Power inverter over voltage issues

**ConstantNRG** · 11-07-2009, 04:44 PM

Hello all,

I have tried to install a power inverter today and am facing a frustrating issue.

The inverter has a built in over voltage shutdown which is supposed to be at 15.5v +/-.75v, but the problem here is that its shutting down at 14.8v

My truck, a 2008 silverado is supercharged, and runs a little high (14.8 is its highest), but once it warms up is about 14.3 or so, which is fine but for the 10 minutes before that i cant deal with the inverter shutting down due to the "over voltage"

Ive been searching high and low for a solution over the past 4 hours and have gotten frustrated so i stopped.... for now.

Anyone have any ideas on how to regulate the voltage down a little bit? All my other electronics run fine on the system, but this inverter is going to be the death of me!

HELP!!!!!!!!!!!!

**Bugbyte** · 11-07-2009, 10:31 PM

Use an inverter without over voltage protection. Alternatively, use a DC-DC power supply.

**ConstantNRG** · 11-09-2009, 03:26 PM

Thanks bugbyte for your quick answer and on a side note i have a project I've been working on that you may take some interest in, but that's a post for a different time. And yea I'm a loping time reader first time poster.

My main problem here is that I've tried 3 different inverters and they all have the same damn overvoltage protect, and I really do t feel like changing inverters any more but this is starting to bug me. I've done some research on this for the past few days and can't seem to find anything to stepdown this voltage. I'm only trying to power a LCD monitor which is 28 watts but I'm having no luck.

Hopefully someone has an idea on how to accomplish this stepdown so I can get this project moving along, maybe a dc-dc stepdown or someway I can reliably get this below 14.8 to like 13

**smartass365** · 11-09-2009, 06:39 PM

what about just a big diode to step it down .7 volts or so?

**soundman98** · 11-09-2009, 08:39 PM

honestly, i think you would be better off getting a m1/m2 dc-dc power supply-- any solutions i can think of are not any more cost effective(a large amount of 1 watt ceramic resistors?) and are possibly even less reliable.

**pulsarsimon** · 11-10-2009, 04:09 AM

I second the diode idea... a big power diode in series with the 12V (or 15 in your case) to the inverter will drop about 0.5 to 0.7 volts - plenty to solve your problem.

**smartass365** · 11-10-2009, 05:11 AM

Just keep in mind, that wherever there's a voltage drop, there's power dissipated.

Voltage*Current=Power

So depending on how much power you plan on using, this might be a viable option.

I would personally go with an intelligent psu. I've been seeing m1-atx's go for 25 bucks on ebay, along with all the other supplies sharply dropping in price. Unlike inverters, many of them can approach up to 90% or more efficiency.

**ConstantNRG** · 11-10-2009, 07:59 AM

Well, considering I'm powering a relatively small 400 watt power inverterwhich will only have a load of the LCD monitor which draws 28 watts I don't think I should have too much of a power issue so on that thought I'm thinking that the diode idea would be a safe bet. I've looked at the dc-dc power supply but given the LCD monitor I'm working with I'm going to wind up over complicating things going that way. At least so far as I can figure.

So please forgive my ignorance on this but can you point me to the right type of diode? I've seen plain 3a silicon diodes from like radio shack but I don't feel like frying anything so I figure I'd be safer to ask haha

thanks again for all of your help on this and someone remind me to put up a post of what this whole project is because I think it's something that you will all find pretty interesting.

Thanks!!!

**smartass365** · 11-10-2009, 01:23 PM

http://www.reuk.co.uk/Zener-Diode-Voltage-Regulator.htm

this is a good site that explains basic zener regulation and has a calculator.

as far as just a single diode, any general purpose silicone diode with high enough ratings will work.