Forum Discussion

Explorer

Feb 28, 2017

Ok What Am I doing Wrong!!

We bought a new to us fifth wheel, traded in the old one so I am in the process of moving everything that I had in the other one to this one . I built a battery box for my 2 6volts , hooked up the pos to neg terminals to get 12 volts, ran the white ground from the trailer chassis to battery neg and ran trailer pos to battery pos, every thing works . So I went to hook up my old inverter accidentaly reversed its polarity and blew it up. thats ok I wanted to upgrade soon anyway, So I get a nice 3,000 watt inverter with remote control that was on sale, and mount it on the wall. hook up neg to neg but when I hook up pos I get big spark, now twice shy, I go over every hookup and they are all correct. take the unit and bench test it with a 12 volt I have and it seems to work although the wire gauge I have available is way too small. hook it back up to rv and big sparks again!! I take my multi meter and test it between the pos on battery and unconnected pos on inverter and get 11.point something volts. Now I don't know what I am doing wrong , Should I be getting the 11.point something voltage when I test it with the multi meter this way? A quick internet search indicated that the capacitors in the inverter initially draw in a lot of power to charge them up and will cause a spark when hooking up the inverter but I just don't know if that would cause this much spark. Help!

23 Replies

shepstone
Explorer
Feb 28, 2017
When I test voltage across the battery bank I get 12. 7 volts its only when I test voltage from the unconnected pos on inverter to pos on batt that I get the 11. So it look like the large capacitors are causing the spark.?
Maybe I am being over cautious because the spark I get is about the same size spark I got when I miss-connected the old inverter and blew it up!
GordonThree
Explorer
Feb 28, 2017
Big spark isn't bad, 3000 w inverter is going to have some big capacitors inside, they need to charge up, and that makes sparks.

Install a battery cut-off switch and a fuse between that inverter and your batteries, all will be well.
Bill_Satellite
Explorer II
Feb 28, 2017
This is a bit muddled but I will give it a try. When you check the voltage of the 2 wires you are connecting to the inverter they should read the exact same voltage that you read at the battery bank. If the batteries are charged that voltage should be somewhere in the 12.5VDC range and if you have the battery charger running it should be above 13VDC. I recommend a battery disconnect between the battery and the inverter but if you don't have one then a spark when you connect the cable is pretty normal. My biggest concern is the 11 volt reading as that indicates the battery(s) way dead! 12.0V is a fully discharged battery and in desperate need of a recharge.