How fully charged is your battery - interesting info

[IG.]

I stumbled upon an interesting table which allows you to judge the charging state of your battery based on the exact voltage of the battery NOT under load.

Car battery - Wikipedia, the free encyclopedia

(scroll down to see the table)

Terminal voltage
The open circuit voltage, is measured when the engine is off and no loads are connected. It can be approximately related to the charge of the battery by:

Open Circuit Voltage (12 V) / Open Circuit Voltage (6 V) / Approximate charge / Relative acid density
12.65 V / 6.3 V / 100% / 1.265 g/cm3
12.45 V / 6.2 V / 75% / 1.225 g/cm3
12.24 V / 6.1 V / 50% / 1.190 g/cm3
12.06 V / 6.0 V / 25% / 1.155 g/cm3
11.89 V / 6.0 V / 0% / 1.120 g/cm3


That's why I permanently installed a V-meter on my bike, so I know when I need to charge the battery.

 

[outlawbusa]

That's an awfully small % between 6.0 and 6.3 volts = empty and full

At least on the 12v system it spreads the gap a little more~!~

 

[mike1180]

This too:

 

[Mr Bogus]

Works for "new" batteries..

problem is that this does not account for "sulfated" battery issues.. you can have a battery with correct voltage and virtually no amperage available... Voltmeter reading is great for charging system operation but not very good for actual battery condition..

AFWIW.. if your battery shows more than around 14.0V during charging? probably getting ready to go south.. 13.5 is a normal reading

Also, watch the voltmeter while cranking the motor.. again you could have 12.5 static and as soon as you hit the starter? could dive to 0.. (you want 11.5 or so cranking)

Also, a battery can be fully charged and show abnormally low voltage.. (shorted cells) and could explode if you continue to try and get it to the 12.5 with a charger (I have witnessed 2 battery explosions and it is not pretty)

 

[dadofthree]

You left out an important part of open circuit voltage checks. It's a good tool, but load testing is the only true test IMHO.

Open circuit testing should be performed with the battery fully charged and completely disconnected from all loads.

Wait at least 12 hours after charging to measure open circuit voltage, the resting time allows surface charge to dissipate and enables a more accurate reading.

 

[Mr Bogus]

You left out an important part of open circuit voltage checks. It's a good tool, but load testing is the only true test IMHO.

Open circuit testing should be performed with the battery fully charged and completely disconnected from all loads.

Wait at least 12 hours after charging to measure open circuit voltage, the resting time allows surface charge to dissipate and enables a more accurate reading.

actually for a bike battery? I did ... hit the starter... plenty of load for a bike battery...

surface charge on a battery will make it appear fine when it is actually toast, no need to age it for 12 hours either.... hit the starter Mavis, hit the starter!

 

[dadofthree]

actually for a bike battery? I did ... hit the starter... plenty of load for a bike battery...

surface charge on a battery will make it appear fine when it is actually toast, no need to age it for 12 hours either.... hit the starter Mavis, hit the starter!

Bogus head. The 12 hours is for the open battery test. Where are those glasses you bought.

And yes, as long as my bike cranks I'm good too, but the thread was about something else

 

[Mr Bogus]

I did go look at the wiki on batteries... pretty incomplete actually.. a few good points missing and others there..

storage: NEVER on a cement floor.. batteries discharge across the bottom when subjected to the cement (could be moisture plays a part in this, but wood or open grate is preferred.. Also "dirty" batteries do the same thing across the top.. Put a volt meter on the plastic only.. will give you readings..

If you tap the starter, it will take the surface charge off the battery... it will in fact drop and then come back up.. so no need to age for 12 hours... (would have bankrupted me if I had to do that )

 

[aussiekeeper]

storage: NEVER on a cement floor.. batteries discharge across the bottom when subjected to the cement (could be moisture plays a part in this, but wood or open grate is preferred.. Also "dirty" batteries do the same thing across the top.. Put a volt meter on the plastic only.. will give you readings..

NOT true.....
Modern batteries do not have exposed bridge clamps. They are sealed. You may place a modern battery on a cement floor.........

 

[dragonbusa]

battery tenders on both my bikes,no need to test them. there always ready to ride

 

[Mr Bogus]

storage: NEVER on a cement floor.. batteries discharge across the bottom when subjected to the cement (could be moisture plays a part in this, but wood or open grate is preferred.. Also "dirty" batteries do the same thing across the top.. Put a volt meter on the plastic only.. will give you readings..

NOT true.....
Modern batteries do not have exposed bridge clamps. They are sealed. You may place a modern battery on a cement floor.........

I stand corrected sorry... (some old school stuff that has gone away..)

 

[IG.]

That's an awfully small % between 6.0 and 6.3 volts = empty and full

At least on the 12v system it spreads the gap a little more~!~

That's the nature of the beast. That's why using a digital V-meter is the best. I took an analog Radio Shack V-meter (draws 0.8 mA) and permanently connected to the battery. Then, I carefully calibrated it with my digital V-meter. Additionally, I drew a green line between 12V and 13V mark, so I have an excellent visual indication what my battery voltage does at different times: bike was sitting for a while, just came froma ride, gauges ON but the bike is not running, the bike is running, cranking, etc.

 

[IG.]

This too:

Clymer must've been drunk when he put out those numbers in item a), or he was not specific at which point in time the measurements should be taken.

A fully charged battery is 12.6V (OK, maybe 12.65V), but not higher.

If one connects a V-meter to the battery and observes the voltage it will be something like this. During the charge: 13.5V - 15.5V. After the charger is disconnected, the voltage doesn't drop to 12.6V right away. Instead, it drifts down, initially rather quickly, but going down from about 13.0V - slower and slower. So, 5 min after the charger is disconnected, the battery may show 12.9V, 20 min later, 12.75V, an hour later 12.65V. So, the key is to let the battery sit for a while to exclude the residue voltage leftover right after it was charged.

