27DCs and SG Lag Problems
Here is what I mean. Got two rebuilt 27DCs from Interstate as "Econo Power" models, which means they are whatever brand and type they decided to renew and sell at under half price. So just right for my purpose. But first to get them up to speed at home same as any battery first thing off the shelf before using it.
The batts seem to be Johnson Controls, all black, weigh 58 lbs, and are marked 27DC-845. Original date 5F (assumed to be June, 2015)
Doing one at a time, put the VEC1093 40 amper on them and let it get to "Full", which I know isn't quite full. I then ran an Equalize as I normally do to get to "real full" and it ran for a couple hours at 15.7v until it said Full.
SG all across was 1.300, so looking good. Then I ran my 10 hour 20 hour rate load test in hopes of finding out what the AH capacity is of the mystery battery (no rating shown--the 845 is no doubt the marine cranking)
It did take 10 hours to get to 50% SOC at 5 amps (I picked 100AH as most likely result) and proved 50% by seeing 1.200 SG and bounce back overnight to 12.17 volts. AH down from full was 51.6 by Trimetric, so Capacity came out as 103.6 AH at the 20 hr rate.
Now the fun part--recharge from 50% after ONE deep draw down, never mind after doing several 50-90s in a row.
Put the charger on same as before starting at 40.4 amps and let it run at 14.8v till it said "full" Sure enough SG was only 1.245ish in the white. So ran an Equalize which took a couple hours at 15.7 and SG was now 1.260ish. Ran a second Equalize for another couple hours till it said Full, and SG now 1.265ish, just barely into the green.
Rats! This is just like old times with 27s :( I used to tip them on their sides at this stage to try to get them up to full SG. But today I have a new weapon I did not have eight years ago-- my PowerMax Adjustable that can do 16.5 volts (with 15 minute shots, so you have to be there to keep doing that. It drops one volt after the first 15 minutes, and then stays at that--15.5 in this case, so unplug and start again at 16.5)
So after two of those--30 minutes at 16.5, the darned SG has hardly moved up at all still 1.265ish. I decided to give it time to cool down when SG will go up a bit with colder fluid, and I will leave the batt on float overnight at 13.8 and give it another kick or two tomorrow.
So what's with these 27s anyway???? There they were at 1.300 and you do ONE drop to 50% and it is like pulling teeth to even get back into the green, never mind 1.275 or above. I hate 27s !!!!!!
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Background info--not needed unless you are bored :)
Eight years ago, I swore off 27s because of my difficulties getting them back to proper full as seen by hydrometer readings. No such problems with 6s or the Trojan 12v T-1275s I have been using since. They come right up. No fuss.
I just got these two 27DCs as a stop-gap for rounding out the battery bank now that my two T-1275s finally died, and I need two batts to go with my six-year old pair of 6s that are still going but for only another year most likely. (I need about a 400AH bank) Then next year I can start over with all new whatever.
The batts seem to be Johnson Controls, all black, weigh 58 lbs, and are marked 27DC-845. Original date 5F (assumed to be June, 2015)
Doing one at a time, put the VEC1093 40 amper on them and let it get to "Full", which I know isn't quite full. I then ran an Equalize as I normally do to get to "real full" and it ran for a couple hours at 15.7v until it said Full.
SG all across was 1.300, so looking good. Then I ran my 10 hour 20 hour rate load test in hopes of finding out what the AH capacity is of the mystery battery (no rating shown--the 845 is no doubt the marine cranking)
It did take 10 hours to get to 50% SOC at 5 amps (I picked 100AH as most likely result) and proved 50% by seeing 1.200 SG and bounce back overnight to 12.17 volts. AH down from full was 51.6 by Trimetric, so Capacity came out as 103.6 AH at the 20 hr rate.
Now the fun part--recharge from 50% after ONE deep draw down, never mind after doing several 50-90s in a row.
Put the charger on same as before starting at 40.4 amps and let it run at 14.8v till it said "full" Sure enough SG was only 1.245ish in the white. So ran an Equalize which took a couple hours at 15.7 and SG was now 1.260ish. Ran a second Equalize for another couple hours till it said Full, and SG now 1.265ish, just barely into the green.
Rats! This is just like old times with 27s :( I used to tip them on their sides at this stage to try to get them up to full SG. But today I have a new weapon I did not have eight years ago-- my PowerMax Adjustable that can do 16.5 volts (with 15 minute shots, so you have to be there to keep doing that. It drops one volt after the first 15 minutes, and then stays at that--15.5 in this case, so unplug and start again at 16.5)
So after two of those--30 minutes at 16.5, the darned SG has hardly moved up at all still 1.265ish. I decided to give it time to cool down when SG will go up a bit with colder fluid, and I will leave the batt on float overnight at 13.8 and give it another kick or two tomorrow.
So what's with these 27s anyway???? There they were at 1.300 and you do ONE drop to 50% and it is like pulling teeth to even get back into the green, never mind 1.275 or above. I hate 27s !!!!!!
-------------
Background info--not needed unless you are bored :)
Eight years ago, I swore off 27s because of my difficulties getting them back to proper full as seen by hydrometer readings. No such problems with 6s or the Trojan 12v T-1275s I have been using since. They come right up. No fuss.
I just got these two 27DCs as a stop-gap for rounding out the battery bank now that my two T-1275s finally died, and I need two batts to go with my six-year old pair of 6s that are still going but for only another year most likely. (I need about a 400AH bank) Then next year I can start over with all new whatever.
