Artum.....Good questions......Good ideas......BAD math, though I think you'll be happy with the outcome.
265 watts of 120 volt AC power does not equal 265 watts of 12 volt DC power. Since you're concerned about the battery capacity, look at the specs for the 600 watt AC inverter you're wanting and see what DC load it takes to produce that AC power. Divide that DC amp load into the amp hour capacity of your Group 27's and I think you'll find you're good to go!
A good rule of thumb to use is to not discharge batteries below 50% capacity to keep from abusing your them. Also, remember to figure in some lights and heater usage in your calculations.
Actually 265 watts of 120 volt AC does not equal 265 watts of 12 volt DC--because of inefficiencies in the inverter it is more like 295 watts of 12 volt.
A nice "rule of thumb" is to divided the watts by ten to get the amp hour draw--so 265 watts will translate to 26.5 amps on the DC side.
The greatest capacity I can find for a group 27 is 105 amp-hours. So he can watch TV for four hours before hitting the 50% state of charge--leaving no margin for any other power use.
23mikey wrote: Artum.....Good questions......Good ideas......BAD math, though I think you'll be happy with the outcome.
265 watts of 120 volt AC power does not equal 265 watts of 12 volt DC power. Since you're concerned about the battery capacity, look at the specs for the 600 watt AC inverter you're wanting and see what DC load it takes to produce that AC power. Divide that DC amp load into the amp hour capacity of your Group 27's and I think you'll find you're good to go!
A good rule of thumb to use is to not discharge batteries below 50% capacity to keep from abusing your them. Also, remember to figure in some lights and heater usage in your calculations.
Happy Camping!
Mike
Regards, Don
Kustom Koach Class C 28'5" 256 watts solar, 875 amp hours in two battery banks 12 volt batteries 2500 watt inverter.
pianotuna wrote: The greatest capacity I can find for a group 27 is 105 amp-hours. So he can watch TV for four hours before hitting the 50% state of charge--leaving no margin for any other power use.
Group 27 Everstart(walmart) is 115 and Costco 27 is 115 amp hours.
But it sounds like two hours is doable.
Some LED lights or a battery lantern would go a long way compared to running a couple incandescent lights while the show is on.
I chose to simply run wire from my inverter to my shore cord power box with an outlet for the shore power cord--and turn *off* the converter breaker. It's simple, cheap, and fool proof. It allows the inverter to be located very close to the batteries, minimizing line losses.
I really doubt that most alternator charging systems are able to "top up" a battery bank in four hours (200 miles @ 50 mph), particularly if we assume 210 amp-hours of capacity for the group 27 battery bank. My stock charging system in the RV was fused at 60 amps, and came with relatively puny wire. In the first hour of driving or so, the best this normal RV charging system might do is 60 amp-hours--but only in the "window" from 50% to 80% state of charge. It may take 5 to 6 additional hours of driving to get from 80% to 100% state of charge.
I agree with smkettner--2 hours is doable.
Artum Snowbird wrote: snip
I am looking at a draw load of around 25 amps from the DVD and TV. and keeping this load going for a few hours... then getting it fully recharged driving the next day for a couple hundred miles.
Any reason to put in an inverter more than 600 watts?
Actually 265 watts of 120 volt AC does not equal 265 watts of 12 volt DC--because of inefficiencies in the inverter it is more like 295 watts of 12 volt.
A nice "rule of thumb" is to divided the watts by ten to get the amp hour draw--so 265 watts will translate to 26.5 amps on the DC side.
Good point -- as voltage in the battery decreases, the amperage will increase so just dividing by 12 is a little optimistic.
As Ohm's said - "this ain't just just my opinion, it's the law!"
Yup, at 115 amp hours (I usually figure G-27's at 100) you have around 500 watt hours per battery... So.. if the TV is 200 watts. that's 2.5 hours. Something else.. You do the math. More batteries = more time. bigger batteries = more time. More "Stuff" (IE: Sat receiver, DVR, etc) = Less time.
Nothin adds excitment like something that is none of your business
Kenwood TS-2000 housed in a 2005 Damon Intruder 377
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