Inverter size?

[larry2c]

I did a search and found a few folks asking the same question but for different reason/requirements. We currently added a 200W solar system to our TT that keeps a pair of 215AH/6V batteries charged up. We've done a couple no hookup trips now with the last one lasting 4 days and what we are seeing is about A 25 - 30 amp draw when the solar isn't producing followed by the batteries returning to full charge by roughly 1PM.

With that in mind I'm thinking of getting a mid-sized inverter. I'm NOT looking to set up something that will let us plug the 30 amp TT power cord in. I want something that will let us plug into the inverter and charge up laptops or maybe run something small & short term (small TV - maybe a 12V version is a better idea?). On the outside of "wishes" would be to run the microwave for a few short warm ups each day (wife likes her "bed buddy" heated up when it's chilly).

So what size inverter would you get (or do you have) to do something like this? How much of a hit would/does it make on the batteries?

[cavie]

Originally Posted by larry2c

I did a search and found a few folks asking the same question but for different reason/requirements. We currently added a 200W solar system to our TT that keeps a pair of 215AH/6V batteries charged up. We've done a couple no hookup trips now with the last one lasting 4 days and what we are seeing is about A 25 - 30 amp draw when the solar isn't producing followed by the batteries returning to full charge by roughly 1PM.

With that in mind I'm thinking of getting a mid-sized inverter. I'm NOT looking to set up something that will let us plug the 30 amp TT power cord in. I want something that will let us plug into the inverter and charge up laptops or maybe run something small & short term (small TV - maybe a 12V version is a better idea?). On the outside of "wishes" would be to run the microwave for a few short warm ups each day (wife likes her "bed buddy" heated up when it's chilly).

So what size inverter would you get (or do you have) to do something like this? How much of a hit would/does it make on the batteries?

1st you need to decide what it is that you wish to run. You have to add up the total wattage of anything you think you want to use at the same time. then add some extra. That total is the size inverter you need.

[Bama Rambler]

The thing about inverters, is nobody has eve said that they wished they had a smaller one. While you may not want to run the entire RV load from it, having one bigger than you 'need' isn't a bad thing.

Since you say that you might want to run the microwave, I'd get one big enough to do that without any issue. I'd consider at least a 2000 watt and more likely a 3000 watt model. You can always run a hundred watts off a 3000 watt model, but you can't run a 1000 watt microwave off an 800 watt unit.

By buying a big inverter to begin with, if you decide that you have to have more power, all you have to do is buy a few more batteries and/or solar panels. However, if you buy a small one now and decide that you need more power, then you still have to buy the batteries and a new larger inverter.

[bikendan]

Originally Posted by Bama Rambler

The thing about inverters, is nobody has eve said that they wished they had a smaller one.

Well, I got rid of my 400w inverter for a 150w inverter, because the 400w shut down after only 30 minutes of tv usage.
Now we can watch tv for hours before it shuts down.

[larry2c]

Thanks all, I appreciate the comments.

So maybe I got some misinformation but I had been lead to believe that if you have a larger inverter (say 2000W) but use it for low wattage applications (like roughly 200W for the laptop charger) it is much less efficient. I have no idea how much "less efficient" really is - 10% ? no big deal 25% ? maybe a bigger deal. If the majority of what we use it for is low watt then do I just say no to the microwave?

So that's why I asked the question the way I did. Our microwave says it uses 1.35 kW so if I want to supply it occasionally, I'd go for the 2000W inverter. Of course the price of the inverter jumps quite a bit and since I can't really find anything that tells me the amount of amps using the inverter to run my microwave will take, it leaves me wondering and asking this great body of knowledge.

Last but not least, we currently don't have a TV so I don't know what the power usage is. Also, would a 12V DC TV be more efficient that running a 120V TV through the inverter.

I know, tooo many questions

[babock]

The problem is really the standby current which is the current that the inverter draws for its internal circuits whether you are drawing 100W or 2000W. For mine, that's 0.5A. A smaller inverter MAY have a smaller standby current. All inverters are a little different.

Since I wanted to power a microwave, I put in a 2000W inverter with a wired remote so I can turn it off easily when I don't need it on. I hardwired the inverter to an outlet outside my trailer so I could plug my shore power cord into it. I know you said you didn't want to do it that way so you would have to install a transfer switch of some kind. I have no room for one which is why I went the way I did.

As far as running a 12V TV vs a 120V AC TV, you are likely only looking at a 15% loss running it through an inverter plus the standby current. For me, that's negligible but I have 700W of solar and 2 Battleborn batteries.

[larry2c]

Thanks for that detail Babock

I see some inverters say they have power saver technology but they are much more expensive. I'm guessing they shut of if there is no load for some period of time?

Regarding size, you say you have a 2000W unit and you run your micro from it. That's what I was thinking too until I read this in the spec sheet of one 2000W inverter

3. Please do NOT overload. If your applications are inductive loads, please choose the inverters whose continuous power is 3-7 times higher than the watts of your appliances. such as fridge, icebox, drill, washing machine, water pump, microwave oven, oven, vacuum cleaner, hair dryer, etc. those with motor inside.

