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Old 03-12-2012, 05:45 AM   #162
JoelWisman
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Joined: Apr 2009
Location: STL, MO, USA
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Okay, I am stumped. Consulting text books, online battery sites, and fired off an email of data to a crazy professor sort that teaches battery technology and may eventually respond.

This is what I got so far on a Shorai LFX18 used roughly for 4 months.

Noteworthy that the BMW F800GS has a wimpy pimply 13.8 charging voltage with substantial AC ripple and lots of HF switching noise.

Also worth noting that the F8 has a hot battery compartment because the basic controller (giant SCR switch bank with some logic) bakes the battery with it's heat sync pointed at one face of the battery, about .5" of air gap, asymmetrically with heat concentrated towards cells 3 and 4 IF MEMORY SERVES, it may be cells 1 and 2 that are getting the hottest, or none of the above depending on how the cells are stacked in the battery, but I think the cells towards the positive terminal are getting hottest.

In any case, here are my raw notes so far, very raw. Nothing seems to match up. AH and SOC voltage aren't linearly connected. Its late so maybe I just need sleep but right now I'm about as clued in as an ameba.

I have a high degree of confidence in the measured numerical values, but nothing makes sense of what they are saying.
Any thoughts on what on earth can be determined from this shit salad?


Shorai LFX18, 4 months of heavy service on F800GS

As arrived, at least 4 days of resting13.149
cell1 3.2965 70%
cell2 3.2962 70%
cell3 3.2938 70%
cell4 3.2633 35%
35% imbalance

Capo w F8 regulator 4.5 hours 3 starts 125a withdrawn for 10 seconds, rest 1 hour
cell1 3.2998 70%
cell2 3.2995 70%
cell3 3.2970 70%
cell4 3.2657 35%

Withdrew current from cells individually at approx 0.2 amps to 3.2165 volts (would be 12.886 volts for battery or 20% SOC) This is a 30 hour rate. Shorai says some BS about “PBEQ amp hour” as do all the LiFePo4 power sports battery manufactures I can find. Dig and you find out they rate the battery at 6 actual amp hour, but state that using the bottom 20% will damage the cells and void your warranty. This means you effectively have a battery that is 4.8 amp hour
cell1 2.56 amps 53%
cell2 2.99 amps 62%
cell3 2.87 amps 60%
cell4 0.81 amps 17%
charged cells individually same amount as withdrawn + 10% for a guestimate at charge eff

After 26 hour rest
cell1 3.2991 70%
cell2 3.2997 70%
cell3 3.2968 70%
cell4 3.2646 35%
close enough for government work

Capo 6.5 hours 7 starts, over 2 days
1 hour after 125 amps for 10 seconds
13.708 volts
cell1 3.5820 100%
cell2 3.4448 90%
cell3 3.3447 90%
cell4 3.3142 75%
25% imbalance

3 more hours of Capo riding, all freeway
cell1 3.5819 100% (rounded up ever so slightly)
cell2 3.4494 90%
cell3 3.3492 90%
cell4 3.3181 80%
20% imbalance

Withdrew current from cells individually at approx 0.2 amps to 3.2327 volts (would be 12.93 volts for battery or 20% SOC to bottom balance all cells

cell1 3.99 amps 83%
cell2 4.33 amps 90%
cell3 4.74 amps 99%
cell4 3.04 amps 63%
Charging it at 14.5 volts till acceptance down to 200mA
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Owned to date. Honda Aero 50, Honda Elite 80, Honda Elite 250x2, Suzuki Katana, Suzuki RF600, Yamaha YZF1000R, Kymco Xciting 500, Suzuki GS500, Suzuki Burgman 650, BMW F800GSx2, BMW S1000RR, Aprilia Scarabeo 200, Aprilia Caponord, Aprilia Sportcity 250
I love and miss you Jeneca and I'm sorry.
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