A Meter to Know How Much Juice is Left in a Battery

Yes, there is one.

Mr. Joshi's terse reply is not that useful. A voltmeter would tell me how much is the volatge at that point, but does not divulge the amount of charge left in the battery. For all I know, in few minutes, the battery may wind up.

I wanted to know categorically that the battery is left with so many aH.

Well, you have convinced me of the validity of your assertion and vanquished any doubts.

What other choice do I have but to agree:

A voltmeter will only tell you the voltage and you will not be able to glean any information about the batteries state of charge from a voltmeter.

For all you know, in a few minutes, someone will invent a wind-up lead acid battery, and that damn voltmeter won't help you out with that either.

"Mr. Joshi's terse reply is not that useful. ..."

The replies you are receiving, IMHO, are due primarily to frustration with the constant stream of ambiguously worded and poorly researched questions posted on these CR4 forums.

Regarding your opening question, "Is there a simple meter, when connected to the terminals of a battery would tell you how many ampere-hours are left in the battery?":
In short, no, there is nothing like that available in the context provided. There are so-called "fuel gauge" ICs available from a few manufacturers (e.g., Maxim), but they are intended for integration into battery pack designs. They rely on algorithms custom-matched to a particular battery's charge/discharge characteristics.

The Wikipedia link ("State of charge") provided above by jack_of_all_trades, gives an overview of how you can achieve similar results by charting the discharge curve of an existing battery.

That simple meter would be a voltmeter. If you are familiar with the battery, the open circuit voltage or voltage at very low load will let you know about the level of charge.

.

It doesn't read out in amp-hours of course, but when you become familiar with the battery and the loads, it can provide pretty good information on how much longer you've got.

.

As long as we are on the subject, if we are discussing lead acid batteries, I feel compelled to throw in two considerations...

.

It is very easy to degrade of ruin lead acid batteries, if you are a 'fly by the seat of your pants' type of person and lack some specific battery knowledge....so here are a two quick things to note:

Overcharging a battery ruins a lot of batteries...not immediately but over time.... it causes out gassing which results in low fluid.

Low fluid is bad for lead acid batteries...but unfortunately, many people replace the water with water that doesn't meet the purity standards necessary (or contaminate the water in the process). Stop charging when or before out gassing starts.

Overdischarge another way to kill a battery (faster in this case) is to heavily discharge the battery significantly below minimum voltage levels. Typically on a lead acid auto battery, it is a good idea to end discharging an begin recharging when rested open voltage falls below 12.5 or 12.6. Some say lower is safe, but in all cases, you really never should discharge when rested open circuit voltage is below 12.0 unless you understand you are degrading the battery in a way that is probably permanent.

There are 1. Battery Capacity Tester 2. Battery Impedance Meter 3. Battery Load Bank and Capacity Tester

Since you were not pleased with the initial answers, here is a more direct answer for your specfic question:

.

'...Is there a simple meter, when connected to the terminals of a battery would tell you how many ampere-hours are left in the battery ?...'

.

Yes! The trusty old heavy-copper-bus-bar-meter can consistently and reliably meet your challenge. Just connect it across the terminals, then observe.

.

The bus bar is read while attached, with read outs based on state of matter....solid indicates you have zero aH remaining.

.

If you screwed up an let it vaporize, you did it wrong, and another one will have to be purchased, as read outs can only be accomplished while it is attached across the terminals.

Have you performed ANY searches for yourself?

Where have you looked?

What is the purpose of your request?

Why are you be rude to people who have absolutely no obligation to help you?

Here is a good place to start if you want to understand how

Link1

Also try an internet search for "battery tester" as this resulted in a few million hits.

This forum board, CR4 is an unexpected surprise for me. I find people answer when they don't want to and show their frustration on ignorant people. I would say answer correctly or don't answer. I don't think there is any compulsion for help.

I am a member of the best forum, diyaudio.com on the net, and these answers on CR4 are a big shock for me.

Now I know the importance of Moderators on diyaudio.

Gajanan Phadte

GMPHADTE, You wrote:

.

'..... I would say answer correctly or don't answer. ....

.....I am a member of the best forum, diyaudio.com on the net, and these answers on CR4 are a big shock for me.....'

.

Right off the bat, I have to ask you, ''Did you 'answer correctly' with your comment?'' Your comment isn't even correlated with the same subject of this thread...

.

...That minor technical point aside, one of the beauties of the internet is its nonhomogeneous nature.

.

Diyaudio differs in ways from CR4 that contribute to your dillusion opinion that Diy Audio is the 'best forum....on the net'; those very same differences contribute to my understanding that CR4 is far superior.

.

We should celebrate the diversity of the internet! I appreciate the individual character of CR4, inclusive of all the subtle quirks and nuances. I'm also glad there are other forums for those who need strict moderation.

You are entitled to your views. I will respect that. But tell me, as long as it is only your view, what difference does it make to me or for that matter CR4.

Mobile telephones have an icon which shows how much battery juice is left. Some recent models even show the percentage of battery power available.

Will it not be possible to have similar arrangement for bigger lead acid batteries ?

Yes. Some lead acid batteries have a built in display of an estimated remaining charge.

That is not the same as having a meter that you can attach to various batteries.