Is that just an up-sell attempt???

[babock]

Originally Posted by larry2c

3. Please do NOT overload. If your applications are inductive loads, please choose the inverters whose continuous power is 3-7 times higher than the watts of your appliances. such as fridge, icebox, drill, washing machine, water pump, microwave oven, oven, vacuum cleaner, hair dryer, etc. those with motor inside.

Is that just an up-sell attempt???

My running power for my microwave is around 800W. My Samlex inverter manual has a sizing factor of 2 where the inverter rating needs to be 2 times what the continuous running watts is.

There is a chart for this on page 17 of my manual
http://www.samlexamerica.com/documen...-0117-Lrez.pdf

EDIT: This is actually the manual of the one I have:
http://www.samlexamerica.com/documen...al_Nov2007.pdf
Says the same thing though.

[rsdata]

Personally I would just get a 400W inverter for charging batteries and watching TV... If you insist on microwave usage get a 2KW inverter/generator, like a Honda, Yamaha, or any of the under $600 options like Firman, Ryobi, or Predator.

[rk06382]

Originally Posted by babock

My running power for my microwave is around 800W. My Samlex inverter manual has a sizing factor of 2 where the inverter rating needs to be 2 times what the continuous running watts is.

There is a chart for this on page 17 of my manual
http://www.samlexamerica.com/documen...-0117-Lrez.pdf

EDIT: This is actually the manual of the one I have:
http://www.samlexamerica.com/documen...al_Nov2007.pdf
Says the same thing though.

I went thru the specs of smaller inverters. I decided to get an inverter with an auto transfer switch. I chose the Samlex EVO-2212 because it has two transfer switches. (Shore & Generator power) They also have a smaller Samlex EVO-1212F with one transfer switch. Both inverters have a surge capability of 3X their continuous power rating, allowing them to turn on loads with high starting surge.

I love my Samlex EVO-2212 Inverter/Charger, because it has a 6,600 watt surge for starting motors. I was even able to start the A/C with it as a test. It also has 100 amps to recharge my Battle Born batteries. It is like having a UPS for my motorhome.

You will need the remote to program it for lithium batteries.
No load power consumption in Power Saving Mode: <8W.

[formerFR]

first, I would drop the idea of running the microwave or the 'buddy' heater off of an inverter, unless you are really spending a lot of money and a big install to run a 'whole house' type of setup... these big draws are going to sap your two batteries very, very quickly, and 200w of solar won't be able to do anything to keep up with that.

Start easily, by simply looking at the off-the-shelf power Inverters at w*mt, in the battery/tire section, or at auto parts stores - a simple 750w to 1000w type would be a simple way to test your needs, and not a lot of cost or install requirements.
These type of power inverters can either connect via a 12v outlet, or via alligator clips directly from your batteries.
You can run an extension cord from it to whatever you want to power.

When you know how this works for you, you can then determine if you want to go the 'whole house' type of inverter route. This type of inverter requires a 'sub-panel' for the circuits you wish the Inverter to power, and must include a built-in relay in order for these same circuits to be powered when you are on Shore power or Generator... not a simple task.

[larry2c]

Thanks again for all the info folks. And Mr. Turner, I think I will be following your suggestion - get an inverter that will handle our charging & future TV and see how it plays out.

Just some info for those who haven't heard of a bed buddy (not the faithful dog), it's just a big "sock" with buckwheat kernels in it. You zap it in the microwave for a couple minutes and it gets warm and holds the heat for close to an hour. DW likes it over her shoulders when it's chilly - keeps the stiffness at bay for a while.

[Hclarkx]

I run a microwave from a 900W inverter. The trick is to use a Panasonic inverter microwave ($120). Instead of switching between full on (1300W) and full off (0W) when set for lower heat, the power input drops but remains steady. Using the microwave on level 5 requires about 700W. We simply dial in level 5 and set the timer for twice normal. Or level 4 or 3 depending on what we are heating and how quickly we want it done.


The 900W inverter also powers our espresso maker which says 1200W on the bottom but actually draws only 1005W. The 900W inverter has enough overload capability to make four shots of espresso.



A cheapie toaster draws 750W so works fine.


Needless to say, we use these three appliances only sequentially. That's a bit of a nuisance, but we've gotten used to it.


This 900W inverter draws about 9 watts when running unloaded, but we have a remote control on it and switch it off when it's not needed. If the days are sunny, we worry less about it running unloaded.


Like all inverters, it will kick off if the battery voltage gets to low. Around 11.5V if I recall correctly. That got to be a nuisance when the lead-acid batteries got older (a 900W load would drop the voltage to 11.5 even before the battery got down to 50% charge). We now have LFP so that's no longer an issue.


We were so happy with the inverter microwave that we got one for our bricks home. It's far more effective at defrosting and cooking on lower heat than the ones that switch on and off.