New engine Flat battery

[RevdRay]

I have recently had a S/H Golf AAZ fitted to our 1984 Wesfalia Club Joker but the battery has now become unreliable going flat if not started for a few days is this related to the engine replacement anyone else have this trouble. Always started with the old engine

[ghost123uk]

Have you measured the current draw from the battery when parked up? Summat you changed when you changed the engine could be drawing current when parked. Any more than about 150 milli Amps is too much. If there is less draw than that, it's 99% certain just a battery that is past it's best, but to be sure, measure the voltage on it when the engine is running, it should be between 13.6 and 14.2 Volts to indicate the correct charging from the alternator.

[marlinowner]

Next time the van is going to be standing for a few days, disconnect the battery. If it still goes flat then new battery required.

[davegsm82]

Any more than about 150 milli Amps is too much.

Any more than about 15 mA is excessive when nothing is turned on. My alarm draws about 8mA and that's excessive for long periods of time.

Is the alternator charging ok? Your battery voltage should be somewhere near 13.8v with the engine running (usually above idle, 1500 RPM or something).

Dave.

[ghost123uk]

Any more than about 150 milli Amps is too much.

Any more than about 15 mA is excessive when nothing is turned on. My alarm draws about 8mA and that's excessive for long periods of time.

Just had to dip back in to point out that many car radios pull between 50 and 100 mA to keep the station memory and clock running. Also, your 8mA for the alarm is well below the normal self discharge rate of an average car battery and as such can't really be considered excessive. Just my 2p worth.

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Aside = I wonder why, when other types of radio can store channel memory information and run a clock, off a tiny internal battery, why it is that many car radios require such chunks of energy to do the same (Sony's in particular)

[davegsm82]

Any more than about 150 milli Amps is too much.

Any more than about 15 mA is excessive when nothing is turned on. My alarm draws about 8mA and that's excessive for long periods of time.

Just had to dip back in to point out that many car radios pull between 50 and 100 mA to keep the station memory and clock running. Also, your 8mA for the alarm is well below the normal self discharge rate of an average car battery and as such can't really be considered excessive. Just my 2p worth.

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Aside = I wonder why, when other types of radio can store channel memory information and run a clock, off a tiny internal battery, why it is that many car radios require such chunks of energy to do the same (Sony's in particular)

Fair enough, although the largest value I've seen for memory retention on a radio was about 20mA and even at the time, this was considered excessive enough to trigger stock alarms!

8mA might not seem a lot, but one thing to remember is it's constant. Self discharge falls off like half life, not at a constant rate. Either way, a lot of our vans sit for lengthy periods of time and ANY current draw is bad news.

With regards to your aside; (P.s. I'm electronics through and through so sorry for this nerdy explanation) car radios usually contain reasonably large capacitors on the power cables for noise reduction, a large capacitor (1000+uF) could in theory contain enough energy to run a LCD clock and memory for anywhere from minutes to hours. This is bad news if you want your radio to be secure and ask for the PIN when it's reconnected, as in theory a thief could disconnect a radio and have enough time to connect it to a battery before it realises it's been disconnected. Therefore there is usually a bleed resistor which takes away that charge as soon as it is disconnected, the downside of this is that the resistor usually consumes a reasonable amount of current.

Car radios tend to use 'Volatile' memory a bit like computer RAM, i.e. they require power to maintain the data. Generally, so that should any glitch occur you can simply disconnect the power to reset everything.

Other Radios, such as normal household table radios use a Non-Volatile memory such as EEPROM, which maintains data when power is removed because batteries go dead and they are frequently disconnected and moved from place to place. usually they are so low cost that should an error occur in memory which causes the unit not to start up, then that's the end of the product, sad but true. I've had a few DAB Radios which had corrupted station/profile memory and were subsequently binned. However in almost all cases I was able to reset them by disconnecting the power and holding down a Key on the front while reapplying power. This tells the computer inside to blank the memory and start fresh (Top tip for you all)

Dave.

[ghost123uk]

Thanks Dave.
I too have been an electronics engineer, for around 40 years

[davegsm82]

Haha, well now I feel a bit foolish preaching to the converted!

Dave.

[ghost123uk]

Not at all, the info we give is for all to use