Edd, Amp-Hour capacity is a moving target. For lead acid batteries, it depends on the amp draw. This is because the battery internal Resistant consumes power at a rate squared to the current draw (I^2 R power lost). It is common to rate deep cycle batteries at a 5 amp draw.
You could run your own 5 amp test with simple volt and amp meters and get a reasonable idea of the battery capacity. Start off with a full charged battery and turn on loads until you get about 5 amps. Measure how long it takes until the battery voltage gets to 12.0V (which is the 50% capacity voltage). Take your time in hours multiply by your current draw and then multiply by 2. Do not run a lead acid battery below 12V. Of course, there are much better ways to measure capacity. A simple $15 watt meter works well too. I have one of these from Amazon https://www.amazon.com/gp/product/B01GZXWH7E/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 <https://www.amazon.com/gp/product/B01GZXWH7E/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1>. I use Anderson power pole connectors which allows me to insert this meter virtually anywhere. For example, I have used it measure the amp-hrs used by my refrigerator (25 amp-hrs/day in July) and more recently to measure the amp-hrs used by my SSB. Power pole connectors are great. Look them up if you are not familiar with them. I have also heard great reviews on this $40 battery meter. It does not have Bluetooth and a phone app that the $200+ meters have, but the DIY off grid solar folks love it and swear by its accuracy. This meter is a true charge discharge meter whereas other cheap meters I seen go only one way. https://www.amazon.com/dp/B07CTKYFTG/?coliid=I28MK0USN5TE67&colid=4DEXPPL436LK&psc=1&ref_=lv_ov_lig_dp_it#customerReviews <https://www.amazon.com/dp/B07CTKYFTG/?coliid=I28MK0USN5TE67&colid=4DEXPPL436LK&psc=1&ref_=lv_ov_lig_dp_it#customerReviews> I’m a big fan of quality item like Victron products but I don’t shy away form affordable solutions too. - Paul E. 1981 C&C Landfall 38 S/V Johanna Rose Fort Walton Beach, FL http://svjohannarose.blogspot.com/ > On Jan 27, 2020, at 6:36 PM, cnc-list-requ...@cnc-list.com wrote: > > Listers, > > Hope everyone had a great New Years. > > So when you buy a battery, it?s pretty clear from the label what it?s Amp > Hour rating is ? so how does one actually verify that information? Is there > any way to test your battery?s actual Amp Hours when they are either new or > used for some time (but fully charged)?? > > All the best, > > Edd
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