Battery or Alternator trouble?

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Ciaoflyer
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Battery or Alternator trouble?

Post by Ciaoflyer »

Hi Guys, just rebuilt the engine on my '88 T25 DJ 2.1 and it runs great!  However, I am having starting issues..

1:  Fully recharged the battery that came with the van, we have owned it 5 years
2:  Battery started van but turned the started slowly
3:  Did not run the engine for a month battery dead (Reads 11.6 on multimeter and drops to 3.2 when turning key)
4:  Jumped van off other car, van started and ran well
5:  Multimeter on battery when running to test charge, 12.97 to 13.2, so charging but not a lot.

So, is the charge low because the battery is totally flat or is my alternator shot or both?

Battery is a VARTA Blue Dynamic  E43 12V 72AH 680A - deff older than 5 years

Thanks

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King Kenny
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Re: Battery or Alternator trouble?

Post by King Kenny »

Difficult to say for sure, but I would suspect the battery. You could take the battery to a garage who can do a drop test on it and give you a good idea of its condition.
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Cecil
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Re: Battery or Alternator trouble?

Post by Cecil »

How long was the battery sat without being charged whilst the engine was being rebuilt ?

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Mocki
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Re: Battery or Alternator trouble?

Post by Mocki »

You need to charger that battery fully with a mains charger ,a  alternator Will only ever charge a lead acid battery to about 80% .
once you have a fully charged battery , pop down to Kwik fit or halfrauds and request a free battery check, for which they will give you a print out ( tell you you need to claim on warrentry and you will get back to them) 

you can’t successfully measure the alternator out put into a half flat battery with voltage readings , but once it’s fully charged , take a volt reading at the back of the alternator, with the alternator casing as the neg connection 
then take a reading at the battery , if it is more than half a volt lower at the battery , you have a wiring or earth issue ....
ideally you should be getting 14.5v at the back of the alternator at tickover ( no point revving it , it’s a alternator not a dynamo!) if you are getting less than 14v then change the brush pack .
Steve
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Ciaoflyer
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Re: Battery or Alternator trouble?

Post by Ciaoflyer »

Thanks for this detailed reply! I’m on the case! :D

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nicq
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Re: Battery or Alternator trouble?

Post by nicq »

Mocki wrote:
15 Jul 2020, 21:19
You need to charger that battery fully with a mains charger ,a  alternator Will only ever charge a lead acid battery to about 80% .
Why is this.
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Mocki
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Re: Battery or Alternator trouble?

Post by Mocki »

Because basically a lead acid battery will take a long while at a trickle to accept that last 20% , something a alternator cannot deliver , so while it reaches its maximum voltage it does not reach its maximum charge .
 
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nicq
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Re: Battery or Alternator trouble?

Post by nicq »

So that's interesting, so old chargers that are fixed voltage you reckon never really fully charge batterys.
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Mocki
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Re: Battery or Alternator trouble?

Post by Mocki »

No, old chargers keep putting it in ,and if you leave them on long enough they get there , where as alternator will see the max voltage and amperage will drop , but you won’t ever drive long enough to get the last bit in  it takes a long while to put the last drop in 
newer intelligent chargers look at the battery and alter what they are doing , so achieve full charge much sooner 

So, there ( should be ) three stages of charge for a flooded lead acid battery , 
1. Bulk - where 70% of the charge is achieved quickly 
2. Topping up (Absorption) where the remaining charge is achieved slower 
3 . Float , where the voltage is dropped to 13.5v and the battery is maintained 

a  old school alternator cannot manage the second and third stages , a old school mains charger cannot manage the third stage 

 
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Ciaoflyer
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Re: Battery or Alternator trouble?

Post by Ciaoflyer »

Thanks for these replies.  I am going to replace the battery due to its age and not holding any charge.  What battery would you guys recommend or shall I fit the same one?  This is the one installed currently:

https://www.tayna.co.uk/car-batteries/varta/e43/

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Re: Battery or Alternator trouble?

Post by Ciaoflyer »

Good news, cleaned all wire connections, replaced voltage regulator and put in new battery, now metre says 14.1 at the battery! Thanks for help all!

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