MilliAmp Monitor/Analyzer
(MAMA)
FUEL GAUGE for A123 RX packs
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Monitor A123 receiver pack capacity:
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* Keeps track of current in/out of pack
* Compatible with all 2-cell A123 (LiFePO4) packs
* Visual indication of remaining capacity
* Remote indicator (option) can be located for easy viewing
* Low-throttle blips (option) to warn of low remaining capacity
* Handles up to 10 amps continuous, 25 amps peak
* No need to unplug, can remain connected for several months
* Automatically adjusts to pack capacity
* Keeps track of partial charging
* Draws 5 ma. with receiver on, less than 100 ua. idle
* 2.05" x 1.10", 12 grams (less optional 16-gauge wires)
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Two-cell A123 (LiFePO4) receiver packs are superior replacements for 5-cell Ni* receiver packs, offering lower resistance and lighter weight.
A123 cells employ a different chemistry that is much safer than LiPo cells.
They also have a flatter discharge curve than either Ni* or LiPo.
While this is a performance advantage, the flat discharge curve makes monitoring remaining capacity difficult with traditional voltage techniques.
MAMA has been designed to continuously monitor pack discharge and charge current and provide a visual "fuel gauge" of percentage of capacity remaining.
MAMA is simply inserted between the pack and receiver as shown below.
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MAMA can be permanently mounted to or near the receiver pack.
It automatically goes into a low-power mode when the pack is not charging or discharging
so that it can be connected for several months without discharging the pack.
An optional remote LED can be mounted on the plane to monitor capacity without accessing the MAMA board.
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MAMA keeps track of milliamp-hours of charge and discharge and displays remaining capacity as a sequence of red and green blinks.
This sequence is intuitive and divides capacity into ten segments.
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MAMA is self-calibrating.
Performing a charge-discharge cycle on your charger defines full capacity.
Periodic cycles will adapt MAMA to any long-term decrease in pack capacity.
It can be used with any size Lithium Iron Phosphate cells, including parallelled cells.
It will work with the small "1100" cells, the standard "2300" cells, or parallel packs, e.g. 2S2P.
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As further protection, MAMA offers an optional throttle alert.
When your pack is in the last 30% of capacity,
MAMA will blip the throttle low periodically to alert the pilot to land immediately.
MAMA is simply inserted between the receiver and the throttle servo or speed control.
It can be programmed for 1- or 2-millisecond low throttle.
Blips do not go to full low to avoid 'killing" the engine.
Blips are noticeable but will allow safe control of the aircraft.
MAMA also monitors pack voltage to warn of a premature empty condition.
This emergency condition causes MAMA to cut the throttle.
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INPUT/OUTPUT:
The standard input allows connection of one or two Futaba- or JR-type connectors plus a balance connector,
either 0V-3V-6V or 0V-6V-3V.
Output is a JR-type connector with 20-gauge wire, plus a balance connector.
To cut down on the proliferation of options, the balance connector is 0V-3V-6V.
This can easily be changed by swapping two pins.
The optional input/output is 16-gauge high-strand-count wire.
This is a good choice for planes drawing heavy loads (>5 amps).
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THROTTLE ALERT:
This option provides an immediate warning when your pack starts to get low.
It supplements the LED indicator in that it provides an IMMEDIATE warning.
The throttle blips are short enough as to not cause a significant loss of power.
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REMOTE LED:
This option allows you to see the LED indicator more easily.
In many installations, the blinking colors can easily be seen in the dark fuselage, even without direct line-of-sight.
If your pack is really buried, you probably want this option.
The connector is compatible with standard servo extention cables, so it can be mounted several inches from MAMA.
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MAMA starts at $32.95 including US shipping.
You can configure your unit and compute cost below:
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