Sunday, Jan 11, 2004 at 01:35
Eric, Eric, Eric, I wish you had taken the trouble to
check before firing off the remark that a voltmeter is unsuitable to
check a battery status.
The internet is such a wonderful resource, especially the 'google' search engine.
I have looked up a reputable deep cycle battery manufacturer - Trojan - to see what they have to say on the subject.
See for yourself at:
http://www.trojanbattery.com/customercare_batterymaint4.html
You'll find they first recommend the hydrometer
test, as I also mentioned, but as this is a bit tricky and temperature dependant they also give a table for a voltage
check. Note that the difference between fully charged and just about dead is less than a volt. Something a $20.- digital voltmeter has no trouble differentiating - even the cheaper ones read to two decimal
places - easy to see if its 12.4V or 12.55V!
What the Trojan suggests as a waiting period after charging (6 hours) before measuring is possibly much better for a true indication of charge but one gets a good idea of it after at least 1/2 hour after disconnecting.
What you say about that a battery measures "always 12.6V" is plain nonsense.
What you say about submarine batteries may have been correct way back when you were presumably in submarines and the digital volt meter was not yet invented.
Note that I said 'use a DIGITAL voltmeter to
check the battery charge'
The old analog (pointer) type meters are useless for this.
These days submarines more likely use a sophisticated computer to determine the charge state of their batteries
I happen to know a bit about this subject and still think that just banging in 5 Amps for 10 hours into a dead 50Ah battery is bad advice. You might have gotten away with that on your battery but not all batteries take that kindly.
Best advice I can give is: NEVER let a deep cycle battery become completely discharged - this will drastically reduce its useful life.
Best to keep it above 50% charge at all times while using it and storing it at 100% charge with frequent topping up.
Klaus
FollowupID:
304944