<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Shane, <div class=""><br class=""></div><div class="">Thank you for the great information. Based on this, and my desire to see how long this run-down test will last, I will program the Arduino to shut down the test at 11.9V. Going forward, to extend the life and account for temperature effects, I will need to be more conservative. </div><div class=""><br class=""></div><div class="">One of the advantages of the Adafruit Solar option was I could use their charge controller and all I had to do was regulate the voltage and measure the battery’s % charge. In this setup, I will need a 12V panel and a new charge controller circuit. I found one <a href="http://www.electroschematics.com/6899/12v-ldo-solar-charge-control/" class="">here</a> but please let me know if you can recommend anything better.</div><div class=""><br class=""></div><div class="">Thanks again,</div><div class=""><br class=""></div><div class="">Chip</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><div><blockquote type="cite" class=""><div class="">On May 29, 2015, at 8:25 PM, Shane Trent <<a href="mailto:shanedtrent@gmail.com" class="">shanedtrent@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Chip,<div class=""><br class=""></div><div class="">The end point voltage of a sealed lead acid battery is a little arbitrary. The point is that you are reaching the point that there is little usable energy left in the battery. At very light load you could keep running longer but you will be reducing the number of cycles you can get out of the battery in it's operating life. </div><div class=""><br class=""></div><div class="">At moderate to heavy loads the battery voltage will generally recover once you reach your cut-off voltage and remove the load. But when the voltage recovers, the battery still contains very little energy and will quickly drop the voltage under load.</div><div class=""><br class=""></div><div class="">The East Penn Manufacturing (I love their batteries, sold under many names including Energizer at Sam's Club) documents below show the battery capacity remaining at specific open circuit voltages. They show 0% at 11.80 volts. A table in the other document shows that stopping 12:00 volts would extended your AGM battery expected life by over 33% (450 cycle at 100% depth of discharge to 650 cycles at 80% depth of discharge. </div><div class=""><br class=""></div><div class="">Another issue often missed is that battery terminal voltage, charging voltage and capacity all vary with temperature. So lab measured battery operating time will probably not be matched in the field. Be conservative. But it sounds like your solar cell is going to be giving your battery much more power that you will be needing. If you hit only 50% depth of discharge, your battery should last for 1000 cycles or around 3 years. Cut it to only 25% depth of charge an you stretch the battery life to 6 years. </div><div class=""><br class=""></div><div class="">Great technical reference about AGM and Gel batteries</div><div class=""><a href="http://www.soligent.net/uploads/products/32669_3.pdf" class="">http://www.soligent.net/uploads/products/32669_3.pdf</a><br class=""></div><div class=""><a href="http://www.eastpennmanufacturing.com/wp-content/uploads/Guide-to-Commercial-VRLA-Batteries-2007.pdf" class="">http://www.eastpennmanufacturing.com/wp-content/uploads/Guide-to-Commercial-VRLA-Batteries-2007.pdf</a><br class=""></div><div class=""><br class=""></div><div class="">I hope the information is helpful!</div><div class=""><br class=""></div><div class="">Shane</div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Fri, May 29, 2015 at 8:04 PM, Chip McClelland via TriEmbed <span dir="ltr" class=""><<a href="mailto:triembed@triembed.org" target="_blank" class="">triembed@triembed.org</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="">To all, <div class=""><br class=""></div><div class="">Taking your collective advice, I have been testing a sealed lead acid battery with my cellular data logger. It has been dutifully sending updates to Ubidots hourly for almost three weeks now. Here is a <a href="http://app.ubidots.com/ubi/getchart/page/fwweXqpV5QlRbiZ8nzEvou4nNi8" target="_blank" class="">link to the current voltage</a> of the <a href="http://www.amazon.com/UPG-UB1280I-Sealed-Lead-Batteries/dp/B0009GIKNE/ref=sr_1_1?ie=UTF8&qid=1432943993&sr=8-1&keywords=UPG+UB1280I+Sealed+Lead+Acid+Batteries" target="_blank" class="">12V battery</a> that has been running things.</div><div class=""><br class=""></div><div class="">The question is, when do I stop the test? I have read different articles stating that these batteries should be discharged only to 11.9V (but, this is a 12V battery - albeit one that started at 13.1V at full charge) and others that say that a full discharge is OK as long as you recharge the battery quickly. </div><div class=""><br class=""></div><div class="">Any advice would be appreciated.</div><div class=""><br class=""></div><div class="">Thanks, </div><span class="HOEnZb"><font color="#888888" class=""><div class=""><br class=""></div><div class="">Chip</div></font></span><div class=""><br class=""></div><div class="">P.S. - the <a href="https://twitter.com/chipmc86/status/604435703653658625" target="_blank" class="">LiPo Solar version </a> s now ready to make it’s public debut on the Greenway trails. </div></div><br class="">_______________________________________________<br class="">
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