Alternator - output capacity?

[Santa-2512]

Probably a stupid question?

How do i work out the max load, output, draw ( i don't know how you describe it) i can take with accessories etc,

before the alternator cant keep up, and doesn't supply enough output to keep the battery charged/ electric running?

I know it has an output in amps i believe,, but the items i want to run only gives a watt value

its a 1200TC

Currently (lol) I have

Bike electrics (std)
Hexezcan
Innov
2xfront spots 35w each
Heated clothing, Top, bottoms & gloves


I want to add a pair of lone rider spots which are 145W (each i guess)

Any magic formula a luddite can use to calculate if its going to work ?

 

[er-minio]

From memory it should be around 600W.

From there you can do the A/W conversion (about 50). Watts/Volts=Amp.

 

[TLSgazza]

Not an answer to your question but 145 watt spots, why? is that per spot?
I have a pair of these on my GSA. 20 watts each and are brighter than a bright thing.
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Ignore the price. They are cheaper than that
Just seems a bit excessive with what you have already and you'll be one of those that burn the retinas of any car driver you're following

 

[er-minio]

Yes, it seems a tad high.
Are the Lone Rider spotlights LED? Is it possible that the 145W per spot figure was a comparison between LED and standard incandescent lightbulb power?

When you buy (residential) LED bulbs they are almost always advertised as (for example) "100W equivalent", when the actual wattage is maybe 8W.

 

[Engineer]

The maximum current from a 600W alternator is 600/12=50A.

So estimating that you need 2A continous to charge your battery (this is a big unknown as starting the bike takes a lot of the battery capacity on a 1250GS) so you have 48 amps to play with. I haven't got a clue what current the rest of the bike takes to keep things ticking over but lets guess at another 5A - so you now have 43Ax12V = 516W left for everything elese.

To be safe I would halve that number, so lets say you have 250W maximum for anything you add. That would be my strating point.

Anyone got a better idea????

 

[stever1]

Probably a stupid question?

How do i work out the max load, output, draw ( i don't know how you describe it) i can take with accessories etc,

before the alternator cant keep up, and doesn't supply enough output to keep the battery charged/ electric running?

I know it has an output in amps i believe,, but the items i want to run only gives a watt value

its a 1200TC

Currently (lol) I have

Bike electrics (std)
Hexezcan
Innov
2xfront spots 35w each
Heated clothing, Top, bottoms & gloves


I want to add a pair of lone rider spots which are 145W (each i guess)

Any magic formula a luddite can use to calculate if its going to work ?

The 145 watts is for the pair at full power. I fitted a set the other week to a 1250 GSA and we’ve had to turn them down as they are too powerful.
As they aren’t on full power very often I’d expect the power drain to be significantly less most of the time.

 

[rovert57]

I remember having two 55w spots on my cb500/4 ,if I went below 60 the bike would start cutting out .

 

[Pukmeister]

Mart, I assume you mean to ask how much headroom you have on the alternator before it maxes out, allowing for battery charging, ignition etc.

That is a difficult one to answer as it depends how depleted your battery is after its last start, ambient temperature etc but I guess you need to work on worst case scenario eg battery almost totally flat in winter after lots of hard cranking/reluctant starting.

145W per spot seems a fair bit of draw, most modern LED kit draws very little so if they aren't LED spots I would be looking to find a pair with low draw.

I seem to recall my Hexhead GSA Denso alternator was rated around 60 Amps from memory.

P=VI so 12 x 60 = 720 Watts output (not allowing for volt drop through wiring).

 

[matgriff]

I would say the 145w for the spotlights is an equivalent value compared to an incandescent bulb. Most LED spotlights are around 20w, don't forget that an incandescent bulb is highly inefficient, and generates a lot of heat, LED's are much more efficient and have a much higher lumen per watt value.

Also, remember that the alternator puts out around 14v when running, not 12v

 

[Robbieben]

There isn't a certain figure for what you use when riding, there are lots of variables, battery condition, engine revs, etc, etc.

The bike alternator provides 600 w at the very maximum, i find most are more like 550 w in normal running on tickover, rising slightly 560-580 w as revs increase to 1000 rpm but the more revs used means more draw against the system as more power is consumed to provide power to the coils as revs increase.
Consumption during normal riding with lights on etc will use 300-400 w dependant on system variables. Continuously exceeding 450 w will usually lead to a failure of either the generator or the regulator rectifyer as they aren't designed to run maxxed out for prolonged periods. The more power demanded from them means more heat generated by the two components, heat is not kind to them.

 

[MWH]

Pretty sure Pukmeister is spot on with his calculations. Think from 08 on they went to 720w, GS and GSA. Read that on an American site, the info was from Jim Von Baden and he seems to know his BMW stuff! Had a look in my 09 handbook and it doesn't say in there. Wonder if a clamp type meter could be put around the main battery cable to get an amperage reading while running then convert it to watts to find its running requirement?

 

[er-minio]

The pressing question would be: what do you need 145W spotlights for?
Go LED.

 

[stever1]

Update…..
We’ve just had to turn them down even more !

 

[Santa-2512]

Update…..
We’ve just had to turn them down even more !

What are they fitted to?

 

[Santa-2512]

The pressing question would be: what do you need 145W spotlights for?
Go LED.

They are led

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www.lonerider-motorcycle.com

Spec at the bottom of page

 

[stever1]

What are they fitted to?

1250 GSA. Turned down due to being to bright.

 

[Santa-2512]

1250 GSA. Turned down due to being to bright.

Ah, im looking to put on a hexhead. Are you running any other stuff?

 

[stever1]

Ah, im looking to put on a hexhead. Are you running any other stuff?

All the standard stuff including heated seats. Phone charger , then there’s Chigee thing.
Mv. Remember, the lights aren’t using 145 watts often, only when all on full power.
Incidentally, I take you have a laptop to programme them.

 

[SBD]

They presumably come with a fused feed from the battery. What is the fuse rating?

They claim to be both 180 and 145W, and I doubt this. If they are 180W (each) you’d need 30A to run them , which is bonkers. The fuse would have to be higher rated, say 40A. And the cable is going to be FAT.

 

[stever1]

They presumably come with a fused feed from the battery. What is the fuse rating?

They claim to be both 180 and 145W, and I doubt this. If they are 180W (each) you’d need 30A to run them , which is bonkers. The fuse would have to be higher rated, say 40A. And the cable is going to be FAT.

It’s 145 watts for the pair working fully. I followed the instructions and put them on the white circuit, and set the fuse rating to the recommended 15 A IIRC and it hasn’t tripped out yet.
I do wonder if now I’ve derated the lights wether I could drop the circuit to 10 A

Oh, no fused feed, it’s on the canbus system