Is my battery kaput?

[swee'pea99]

The only true way to say if a battery is ok, is to do a load test, putting the battery under heavy load. It should be able to put out nearly the cold cranking amps(CCA-written on battery)) for a short period.

However a battery that stays above 12.6V for a long period would be a good indication of being good. The battery will fall away from above 13V because that is peak voltage charge. Nominal is 12.6V. If its still above 12.6V for a few days and it spins the engine over quickly when you re install it-good battery.

Sluggish turnover indicates worn battery.

Be very careful when measuring inline current with a simple meter that requires correct lead position for low amperage readings. Cars can draw several amps for a short period whilst going into sleep mode. If you have you meter set on the wrong scale it could either blow a fuse(in the meter) or fry the meter.
Never test in line current when the car is running or about to be started, many, many tens to hundreds of Amps can be drawn and will literally set your little meter on fire.

The only way to measure high Amps safely is to use an Amp clamp.

Thanks, that's really helpful. Not least this

However a battery that stays above 12.6V for a long period would be a good indication of being good. The battery will fall away from above 13V because that is peak voltage charge. Nominal is 12.6V. If its still above 12.6V for a few days and it spins the engine over quickly when you re install it-good battery.

If it's dropping, as it appears to be, by about 0.1 a day, it should be 12.6+ for a week, give or take. I was about to add that I know from experience it'll set the engine spinning at first use, but of course I always top it up fully before re-installing it, so that doesn't really tell me anything. But with the volts holding above 13 after a couple of days, I'm thinking the battery probably is sound.

I take on board the perils of measuring inline current. Which hole & setting would you recommend? As I think I said earlier, I just started off with one far too high then worked my way down till I found one that gave a reading, then stopped. (As best I remember, I wasn't getting even a flicker using the other 'ole...but I could be mistaken. I confuse myself, and forget things a lot.

 

[swee'pea99]

Red lead in the left hole for the 10A range, middle hole for everything else. If you value your meter you'll start with the 10A range first until you know the current is below 200mA. If for any reason you see it's several amps, pay heed to the 10s time limit.

Right! So, left hole, 200mA - 10A; right hole, 0 - 200mA, yes? So

Carefully use the ampere mode in the multimeter by selecting correct probe cables and selector knob. Disconnect the car's negative terminal. Now bridge the multimeter wires between the negative battery node and the disconnected terminal. Note down the ampere passing thru multimeter. If it is approximately 0.05Amp then there is no parasitic draw. Otherwise, if it is above this value there is certainly an error in some circuit.

Again, apologies for ignorance, but I get baffled by decimals...central hole, and switch where it is? (On 20m) And looking for a reading of the order of 0.05?

 

[numbnuts]

Just take said car to a garage and get it sorted and while there ask them to wire up the solar/regulator panal - why
as you don't really know what your doing, now be honest you don't, we can't all be good at everything.

 

[presta]

Again, apologies for ignorance, but I get baffled by decimals...central hole, and switch where it is? (On 20m) And looking for a reading of the order of 0.05?

No, 0.05A is 50mA.

 

[Cycleops]

..... preferably an auto electrician who is used to dealing with such issues. I don't think I can take any more daily updates on swee'pee's battery voltage.

 

[swee'pea99]

..... preferably an auto electrician who is used to dealing with such issues. I don't think I can take any more daily updates on swee'pee's battery voltage.

There there, you 'ave a sit down...nice cuppa tea.

Just take said car to a garage and get it sorted and while there ask them to wire up the solar/regulator panal - why
as you don't really know what your doing, now be honest you don't, we can't all be good at everything.

I don't. That's why I'm trying to learn. I can do all sorts of things where it used to be that I didn't know what I was doing...you'd be amazed! Anyway, soon as I figure out which 'ole and click I should be good to go.

 

[presta]

In an era when cars are full of electronics draining the battery whilst they're stood unused, and drivers are encouraged to leave the car at home as often as possible, you'd think the manufacturers would be putting something in the handbook about how long you can expect a fully charged battery to last. Or perhaps not. It won't go down well admitting the cars are likely to leave owners in the lurch.

 

[swee'pea99]

Ok, so the battery's back in - without any kind of top up since I charged it on Thursday evening - and the engine burst into life at first prod, with great gusto. So based on

However a battery that stays above 12.6V for a long period would be a good indication of being good. The battery will fall away from above 13V because that is peak voltage charge. Nominal is 12.6V. If its still above 12.6V for a few days and it spins the engine over quickly when you re install it-good battery.

I'm thinking the battery's a good'un.

I then had a go at the amps thing, and...

With the lead in the middle - 'up to 200mA' hole, not a flicker, anywhere on the dial.

With the lead in the left hand hole, and starting with the 10 ('don't overload it'), I was quite surprised to find myself looking at

At first glance, it looks to me like I'm reading 0.22, where I wanted to be no higher than 0.05. Which suggests a major parasitic drain somewhere in the car. Or am I barking up the wrong terminal?

 

[Biker BoB]

Dead short somewhere. Most likely starter motor

 

[CXRAndy]

I take on board the perils of measuring inline current

Start on the 10A scale.

When you lock a car, the vehicle goes into a shutdown process. The first few seconds to a minute, you may see a few amps being drawn, this should quickly fall to less than 1 amp, and keep falling until the vehicle is in sleep mode. Each car is different in the period it takes to shutdown fully, some take only a few minutes, other 30-40 mins.

I'd leave the meter attached for a good half an hour before assessing the vehicle sleep mode drain

 

[presta]

With the lead in the middle - 'up to 200mA' hole, not a flicker, anywhere on the dial.

....because you've blown the fuse in the meter, because you didn't...

start with the 10A range first until you know the current is below 200mA

....like I told you to.

What's the battery capacity, if it were say, 50AH, that current is enough to completely flatten it in 9 days, so you'll be struggling to start it in less than that.

Dead short somewhere. Most likely starter motor

Starter motors draw hundreds of amps, not 220mA.

 

[presta]

I'd leave the meter attached for a good half an hour before assessing the vehicle sleep mode drain

There's a 10 second limit on the 10A scale.

 

[Biker BoB]

@presta
When a starter motor dies it trickle drains the battery when it's not being used.

 

[CXRAndy]

There's a 10 second limit on the 10A scale.

If there is a parasitic drain of more than 10A the meter won't last. The battery would be flat in less than a day.

It's normally 1-2A after locking the car, then a quick fall into milliamps, then less than 50mA a minute or so later

 

[swee'pea99]

Well, I never heard of shutdown processes, but now I have I went out and redid the check, exactly as above, an hour or so ago, when I got the 0.22 readout, and...

Much lower. Also, arguably interestingly, all over the place. Fluctuating constantly, between about 0.06 and 0.12. I'm curious about the variation - I would have thought if there was a drain it would be consistent. Apparently not. But assuming it averages out at about 0.09, that's around twice what I've heard is 'to be expected'/acceptable. And would probably account for the battery losing its grunt over a few days.

I'm thinking, as a quick & dirty solution, fit the solar panel, hard-wiring it to the battery terminals so it's isolated from the battery isolator, as per Gwylan's tip up-thread, then simply add 'bip battery' to the regular startup routine. Sounds a belter, eh?