43
votes
Accepted
18650 Cell (8800 mAh) accepts only 300 mAh on recharge
There's no such thing as 8800mAh 18650 cell. The highest capacity available is around 3600mAh. Thus your cell is fake.
Image source: YouTube video - C'sB Channel "Fake 18650 China batteries ...
- 81.6k
14
votes
18650 Cell (8800 mAh) accepts only 300 mAh on recharge
Throw this fake cell away and buy a new one from a reputable supplier. Look for capacities in the range 2,000-3,000 mAh, which is what is physically possible to achieve with current LiIon battery ...
- 1,633
9
votes
Accepted
Voltage divider with MOSFET to save power
No, it is not right. There are so many mistakes lets just start over.
I believe the circuit you're looking for is this:
simulate this circuit – Schematic created using CircuitLab
M1 is a PFET. ...
- 7,636
6
votes
Accepted
Charging two 18650 cells connected in series?
Battery cell re-charge must be carefully managed, each cell must receive the correct current (amps) and total charge (couloumbs, or amp-hours) to prevent any damage to the cell. When a string of ...
- 5,865
5
votes
18650 cell will use ______ amps every _____mins?
The ampere is a measure of flow of charge per unit time. Talking in terms of "amps every x minutes" does not make sense.
From reading online sources, understand 3600mAh is 3600mA per hour ...
- 180k
5
votes
Charging two 18650 cells connected in series?
You bascially have two options to do that:
Use isolated supplies for each charging IC:
In the other question you linked to all the TP4056 modules used the same supply. This means that the outputs are ...
- 9,749
4
votes
What is the name of this connector and where can I find it?
That looks like a JST SFKR-02V-S
https://www.jst-mfg.com/product/pdf/eng/eSFK.pdf
The MKS-L crimper costs $1000+ but Digikey carries pre-crimped jumpers with a contact at each end for less than $1 ...
- 23.1k
4
votes
18650 Cell (8800 mAh) accepts only 300 mAh on recharge
As several have responded, this is a fake cell. The small print says 3.7V at 11.8Wh = 3200 mAh, which sounds reasonable. So @Ale..chenski estimate was right. He also confirmed my suspicion that a ...
- 233
4
votes
Voltage divider with MOSFET to save power
Realistically you don't need to go this complex for a 18650 battery. Their self-discharge is about 50 µA. If your sleep current is significantly below this, it has little effect on the battery life.
...
- 9,656
3
votes
Repopulating a Dewalt battery, cell choices
Winny's comment is absolutely correct.
Replacing a single cell it makes only sense, if the battery pack has only seen a few use cycles and broke early.
Otherwise it is better to replace all cells with ...
- 1,011
3
votes
Protecting parallel 18650 cells
For just two 18650 cells in parallel, fuses are not required.
Measure the voltage of the two cells, to make sure they are the same
Connect the two cell directly and permanently in parallel
Use a BMS ...
- 25.5k
3
votes
Is this a good way to make 2S 18650 battery cell while parallel charging?
No, that's not a good way, you have just shorted the batteries together through the charging modules.
- 172k
2
votes
I just built an 18650 battery. I need to know if I can use this power adapter/charger for this BMS
Power supply ripple is not your problem here. The BMS should never see the power supply directly; there should be a Li-ion charger inbetween.
A BMS is not a charger; you need a proper Li-ion charger ...
- 9,310
2
votes
Accepted
Are loose 18650 batteries safe?
18650 batteries are lithium-based. All lithium-based batteries are dangerous to varying degrees.
Lithium batteries which are shorted, punctured, overheated, compressed or a number of other conditions ...
- 2,184
2
votes
Are loose 18650 batteries safe?
No. Quoting the United States Consumer Product Safety Commission:
Once shorted, loose cells can overheat ... resulting in fires, explosions, serious injuries and even death. [1]
While they might be ...
