My car battery is oversized for the car. The battery is a bit old but usually works fine. The battery is flat (I left the lights on).
My fancy new modern charger senses a poor battery and only puts in very little charge.
I used to use a really old charger to charge this battery successfully. I opened up the old charger and saw it was only a transformer and a big rectifier. That's it. No soothing.
Is this ok for a car battery or is it way too crude?
Eddie coughed up some electrons that declared:
Well, it always has been OK - never seen a car charger that was anything but a transformer and some rectifiers - but then I haven't actually bought a new one for 20 years!
The only concern is for the electronics in the car, but generally the battery itself will do the smoothing, which only leaves over-voltage to be a problem, so don't over charge the battery, which would be bad for the battery anyway.
If you're paranoid you could disconnect the +ve and charge the battery in isolation.
Cheers
Tim
Automotive electronics is (or should be) designed to withstand all sorts of horrible things. For example, transients of a few hundred volts from the ignition coil or being jump started from a 24V battery. For details see:
Which is likely to bugger up the radio code! Do you know what yours is? I'm trying to find a roundtuit to pull the radio out to find necessary info and go to the main dealers as a result of a similar episode!
Check the electrolyte level in your battery.Filtered DC causes polarization of the battery.
Bob
An unpolarised battery isn't much use.
It's a sealed battery. Are they better or worse than electrolyte batteries when the charge drops to very low?
Similar, the difference is when they're overcharged , but any battery with a high CCA compared to it's capacity won't like being hard discharged. Boost it for a few hours on the old charger, charge it up on a decent one or by driving the car & see if it's still happy.
Dunno - might make a good door stop
Fair point.
In message , geoff writes
Depends a bit on size.
Last week a VERY large hornet decided to take a stroll across my work bench. A 2.8Ah Yuasa flattened it perfectly. Although I must admit that it was not unpolarised, the battery that is.
Any one have any other uses for old batteries?
If you disconnect the battery, make sure you have the key code for the radio !
An AC battery would be darn handy...
Adam
You've not met Radioheads big battery have you :-)
Car batteries are not fussy about the charger waveform. In fact a half-wave rectifier will do the job very well.
DJ
An ancient crude charger is actually quite good at recovering a flat and possibly sulphated battery - it will output quite a high voltage with a high impedance load, which is needed to help combat the sulphation. However, after the battery has started to take a reasonable charge rate, ditch it and use your modern one.
Electrons are electrons to the battery. If they are at high enough potential to cause a charge condition on the battery, they will.
My electrons are smaller than your electrons; take THAT!!
If it's the original radio, you just need the registration number.
I keep one just for that purpose & then connect the new fangled smart charger soon as the batt can take it. From experience though, if connecting a totally flat batt get ready to switch off the old charger before the needle goes off the scale followed by a big bang as the bridge rectifier decides its had enough!!
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