What battery to choose after your last one burned your house.

[TheBeastie]

What I ended up with after my fire, was a no longer usable electric oven. Its outside now, away from the house, and I keep all my batteries in it. I charge in the open air, on the glass cooktop.

My batteries do freeze in the winter in there, but it could be heated.. When its that cold, I'm pedaling now, so I go slower and stay warmer. But on a nice winter day, I put the cells in the sun for an hour to thaw before I charge them, if actually still frozen.

Just thinking maybe you could use a mini heater in the broken oven to keep them warm?
There are tons of quirky gadgets on ebay these days..

USB warming pad... put this in the oven, would be low power if it can be plugged into a USB, you could just cut the USB connector and power it with regular 5volts if u don't have USB power source. The power usage would be about 10w.
https://www.ebay.com.au/itm/1X-USB-5V-10CM-21CM-Heating-Heater-Winter-Warm-Plate-For-Waist-Shoes-Pad-Ih-J-AU/362788634811

https://www.ebay.com.au/itm/5V-USB-Electric-Cloth-Heater-Pad-Heating-Element-for-Pet-Belt-Warmer-Durable/254302767256
I am surprised they didn't include wifi connectivity https://www.ebay.com.au/sch/i.html?_nkw=usb+heater&_sop=12&rt=nc&LH_PrefLoc=2

Or even just an old electric blanket..

Then top it off with a wifi temp sensor, lots of quirky gadgets on this search key words https://www.ebay.com/sch/i.html?_nkw=wifi+temperature+sensor&_sop=12

 

[sleepy_tired]

You don't need a mini-heater.

Just wire in a incandescent light bulb. 60 watts or something like that. 60 watts of heat is plenty to keep something warmer then ambient in the winter.

 

[flippy]

You don't need a mini-heater.

Just wire in a incandescent light bulb. 60 watts or something like that. 60 watts of heat is plenty to keep something warmer then ambient in the winter.

and how would you cram a light bulb into a battery? and why would you waste energy on creating light when you need heat?

 

[obcd]

I see temperature monitorring as a functionallity of the BMS board. It turns off the charger if the cell voltage goes above 4.3V. It should also turn it off if the temperature goes above 50 - 60 degrees celcius. (Not sure what is still considered safe) It should also disconnect the load if the battery pack becomes 2 high.

I wasn't intended to stick a thermometer between my cells and read the temperature every hour. A way to retrieve the data (even if it's just maximum and minimum) could help analyse premature failures. If your pack suddenly starts to become 10 degrees hotter during charging than it used to do, you can expect some issues. (Unless then environmental temperature was 10 degrees higher as well).

Most aftermarket chinese bms boards don't seem to care about the temperature. On the question, what is a good BMS, I would call those simply bad. A good one should give you an option to check individual cell voltages and maximum values for temperature, charge and discharge current. In case of a short circuit, it should disconnect the cells before they go in thermal runaway.
They will be more expensive, but safety is worth something in my opinion.

 

[mark5]

You don't need a mini-heater.

Just wire in a incandescent light bulb. 60 watts or something like that. 60 watts of heat is plenty to keep something warmer then ambient in the winter.

and how would you cram a light bulb into a battery? and why would you waste energy on creating light when you need heat?

The light bulb must be for inside the oven where the battery is kept.

 

[flippy]

You don't need a mini-heater.

Just wire in a incandescent light bulb. 60 watts or something like that. 60 watts of heat is plenty to keep something warmer then ambient in the winter.

and how would you cram a light bulb into a battery? and why would you waste energy on creating light when you need heat?

The light bulb must be for inside the oven where the battery is kept.

why would you bolt an oven to your bike or scooter?

I see temperature monitorring as a functionallity of the BMS board. It turns off the charger if the cell voltage goes above 4.3V. It should also turn it off if the temperature goes above 50 - 60 degrees celcius. (Not sure what is still considered safe) It should also disconnect the load if the battery pack becomes 2 high.

I wasn't intended to stick a thermometer between my cells and read the temperature every hour. A way to retrieve the data (even if it's just maximum and minimum) could help analyse premature failures. If your pack suddenly starts to become 10 degrees hotter during charging than it used to do, you can expect some issues. (Unless then environmental temperature was 10 degrees higher as well).

