Is the rectifier/regulator really as crude as it looks?

[suzyj]

So I removed my crankcase breather canister on my 695, and made a plate to replace it that mounts both the rectifier/regulator block and one of the coils.  That'll give me room to replace my stock Sachs shock with a high zoot factor Showa from a 749.

In addition, the idea of replacing my battery with something made from A123 LiFe cells is intriguing.

So, being an EE by trade, I thought I'd have a look at the charging circuit, to see if it's up to the slightly more demanding charging requirements of four LiFe cells.  So far, everything I've seen points to it being a three phase rectifier, followed by a shunt regulator.

Please, please tell me that the box I repositioned contains more than six diodes and a shunt zener...  Cos if that's so, it's disgraceful.  That's amazingly inefficient.

If that's really the case, then I wouldn't trust it to charge LiFe cells, and would want to make something to replace it.  I'm thinking of a rectifier, followed by a non-isolated DC-DC switching converter (like perhaps a couple of Linear Tech LTM8027 umodule regulators in parallel).  Only issue with this setup is the 60V max input to the converter, but that could be solved by a simple series pre-regulator (a zener diode and a transistor).  Efficiency would be somewhere around 80-90 percent, so it'd dissipate maybe 10W max.

Would anyone be interested in these if I were to make some?  Think regulator that's a tiny fraction of the size of the existing one that doesn't get hot, ever, and that has a really tightly controlled charging voltage.

[Slide Panda]

And yes, it probably is that bad. AFAIK, the same regulator that fits your 695 is the same as mine, from 2000. And it would not shock me to learn that it's the same as even older models

Well... people love mods... but what would be the cost on an item like this?

[ducpainter]

And yes, it probably is that bad. AFAIK, the same regulator that fits your 695 is the same as mine, from 2000. And it would not shock me to learn that it's the same as even older models

Well... people love mods... but what would be the cost on an item like this?

The regulators for the single phase alternators were different.

[Bill in OKC]

Your description sounds remarkably similar to the discrete components visible on my 1975 Suzuki.  If you are thinking about a LiFePO4 charging system, how about one that could balance charge the cells?

[WarrenJ]

My 2000 750 has eaten two regulators in 8000 miles.  I'd certainly be interested.

[floyd turbo]

Sounds good to me.  All I could dream up was a better heat sink.

[Major Slow]

You might have a little problem with the 48 W output you would need 10+ to meet the 520W output (S4R manual states - Alternator Capacity 12 V - 520 W) with the LTM8027. I imagine there are other devices that could be used. Interesting project, I sure would like to see what the alternator actually puts out. Have you characterized it yet?

[sbrguy]

if you can make a rectifier that replace the stock one that takes up a lot less space and also doesn't need the cooling or does not even get as hot ever, then i'm game.

tell me what the approx price is and just make sure that its safe to use on the bike and won't screw up anything and is plug and play and we have a deal.

[scott_araujo]

I haven't looked at it that closely but it sounds totally feasible.  Ducati electrics, especially the regultor, are not known for reliability.  There is an aftermarket replacement already, DesmoTimes carries it.  Not sure if it's different or just a clone.

Remember the golden rule: Never get an Italian motorcycle wet on purpose

Scott

[Speeddog]

I'd be interested. 

[suzyj]

Good to see some interest.  I can't say how much something like this would cost, except to say more than $100 and less than $500   It depends, both on what's in the final thing and in how many are made - electronics stuff gets a lot cheaper per unit if you're making twenty or fifty of something than if you're making two.

The idea of adding circuitry to manage cell balancing is a good one, and doesn't preclude using it with lead acid batteries either (you just wouldn't connect those bits).  I had a look on my bike last night, and it would be quite easy to re-route the part of the loom that go back to the rectifier/regulator so it goes up to the battery box instead, and would remove more wiring that passes the shock, too.  An ideal location for the rectifier/regulator would be in the battery box alongside the LiFe cells.

The 520W alternator spec is in my book, too.  I agree that it's a little dubious (the fuse in line with the rectifier/regulator is 30A, so the absolute most we can hope for is 360W before we blow the fuse), and also agree that the 48W from a single little Linear Tech converter won't be enough.  An interesting point about a crude shunt regulator is that the more power you pull from it, the cooler it gets (as it has to dissipate the balance between the power in and power out as heat).  So perhaps the 520W bit isn't so unrealistic.  It's the 50-100W load that would blow them up.  The Linear Tech converters can be paralleled for more power - alternatively we could just pick a higher power one.

[Some Dude]

very interested

[Ducnial]

Oh yea, and to make matters worse it s stupidly primitive shunt regulator.  So its dumping hundreds of watts right into heat - all the time putting stress on both the regulator and the alternator.   The more you rev it the more heat get dumped.  But wait, that's not all,  if you order today we'll even mount the regulator in the worse place possible  that could ever be devised of for cooling - right under the seat away from cooling air flow.  Given the state of art for even the simplest devices these days it really amazes me that Ducati is still living in the stone age.

[crimsoncloak]

I've often wondered why there isn't some kind of mosfet-switched gizmo in charge of regulating/rectifiying by now.  But even Honda, with its legions of engineers, uses a similar arrangement.

[battlecry]

There are MOSFET VRs out there.  I believe Yamaha has one.  Not for 520W though.

I relocated mine and installed a heat sink.  I'm fine with it.  If something comes along that allows me to use/charge A123 cells reliably, that would interest me.