Battery voltage vs state of charge

[dxhall]

Interesting table from ADVRider.  I didn’t know state of charge and resting voltage showed such a linear relationship.

[Muzz]

Suspect that is for a new battery.

Food for thought, at least on the calcium technology wet cell batteries, once the voltage drops to 12 volts a lot of smart chargers will not recognise it as a battery and just sit there saying it is fully charged.  I have an old "dumb" charger (an old transformer type) and they don't care what the hell the voltage is.  Put the battery on that for 1/2-1 hour, bring the voltage up and then the smart charger will do it's thing.

[mechanicsavant]

Good on ya Muzz . That’s why I treasure my vintage Craftsman batt. Charger .
Also , cranking voltage is very important , I get concerned when it goes down to 10v or so .

[kingoffleece]

https://tecmate.com/products/ts-126/

This little guy here stops a whole lot of issues before they become real problems

[Wayne Orwig]

Interesting table from ADVRider.  I didn’t know state of charge and resting voltage showed such a linear relationship.

That chart is often shown on RV sites. But often people do not understand that it is meaningless for a battery with even the slightest load. The battery must be fully rested for hours for that chart to apply.

I have one of these gadgets on each motorcycle, and my camper battery. Very handy to chart charge voltages and battery resting voltage.

https://www.amazon.com/Kanruis-Bluetooth-Wireless-Cranking-Compatible/dp/B08YR4NQX3/ref=sr_1_4?keywords=battery+monitor+bm2&qid=1638886865&sr=8-4

[Mike Tashjian]

NOCA genius 10 amp charger is on my wish list as it does charge from a really low voltage and I believe will desulfate  as well. At 100 bucks it is not cheap but looks to be a charger that can do almost everything.

[Muzz]

NOCA genius 10 amp charger is on my wish list as it does charge from a really low voltage and I believe will desulfate  as well. At 100 bucks it is not cheap but looks to be a charger that can do almost everything.

Had to look that up Mike.  Charges as low as 1 volt.  That alone differentiates it from most other smart chargers.

[kingoffleece]

Does that not make the assumption that a battery discharged that severely is indeed recoverable?

Some info: https://www.recovermybatteries.com/batterybasics1.html

[chuck peterson]

If you measure the individual wet cells of a full charge it can be as high as 2.2 volts each X 6 cells = 13.2 volts. Notice the chart says 12.6 +..

What I’ve heard about that chart is how 60% of your battery lives between 12.6 and 11.9 volts

About every 1/10th volt is worth 10% of your battery

So finding/gaining an 0.3 volts thru your charging system by cleaning all the grounds and a second ground off the recitifryer was worth the trouble

And using the adjustable regulators,  on a Convert, you can overcome the draw from the headlight. Just don’t run too long without the headlight

On another bike, the charging system never tops off the battery (12.4 volts) and its best to plug it in after a ride. Charger brings it back up to 12.7/8 resting, and suddenly the starter is working correctly. 0.3 volts difference seems like very little but it’s 30% of the battery

[guzziart]

The chart seems useless to me.  Using voltage is an indicator as a percentage of state of charge is deceiving, you still wouldn't know what the battery capacity is.  If I were to disassemble my perfectly good 12.6v battery, cut the 6 plates in half and reassemble with the half  plates, my battery would still be at 12.6v.  However, the capacity would now be half and would not have the ability to do what I need it to do.  Basically, performance that mimics a partially sulphated battery.

A few of you have mentioned aftermarket state of charge indicators, etc. that you've mounted on your vehicles.  While looking at those devices described, I came across some devices that perform non-destructive battery load testing (unlike Milton style units), indicate battery health, charging & cranking system checks, etc. starting at around $32 (e.g. Konnwei KW210, etc.).  I think I might buy one of these devices versus using my voltmeter to troubleshoot problems as I have done for decades.  It seems to me that these low cost devices yield way more useful information than checking your battery voltage and then comparing that value to a chart on the wall....imho.

[Kiwi_Roy]

Look around your house, I guarantee you have several old Wall Worts stuffed in a drawer that will put out 12 Volts at half an amp or more, these things will revive a battery from dead flat to a point where your fancy battery tender knows what its dealing with.

[guzziart]

Look around your house, I guarantee you have several old Wall Worts stuffed in a drawer that will put out 12 Volts at half an amp or more, these things will revive a battery from dead flat to a point where your fancy battery tender knows what its dealing with.

If not, one could possibly jump the dead battery momentarily with a good battery to get your smart charger on-line ??!!  But depending how long it has been flat dead your efforts could be too late. And, if the dead battery has been subjected to freezing temps, don't waste your time, it's dead for good.