- 165
2
votes
Reverse voltage protection for four 18650 cells
It depends on which fault you want to protect and what you want to protect. I would say option 1 is probably good enough for what you have in mind.
Option 2 is not a good solution no matter what since ...
- 1,840
2
votes
Is this a good way to make 2S 18650 battery cell while parallel charging?
Your second approach is smashing a square peg in a round hole:
The DC-DC converters are a solution to a bad approach
The cells and the charger/protection boards will be damaged whenever one of the ...
- 25.5k
2
votes
Is this a good way to make 2S 18650 battery cell while parallel charging?
This will not work in the general case.
The charger board, however it looks like, is in fact a short between the two of its terminals (usually the negative ones) and a variable resistance between the ...
- 9,686
2
votes
How to get a stable 3.3V/2A output out of a single cell (18650 Li-ion) battery?
I'd look at something like the TPS63805 non-inverting buck-boost from TI.
It's fairly simple to use:
It produces 3.3 V out over your entire input range, and the efficiency is pretty high:
I don't ...
- 24.7k
2
votes
Accepted
Is my 4s2p pack connections correct?
I think the connections are correct.
But the calculations are not.
You have eight 3Ah batteries. Connected like that, it certainly does not make a 24 Ah battery, but a 6 Ah battery.
That's because you ...
- 172k
2
votes
Is a TP5100 module redundant with "protected button top" 18650 cells?
The protected 18650 batteries protect themselves but will slowly go out of balance.
Instead, the unprotected 18650 cells, plus a 2S BMS, will be protected and kept in balance, so that's a better ...
- 25.5k
2
votes
Charging 18650 Li-ion battery with dynamo
You will need three devices:
A Step-up / step down converter to convert the highly variable voltage from the dynamo to a constant voltage
A Li-ion charger to limit the current and regulate the ...
- 25.5k
2
votes
Resistance vs Capacity in Building a Power Bank
In principle, you want the currents between paralleled cells to be matched, so you want matched resistance across each parallel section.
In principle, you want each series block to have the same ...
- 174k
1
vote
Can I charge my 3S2P 18650 battery (12.6v) with a normal 12v power adapter if I use a BMS with built-in balancing+protection?
My suggestion is you get a proper battery charger from a reputable source. It is absurd to by something as critical as a Li-Ion battery charger from Aliexpress. A proper battery charger is the ...
- 5,352
1
vote
18650 cell will use ______ amps every _____mins?
If I decide to use five 18650 cells in series, 3600 mAh @ 0.2C discharge for one BQ77915 device, is this 3.6 A * 5 = 18 A every 12 mins?
3600 mAh is not a current, but a capacity. It means a battery ...
- 9,310
1
vote
When I test a 18650 Li-ion cell, why do I get two different values of capacity for charging and discharging?
It is possible that a Li-ion cell takes in more charge during a full charge than it gives during a full discharge.
The ratio of the two values is called the "Coulombic Efficiency" (Or ...
- 25.5k
1
vote
Accepted
Can I draw power from one cell while charging 5 in series?
That's an exceptionally bad idea: You charge one battery less than the others / discharge one battery more than the others, so that you would be overcharging the rest.
Don't do it.
- 100k
1
vote
TP 4056 + XL6009 for RC cars
The XL6009 is not suitable to boost the voltage from a Li-ion battery. The nominal voltage of a 18650 is 3.6V, but it can be higher or lower than that depending on the charge of the battery. See this ...
- 7,858
1
vote
18650 parallel power bank cooks the furthest batteries
If the batteries were not balanced before blindly shorting them in parallel, a huge unlimited charging or discharging current would flow.
There likely is nothing wrong in the powerbank itself, or the ...
- 172k
1
vote
S8550 reducing current
Use the enable pin of the LM2596S to turn on your 1.2 V output when solar is low.
Please note that this is not a complete schematic but rather more of a glorified block diagram.
Resistor divider R3/R4 ...
- 16.8k
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