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Old 05-30-2013, 04:56 AM   #330
Beastly Adventurer
Joined: Sep 2011
Location: Tulsa, Oklahoma
Oddometer: 6,334
Originally Posted by RexBuck View Post
Thanks for that _CY_

Joel gave me some advise last fall in preparation for my trip. I knew he wasn't around here as much so I just thought I'd see who jumped up.

I'm a little confused. You say operating range is 13.3v to 12.85v but it will charge slightly at 13.8v. When mine gets below 13.5v the little meter on my bike has pretty well gone solid red which I thought was pretty close to the end of the world. Was 12.85v a typo?

At what voltage does the battery start being discharged?

I checked the voltage of my battery yesterday after the bike had sat for 5 days after a 4 hour ride. Voltage was 13.6v.

Checked it again today after running it about 30 minutes yesterday and it was 13.7v

Did some tests yesterday and today and with everything off that can be turned off, the voltage climbed to 14.3v and stayed there. With everything turned on including both the jacket and grips on high, the voltage dropped down to 13.5v - 13.7v @ 4000 rpm. I didn't leave it there for a long time but the voltage seemed to be deteriorating.

So, does it make sense that the system seems to be struggling to power 290 watts worth of bike and gear?

By the way, my meter is a cheapy $50 meter. I've never checked it against a good meter but, I'm sure I have to go into town tomorrow and maybe I'll see if I can find someone to calibrate it for me.
LiFePo4 is a completely different animal than PB. but charging systems voltages designed to support PB is an almost prefect fit for LiFePO4.

to understand it's necessary to dive into mumbo jumbo of discharge curve of LiFePO4, which is shown in chart below.

all LiFePO4 12v batteries are fully charged at 14.6V ... voltage drop down to 13.3v only constitute 10% of available AH capacity.

13.3v to 12.85v represents 90% of available AH capacity .. a very flat discharge curve. hence reason why it's necessary to know if your meter is accurate.

resting voltage the next morning before starting your bike will give an accurate state of charge assessment. if you don't have time to wait overnight to measure. simply turn on your lights for a few seconds to bleed off surface charge. but it's more meaningful to know your battery has a full charge next morning before starting your bike.

if your LiFePO4 battery is reading 13.6V after sitting several days. that's an indication your parasitic drain is not excessive and your battery is fully charged. odds are everything is working exactly as designed.

failure mode for all permanent magnet charging systems when RR goes out .. 17v+ is delivered to your battery. if left long enough will kill your battery, PB or LiFePO4. then you will be replacing both RR and battery. catch it soon enough, your battery will be saved.

recommendation is to install a volt meter if you don't already have one. it's handy to understand your battery has 9.2AH actual capacity. this means your battery will support a 9amp load for about one hour with your charging system completely dead. so if your meter shows battery not charging for few seconds .. not a big deal, even with tiny 9.2AH reserves.

better to carry a spare RR and stator on extended trips. which means you will not need either one

_cy_ screwed with this post 05-30-2013 at 05:24 AM
_cy_ is offline   Reply With Quote