Cranking trouble! What size battery?

Hi,
I have just brought my first landy. A SR2a 1969.

What size battery should it have. Its got a halfords special which says 550cca. Not sure if this rings true.

If its just stopped it will crank fine and start but if its left it hasn't got enough power and needs jumping.

i know this sounds like a duff battery but its only a few months old.

I was wondering if i need a bigger battery or if i should have two in series.

Any help would be appreciated.

Thanks
Rob

Take the motor in and ask em to do an alternator check - it sounds like it aint being charged proper.

have you thought of also checking the carbon brushes in the starter motor, but as the mad hat said have the alternator checked, or as it got a dynamo fitted, simple way to check the alternator is put a volt meter on it when the engine is running, but with out knowing what the alternator or dynamo is putting out you could end up replacing parts that dont need replacing and the fault is still there.

checking with a voltmeter wont work - I have seen two alternators in the last fortnight that were showing good volts but excessive ripple ( caused by smoothing diode failure). this will not show with a voltmeter test and will mean that the alternator will not supply any CURRENT to charge the battery.

Its just had a new alternator fitted but will get it checked.

Does that battery sound ok or should it have a bigger 1?

shud be ok, but rule of thumb is go for biggest you can.

Do you know the best place to get a big battery thats not to expensive. I know halfords will be bloody expensive!!!

See post #5 on this thread from a couple of days ago. good luck.
http://www.landyzone.co.uk/lz/f6/battery-prob-84163.html

ive got the same problem with mine have to cargh the battery every couple of days had my alty cecked and it was putting out 13.84-13.88 but its a small battery (wots a smoothing diode ???)

herbie 66 said:

(wots a smoothing diode ???)

Click to expand...

A smoothing diode is one of four diodes in the back of an alternator that make up a 'bridge rectifier' (google it if you're interested) which is an electrical device that turns Alternating Current (as supplied by a bare alternator - the clue is in the name) into Direct Current (which your car runs on). They're a relatively common failure.

It is possible to check each diode in turn, a diode passes current in one direction but not the other. It is also possible to replace each diode if you're handy with a soldering iron, although it's generally easier to replace the entire alternator - last one I replaced was only about £25 IIRC.

I'd also be tempted to check whether you have a wiring problem or a permanent load on the wiring ... try disconnecting your battery when you're not using the Landy and see if it still discharges.

this is the sort of thing you are looking for - at the back of the Alternator.

There are actually 9 diodes in the rectifier on a lucas alty, 6 are the main bridge tht charge the battery and the other 3 supply the internal regulator electronics and control the alternator warning light.
If one 'phase' or more fails then ripple current increases and it can give a misleading reading, one simple check is run the engine for an our or so on a known charged up battery, then stop the engine, leave it for 20 mins then check the volts, 12.5 or higher is good, any less indicates a problem.
Most multimeters have a diode test, stick the leads accross the diode, one way round will show 'oL', and the other way should show between 0.5 and 0.65, if you get 0.0 either or both ways round the diode's knacked.

thanks you learn somthing new every day gonantry diconecting the battery and see

Something I do when disconnecting a battery, look for sparks when you momentarily cannect the battery, if there is then its a rough indiaction of a power drain.
Stereos can give a false impression with this though, if you've a meaty radio then the inrush which is normal will create a fair spark.