battery or alternator?

[Deleted User]

Paradigm wrote: »

Year old fuel stored in the cars tank is way, way past it's best... especially if it's an ethanol blend (all modern petrol I believe)

The cars tank isn't airtight & ethanol attracts water... could be why it's cutting out (faulty alternator aside)

Yeh I know. Someone suggested filling it up to at least dilute it with decent fuel.

Although saying that it seems to run ok otherwise.

[Deleted User]

Robisere wrote: »

A battery that has been idle for a reasonably long period of time begins to "Sulphate" - sediment builds up from the plates and its efficiency is very much reduced. It will never recover full charge. If you did connect the battery the wrong way round, you reversed the polarity, which may well have destroyed the diode pack in the alternator, so you may have two problems, as has been said.

If you check the battery with a multimeter, take the caps off the battery cells, but DO NOT lean over the battery whilst you do so (fumes which are potentially explosive - no sparks please!) Note the reading, then remove the tester and look at the cells. Are they gassing? (Bubbles coming up through the electrolyte) If so, there is enough life remaining in the battery to pass sufficient starting current. Is the level of electrolyte in the cells low? If so, get some distilled water from a parts shop/garage and top it up, but only to the level shown in the battery. Don't forget to replace the battery caps!

If you have access to any "jump Leads" you can ask a friend with a car to run them from his battery (whilst his engine is running) to yours, then after a few minutes, try to start the Mini. Fortunately the old Mini was uncomplicated, without so many of the modern electronics that can cause problems.

Good Luck!

Im wondering whether I've got a duff battery and alternator problem here.

I've been starting it with a mobile jump pack thingy. So it starts ok using this every time - dies after few mins.

forgotmyname

A totally dead battery wont charge with an alternator. You need an old fashioned charger that pumps the voltage into the battery without trying to do clever stuff and regulate the charge.

The battery maybe dragging the voltage down. Or it maybe a faulty alternator as well.
You need to start with a decent battery though.

Strider590

Please do not keep trying to charge that battery..... A dead battery, with several dead cells (which you clearly have), will kick out a sh*t load of hydrogen gas when subjected to a 14v charge. It sounds like you have 3 or 4 cells out of 6 working.

You risk causing an explosion, one that involves flying bits of plastic, lead and boiling hot sulphuric acid.

For the price of a battery, it's just not worth the risk.

bigjl

First port of call is make sure all the cells are full.

Then trickle charge the battery for at least a day.

An alternator will never charge up a dead battery it is only meant to replace what the vehicle uses.

At tickover a battery can actually go flat as very little if any charge is produced.

If after a good trickle charge it is still knackered then it is new battery time

AdrianC

[quote=[Deleted User];65560476]7.5v no more when running.[/QUOTE]
So there y'go. Not being charged. You should be seeing 14v or so with the engine running.

Whether the battery's dead or not is a separate issue, as is cause-or-effect. But it's not charging...

Slowly_does_it..

Sorry, if 7.5V when running, your alternator is not working. Anything from the belt has broken to needing a new alternator.

A battery that has been flat for a year is also nearly certainly dead, but no harm done in taking it out, checking cells have enough water, and charging it properly.

Joe_Horner

7.5v is very low for a 12v battery. It might recover a little with a long trickle charge but it's unlikely (and I'm the one who's normally advocating saving them if at all possible on here!)

7.5v when running means nothing is coming out of the alternator. That may be a wiring issue but connecting the battery the wrong way on these will blow diodes if the battery had any power in it at all.

The way the diode pack is wired it present a dead short to a reversed battery so, with any sort of charge in there, you'll get the maximum current the battery can supply ( which could be a couple of hundred amps through 40 or 50 amp rated diodes) for a few hundredths of a second until one or more of them fails.

Still, a classic Mini has to be worth a battery and alternator!

Stoke

Robisere wrote: »

A battery that has been idle for a reasonably long period of time begins to "Sulphate" - sediment builds up from the plates and its efficiency is very much reduced. It will never recover full charge. If you did connect the battery the wrong way round, you reversed the polarity, which may well have destroyed the diode pack in the alternator, so you may have two problems, as has been said.

If you check the battery with a multimeter, take the caps off the battery cells, but DO NOT lean over the battery whilst you do so (fumes which are potentially explosive - no sparks please!) Note the reading, then remove the tester and look at the cells. Are they gassing? (Bubbles coming up through the electrolyte) If so, there is enough life remaining in the battery to pass sufficient starting current. Is the level of electrolyte in the cells low? If so, get some distilled water from a parts shop/garage and top it up, but only to the level shown in the battery. Don't forget to replace the battery caps!

If you have access to any "jump Leads" you can ask a friend with a car to run them from his battery (whilst his engine is running) to yours, then after a few minutes, try to start the Mini. Fortunately the old Mini was uncomplicated, without so many of the modern electronics that can cause problems.

Good Luck!

I know someone who did this. Garage changed alternator, and battery, never thought of diode pack. Very expensive lesson there.

[Deleted User]

AdrianC wrote: »

So there y'go. Not being charged. You should be seeing 14v or so with the engine running.

Whether the battery's dead or not is a separate issue, as is cause-or-effect. But it's not charging...

So just to clarify - with engine running, battery connected, I should be seeing 14v using multi-meter between terminals? regardless of battery state?