Dummy Batteries
erco
Posts: 20,256
No, not "Batteries for Dummies". These are 0V shunts (shorts) in a AA form factor package.
https://www.ebay.com/itm/360970021495
Designed to be used with a 3.7V 14500 Li-Ion cell, for instance in a product designed for two AA alkaline cells. Several years ago, I posted here about my then-new discovery of 14500 cells, and many of us ordered them. A week or two later, that same Chinese seller sent (for free, and unrequested), several of these dummy batteries to all of us. Pretty good service for Ebay China, I thought! (Woe be unto him who simply swaps two 14500s for two AA cells in something. Magic smoke challenge accepted!)
One of the twins got a little piano keyboard for Christmas. The included batteries died pretty quickly, so I replaced them. Turns out it's designed for 3xAA batteries, but it came with two cheap AA cells and a shunt.
Three alkalines increased the volume and should last a bit longer.
Anyway, these dummy cells popped up in an Ebay search for 14500s today and I was surprised to see that that there are a lot of sellers for these. Big demand? Apparently these 14500 cells are catching on. Of course their capacity claims are way off, and the capacity deteriorates over time. I have maybe two dozen 14500 cells, purchased ~1.5 years ago. The best capacity when new was ~350 mAh, and now those are half that. Hardly Tenergy quality, but if you use them a lot when you get them, they can be worth the quality gamble.
https://www.ebay.com/itm/360970021495
Designed to be used with a 3.7V 14500 Li-Ion cell, for instance in a product designed for two AA alkaline cells. Several years ago, I posted here about my then-new discovery of 14500 cells, and many of us ordered them. A week or two later, that same Chinese seller sent (for free, and unrequested), several of these dummy batteries to all of us. Pretty good service for Ebay China, I thought! (Woe be unto him who simply swaps two 14500s for two AA cells in something. Magic smoke challenge accepted!)
One of the twins got a little piano keyboard for Christmas. The included batteries died pretty quickly, so I replaced them. Turns out it's designed for 3xAA batteries, but it came with two cheap AA cells and a shunt.
Three alkalines increased the volume and should last a bit longer.Anyway, these dummy cells popped up in an Ebay search for 14500s today and I was surprised to see that that there are a lot of sellers for these. Big demand? Apparently these 14500 cells are catching on. Of course their capacity claims are way off, and the capacity deteriorates over time. I have maybe two dozen 14500 cells, purchased ~1.5 years ago. The best capacity when new was ~350 mAh, and now those are half that. Hardly Tenergy quality, but if you use them a lot when you get them, they can be worth the quality gamble.
Comments
-Phil
https://www.pololu.com/product/2111
Way to expensive, and I think it it's just the size of an AA lengthwise which would make it tough to cram it into a dummy cell. It's also discontinued, so I guess the idea of an AA-size regulator didn't catch many people's fancy. Oh well.
When the kids were younger I thought a remote control battery would be a good way to go. You could just turn down whatever toy to make it slower/quiter, and when it stopped, it'd be time for bed.
What about something like this https://www.ebay.com/itm/222688559736 and a lithium battery protection board?
On the Li battery protection board: do the 14500s not have those built-in? I was also thinking you'd still remove them for recharging.
Five pieces ordered & hoarded.
Hoardered?
@Gordon: I don't think any of my 14500 cells have the protection board built in. They're a bit longer than an AA cell, and already a snug fit in most AA battery holders. That board would make it worse.
Since I plan to remove the batteries for charging in a charger that already has protection circuitry in it I think I'm okay. The "regulator dummy" goes in ahead of the cell(s), so it takes up one of the cell compartments. It's more the size of a AAA, so I think it'll be okay.
Even if it won't work as a dummy+regulator I can still use them, maybe strapped to the side of the battery holder. I figured the real rating for the module is 1A. Never trust the specs of a 99 cent switching regulator with free shipping!
Agreed, I only count on half the rated Chinese spec. I figure half the magic smoke got lost in free shipping.
Actually, I was recently surprised how robust these tiny $1 dual H-bridges are. I used a bunch in my NTYF models and they took a LOT of abuse/stalls/shorts in testing. I ordered more. They brake and coast, BTW.
https://www.ebay.com/itm/Dual-Channel-DC-Motor-Driver-Module-PWM-Speed-H-Bridge-Stepper-L298N/272301540441
"Did you check the batteries?"
"They're brand new. I got a really good deal on a 24 pack."
10 questions later...
"This doesn't make sense. Wait... Are the batteries dummy batteries!?"
