The challenge of the Light Sport Battery
As I mentioned in a previous post (Regulations for LSA Owners) maintenance regs for a LSA are a bit different from Part 23 aircraft.
14 CFR 91.327 "Each alteration accomplished after the (LSA) aircraft's date of manufacture meets the applicable and current consensus standard and has been authorized by either the manufacturer or a person acceptable to the FAA"
In the case of the Battery, one must consult the CC11-100 Factory Maintenance Manual for "Authorization to Perform Maintenance, Repairs, Alterations and Inspections. Clearly the factory authorizes the pilot/owner or above to maintain and or alter the battery.
This is different from "certified" Part 23 aircraft, where batteries require TSO's or PMA's and STC's.
The original battery for the CC11-100 as shown on Cubcrafters website is a Made in China Power-Sonic PTX9-BS AGM VRLA battery rated a 8AH and 120CCA-130CCa. It is supposedly equivalent to YuasaYTX9-BS. There is no PMA or TSO. (The Power-Sonic website only claims a 90 CCA for their made in China battery! YUASA website claims 135 CCA for their US made YTX9-BS.)
In addition to the 91.327 regs for LSA, there is also an Advisory Circular 23-27 that addresses replacing/substituting parts for plane no longer in production.
https://www.faa.gov/documentlibrary/media/advisory_circular/ac_23-27.pdf
"2. BATTERIES. If one type ofseries 35 battery ( e.g. a Gill 35) is approved as original equipment or a PMA part, and another type ofseries 35 banery ( e.g. a Concord 35) is PMA approved for some aircraft models but not your model aircraft, you may install the alternate type of series 35 battery and document the installation with only a logbook entry. This applies to all series 35 batteries. This philosophy also applies to other series, such as series 25 batteries. However, this part substitution is permissible only as long as the batteries are the same weight, within plus or minus one pound, and have such similar physical characteristics as to enable the use ofthe same securing or attaching devices, mechanisms, or containers."
The O-200 Continental engine in the Cub draws 220 CCA at first crank, then stabilizes at 180 CCA for the next couple rotations, if necessary. Clearly a battery that is rated at only 90-120 CCA is marginal. Cubcrafters issued Service Instruction SI0026 that allowed major mods to the battery box and substitution with a larger 200-220 CCA battery.
After two years of service, the Power-Sonic battery would no longer crank the engine. See Battery Test data. Appears the failure was due to the electrolyte loss from evaporation and resulting sulfation. Note the very high 39.89 milliohm internal resistance.
Many years of experience with formula racing cars has taught me that for small AGM batteries, only two manufacturers produce an acceptable product--YUASA and Braille. Although Braille and YUASA both manufacture batteries in the USA, my experience is that the YUASA factory filled batteries they make in Japan are the best. (It is rumored that Braille batteries are made by East Penn aka Deka. Braille uses "different" methods of testing for specs. I have no personal experience with Braille, but they do have a good reputation in the racing community. I am reasonably convinced that YUASA has introduced an improved design and manufacturing process in their Japan factory that increases CCA over similar models produced in their other plants around the world. YUASA is by far the leader in Power Sports batteries world wide.)
The "advanced" versions of the TX9-BS battery are the YUASA YTZ10-S and the Braille B106. The difference is that CCA rating of the YUASA YTZ10-S is 190, while the Braille claims a CCA rating of 210. YUASA provides the YTZ10-S thru OEM's using the YUASA brand, and thru aftermarket battery suppliers using the Motocross brand.
With factory filled batteries, one must take care to insure they are "fresh" and/or have been "maintained" while in inventory. I ordered a YUASA YTZ10-S from a distributor and the battery they shipped was over 2 years old and had fallen to 12.03 volts. YUASA suggested that I order another as a 2 year old battery that had not been freshened while in inventory was probably sulfated. That was a correct observation. See the Battery Test data below--after I had charged the battery carefully to "revive" it. Still a good battery but not up to spec,
Here is the instructions to dealers on YUASA's website: "Check the open - circuit voltage of the batteries in your stocks every month using a digital voltmeter or a multimeter. Do not supply a battery to a customer (end-user) if the voltage is below 12.40V (6.20V for 6V batteries). Charge any batteries with voltages below these values." I do not know of any othere manufacturer that is this quality oriented regarding performance of factory filled batteries.
I searched for an aftermarket distributor who was "hands on" so that I could veriify their inventory maintenance procedures and the date code on the batteries in their stock. I ordered a new YTZ10-S from RYSZ in Connecticut after they convinced me of their expertise. https://www.ryszbattery.com/12-Volt-Motorcycle-Battery-s/1826.htm
This battery performs in terms of cranking amps (according to specs from Yuasa) very close to the large battery that Cubcrafters suggested for the highly modified battery box in SI0026.
See the Battery Test below for this "fresh" battery:
Note the 308 CCA tested and 9.7 milliohm internal resistance.
I fitted the battery box of the Cub with a tapered rubber pad under the battery to better align the battery terminals with the main wires coming thru the seat frame housing (and to provide vibration isolation) and provided a green nylon "strap handle" to help in the future to remove the batttery since it does not have a handle. Terminals have a 3/16" clearance to the composite seat frame.
The red and black wires are for the remote charging outlet (I use a Battery Tender Maintainer) that also provides an easy connection for my EarthX Jump Start battery that I carry for emergencies. The old battery until recently had always started a cold engine on the "second blade" but was never able to start a hot engine, so I always needed the EarthX for cross country flying. The EarthX is also my backup battert for my IPad (Foreflight).
The CC11-100 is equipped with an alternator that is more than adequate to recharge the starting battery, however the voltage regulator tends to run in the 14.0-14.5 V range and this can over time result in evaporation of the electrolyte on a VRLA "sealed" battery--especially if you are flying cross country. My plane is VFR daylight only, so my only battery load is the nav/com electronics and electrical instruments/gauges. (This was less of an issue when I was flying primarily "pattern practice" with a lot of taxi and glide time where the engine runs slower and the alternator is not at full output.)
I was very pleased with the Ancel BA101 Battery Tester and will use it to evaluate the battery periodically.
Cubcrafters has specifically warned/cautioned against using a Lithium battery--even the advanced LiFePo4 microproccessor protected types from EarthX. (Their concern was not only about thermal runaway risk--they were also concerned that the battery might be shutdown by the microprocessor and concerns related to the back up battery for electronic ignition. ) The weight savings for the CC11-100 would not be major (3-4 pounds) but one advantage of the LiFePo4 batteries is that they provide a higher voltage during cranking and hence a higher initial rotation speed. EarthX does make a TSO'd battery with external venting, but it is too large for the CC11-100.
With proper maintenance and monitoring, along with the EarthX Jump Start battery when needed, the original battery box, with the best quality lead acid AGM battery is probably adequate.
Testing the new YTX10-S after install provided confirmation that the battery provided the improvement desired. First start (cold) was good, as was in a subsequent start with a hot engine.
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