Most aftermarket chinese bms boards don't seem to care about the temperature. On the question, what is a good BMS, I would call those simply bad. A good one should give you an option to check individual cell voltages and maximum values for temperature, charge and discharge current. In case of a short circuit, it should disconnect the cells before they go in thermal runaway.
They will be more expensive, but safety is worth something in my opinion.

check the bluetooth bms thread. those have the functionality you seek

 

[E=IR]

Lead acid

 

[obcd]

This still leaves me with the question why they don't provide a fuse on every cell?
Even commercial ebike batteries don't seem to have it.
I watched some youtube videos of guys creating batteries for power walls (Something like 40P or 50P) and they do provide a fuse wire on every cell. Obviously, 40 cells releasing their energy into a bad one is worse than 4 cells doing it, but even 4 can release a lot of energy, likely enough to seriously heat up a bad cell.
Maybe the nickel strips work as fuse and burn trough in case of an issue? (I doubt it as they seem pretty solid)

 

[flippy]

This still leaves me with the question why they don't provide a fuse on every cell?
Even commercial ebike batteries don't seem to have it.
I watched some youtube videos of guys creating batteries for power walls (Something like 40P or 50P) and they do provide a fuse wire on every cell. Obviously, 40 cells releasing their energy into a bad one is worse than 4 cells doing it, but even 4 can release a lot of energy, likely enough to seriously heat up a bad cell.
Maybe the nickel strips work as fuse and burn trough in case of an issue? (I doubt it as they seem pretty solid)

simple, its cost with these puny batteries.
once you get into scale like tesla with 8500 cells in a single car pack you just program a robot to do it and then its the cheapest and fastest method of making a pack. but nobody that builds small batteries is going to spend hunderds of thousands of american roebels to buy a industrial robot with a wire feeding weld head.

it also does not serve any purpose. each cell has a PTC disk in it that will pop if a cell goes postal and reduce damage to cells next to it.

the people that do DIY cell fusing simply do it because they think it will protect them from damage. it wont. once you reach the point where you pop cell fuses you usually got way bigger problems and you didnt put in the proper protections (like a bms) in the first place.

 

[sleepy_tired]

You don't need a mini-heater.

Just wire in a incandescent light bulb. 60 watts or something like that. 60 watts of heat is plenty to keep something warmer then ambient in the winter.

and how would you cram a light bulb into a battery? and why would you waste energy on creating light when you need heat?

The light bulb must be for inside the oven where the battery is kept.

why would you bolt an oven to your bike or scooter?

You have seemed to lost the thread. He was going to store the battery in a old oven in his backyard when it wasn't being used or charging it something like that. The only person suggesting that we bolt a oven to a bike was you.

If you want to protect the battery from the cold while riding, or something like that, then I always figured a custom neoprene foam rubber cover would do the trick. Since the battery generates it's own heat while being used. Never tested it out though.

 

[sleepy_tired]

Even commercial ebike batteries don't seem to have it.

Em3ev fuses their cells in most of their batteries. They also fuse the balance lines.

it also does not serve any purpose. each cell has a PTC disk in it that will pop if a cell goes postal and reduce damage to cells next to it.

the people that do DIY cell fusing simply do it because they think it will protect them from damage. it wont. once you reach the point where you pop cell fuses you usually got way bigger problems and you didnt put in the proper protections (like a bms) in the first place.

That's extremely silly set of conclusions, I think. The reason for your confusion probably has to do with a misunderstanding about the purpose of the fuses. I tested my fuses before I put them inside my battery and they work extremely well at protecting things. They blow out very reliably and long time before the cell even gets warm, much less before it pops it's top.

This sort of thing is the difference between a trivial repair versus cataclysmic failure.

Imagine you are building a battery for a 40 amp controller. It's 14s8p battery. So you are looking at a maximum of 5 amps per cell. So you put a fuse on each cell to blow at 15 amps and you keep it very short to limit the voltage drop. That's far above what you expect to see and far below the level at which a cell will pop it's top.

Now you are riding around on your bike and fall over. The battery gets bashed against a rock and something lets loose inside or one of the cells gets smashed (or something along those lines) and the battery develops a internal short. In a split second the fuses surrounding the damaged area blow and while your battery is now mostly disabled you have the advantage of not having a fire develop a couple minutes later.

