Regulator to battery fuse rating

[Steve]

I would also prefer smaller fuses, which is why I asked my original question.

Not sure why smaller fuses would be "preferred", you really need to go with what is necessary.

Since you have changed the wiring of your bike by re-routing your regulator output straight to the battery, please re-read my post #4.

Feel free to put in as small a fuse as you "prefer" or feel comfortable with, but also feel free to have a supply of larger fuses on hand.

Either way, please report back on your findings. If a smaller fuse does, indeed, work, some of us who are advocating larger fuses would appreciate knowing that a smaller fuse will work.

.

[GSJim]

Not sure why smaller fuses would be "preferred", you really need to go with what is necessary.

Since you have changed the wiring of your bike by re-routing your regulator output straight to the battery, please re-read my post #4.

Feel free to put in as small a fuse as you "prefer" or feel comfortable with, but also feel free to have a supply of larger fuses on hand.

Either way, please report back on your findings. If a smaller fuse does, indeed, work, some of us who are advocating larger fuses would appreciate knowing that a smaller fuse will work.

.

By "smaller fuse preferred" I was thinking about using the original wiring and stock T for the regulator output as suggested by posplayr. I have to stop posting before my first coffee is consumed.

I haven't changed the regulator positive wiring yet, just the wiring between the stator and regulator. I thought that going directly from the regulator to the battery through a fuse was a "best practice" for the GS, but as usual you guys have given me more to think about. The final decision will depend on the condition of the regulator positive wire and the wire in the harness. I don't have the original regulator to check. As far as I can remember, the regulator failed shorted and blew the 15A main fuse.

If I make any changes I will update my project thread.

Thanks.

Jim

[Steve]

I haven't changed the regulator positive wiring yet, just the wiring between the stator and regulator. I thought that going directly from the regulator to the battery through a fuse was a "best practice" for the GS, but as usual you guys have given me more to think about.

We still consider direct wiring the regulator to the battery to be "best practice".

It's just that, if you do that, you are changing the fusing requirements. The regulator output will not be changed, but, as pointed out earlier, the fuse between the regulator and the battery does not appear until AFTER some of the regulator's output splits off to power the rest of the bike.

It is my opinion that the only reason there is a 15 amp fuse in there in the first place is because before the bike is running, ALL the current to run the bike (lights, ignition, etc.) will be going through the MAIN fuse. After the bike is running and the stator/regulator are doing their thing, only battery-charging current goes the other direction through that fuse, and it probably does not need to be as large.

However, when you wire the regulator directly to the battery, you still need to have a fuse between the battery and the regulator, but ALL the regulator's current is going to be going through that fuse, not just part of it, as before, in the original wiring.

.

[posplayr]

We still consider direct wiring the regulator to the battery to be "best practice".

Steve, I can NOT disagree with someone wiring directly to the battery especially if they have one of the older style fuse boxes. However, when you consider the single point power and grounding and all else being equal, I would maintain the "T" as it minimizes current flow between the R/R and battery (on both the + and ground sides). This makes the charging voltage higher if there is corrosion between the R/R and battery. Of course with big leads and clean contacts it will matter little.

It's just that, if you do that, you are changing the fusing requirements. The regulator output will not be changed, but, as pointed out earlier, the fuse between the regulator and the battery does not appear until AFTER some of the regulator's output splits off to power the rest of the bike.

It is my opinion that the only reason there is a 15 amp fuse in there in the first place is because before the bike is running, ALL the current to run the bike (lights, ignition, etc.) will be going through the MAIN fuse.

You are correct that the main fuse has to be sized to run the whole bike. This current is 11 amps when not running and 11 amps peak when the R/R goes into regulation. If it really took 15 amps then the 15 amp fuse would probably blow much more often than it does in practice.

After the bike is running and the stator/regulator are doing their thing, only battery-charging current goes the other direction through that fuse, and it probably does not need to be as large.

As noted above, even when the bike is running, the battery has to supply the full 11amps when a SHUNT R/R shunts or a SERIES R/R opens.

However, when you wire the regulator directly to the battery, you still need to have a fuse between the battery and the regulator, but ALL the regulator's current is going to be going through that fuse, not just part of it, as before, in the original wiring.

.

re my original comment: as a general rule if there is a fault condition you are trying to protect against using a fuse(i.e a battery short), the higher that fuse is the less protection you have. I'm sure there are exceptions but a fuse blowing a 15 amps is better than 18 amps running through a 20 amp fuse and making something hot because it is below the 20 amp fuse current.


Even though we have berated the GS charging systems grounding at length, I think that the (+) power split at the "T" with the main fuse isolating the battery from everything else is good practice and arguably the best practice.


When the R/R is charging the Battery, this schematic minimizes the number of connections and the amount of current between the R/R and Battery while still keeping a fuze between the battery and everything else.

The "T" is really the corresponding point on the positive side as the single point ground is on the negative side. It avoids "current sharing", or in other words splits off the currents as soon as possible (on the positive side) and consolidates them at the last point (on the negative side).

The R/R is still directly across the battery, but of course it is through the stock harness.

[salty_monk]

The bike I had fuses blow on used an Electrex stator (the higher rated one) & a Mosfet FH012 RR if that helps...

I haven't tried anything lower than a 30 on my Skunk (STock Stator with an FH012).

[GSJim]

The bike I had fuses blow on used an Electrex stator (the higher rated one) & a Mosfet FH012 RR if that helps...

I haven't tried anything lower than a 30 on my Skunk (STock Stator with an FH012).

I have no idea what stator is installed on my bike. The original fried and the shop didn't put any part or model number on the work order. I doubt it was an original Suzuki part because it wasn't expensive enough. The regulator is an Electrosport ESR090.

Here is another question I was thinking about last night. If I wire the regulator output directly to the battery and then blow the main fuse, it leaves the regulator output unloaded. Is this a recipe for roasting a stator? The bike will run for a while on the battery. The stator will still be generating and the regulator will be shorting the current to ground, generating lots of heat.

Jim

[Steve]

The R/R is still directly across the battery, but of course it is through the stock harness.

Jim, I agree with you, but I have found that stock connection to be faulty on occasion. Rather than tear the harnes open to re-crimp or solder the connection, I have found it easier to move the R/R output to the battery.

Both situations work, it's only semantics which one is more "right".

.

[GSJim]

Here is another question I was thinking about last night. If I wire the regulator output directly to the battery and then blow the main fuse, it leaves the regulator output unloaded. Is this a recipe for roasting a stator? The bike will run for a while on the battery. The stator will still be generating and the regulator will be shorting the current to ground, generating lots of heat.

Jim

After some additional thought, leaving the regulator with no load would overheat the regulator, not the stator, if you have a shunt regulator. The stator will always have the same output and the shunt regulator will short it to ground, generating heat in the regulator. The stator will overheat regardless of regulator load.

Jim

[MisterCinders]

If folks are blowing fuses on the RR to battery link, wouldn't you want to change the wire gauge when you up the fuse? Just bumping up amps in a fuse is bad mojo since that wire is still getting hotter than the old fuse.

So if your 15A fuse can't handle the juice, changing to a 20A fuse means you are embracing that hot wire. Wouldn't the better move be to drop a gauge in wire (increasing the size) and then changing to a higher amp fuse?