Any interest in a small LED "charge remaining" gauge for Li-POs?
 

I'm considering a simple new accessory. Who would find this honestly useful? Price is aimed to be under 20$.

What it is
A small (maybe 1.5" long and very thin) unit that can plug into a battery and displays on an LED gauge what the condition of the battery is. At a glance would show a visual indication of the remaining charge, and whether the pack is near, at, or below "dead" level to help people prevent dangerous overdischarge. Because unless you check, it's hard to tell how full or empty a pack is!

What it is NOT

• It is not an in-use "fuel gauge" for your gun. You plug it into the battery, look at the lights, then unplug it. You don't have it plugged in while using your gun.
• It will not stop your gun from firing when the batteries get low. It is not a switch or a fuse and does not interface with your gun in any way.
• It will not balance (or check the balancing of) the cells in your pack. Your charger should be doing that.

Intended for Li-PO packs but I might be convinced to consider Ni-MH/Ni-Cd versions too I suppose.

If you could make it work in-line under load it might be worth it. Otherwise why not just use a multi-meter?

if I was able to plug it while I'm using my gun, then yeah :)

Damn. I was hoping for a fuel gauge. Cool idea. But less useful (in my opinion) than something you can keep in your gun and periodically check over the day.

such a thing is so handy it's almost a Must Have.

I have a hobby RC one that plugs into the balancing tap of lipo's. I can measure between 2-6 cell packs. It has a 3 digit display...cycles from the V of each cell and the total pack voltage (i.e. cell 1, cell 2, cell 3, Total...cell 1, etc...). Takes just seconds to measure a pack. Cost $22 after taxes.

It's saved me grief at least once when I mixed up my partially charged and freshly charged LiPo packs in the middle of game. Worth the $20 just for that one time so I didn't have to sweat it for the rest of the day.

I check before I charge, before I plug it into the gun, maybe at lunch (again...it's really quick) and when I'm done for the day. Most times...there's nothing surprising. Once my buddy had a dead cell in a pack (so maybe having one saved him from bursting in to flames! LOL) that we found with the little meter. Another time I had a pack come in with a gun for repairs and one cell was 0.5v higher than the other two. I was able to let the owner know about that, show him, and tell him how to keep an eye on it.

Yes...a multimeter will do the same thing...but this reader is smaller than my thumb and I just toss it into my admin pouch.

It was hard to find at first...so yes, if there was one available from you at the time, I would have bought it from you.

Wow, that's a nice unit for 22$ under taxes. I don't think I could make one for that price.

On the other topic I do like the idea of an in-use fuel gauge but I always thought the whole need-to-see-the-display part was a problem. You need to see the lights and a battery is normally tucked away in an AEG... anyone got any bright ideas for that?

I say a safe 60-70% of people use a battery system which is able to be field stripped; that is, able to remove the battery without the use of tools, or few tools and little to no loose small parts.

You wouldn't need it external, just something which stays plugged into the battery, and has an on off switch so that it doesn't unnecessarily drain the battery when away from eye's view.

You remove the battery from it's shell and press the button on the meter, it tells you where you're at, and you either change the battery or put the cover back on and continue with the current one.

Sound feasible?

There are too many styles of guns for you to expect to be able to, out of the box, have the meter exposed. If the user wants to expose the meter and button to check the battery level without exposing the battery, you could provide a system which can cater to their needs (large solder points for the button... or even have it wired an inch off of the board so the user can lengthen it if they choose. Possibly have the led's protruding (or even the opposite... flush with the board to allow the user to easily create a port to view the meter through).

The other option I looked at was a setup that had a red led that the operator could position/see on their gun. The light would light when the pack went close to 9v.

Downside...you usually end up with a flickering light as the pack gets down to the lower end. It'll dip a fair bit with sustained fire. Not bad as a warning light I suppose. The other "hard" part was wiring it so you could see it. Not too bad for handguard positioned batteries...not as noticeable for stock mounted batteries. Basically extension wires with an LED that you'd stick on your gun. Very Red/Green.

Variations of that were units that chirped...but guys found that annoying as it got low and blipped below the threshold.

In the end...I decided just to periodically check them with the plug in tap. I run them in the stock and usually the tap is easily accessible.

An alternative is to have a velcro mountable unit (or trick RIS attacheable unit!) that has a long tap extension that runs into the gun to the battery. The velcro type could be mounted on the stock tube, side of receiver or on the PEQ box. The RIS type could go anywhere...even up between sights. Little black out flip cover and you're all tricked out.

Good luck! :D

http://cgi.ebay.ca/2S-6S-RC-Lipo-Bat...d=p3286.c0.m14

paid mine 6$CAD total in an auction on ebay. You can keep it plugged while you play! Show total voltage and individual cell charge.
it takes10 secondes to check or if you are really lazy you can read it through the handguard holes http://www.airsoftcanada.com/images/...on_mrgreen.gif Its probably the same as yours m102404

Heres what it looks like in a m4 handguard:

http://img525.imageshack.us/img525/403/img4816i.jpg

THAT"S THE EXACT SAME ONE...I got RIPPED OFF for $16!!!!

Hehe!

they are cheap on ebay! took 3 weeks to receive it but It was cheap!

What about an audible alarm, a little beeper maybe.

it exist

http://cgi.ebay.ca/Lipo-battery-Low-...d=p3286.c0.m14

http://renbin.zk119.cnkuai.cn/200812171600450.jpg

only problem is that its a 95db alarm... Could be a good idea to remove the speaker and solder a vibration motor!

exactly, I think you can show how much energy is left in the batts by changing the frequency or pattern (or both) of the beeper, maybe with a piezo, people learn these fast if the cues are well designed.
If you are going to use an alarm, you can just use a mosfet and cut the power to the aeg, it would be more useful than an alarm imho. What I would want would be a audible battery meter.
Of course it shouldn't beep all the time, it should have a way to trigger when you want.

i use this one...http://www.hobbycity.com/hobbycity/s...idProduct=7704 15$ and digital readout LOL... very accurate i checked it with a multimeter...

and while playing i have this plugged into my lipos... http://www.hobbycity.com/hobbycity/s...ery_Monitor_3S 4$