Or how about a situation were now your battery is a couple years old and nearing it's retirement. Unbeknownst to you a few of the cells have a manufacturing flaw and for whatever reason one of them develops a internal short. So instead of the battery discharging through that cell and having it barf it's super heated electrolyte all over the inside of the battery it's fuse pops and now you are just down one cell in one of the groups. Hopefully you have a communicative BMS, either through external display or bluetooth or serial connection, so you can identify the problem rather then being left scratching your head about the loss of capacity.

 

[flippy]

if a cell faults internally bad enough the PTC will pop, no fuse needed and i have seen quite a couple of tesla packs that have been in accidents and have never seen a blown fuse wire.
cheap cells will just start leaking. i got plenty of examples of batteries i got on my bench that were just months old and pissed out their liquids all over the rest of the cells. but they still accepted current, the PTC only leaked, it did not pop.
with proper cells this wont happen.

still, you can break the fuse wire but that wont stop any short inside a cell. the cell will still heat up and vent and if you have a crappy cell it will also vent flames. and if you have a crappy battery box that punctures cells during a fall it probably wont protect other cells from popping their plastic PTC disk during that venting flames so it will cascade into the enitre pack. and not a single fuse will have melted.
still, if you crash hard enough to break a 18650 cell in a accident i am pretty sure my statement that you have bigger problems at that point still holds.
if a cell shorts out it usually does that "gracefully", so no instant fail but you will see it heat up and eat up all the volts in the P group and trigger the bms to fault and killing the output. so you know very fast something is wrong.

unless you have a massive battery with dozens of cells in P you will not pop a cell fuse.

 

[fechter]

Well designed fuse links won't hurt anything and may protect against certain types of faults, but I have seen many cases where they wouldn't help. If a single cell shorts internally (or externally) and vents with flame, just the heat alone is often enough to set off the adjacent cells and it propagates until the entire pack burns up. I have also seen Tesla pack fires where there was a big short somewhere and a large section of the pack goes off at the same time with a huge fireball.

Not all cells have PTC devices, but i think most have a CID, which will open the circuit when the cell pressure gets too high. This rarely comes into play unless you overcharge a cell.

 

[dogman dan]

My assumption has always been that in my fire, the bms failed, a cell overcharged, and vented flame. This dominoes to all the other cells.

Fuses are great at protecting from shorts. a fuse type connection between each parallel group of cells in a bike pack seems like a good idea to me. Every cell, I don't know if that would be enough better or not. In any case, a bms that fails and lets a pack overcharge is not something a fuse would help you with.

RE the oven. The idea here, is that no big bike batteries enter my home again. When they freeze overnight in the winter, no harm is done to the cells. Harm would only be done if I charged them, or discharged them while frozen solid. I can be sure that I have zero interest in riding my e bike in temps that low. 25F maybe, for a fun snow ride. For that I can warm them easy enough. As said above, incandescent light bulbs are good heaters, as are many other devices. But I don't need to heat my batteries to commute anymore. I will ride later in the day, when its 50F and the batteries are thawed.

The oven simply provides a somewhat insulated box, so that there is a bit less heat in that storage in summer. Some thermal lag so they don't hit 100F quite as early in the day as they would otherwise. Much like my garage was, when I was charging the bike in the garage. Other good outside storage can be a small, possibly broken, old fridge.

Lead acid would have been my choice, if I had to have my bike battery inside the house again. But the original point of this thread was this..

They are not coming inside again, ever. Therefore, I could choose a known to be dangerous type of battery. ( Turnigy lipos) I don't trust them at all, so no need for lifepo4, or lead, or whatever. They can flame away out there inside that oven, if they do.

BTW, I got sent a Luna battery last spring for free. I don't trust it either, its out in the oven. Its clearly way superior in cell type and construction to the piece of crap that burned my house. I believe it does have fuse links inside it. Hopefully a more reliable bms too. But its outside, its staying outside, and its charging outside.

I could give a crap what this might do to its lifespan. Paying for batteries sooner beats the shit out of burning your house down.

 

[vreppeto]

My 18650 pack, was not good cells though, so it lasted 18 months then burned down the house. Best guess on the cause was failure to stop the charge by the bms. Or maybe, the cause was even simpler, I trusted a cheap ass bms.

