Inverters

[Burtonair01]

Re: Inverters

I agree that two 12volt batteries will not last very long(maybe a day) if you're running that microwave around an hour a day and that coffee pot 1-2 hours a day. Given those batteries already have some draw on them. We've got a 2,000 watt inverter that runs a 46" tv, full size refrigerator, and some fans, lights, and a coffee pot. We have 6 6 volt golf cart batteries wired in series to get 12 volts and they will last 12 hours if we use our appliances moderately. You could give it a try and see how things go, no problem in getting another battery. Our inverter also has a built in switch that automatically switches from shore to inverter power when it looses shore power and also charges the batteries(110 amp built in charger) when we go back to shore power.

The inverter should have instructions that will tell you what gauge wire to use on the D/C side. We just have normal 12 gauge on the A/C side but ours is only 2,000 watts.

What brand inverter do you have? Sounds like thats the one I should have gone with, the switching back and forth atoumatically sounds like a real nice option. I'm sure we won't be using it very much really, just brew a pot of coffee in the morning and maybe nuke some lunch once in awhile and we will be running the motor often enough that we should'nt be running the batteries down, I hope!

 

[bruceb58]

Re: Inverters

Just a thought, but if it were me (and it will be down the road), I'd be looking at a 1500W unit to supply what I need and simplify the install. It'll provide more than 11 amps output and operate everything you have in mind.

Depends on the continuous operating specification. Also, I believe the spec for the 2500W is the output wattage...not derated by efficiency. So if you have a 2500W model the amp output is 2500/110 = 22.7A. The input is where you need to derate. The input current is 2500/12.5/.85 = 235A.

 

[Jeepster04]

Re: Inverters

What brand inverter do you have? Sounds like thats the one I should have gone with, the switching back and forth atoumatically sounds like a real nice option. I'm sure we won't be using it very much really, just brew a pot of coffee in the morning and maybe nuke some lunch once in awhile and we will be running the motor often enough that we should'nt be running the batteries down, I hope!

Its an Exide inverter. Far as I know its over 5 years old(was on the boat when we got it) but Exide no longer makes inverters since they sold that section I believe. There are many other inverters out there that function the same as ours. This type of inverter is pretty expensive though, it can go well over $1,000.

Here are some examples:

http://www.westmarine.com/webapp/wc...toreNum=10109&subdeptNum=10544&classNum=11281

http://www.westmarine.com/webapp/wc...toreNum=10109&subdeptNum=10544&classNum=11280

I really like this one, the warranty sucks though:

http://www.xantrex.com/web/id/50/p/1/pt/7/product.asp

Depends on the continuous operating specification. Also, I believe the spec for the 2500W is the output wattage...not derated by efficiency. So if you have a 2500W model the amp output is 2500/110 = 22.7A. The input is where you need to derate. The input current is 2500/12.5/.85 = 235A.

You are correct. Its 2500 watts on the A/C side.

 

[bruceb58]

Re: Inverters

I was just doing my calcs on the DC side assuming 12.5V 2500 watts and .85 efficiency.

217A x 12.5V only gives you 2300W and that isn't taking into account efficiency. If you are truly drawing 2500W, its much higher. Once the battery voltage starts dropping , the current will be going up even more.

 

[This_lil_fishy]

Re: Inverters

So you are saying you can only get 1000 watts out of your 3500 watt inverter?

Just going by my experience with our inverters. Now it could be that the battery isn't handling the load thus tripping the inverter. More then likely though our inverters are rated at 3500w peak and closer to 1000 maintained, and the breaker isn't tripping fast enough to prevent the fault. I stopped using it anyways, as the constant dead batteries got to be a pita whenever I forgot to turn the inverter off. Keeping in mind, my inverter had a very high draw even without a load on it....

Ian

 

[Jeepster04]

Re: Inverters

I was just doing my calcs on the DC side assuming 12.5V 2500 watts and .85 efficiency.

217A x 12.5V only gives you 2300W and that isn't taking into account efficiency. If you are truly drawing 2500W, its much higher. Once the battery voltage starts dropping , the current will be going up even more.

Yeah thats my bad, I was thinking of something else. 2500/12.5volts=200amps D/C or 235amps with the 85% efficiency.

 

[bruceb58]

Re: Inverters

Just going by my experience with our inverters. Now it could be that the battery isn't handling the load thus tripping the inverter.

That could be especially if the wiring is on the smallish side. Could get an undervoltage fault before the circuit breaker can react to the current.

 

[NYBo]

Re: Inverters

Think it would be ok in the motor compartment or is it too hot in there?

NO!!!

While the heat would be a problem, the biggest concern would be going kaboom! Inverters aren't spark-protected AFAIK. Read here for installation tips.