Oops! I let the smoke out.

[Düb Lüv]

Uh... that's not good. 



Uh... that's REALLY not good. 



Balls.   

Haha. Sorry I had the same thing happen to me. It's hard to look cool when you're pushing your bike home for 2 miles geared up in the middle of summer.

[suzyj]

I think it was suzyj...not Howley.

Yup.  I came up with a design using a couple of DC-DC converters; one to charge the battery and one to supply the rest of the loads.  The idea is that the system can give a nice stable regulated 13.8V with inputs from 15 to 80 odd volts.  I designed it on paper and then put the oem rectifier/regulator to service driving my LiFePo4 battery, which has been running reliably for a year or so.  I revisited the DC-DC converter recently, as to be frank the inefficient oem one offends me.

The problem that I have is that if the stator is disconnected the voltage shoots up to >150V at a few thousand RPM.  So even an efficient regulator still needs a circuit to shunt the excess power from the stator to stop the voltage from getting really high and causing arcs and sparks and potential breakdown of the stator insulation.

Unfortunately that part that shunts the excess voltage is going to get really, really hot.  Defeating the purpose.

[battlecry]

Would a bank of 15V zeners protect a Shorai or A123 battery from flaming if the voltage spikes from a RR failure?  Sounds expensive, but so is a bike with a battery under the fuel tank.

[suzyj]

Would a bank of 15V zeners protect a Shorai or A123 battery from flaming if the voltage spikes from a RR failure?  Sounds expensive, but so is a bike with a battery under the fuel tank.

Not very well.  Zeners have a pretty gradual turn on, so they wouldn't regulate the voltage terribly well.  Also, if the RR failed, then the zeners would then be doing the whole job of the RR, and would soon fail themselves.

Edit:  On reflection, a thyristor crowbar might be a good circuit to use as battery protection.  The circuit at the bottom of http://axotron.se/index_en.php?page=26 would do the job, in line with the battery.  You'd need two 30A fuses, one between the crowbar and battery, and the other between the crowbar and RR.  If the crowbar went off it'd blow both fuses, protecting the battery.  There is still the possibility that the RR goes low impedance and catches fire itself though, as happened to the OP, so it wouldn't protect against everything.

[koko64]

I'm pretty sure the Shorai has a suicide fuse to commit Seppukku rather than catch fire and puke molten chemicals all over your bike.
That is the only downside to such batteries without that feature. Shorai are pricey tho.

When SJ creates her u beaut regulator, they will sell like hotcakes, and she'll be granted sainthood.

[NAKID]

Shorai are pricey tho.

At $159 they're cheaper than a lot of the other lightweight batteries I've seen out there. OEM Yuasa is about $70 and 7.6lbs. The Shorai is 1.83lbs. $90 bucks to lose close to 6lbs and not have to worry about the chemicals of the lead/acid battery burping out? I'm in...