Battery voltage...

Tim120

Tim120

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As far as I'm aware I have two lead acid 100 or 120 amp/HR leisure batteries , not sure that has any relation on my question which is...
What voltage is safe to let them drop to?
Readings gradually fall from 12.8 or above to 12.2 when I'm informed via an internal panel leisure batteries are fair/poor.
What is the collective wisdoms opinion?
 
lots of these charts around with variations on the numbers. This one is pretty good for standard Lead-Acid batteries and includes a nice description as well :)
battery-charging.jpg

Bear in mind that when under load the voltage reading is lower than the "true" voltage which you would look up on the chart - and the higher the load, the greater it is lower.
Also if using a reading like a Sargent Control panel or similar, the reading they display can be significantly lower than the actual reading - be worth checking against a multimeter directly on the battery to compare.
 
Our leisure battery regularly falls to 12.2 by end of day, it then rises to 12.5 or 12.7 come the following morning. We have fitted one of these to the leisure battery which tends to show a slightly higher voltage than the factory fitted panel.
1643493574368.png
 
David is 100% with his comments, especialy about putting a good quality volt/amp meter directly on the battery to confirm what the battery is doing at source. I wouldnt trust these voltage plug in gadgets etc as Ive had misleading readings in the past.
Good Luck
 
Tim120 said:
Thanks David, exactly what I was looking for, most appreciated 👍
Click to expand...
To elaborate on what David is saying, if you want to get a rough idea of what is left in your battery you can measure it's voltage. BUT, it must have been sat for some time (hour?) with nothing connected to it.... Rarely practical, so getting a proper battery monitor that has a shunt is the only way to know what's left as you use the battery.
 
Thanks very much for your input, the question was really to satisfy my own curiosity as to safe levels which I can adjust the charge with either solar, should it happen, engine charge whilst driving or EHU should need be. At some point I will check with a multimeter the difference between the panel display and actual reading.
 
st3v3 said:
To elaborate on what David is saying, if you want to get a rough idea of what is left in your battery you can measure it's voltage. BUT, it must have been sat for some time (hour?) with nothing connected to it.... Rarely practical, so getting a proper battery monitor that has a shunt is the only way to know what's left as you use the battery.
Click to expand...
And to elaborate further to anyone reading this thread who may have a Lithium Battery ... A battery monitor with shunt (or hall effect sensor) to calculate the state of charge of the battery is the only way* to know what a Lithium battery has remaining. The voltage of Lithium is so steady over its use, a voltmeter will not tell you if you have 80% or 20% remaining.


* Some lithium batteries do of course come with built in State of Charge monitors, which is great and means you don't have to add anything, but they again work as they have an internal shunt inside the battery box.
 
Tim120 said:
Thanks very much for your input, the question was really to satisfy my own curiosity as to safe levels which I can adjust the charge with either solar, should it happen, engine charge whilst driving or EHU should need be. At some point I will check with a multimeter the difference between the panel display and actual reading.
Click to expand...
I find the voltage info on my sargent control panel little more than a curiosity as it reads so pessimistically. I think it is fairly consistent, so it is still usable, but have to remember not to take the displayed number at face value. I use the Victron BMV Monitor number to see the actual voltages :)
 
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