ravingfool
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| posted on 20/4/15 at 09:47 PM |
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alternator/battery recommendations
OK
.Have had the striker for a few weeks and busy fault finding to improve things.
At the moment it's running an unknown alternator (I may be able to work out what it is by having a proper look) and a tiny lightweight varley
battery.
Day to day it manages just about with this combination but leave it for a week and the battery seems to have lost a little power and tends to need a
jump. More importantly, running with lights it seems to not generate enough power to recharge the battery.
Digidash shows voltage dropping from 14.4 to 13.something running with lights and then not enough to restart. Even with the battery reading 14.4v it
only seems to have enough power for a quick crank (normally sufficient to start).
I suspect that the battery needs replacing as I got the impression that the car didn't get much use previously so probably not at its best and
I'm thinking of getting something a little bigger but as it doesn't seem to be charging I'm thinking about an improved
alternator.
What do people find to be a good combination?
I want a reliable setup that's going to give me enough power for lights!
In case it affects considerations it's a 2lt blacktop zetec on standard Mondeo ignition setup.
I'd welcome any thoughts before I have a play with it at the weekend!
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britishtrident
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| posted on 21/4/15 at 06:18 AM |
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While it sounds like both the alternator and battery are U/S a duff alternator having killed the Varley a couple more diagnostic checks might save
you money, the first is to watch what happens to the battery voltage under starter load. Charge the battery then let it sit off charge for a couple
of hours (12 hours is better) then connect a volt meter and watch the battery voltage as you turn the starter, dropping instantly below 9.6 volts
right down to to 6 volts indicates the battery is toast.
If it passes this test then check the earth lead resistance --- there are two ways to do this either measure the voltage between the battery negative
and the cylinder block when you crank the engine on the starter: it should measure only about 0.02v or use a good quality set of jump leads to make
a connection between the battery negative and the cylinder block.
The other test you should do is check for parasitic current draining the battery, the easy way to do this is charge the battery and leave
disconnected from the car for a week and see what happens. Often parasitic current can be caused by leaking alternator diodes.
If it passes this test the alternator may just need a new set of brushes which can be quite easy and cheap to fix.
Generally a battery for a 2litre petrol engine needs to be be rated at 500cca (a fairly big battery a type code 075 or similar) you can use smaller
for car used only in summer but the smaller the battery the shorter it will last. I would not advise going below 340 cca 35ah.
My personal choice would be a type code 063 Excide or Varta http://www.tayna.co.uk/EA472-Exide-Premium-Car-Battery-063TE-P7496.html
[Edited on 21/4/15 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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ravingfool
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| posted on 21/4/15 at 11:45 AM |
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Thanks BT, that's really helpful information.
It was too dark by the time I got home last night to take a look at what the current battery specs are but with a quick look online I suspect
I'm currently running a 15AH varley redtop (it really is tiny) which rather explains why it's only good for a quick crank and if the
engine doesn't catch absolutely instantly the battery is then too flat for another attempt.
I appreciate the advice re capacities and also the suggestions for checking for parasitic loss and that the alternator is working properly -
I've never done those things before so will pull the multimeter out for that at the weekend.
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britishtrident
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| posted on 21/4/15 at 12:31 PM |
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I think it is most likely a case of a new battery and the alternator needs a set of brushes.
Sadly Varleys tend to have a short life in cars, testing batteries and alternators is easy with the pro test gear but you can do a lot with just a
multimeter it just takes longer.
One thing to watch is amps measuring with digital multimeter is usually limited by the internal 10amp, if you blow the fuse it will just read 0.00
amps and the volt range will be unaffected so you can get a false current reading and be none the wiser.
The cold cranking amps is really measure of starting reserve capacity of a battery before the voltage falls below 7.2 volts.
When new a 400cca battery would produce 400 amps for 30 seconds at -12c before the battery drops below 7.2 volts. However modern cars the ECU needs
at least 9.5 volts to start the car, which one of the reasons modern cars have bigger batteries. Battery capacity goes down with use and after a
couple years service even a good well looked after 400cca battery would in real life be closer too 300cca.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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