My battery is like a mini car battery, but it has no indication as to how much time is left before I must charge it again. How would I tell how much time is left on the battery?
welcome to the world of Sealed Lead Acid (SLA) batteries... brings back memories.
trying to determine "time" on any battery is going to depend on the load (i.e. how much current your device draws)... so unless you know that, i don't think you're going to find an answer. For instance, it looks like your battery will last for a whopping 20 hours if you draw 0.35 amps, but only 1 hour if you're sucking 4.2 amps.
lot's of info on SLA's on the internet... one long time SLA maker is Yuasa and they have more poop than your brain can hold...
if you download the "
NP Manual - Valve Regulated Lead-Acid Batteries" from here:
http://www.yuasa-battery.co.uk/industrial/downloads.htmland go to page 12, there is a graph that will show you how to convert the voltage measured on a unconnected battery to the remaining
capacity (60%, 80%, etc)... which may also apply to your Toyo since this method isn't very exact anyway.
there is a Toyo 6FM7 datasheet here
http://www.battery-usa.com/TOYO.htm that will attempt to show you about how long the battery will last if you can determine the average current draw on that HD-P2.