Cruisers & Sailing Forums - View Single Post - Evaluating 12V flooded-cell batteries

btrayfors · 07-02-2008, 13:02

Rick,

Thanks for your detailed post re: evaluating old batteries.

I'd be very interested if you could tell me from the graph below:
Gallery :: Miscellaneous 2007 :: VoltageDecayComparison

what your evaluation method would come up with in terms of capacity.

FYI, these were batteries used in a 12-month plus test of pulsers. The gelled golf-cart batteries were over 10 years old (had been removed from a sailboat), and the T-105's were about 3-4 years old but not performing very well.

My interest is peaked in your calculations, because I have estimates of capacity of these battery banks (of 2 each) derived from direct measurements using a $600 internal resistance computer.

Would be fun to compare :-)

Thanks,

Bill

BTW, the voltage measurements were taken with a calibrated Fluke 189 meter; the "load" consisted of several 12V light bulbs in parallel (and measurements were taken of amperage, AH, and KWH).

Note also that the T-105s actually show an INCREASE in voltage after 15 minutes or so. This is typical of the behavior shown, i.e., their voltage drops way below what you'd expect, then picks up a bit. Here's a graph of the first 20 minutes of each battery bank:
Gallery :: Miscellaneous 2007 :: First20MinsLoad

B.

07-02-2008, 13:02	#7
btrayfors Senior Cruiser Join Date: Jul 2006 Location: Chesapeake Region Boat: 42' Bob Perry sloop, "Born Free" Posts: 1,242	Rick, Thanks for your detailed post re: evaluating old batteries. I'd be very interested if you could tell me from the graph below: Gallery :: Miscellaneous 2007 :: VoltageDecayComparison what your evaluation method would come up with in terms of capacity. FYI, these were batteries used in a 12-month plus test of pulsers. The gelled golf-cart batteries were over 10 years old (had been removed from a sailboat), and the T-105's were about 3-4 years old but not performing very well. My interest is peaked in your calculations, because I have estimates of capacity of these battery banks (of 2 each) derived from direct measurements using a $600 internal resistance computer. Would be fun to compare :-) Thanks, Bill BTW, the voltage measurements were taken with a calibrated Fluke 189 meter; the "load" consisted of several 12V light bulbs in parallel (and measurements were taken of amperage, AH, and KWH). Note also that the T-105s actually show an INCREASE in voltage after 15 minutes or so. This is typical of the behavior shown, i.e., their voltage drops way below what you'd expect, then picks up a bit. Here's a graph of the first 20 minutes of each battery bank: Gallery :: Miscellaneous 2007 :: First20MinsLoad B. Last edited by btrayfors; 07-02-2008 at 13:10.