Re: help needed: watt/sec ?!?


<jimp@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:7bpsc5-jjj.ln1@xxxxxxxxxxxxxxxxxxx
Randall@xxxxxxxxxxx <r.oelerich@xxxxxxxxx> wrote:
On Apr 8, 12:12 pm, "CWatters"
<colin.watt...@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
...
Is there a fuse in the plug or any other marking on the unit? If there
is a
fuse then the current won't be higher than that. In the absence of
better
info you could assume that your inverter needs to provide that current
continuously...

Lets say it's a 1A fuse. Then the power would be 110W.

Good idea! I checked and there is a fuse cover that says "F 2A" so I
unscrewed with a dime coin and there is a very small fuse that I
pulled out, cylindrical, about 1 inch long and 1/8 inch in diameter,
glass with metal ends, thin wire inside it, small lettering on the
metal caps of the fuse that says "F2A L250V". So what wattage would
the flash unit be drawing then, for purposes of figuring what sort of
power pack to get to power it out in the woods or on the beach?

That's a 2 Amp fuse so you can safely assume that the unit draws no
more than 2 Amps peak.

Since this is a strobe light, the peak power is only there for a while
as the capacitors that actually power the light are charged. Once they
are charged, the current draw is going to go down to a very small value
until you fire the light and the caps recharge.

The rule of thumb is that a fuse should carry twice the peak current,
so depending on how conservative the maker was, you can figure the
peak power to be somewhere between 100 to 200 watts.

Most power packs have a continuous rating and a short term peak rating.

So, if it were me, I would look for something with a peak rating in
the 100 to 200 watt peak range.

I've seen inverters in this range for around $20 at Kragen auto parts.


--
Jim Pennino

Remove .spam.sux to reply.

I agree. The absolute most it can draw is 2A continuous. The 250V refers to
the fuse rating not the operating voltage which you say is 110V so absolute
worse case power could be 220 Watts but usually fuses are rated to protect
the cable so <200W actual consumption would be reasonable.

Personally I'd go for a slightly bigger unit (500W?) as there is bound to be
something else you want to power with it in the future. Laptop?

You also need to think about the battery. I believe the battery in that unit
you refered to is 28AH 12V. Officially that will provide 336W for an hour
but I suspect in practice you won't get that, perhaps not even half in cold
weather or when the battery has aged a bit. It's hard to say how long this
will power the flash as we can only work out the max power required not the
typical. Use it for a non-critical photo shoot for the first time!

I think I would use an inverter whch will operate with an external battery
and then if necessary buy something like a 70AH (or bigger) "deep discharge"
or "motive power" lead acid battery. Between sessions keep that it on a
charger that has a "float" or "permanant charge" setting. Avoid allowing it
to discharge totally and avoid storing it flat or it won't live very long.






.

Relevant Pages

  • Re: One Thing After Another
    ... But then my Shurflo house water pump quit working. ... battery in the remote, but no, it's up there somewhere. ... But back to the power leak. ...  I took the fuse out for two days and the ...
    (rec.outdoors.rv-travel)
  • Re: One Thing After Another
    ... But then my Shurflo house water pump quit working. ... battery in the remote, but no, it's up there somewhere. ... But back to the power leak. ...  I took the fuse out for two days and the ...
    (rec.outdoors.rv-travel)
  • Re: "Secret" Overvoltage Protection?
    ... these devices are completely isolated from ship's power is to pull the ... When the master switch in an airplane is off, ... fuse directly from the hot side of the battery contactor. ...
    (rec.aviation.homebuilt)
  • Re: help needed: watt/sec ?!?
    ... info you could assume that your inverter needs to provide that current ... Lets say it's a 1A fuse. ... Then the power would be 110W. ... Since this is a strobe light, the peak power is only there for a while ...
    (sci.physics)
  • Re: "Secret" Overvoltage Protection?
    ... The "tiny fuse" you refer to is actually a single fuse mounted as close as ... doesn't go through the master relay but is wired directly to the battery. ... I mounted that fuse on the master relay bracket and got the ... these devices are completely isolated from ship's power is to pull the ...
    (rec.aviation.homebuilt)