Power Inverter - Fan Doesn't Do Anything - I have a question.....

[John Kimble]

What is the best way to get the fan to work without wiring it straight to the +/- terminals?


I want it to work the way it is supposed to (meaning, you flip the switch and the fan comes on along wtih the rest of the circuit). But I don't see a way I can do that without connecting the fan directly to the +/- terminals, in which case, would cause the fan to constantly run as long as it's connected to the battery.

I don't have a schematic, so I figured I'd post a message in a couple of these groups and see what kind of response I got.


Thanks for the help.

 

[Ken Taylor]

What is the best way to get the fan to work without wiring it straight to the +/- terminals?


I want it to work the way it is supposed to (meaning, you flip the switch

and the fan comes on along wtih the rest of the circuit). But I don't see a
way I can do that without connecting the fan directly to the +/- terminals,
in which case, would cause the fan to constantly run as long as it's
connected to the battery.

I don't have a schematic, so I figured I'd post a message in a couple of

these groups and see what kind of response I got.

Thanks for the help.

I assume from the little you've given us that the fan comes on when it's
needed, rather than when you want it (all the time, for some unexplained
reason). Is this correct? Why do you want this? Is it worth the trouble if
you haven't got the schematic or the diagnostic skills to check it out?

Ken

 

[Joerg]

Hi John,

If you can't get to the switch the only way I see is sense the current in the + or - cable and use that signal to turn on the fan. I don't know what would be sensitive enough, maybe a Hall sensor? Modified Reed relay?

You'd have to make sure the fan comes on at the power intake where it is needed to cool things and not any later.

Then there are thermal switches, often called thermo disks. These are simply switches that are screwed onto a heat sink. That only works if the heat sinking to the outside is done very well, it won't work if stuff inside gets hot.


Regards, Joerg

 

[John Fields]

What is the best way to get the fan to work without wiring it straight to the +/- terminals?


I want it to work the way it is supposed to (meaning, you flip the switch and the fan comes on along wtih the rest of the circuit). But I don't see a way I can do that without connecting the fan directly to the +/- terminals, in which case, would cause the fan to constantly run as long as it's connected to the battery.

I don't have a schematic, so I figured I'd post a message in a couple of these groups and see what kind of response I got.

 

[Joerg]

Hi John,

You connect the - side of the fan to the - terminal and the + side of
the fan to the low side of the switch, assuming the switch is on the
high (+) side of the circuit.

Sometimes that is tricky with larger inverters. One of the versions I
saw had a tiny switch that connected to the pin of a chip and ground.
The power path was always under juice but with the switch off the FETs
were turned off.

Past a few hundred watts and when the wires become the size of a finger
a 12V/120V inverter can't really be switched with anything off the shelf
anymore.

Regards, Joerg

 

[John Fields]

Hi John,

Sometimes that is tricky with larger inverters. One of the versions I
saw had a tiny switch that connected to the pin of a chip and ground.
The power path was always under juice but with the switch off the FETs
were turned off.

Past a few hundred watts and when the wires become the size of a finger
a 12V/120V inverter can't really be switched with anything off the shelf
anymore.

---
Good point. Prob'ly what I'd do under those circumstances (and to
keep from having to digging around in the inverter's innards) would be
to turn the fan on with 12V from the battery and a 120VAC relay
running off of the output of the inverter or else build a little
120VAC ->12VDC supply just to run the fan. A transformer with a CT
secondary and a couple of diodes, or no CT and a full wave bridge. No
cap even...

 

[Joerg]

Hi John,

Good point. Prob'ly what I'd do under those circumstances (and to
keep from having to digging around in the inverter's innards) would be
to turn the fan on with 12V from the battery and a 120VAC relay
running off of the output of the inverter or else build a little
120VAC ->12VDC supply just to run the fan. A transformer with a CT
secondary and a couple of diodes, or no CT and a full wave bridge. No
cap even...

Yes, that sounds like it is the ticket here. Since he seems to have a
12V fan then the relay could indeed just connect it to the battery as
the inverter's output comes up.

Many large inverters have a minimum load sense so they kind of drop dead
when the load is too small. Sometimes that is called auto-start and
prevents battery drain when someone turns off a TV but forgets to turn
off the inverter as well. So the OP would only have to make sure that
nothing in there gets too hot when the inverter spends extended time in
this hibernation state.

Regards, Joerg