The real normal voltage I consistently observe on my bike is this (assuming the battery is fully charged).

Everything is OFF: 12.6V.

The key is ON (headlight OFF - yeah, I have a switch which I installed): 12.0V, with the headling ON: something like 11.8V.

Cranking: around 8.5V - 9.0V.

Idling: 14.5V.

Riding: 13.5V.

Keep in mind that the battery itself loses about 1% - 2% of charge all by itself just sitting there (the nature of the beast). So, in one week of sitting, that's approx. 1.5% x 7 = about 10%. Doesn't seem like much. However, a short ride on a weekend won't replenish all of it - so after a week let's say it lost 10%, but after some riding got back 5%. So, if the bike is ridden like that, it loses 5% each week. So, a few months go by and all of a sudden, the bike wouldn't start, and most would think the battery went bad. Nope. It gradually lost it's charge over time, and needed to be additionally charged by other means.

Oh, and don't forget those bike alarms. I had an issue with Scorpio years ago after I installed it. It was drawing around 10ma when the alarm was off and about 15 ma when ON. Well, 15 mA x 24 hours = 360 ma h = 0.36 Ah. So, after a week, that's 0.36 Ah x 7 = 2.5 Ah. That's not a small amount! That's 2.5 Ah on top of 10% of what the battery loses all by itself (which for a 10 Ah battery would be 1 Ah). So, I contacted them and they confirmed that 15 mA was too much, and sent me a replacement unit. That one drew about 5 ma when not armed and about 8 mA when armed - roughly twice less draw. This still adds 1.25 Ah per week - something to be considered.

An interesting example would be when the battery has barely enough juice to start the bike ONCE. Then the rider goes to the gas station. Shuts the bike off, puts the gas in, and the bike would not restart. Dang! Just started 5 min ago. Well, the thing is it had enough juice to start the bike - and this took away some juice so that the battery charge crossed the threshold and now doesn't have enough juice to start the bike. The 5 min ride to the gas station (even if rpm is high enough to be charging the batter) is not enough to replenish that.

 

[Tufbusa]

If I suspect a battery is getting weak, I drag out the load tester.

This is the only way I have learned how to really determine the condition of the battery?

 

[IG.]

Works for "new" batteries..

problem is that this does not account for "sulfated" battery issues.. you can have a battery with correct voltage and virtually no amperage available... Voltmeter reading is great for charging system operation but not very good for actual battery condition..

AFWIW.. if your battery shows more than around 14.0V during charging? probably getting ready to go south.. 13.5 is a normal reading

Also, watch the voltmeter while cranking the motor.. again you could have 12.5 static and as soon as you hit the starter? could dive to 0.. (you want 11.5 or so cranking)

Also, a battery can be fully charged and show abnormally low voltage.. (shorted cells) and could explode if you continue to try and get it to the 12.5 with a charger (I have witnessed 2 battery explosions and it is not pretty)

Yes, I agree that a V-meter is not a complete test as you described. But my point is that it is so much better than nothing, and this allows the rider to keep an eye on it in an easy way, and notice a sign of something not right way ahead of time, and not be stuck in the middle of the road, or destroy a starter case with a weak battery as happened to so many.

I would not attempt to start the bike if the voltage is 12.3V or below. I have the simplest AC adaptor style charger. When the need arises, I would charge the battery for a few hours or overnight.

Strongly recommend from real American company RadioShack, proudly made in China. LOL

RadioShack® Panel Meter 0-15VDC - RadioShack.com

When I was calibrating it with the digital V-meter (also from RadioShack which I bought about 15 years ago), I connected a potentiometer which could be adjusted with a small scredriver instead of the fixed resistor it comes with. Then, I adjusted the position of the needle with the adjusting screw on top of the V-meter (visible in the middle of the black portion of V-meter) so that it is most accurate in 12V-13V range. I.e. it may be least accurate showing 1V (but who cares), but would be spot on in 12V-13V range.

 

[jsjdjn]

Battery Tender Baby!!! All is good.

 

[IG.]

If I suspect a battery is getting weak, I drag out the load tester.

This is the only way I have learned how to really determine the condition of the battery?

Well, it's hard to guess the battery is weak until it might be too late. Acatully, these days batteries are pretty good. So, 99% of the time it's simply whether the battery is charged or not.

Instead of throwing out my old bike battery, I installed it in the shed, and connected to it a small solar panel on one end (you know they sell those to maintain the battery in the car when it sits for long times), and a 12V light on another end. So, when I need a light for a few min in the shed, especially when it's dark, I don't have to struggle with a flashlight.

Well, one day I forgot to turn the light off, and the battery completely discharged. That was winter time and I thought the battery was done. At least this would've been the case with older batteries. When completely discharged, the battery is full of water (as opposed to acid when fully charged), so the water freezes and destroys the battery. But, I gave it a shot - took it indoors, and to my surprise after being charged for about 24 hours with my simple AC adaptor style charger (charging current is about 0.3 Amp) the battery seemingly fully recovered. Well, I don't use it to start the bike, but the light in the shed lights up without any issues. I guess the gel they use now can withstand freezing.

 

[mike1180]

for Battery Tender.
I use one whenever I am not riding.
My battery reads 13.0 consistently with a digital meter, after the tender is removed.

 

[IG.]

Can't beat the simplicity - "Set it and forget it". Bulletproof.

 

[valkyriemc]

If I suspect a battery is getting weak, I drag out the load tester.

This is the only way I have learned how to really determine the condition of the battery?

+1-Yup.