Technical Alternatator/battery replacement

[Hharbers]

My 1987 panda 4x4 seems to me a little low battery voltage:
Engine off 12.2v / idle Engine 13.3 v/ rev 13.7v
To my information battery should have at least 12.4v off

Is battery and (or alternator) dying?

Current 44ah battery is installed by previous owner and a dont know age.
According to manual stock was 30ah

I want to install in future a winch. So if i need to install new battery I want be ready to power a winch

Will a 55ah battery like Varta blue cC22 or Bosch S4 002 be a good choice?

I have a spare alternator that looks new to me according to specs it can deliver 65a. Better to fit this to power battery when winching?

 

[Dragon Man]

as fiats go, it seems normal to me. my panda charges at 13.8v dead on. sometimes i see the battery voltage at 11.9v when i come to it in the morning! it still starts well though.
i am running an alternator from a mk1 fiat punto which is 95 amps. (the one that has electric everything and electric power steering) i also have a larger battery fitted too.

 

[ZaphodB]

The battery might just be reading a little low because it's aged not because your alternator isn't up to it , a battery in good condition should have a resting voltage of about 12.6v (~30 mins after turning the engine off)
Look for a date code on the casing.

Will a 55ah battery like Varta blue cC22 or Bosch S4 002 be a good choice?

Any battery that will physically fit will work, and that physical size will be what limits its Ah capacity.
The alternator isn't related to the battery capacity per se, more the overall vehicle load.

I'd get the battery properly drop tested , and it'll probably 'fail' from that resting terminal voltage.

 

[Pugglt Auld Jock]

The battery might just be reading a little low because it's aged not because your alternator isn't up to it , a battery in good condition should have a resting voltage of about 12.6v (~30 mins after turning the engine off)
Look for a date code on the casing.



Any battery that will physically fit will work, and that physical size will be what limits its Ah capacity.
The alternator isn't related to the battery capacity per se, more the overall vehicle load.

I'd get the battery properly drop tested , and it'll probably 'fail' from that resting terminal voltage.

If you are going to get it "drop" tested then there's basically two ways this can be done. The old way is to use a load tester which is a device with a robust resistance applied between two probes. It has a voltmeter which reads the voltage at the battery terminals. With the battery well charged - but allowed to rest for say an hour after charging. ie, don't test it immediately after having it on charge. Letting it rest overnight is even better. This draws a large current, typically around 100 to 150 amps, from the battery. As the test is taking place you observe the battery voltage and it shouldn't drop off quickly or get too low either. You wouldn't want to see it dropping below 9.5 volts with the tester applied. Because large currents are involved there are risks to using a traditional drop tester. You can get sparks - never good around a battery which will be emitting flammable gasses and it puts the battery under great duress so not ideal for a battery which may be suspect anyway. On the other hand, if the battery is dodgy it'll quite often do for it so leaving you in no doubt you need a new one!

The more modern way to do it is to use a battery condition analyser which is a device which connects to both battery terminals and passes a relatively small current through the battery and measures the internal cell resistance. This way of testing carries no risk of damaging the battery and can also be done with the battery still in circuit on the vehicle without any worry that electronics on the car may be affected in any way. Both our local Halfords branches use this method and will check the battery condition free of charge - I've found them very helpful and not at all "pushy". If the battery is Ok they say so and don't try to sell you a new one.

When Becky (1010 1.2 Panda 169) needed a new battery a few years ago I replaced it with a Yuasa silver 5000 HSB 012 rated at 54ah with a cold cranking amps of 500 (en) which was pretty much the biggest that would fit and, the one it replaced was rated at 50ah but only 350 CCA (en) so a useful upgrade. I am in the habit of checking battery standing voltage quite often, when I'm doing levels checks mostly, and it used to sit at around 12.6/12.7 volts when new. Now, maybe 4 or 5 years down the line, it typically shows 12.4 volts after sitting overnight. starts and runs very well. My Scala, which was a pre reg purchase and I suspect sat around in the docks at Glasgow for quite a few months without being started - only had 9 miles on the clock when I drove it away - has never looked so good and now, at about 21 months old, typically shows 12.2 volts. That is a little low but she starts and runs absolutely fine. I have had her tested at the local main dealer, but, unsurprisingly, the report was that all was well! The battery is covered by warranty so I've got just over another year before that runs out and am hoping that if its going to fail, it jolly well gets on with it before the warranty runs out!

 

[ZaphodB]

The more modern way to do it is to use a battery condition analyser which is a device which connects to both battery terminals and passes a relatively small current through the battery and measures the internal cell resistance.

They don't inject a small current, they simply check open circuit terminal voltage and then terminal voltage with various small known loads and are able to extrapolate those results to estimate/plot the internal resistance (the curve isn't a straight line as the loads increase just because of the chemistry of the battery)

See https://learn.sparkfun.com/tutorials/measuring-internal-resistance-of-batteries/internal-resistance for an overview of a manual check.

The internal resistance is why the terminal voltage drops lower and lower as the load increases (current x resistance), disregarding the natural drop as the charge decreases.

 

[Pugglt Auld Jock]

They don't inject a small current, they simply check open terminal voltage and then terminal voltage with various small known loads and are able to extrapolate those results to estimate/plot the internal resistance (the curve isn't a straight line as the loads increase just because of the chemistry of the battery)

See https://learn.sparkfun.com/tutorials/measuring-internal-resistance-of-batteries/internal-resistance for an overview of a manual check.

Thanks Zaphod. I'm not great with the actual "how does it work" when it comes to electronic devices. I like the idea of these modern testers, especially as they can be used without having to disconnect the battery from the vehicle, and am looking into which one I'm going to buy. Of course I don't need to know how it works, and had gathered what I said above from reading "stuff" on the internet - more fool me! Anyway, I've not been very well through the night - tummy problems, Yuk! so I'm taking it easy this morning. Going to settle down to reading the link you posted now.

 

[ZaphodB]

Thanks Zaphod. I'm not great with the actual "how does it work" when it comes to electronic devices. I like the idea of these modern testers, especially as they can be used without having to disconnect the battery from the vehicle, and am looking into which one I'm going to buy. Of course I don't need to know how it works, and had gathered what I said above from reading "stuff" on the internet - more fool me! Anyway, I've not been very well through the night - tummy problems, Yuk! so I'm taking it easy this morning. Going to settle down to reading the link you posted now.

No, the modern ones are good, and I agree the drop test of old is a brutal (but good test) , no intermediate loads, just straight in at the jugular

The modern day testers get to the same result more or less, but can only test the lower end of the curve which indicates what's happening at many amps

 

[Pugglt Auld Jock]

No, the modern ones are good, and I agree the drop test of old is a brutal (but good test) , no intermediate loads, just straight in at the jugular

The modern day testers get to the same result more or less, but can only test the lower end of the curve which indicates what's happening at many amps

When in the trade, way back, you only had the "Brutal" type and they certainly sorted the men from the boys! Seen a number of accidents involving them too. I'm very used to using this type and am tempted to get one - This sort of thing:- https://www.ukplanettools.co.uk/battery-drop-tester-12v-bt91-3.html Quite pricey though? Then there's more DIY oriented types like this https://www.sealey.co.uk/product/5637185981/battery-drop-tester-612v Generic versions of which seem to be available for not very much money - don't know how durable these cheaper ones are though?

I've read a number of reviews of the analysers and come to the conclusion that the cheapest ones, which are still more expensive than a cheap load tester, can be quite inaccurate. Expensive ones, recommended for "trade" use, can be quite pricey though and include things like a results printer - which I don't need. So, plenty to keep me busy making my mind up about.