"They say A, A, dummy, battery. Is that bad?"
If you sell it on ebay, I'll buy a couple.
I believe that most single cell batteries do not have integrated protection and it should be added.
Well, I know Parallax's (Tenergy) cells do, as they make a note of it. I guess I shouldn't be surprised that the cheapos from overseas will cut corners. I suppose they are assuming the charger will have it.
That's my very basic understanding.
I've used a few in some of my projects and haven't released the magic smoke yet.
Has anyone figured out what IC is used? All of my modules have unlabelled IC's.
-Phil
Here's Pololu's version of it:
https://www.pololu.com/product/2135
Or this variation of it, which is quite clever. It sits atop an Arduino as a shield, but covers only the pins it needs to:
https://www.pololu.com/product/2511
TI's rating is the more conservative 1.5A /channel.
I've used this chip in other breakout boards and it's quite nice. Runs those yellow gearmotors quite well.
https://www.pololu.com/product/2136
Not Chinese cheap, but not bad at $5 bucks.
In a pinch for a dummy "AAA" battery you could use a ".44 Magnum Remington Bullet" measuring in at 11.6mm diameter by a length of 41mm. Compare that to a AAA with a 10.5 mm diameter and a length of 44.5 mm. No need to file down one end to a point <smirk> as mentioned in a earlier post above. ... just don't pass a large current through that configuration.
So one could say this Dummy Battery is also a fuse!
Mike
https://www.ebay.ie/itm/MX1508-1-5A-Dual-Channel-DC-Motor-Driver-Module-Beyond-L298N-PWM-Speed-Control-M-/152557205988
https://www.hobbytronics.co.za/p/1222/15a-2-way-mx1508-dc-motor-driver-module-pwm-speed-control
Truth table attached. Coasting and dynamic braking supported.
https://www.ebay.ie/itm/MX1508-1-5A-Dual-Channel-DC-Motor-Driver-Module-Beyond-L298N-PWM-Speed-Control-M-/152557205988
https://www.hobbytronics.co.za/p/1222/15a-2-way-mx1508-dc-motor-driver-module-pwm-speed-control
Truth table attached. Coasting (AKA Standby) and dynamic braking are both supported and work well. My new favorite H-bridge.
Interesting that there doesn't seem to be a datasheet available (at least that I could Google).
How's your Chinese?
http://sales.dzsc.com/486222.html
Google automatic translation of the text:
MX1508 SOP-16 Four-Channel Dual Brushless DC Motor Driver IC
Overview
The product provides an integrated brushless DC motor drive solution for battery-powered toys, low-voltage or battery-powered motion control applications
case. The circuit integrates two channels of N-channel and P-channel power MOSFET design of the H-bridge drive circuit, suitable for driving electric toy car steering
Wheel and rear drive, (drive brushless DC motor or drive two stepping motors). The circuit has a wide operating voltage range (from
2V to 9.6V), the maximum continuous output current of the steering wheel reaches 0.8A, and the maximum peak output current reaches 1.5A. Rear wheel drive maximum continuous output power
Flow reaches 1.5A, the maximum peak output current reaches 2A.
The drive circuit built-in thermal protection circuit. Through the drive circuit load current is much greater than the maximum circuit current, by the package cooling capacity
Limit, the internal chip chip temperature will rise rapidly, once more than the set value (typical 150 °C), the internal circuit will immediately turn off the output power
Rate, cut off the load current, to avoid the temperature continued to rise caused by plastic packaging smoke, fire and other security risks. Built-in temperature hysteresis circuit, indeed
After the circuit is restored to a safe temperature, the circuit is allowed to be re-controlled.
The
Features:
a. Low standby current (less than 0.1uA);
b. Low static operating current;
c. Integrated H bridge drive circuit;
d. Built-in anti-common conduction circuit;
e low conduction resistance of the power MOSFET;
F. Built-in overheat protection circuit (TSD) with hysteresis effect;
g. Antistatic rating: 3KV (HBM).
Typical applications
a. 2-6 AA / AAA battery powered motor drive;
b. 2-6 nickel-hydrogen / nickel-cadmium rechargeable battery-powered toy motor drive;
c. 1-2 lithium battery-powered motor drive
I'm using one of these to power 2 brushed motors for a Rover 5 chassis at 7.2V:
https://pololu.com/product/1551
I've not noticed any issues (heat, shutdown, or malfunction), even with repeated start/stop sequences or stalls. Just the board, no additional heatsink.
BTW, the stall current of these motors (2.4A) is greater than the chip's (2.0A) limit.