Radio shack closing selling li-ion rechargeable half price

[Hummina Shadeeba]

Deworld brand rechargeable li-ion. Radio shack filled chapter 7 bankruptcy, or 11, whichever has not all the stores closing. Some stores have them there or you can have them sent from other stores

But they have a discharge limit in the battery. Will that disable them from being put in series for a greater voltage?

 

[neptronix]

A link to the product would be helpful to answer your question.

Funny story, i was at a radioshack a few months ago. I took my bike into the store, as i usually do. The manager got huffy and told me i couldn't have my bike inside because of insurance ( not knowing that it was an ebike ). I asked if he had bike parking, he said no ( of course ). So basically, i got shooed out of the store. I've never had that happen in Utah, all 3 years i've been taking my bike inside various stores ( 99% of them have no bike parking ), so that was messed up..

A few weeks later, i drive my car there, thinking that they may have a closing sale because i read about the bankruptcy. One employee told me that the store was not closing, so i told her that the bankruptcy means that the store is most likely closing.. two employees just looked at me like i was from outer space. Like i was making up shit. :lol:
What a crooked company. They didn't even give their employees any notice of what was happening, apparently.

Anyway, most of the batteries they've sold have been not only crap, but wildly overpriced crap. Go look at a spec sheet for the cells you're talking about, and we can find out if you have a gem here or not.

 

[Hummina Shadeeba]

Maybe crap I don't know anything and my search for reviews just gets personal stories from Amazon or similar. Amazon buyers seem to like them even paying full price

But all the stores are not closing I heard today. Chapter 7 bankruptcy. Or 11. Most stores are closing

 

[mark5]

The batteries might be these referenced in these threads (1, 2).

 

[neptronix]

Oh, those are pretty substandard batteries then. 2000mah is oldschool lithium tech, and possibly even old stock. I wouldn't even buy a pair for half price.

 

[Hummina Shadeeba]

ok. I don't even need any batteries but thought maybe it was a deal. seems not.

but what of the discharge limit or protection? Can you put these in series or will it trigger a fuse or something?

 

[neptronix]

They're rated for a 2.5 amp discharge. What happens after doing that continuously for a long time is probably self-immolation from heat buildup. ( we can find this out by looking at a discharge graph if we have one ).

Batteries have amperage ratings for discharge and charge rates. They usually don't come with fuses. Nothing is preventing you from misusing them, other than thermodynamics and chemistry :lol:

 

[Hummina Shadeeba]

I thought they have.. not a fuse but some type of circuit inside which will limit how much amperage and maybe voltage will pass through them. so just an amp limit? and then if they were in series that would be a problem right? assuming I'm using up to 30 amps

 

[neptronix]

Nope. No fuse or limit. The controller is the thing that does the limiting.

If you're asking questions like this, there is a lot that you need to know Start reading up about batteries and how they work:

http://batteryuniversity.com/

 

[Hummina Shadeeba]

ive seen cells with small circuit boards that limit the cells individually. I read they can not be put in series. You have not seen these?

I thought a bms could also limit the discharge?

 

[neptronix]

Oh yes, those are low voltage/high voltage cutoff limiters, usually used for electronic devices that do not contain such circuitry. I doubt that you could properly solder to one of the pcb's outputs/inputs... and said device will probably also limit the battery output amperage by inducing a failure point if you go over X amps.

A BMS or controller's low voltage cutoff performs that function in an ebike battery.

ive seen cells with small circuit boards that limit the cells individually. I read they can not be put in series. You have not seen these?

 

[Hummina Shadeeba]

so the discharge limit on these batteries likely contain such a voltage limit? and then they would be no good for building a pack with because of that limit and also the circuit would melt with too much amperage right?

another question...unrelated. I'm skyping with china trying to get motors made. hub skateboard motors, thread in the skate section. they have what I want in size but the laminations are .5mm . at first I thought maybe it could saturate with flux being a hub motor with low kv and needing lots of flux, but this doesn't happen. will the eddy current be more of a problem with the roughly 100kv motor (53mm stator) and strong magnets and the thick laminations be more of an issue?

 

[neptronix]

The discharge limit is 2.5a, as seen on the battery info sheet.
They are limited by voltage via chemistry. IE, you charge them above their voltage and they blow up, smoke, etc.
To be clear, there are no limiting circuits in this battery. It's a chemical energy storage device like any other battery. Your charger, BMS, controller etc. all take care of the voltage of the whole pack for you.

Those batteries with 'protection circuits' just turn the battery output on/off if the cell hits the top or lowest voltage they're set to. But the protection circuit is unnecessary and creates a disbalance in a pack with what, 50-1000 cells, where the BMS does that job. The circuit itself also might be limited in how much amps the cell can output as well.

You want 0.33-0.35 laminations for any motor you design, ideally, to increase efficiency and reduce eddy currents. I'm not a motor design expert though, that's for someone else on another thread.

so the discharge limit on these batteries likely contain such a voltage limit? and then they would be no good for building a pack with?

another question...unrelated. I'm skyping with china trying to get motors made. hub skateboard motors, thread in the skate section. they have what I want in size but the laminations are .5mm . at first I thought maybe it could saturate with flux being a hub motor with low kv and needing lots of flux, but this doesn't happen. will the eddy current be more of a problem with the roughly 100kv motor (53mm stator) and strong magnets?

 

[Hummina Shadeeba]

im forgetting circuitry 101. These batteries don't have a limiting circuit you say, but if they did, and you were to put them in series....the voltage would increase at each additional cell and so would the possible amperage output right? so the last battery in the series chain would be the one to most likely trigger a limiting circuit, if there was one?

 

[neptronix]

No, that's not how batteries work. Read the battery university site, as you have a lot to learn before you start building packs. I'm prescribing you 5 units of 101..