New answers tagged

4 votes

9V battery open circuit 8.5 volts but reduces to 2V when connected in series with a 300 ohm resistor across the resistor. Why isn't it 8.5V?

Your 9V battery is almost exhausted and has an internal resistance of about 1kΩ. A fresh battery would have an internal resistance maybe 1/500 of that. So the circuit looks like this: simulate this ...
0 votes

Portable Xiaomi speaker passive radiator need space?

Bass reflex speakers are mass-spring resonant systems. The main driver applies pressure to the spring, which is the volume of air inside the box. At the other end of the spring, there is the mass of ...
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1 vote

Is there a better way to power this circuit from a battery?

Abandon the regulator: Use a CR123A/CR17345 3V Lithium battery @1500mAh. Low discharge, no loss in regulation, or, 2xAA Energizer L91 "1.5V" (1.8V when fresh) @3000mAh Other Lithium cells ...
  • 3,011
1 vote

Is there a better way to power this circuit from a battery?

This is not really an answer, but there's too much here for a comment. Let's try to understand the consumption, before going about fixing it. We have 600 s of sleep at around 22 uA (LDO+MCU), and then ...
  • 148k
4 votes

How will be the energy consumption curve of a Li-Ion / Li-Polymer charger?

Short answer: No Longer Answer: What's written as power consumption (or delivery) of a device is always the maximum power consumption. In some cases it might be, what the devices really use but in ...
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1 vote

Is there a better way to power this circuit from a battery?

Any feedback would be great, as I am confused as to what the best / standard way would be to go about this. I see no reason why you wouldn't choose a switching buck regulator that can work down to 3 ...
  • 404k
1 vote

Portable Xiaomi speaker passive radiator need space?

The entire speaker is too small to produce low bass frequencies. It might produce down to 100Hz then it misses producing more than 2 octaves of bass. The internal space and passive radiator are ...
  • 2,803
4 votes

What is the point of a high discharge rate Li-ion battery if the wire gauge is too low?

As others have said, the ampacity of a wire is typically based on how hot the insulation can get. One thing to keep in mind is that when you discharge a battery at 50 C, by definition, the discharge ...
  • 27.5k
6 votes

What is the point of a high discharge rate Li-ion battery if the wire gauge is too low?

As others have explained, current capacity of a given gauge of wire is based on temperature rise, insulation rating, and conditions that add to or remove the heat generated. There is also the I^2t ...
  • 3,303
4 votes

What is the point of a high discharge rate Li-ion battery if the wire gauge is too low?

The fusing current for bare copper wire in free air is about 333 A. This can be higher or lower depending on how the air flows. This is a melting temperature of 1084oC Most wires that we use are ...
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14 votes
Accepted

What is the point of a high discharge rate Li-ion battery if the wire gauge is too low?

AWG 10 is 1 Ω per 1,000 feet. So, 1 foot of wire (305 mm) will be 1 mΩ (that's 1 milli ohm). I don't know how much wire is needed to wire up a battery pack but it's going to be less than 305 mm. So, ...
  • 404k
4 votes

What is the point of a high discharge rate Li-ion battery if the wire gauge is too low?

Because the "50C" rating is utter and complete rubbish. It would mean discharging the battery in 72 seconds. No Li-ion cell can survive being fully discharged that fast without some serious ...
0 votes

Battery over-discharge protection

When I need to design a circuit, I do an image search for the name of the circuit. Like this: low voltage cutoff circuit.
0 votes
Accepted

Circuit for Li-ion cell cycling testing

No, it won't (sorry). The 0.5 C charging and 1 C discharging current is on the order of 1 to 10 A (depending on the capacity of the Li-ion cell under test). For that kind of current, you need a relay, ...
0 votes

Reduce current pull in circuit

As DrMoishe Pippik mentioned in his answer, the usual solution is PWM, which permits you to control average motor current very efficiently. The downside is the relatively complex circuit to produce ...
0 votes
Accepted

Choosing either 1S4P or 2S2P configuration with a 21700 battery (3.7V) for 3.3V Supply

If you are looking for a cheap solution, an LDO or linear regulator of sorts should do the trick. But then also consider how you will manage charging and ensuring the battery does not get too low. I ...
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0 votes

