ORIGINAL: A.T.
ORIGINAL: chewytm But nothing for 2S A123 batts at 6.6V? I think A123 batts are quite common nowadays as they don't require regulators with most 6V capable servos. Will anything be done about that? chewy
Unfortunately there are to many different types of cells refered to as A123 with different voltages and cut offs which is why it is hard to find good chargers and few if any on board voltage displays.
I believe the engineers are trying to work on an answer but it could be a while.
Just two examples of cut off / loaded voltage measurement problems,regarding A123,availableon the net:
A123 Battery FAQ for Giant Scale and IMAC
"Here’s the biggest issue.. load testing. The beasties just don’t react like we expect.. a 1 amp load for 10 seconds will convince somebody not familiar with them that there’s something wrong with the load tester.. the needle won’t sag! I’ve even had guys start melting switch ports and connector housings trying to get enough load on the pack to use an ESV in the tried and true sense. Just doesn’t work. Because of the incredibly flat discharge curve and the ability of the cell to hold voltage while doing 'heavy lifting', using a standing voltage level under load to decide when to recharge can lead to a disaster
because when the cells go flat they do so remarkably fast. So, we go to the next question.."
A123 battery Information - SinCity Jets.
"The
battery's only downside is that you can not tell how much energy is left in the pack by reading the voltage. Because the discharge curve of the pack is so flat, the voltage will be almost the same throught its cycle, and then "cliff dive" at the end of its cycle. Because of this, it is important to become familiar with how much energy your vehicle uses during each use. For planes, I advise people to fully charge their batteries and then fly 2-3 flights. Then, fully charge the packs again and see how much energy (Mah) you put back in to the packs. Then simply divide the amount of energy by the number of flights and come up with your average Mah per flight. This will allow you to set your safe cut-off. It is advisable to only use 1800-2000 of the pack's 2300 Mah's. " Regards Alan T.
Alan's Hobby, Model & RC FAQ Web Links
Update 18 Aug 2010:
Following recent upgrade ofAurorato V1.07 and Spectra pro Module to V2.0, user is now able to set voltage alert levels.
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<font size="2" face="">(View Version 1.07 Manual Addendum)</font> page 5 refers
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Current related discussion
elsewhere regarding Eneloop cells.and benefit of battery voltage telemetry.
<span style="font-size: smaller"> "Quote: Originally Posted by
MikeMayberry - but take this situation for example: a guy was flying with a 5 cell 2000mah Eneloop RX pack that cycled easily to 2000 mah with a 1A load and worked fine in a sport application for over a year, but when that same pack was used in a larger application with multiple digital servos it fell flat on it's face and the low voltage warning would kick it under normal maneuvers.</span><div id="post_message_15820833"><div style="margin: 5px 20px 20px"><div class="smallfont" style="margin-bottom: 2px">Of course if he had made a proper battery selection in the first place then everything else is moot.
The Eneloop cells are fine in transmitters and low load airborne use. But their high internal impedance makes them unsuitable for any kind of potentially high load use. Under load these cells have a large voltage depression due to the high internal impedance.
You do not need telemetry to tell you that - Silent-AV8R "</div></div></div>
Response - Mike Mayberry
" Agreed that these batteries were the wrong tool for the job, but in this case the user was unaware that they were not suitable and luckily landed when the low battery warning went off, most likely saving the airplane. A loaded volt meter even at 2A (equivalent of one digital servo) would not have made a difference here as the load would not have been high enough to sag the voltage. Flight loads vary with the servos in use, but if you consider that a high power digital servo working hard can easily pull 2A each (or more) then the only accurate way to see how the battery handle the actual flight conditions is with telemetry.
Yes, most of you know what you're doing but so many R/Cers out there have no idea about how the flight loads can affect the battery voltage; this goes for BEC's used in Electronic Speed Controls which which with the higher voltage threshold of 2.4 is the culprit for so many brownout crashes. What percentage of pilots use a loaded volt meter every time they fly? Not many. How many with telemetry check their battery every time they fly? 100%
Sorry, I know this thread, as many others do, has morphed into a battery discussion but to say that telemetry is no replacement for a good voltmeter which most don't use, or that you don't need it to tell you that your batteries can't handle the loads because you should have already know this is not realistic. It may be easy for some of you to justify that you don't need it, but it opened up a whole new understanding for me as to actually what's going on with batteries and BEC's in flight that I never really knew, and I consider myself and expert too! It's not a novilty... it's a tool, and I would think that all radio manufacturers will have to encorporate it into their systems sooner or later just like 2.4ghz. . Mike. "
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Aurora A9, Spectra Pro & Optima - FAQ & Undocumented Features - Mixes, Setups, Tips. {Individual Links often updated}
</span><span style="font-size: x-small">Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links</span>