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 fo...
Forum Discussion
There are several tables of resting voltage per SOC and the SG that goes with it. You want to know what is right for your own battery.
You can do that by running that 10 hour test to 50% and cross-check SGs with the rebound voltage and the AH count. After a few tests you get a "feel" for what is "matching".
SG values depend also on what the battery maker started with for the concentration of acid. They use a lower concentration for use in hotter climates and VV, so they pick a compromise for temperate and they don't all use the same compromise. 1.275 can be full but some use 1.300 as full. Some use lower than 1.275.
Also the type of battery by purpose means using a different level of acid concentration. A Deep Cycle battery will have higher and a battery used in long term UPS banks will have a lower concentration. Higher SGs mean the battery does not like to be on a float voltage for a long time like a UPS battery sees.
For your first go, IMO, run the battery down at its 20hr rate until SG is 1.200 and then stop. Wait to see what the voltage does. If it bounces back to 12.2 right away, you are not there yet, so start it up again and go to a lower SG and try again. You can't get it exact, and you don't need to just to find out if the battery is "good enough" Try not to overshoot by much. Spot check the SG more often near the end.
When you first put the 20 hr rate on the voltage will drop and then slowly go down after that. With 5 amps on a 100AH batt, expect to see about 12.3 right off, and then maybe 11.8 by the time SG gets to 1.200. Whatever, it varies. But if you see 12.1 right off, that is a bad sign that the battery is in poor shape. So stick around and see how fast it takes to get the rest of the way. That is called "collapsing under load" and you need a new battery.
You want to see voltage bounce back to maybe 12.0 or so from that 11.8 or whatever, then climb slowly towards 12.1 or 12.2 depending on battery spec for 50% it can take overnight to get all the way to 12.2 but you can tell if it is going to work out ok within an hour.
You have to decide how bad to let things go before replacing the battery. You can have one that is 85% as good as new, but it still gets you through the night. Why toss it? But you know it is getting near the end.
You don't get much warning when the end comes. It can be working last weekend and collapse next time out. You have to decide what to do when it is like that, but at least you will know if you are getting near that point.
You can do that by running that 10 hour test to 50% and cross-check SGs with the rebound voltage and the AH count. After a few tests you get a "feel" for what is "matching".
SG values depend also on what the battery maker started with for the concentration of acid. They use a lower concentration for use in hotter climates and VV, so they pick a compromise for temperate and they don't all use the same compromise. 1.275 can be full but some use 1.300 as full. Some use lower than 1.275.
Also the type of battery by purpose means using a different level of acid concentration. A Deep Cycle battery will have higher and a battery used in long term UPS banks will have a lower concentration. Higher SGs mean the battery does not like to be on a float voltage for a long time like a UPS battery sees.
For your first go, IMO, run the battery down at its 20hr rate until SG is 1.200 and then stop. Wait to see what the voltage does. If it bounces back to 12.2 right away, you are not there yet, so start it up again and go to a lower SG and try again. You can't get it exact, and you don't need to just to find out if the battery is "good enough" Try not to overshoot by much. Spot check the SG more often near the end.
When you first put the 20 hr rate on the voltage will drop and then slowly go down after that. With 5 amps on a 100AH batt, expect to see about 12.3 right off, and then maybe 11.8 by the time SG gets to 1.200. Whatever, it varies. But if you see 12.1 right off, that is a bad sign that the battery is in poor shape. So stick around and see how fast it takes to get the rest of the way. That is called "collapsing under load" and you need a new battery.
You want to see voltage bounce back to maybe 12.0 or so from that 11.8 or whatever, then climb slowly towards 12.1 or 12.2 depending on battery spec for 50% it can take overnight to get all the way to 12.2 but you can tell if it is going to work out ok within an hour.
You have to decide how bad to let things go before replacing the battery. You can have one that is 85% as good as new, but it still gets you through the night. Why toss it? But you know it is getting near the end.
You don't get much warning when the end comes. It can be working last weekend and collapse next time out. You have to decide what to do when it is like that, but at least you will know if you are getting near that point.
