Altrnator- 40a vs 85a

[mrgeoff]

Having a 99 CT, I see that some folks are putting 85a alternators in to replace their 40a alternators...Would there be any problems with this...They seem to have the same brackets and fit...Just wondering if it would cause a problem somewhere down the road...!!!

[hubcapsc]

Some people need high output alternators, all the stuff they've added...

My old OEM alternator does fine with my motolights, quad horn, cobra lights,
heated clothes...

I'm not sure how it could hurt to have a 85 amp one, the OEM one is
pretty high quality... maybe the 85 amp Amazon one is too...

-Mike "ida know..."

[Pete]

No problem other than additional output if you need it.
Small amount of horsepower consumption to produce the additional output.
Also some increase in alternator heat when producing higher amps.

Unless you have added a lot lights and other power consumers you would in all likely hood not be using the additional output.

My thoughts are that the alternator is already not getting a great flow of cooling air because of where it is located. So lets not introduce any more heat.

You may have noticed the alternator cover reports of peeling chrome with standard alternators, heat is part of that issue. Do not make it worse with more heat.

If you do decide to add the increased output alternator, then increase airflow also.

[Steel cowboy]

Valkyries did not come with a higher output alternator from the factory, the higher output alternators were used on goldwings due to the higher amount of electronics and possible addition of a trailer. With today's LED lighting options, even on tow trailers added on, you can get a lot of light for very low current use.  In earlier times adding extra halogen and incandescent lighting on our bikes caused high current demands on our electrical components. I would say, if your going to add LED lighting the standard alternator would do the job.

[98valk]

valkyrie and Goldwing GL1500 OEM alternators are same amps. There is not a difference btwn in regards to rated output. OUTPUT: 546 WATTS & 14.2 VOLTS @ 3500 RPM

when buying a higher output alt ask to see the output performance curve test.
sometimes the higher amps are only at higher rpms which normally are not seen and/or the amps being put out at normal operation levels will be actually lower than OEM. unless the test of the HO alt is more than OEM at 3500rpm and below, your wasting your money.  a clue is does the new alt require the idle rpms to be set higher than the factory spec? OEM I tend to remember is not putting out enough amps at 800 rpms.

[Gryphon Rider]

My OEM alternator does fine with 110W of auxiliary lights and two heated jacket liners.  If I were buying aux lighting today, I would look for LEDs to minimize electrical loads, for a couple of reasons:
1.  Electrical power isn't free.  It takes engine HP to spin the alternator, and the higher the electrical load, the less power is available at the back wheel.  It's not a huge deal, maybe one or two HP, but there it is.
2.  The heat cycling of high currents makes wires, insulation, and connections brittle and weak.  Lower current means longer electrical component life.

If a stock alternator provides the power you need, you are better off sticking with it for the sake of the battery.  When the battery is discharged, it will "take" as much current as the alternator will supply to re-charge.  Batteries always do better with lower charging currents.  A high-output alternator is best matched with a larger battery.

[WintrSol]

My OEM alternator does fine with 110W of auxiliary lights and two heated jacket liners.  If I were buying aux lighting today, I would look for LEDs to minimize electrical loads, for a couple of reasons:
1.  Electrical power isn't free.  It takes engine HP to spin the alternator, and the higher the electrical load, the less power is available at the back wheel.  It's not a huge deal, maybe one or two HP, but there it is.
2.  The heat cycling of high currents makes wires, insulation, and connections brittle and weak.  Lower current means longer electrical component life.

If a stock alternator provides the power you need, you are better off sticking with it for the sake of the battery.  When the battery is discharged, it will "take" as much current as the alternator will supply to re-charge.  Batteries always do better with lower charging currents.  A high-output alternator is best matched with a larger battery.

I agree, except for the one or two hp, since the alternator puts out less than 3/4hp at its rated output, so must pull less than one hp from the engine, under full load. FYI, one hp is 746W.

