Originally Posted by _cy_
Using Heated Gear with LiFePO4 batteries
heated gear don't understand PB/EQ. they draw real amps. Almost all LiFePO4 battery mfg like to use amp equivalents to lead acid batteries. that may be valid for starting requirements. but heated gear don't care... they draw regular amps.
listed amp/watts for Gerbings micro wire. even if you don't have Gerbings, amp draw will be real close. amp x volt = watts
1. Jacket 6.4 amp/77watts
2. Vest 4.5 amp/54watts
3. Pants 3.6 amp/44watts
4. Gloves 2.2 amp/27watts
5. Grips 3.0 amp/36watts
let's say you've got a heated jacket, heated gloves and heated grips = 11.6amp draw
let's say your LiFePO4 battery has an actual Amp Hour capacity of 6 amp hour. this means your battery will support your heated gear for about 1/2 hour before going dead.
then let's factor in alternator output and amp draw from rest of bike. on short rides using heated gear, it's quite possible to use more amps from your battery than Alternator has a chance to replenish.
when you put your bike away for the night after that short cold ride. your 6 amp hour battery may not be fully charged.
next morning it's say 30f degrees ... you go to start your bike with a half dead battery.... fail ... one automatically blames the battery. when the fault is putting bike away with a half charged battery.
this is where LiFePO4 batteries with BIG reserve capacities shine. Lithium batteries internal resistance goes way up with battery gets cold. this means substantially less amps will be delivered. cold start procedures calls for a load to be placed on LiFePO4 battery. this heats up battery reducing internal resistance, allowing more amps to be delivered.
ahhhh... but there is a catch... heating a cold LiFePO4 battery takes amps... battery must have enough reserve capacity to heat battery up and start your motorcycle.
clear as mud... nah.. it's not that hard to understand. Adventure bikes must have some of the hardest demands on a battery. if you've got a R1200GS and you are planing on climbing the Andes mountains and camping out.
go with an AGM or if saving 10lb+ is worth the trouble... go with largest LiFePO4 motorcycle battery available.
Shorai LFX36 next to Earth-X ETX36C
Amazing the EarthX battery is much smaller than the Shorai, but then the Shorai's can have a lot of airspace above the flat-packs and the case is sized more for the expected application.
As for running heated gear, GPS , heated grips etc, as long as you don't draw more than your alternator puts out, your battery will stay charged just fine. A small panel voltmeter is all you need to tell that. If it drops below 13V or so your charging system/alternator is not keeping up with the loads on the bike, and starts to draw on the battery. If you were to ride a long way in this configuration, your battery would eventually die.
I size my loads on the bike I'm riding to always leave some overhead watts so the alternator can keep up. I don't count on any kind of battery to run my heated gear directly since they will all run down quick.
Even my Husaberg FE390 dirtbike has 200Watts out and running a Gerbings heated jacket liner, heated grips, the EFI system, GPS and my 44Watt LED headlight, I have 80+ watts left over and my alternator on that bike easily keeps the Shorai in it as fully charged as it can be. I would think BMW's have even larger alternators.
My KTM 990 (~450watts) has even more power out and has no problem keeping any battery on the bike fully charged along with EFI, heated gear, HID lights, navigation, etc. even on short rides. If you are managing your loads properly, you should basically never be drawing from your battery while the engine is running.