Battery drain

No, original clock, fascinating things every two minutes power winds the clock up

 

Great tick tocks after I installed and sorted the rats maze of wires

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I have fitted battery isolating terminals to both batteries and as a matter of course isolate them after every trip. No way can anything then drain current from them.

I don't like trickle chargers permanently connected in case they go wrong and fry the battery. I just give a top up charge every so often.

 

I understand your concern in trickle chargers but I've rotated two batteries for over 2 years without issue, modern digital chargers have a lot of fail-safe features built in, wouldn't use a cheap one as I wouldn't want to fry my garage if it went pete tong

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They are quite ingenious. Any change if you disconnect it?

 

Just being cautious. I once fried three fluorescent light fittings before I realised that the ctek charger was pushing about 18V on its 12V supply setting. Still under warranty so just a bit wary of the replacement.

 

I will try that tomorrow

 

You only get 18 volts if the battery is knackered and the charger is being stupid.

 

Just remember - 35mA will only run a 65AH battery flat in about 2000 hours (Which is 3 months) . Any faster then.. You might have a hidden tracker - that 35mA is typical for something with a microprocessor in it that is not trying too hard to be economical..

Your battery is probably shot. Buy a battery tester for £25 off eBay and try that : within a few seconds it will tell you the CCA of the battery...

 

Hi Mike, I've been thinking of buying a battery tester. What do they do exactly, compared to what I can read with my multi meter? Jim

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After 40 some leakage is to be expected

 

Battery was (and still is) fine. Charger was being stupid! Replaced under warranty.

 

The little electronic ones basically connect and remove a small load , a 5 watt resistor, to the battery and measure the small voltage drop on load at maybe 5 or 10 amps - from that they work out the internal resistance of the battery .. in the 0.001 ohm to 0.01 ohm region, and from that they can extrapolate the current needed to drop the battery voltage to 10 volts (I think) which is when the CCA is measured.

You cannot measure the internal resistance of a car battery with a little digital multimeter unless you have a big resistor to load the battery to the point the battery voltage starts to drop immediately from its internal resistance rather than running it flat over time.

So you get battery voltage, internal resistance and an estimated CCA.
It seems quite good - a new 500 Cold Cranking Amps battery tests maybe at 700 CCA. A very knackered 120AH sulphated AGM battery tests at 10CCA according to my tester.

For instance :
A 1 ohm resistor in series with a battery with an internal resistance of 0.01 ohms will for instance drop the terminal voltage to 1/1.01 or about 11.88 volts, or a drop of 0.12 volts.
At the same time that resistor will be dissipating 144 watts of heat...
The little electronic box switches on the test load for a fraction of a second so it doesnt melt ..

In the old days there would have been a big resistor in a box , a big knife switch , and a meter that directly measured the battery voltage, as the resistor inside starts glowing. You can still find these testers in the back of garages and sometimes on eBay.

 

Brilliant stuff. Thanks Mike.

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