A simple battery meter for mods.

[robby]

 

I got some vapemail today which included a couple of cheap voltage displays. I was looking to make something that I could quickly and easily keep an eye on my mod batteries. So after a while pondering how to use it I thought about using an old Vivi Nova which had been leaking and was getting on a bit, so I decided to try and fit the display chip inside the Nova tube where it would be permanently connected to the bottom of the Nova and unlikely to have any bad connection issues. As we all know, not all Novas are created equally lol. Luckily this had the fattest tube to fit the display into. 
First step was to strip the Nova down until only the base and the actual centre post were left. It was obvious that the display was still to big to fit inside the tube and that the centre post would have to be shortened.
  So it was out with the Dremel lol. The four corners of the display would have to be reduced for a start. You need a lot of care doing this. The circuit are exposed and it would have been very easy to take of too much plastic and printed circuit board. I went as far as I dared with the display but it still wasnt enough. It was so close to fitting. The only thing left was to take some plastic off the inside of the tube without cracking it or making it too weak. I think I took off about 2mm off the inside of the juice tube. Then it was a GOOD fit, not too lose and not too tight a fit. Taking a kind of groove out of the inside off the tube also meant that the display would not turn in the tube which was a plus.



 Pushed the display into the tube and bottom of the Nova combined and it became clear that the centre post was too high.  I took the centre post out and decided to cut it after the display was in it`s final position. This would help with stopping the centre post moving further inside the Nova tube, possibly causing connection issues.

When I looked at the display I first thought that it would need some sort of voltage supple to make it work, but when I tried various batteries of various voltage levels it became clear that it wasnt necessary. The Display has only two wires, one going to the centre post and one going to earth. 




Most of the centre post had to be cut off, dont ya just love the Dremel ;-)

The display was quite nicely jammed in the tube at this stage, so I push the centre post up until it jammed against the display and measured how much I would need to cut off it which I then did. The centre post turned out to be a tube which was good. I had been wondering how I was going to solder the red wire to the centre post and then screw the tube and bottom of the Nova, having to use three or four rotations which could have caused problems. I stripped a lot of the insulation and twisted the stranded wire.. Then fed it through the tube and tightened up the bottom of the Nova. The wire didn`t twist which was great. Then soldered the wire at the bottom of the centre post with a little solder. Then screwed the top on and tried it out, worked great, tested the voltages of various batteries and cross checked them with my multimeter, just about identical. Perfectly visible at 3.2 volts and below. 

  The display chip will show voltage between 3 and 30 volts. It can be used on all sorts of batteries and mods because of the connector on the Nova, including the basic lookalikes that we all fell for wnen we started. The only difference is you have to blow gently at the LED end to activate the automatic switch. 

The display chip is available with green, blue or red displays. 

A possible further extension of this could be to take it a bit further and somehow fit a connector to the top of the Nova so you could see how the battery was performing under load, But overall I am pleased with it.

The bits
the display ................................. www.fasttech.com/products/1222900  .............£2
the Nova..................................... your junkbox lol

[Deleted]

genius mate ... you could pick up a 510 connector for 3 quid or so and dremel the drip tip hole out for it to fit to do the in-line measurement ... how would you wire that ?

[robby]

Mar 20, 2013 21:40:48 GMT @ashmal said:

genius mate ... you could pick up a 510 connector for 3 quid or so and dremel the drip tip hole out for it to fit to do the in-line measurement ... how would you wire that ?

There is a little space behind the display to feed a couple of wires through to a top atty connector, where`s me Dremel lolol You would just connect it straight to where the red and black wires go now, because you would be wanting to see the effect of the atty on the battery voltage.

[Deleted]

Mar 20, 2013 21:43:20 GMT robby said:

Mar 20, 2013 21:40:48 GMT @ashmal said:

genius mate ... you could pick up a 510 connector for 3 quid or so and dremel the drip tip hole out for it to fit to do the in-line measurement ... how would you wire that ?

There is a little space behind the display to feed a couple of wires through to a top atty connector, where`s me Dremel lolol You would just connect it straight to where the red and black wires go now, because you would be wanting to see the effect of the atty on the battery voltage.

right so 510 connector wires soldered on top of the wires you have already connected ?

[robby]

Yes Then you could look at the reading with no atty on and then put the atty on. You can often spot a "tired" old battery like that if the voltage drop is much.

[Deleted]

Mar 20, 2013 21:51:41 GMT robby said:

Yes Then you could look at the reading with no atty on and then put the atty on. You can often spot a "tired" old battery like that if the voltage drop is much.

yeah yeah ... been wanting to build one for ages but never came up with what to house one in ... all the time it was staring me in the face ....

[robby]

Mar 20, 2013 21:56:25 GMT @ashmal said:

Mar 20, 2013 21:51:41 GMT robby said:

Yes Then you could look at the reading with no atty on and then put the atty on. You can often spot a "tired" old battery like that if the voltage drop is much.

yeah yeah ... been wanting to build one for ages but never came up with what to house one in ... all the time it was staring me in the face ....

I was the same lol, the display is only £2 as well, that is all you need really and a clapped out Nova

[Deleted]

$20 for a voltage tester, 20ml of juice and 2x18650 pannies ... what a great site ... including shipping ... suppose it would be too much to ask for a discount code ...

[robby]

Be careful, once you get on that site, you just cant leave it lol

[Greigster]

You are a clever and inspirational man Robby, a real asset to our forum.
Well done Mate

[robby]

Thanks mate, appreciate it  just wish I could blow smoke rings like you lolol

[Greigster]

Mar 20, 2013 22:02:44 GMT robby said:

Thanks mate, appreciate it  just wish I could blow smoke rings like you lolol

yea but that was 49 years ago

[NickIcon]

Fantastic! Will be ordering a couple of those displays as soon as I've had a chance to make sure there's nothing else on that site that I can't possibly live without...

Also - why do you have a drip tip in the Nova in your first photo? :-)

[robby]

Just left the drip tip there, looks a bit sad without it lol, and I kept trying to suck the darn thing. You wanna be careful on that site, I have been stuck there for days sometimes lol

[piper1]

Nice one robby