Topic: Battery Charging

[bambuhiphop]

At what RPM does the system start charging the battery?

[evinrude7]

on the 750 i believe about 3000. 

[calj737]

Just over 2,000 is when the alternator starts producing surplus charge for the stock electrical system.

[bambuhiphop]

Thanks Guys

[TwoTired]

Actually the alternator makes power even at idle, about 1/3 of capacity.  It just that the bike's electrical consumes more than it can make at that RPM.

So the answer of when depends on whether you have lighting on or off.  The battery will charge at a lower RPM when lighting is off.  But, even with lighting on, it should start putting energy back into the battery around 2000 - 2500 RPM.

Naturally, this assumes a bike with all stock components.  Change begets change.

Cheers,

[bambuhiphop]

I was mainly inquiring what it would be if there was no electrical draw from components. This is an area of the bike where my knowledge is lacking and I need to understand it better, haha.

I have no stock components. What I should do is build out a table so I can have a theoretical understanding of what my components pull so I can have a better understanding of what is doing what when. From there I can align those with actual measurements. That will give me a solid baseline to understand what I should look for if I decide to "upgrade" this componentry.

[AirCanuck]

I was mainly inquiring what it would be if there was no electrical draw from components. This is an area of the bike where my knowledge is lacking and I need to understand it better, haha.

I have no stock components. What I should do is build out a table so I can have a theoretical understanding of what my components pull so I can have a better understanding of what is doing what when. From there I can align those with actual measurements. That will give me a solid baseline to understand what I should look for if I decide to "upgrade" this componentry.

Please post results, this would be interesting to see! If it works out accurately I’ll be bugging you for your method. Bought a bike with all non-stock parts

[TwoTired]

Honda states the 550 Alternator makes 150 watts at 5000 RPM.
That's likely a minimum spec.  Production examples may make more depending on the build tolerances and consistency of assembled components.

At idle RPM the Alt. makes about 1/3 of peak output.  The watt output chart vs RPM is a curve reaching about 120 watts around 2500 RPM-ish.

However, since watts is Amps times volts,  (P=IE) if there is no load (no current), it makes no power.  Whatever voltage it develops multiplied by zero is always going to be zero.
Conversely, it's output is self limiting by design.  You can never take more power out of it than it can create.  I.E. if you short the output, it can't make voltage high enough to generate enough watts and overheat (or produce anything near 150 watts).

Simple, eh?

[bambuhiphop]

Simple, eh?

YUP

[bambuhiphop]

This is what I have gathered thus far.

Item	Standby	Operating	Watts
Headlight (Evo 2)
Hi	0	3.5
Low	0	2	0.25
m-Pin Left	0	0.25	3
m-Pin Right	0	0.25	3
Tail Light
Brake	0	0.42	5
Left Signal	0	0.17	2
Right Signal	0	0.17	2
Motoscope Pro	0.0004	0.2	0.00045
M-Unit Blue	0.00045
Breakout A	0	0	0
m-Relay
Coils	0	0.67	8
C5 ignition	0	0.5
Field Coil	0	2.4	28.8
Totals	0.00085	10.53

[bambuhiphop]

So, I got the remaining pieces and updated the table. Looks like I am at 0.00085 amps in standby, 7.03 amps running with low, and 8.53 when running on high beam. If I were to running everything I peak at 10.53 amps and with no lights I am at 5.03 amps.

So, at idle if the alternator is putting out 2 amps I'd be running a deficit of about 5 amps (low), 6 amps (hi), and 3 amps with no lights.

Then at around 2500/3000 RPM the bike should be putting out around 8 amps meaning I have a plus 1 amp (low), neutral (hi), and plus 3 with no lights.

How's my math look? If that's in the ballpark I need to calculate battery charge time based on those numbers. Also, I'm getting all my amp numbers dividing watts by 12v.

[TwoTired]

Your math looks reasonable.

Nice to know worst case.  But, be aware it's a chase your tail scenario.  The voltage won't stay at 12V.  In fact, when the battery is charged, the voltage will certainly be higher.  If you idle for some time, the voltage can get lower than 12.  So, it is not really a constant for equational calculations matching the real world.

If you plug numbers into ohms law (I=E x R),  8.53 amps @ 12V, means your bikes load resistance is 1.403 Ω.  This is likely a constant for worst case load.  But, if you plug that resistance number into the equation above, and raise the voltage above 12V, say 14V, your current and wattage consumption will increase.

On the other hand, the voltage regulator will place the alternator field coil in and out of circuit, relative to system voltage level, this effects the load resistance and the current draw outside of consistency parameters.

Your doing the right things in attempting to predict.  It's just a moving target to nail precisely.  Do set your expectations accordingly.

Cheers,