t99ford

Having just spent a little time researching MOSFET and thyristors, as they apply to the regulator application, it becomes very clear as to why the former is the more efficient option.

Both perform a nearly identical function. However, once the thyristor (latching diode, while forward biased) has allowed conductance, it is much slower to release the "latch", especially if the anode current of the diode is exceeding the latching current. So, two things keep the thyristor conductance latched: trigger current, or annode current. If the annode current is above the holding current of the thyristor, it will remain latched. It can be manually switched off by changing the bias of the diode to negative. This method is not used in the SH R/R, as the SH relies on annode current to fall off, allowing the thyristor to open. However, the entire process is slow to react as it is entirely dependent upon the current differential between the trigger current and the anode current to release. This equals more heat. As you would imagine, the whole process is further slowed as the thyristor gets older.

The MOSFET transistor uses a positive gate, more likened to a light switch. When current is applied to the gate of the MOSFET, it closes the switch. When current is removed, the switch opens. This occurs much more quickly due to the switch action's direct relationship to the applied gate current, rather than on current differential between two points. It seems that as the switching action is much more reliant on gate current, this regulating system would be much less prone to the kind of burn down experienced on the SH than are the tyristor types.

Anyway, its kind of nice to know why the charging rates and variables are so much different between the two...

t99ford

I was contacted by the president of Shorai today. In talking with him, I learned of some additional information:

It turns out that the small case batteries had reduced plate spacers installed. This places the plates closer together inside the case. It was done to improve starting current flow, as everyone knows this is an area of some weakness on Lipo4 batteries.
During the production run in which my battery was made, there was an issue with how the plates were joined. Evidently a crimp was made that could cut or circumvent the spacer, allowing the plates to touch (short). This caused the fire. According to the the people I spoke with (and of course common sense), this issue will present itself within the first few cycles of the battery--so if you have one and it has been working, you will do not have a time bomb, your battery is ok.
I am not sure which issue caused the concern knowing this. However, the charging system scenario is still valid, and I would recommend changing to the MOSFET system if at all possible. This is an easy change if you have three stator wires, a postive wire, and a ground wire in your current regulator.
Anyway, part of the Shorai stocking issue is a redesign of the battery, which will double the thickness of the plate spacer. This will reduce cranking effectiveness to a degree, but will allow for greater safety. I was assured that the overall performance of the battery would not be reduced by a large degree. Additional improvements will include thicker battery terminals (changed from 1 mm to 1.5 mm) to reduce bending. I was told that Shorai hopes to have these available by mid April.
I was also informed that Shorai has sold approximately 3000 of these batteries, of which only 12 have been returned for warranty issues. The president further explained the complexities of the new technology of these batteries, and as to the very newness of the design.
As for my end, I am very pleased with the handling of this issue. I am being issued one of the new series batteries of even larger capacity. They are re-imbursing the cost of the original, providing a replacement free of charge, and paying for all the damage to Kool-Aid. And they are compensating me handsomely in addition to this. The issue has been handled promptly and with very professional and speedy methods. I could not be happier.

So far, +1 for Shorai...

skokievtr

Tweety, for a replacement VR-R, which Yamaha year & model is best for use in a VTR? I know how to do it & just need the optimum part number.

Thx

Tweety

Well... The list is looooong, and it's not just Yamaha's... Yamaha, Kawa and a bunch of others use Shindengen as the supplier of R/R's and they all do the same thing... The one's that have MOSFET's all have a marking starting with "FH" and a bunch of numbers... So it's more a matter of getting one with the right plug... Two types exist...

Older one's with a plug that isn't sealed... Works fine, and you can just pop the spade connectors on and go... Not that great in terms of corrosion though...

Newer type with the sealed connectors, here you need to buy the correct plugs from Eastern Beaver or some other place... But much better in the long run...

For a rather incomplete list... Yamaha R1/R6 newer than 2001, most Kawa's newer than 2000... Yeah, it's a bit unspecific... But go look on eBay, usually the seller posts a pic of the marking, look for the "FH" and look at the plug... if those two match your preference, it's a match...

skokievtr

Thx

ShoraiTech

Hi,

In addition to making some changes to cell structure and the beefy terminal upgrades, we are also going to add an over-charge protection circuit to all future LFX production. Our next batch should arrive on April 25th we expect (pretty solid date, give/take a few days).

The cell structure changes alone nearly eliminate the possibility of internal cell short circuit, even if the charging system is over-voltage. Also, lifespan during high-temp storage (AZ garages, etc) will increase, and self-discharge rate is reduced even further (longer storage before recharge is required).

Then the charge protection circuit will add an addtional layer of protection, pretty much insuring that the LFX cells are not affected by a rogue charging system, at all.

Frankly, though, even we are a bit surprised at the tiny return rate we have seen so far (<1/2 of 1%), and very encouraged by it. Our two new production lines - with the newest and best equipment - and the protection circuit and cell upgrades will make it even better. And we plan to continue looking for every little thing we can do to improve our LFX, going forward.

And... if we can get our volume up high enough, we hope to see cost reductions that we can pass on to you in the form of lower prices.

We're having fun, and really appreciate your support.

All the Best,

David
Shorai Tech