[Gryphon Rider]

My OEM alternator does fine with 110W of auxiliary lights and two heated jacket liners.  If I were buying aux lighting today, I would look for LEDs to minimize electrical loads, for a couple of reasons:
1.  Electrical power isn't free.  It takes engine HP to spin the alternator, and the higher the electrical load, the less power is available at the back wheel.  It's not a huge deal, maybe one or two HP, but there it is.
2.  The heat cycling of high currents makes wires, insulation, and connections brittle and weak.  Lower current means longer electrical component life.

If a stock alternator provides the power you need, you are better off sticking with it for the sake of the battery.  When the battery is discharged, it will "take" as much current as the alternator will supply to re-charge.  Batteries always do better with lower charging currents.  A high-output alternator is best matched with a larger battery.

I agree, except for the one or two hp, since the alternator puts out less than 3/4hp at its rated output, so must pull less than one hp from the engine, under full load. FYI, one hp is 746W.

Your gonna make me do the math, are ya?

546W = 0.732 HP

But, automotive alternators are around 60% efficient, converting mechanical energy to electrical energy, so...

0.732 HP ÷ 0.60 = 1.22 HP

So, I'll stick to my off-the-cuff one or two horsepower guess.

[MarkT]

I concur on not needing the H.O. alternator in general.  I set up Deerslayer over a dozen years ago with a 1.3kW (90amp) Compufire alternator due to my high demand accessories at the time.  Including air compressor, air suspension, air horn, A/C landing lights, 110w of tungsten spots, 130/90 headlight with relay mod, around 450 LED's distributed around the bike, heated clothing, 400w stereo and preamp with 4 speakers, GPS, Dan-marc solenoid, neon lights - that's all I recall right now. The bike is rigged so I can run the compressor and fill tires, though it's best to do that with the engine running. The lights would dim depending on what I turned on before installing the big alternator.  The bike goes through batteries much more than a stock system does.  And those are the really large batteries for GW's.  

On Jade I have the same demands except less w/o air compressor, all lights LED except the headlight & big spots are tungsten - everything else changed to LED.  No LED fancy lighting, or neon.  This bike rigged to pull trailers - the Timeout camper has all tungsten lights (6 - 194's, 2 - 1156's, 2 - 1157's) and electric brakes, while the cargo trailer is all LED's (1157 function, 3 clearance lights). Otherwise, big stereo (but newer model, high efficiency) with crossover (new), radar, GPS, elect clothing, Dan-marc, fuel pump which runs only 9 minutes per refill (250 mile range), headlights = 2-std H4's, 1-130/90 - about the same accessories.  The OEM alternator keeps up just fine and it's not eating batteries.  I've set it up so I can't forget and leave something on when the bike isn't running, with 17 relays, most on a relay panel under the seat. Circuits that are appropriate to run with the bike off have warning lights, and are intended to run for short times (fuel transfer solenoid) or with a charger plugged in (stereo and USB charger)

I conclude, you would be hard put to really need a big alternator while the install costs money up front and results in replacing batteries more often.

[mrgeoff]

Thanks for all of your output on the Alternator...(No pun intended)...Guess I will stay with the OEM and just keep the 40amper...That is why I like asking question on here...!!!

[WintrSol]

My OEM alternator does fine with 110W of auxiliary lights and two heated jacket liners.  If I were buying aux lighting today, I would look for LEDs to minimize electrical loads, for a couple of reasons:
1.  Electrical power isn't free.  It takes engine HP to spin the alternator, and the higher the electrical load, the less power is available at the back wheel.  It's not a huge deal, maybe one or two HP, but there it is.
2.  The heat cycling of high currents makes wires, insulation, and connections brittle and weak.  Lower current means longer electrical component life.

If a stock alternator provides the power you need, you are better off sticking with it for the sake of the battery.  When the battery is discharged, it will "take" as much current as the alternator will supply to re-charge.  Batteries always do better with lower charging currents.  A high-output alternator is best matched with a larger battery.

I agree, except for the one or two hp, since the alternator puts out less than 3/4hp at its rated output, so must pull less than one hp from the engine, under full load. FYI, one hp is 746W.

Your gonna make me do the math, are ya?

