If you have A123/LiFe receiver packs, you WANT this mAh consumption tracker - RC Groups
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Jul 25, 2011, 08:40 AM
Magicsmoke maker
Inflexo's Avatar
Build Log

If you have A123/LiFe receiver packs, you WANT this mAh consumption tracker

STATUS: LCDs now shipped (12-Nov-2011).
STATUS: In production, awaiting LCD delivery from China.
Dispatch from China is anticipated on Nov 12, arrival by Nov 20. PCBs will already be populated on LCD arrival so SCC1 deliveries will commence almost immediately.

A sophisticated device that measures the battery capacity being drained from your receiver packs (or small park flyer power pack) and provides detailed data on the state of the power.

Perfect for A123/LiFe packs which cannot be reliably measured using the normal voltage sense alarm systems.

Download the user-manual and check out the features that it offers in detail.
  • Programmable battery size in 50mAh blocks
  • Manual reset/initialise (as with a normal car odometer)
  • Empty battery alarm (not really very loud, but it's still there)
  • Maximum of 10A sense ability
  • 1mAh consumption resolution
  • Data display:
    • Top line - Battery capacity remaining
    • Bottom line:
    • Runtime since last reset
    • Current battery voltage (V)
    • Peak current (mA)
    • Lowest averaged battery voltage (V)
    • Consumed mAh
  • Voltage range: 4.0~8.5V (2S lipo maximum)
  • Current range: 0~9,999mA (5A average max recommended)
  • Battery size: 50~12,800mAh
  • Weight: 10~12g ( ~0.4oz )
  • Size: 38 x 25 x 7mm size (1.5 x 1 x 0.25")
  • Leads: Two pairs of 20AWG bare silicon fly leads
  • Protection: Rubberised clear heatshrink

Last edited by Inflexo; Nov 11, 2011 at 09:35 PM.
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Jul 25, 2011, 08:53 AM
Registered User
SteveM732's Avatar
Surely you mean to say it'll tell you how much charge was consumed from the pack.

The newer Castle Creations ICE ESC's have a logging capability that records much of this info:
* Battery Voltage
* Battery Ripple
* Battery Current
* Controller Temperature
* Controller Input Throttle
* Controller Motor Power Output
* Motor RPM

But sadly, no record of mAh (charge) used. http://www.castlecreations.com/produ...oenix_ice.html

I don't have any of these controllers so a little $40 device like you describe would be handy.
Last edited by SteveM732; Jul 25, 2011 at 09:17 AM.
Jul 25, 2011, 09:24 AM
Magicsmoke maker
Inflexo's Avatar
This unit is more for receiver packs (NiMH/LiFe/A123/2S-lipo) on glow/glider systems, as opposed to electric power with ESCs. Maybe I can come up with a better title in the morning for the whole system to clarify its intended application.

Anyhow, attached is a preliminary spin of the board.
Jul 25, 2011, 09:36 AM
Registered User
SteveM732's Avatar
It is morning

I see, makes more sense in a fuel powered plane. In this forum I always assume electric powered unless otherwise specified. Still, I could see potential in smaller electric FF or R/C. Any idea what the max current would be?
Jul 25, 2011, 09:47 AM
Magicsmoke maker
Inflexo's Avatar
Ah, we're just about to switch over to Tuesday morning here in Australia... in T-15 minutes

I know what you mean about the electric-powered assumption, I do it a lot myself too, though less so these days since I've moved mostly over to DLG's.

Max current is able to be chosen based on the sense resistor, right now I'm going for 5A but moving to 10A isn't a problem. I only need to try keep the max voltage drop across the sense to below ~50mV (keeps the power dissipation/wastage down to a minimum).

I am looking at a similar device for full electric planes but there's a few technical hurdles I have to overcome first.

Jul 25, 2011, 11:28 AM
Perfect 3pt inverted landing!
teookie's Avatar
Good idea for a project; perfect for people flying A123 receiver packs. Good luck with it.

(I will probably pass for myself though at the $40 price point. I am notoriously cheap, however.)
Jul 25, 2011, 11:43 AM
Magicsmoke maker
Inflexo's Avatar
Pricing is always a difficult thing to get "right". Unfortunately for us sitting outside of the countries where the bulk of the components are manufactured, we get a nice setback compared to being on the inside ( really, a lot of the stuff you see at HobbyKing, even if I bought 1000 units of every part, I'd still not get below their retail price, it's enough to make you cry - so instead you have to be two steps ahead and try other aspects to sell )

I'm waiting for the LCD panels to arrive before I commit the PCB for prototyping, the main reason is that it'll be a chip-on-glass LCD and has a fixed length flexible flat (FPC/FFC) ribbon and I really do NOT want to miscalculate the size of the PCB and the respective positioning of the connector.

Jul 25, 2011, 01:40 PM
Supersonic Engineering
GordonTarling's Avatar
I use A123's for receiver packs, so am very interested in this.
Jul 25, 2011, 03:58 PM
Registered User
SteveM732's Avatar
I don't think $40 is unreasonable for a specialty product of high quality made in small quantities.
Jul 25, 2011, 08:30 PM
Magicsmoke maker
Inflexo's Avatar
Good morning all

Will be working on the project a bit more today, trying to work out where I'm going to put another couple of parts (I don't want to put them on the other side of the board, because that's where the display will be resting, best I keep it flat)
Jul 26, 2011, 09:15 PM
Magicsmoke maker
Inflexo's Avatar
Typical isn't it... when I need to get a bunch of parts and PPal is the only way to pick them up guess who doesn't have any $ in PayPal... will wait another week before getting desperate.
Jul 26, 2011, 09:33 PM
You looking at me?
Ed Franz's Avatar
I would be interested in one of these. Sounds like a great idea!

Jul 26, 2011, 09:41 PM
Magicsmoke maker
Inflexo's Avatar
Trying to decide at the moment which way I should go for detecting peak currents. Two options on the table;

1) Resettable peak-detector with a low-pass filter on the input stage
2) Calculate from firmware, measuring peak current based on the pulsecount per unit of time from the charge integrator.

The first option is nice in that it's something which looks after itself and actually doesn't really need a reset on it, however it'll be prone to pick up transient spikes 20A+ without suitable filtering on the input stage. Also being made of 2~3 opamps it'll have it's own set of calibration issues.

The second option will only however detect peaks up to the maximum permitted by the 50mV range of the integrator, so if I go with a 5A range then 5A is where it'll peak, even if the actual draw was 8A.

Aaah, the joys of design
Jul 26, 2011, 10:35 PM
Registered User
Interesting project

I think you should go for the 10A sensor if not higher. With multiple digital servos it is very easy to exceed 5A.

Keeping in mind that your primary market is monitoring Rx packs, if you use a 10A sensor then a simple peak detector that clips at 10A is probably adequate if it makes the device significantly smaller/simpler/cheaper.
If you have a 10A sensor
Jul 26, 2011, 11:26 PM
Magicsmoke maker
Inflexo's Avatar
10A isn't a problem in so far as getting a suitable part for it... the downside of going with a higher peak though is that you lose your bottom end sense range resolution, however, realistically we're aiming for worst case of 10% tolerance (eg, 1000mAh +/-100mAh), though I'm hoping we'll end up more like 2.5~5%. While the math would indicate we'll end up in the higher quality resolution I won't state it absolutely until the first prototypes are finished and tested


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