Expert: Chuck Marken - 7/7/2001

Question
I recently purchased a 12volt, 75Amp, 100Min. capacity Deep Cycle battery. I plan to trickle charge it from a 10.5watt, 650mA, 17volt, solar panel. I will power a small shed in my yard.  Fluorescent lights, an outdoor nightlight, and a workbench outlet. I purchased a 300watt power inverter that hooks directly to the battery. The power inverter has the following stats:
Max. Continuous Power - 300 watts
No Load Current Draw - 0.4A
Input Voltage Range - 10 - 15 Volts DC
Now for the question. I hooked the power inverter to a typical automotive battery and it worked fine. I then hooked it to the deep cycle battery and it fried. I mean smoke, heat and toasted.
I returned the inverter and exchanged it for another one. Before I hook the new one back up I would like to know if it's possible that the inverter is mismatched to the battery. It's hard to understand why however, because this hookup is typical for any marine/solar/etc. use. There is a strong possibility that the inverter was faulty. It was purchased at a store that typically sells factory refurbished equipment at low prices. But that doesnt explain why it worked on the automotive battery just prior to hooking it to the deep cycle battery.
Your answer is eagerly awaited.
Thank you in advance.

Answer
AJ,
What you describe in the inverter hookup to the deep cycle battery is normally caused by the wrong polarity, ie. neagtive inverter terminal to positive battery terminal. This will always fry an inverter just as you describe, smoke, burning smell etc. The only other possibility is a faulty inverter. There is really no such thing as a battery mismatch when using 12 volt lead acid batteries and 12 VDC inverters (lead acid car and deep cycles are basically the same except for plate design in the deep cycle that allows for deep cycling not affecting the battery life as much). Be double careful when hooking up the terminals and make sure the positive goes to positive and negative to negative. It is really easy to hook them up wrong and I have seen professional electricians do this more than once at a cost that sometimes is hundreds of dollars.

A bit of advise. The inverter has a no load current of .4 amps - rather high in inverter specs. This means that with nothing on, the inverter will draw almost 10 amp hours in a 24 hour period and take the 75 amp hours battery to a 80% depth of discharge in 6 days - without powering a thing! With an inverter like that it is best to switch the inverter completley off when no power is required. Most inveters have  an on/off switch that allows you to do this.
Hope this helps
Chuck