>
>>Has any one ever tried jumping a dead 24V system from a DC 27V welder
>>source? It seems that it should work, having up to 225 amps (mine, any
way)
>>available for starting. What amperage would a person set it at to try
that,
>>or would you set it at max and let it draw what it wants?
>
>I'll assume that you have a generic arc welder with a rectified output for
>the DC and the current selection is done by taps or a wiper system. Then,
>there isn't much difference between a battery charger/booster and a welder.
>
>First off, voltage and current are dependant quanities (voltage = current x
>resistance or current = voltage/resistance). The 27 volts sounds to low to
>be the open circuit voltage (for a welder anyway) so if we assume that the
>27 volts is the output voltage at 225 amps then it is plausible that you
>should be able to get some nice current at the 28 (or more) volts needed to
>charge a 24v battery pair. If the 27 volts is the open circuit (no load)
>voltage then you won't get very far. The current setting on your welder
is
>actually just a voltage setting. If you put a voltmeter on the output with
>no load, you will see the output voltage get higher as you increase the
>'current control'. If open circuit output voltage is not over 28v then
your
>not going to charge the batteries. Every step above that point will just
>increase the charge current.
>
>I would not play with this unless you have an ammeter in the output line so
>you can see what your doing, voltage is less important but you may want to
>monitor it also.
>
>
>>Could you charge the batteries that way, on low amperage?
>
>Again, the amperage setting is actually a voltage control so, yes, set the
>voltage control until you see the charge current (on an ammeter) that your
>after.
>
>And of course make sure the polarity is correct!
>
>
I used to see the electricians jumpstart low/dead batteries on Alco and GM
locomotives with a dc motorgenerator welding rig many times. Nominal voltage
on a locomotive is 64v DC. < When a locomotive is running the nominal
voltage is 72-75 volts depending on where the regulator is set. > Hook up
the cables,
watch the polarity!!! Set the welding current at max but don't start it
until it's hooked up and polarity is double checked. Then push the start
button on the welder and hit the start button on the vehicle. As soon as it
< the dead vehicle> starts shut down the welder and disconnect the cables.
===
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