Hi,

Anyone able to help with battery alternator readings?

I have my car set up on a battery trickle charger or maintainer I think its called in the US, anyway, the battery is 100% charged and in good condition. After a 2 hour run with a few stop starts i noticed that its at 80% after testing when it was home.

So thinking it might be the alternator I fully charged the battery and tested to make sure it was at 100% and on the float cycle, I disconnected the charger and started it up then took a few readings

1: Battery reads 12.4 volts
2: When it's started and at idle it reads 0 volts for a short period (don't know why)
3: When its running at 3000rpm then idle then 3000rpm it reads 13.6 volts constantly without change.

Is the alternator weak? should it be higher to keep topping the battery up or is 13.6 sufficient?

On a side issue why would it read 0 volts for a 30 sec period until it was rev'd to 3000rpm?

Thanks in advance

 

"why would it read 0 volts for a 30 sec period until it was rev'd to 3000rpm?" Typical characteristic of cold solder joints at the clock connector pins. Resoldering the pins should resolve the issue.

 

Thanks for the reply

Can you help an idiot, what are clock connector pins?

 

Literally the pins on the back of the clock (i.e. the one that tells the time). It's well known issue, and could be your cause.

 

Some confusion here.

First, do you have a maintainer or a charger - they are two different things.

Second, a battery at 12.4 VDC is not 100% charged, it is 93% charged. A battery is a series of 6 wet cells, each producing 2.1-2.2 VDC and wired in series. The battery should read 12.6-13.2 VDC if 100%. Causes for the low value could be; a.) a poor quality or faulty maintainer which 'drops out' early b.) low battery electrolyte c.) damaged battery plate(s) d.) sulphate buildup on the plates. If the battery is more than 4 years old, it is nearing the end of it's useful life. To keep it in service can overwork the alternator and cause it to fail prematurely and also increase your cost/mi. due to lessened Range (MPG).

The gauge reading '0' could be several things; a.) faulty gauge b.) poor or corroded wiring and/or connections as has been suggested c.) a faulty drop-out relay (this kills all appliances and ancillaries to temporarily dedicate all the battery power to the starter, fuel pump and ignition) d.) faulty ignition switch

The battery and alternator should be tested under load. You can do this yourself with a DMM (digital multi-meter) as follows:

Disconnect negative (-) battery cable and set the DMM to VDC. Place one lead to the positive (+) terminal of the battery and the other to the negative (-) terminal. This should read 12.6-13.2 VDC. Use a DMM, do not rely on the dash gauge or maintainer indicator.

Reconnect the battery and start the car, turn on all the appliances - headlights, radio, heater, etc., maintain 1100 RPMs and take the same reading again. You want to see 13.5-14.5 VDC - this is the alternator output spec for the Bosch alternator. If the value is lower, and the battery has already been ruled out, one or more pairs of diodes in the voltage regulator is faulty - this voltage regulator or diode pac is externally mounted on the alternator and can be replaced separately.

Now, engine running 1100+ RPM, DMM set to VAC (AC Voltage), place test leads on each battery terminal. The value you want is 0 or nothing (depending on the DMM). If you have any other value, the diode pac is leaking VAC back to the battery and is faulty.

The answers to your questions will lay in one of these.

Cheers!

 

Thanks for the reply, it was 12.6v my mistake.

The charger/maintainer is one unit that combines to do either the simple charging at 2 4 6 8 16 amp or conditioning/maintaining with desulphation, soft start, bulk, absorption, recondition, float. Is that what you mean?

I will try the rest tomorrow night

 

Where does one stop and the other start ?

 

When you turn the key to the run position and the motor is not running ,
does your alt light come on ?

 

12.4 volts is dead or damn near dead. If you pull a load on it probably drops even further.

13.6 sounds about right for the alt output.

Sounds like a weak or dead battery.

 

.5 or .2 amp will maintian a charge but not charge a car battery

2 Amps will charge one of our batteries up in about two days.

 

Really, at about 1.5 Amps.

Lower, it's a maintainer, higher, it's a charger. It may be a charger w/ 'Float' capability and variable charge rate (amps), but it's still a charger.

The maintainer is designed to simply keep the battery chemistry going and replace that miniscule energy lost to temperature swings, battery inefficiencies, etc. They typically come in 0.5, 1.0, 1.2 or 1.5 amp flavors. The low amperage insures that no sulphating of the plates occurs. Even a charger at 2 amps cannot make that claim, especially for longterm inactivity.

I'm familiar with the type of charger the OP has, there's nothing wrong with it for charging. But, it's charge rate and probably it's float circuitry make it less than ideal as a maintainer, though these all-in-one units are typically marketed that way. It has the 2 amp charge rate available to charge the battery while limiting sulphate crystal formation, which it does when connected for a relatively short time (read hours, not days/weeks/months). The other charge rates are for speeding up the charging process in an emergency, you typically never want a high charge rate, which can cause sulphate crystals and boil off some of the electrolyte.

Here in the states, you can get a schumacher maintainer for under $20 at Ace Hardware which works quite well. It'll pay for itself in lower operating costs vs. the all-in-one charger described by the OP.

Cheers!

 

It kind of sorts itself out, but i can do it manually by either pressing charge or condition which then goes into a maintenance mode.

I think so, 2 mins and i will go and check

 

Yes the lights were on.

but the weirdest thing, i tested the battery and it now shows 60% and i couldn't get a reading on the multimeter. so i took the battery off the car and tested it again, it read the same with the multimeter with no reading. Then tested it on the charger test setting again and it shows 100% so i put the multimeter back on and it shows 12.6volts. I can't have a faulty tester and multimeter can I?

I am going to take it to work as people i work with are trained to test these things. Sounds weird though

 

Maintainer = if the battery is unplugged from the car , internal discharge rate of the battery .
Maintainer = if the batter is plugged in to the car , internal discharge rate of the battery + the cars battery discharge rate .

Charger = anything over the batteries internal discharge rate , if you think of charging as a net plus . If on the other hand is a discharge rate is greater than the charge going in , the battery is being charged but not enough to keep up with the discharge .
In real life you could have a car using more amps than what the alternator can put out , a 100 amp load and a 50 amp alternator .

 

Sure , why not ?
How old is the battery ?

If you have never had the clock out and redone it ,
its worth doing , your clock is old and the back side can give problems .