battery issue

[dj2k21]

Hello,

ongoing problem if I leave the mr2 stood for more than a week the battery goes dead, I dont think there is anything on the car drawing power when ignition is off, the car does have a nissan micra battery fitted as its in a battery box in the front of the car, measured it today, and its only giving out 2 volts! normally I stick my charger on it overnight and its fine, but this time its popped 2 fuses in my charger, so I removed the wires from the battery, stuck it on charge again and its charging fine! another thing to add is that I bumped the car off yesterday and it was running rather lumpy, my lights wouldnt work and the speedo wasnt working either, could it be a dodgy alternator do you think? been thinking of putting a higher output one on the car due to having things like EDFC, New gauges, stereo etc etc and now its got a smaller battery maybe im not giving it the runs it needs to charge it>?

[normanh]

If your voltage output is low I think the ignition light (engine light?) is likely to come on - was always a rule of thumb and easy way to know if the output voltage was there as it needs to be greater than that of the battery to effect a charge.

I might be wrong on this ?

norman

[Dyn-Evo]

Car batteries are a thing of mystery....!   s:? :? s:?  

They can let you down at the drop of a hat, for no apparent reason...and you can't really do much to fix them.....!

Personally, I would replace the thing if its over 3 years old: sounds like you may have a shorted plate(s) internally, perhaps?   s:? :? s:?  

For reference, my V6 was not started for over 3 weeks recently: when I tried to start it on a fairly cold morning, it DID turn over very slowly, and did start up....

That was about 2 weeks ago: yesterday I tried to start it, and I got the oscillating relay / no startee....!   s:lol: :lol: s:lol:  

So, it lasted about a month, with the alarm armed the whole time.

Batteries tend to fail a lot more regularly than alternators: if you have 12.5v on the battery when the engine is off, and around 14.5 when running then your alternator would appear to be working.
If you have 16v+ then you have a failed regulator diode, and you'll be gradually frying your battery......even though you'll not realise until you measure it, or the battery dies!
This will also invariably manifest itself as your battery not holding charge for long: you can easily check this by connecting a DVM set to "Amps" in SERIES with the "+" terminal.
(ie: disconnect the "+" connector, connect the red DVM probe to the battery terminal and the DVM black probe to the connector)
This will show any current leakage when the car is standing: should normally be in the order of around 25mA, maybe a little more depending on what you have in the car.
NOTE: DO NOT TRY TO START THE CAR WITH THIS SETUP!   s:wink: :wink: s:wink: