Auxiliarly Lights - How big is my alternator?

Soundguy · Sep 29, 2003

( This will only tell me if I've got enough "room" in that particular circuit. The alternator may not have enough "umph" (that's a technical term... ) to drive all of the circuits that I have access to (or even "all" of one circuit). If, as has been suggested in other posts, I only have a 10 amp alternator, this theory wouldn't hold true...
)

Not exactly... just beacuse you have a 10 amp alternator doesn't mean that the 'theory' is wrong.. just means that while running that load, your storage battery is discharging the the remaining amps in excess of what the alternator can handle... just like it would do if you were not running, but had the lights on. Duration at that load would be determined by the amp hour rating of your battery, at that load.

It is quite possible to have a fused circuit that has a fuse rating higher than the max output of the alternator.

Soundguy

Mikemas · Sep 30, 2003

Bill,
You are correct about drawing 19 amps with the headlamps, tail lamps, and auxiliary lights. I do not run them simultaneously due to the possible current drain on the battery. Soundguy makes a good point about circuits being within their fused limits, but the overall system not being able to keep up with the demand of the combined draw of the circuits. Therefore, I wouldn't recommend running all the lights at one time, unless you make some other plans to replenish the charge in the battery. I also agree with Soundguy about the charging / lighting issues on the B-series Kubota. It is a weak link in an otherwise bulletproof machine. I have expressed my opinion to Kubota via letters and questionaires, but I doubt they'll change it on the assembly line. They're getting by with what has become acceptable, and then making a little more on parts when somebody does decide to upgrade to a 40 amp alternator.

Mike

Soundguy · Sep 30, 2003

( about the charging / lighting issues on the B-series Kubota. It is a weak link in an otherwise bulletproof machine )

I think you hit the nail on the head. The mechanicals on the machine are good from what I've seen.... and as you point out.. it is doubtfull that they will upgrade the charging unit from the factory... as it meets the minimum needs of the tractor, as shipped. After the owner gets it.. it is up to him to get it upgraded to do more work etc.

Soundguy

bcarter · Oct 1, 2003

Not exactly... just beacuse you have a 10 amp alternator doesn't mean that the 'theory' is wrong.. just means that while running that load, your storage battery is discharging the the remaining amps in excess of what the alternator can handle... 

Agreed... My assumption was that I didn't want to run a load that would drain the battery and I didn't make this assumption clear.

bcarter · Oct 1, 2003

Mike,

 ... I do not run them simultaneously due to the possible current drain on the battery... 

OK...this at least partially answers my question. If you can run 2 55W loads (either your primary or auxiliary lights) with no problem, then I should be able to run with 3 35W loads (my auxiliary lights) and not have a problem since my current draw would be slightly less than yours.

...or suppose that I could just pony up the $$$ for a 40W alternator /forums/images/graemlins/frown.gif and then I could light up the whole neighborhood... /forums/images/graemlins/grin.gif

Thanks...

Junkman · Oct 1, 2003

( ...or suppose that I could just pony up the $$$ for a 40W alternator /forums/images/graemlins/frown.gif and then I could light up the whole neighborhood... /forums/images/graemlins/grin.gif

Thanks... )

That is amps, not watts........ and 40 Amps isn't that much.... about enough to power 480 watts at 0.3 Ohms. To keep the resistance down, use the finest stranded copper wire that you can find.

WATTS ÷ AMPS = VOLTS.........Voltage
WATTS÷VOLTS = AMPS...........Current
VOLTS x AMPS = WATTS..........Power
OHMS=Resistance

PS.... no I am not that smart...... just looked it up........ the Junkman /forums/images/graemlins/shocked.gif

Rick Jay · Oct 1, 2003

bcarter and all,

I'm not sure how many hours of continual use you are planning on using your lights, but there is one factor I haven't heard mentioned yet, and that is the reserve capacity of the battery. You can draw more current out of the battery than you put into it, you're just limited on how long you can do that.

I just checked my manuals for my B2910, and I'll be danged if I can find the battery reserve capacity (amp-hours) in the published documents. I'll have to check the actual size of the battery in the tractor. Anyway, assuming the amp-hour capacity of the battery is at least 20 amp hours, that means the battery could "theoretically" run 2 55 Watt lights (about 9 amps) for more than 2 hours without fully discharging. (20 amp-hours divided by 9 amps = a bit more than 2 hours.)

Everything I say here is based on a 20 Amp-hour battery.

This means that if you initially have sufficient current draw from all the lights such that the dynamo is "just keeping up" with the current draw, you can run indefinitely. If you have extra lights that draw, say another 10 amps, you can still run them, but the battery will slowly discharge...in this example, over a span of about 2 hours. If you occasionally shut down some of the lights, the battery will regain some of it's charge.

So...if you're going to be out working at night for extended periods, you need the bigger alternator. If you just want the "extra lights" for short periods of use, I don't think you're going to be putting too much at risk by exceeding the charging capacity.

I guess another option is to find a place to mount a second battery (a biggun'...like a car battery) and run the auxiliary lights off of that. During the day, charge the battery up with a 120 volt charger and it'll be ready for the next night.

I'll admit it's not the "self-contained" solution of a heavy duty alternator (and I also feel that such a critter ought to be standard equipment), but I guess it might be a viable alternative for those of us that are fortunate enough so that we don't generally have to work in the dark. Plus, during the day, you could use the "extra" battery to power an inverter for those that might need limited 120 V.A.C. power out in the field.

Well, in my case, with the standard dynamo, I've got 2 additional 55 watt halogens mounted on the ROPS...one pointing front and one back...and it's sufficient for my use. And on my small property, I can run an extension cord to anyplace I need from the house. /forums/images/graemlins/crazy.gif

To each his own, I guess.

~Rick

Soundguy · Oct 2, 2003

( there is one factor I haven't heard mentioned yet, and that is the reserve capacity of the battery. You can draw more current out of the battery than you put into it, you're just limited on how long you can do that.
)

Actually at the top of page 2, I addressed exactly that point... any load over the capability of the alternator is taken care of by discharge from the storage battery.

Soundguy

Rick Jay · Oct 2, 2003

Sorry, Soundguy, I read that but forgot about it after reading the other posts.

The main point being, that it is O.K. to discharge the battery a bit if people only need the extra lights for short periods of time.

~Rick

Soundguy · Oct 2, 2003

( The main point being, that it is O.K. to discharge the battery a bit if people only need the extra lights for short periods of time.
)

Sure.. otherwise cars wouldn't have an 'accessory' option on the ignition switch.

It is a pretty universally recognized that the storage battery for a vehicle is used to start it, and run loads when the charging system is not runnning.

Soundguy