I use one of these
Not the greatest in the world, but it works well enough for my purposes.
You could go with this for $10, if you just want to use it just for your bikes:
But I would recommend this one for $20 that would also work well for your cars:
LONG MAY YOUR BRICK FLY!
Ride Safe, Ride Far, Ride Often
Lee Fulton Forum Moderator
3 Marakesh Red K75Ss
Mine, Hers, Spare
I tried the pump first. Bigger load. It wouldn't do anything. Then tried the light bulb because it was in fact so puny. I also tried a 2.5 amp MR16 bulb which when attached dropped the measured voltage to less than one volt. An H4 high beam at about 4.3 amps pulled it down to something approximating .1 volt.
Lacking a real load tester these different loads were sufficient to tell me in certain terms that the battery was headed to the recycler. But I just found it weird that the difference between the standing no load voltage and the .5 amp load voltage was so striking. I have had broken connectors or similar inside batteries before where the thing actually went open between the two posts - ie - I got no voltage reading whatsoever. This I understand. But the 12.7 down to 4 with minimal load is what I wanted to understand.
A complete battery test consists of a load test and a capacity test.
Even those "conductance" testers do not provide the whole story. I've connected them to batteries only to have them indicate a healthy CCA, battery voltage and even a "Good Battery" indication...this from a 100 Ah battery that only has 25 Ah of capacity.
Do you use this battery in Texas? Have you checked the battery voltage under various conditions when it is 100F outside? Chances are you are overcharging the battery and it is now dry. Now you know why I mounted a voltmeter on my GS and Porsche which is wired directly to the battery.
That is the problem with VRLA batteries; AGM or GEL. You can't afford to have them gas due to overcharging because what is lost cannot be replenished...as in being able to add distilled water as you can in a flooded lead acid battery.
Another fact about battery life, ever 8C (15F) increase above 27C (80F) decreases battery life in half. Run a battery in 110F temperatures and it lasts 1/4 as long as it does at 80F. Vibration is the other battery killer.
BTW, invest in a carbon pile 500A load tester from Harbor Freight. A load test is done at 1/2 the CCA rating of the battery for 15 seconds with voltage decreasing no lower than 10.5V...this test is done on a fully charged battery.
Paul, the following chart shows battery charge and float voltages based on battery temperature.
As you can see, you hope your voltage regulator temperature compensates. An on-board voltmeter will tell you that.
car's and bikes i change every three years, do not want to get stranded. that being said my airplane lives with a seven year old battery it gets a 30 minute charge every day. play it safe..
What puzzled me was the failure mode. I've had the dread Yuasa snap-pop dead zero volts. I've had the slow but sure loss of capacity. But I have never had one act quite like this one did - described in posts above. I was trying to figure out the failure mode is all.
East Penn Technical Manual. Note pages 9, 11 and 12.