No judgement from me. I am grateful you are willing to share these details to save me from a similar fate. So can I assume one of the takeaways here is that redundancy is key in development of a safe charging protocol? I am thinking a smart bms and a smart balance board so either can stop the charging process. I tried a resistive analog balance board by itself and it made me glad I was charging lifepo4 cells at the time.

 

[vreppeto]

I think LiFePO4 are slightly safer because they pack a smaller absolute quantity of energy into a larger volume and a larger mass compared to smaller and lighter Lithium-ion chems like NMC. I don't think LiFePO4 chemisty is safer because of any specific quality inherent to specific proprieties of the chemical used... At least to my knowledge (I'm a chemist, organic chem to be specific, but i'm not an electrochemist).

Someone said something about A123 lifepo4 being extremely volatile so it is not always true but the liitokala 32700 lifepo4 cells seem to be pretty safe. I was charging 16s2p in a honeycombed pack with hot glue and shrink tape. The analog balance board failed and I was sitting right next to it the whole time. The failure was so gentle I had trouble figuring out where the little intermittent pop was coming from. I had been taking measurements every few minutes but I got complacent when I thought the balance board was doing it's job. Some cells had reached 3.8v and were not climbing any higher, or so I thought. The temperature never got high enough to melt any of the plastic insulation on the cells or the sense wires. I will add a decent bms and a redundant charge cut off circuit and likely discard the analog balance board. A metal box sounds like a good idea too as well as fish paper separators between series cells.

 

[john61ct]

A123 **LFP** is as safe as any LI gets

well maybe LTO. A123 makes NMC other types that are indeed less safe.

Those safer chemistries are indeed **inherently** safer, less prone to thermal runaway.

Less known-good makers like Liitokala may not have as good longevity, build quality etc compared to A123

but really the fire-safety issue is much more the chemistry chosen than the maker.

 

[999zip999]

It's stored energy it's a lightning bolt in a box. tNo matter what no matter what chemistry it's still a lightning bolt in the box and the light import would just love to get out. That said A123 is pretty darn safe see what they've been hiding.

 

[sharinginfos]

hi everyone
i found that from their test lifepo4 does not propagate

Did any one have a house fire with lifepo4 to begin with?
What do you think @matador?



about the fires I read that yes lifopo4 can catch fire but not propagate to other cell so only one would fire not the neigbourscell. to combust them you need to torch them with an external flame torch. They seem very safe. a link a doc made by fireman similar

:extract from https://www.fire.tc.faa.gov/pdf/TC-16-17.pdf

Figure 17 shows the
results of the Li-ion pouch cell propagation tests. This figure shows the number of cells, out of
the five that were physically connected together, that experienced thermal runaway. All of the
cells, except for the LiFePO4, achieved full propagation to all five cells. Thermal runaway of the
LiFePO4 cell did not propagate to any of the cells beyond the initial one that was in direct contact
with the heater.
the conclusion says also In general, of all of the lithium-ion cells that were tested, LiFePO4 would be considered the
safest cathode material because of the relatively low temperature rise and the resulting low
likelihood for thermal runaway to propagate.

 

[lnanek]

So my new battery will be a modest 12s 10 ah, of 6s turnigy packs.

For extra safety 1) only ever charge the cells individually via rc balance chargers and 2) lock the whole thing up in a metal ammo box. Luna's ammo boxes are ridiculously cheap military surplus. I've got some loud cell voltage alarms on my latest battery, which are super cheap too, and a powerful active balancer which is not so cheap.

 

[RootedSuperuser]

just for these reasons i refuse to work with pouches

BINGO, We Have A Winner!

 

[sharinginfos]

So my new battery will be a modest 12s 10 ah, of 6s turnigy packs.

For extra safety 1) only ever charge the cells individually via rc balance chargers and 2) lock the whole thing up in a metal ammo box. Luna's ammo boxes are ridiculously cheap military surplus. I've got some loud cell voltage alarms on my latest battery, which are super cheap too, and a powerful active balancer which is not so cheap.

Hi inanek what do you mean by always charge the cells individually? are you talking before the battery assembly or like every single charge after you charge them one by one even though they are in a apack?

could you provide a link to the voltage alarm?

 

[sharinginfos]

would you have suggestion on how to charge a battery outside for the people living in -30 C winter?