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Old 03-12-2012, 05:12 PM   #165
JoelWisman
Beastly Adventurer
 
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Joined: Apr 2009
Location: STL, MO, USA
Oddometer: 1,392
What I know....

When the battery arrived from being used hard by Lost Rider for 4 or so months, it was horribly imbalanced. Lost Rider does not have any charger so like many, only the bike charges the battery.

His mount is an F800GS I know well from being a BMW dealership shop foreman and being front line on many many BMW issues.

The F800GS has a 13.8 volt charging voltage. I don't know why, it almost as if they were planning on putting a GEL VRLA battery in the F8's and changed their minds and dumped AGM's in them at the last moment without changing the regulation voltage. It is not as if BMW is stupid, the R1200GS/GSA, S1000RR, K1300S/GT, K1600GT/GTL all have charge voltages around 14.4

I would have to say it was well on it's way to complete failure though likely without symptoms since LiFePo4 batteries have a low enough internal resistance that they will put out, till one day all at once they won't.

Best I can dig up is that a Shorai LFX18 is a 6 amp hour battery, and that includes the last 20% of charge which they don't want you to use, so effectively a 4.8 amp hour battery.

This being the case, I am seeing amp hour capacity per cell that is all over the frisking board!

Cell 1 appears damaged, and this seems logical. It was the cell with the highest state of charge and in series with 3 other depleted cells, likely saw much higher voltage then designed for.

Cell 2 is sorta kinda reasonable.

Cell 3 is actually showing more capacity then spec'd

Cell 4 is also showing a reduced capacity compared to it's state of charge. Perhaps damaged by Anode damage from too low of SOC or even cell reversal?

I don't know. I don't have any special charge equipment and won't be buying any as I am not at all convinced that lithium chemistries are the way to go for adventure riding which is all I do. This may change, but not with this sickly battery lol.

What I do have is a charger that will charge across the main terminals at 800mA pairing back to 200mA at 14.4 volts, then ceasing all together when current declines further.

It will not exceed 14.4 volts under any circumstance confirmed by plotting it's algorithm on a paperless recorder.

I built a bottom equalizer with some spare parts and a bread board with a pot I can use to adjust disconnect voltage which I had set for 3.2165 volts and hit its mark on every cell within 1% It only applies a 200mA load, so waiting now for it to finish the second draw down so I can charge the whole thing equalized.

The F8 also has massive AC ripple and a lot of HF switching noise and has a battery compartment that is hot but asymmetrically hot.


Shorai keeps ramping up the size of battery they recommend for the BMW F800. The started with an LFX14 recommended and after a high failure rate with both that and the LFX18, currently recommend the LFX21.

This is odd, because compared to the R1200GS and many other bikes, the starting demands cold or hot of the F800 is a walk in the park.

As shown in tests, the Shorai will balance in series slowly when seeing the charging voltage my Capo puts out which varies greatly by load and engine speed but gets into the 14.55 volt range for brief periods and averages about 14.34 on the freeway.



Working hypothesis: Shorai does not balance either cell resistance or capacity well or has self discharge that varies widely. 13.8 volt charging of the F800 is not high enough to permit the very limited balancing LiFePo4 packs will do when voltage is continued after fully charged. The cell with the lowest capacity, highest resistance, or lowest leakage current gets damaged by high voltage as the cell the most opposite gets damaged by under voltage until the battery rapidly fails.

Just a theory, but all evidence points to high incidence of failure of Shorai in F800 application and Shorais every increasing recommendations of battery size for the F800 bares this out.

If true, this argues strongly that 13.8 volt charging systems are not adequate for the Shorai battery.

Big hedges: As stated, the F800 also has unusually large AC ripple, loads of HF switching noise from PWM pump control, and a hot asymmetrically heated battery compartment.

I have spent half my life reading up on new technical things though only 2 or 3% on batteries. I will continue reading up on LiFePo4 but any first impressions or suggestions for experiments to confirm? :)
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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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