Originally Posted by _cy_
keep in mind we are talking about an adventure bike ... and we all know that nothing ever goes wrong in the middle of nowhere
sure would be nice to be able to crank that heavy pig of a bike over .. and over and over .... clearing that bad load of fuel out, etc.
don't know about you, but I'd want that extra amp hour capacity to deliver that reserve cranking with me.
another factor to keep in mind is LiFePO4 batteries operate on a different voltage scale as lead acid. think in terms of pressure in a pipe... meaning charging voltage has to be higher than resting voltage of battery to push a charge into battery.
depending on charge state of your battery, 13v my not be enough to charge your LiFePO4 battery back up to full.
I was just tossing out a voltage higher than 12V as an example for a voltmeter. Actual charging minimum voltage needed depends upon the battery type as you pointed out. My running engine voltages on 2 bikes generally run 14+ V and have so far been enough even on short rides to replace the energy used up from starting.
Of course we would all want the maximum capacity battery for the unexpected. However unless EarthX, for example, is being untruthful about their AmpHour capacity within the stated environmental envelope, then it should be the equivalent of the lead/acid it replaced. If that's not the case we will find out.
In the EarthX case the 'correct' battery for my bike is the 18Ah. The 24Ah and 36aH all fit in the same "C" case as the 18aH. The 18aH is $209, the 36aH is $339. If I was going super remote, and didn't trust the battery manufacturer I would get the biggest LiFe I could (or get an AGM), but in general why spend the bucks if the proper size works at least as well as the lead/acid it replaces.
I do and have taken my adventure bikes very remote and extreme temperatures at times over the last 40+ years of riding and so far so good. Never been stranded by a bad battery yet, not even a Shorai.