll probably start charging outside in my back patio. and i'll buy a smoke detector.
and i usually charge at home unattended. i get home, charge, go upstairs...and come down again a couple of hours later to disconnect, etc.
sounds to me like most people have issues when they discharge a little too far. stay above 3.5 should be fine. stay above 3.7 should be more than fine...
1) i use a hyperion 1420i charger and set it to charge up to 85%. this results in each cell being 4.10-4.12. the variation isn't that some cells are 4.10 and some are 4.12 but that usually when i charge all cells are 4.10 or all cells are 4.11 or all cells are 4.12. there is some variance but 85% is good and comfortable for me.
2) i ride my bike to work (16 miles). i have a 14s3p pack so it has 15ah. i use around 9ah-11ah each way. when i charge at work, i simply charge at 14s with the leads. however, i charge under my desk with my legs a few inches away. scary?
3) when i get home, i do a balance charge as 12s and then 2s
4) when i charge, i only charge a 1C max. due to other limitations, i actually charge at a much slower rate. my 12s packs charges at around 9amps, 14s pack charges at 8amps, 2s pack charges at 10 amps. i ok with the charge taking time in exchange for safety.
5) i run low voltage buzzer/horn/blinker type things on each 6s3p (2 of them). i can visually see if any cells are going down.
6) the lowest i have ever run down a cell is 3.71v. the highest i have ever charged a cell is 4.12v.
7) i have anderson connectors and i have clips to hold the andersons in place so that any lipo shouldn't inadvertently fall out.
8) i have voltage monitors for every pack (9 of them). this allows me to visually see what the cell voltages are for every cell in my pack. however, i stopped using this. i just have all of my balance tabs in parallel and use a battery medic to analyze each 6s3p, 6s3p, 2s3p pack's parallel balance tab. i check before charging.
9) every night after charging, i store my lipos in a fireproof safe. every morning, i take them out of the fireproof safe to put them on my bike. all lipos are enclosed with floor tile wrapped with duct tape for protections and then put into a hard plastic container (similar to hard tupperware) for additional protection.
in my opinion, i feel like in many ways i am overly cautious. but i haven't had any issues yet or come close.
however, i am a bit wary of charging at work. i can't think of any other way to charge at work though. i simply charge under my desk and work...within about 2 hours the batteries are all charged up. i am thinking that maybe i should balance charge at work too rather than just every day at home (so balance every time instead of every other charge). however, doing that requires me to split up the cells a little bit into 12s3p and 2s3p.
i don't have a smoke alarm or fire extinguisher near my charging area. i charge at home next to my wife's car in the garage near my other bikes, etc. a fire would probably be really bad. i'll probably start charging outside in my back patio. and i'll buy a smoke detector.
and i usually charge at home unattended. i get home, charge, go upstairs...and come down again a couple of hours later to disconnect, etc.
sounds to me like most people have issues when they discharge a little too far. stay above 3.5 should be fine. stay above 3.7 should be more than fine...
