wopachop wrote:
I got to take some of the blame as it happens to me a lot on forums. I write big long confusing posts and some people dont absorb it correctly. It seems like time2roll followed along just fine. While others are yelling at me saying 12.64v is not fully charged. I was hoping we all agreed im closer to 90% charge from the 5a battery tender and the main question of the thread is should a 4a load make the batteries drop to 12.4v?
Umm, hate to tell you but THAT is not the way you go about checking your battery capacity, hence the posts TELLING YOU THIS..
You START WITH A FULLY CHARGED BATTERY.
You don't start with a PARTIALLY DISCHARGED BATTERY AND GUESS WHAT THAT PART OF THE DISCHARGE IS AT THAT POINT IN TIME.
For instance, I just checked a group 24 battery that I use in an antique auto. I had recharged that battery a couple of weeks ago FULLY.
That auto does not have an alternator or generator to recharge the battery.
I have run that auto for about 2 hrs over the last two weekends.
That battery is powering only the coil and a rear single tailight.
Coil draws an average of 3A and the bulb about 1A.
So, I have used about 8Ahr from that battery.
I just checked the voltage of that battery, it READS 12.94V (averaged between three different volt meters).
Your "test" is not valid, you NEED to start with a FULLY charged battery. Then apply a known load, check and log voltages periodically during the test.
This establishes a BASELINE to work from.
Something else to consider, using a incadescent bulb as a "load" is not a good idea. The bulb current will not change in a linear fashion as the battery voltage drops and will mess with your results. Much better to use a RESISTER as a load, will still drop current as battery voltage decreases but gives a more predicable linear load to work with.
But personally, I DON'T bother with "testing" my batteries in such fashion. I don't stress over it and yet they give me a minimum of 9 yrs of trouble free service.. :B
Heck my last set could have gone MUCH longer, I only changed them out so I didn't have to worry about them not having enough life left while on the road..
But go ahead and do it "your way", it is YOUR "world" to play in..
