Pulsing battery charge

Grumpy_chap

My car has been on SORN for lockdown and I now need to get it an MOT.

Just gone to put the battery on charge and it is pulsing wildly min-max which I have never seen before.  Am I OK to leave that charging?

The battery is shot anyway - it needed a new battery before lockdown - all I want to do is get the battery enough to start the car (even if I have to also assist with a "jump") and then take it for MOT.  If the MOT is a pass, I have a car for another year and I'll buy a battery and do proper service.

If the pulsing damages the battery, it is no loss.  What I don't want to do, though, is damage the charger.

AdrianC

What sort of charger is it?

It's possible that if a smart charger is seeing the battery as being very flat, it might be pulsing to try and get enough charge in to "wake it up" before starting a more normal charge cycle.

Grumpy_chap

AdrianC said:

What sort of charger is it?

Woolworth 4 amp battery charger for all 12 volt car batteries fitted with automatic safety cut-out complies with Home Office Regulations Made in Great Britain.
Someone took some pictures of one just like it:
https://www.ebay.co.uk/itm/vintage-battery-charger-4-amp-12v-woolworths-winfield-used-working-/274844912823?ViewItem=&item=274844912823&nma=true&si=Qy93083Gk%2F9HlFT9JPGZ0tuxayg%3D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

I did do a charge last week, which got something into the battery. 
Then the next day, opening the bonnet set the alarm off.  Once the alarm ceased, I started to charge, but the dial was swinging wildly so I stopped.  I thought, even if the battery had gone too dead to allow the horn to still sound, the relay might have been pulsing down.
This week, at slow charge, it is fine, but fast charge is pulsing.  I am sure if it was the alarm relay, that would be deceased by now.

AdrianC

OK, so definitely not a smart charger, then...



I suspect "1366" was probably roughly when it was made...

It's likely that it's pulsing because it's chucking so much current in that the much vaunted "automatic safety cutout" is being tripped. Give it a day or so on slow charge, then try fast.

facade

It might be a good idea to disconnect the earth lead from the battery while you charge it.

There may be something switched on- like your alarm, which is trying to take more current than the charger can deliver, hence the pulsing as it tries to protect itself, BUT the battery will never charge if this is the case.

Grumpy_chap

AdrianC said:

It's likely that it's pulsing because it's chucking so much current in that the much vaunted "automatic safety cutout" is being tripped. Give it a day or so on slow charge, then try fast.

I'll do that and see what happens.

Just don't want to damage anything.

This charger is one of a handful of items I inherited from my father.

The others were a state of the art audible entertainment centre:


Plus a superb nest of tables:
https://www.pamono.co.uk/czech-nesting-tables-by-poul-hundevad-1960s-set-of-5/?utm_medium=cpc_test&utm_source=google&utm_campaign=PLA_UK_6497616183_73238117970&utm_content=381960973867_c_&utm_term=pla-298893601623___OXJ-605117&gclid=EAIaIQobChMIr5qv7bGI8wIV0e7tCh2c5g7jEAQYAiABEgJ5V_D_BwE

Finally, my daily use scientific calculator:
https://www.ebay.co.uk/itm/363539648393?hash=item54a4a6cf89:g:jcUAAOSwwL1hPHvk

The radio is, perhaps, the best (though least used) of the items because of the story that goes with it. 
I remember Dad saving up for the radio and he kept looking at it in the shop over several months then he was able to get the radio and I was, "Like, wow, that is sooooo cool, you are sooooo lucky Dad, I wish I could ever get something like that." 
Dad's response was "over my dead body will you be able to have something like this." 
He was, of course, entirely correct as said radio became mine only as we cleared out the garage following his passing. 
I laugh about it, but also think a better response might well have been more motivational along the lines of "Well, son, if you study hard and do well at school, you'll be able to get a good job and one day you will be able to buy yourself a state of the art system just like this."

Grumpy_chap

facade said:

It might be a good idea to disconnect the earth lead from the battery while you charge it.

There may be something switched on- like your alarm, which is trying to take more current than the charger can deliver, hence the pulsing as it tries to protect itself, BUT the battery will never charge if this is the case.

That'll be easy to do - I will right now.

Grumpy_chap

facade said:

It might be a good idea to disconnect the earth lead from the battery while you charge it.

There may be something switched on- like your alarm, which is trying to take more current than the charger can deliver, hence the pulsing as it tries to protect itself, BUT the battery will never charge if this is the case.

Brilliant suggestion - done and charging happily now at fast charge rate

Ectophile

If it's a cheap old charger, rather than a fancy modern electronic one, then the chances are that it's overloaded and triggering an emergency cut-out.  That could be a thermal switch.

I would be inclined to leave it on trickle charge for several hours (maybe overnight), to see if that puts enough charge into the battery that you can then switch to rapid charge.

facade

Grumpy_chap said:

facade said:

It might be a good idea to disconnect the earth lead from the battery while you charge it.

There may be something switched on- like your alarm, which is trying to take more current than the charger can deliver, hence the pulsing as it tries to protect itself, BUT the battery will never charge if this is the case.

Brilliant suggestion - done and charging happily now at fast charge rate

When you reconnect the battery, whatever is on is going to start working- this might be the alarm going off!

When the battery on my woeful Renault Nissan inexplicably went flat I had to disconnect it to charge it, because the (pointlessly complicated and unnecessary) BECM had gone into some half reset mode where it was trying to put the lights on (they were feebly glowing with the charger connected- yes the switch that requests the BECM to turn on the lights was off), maxing out the charger.

cattom

Might be to late to tell you, but don't charge the battery with earth or live cables still attached. if you do, it can damage the ecu, if the car has one. also it may make your dashboard warning lights come on and stay on.