Solar Help Please

greenplasticbag · Mar 18, 2013

Hello. Can someone please assist me?

I am testing a small setup and will hopefully one day scale it up but i seem to have an issue.

I have one 20 watt panel and one 12v 12ah sealed lead acid battery. At full charge pulling 13 watts ac via a 160 watt inverter i barely get 2 hrs from my battery.

There are a few things I am unsure about. I only take the battery down to 12.10 volts closed circuit for fear of discharging too much, should it go further than this? I have been getting conflicting State of Charge data for SLA batteries online. Some site say 50% is 12.06v some say 12.30. Can someone please help?

larkspur · Mar 18, 2013

This is a deep-cycle SLA? 50% discharge is 12.06v (I just call it 12.0v in practice).

12.3v doesn't sound right - I think they are saying that 12.3 is like 50% in between 12.7 (full) and 12.0 (needs recharge). You can take it down further occasionally, but if you are dropping it below 12v on every discharge cycle then you'll lower the longevity.

Make sure you are charging the battery properly. Also remember that your inverter isn't going to be 100% efficient.

greenplasticbag · Mar 18, 2013

Thanks for you reply. Is there anything that i can use to automatically cut off the voltage after a certain point?

larkspur · Mar 18, 2013

Something like this is reasonably affordable and does a good job charging the battery properly and also has low-voltage-cutoff: http://www.solarpanelstore.com/solar-power.small-charge-controllers.sunsaver.sunsaver-6-12-lvd.info.1.html

Depending on your current method of charging the battery, you may not be getting a true full-charge. The above controller will give you a 'true' full charge (as long as it gets enough power from the panel that is : ) You can look around and find controllers that are more programmable, but they start getting more and more expensive. I encourage you to shop around a bit, I haven't used anything this small, the above is just an example I found with a quick search. Also, make sure the controller's load output is sufficient for your loads.

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Solar Help Please

greenplasticbag

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larkspur

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greenplasticbag

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larkspur

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