Might have to pay extra for the non stop recording feature haha
2 Likes
Those youtube views will make it worth it.
2 Likes
Bro. You have a fire-proof lasso? I want in.
Did that come with @Elon 's flamethrower?
Oi mate I hear you on this one keeping the home and fam safe is a top priority. Iv been looking into preventing ignition on these so far the best solution is to charge it in a stone of steel box if one has the space. If not wrapping it in some fiberglass/fireproof insulation would be next best thing it doesnāt stop the smoke but it does keep the flames contained. If I were to sell these though it would be be sold inside a vented steel enclosure or a fiberglass enclosure that covers the entire battery top bottom and all 4 sides.
1 Like
Iāve thought a lot about this over the yearsā¦
No way to prevent one cell from going into runaway if the conditions are right (temperature, over-charging, physical damage, etc.) but we can do a lot to prevent that single cell disaster from spreading to other cells.
Unfortunately that involves fire-proof materials between the cells and/or a lot more space between them. Cell-level fusing has some usefulness for helping to prevent other cells from possibly going into thermal runaway too but itās tough to do this DIY. Just so many unknowns with the existing āfusedā nickel strip.
4 Likes
I think it would be great to FLIR test battery packs after high discharge and while charging to identify hot spots from time to time. That way you could prevent Forest fires. After looking on ebay this seems to be about a $200.00 + investment . Maybe battery builders could offer FLIR tested batterys for alittle peace of mind. I always just use my hand to feel for heaters before putting battery pack into enclosure.
2 Likes
Best way to stop the fires is to prevent them. Build the battery correctly or donāt do it at all.
We can all chip in by yelling at bad battery builds on facebook as well as call out manufacturers
4 Likes
Even if its built right the problem comes down to the cell level and problems are expressed in heat that cant be easily seen or felt through an enclosure. It all starts with heat.
2 Likes
Thatās true, it will always be a risk.
Would be cool for these smart bmsās to have temp sensors for each p pack.
1 Like
As a battery builderā¦
fuck
3 Likes
As of right now Iām just monitoring the temp of the whole battery with one sensor. The heat of one is the heat of it all in a box. 10.00 battery meter with temp probe wire
It can certainly be done but would require additional circuitry, cost, and circuit board space. The wiring up and installation a dozen or more temp sensors is something to consider too. 
We also have to consider what temp sensors can actually do for us. For slow changes in temp that spread out over the entire p-group (or pack if only one sensor) an inexpensive thermistor temp sensor can work well but will only tell us that the pack is being used too hard or thatās itās too cold to charge the pack.
Since only one temp sensor would be used per p-group it wouldnāt be very useful in identifying a cell that has failed and is quickly overheating unless we were lucky enough to have the sensor be touching that particular cell.
If the cell was failing, and we did detect that, then the BMS wouldnāt be able to do much more than shut off the current. That might stop the cell from going into thermal runaway but it might already be too late and the temp rise we detected was a cell already in runaway.
Iām a huge fan of temp sensing but it does have some limitations that we have to carefully consider in the design and layout of the pack along with what sensors we use, where to install them, if heat spreaders are used, and what reactions to particular temps are programmed into the BMS or dedicated temp protection circuits.
Your post has given me a couple ideas to consider thoughā¦
4 Likes
So, I did want to go for a few laps around the neighborhood so I took it off the charger. Nothing happened after leaving it on for close to a day. Took it for a spin from 49.7v to 47.2v.
These were the groups voltage before the ride:
Plugged it back on the charger this morning and it just turned green, will leave it on the whole day. These are the voltages after the green light:
1 - 4.18
2 - 4.13
3 - 4.19
4 - 4.20
5 - 4.20
6 - 4.19
7 - 4.19
8 - 4.23
9 - 4.18
10 - 4.19
11 - 4.23
12 - 4.20
Is it an issue for those 2 to over 4.2?
I am still going to leave the pack on the charger for longer this time and fight the urge to go for a ride.
1 Like
Most BMS boards have their overvoltage protection set around 4.25v, +/- 0.05 v.
4.23 is just a hair overcharged, but I wouldnāt say itās high enough for serious concern.
Keep an eye on it - Those two should get knocked down pretty quickly (in balancing terms - say an hour or two?)
2 Likes
Bring #8 and #11 down and it should be fine. You want no more than .05 difference or less. Anything above that you want to balance back in
1 Like
What charger are you using?
1 Like
Both groups are now at 4.24 I will be keeping an eye on them.
If those 2 groups arenāt balancing, do I have another case of dead cells/bad weld?
What voltage does it output?
Iād say open it up and reduce the voltage with the potentiometer.
(Iām not quite sure if the bms pushes the cell that high or if the charger outputs more voltage than the 50.4)
1 Like