Battery drain when watching TV using inverter

[Steve]

I have a Freedom 20 inverter with a 4D house battery. I was wondering how long my son can watch a 9 inch TV (while sailing) without draining the battery down to a very low level. Does three or four hours seem too long? Thanks.

 

[Brad Cavedo]

Maybe too long

what is your 4D amp hour capacity? Cut that number in half to get your usable capacity. The TV draw is probably about 15 to 20 DC amps an hour. That is just a guess, though. The Heart instruction book has a chart in it with numbers for TV and other appliances so that you can do the calculation. At 15 DC amps, you hit 45 amps consumed in 3 hours. Your TV set instructions should tell you how many AC amps it draws. To get the approximate DC amps, just add a zero to that number. You many need a second 4D to really give you the capacity you want. Doesnt a 4D have a rated capacity of about 150 amps? If so, then cut that in half to get your usuable figure.

 

[Justin Wolfe]

Not too long, but...

We have a 9". It draws about 5 amps. So you are looking a 15-20 amphours per day. That isn't much. Something your alternator can put back in less than 30 minutes. A 4D is what? 170 amphours? That means you have about 80 amphours useable capacity for a healthy battery. Doesn't sound like an issue. However, get that kid out sailing. Get him in the dinghy. Throw the boob tube in the drink. Have him steer. Have him navigate. Just a thought...

 

[Chuck Wolfe]

Get a 9V AC/DC

Get a 9 Volt AC/DC TV (or even a 13"). It is much more efficient to draw off your battery than thru your inverter. Then the 5 amp per hour draw will be correct. Going through your inverter will cost you at least 10% and the DC TV's are pretty efficient.Chuck Wolfe@innocent.com

 

[Bob Zolczer]

Try the Math

Determine how many watts your son's TV consumes (from the label on the TV). Mine (which is a 13" TV) uses about 120 watts. Divide the wattage by the voltage (12) to determine the number of amps consumed. In my example it would be 10. If the TV is run for an hour, it would consume 10 amp-hours of the battery's power. Somewhere on the battery, the battery's capacity in amp-hours is listed. This is a fast way to determine roughly what electric gizmos take out of batteries. These are approximate figures; inverters are never 100% efficient. Batteries may not be fully charged when power is taken from them and, with repeated chargings and age, may not live up to the numbers posted on them. Running the math the way I described it above is the best way I know to calculate battery power and usage. I've run my TV at anchor on raw wet consecutive days for 10 -12 hours total without draining my Group 30 deep cycle battery.