35
votes
Why are Alkaline, NiMH, and Li-ion AA measured differently (mAh, mWh, etc)?
It's marketing, like PMPO watts. Big numbers sell!
If the battery is 1.2V nominal, there won't be a big difference between W.h and A.h numbers.
But if the battery is 3.6V nominal, the W.h number ...
- 81.8k
19
votes
Accepted
Why are Alkaline, NiMH, and Li-ion AA measured differently (mAh, mWh, etc)?
cIt's complex, and some of the answers are "soft" and some of you assumptions are (reasonably enough) inexact.
Li-ion are measured in mWh
LiIon cells are frequently measured in mAh capacity.
LiIon ...
- 152k
13
votes
Accepted
Replacing NiMH with Li ion
Try to avoid asking "can I replace.." because sure, you can.
The real question is: Is it a good idea?
Unfortunately the answer is a solid NO.
Reasons why:
The NiMh cells are very likely high ...
- 81.4k
12
votes
What is the minimum safe voltage for NiMH batteries, if at all?
To avoid permanent damage from a single discharge cycle, a NiMH should not be discharged below 0 v. This should not be done routinely however, as it's likely to accelerate the normal wear and tear on ...
- 174k
11
votes
Accepted
Can I indefinitely "trickle" charge NiMH batteries with a constant current?
It's not clear to me if it's indicating that even this overcharging will have a noticeable negative effect on the battery (but it's worthwhile if your application needs to maintain fully charged ...
- 548
10
votes
Rechargable batteries vs alkaline
NiMH batteries have lower initial voltage and lower internal resistance.
Lower voltage won't allow the device to operate properly. Not likely since alkaline voltage decreases over the useful life. A ...
- 17.4k
9
votes
Accepted
Can I charge a NiCd battery with a NiMH charger?
The following application note from Texas Instruments on battery charging is quite relevant.
It is about some charger controller chips, but the bulk of the document is focused on how to charge NiCd, ...
7
votes
Accepted
MAX712 charging circuit - diode gets too hot
For starters: Electronics can get hot. Very hot, in fact. The diode you are using is rated to 150 degrees Celsius. I would advise you to really avoid getting anywhere near that but what I'm trying to ...
- 12.6k
7
votes
Why are Alkaline, NiMH, and Li-ion AA measured differently (mAh, mWh, etc)?
Not all loads are constant power or constant resistance or constant current or constant in any other category as the voltage drops at 20% and the double layer effects in all batteries as well as the ...
- 148k
6
votes
Why are Alkaline, NiMH, and Li-ion AA measured differently (mAh, mWh, etc)?
Alkaline battery capacity depends too much on load, it's too complex for the average consumer to understand and the difference between brands is small. Primary (non-rechargeable) lithium AA cells have ...
- 220
6
votes
Can I use a lithium charger for a bluetooth speaker with a NiMH battery?
No, you should not use a lithium charger, or any charger for that matter.
You should use what it says on the unit, a 12V DC power supply.
The charging circuitry for the battery is inside the speaker. ...
- 172k
6
votes
Voltage of AA rechargeable batteries suddenly drops
"A chain is only as strong as its weakest link"
Due to manufacturing tolerances etc., each cell will have a slightly different capacity. Whichever cell has the lowest capacity will be ...
- 57k
5
votes
Can I swap a USB power sources for a 3-AAA battery source?
My question: Is anything bad going to happen if I hook up 5V USB
power-pack in place of the (3.6V total) batteries?
The LEDs will likely fail
If I need a resister in series, how do I tell what ...
- 473k
5
votes
Accepted
Recharging NiMH cells after long period (18 months) of self discharge
I do not expect these cells to be damaged. Contrary to Lithium based cells, which are indeed damaged when fully discharged, NiMh cells can handle this as long as they are not reverse charged.
Reverse ...
- 81.4k
5
votes
MAX712 charging circuit - diode gets too hot
No, it's not getting 'too hot'. No where in the field of electronics is 'too hot' defined as 'too hot to touch.'