546W = 0.732 HP

But, automotive alternators are around 60% efficient, converting mechanical energy to electrical energy, so...

0.732 HP ÷ 0.60 = 1.22 HP

So, I'll stick to my off-the-cuff one or two horsepower guess.

In the context of adding loads (lighting), we're talking a few tenths of a horsepower, not going from no load to full output capacity of the alternator.

[Gryphon Rider]

My OEM alternator does fine with 110W of auxiliary lights and two heated jacket liners.  If I were buying aux lighting today, I would look for LEDs to minimize electrical loads, for a couple of reasons:
1.  Electrical power isn't free.  It takes engine HP to spin the alternator, and the higher the electrical load, the less power is available at the back wheel.  It's not a huge deal, maybe one or two HP, but there it is.
2.  The heat cycling of high currents makes wires, insulation, and connections brittle and weak.  Lower current means longer electrical component life.

If a stock alternator provides the power you need, you are better off sticking with it for the sake of the battery.  When the battery is discharged, it will "take" as much current as the alternator will supply to re-charge.  Batteries always do better with lower charging currents.  A high-output alternator is best matched with a larger battery.

I agree, except for the one or two hp, since the alternator puts out less than 3/4hp at its rated output, so must pull less than one hp from the engine, under full load. FYI, one hp is 746W.

Your gonna make me do the math, are ya?

546W = 0.732 HP

But, automotive alternators are around 60% efficient, converting mechanical energy to electrical energy, so...

0.732 HP ÷ 0.60 = 1.22 HP

So, I'll stick to my off-the-cuff one or two horsepower guess.

In the context of adding loads (lighting), we're talking a few tenths of a horsepower, not going from no load to full output capacity of the alternator.

Okay. I didn't know anyone was proposing a specific additional load. I feel like I'm shooting at a moving target here. And you were the one basing calculations on the full output of the alternator.

[Kevin Valk]

I sent you an email, as I am having the same trouble with mine. I live in Evans, and could likely sell you my used OEM, as I ordered a rebuilt one from MARS.

[Gryphon Rider]

I sent you an email, as I am having the same trouble with mine. I live in Evans, and could likely sell you my used OEM, as I ordered a rebuilt one from MARS.

What trouble are you having?  I don't think anyone on this thread was indicating trouble, but only discussing the merits of a higher capacity alternator.

[WintrSol]

My OEM alternator does fine with 110W of auxiliary lights and two heated jacket liners.  If I were buying aux lighting today, I would look for LEDs to minimize electrical loads, for a couple of reasons:
1.  Electrical power isn't free.  It takes engine HP to spin the alternator, and the higher the electrical load, the less power is available at the back wheel.  It's not a huge deal, maybe one or two HP, but there it is.
2.  The heat cycling of high currents makes wires, insulation, and connections brittle and weak.  Lower current means longer electrical component life.

If a stock alternator provides the power you need, you are better off sticking with it for the sake of the battery.  When the battery is discharged, it will "take" as much current as the alternator will supply to re-charge.  Batteries always do better with lower charging currents.  A high-output alternator is best matched with a larger battery.

I agree, except for the one or two hp, since the alternator puts out less than 3/4hp at its rated output, so must pull less than one hp from the engine, under full load. FYI, one hp is 746W.

Your gonna make me do the math, are ya?

546W = 0.732 HP

But, automotive alternators are around 60% efficient, converting mechanical energy to electrical energy, so...

0.732 HP ÷ 0.60 = 1.22 HP

So, I'll stick to my off-the-cuff one or two horsepower guess.

In the context of adding loads (lighting), we're talking a few tenths of a horsepower, not going from no load to full output capacity of the alternator.

Okay. I didn't know anyone was proposing a specific additional load. I feel like I'm shooting at a moving target here. And you were the one basing calculations on the full output of the alternator.

OK, misunderstandings all around. I read your post as implying adding lights or accessories could result in a higher load that would take another 1 or 2 hp, so responded that couldn't be, because the alternator could only pull about 1 hp total from the engine, and that adding lights could only add a few tenths, at most, to the load.