How to read an analogue battery gauge ?

[Oscarpop]

I really should know this, but as it is a little foggy here goes:

I have an analogue battery gauge. the needle swings from about 9v at one enbd to 14 v at the other with the 12v being at the 12 o'clock position.

When charging it reads about 12.5-13.5 v

and when the batteries are fully charged it reads about 12.5V.

However i am not sure at what voltage the batteries are effectively discharged, and thus what say " 11.5v" would mean in terms of % charge remaining.

I know I can buy a digital battery monitor, and possibly will at some point.

But thanks for the answers in advance.

 

[VicS]

I really should know this, but as it is a little foggy here goes:

I have an analogue battery gauge. the needle swings from about 9v at one enbd to 14 v at the other with the 12v being at the 12 o'clock position.

When charging it reads about 12.5-13.5 v

and when the batteries are fully charged it reads about 12.5V.

However i am not sure at what voltage the batteries are effectively discharged, and thus what say " 11.5v" would mean in terms of % charge remaining.

I know I can buy a digital battery monitor, and possibly will at some point.

But thanks for the answers in advance.

I' d expect a higher reading when charging.. more than 13.8, possibly up to 14.4

Fully charged and rested with no load for 12 hours or so I'd expect 12.7 ish or a little more

hallf charged would be around 12.3 ish with no load

Effectively discharged if below 12 , with no load

Id suggest you check you voltmeter against a reasonably decent multimeter.

 

[alahol2]

I've got a table similar to this on board.

 

[Oscarpop]

Briliant!!!!
Thanks for that

 

[pappaecho]

Looks to me that it is underreading. As VicS says I would check with a good multimeter, so you know where you stand

 

[KAL]

I've got a table similar to this on board.

That's a really useful chart - thanks!

Fire up the laminator, Jenkins!

 

[VicS]

That's a really useful chart - thanks!

Fire up the laminator, Jenkins!

Here's an even prettier one

 

[nigelmercier]

Here's an even prettier one...

That looks handy, but isn't the minimum level a bit low?

 

[Richard10002]

That looks handy, but isn't the minimum level a bit low?

+1

I think it was posted for the prettiness, rather than information.

 

[halcyon]

That looks handy, but isn't the minimum level a bit low?

The straight line is the voltage of a settled battery, the green is when on charge, red with a small amperage drain.

A battery has three voltage ranges, off load settled, on charge, and on load, this voltage is also temperature dependent, and battery age dependent.

The settled voltage shown is at 60 F, 20 F will change voltage by 0,05 V plus for a lower temp, negative for a higher temp. This voltage will also increase with a new battery as it's used, each time it's charged the voltage will increase, it can be up to 13.1 V, then overtime this will fall to 12.7 / 12.8 volt fully charged. In time this voltage can fall as the battery ages.

A fully charged battery reaches 15.5 volt, but the top end is not used, actual value depends on charge source.

The on load voltage varies with current drawn, and again many other detail. But reasonably straight line down to 50% capacity then falls off as the graph shows. Assuming a average power drain equal to 5% of battery amphour rating, discharged over 20 hours constant use, 12 volt is a reasonable 50% capacity mark.

But it's not precise at any point, hence the problems trying to monitor battery condition.

Brian

 

[nigelmercier]

The straight line is the voltage of a settled battery...

I meant the "safe" level was too low at 25% discharge.