Battery testers

[Nereus]

thanks for the replies.

The kind of battery tester i am looking for would tell me how much charge was left in a battery. After a few readings, i would then have a rough idea when it would have expired. Very useful for security equipment that may not be looked at for many weeks !

The tester that you have linked to does appear to take the correct approach, in as much as it supposedly applies a load to the battery under test, which is the correct method.

But it still comes up with what is usually referred to as "idiot lights". If you are wanting to check batteries as you have outlined, then a digital multimeter will show you the remaining terminal voltage, from which you can see how long it takes to discharge the cell. (by checking regularly as you have indicated).

The applications that you are referring to normally have a battery as a "back up" in case of mains failure, and if they are "stand alone" battery powered then the equipment should have a low voltage alarm to indicate when the battery is getting near the end of its life. In either case the current drain on the battery will be very low while the equipment is in its standby mode, and the type of battery that you are using becomes more of a critical decision.

[Terry]

As a rule, batteries do not last as long in the tropics – heat is a killer for batteries.
When a UPS installation is specified for use on modern metro systems (Such as BTS, or MRT) these installations are usually housed in an air conditioned environment with temperatures at a nominal 20 deg C or so – this is to keep the battery banks cool.

Cannot agree with this Terry. Any commercial UPS system, such as you are quoting, will not be using lead acid batteries, they will, or should be, Ni-Cad batteries. The air conditioning is provided to cool the electronics of the system, the batteries may benefit as a spin off, but it is not the primary reason for the cooling system. Over many years I have had to maintain UPS systems on Offshore Installations, without the benefit of air conditioning.

Nereus

We will have to agree to disagree then

You are correct in that the type of batteries should be Ni-Cad - a fact that I omitted. Also the modern ones are Gel type.

You are correct that the aircon is pimarily for the UPS electronics

BUT keep these batteries in temps over 20 deg C or so, then their battery life is shortened on average by 1month / deg C .

I have also been involved in many mass transit E&M designs over many years and it is the considered view in the industry that cool and dust free environments should be provided for BOTH batteries and the UPS systems.

I have seen projects whereby this had not been done and the cost of battery replacement and housing mods have been horrendous.

Anyway - this supposed to be about testers


T

[Khundon1975]

Before returning to the UK, I bought a 4 pack of EverReady AAA batteries, as EverReady was owned by the conglomerate I worked for.

I bought 2 back with me and put them into two identical clocks.

One lasted just over a year and the other is still running strong after 5 years. Go figure.

Do these batteries deteriorate, if kept on the shelf for a long time?

I was told but don't know if it was correct, that diesel engines require a stronger battery than petrol engines and also 75% of the charge goes in lighting up the dash etc, before even starting the engine.

Maybe Nereus or Terry can enlighten me on the last couple of points.

[Nereus]

I was told but don't know if it was correct, that diesel engines require a stronger battery than petrol engines and also 75% of the charge goes in lighting up the dash etc, before even starting the engine. Maybe Nereus or Terry can enlighten me on the last couple of points.

Yes, a diesel engine will require a "stronger" battery than a petrol engine. A diesel has a much higher compression ratio than a petrol engine, so it takes more "effort" if you like, to crank it over, meaning the battery will have to have a larger capacity--- usually referred to as CCA, cold cranking amps.

Not sure what you are asking with the second question. A starter motor can draw 400 / 500 amps from the battery whilst it is cranking, albeit for only a short time. 2x 100watt headlights will draw around 16 amps, so providing the battery is fully charged, the extra draw is not going to make much difference. If you are asking about the load when the engine is running, then the alternator will provide all of the cars requirements, including recharging the battery.

[Terry]

Nereus

Looks like we have to agree to agree on that one


As a discussion point - Do any of you subscribe to my 'prolong the life of car batteries' theory?

i.e. Use max car aux equipment wherever possible and let the alternator do the work - thus minimising charge rate of the battery.

It seems to work for me

[Nereus]

Nereus

Looks like we have to agree to agree on that one
Thats good then

As a discussion point - Do any of you subscribe to my 'prolong the life of car batteries' theory? No, not really.

i.e. Use max car aux equipment wherever possible and let the alternator do the work - thus minimising charge rate of the battery.

It seems to work for me

You have no control over what the charge rate is into the battery. The voltage regulator will maintain the system voltage to whatever the designer decided was required. (in a car 12 volt system, around 14.4 volts)
The battery will continue to take a charge, tapering off, until it`s terminal voltage rises and is equal to the system voltage, at which point the two voltages are opposing each other and no further current will flow into the battery.

Without being pedantic, the "zena" (zener) is only a small part of the voltage regulator. It is used as the "reference voltage" in a voltage divider network that switches transistors to vary the excitation of the alternator field, which in turn, controls the output of the alternator.

The voltage is the key: an increase in load on the system for what ever reason, will cause the voltage to drop slightly, which the regulator senses and increases the excitation to bring the output voltage back up to the required level. The reverse being the case with a decrease in system load. You could in fact, remove the battery once the engine (alternator) is running, without any effect on the system.

But, whatever works for you is good!

[Khundon1975]

Nereus

"A starter motor can draw 400 / 500 amps from the battery whilst it is cranking, albeit for only a short time".

How does a 12v battery produce such high Amps? That is a hell of a lot from a little black box.

Terry
Let my little wife drive your car, she switches on EVERYTHING whether it's needed or not.

She will keep your battery in tip top condition.

I believe the new top end BMW's don't use the alternator to charge the battery now, they use retrieved energy from the braking system to do it instead.


Sorry, back to testers.