Reduce current pull in circuit

If an off-the-shelf pulse-width-modulator (PWM) doesn't provide low-enough average current drain, and RPM is of no consequence, replace it with a CMOS timer. The TS555 typically draws ~100 µA, so ...
0 votes

Choosing either 1S4P or 2S2P configuration with a 21700 battery (3.7V) for 3.3V Supply

Both solutions can be good, this is more a price (and availability) problem to find an efficient buck converter while using the 2S battery or a buck boost to use 1S configuration. Another important ...
6 votes

Candle light flashing LED (max. 5V) burnt by attaching LiPo battery (3.7V)

The burned LED is what should be the expectation by connecting it directly to battery. You seem to have a misunderstanding about the LED. The lithium battery won't be 3.7V. It will be about 4.2V when ...
  • 104k
6 votes
Accepted

Candle light flashing LED (max. 5V) burnt by attaching LiPo battery (3.7V)

Perhaps you connected it backwards. This kind of part has an internal IC that should operate from a 3.6V battery directly, at least by my reading of the current datasheet downloaded from the ...
3 votes

Candle light flashing LED (max. 5V) burnt by attaching LiPo battery (3.7V)

Did you put a resistor in series to the circuit for the current limitation? A battery provide 3.7V, and without a resistor which limit the current, the current will exceed the maximum rating of the ...
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5 votes

Candle light flashing LED (max. 5V) burnt by attaching LiPo battery (3.7V)

According to the datasheet the LED should take anything from 2.5 to 5V ... Correct. So, if the forward voltage of the LED is only 2.5 V then a very large current will flow and destroy the LED. A ...
  • 165k
0 votes

Can three 7Ah batteries be connected with one 22Ah battery?

In short, YES I see as a viable solution, considering the following conditions: (1) If the Four batteries have same chemistry and manufacturer, they may follow the same discharge profile. (2) If all ...
  • 1,237
1 vote
Accepted

Replacing three AAA batteries with a 3.7 V, 1200 mAh lithium battery

About replacement of 3x AAA by 1x Lithium: AAA batteries can be either Zinc-Carbon, Alkaline or NiMH. Working voltages then can be as high as 3x1.6 = 4.8V to as low as 3x1.0 = 3V. This voltage range (...
  • 1,237
3 votes
Accepted

Convert 6 V motor to run on 4.8 V

Probably no change at all. The 'end point' for AA batteries is around 1 V, so the sharpener still ought to be producing a reasonable amount of speed and torque at this voltage. The output voltage of ...
  • 148k
0 votes

1.2 V AAA rechargeable batteries, voltage for almost fully charged cell

Energizer has their Ni-MH batteries made in Japan and have the same features as Panasonic Eneloop cells so they are probably re-labelled Eneloops. Wait a minute! My newest AAA Energizer and AAA ...
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-2 votes

Charging 2 12V batteries with a 19V 3.42A laptop charger

Yes, it is possible. I have been doing it for years. I have a Jeep Wrangler that I only drive in summer time. The day before I plan to start using the car, I charge the battery overnight with a 19.2V ...
2 votes
Accepted

Reversed battery protection vs reverse discharge protection

Reversed battery is about an incorrectly connected battery (plus and minus swapped by mistake). Reverse discharge is about the battery discharging through the IC after charging is complete and has ...
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0 votes

12 VDC to 380 VAC for 1 kW, 3-phase motor

Assuming about 80% overall efficiency, a 1kW motor at full load will draw about 100A from the 12V battery. That is a 1C load, and for a lead-acid battery the Peukert effect will make effective ...
  • 3,303
0 votes

How can I power my Raspberry Pi with red and black wires?

Your friend is right you can't just run a battery voltage into raspberry pi. Two lipo cells will be more than 7 volts when charged and will damage the raspberry pi as it's only rated for 5 volts. You ...
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0 votes

How can I power my Raspberry Pi with red and black wires?

I can't use the pins to power it since I'll be using both the 5V Are you using a display on a shield, or wiring your own connector? You can certainly wire your own 5V input in parallel. since it ...
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0 votes

How can I power my Raspberry Pi with red and black wires?

