Amps And Volts When Charging The Battery

[Nishan.dj]

Hi Friends,

What is the charging Voltage and Current (V and Amp) for a vehicle which has 24V electrical system (Mitsubishi 4DR5 Jeep)? One battery is a 12V 90Amp one and the other is a 12V 70Amp one. Electrician said it has to come between 26-28V and 15Amp when the engine is running. Also Can we measure this using a digital multimeter? If so what is the best way to check? Please add a reply if you know anything. Thanks a lot in advance.

(I Found This for checking the electrical leak. Hope it would help.)

Regards,

Nishan

Edited September 26, 2011 by Nishan.dj

[Watchman]

Well, ideally when a engine is running the voltage between 2 terminals is about 13.5volts, so for 2 batteries it will be about 27, so the 26-28 figure sounds correct. But the amperage may vary a LOT depending on at what point of time you check the voltage. Ex:

1- as soon as the engine is started, since the starter motor would have drawn a fair bit of current, there'll be a higher amperage going form alternator to battery.

2- After a while the battery will be fully charged and there will be no current flowing hence a zero amperage.

3- If you're engine's idling and you got your headlights AirCon and maybe big-ass stereo running you might see only a faint current, if not none flowing.

So there's a number of factors that affect the amperage. And I dont think you can use a multimeter to check the amperage as those tiny leads wont be able to handle the current. No problem with voltage though.

As for your 90Amp/70Amp mismatch I think in this case the amperage over the entire system would be the value of the lower battery. Not too sure on this, but that seems the logical possibility.

[Shock]

As for your 90Amp/70Amp mismatch I think in this case the amperage over the entire system would be the value of the lower battery. Not too sure on this, but that seems the logical possibility.

I agree since the batteries are in series, the system amperage would be that of the lower battery.

I also want to mention that the figures 90 and 70 on the batteries is not a direct measure of the current the battery can supply. 90Amp/h is a measure of the energy capacity of the battery. I feel this is a some what miss understood rating in batteries. During cranking the starter motor will draw a few hundreds of amps depending of the vehicle. If you want to get at the capability of the battery in this regard you'll have to check its

CCA - Cold Cranking Amps and

HCA - Hot Cranking Amps

figures. And if you want to get a proper idea of the energy capacity you can use its

RCM - Reserve capacity minutes

Wikipedea has the exact definitions here ... http://en.wikipedia.org/wiki/Car_battery

Anyway these figures can vary from one 90Amp/h battery to another 90Amp/h battery as well. But this is usually not by a critical amount. That's why when you replace your battery with a one with the same Amp/Hour rating, you're usually ok.

These may be important if you want to do any mods for example to the vehicle.

Hope this helps

@ Nishan.dj

After starting if the battery terminal voltage rises to around 26V - 28V your can be pretty sure that your batteries are being charged. I also suggest to check the battery terminal voltage after turning on all the electrical accessories such as headlights, AC, signal lights stereo etc. If the voltage in the above range or at least above the battery terminal voltage when the engine is switched off you can be pretty sure that the alternator is providing the required current as well.

But this of course doesn't guarantee that your alternator is overloaded of course....

Edited September 26, 2011 by Shock

[Nishan.dj]

Thank you all for (Watchman and Shock). I got the idea.

[rameez]

i have a small question related to this.

let us assume due to my job in the night shift i drive my car continuously in the night using lights and maybe the AC/setup....this happens for about 2 months and the car is not taken out for anything else..during the day time.Can this kill the battery......can anyone explain this ?

[Watchman]

i have a small question related to this.

let us assume due to my job in the night shift i drive my car continuously in the night using lights and maybe the AC/setup....this happens for about 2 months and the car is not taken out for anything else..during the day time.Can this kill the battery......can anyone explain this ?

Even with the headlight and aircon running your battery WILL be charging (though it may not be as rapid as during the day). Its no reason for the battery to run out completely.

[Sylvi]

i have a small question related to this.

let us assume due to my job in the night shift i drive my car continuously in the night using lights and maybe the AC/setup....this happens for about 2 months and the car is not taken out for anything else..during the day time.Can this kill the battery......can anyone explain this ?

'rameez',

Do you have a problem during the night driving.

(1)After driving in the night under 30km speed about 2KM with all your equipment on on your vehicle do you notice the lights getting dim little.

(2)When you stop your vehicle after a night drive all your equipment on can you start immediately without any sluggishness of the starter motor.

(3) Have you tested the amperage when the engine is running with all your units on, this means H/Lights, A/Conditioner, W/S wiper, motor your audio setup.

I hope you have only above electrical units on your Vehicle.There is no way your alternator charging system is working correctly, for your battery to go down during the day.

Multimeter will only give a Voltage reading,multimeter cannot give high discharge and charge, they do not have that facility you have to use a Ampere meter with a reading of above 50 amps.

Ampere meter( Discharge and Charge ) connected to your system by a electrician, to read the amperage of charging, to find out how the alternator is performing, with your full discharge load is compensated at different speeds.

Some times due to faulty alternators, they will charge little Then the warning light goes off, but when your full load is on, alternator will not give required amperage to compensate the discharge of your system.

I hope this is clear to you if you wand any further clarification and assistance on your electrical system do not hesitate to contact me I will give you free advice.

Actually this test was done with the help of a test bench. Which I had I scraped as that was not necessary for the service what I do.

Sylvi Wijesinghe.