Miniature programmable voltage indicator for mods - overview

[slimest]

I always wanted to use in my power supplies a battery voltage indicator precise enough, miniature, without these stupid digital displays, only one multicolor led. Found out and purchased this thing: LED Battery level voltage monitor meter indicator Alkaline Nicad NiMh LiPo L | eBay

Today I got it from post office, tried to program and tested. Here is a small overview.
The device arrived in reliable and big bubble envelope, well packaged. I found inside the board itself with presoldered positive and negative leads, removable plastic bezel for LED mounting and complete color manual with how-to's.
This board has 8 steps to indicate voltage. If, say, range is from 3.0 to 4.5 volts, divide 1.5 volts to 8 and you get 1 step voltage. You can use this indicator in wide variety of voltages.
The manual is clear enough (remember, you have to program the device before use!), but there is annoying mistake: in the main programming table LiIon batteries are called Lead.

The main thing. Test results are a little disappointing. In LiIon mode minimal voltage is about 3.2V (it's OK), but max voltage for fully charged battery is only 3.7V! It acceptable only for LiIon cells with LiFePo chemistry, but most LiIon (LiPo) cells have this voltage 4.2V. Anyway there is an option to ovverride this problem choosing Alcaline battery during programming (rate is 3.0 - 4.5V). Not ideal solution, but better than standard mode.
Added: the problem resolved: http://www.e-cigarette-forum.com/fo...tage-indicator-mods-overview.html#post6116178
Anyway the indicator works, it's very small and nice. Good choice for miniature e-cigs. The LED can simultaneously show that power is on and indicate battery status.

Hope that this information will be useful for modders.

 

[BJ43]

Slimest, how do you program it?

 

[slimest]

Just one button on the board. Connect it to a battery, do some magic according the manual and... The board gets burned
To be serious, I managed to correctly program it after a few attempts, but nothing complicated.

P.S. Between us, this thing is also a great toy

 

[BJ43]

HobbyKing R/C Hobby Store : HXT Lipo Monitor 3S. A must have for all lipo users!

From what I can understand your unit will give me a range between the min and max voltage I want. This unit I am using works great but only gives me over 3.3 v per cell (green) and under 3.3v per cell (red) which is what I really care about. Much better price though. That said I will probably buy one just because it is a cool toy.. lol

 

[slimest]

This small device does not have a datasheet, but seems that it just says: hey, you battery is off!!!
I prefer to know my battery status before this hey
Another thing: if you insert this board to a cigarette body, you have to consider its position to wach indicator conveniently. The described board is more friendly - just desolder or cut the led, use a thin wires and position the board and led as you wish.
About price - yes, this board is expensive enough. And very smart.

Anyway thanks for the link. This small board coul be useful in simple 2S systems if you want to simply control critical batteries status.

 

[asdaq]

Slimest, so the switch is just for programming or does it need to be pressed to take a reading? If just for programming it could be snipped off after being set and in an emergency the pins could be shorted to re-program. This could save some extra space.

 

[slimest]

asdaq, the button needed only when you program the board. You are right: if you want use this indicator for life only in one mode, the button can be desoldered. And if you after time want to reprogram it again, no problem to resolder a button again, it's easy.

 

[asdaq]

I see what you did there.

 

[jhonutz]

seems to be not good for what you want and it`s kind expensive for what that PCB can do.
And about LiPoFe4 try to forget

 

[slimest]

Haha! I told to developer, and he suggested quick solution: to shunt one resistor in divider which determines reference voltage for controller. So I soldered 68 K resistor between legs 7 and 8.
Now steady green on 4.20 V, green flashes slowly if voltage decreases to about 4.1 V, steady red appears at about 3.6 V, red flashes fast if voltage decreased to about 3.4 V
Practically ideal for IMR cells (they don't like to be discharged less than 3.5 V).

 

[breaktru]

Very nice write up slimest. Good info. Thanks Comrade.

 

[slimest]

breaktru, thanks.
Developer knows about this topic, I hope that he modifies firmware, so we will get an universal voltmeter even for rough charge testing. And I just imagine: what if use the same concept but with fixed mode: 3.4 - 4.2 volts... No button, no awkward regulator, much more compact and cheaper device

 

[slimest]

I desoldered one leg of the button, so we can see what components used in this board.
1. Black 3-legs thing seems to be LM2950, voltage regulator. It is needed because voltages range for the board is wide enough (I guess, it also supports reference)
2. The main chip is Microchip 12F683. Datasheet: http://ww1.microchip.com/downloads/en/devicedoc/41211d_.pdf