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Old 02-25-2012, 07:00 AM   #102
_cy_ OP
Beastly Adventurer
Joined: Sep 2011
Location: Tulsa, Oklahoma
Oddometer: 5,032
@Joel .. thanks for dropping in .. looks like I'm not the only Fluke junkie

power may be king, but at what temperature? so far I'm getting losses of 50% when battery along with bike is subjected to 15f degrees. then factor in additional current draw when engine/oils are cold. then factor in need to learn a completely different starting procedure, IE necessity of waking up battery before placing starting loads.

there's definitely an education process to successfully learn how to use li-ion batteries when starting a motorcycle in cold conditions. this goes for even advanced techs too. NO one knows it all... especially when treading brand new territory.

for cold starts, Amp Hour rating plays a very important role. Waking up li-ion batteries with current flow uses amps pure and simple. for cold starts Lithium iron phosphate battery must contain enough reserve to power warm up phase. then contain enough power to put out 200amps for several discharge cycles.

a four cell A123 li-ion battery like SCYL 2.3 AH will probably start a car or a Harley Shovelhead (fixin to find out). All li-ion cells are capable of putting out HUGE power for short durations. this is due to very low internal resistance.

reason for disclosing details of testing gear ... data generated is lab grade using traceable standards. Discharge tests are only an indicator of performance. Real world test like what's being laid out is what counts.

overcharge and under-discharge protection circuits have been around for quite sometime. ALL portable devices containing multiple li-ion cells should contain protection circuits. Laptops were the power user for li-ion cells for quite sometime. a power management system was mandatory. even then fires/explosions started hitting the news. Sony and Apple both had their share of devices with li-ion cells go into thermal runaway... resulting in fires/explosions. naturally they were among the first to made the switch to lithium iron phosphate. too much liability not to.

in it's simplest form, protected lithium cobalt cylindrical cells have been around for 5+ years. I was part of the original group buy by JS Burley on Candlepower forums for the world's first protected cell. He mortgaged his house to pay for initial tooling, then Chinese companies took resulting technology and ran with it. JS Burley got nothing .. his investment spawned an entirely new category of consumer li-ion cells.

here's a 18650 lithium cobalt protected cell ... over and under charge protection with an estimated 10% self discharge per month

if you will note during first phase of testing ... balance/over discharge circuits was used on the 20 AH battery. they were later removed due to circuit boards/shunts scrubbing off 10% of charge. most bare li-ion cells will have about 1% self discharge per month. add protection circuits and that no longer is true. depending on circuits. there could be 10% per month self charge due to protection circuits.

here's a pic of balance/over charge protection circuits in action. red led light when shunting off excess current.


had a brain fart and didn't leave G/S outside last night. lately spring like weather, first cold that actually arrived... 27f for a low. overslept, wheeled G/S outside at 6:45am .. waited until 8:15am .. had to start tests, temp raising fast.

33f degree, 13.51v resting voltage... 10 seconds lights & heated grip on... choke off ... first crank 124amp for 5 seconds. engine spins over fast. would have easily started if choke was set.

two more 5-6 second cranks nets 164amp draws. starter cranking engine over strong. battery drops to 12.59v after first sets of cranking

battery is allowed 3-4 minutes rest ... voltage raise to 13.18v .. battery case temp raises to 39f
choke is turned on, motor cranks strong and fires right up. amp spiked up too quick to get a good read. about 155amp for a fraction second.

after motor runs for about a minute ... turned off and cranked again... current draw drops to 68amp, motor starts quickly.... cold start tests are over for now. Forecast is 30f tonight. will leave G/S outside. above test is estimated to be equal to 40f degree starts. since bike didn't have time to fully get down to 33f internally.


9am .. 44f .. battery has recovered to 13.26 or 80% capacity remains ... amp draw spikes to 118am, then goes down to 98amp. engine cranks over strong and fires right up.

at 13.26v recovered resting voltage... this means first sets of crank cycles used about 20% of Shorai 18AH capacity. Very impressive performance from Shorai so far... but we still have not done a valid cold start test yet.

battery drops to 12.59v after first sets of cranking

battery raises to 13.18 after 3-4 minutes rest, batt temp is now 39f

9am .. 44f .. battery has recovered to 13.26 or 80% capacity remains ... amp draw spikes to 118am, then goes down to 98amp. engine cranks over strong and fires right up

_cy_ screwed with this post 02-26-2012 at 08:21 AM
_cy_ is online now   Reply With Quote