2005 Puzzling Battery Problem

[Sara]

Hi All
We have a 2005 Transit 2402CC MWB and after standing even for just 4 hours the power of the battery drops so that the engine will not start. The battery has been tested and is a fairly new one and is fine. Alternator fine. Starting motor fine. As soon as my husband gets the help of a jump start it starts immediately. Something appears to be draining the battery but what we cannot discover. Hubbie ripped out the radio and there was a phone cradle wired in which he has pulled out as well. But this morning... same problem. He just tried it again tonight after it had been there just four hours and again it won't start. It's driving him mad. Any ideas anyone please?

[the_big_fact_hunt]

you say the alternator is fine, i assume you mean it is charging properly?
apparently the diodes can fail in the alternator causing it to discharge the battery, you could disconnect your battery while standing to eliminate the battery and see if its ok 4 hours later, you can also connect a multimeter to assess the wiring to see if something is discharging the battery

[Sara]

Thankyou very much - we will try those suggestions.

[sidspop]

Does it have second battery fed by split charge?

[winterheating]

how do you know battery voltage drops does it just sound flat or are you actually testing the voltage

[ake]

Simple test to rule out the battery, next time you stop, disconnect the battery earth lead, only reconnect it when you are ready to go, if battery is discharged when you try then battery is dead, if it starts the van then the problem is on the van. Just cos the battery is fairly new, don't mean it is good

[v8rick]

it does say in the first post that the battery has been tested already.

[winterheating]

it does say in the first post that the battery has been tested already.

yeah but people have many diff ideas of testing batteries.

[sidspop]

I'll ask again, does it have a split charger?

[ake]

it does say in the first post that the battery has been tested already.

yeah but people have many diff ideas of testing batteries.

And lots of people think that if you test a battery with a multi meter and get 12v that it is good, when it clearly is not

[bazw]

And lots of people think that if you test a battery with a multi meter and get 12v that it is good, when it clearly is not

13.2V min for a battery

always amuses me that we call it a 12V system when 12 volts means a cell is almost dead lol

[winterheating]

hasv anyone got a list of voltages, and temps of a battery

[MrMPuk]

http://www.batteryuniversity.com/partone-13.htm

[winterheating]

The open circuit voltage, is measured when the engine is off and no loads are connected. It can be approximately related to the charge of the battery by:

Open Circuit Voltage (12 V) Open Circuit Voltage (6 V) Approximate charge Relative acid density
12.65 V 6.32 V 100% 1.265 g/cm3
12.45 V 6.22 V 75% 1.225 g/cm3
12.24 V 6.12 V 50% 1.190 g/cm3
12.06 V 6.03 V 25% 1.155 g/cm3
11.89 V 6.00 V 0% 1.120 g/cm3

Open circuit voltage is also affected by temperature, and the specific gravity of the electrolyte at full charge.

The following is common for a six-cell automotive lead-acid battery at room temperature:

Quiescent (open-circuit) voltage at full charge: 12.6 V
Unloading-end: 11.8 V
Charge with 13.2–14.4 V
Gassing voltage: 14.4 V
Continuous-preservation charge with max. 13.2 V
After full charge the terminal voltage will drop quickly to 13.2 V and then slowly to 12.6 V
Wait at least 12 hours after charging to measure open circuit voltage, the resting time allows surface charge to dissipate and enables a more accurate reading.
All voltages are at 20 °C, and must be adjusted -0.022V/°C for temperature changes.

[GBBiker]

Just because a battery shows those voltages on a multimeter, it doesn't necessarily mean it is a good battery.

A knackered battery cell won't normally be evident on a multimeter reading, the only real way to tell is to measure it under load.