Without knowing your background and resources for a few dollars purchase a new Raspberry Pi adapter. Be sure it is capable of supplying at least 2 amps, more would be OK as the Pi is not greedy and ...
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1 vote
Accepted

PIC16F684 A/D converter problem

Your circuit is likely latching up because the battery tries to power-up the processor via RA2/AN2 input. Since the battery is a very slowly-varying DC voltage, try adding a 10k resistor in series. ...
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0 votes

If I want to add an extra DC motor to an existing 6 V system, do I replace the battery with a higher amperage?

Suggestion: What I have done in the past was to upgrade/overhaul the toy vehicle to use a 12V battery (check space - the larger, the better) while using a control for selected maximum voltage (speed) ...
  • 1,237
1 vote

Repairing a 5-cell Li-ion battery: dead 21700 cells replaced, but BMS still reporting error when charging

If one cell was completely at 0 V, it's an indication that, during use, its voltage actually became negative, as it was being charged in the reverse direction by current from the other cells. If so: 1)...
1 vote

Repairing a 5-cell Li-ion battery: dead 21700 cells replaced, but BMS still reporting error when charging

Having a 5-serial BMS, it will control the individual voltages at all 5 cell. When the voltage differences are too high the BMS will report an error. I assume the newly inserted battery will be not ...
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0 votes

Using an undersized Li-po/Li-ion charger for a large pack of 18650 cells

There is no minimum charging current for Li-ion batteries. You'll be fine. Just don't leave the charger connected for a prolonged time.
7 votes
Accepted

What is the name of this battery contact type?

The contact is proprietary to the Vruzend system, designed to work with the holder to make a secure, low-resistance contact with the battery. So this C-shaped contact is their special-sauce that, ...
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0 votes

What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?

As already noted, the current draw is likely too high for a single PP3, and multiple in parallel is "A Bad Thing"(tm) So, use a single PP9 or BAT10, both of which are rated for much higher ...
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1 vote

What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?

I find it interesting that noone has mentioned internal resistance. AA batteries have MUCH lower resistance than 9V batteries do. How will that change your circuit? Only you know. I actually burned an ...
0 votes

Battery Pack Design: Charging Parallel 18650s Through a Step Up Converter and BMS

You're overthinking it. No diodes are required. 2-cells in parallel = 1 larger cell. Make sure that the DC-DC converter is current limited (for CCCV operation) and is trimmed for 4.2 V (not 5 V) Make ...
0 votes

Connecting 3 Li-ion pouch cells in series with BMS

What you call "Lipo" are actually Li-ion cells in a pouch package. Internally, they are Li-ion cells regardless of whether they are housed in a plastic pouch or a metal cylinder. Therefore, ...
3 votes

What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?

Not answering the exact question, but if you want to improve on ugly AA cells, I would try to make the device run on a nice cheap and easy rechargeable usb power bank. There is a fair chance that it ...
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5 votes

What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?

Many 9v batteries are simply 6 AAAA batteries in series, configured that way to make it compact. This link shows the makeup of a 9v: http://dacuriousone.blogspot.com/2011/05/batteries-in-most-consumer-...
0 votes

Chaining TP4056 modules, the proper way

Your supply figure is correct, but you need to put a diode between each out+ out-. otherwise b+ in+ will be short-circuited.
5 votes

What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?

Of course, you are missing a lot. This is OK as long as you learn. Here we talk mainly about the primary (non-rechargeable) things. Why batteries are used traditionally in series: Because of the ...
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8 votes

What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?

If a product has several independent battery receptacles wired in parallel, the user will insert one exhausted battery and one fresh battery, because why not. When this happens a high current will ...
  • 65.5k
22 votes
Accepted

What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?

What would prohibit? Nothing, except you likely get less capacity with four 9V batteries in parallel than with six 1.5V batteries in series. And because connecting batteries in parallel is generally ...
  • 104k
16 votes

What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?

The other answers talk about the physics, but there's also the commercial angle to consider, you did ask for practical considerations! AA batteries are made by the gazillion. 9 V batteries have a much ...
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