LiIon Battery Question

Den onsdag den 7. december 2016 kl. 18.55.42 UTC+1 skrev Jim Thompson:

Thanks, Lasse! _Precisely_ the info I was seeking!

(I'm writing a Spice model for Microchip MCP73831/2 and the datasheet is just a wee-bit vague ;-) ...Jim Thompson

Let it discharge too low and on charge it may burst into flame.

Charge it too high and it may burst into flame.

Not always -- but enough that anyone who flies electric RC has an acquaintance who has, or has nearly, burnt their shop down.

I'm getting a more burly Lipo charger for my son. Should we set up some kind of flame proof table to charge on?

George H.

After the recent Samsung episode I leave no LiIon battery charging unattended. But a flame-proof table/surround might be a good idea. ...Jim Thompson

you can get a fancy pouch for charging

I've seen some put batteries in an old cooking pot while charging

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Pouch, cooking pot, metal ammo can, corral of bricks, charge on the patio (if you live in temperate climes), etc. I charge them in an ammo can (and haven't had one go poof -- but one of my RC club members had one catch fire in his basement, and it burnt through a piece of scrap carpet before he could get it out the door).

A friend of mine who flies in competition and who is REALLY detail oriented says that just charging them warm and letting them cool is a Bad Thing, because the capacity drops with temperature, turning a fully charged battery into an overcharged battery.

If you didn't get him a balancing charger, get him a balancer.

Ahh I've got these big metal tins I've been wondering what to do with. Now I know.

George H.

Hmm I don't know.. he picked out this one.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

A flame proof charging container for Li battery powered devices might make a good product.

Reality Check... Are you building a hobby project or designing a product for sale? If the latter, is the volume high enough for you to risk designing the battery system? You can buy assembled battery packs that are designed by people who know what they're doing and lower your personal risk.

If somebody gets hurt, you may be called upon to demonstrate that you applied all the appropriate safeguards. The ONLY place you can get the required information is from the actual vendor of the exact battery. I don't think getting answers from random inputs on usenet qualifies as due diligence.

Requiring the user to buy a new battery to replace one that might have been recoverable disappoints the user. Exercising your design skills to recover an over-discharged battery can render you bankrupt.

jumbo-

It's a balancing charger. Fancy.

Neither. You missed my second post...

"(I'm writing a Spice model for Microchip MCP73831/2 and the datasheet is just a wee-bit vague ;-)"

RC stuff is fun, he's into quad copters w/ first person view... (CCD camera on the copter feeding video back.) He did ask me to help him build a 3-terminal voltage regulator. But mostly he's building his own, from watching videos. He has asked me about PID control loops. :^)

George H.

I store mine in a cinder block.

Send it back. You have plenty of time until Christmas:

Drivel: I've been learning to fly my quadcopter (Walkera QR X350 clone) indoors. It's much more difficult indoors than outdoors. So far, nothing broken, and getting better with practice. Blade guards and adjustable control sensitivity are a big help. There is nothing like lying in bed while flying a drone around the house: Hint: I'm not married.

"the boy" has a little copter he flies around the house. About the size of a deck of cards. (smaller is easier.)

George H.

low_voltage_cut_off

Have him watch my videos, and then tell me what he thinks!

AFAIK, the state of the art in hobby quad-copter PID tuning is to use a seat of the pants method similar to what I describe in my video. If I'm correct, this leaves out a lot of nonlinear effects (like actuator saturation) that means you're not getting the most out of the thing in sudden maneuvers.

So far I haven't dug deep into that particular mine of knowledge.

Be aware that - despite what that article infers - NOT_ALL Li-xx batteries incorporate protection modules. In many appliances, the protection circuitry is built into the charge controller which is part of the appliance. That keeps the battery (well, cell really) simpler aka cheaper.

In a typical laptop battery (3-series N-parallel 18650) the *cells* contain no protection as it is incorporated into the pack electronics.

It's far worse than that. Most quadcopters do not even have a protective fuse in the battery line. The on-off switch consists of uplugging the (Deans, XT60, etc) power connector. None of the brushless motors have thermal cutouts. Fire and smoke are fortunately uncommon, but still happens:

Various low-voltage alarms and cutoffs are available as add-ons.

The usual excuse for not having any protection is that it adds weight.