DIY Powerpack and electrical issue

[lennon33x]

So did some research on a DIY power pack for monolights. There were some good DIYs on the net, and I built my own. I initially used a 12v 7.5mAH battery used to power small electronic devices, but it only gave me about 20 flashes before it died (I was running a 180w strobe). So, I upgraded to a 12v lawn mower battery (substantially more powerful, yet still 12v) and upgraded the inverter to a 1000w (with 2400w peak). I am only running a 250w and a 180w strobe, and haven't done so simultaneously yet.

I multimetered a regular outlet and was getting ~122v. So, then I metered the inverter when connected to the battery and turned on and it read ~108v. When I used it the other day (with both continuous and flash lighting) , the circuitry in the strobe (250w) went haywire and started smoking. The fuse never blew (which would be my first inclination when there is too much voltage) and then it died. This is a lower-end model (Neewer), so I don't expect much.

I replaced the strobe, and tried it out again today. I again metered the wall, plugged it in and tried it. It worked fine with no smoke or burning smell. Tried it on the battery pack, and the front portion of the continuous light began to smoke (as if something had caught on the actual bulb and burned). However, nothing like the other day. So, out of curiosity, I metered the plug-in to the cord, and it was was reading ~130v. It is rated at 110v. Any one have any idea why?

I also tried it on the cord for the 180w strobe and it was getting ~128v.

Thanks

 

[Derrel]

I think the why is amateur electrical engineering error...

 

[SCraig]

I think the why is amateur electrical engineering error...

Agreed. If you don't know what you are doing I'd strongly recommend getting someone to help you who does. Electricity is nothing to play around with if you don't understand it. You probably have some wire somewhere that isn't capable of carrying the current you are sending through it.

I am very surprised you were able to get 20 flashes from a 7.5mAh battery on a 180 watt strobe though. 180 watts at 12 volts is 15 amps. That battery pack can put out 7.5 milliamps for an hour, or 15 amps for about 1.8 second. The pack should have melted though since nothing in it was designed to handle 15 amps.

 

[lennon33x]

I think the why is amateur electrical engineering error...

Agreed. If you don't know what you are doing I'd strongly recommend getting someone to help you who does. Electricity is nothing to play around with if you don't understand it. You probably have some wire somewhere that isn't capable of carrying the current you are sending through it.

I am very surprised you were able to get 20 flashes from a 7.5mAh battery on a 180 watt strobe though. 180 watts at 12 volts is 15 amps. That battery pack can put out 7.5 milliamps for an hour, or 15 amps for about 1.8 second. The pack should have melted though since nothing in it was designed to handle 15 amps.

my apologies...I mean 7.5 aH.

This is not rocket science though. I used the cords provided by the manufacturers, rated for a 12v car battery to hook it together. I just don't understand why the use of the plug used for the strobe would cause an increase in voltage.

 

[Qveon]

If your inverters are putting out 108, then 130, then 122, IMO you have inverter issues. When I get up I'll play with my inverter to double check, but i have never had your issues, then again i have never plugged a mono-light into my inverter. Although on the other hand most 120v devices should be rated to work +/- 10% of that voltage and be ok. Your monolights might not like the clipped sine wave being put out by the inverter.

 

[lennon33x]

If your inverters are putting out 108, then 130, then 122, IMO you have inverter issues. When I get up I'll play with my inverter to double check, but i have never had your issues, then again i have never plugged a mono-light into my inverter

Thanks. I tried plugging in a 60w light simultaneously to see if it changed the load, and surprisingly it went up. I was thinking that it was an inverter issue and not a cord issue. I also tried a different SLA battery, and alas, the same effect. I may switch out inverters and see what happens. Let me know what you get on your end.

 

[Patrice]

I think you'd be better off getting a proper power pack sold for the purpose at hand. You are burning through strobes at a pretty fast clip. You're going to run out of money if you keep going as you are!

 

[lennon33x]

The inverter is faulty. Not a fault of my own. I replaced the inverter and the voltages are the same directly in and through the cord. Thanks for those that helped.

 

[Patrice]

Glad you got it sorted. Test your inverter every once in a while, the cheaper ones tend to fail a bit quicker than the premium ones. A good 1500 watt 12 volt pure sine wave inverter could set you back $400 to $600 or more.

 

[Qveon]

The inverter is faulty. Not a fault of my own. I replaced the inverter and the voltages are the same directly in and through the cord. Thanks for those that helped.

Good you found the problem. i was just going to say that i plugged a clock, a 60w light blub and a blower fan out of a furnace much too large for the inverter and all of them held within plus or minus 5 volts till the blower tripped the safety.