Why would deep cycle 100ah battery drain down in 6.5 hour with a 1.4 amp load?

[Carianne]

Why would my 105ah deep cycle battery drain down in 6hrs when my load is only 1.4amps?

Goal: To have lights run for 2 days -10hr/day

I have: 12 led bulbs (each bulb is 14w/120v/60Hz/115mA/5000K) on 4 tracks

Plugged into a heavy duty power strip(my test was done using only three tracks/9 light bulbs with a heavy duty 3 way)

Plugged into a Zamp pure sine power inverter 300watt continuous power/600w surge power (model zp-300ps).
Input: 12v normal (10-15) DC
Output: 120 vac ay 60hz

Note: I cut off the clips, stripped the wires and attached ring terminals to the inverter wires for a better connection

Connected inverter to a NAPA (part 8231) 100ah deep cycle Marine/RV premium battery BCI No.31 MCA @32F(800) CCA @0F(650)

From my calculations to find my draw and the same readout from my killawatt meter, my draw should be 1.4 amps. I plugged the killawatt meter into the inverter and plugged my lights in as well just to double check to see if that changed the load , but it was nominal.

I don’t understand what I’m doing and/or calculating incorrectly, or perhaps this is just the way it works!

This is my first foray into this and I’ve read a lot, but then just dove in and tested it. I’m out of my realm now with troubleshooting!

What I don’t get is most people are trying to run appliances with this setup!

Can anyone see what I’m doing wrong?

Thank you for the help!

 

[Nigel Goodwin]

I don't know where you're getting your readings from, but 12 x 14W bulbs is 168W - 100A battery x 12V is 1200W - so assuming 100% efficiency you get about 7 hours life.

Running appliances depends entirely on the appliance, and how long you run it for - I presume you're talking small fridges?.

Buy why on earth would you want 168W of LED lighting?

 

[alec_t]

Welcome to ETO!
9 x 14W = 126W, which equates to about 10A draw from the 12V battery by the inverter (if it were 100% efficient). Even if you ran the battery dead flat (which you should never do) it would last only 100Ah/10A = 10 hours.

 

[Ylli]

That 1.4A is the current draw of the LEDs at line voltage of 120 VAC. On the 12 volt side, that translates to a current draw of about 14 amps if you have 100% efficiency. Let's be generous and say your inverter has an efficiency of 80%. That would make the current draw from your 12 volt battery 17.5 amps.

A 100 Ahr battery will deliver 17.5 amps for 100/17.5 = 5.7 hours.

 

[Carianne]

Wow! I was way off!

Ah, so
1. My killawatt meter read my draw incorrectly.
2. I calculated 14/120=.11666667. Then .12 x 12=1.44.

Doesn’t one use a killawatt meter to test what kind of load you have?

 

[Carianne]

All I was trying to do is set up lighting for an art festival that has no electricity! It seemed easy. I guess I could just not use all of my bulbs and that would solve the issue! Or get different light bulbs.

 

[Ylli]

Ah, so
1. My killawatt meter read my draw incorrectly.
2. I calculated 14/120=.11666667. Then .12 x 12=1.44.

Doesn’t one use a killawatt meter to test what kind of load you have?

Yes, your meter was reading correctly. You were drawing 1.4 A from the 120VAC source. 1.4A from a 120 VAC source is 168 watts. (P = E*I).
Rearranging the above, we can see that I = P/E. So 168 watts from a 12 volts source is 168/12 = 14 amps.

 

[Carianne]

Thanks to all! I completely understand where I went wrong, thanks to your explanations! I know there should be some other solution, but for now I will just use four bulbs. I just don’t understand how anyone can use these setups to run appliances in an RV!

 

[Pommie]

As already mentioned 168W of LED lighting is a very large lighting display. Do you have a picture of link to the LEDs being used?

Mike.

 

[Carianne]

I don’t have a pic, but they are 14w. I just attended a festival this weekend and my neighbors had 3w LEDs, so I’m definitely changing my bulbs out.

 

[Pommie]

If you're going to change the LEDs then you could switch to the 12V 6W downlights and run them direct from the battery. More efficient and safer.

Mike.