Electronics get hot. This is a fact of life. Data sheets generally don't tell you ...
- 29.3k
5
votes
Accepted
Buck converter without inductor in a NiMH charger (Zilog AN0259 application note)
The circuit you mentioned could be described as a pwm current source. It uses its relatively large 2 ohms current sensing resistor, as well as the resistor R3 at the base of Q1 to limit its output ...
5
votes
Accepted
Battery pack voltage keeps dropping without use
Nickel metal hydride batteries have a relatively high self discharge rate. Battery University says that they lose 10 to 15 percent of charge over the first 24 hours. That loss of charge will result ...
- 73.6k
4
votes
Accepted
What does it mean that NiMH batteries do not have a "float voltage"?
As long as the charge voltage is below whatever the "fully charged" battery voltage is, presumably you should be ok.
The problems with NiMHs is that continuous charging can lead to a build up of ...
- 3,789
4
votes
Balancing NiMh batteries in series over a long term
NiMH has pretty high self-discharge. Read: the internal isolation is probably much lower than 10 MΩ. So those won't do anything.
I don't see any problems with NiMH cells in series – and the ...
- 100k
4
votes
Accepted
Can I replace a NIMH rechargeable pack with a resistor if I only want to run plugged in?
In the spirit of fooling the battery charging circuit into thinking that it is attached to a charged battery and also getting at least a little light in the case of a power failure, you can replace ...
- 5,626
4
votes
Accepted
What is the miminum voltage for series NiMH pack?
Your sums are right, 900 mV * 8 = 7.2v.
However, what happens if the pack is unbalanced, has 7 cells at 1.0 v, and one cell at 200 mV? That measures 7.2 V at the pack terminals as well.
The cells ...
- 174k
4
votes
How can I trickle charge NiMH batteries as part of an IOT controller?
You should be able to measure the sleep mode current draw and determine where the current is going.
Always active are the L293, the LM1117 and the sleeping ESP.
None of these should be close to the ...
- 152k
4
votes
Accepted
How can I trickle charge NiMH batteries as part of an IOT controller?
You are not seeing an increase in your battery voltage for two reasons:
The solar cell is NOT providing its full current/voltage capability, so your perception of 'full sunlight' is wrong. Test your ...
- 22k
4
votes
Nickel battery balancer
The problem you obverved is very common in large stacks of Nickel batteries: Some cells get polarity inversion every cycle, and rapidly detoriate, so the whole pack dies. But the primary reason for ...
- 2,384
4
votes
Accepted
High voltage when charging NiMH battery?
Your questions:
Why do some batteries show this high voltage when charging while many others stay within acceptable ranges?
Is there something wrong with the battery?
The answer is related to ...
- 1,629
4
votes
Accepted
NiMH or Li-Ion for a 5v <1A powered device for a kid?
LiIon is dangerous ... if you:
overload it (U > 4.2V)
load it with an high current
the LiIon-cell gets hot (because of sun or an other heat source)
Use LiIon-cells, but reduce the charging ...
- 1,346
4
votes
Rechargable batteries vs alkaline
The chances of any adverse safety event are very small. The only concern is voltage compatibility. If they designed the device with a relatively high cut off voltage, then the NiMH cells may give ...
- 29.5k
4
votes
How much power do I need to charge 12 V 800 mAh NiMH battery
I lost its charger. I tried to charge the battery with another 12 1A power supply.
DO NOT attempt to charge a NiMH battery with a power supply. A NiMH charger is current limited, has a precise top ...
- 25.6k
4
votes
Accepted
Turning off a solar panel with a GPIO
For terminating the charging from a low power solar panel an easier approach is to short it out with a transistor driven from the GPIO.
Connect the bypass transistor directly to the panel before the ...
- 34.2k
3
votes
Accepted
Mosfet is getting hot in switching circuit
There are two important types of losses in a mosfet: Conduction losses and switching losses.
Conduction losses: This occurs when the mosfet is already switched on and is conducting current. You will ...
- 440
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