Ratcliffe coal

Sometimes batteries develop internal shorts. And Just Die.

I changed my car battery this year., It still started the car but I was getting strange error codes indicating low voltage. Tests indicated it was about 50% of rated performance. Batteries will continue to work until a point at which they simply dont have enough any more and then they will go downhill fast.

I’ve never disconnected a battery to charge it in situ. Maybe I should have but nothing bad has ever happened.

Tim

Connect charger + to battery +, charger - to an earth point other than the battery’s, switch on charger.

This could be the EV vehicles that don't have a cooling loop for the battery.

Most modern cars pamper the battery. Before charging begins, the heat pump either raises the battery temp (on a cold day) or lowers the battery temp (on a hot day).

No matter what car you buy, you have to check for customer reviews regarding charger behavior, to catch any obnoxious behaviors before you buy. If the car computer arbitrarily "denies fast charging, based on charging history", that counts as a negative mark against the car brand. The reason the car computer keeps track of this, is the car computer tries to "stretch" the battery life, so it surpasses the company warranty period. After the warranty is toast, the car will no longer care about battery wear conservation.

And batteries don't have to die. They can have reduced storage capacity (like your laptop) as they get older. This is why, if a car is recycled, the recyclers are interested in the battery cells, as they can still be charged, and used for other projects.

It's a complex topic.

On the assumption that there's good logic to that sequence, and understanding the logic makes it more likely the instruction will be followed, can you explain why the +ve terminal should be connected first, and why use a chassis connection for the -ve rather than the battery -ve terminal.

To reduce the possibility that a spark on making the final connection might ignite hydrogen emitted from the battery?

(Though I've often wondered whether a flat battery would be doing much electrolysing?)

nib

You connect the +ve first simply because then if you accidentally touch something with the positive battery clip there wont be a spark. Assuming you are jumping a live battery. If its a charger it doesnt matter

If you then touch the negative to anything you are unlikely to get a spark.

The choice as to whether to connect to the battery negative or chassis depends on how the starter motor is earthed. If jumping.

If charging its irrelevant

Well yes, quite possibly if its out of balance with dead cells and fully charged ones

Thanks. That's what I thought, but wondered if for some reason I was wrong.

However its another example of the 'all snakes are poisonous' rule.

In 'Fate is the Hunter' Ernest K Gann relates how he was taught to fly

Rules are for the guidance of wise men and the obedience of fools.

then use esso synergy premium !!. It has NO ethanol (in much of the country).

I would recommend Googling the problem, because there have been other brands, where those sorts of "mysteries" occur.

The conclusion here, is the audio system is drawing 1 ampere.

Thanks Paul. I did try to measure the parasitic drain on the battery, which didn't seem to be significant, but I may not have done it correctly. I'll try it again.

I recall talk about firmware bugs in entertainment equipment that caused random intermittent current drains.

OK, a quick google on car entertainment firmware battery drain shows the problem as being fairly widespread.

Did it properly this time. An initial surge of 1.6A, which dropped suddenly to 0.65A after about a minute, and stayed there for a little while, but then dropped again to 0.06A. I was a little alarmed at the initial surge, thinking it was the continuous parasitic drain, but with the eventual drop down to 0.06A, and after a bit more Googling I realised it was just various electronics settling down after they'd be reconnected.

I can only conclude that I had inadvertently and unknowingly left something drawing power when I'd previously switched the off ignition. But whatever it was, it wasn't obvious - no lights nor radio etc.