Club 80-90 Forums

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

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.

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

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 .

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

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.

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 .
 

So that's interesting, so old chargers that are fixed voltage you reckon never really fully charge batterys.

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 

 

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/

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!

A point to make about Varient derived engine Bays is that the alternator output wire is maybe too thin. This might have been done to get itself through the 2 large grommets, one in the back of the alternator, the other on the right hand cylinder bank tinware, where the whole loom passage is tight. A cure is to run another wire the same size as the first alongside to the live starter solenoid terminal. This practice was also done on the Golf C models pre 1987. A comparison with the main fusebox feed wire (the fat red/white one) should give this point.