Plugging shore power into inverter
I'm about to buy an inverter for my travel trailer. It has no 12 volt outlets, so I think ac is the easiest way to go. Can I plug the shore power plug (with an adapter) directly into the inverter an...
Forum Discussion
JRRNeiklot wrote:
At 900 watts, the microwave will draw 7.5 amps if used for 6 minutes(by my math). That's probably more than I will use it in a day. But yeah, it will require a larger inverter.
It will draw 7.5amps if it's on for 1minute or 1year (assuming it doesn't fail or something odd happens).
A big issue you need to look at is how many amp-hrs you draw and how that impacts:
- Battery Bank Size
- Charging System
Take your microwave running at 900watts, it draws 7.5amps for 6min. That translates as 7.5amp-hrs (7.5*6/60*120/12: Divide by 60 to change minutes to hours and 120/12 to convert 120v to 12v)
By itself that's not too bad but you need to run the same calcs for every item you expect to use (both 120vAC and 12vDC) and add them up.
Every device should have wattage or amps on the UL lable. Divide watts by the rated voltage to get amps. You will have to guess on the time duration.
Add those up and that is how many amp-hrs you need to supply.
Then you need to determine how many days you want to go between charging (even with solar, it's good to assume 2-3 days as you will get minimal charging during cloudy days).
Your battery bank amp-hr rating should total 3-4times the total amp-hrs you come up with. The reason being is if you drag battery bank much below 50% charge it significantly shortens the life of the batteries.
Charging can come from many sources.
- If you will plug in, the trailers charger is probably fine.
- If you run a generator, you need to figure out how much time is worth the effort. After 80-90% full, batteries absorb charge much more slowely, so completely filling them takes an exceedingly long time (another reason to get a bank that is rated at 3-4 times the size you calculated)
- If you go to solar or wind, you need to factor in when the weather does not cooperate, so they should be able to put out more than you need in a day in case the first day had negligible output and the second day is trying to catch up.
Reality there are some efficency losses when you convert back and forth and store in the batteries but if you size for 3-4times your need for 2-3days worth of use, you typically have enough fluff that it isn't important.
