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post #1 of 13 Old 10-21-2019 Thread Starter
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Inverter drains batteries

This might be to complicated a question with not enough details but here goes:

I bought a Catalina 36MKII last year. Original charger/inverter. One group 24 lead acid house battery.

The inverter, with just a modern 22 inch flat screen TV would drain the batteries in an hour. (the flat screen is the only 110 volt bit I have on the boat). I assumed it was the battery, intended on replacing with 6 volt X2 this spring.

One thing lead to another and I spent a boat load (pun intended) in new electronics this year so I went cheapo and bought cheapo 2x lead acid "deep cycle" group 24 batteries for the house bank.

Inverter still won't run the TV for more than an hour without draining the house bank.

Any ideas for this electrically challenged person who is scared to sick a marine pro on it at 120 per hour only to find out I need a new inverter anyway????

WINDHOVER
1999 CATALINA 36 MKII
NOANK, CT
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post #2 of 13 Old 10-21-2019
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Re: Inverter drains batteries

How many watts does the TV draw? Most websites I have found estimate that a 22 inch LCD TV will draw between 30 and 40 watts. So that means calculating power as P = E*I, E being voltage and I being current a draw of between 0.25 and 0.33 amps at 120 volts slightly higher at 110 volts 0.27 and 0.36 amps. With 100% efficiency on an inverter this would give you a range of 2.5 to 3.6 amps for your draw, depending on what your inverter puts out, also no inverter is 100 % efficient, this is also assuming the nominal 12 volt dc . Your TV on for an hour is akin to your VHF transmitting continuously at maximum allowed power of 25 watts for an hour and thirty six minutes. How many amps does your battery bank have in reserve after you take out your normal load? Also realize that the TV is a fairly constant load for power drain and will tend to draw more amps from the batteries as they draw down.
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post #3 of 13 Old 10-22-2019
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Re: Inverter drains batteries

I have a 1000 watt Xantrex inverter. I don't use it for anything continuous. My NUC computer runs an 20" HP LCD monitor and both run off a (inexpensive) buck 12v > 19v transformer. However the inverter does seem to drain the batteries which is why I use it very rarely... and mostly for charging power tool batteries. Mobile devices are charged from USB outlets wired to the 12v system.

I gave the TV away because we prefer content from the www... YouTubes and so forth we stream with a mobile hot spot on the cell phone. We're now used to very large screens (at home) so the 20" seems ancient.

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post #4 of 13 Old 10-22-2019
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Re: Inverter drains batteries

The inverter has it's own draw, in addition to the TV. Some refer to that as inefficient power inversion, but I like to think of it this way.

A group 24 battery is pretty small and more often used as start batteries than house bank. Usually only 80ish amp hours, so only 40 usable. I hope you didn't "drain" past that. That capacity also declines naturally with time. Further, unless you have a smart three stage charger, with a shunt to monitor charge amps, there is little chance you're anywhere near full charge capacity to start with. The useable range starts to squeeze.

If you're not actually using the inverter, do you shut it down? An active inverter can draw nearly an amp, just waiting to invert. That is more than half your capacity per day. Is anything else drawing on your batteries?


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post #5 of 13 Old 10-22-2019
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Re: Inverter drains batteries

As much as possible, where energy efficiency is a concern, select components and appliances that do not require an inverter.

There are DC powered TVs

And of course monitor screens, which an extra add-on gadget turns into "a TV", all of which are native DC internally.
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post #6 of 13 Old 10-25-2019
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Re: Inverter drains batteries

My main inverter uses 5 amps DC just turning it on!

For the TV I have a little 300 watt inverter and the combo of it with the TV and sound bar running only uses about 5 amps DC.

Having a smaller 300-400 watt inverter is worth it to run these small loads (they are only around $20-30).
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Last edited by Don L; 10-25-2019 at 12:00 PM.
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post #7 of 13 Old 10-25-2019
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Re: Inverter drains batteries

Those are some pretty big ass inverters there!
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post #8 of 13 Old 10-25-2019
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Re: Inverter drains batteries

As someone else mentioned, I too got out of the need to invert to watch a movie on TV. Itís not only energy inefficient, but the permutation of switches to make it work and, more importantly, shut it back off so it doesnít drain all night, was a PITA. When we invert, it powers every 110v receptacle in the ship. Especially a problem, when the youngins wanted to stay up later and never shut down quite right.

It was a bit pricey, but I bought a Jensen 12v TV. Great picture. Best money I ever spent on a TV, which Iím not even a very significant user. RV and Trucker sites have lots of 12v selection, but be warned that most are pretty lousy. This seems to be a top brand and is engineered to accept the various voltages that a 12v bank is going to throw at it. Super low draw.
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post #9 of 13 Old 10-25-2019
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Re: Inverter drains batteries

We do like Don does - use a little 200W inverter to power the TV. We just hard wire this into the DC system on a breaker labeled "TV", and turn it on/off as needed just like any other DC circuit.

These inverters are pretty efficient for the small current they need to provide. Our 28" Smart TV powering a connected hard drive and its wifi only draws 3A through the inverter. Any invert inefficiencies are in the milliamp range, and if once can't spare 1Ah for 10hrs of TV time, then one probably shouldn't be using a TV at all.

The problem with 12V TV's besides high price and weight, is that they just can't compare to the 120V offerings. Today's 120V TV's are available in unlimited sizes (although it is getting difficult to find them under 24"), will wirelessly stream off the internet or computing device, have a built-in media hub, connect to our on-board media router, take a USB hard drive full of movies, and several other useful features. Our 28" does all the above and only cost $120.

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post #10 of 13 Old 10-25-2019
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Re: Inverter drains batteries

Don't know why you went 'cheap' with 12v batteries. Last time I checked at Costco you could get 6v golf cart batteries for around a $100 each. 225ah @ 12v of REAL heavy duty deep cycle storage for $200 is pretty damned cheap. You can pay more for GC batteries but not sure you are getting much more for the extra money.

To get the longest life out of L/A batteries 50% discharge is recommended. Discharging beyond that won't kill them instantly or even quickly, however. May work out that the best cost/life/capacity reality for L/A batteries is a deeper discharge and a slightly more often replacement. Discharging a battery to near flat or flat will severely effect battery life. Taking it down to 25%/12v might be a good tradeoff.
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