Quote:
Originally Posted by macafee2
when i put the spare battery on charge it went to showing fully charged and i am going to assume it is good enough to start one car once
|
Hi Ian, thanks for your reply.
Unfortunately your assumption may be unreliable. Unless your "spare" battery receives a frequent maintenance charge, it is likely to become sulphated. This means that although it may illuminate a "fully charged" indicator, many of the plates may be rendered useless so, in fact, only a proportion of the battery is fully charged. In this condition it is unlikely to start a car and particularly when placed in parallel with the vehicle's discharged battery.
If you put your voltmeter across the "spare" battery and operate the starter, a voltage of below approximately 10.5v suggests that the battery is sulphated if it previously gave a "fully charged" indication.
To guarantee that a "spare" battery will be useful whenever needed, leave it permanently connected to a smart maintenance charger. I recommend C-tek as they are well made and very compact but there are other choices.
Simon