# Solar battery draining too fast

I have a Bosch L5077 180 Ah, 12 V deep-cycle sealed Pb battery for my solar setup. I bought it recently (two weeks ago) but since the weather was rainy the last two weeks, and the solar panels didn't produce any significant power, I keep charging it on-grid with a 10 A, 3-stage smart charger.

Assuming that this battery has a capacity of 180 Ah which is around 2 kWh of energy, the battery is almost fully drained (11.3 V) before even consuming 1 kWh or so.

So, in six hours of usage which usually reaches the threshold in which the inverter shuts down, I'm using a 43", 50 W LED TV, one 32" 35 W LED TV, a laptop charging (60 W/hour) and a few home LED lights now and then.

With a quick calculation we have:

• 43" LED TV 50 W x 6 hours = 300 W
• 32" LED TV 35 W x 6 hours = 210 W
• Laptop charger 60 W x 6 hours = 360 W
• Inverter 1500 W consumption, let's say 30 W x 6 hours = 180 W.
• Lights, which shouldn't be more than 100 W total in those 6 hours, as I don't use the lights much.

The result is 1050 W of energy consumed and the battery is fully drained.

Where did the rest of the 85 Ah go?

The charger is always charging the battery fully; when the battery is freshly charged it will show a value of 13.6 V on the PWM charger; 2 hours later it shows between 13.4-13.5 V so I guess the battery can't be damaged so soon.

Any ideas?

• Have you accounted for DC/AC conversion efficiency of the inverter under the load of your use case? Nov 21, 2019 at 23:23
• How to do that ? I have no idea how much the inverter draws in standby or under load. It mentions nothing also in its manual. Nov 21, 2019 at 23:37
• the battery is probably rated at 9 A over a 20 hour discharge interval ... for example, if you draw 45 A, then the battery will last less than 4 hours ... refer to the datasheet, if you can find one (i could not find it) Nov 22, 2019 at 1:08
• How do you know the various loads? Especially the power for TVs will vary considerably depending upon usage - in particular the backlight intensity setting. I don't think you can conclude much unless you actually measure the current being taken from the battery. Nov 22, 2019 at 1:41
• take a gander at this e-education.psu.edu/eme812/node/738 Nov 22, 2019 at 1:43