Help please. The voltage of my new battery when not connected to my car is 13.18v. If I connect it to my car it will be drained flat within one day. Having fully recharged the battery it went back to 13.18v. I connected it to the car again and observed the following readings: Within 5 minutes it dropped to 12.85v; two hours later it dropped to 12.59v; and a further two hours later it dropped to 12.3v - so I disconnected it ... and took a reading an hour later of 12.59v (where it has stayed - whilst not connected to my car). I have taken a reading of the current being drawn off with everything turned off = 33.5mA. I have removed all fuses, one by one, with little or no change in the level of current being drawn off. My door lights and rear window demist work properly as does my after market alarm but even if I disconnect all of these the current drawn off remains 33.5mA. If I connect the battery to my car and go for a drive the reading on the car's volt meter goes down slowly. Any helpful suggestions/advice welcomed.

 

do you have an aftermarket amp? or an older head unit, somtimes these can drain the system , also the volt meter falling after the car has wamed up is a normal condition, the best way to get the actual number of rate of charge is to go to the hot post

 

Several things here don't make sense.

The battery should never be at 13.18v at rest in a stable condition... what are you measuring it with?

33.5mA is not as low as it should be but its also not enough to drain your battery overnight (or even in a week). If this value doesn't change when you disconnect the alarm & clock something is wrong with how you are measuring it...

Somethin's up!... have the DMM the battery or your method checked

Alan

 

Thanks for your replies.

Mrmerlin - no after market amp & head unit is only 2yrs old.

Alan - the 13.18v reading was taken after the battery had been connected to the car for a short time and then disconnected. I am using a DMM connected at follows: DMM +ve to chassis (via earth cable) & DMM-ve to battery -ve post, DMM red/+ve connected to 10A socket and DMM black/-ve connected to COMM & DMM dial set to 200mA. Should the connections be different? If I am using the DMM incorrectly what should I do differently? If I've connected it correctly, I agree (based on all the threads I've read) 33.5mA doesn't seem too high - but the fact is, the battery only takes a day to discharge almost completely (something I don't want to allow to happen again).

 

13.18v a short time after charging is normal as is the other voltage behaviour you noted - at rest not under load stabilised at around 12.6v.

Your meter connections to the car and battery are correct for measuring current drain. however the DMM settings could be incorrect depending upon your meter - I have four DMMs which all vary as to their connections and settings to get the 10A scale, and how they display readings in the 10A scale - Pointless describing how they vary, but one of them displays 100.0 when measuring 10A. Check the destructions for your meter.

 

MA should be below .500 Use the meter and pull each fuse one at atime untill u find the draw...........

 

Don't re-insert fuses as you pull them out one at a time. In other words, when all of your fuses have been pulled, you should get minimal Amp drain on your meter.

Do whatever it takes to get no drain when the battery is still connected...every button pressed, everything off, all fuses/relays out, etc.

Then work on adding back relays and then fuses for those relays. I'd suggest re-inserting half of them and checking the Amp drain. If that half is the problem then work backwards removing some of them. Otherwise, re-insert the other half and work from there.

 

Check your meter for another socket for the red/+ ve lead. As Jon mentions different meters are configured differently but most use a socket voltage, resistance and low current, another for higher current (as you have) and another socket for ground.

I'll take a pic.

 

I think your connection for current measurements are wrong. If you are in the 10A range you need to use the 10A socket instead of the mA (or often combined mA/V/Ohms) socket.

If in 10A mode you see a reading of < 200mA - only then switch the connection & meter range to the mA socket and 200 mA range.

Obviously for voltage use the V/Ohms or V/Ohms/mA Socket.

In all cases the other socket is black & usually labeled 'Com' so in all measurements you use the black com (-ve) and one of the red (sometimes yellow) terminals (+ve).

Of course also make sure you are on the DC range in every case.

Alan

 

Err No ... 0.5mA is 500 micro amps.

The correct goal is <20mA. Even <50mA is probably livable with care.

Also don't start in the 200 mA range unless you know for sure the current is below this level - if it is much higher you will risk blowing the meter - the fuse at least*.

Alan

*PS The fuses in meters seem to be oddball sizes designed to be very hard to find replacements for - you can never locate one one for at least a day after you blow it up...