Greg Covey
Posts: 4375
Joined: 5/24/2003
From: Rochester,
NY, USA
Status: offline
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Chad,
You are correct. We gained valuable information from several pattern flyers during the beta development phase of Skyvolt last Fall and have not deployed new product to them as we await new packs from Kokam using 4800mAh cells that can deliver 100amps of current. The wait should only be a few weeks now. A 2p configuration of 3200 cells would work but is too heavy and costly for most users.
What we learned from our pattern test flyers is that the real world usage of Lithium packs cannot easily be duplicated in the lab. For example, just before production release of the BalancePro HD (formerly Skyvolt) line, we removed the air gap between the cells as it drastically reduced the cycle life due to warping from the spacers. The real world handling of these packs revealed the effect of capacity loss from our measurements. The difference in internal cell temperature was only 10 degrees F so it wasn't as effective as we originally hoped for. We had a chuckle as the PolyQuest packs soon came out with air gaps shortly afterwords as we had been advertising our packs this way as a feature.
We have improved the Discharge Protection Module (DPM) software and the 6s charger software (both products are re-programmable) in areas that affect both cycle life of the packs, usage, and speed of charging. A 20 minute full charge is now seen instead of only 90%. We lowered the full charge voltage by 0.05v and disable the low voltage cutoff for the first 30 seconds of flight.
The 3200mAh cell just didn't cut it in the F3A world. Most top pilots including QuiQue use a 5AH capacity. Unlike the ThunderPower 5AH packs, the new Kokam 4.8AH packs using the BalancePro HD charger and DPM will stand up to the current demand. What we found is that top sponsored pilots didn't care about pack longevity as they got their equipment for free. This was not the case for the majority competition pattern flyer and they often could not afford the expense of replacing Lithium packs several times a season.
The two areas of pack longevity that the user must still control are temperature and discharge current. For temperature, we provide an indicator on the pack that helps you determine if your air flow is sufficient. Since Kokam cells produce less heat during discharge, this helps the performance. The 3200 cells could only deliver 64amps which was just shy of the pattern planes power demands. The new 4800 cells are the same width but longer and thicker and they can deliver 100amps and stay under the 140 degree F threshold of damage. The new Cell Rating Specs show the true operating current for maximum longevity so the advanced user can seperate reality from advertising hype...at least on packs from FMA.
I'll be off at the GP E-Fest until Tuesday and check back then...
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