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

Carianne

New Member
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

Super Moderator
Most Helpful Member
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

Well-Known Member
Most Helpful Member
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

Active Member
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

New Member
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

New Member
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

Active Member
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

New Member
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

Well-Known Member
Most Helpful Member
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

New Member
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

Well-Known Member
Most Helpful Member
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.
 

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