About the discharge of Lead Acid Batteries.......

[OnTheRoadAgain]

I realize we are moving away from Lead acid and towards lithium batteries but.....I still use them in my cars, motorcycles and scooters
They say never discharge them below 50%.

But some say the "never go below voltage" is 10.8v

So, if you were Discharge Testing a Lead Acid battery, what voltage would be your cut-off point ?

What cut off voltage do they use for determining Ah ratings ?

 

[snoobler]

Different references provide different voltages. Context also matters. Those are for resting voltages only, i.e., no charge or discharge for several hours (some references say 24 hours after charge/discharge). AGM and FLA are slightly different.

There's "recommended" and "never"

Not sure where you got those numbers, but they're not consistent with other references and my experience. I'm more familiar with numbers like these:



Hopefully, my response demonstrates that there is a lot of uncertainty in this area. Voltage vs. SoC is rarely accurate/useful. The best method is with a quality battery monitor that counts current, calculates Peukert effect and adjusts for temperature/efficiency. The Victron SmartShunt and BMV-7XX monitors perform exceptionally in these areas. Want to know your battery's true state of charge? Get one of those units.

Want to stop your discharge at 50%? Stop when the battery monitor says 50%. To heck with voltage.

Lastly, a heavy load on a battery causes the voltage to drop significantly. You could have a battery at 70-80% SoC, but a heavy load might pull it below 12V. Should you shut it off because it's below 12V? No.

 

[Noneyabussiness]

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Cheap and will give a constant AH reading ... both charge and discharge( no peukert effect calculations, but for the price)

 

[snoobler]

I have one of those as well used in my starter system. Purchased from Amazon for about $45 when it was on Prime.

Amazon.com

It's adequate, and way better than voltage. It's purely a current counter though. It doesn't have a 100% automatic reset based on voltage and current, but you can do it manually.

Wireless part didn't totally stink either. Range was comparable to good bluetooth.

 

[Noneyabussiness]

I did a small write-up on how to increase their range, as i needed it...

Juntek state of charge Meter mods

Juntek state of charge Meter mods

www.anotherpower.com