New Batteries

[Lnob]

Hi there
I just bought 2 new Interstate SRM24 batteries. When I first put them in the monitor read 12.5.
I charged overnight from 110V now reads 12.8. I recall when I first got the AS that after charging I could be at 13.4ish. When I called the place where I purchased them he says 12.8 is what it should read. Can somebody please explain. I'm confused.
I also store it where I was leaving it plugged into 110v. After searching here i now realize i shouldn't do that. Maybe that's why the other batteries died after a year?
Thank you in advance
Laura

[daveswenson]

Here's a chart of typical voltages for a flooded lead battery.

State of Charge 12 Volt battery Volts per Cell
100% 12.7 2.12
90% 12.5 2.08
80% 12.42 2.07
70% 12.32 2.05
60% 12.20 2.03
50% 12.06 2.01
40% 11.9 1.98
30% 11.75 1.96
20% 11.58 1.93
10% 11.31 1.89
0 10.5 1.75

As far as leaving it plugged in, if you have the Parallax charger that comes standard you are right. It is a one stage charger and will kill your batteries.

[lewster]

Originally Posted by daveswenson

Here's a chart of typical voltages for a flooded lead battery.

State of Charge 12 Volt battery Volts per Cell
100% 12.7 2.12
90% 12.5 2.08
80% 12.42 2.07
70% 12.32 2.05
60% 12.20 2.03
50% 12.06 2.01
40% 11.9 1.98
30% 11.75 1.96
20% 11.58 1.93
10% 11.31 1.89
0 10.5 1.75

As far as leaving it plugged in, if you have the Parallax charger that comes standard you are right. It is a one stage charger and will kill your batteries.

Your numbers are pretty low for most batteries that I have seen. Where did you get the information? Typically, 12.8-13.2 is considered 100% and 12.2 is 50% discharged.

[daveswenson]

Hi Lew,
I got those numbers here.

Deep Cycle Battery FAQ

I thought they sounded a little low. I was too lazy to search further.

[weirdstuff]

Lew, do you have, or can you post a similar chart of what you think these numbers are? This would be very helpful.

After having ours in indoor storage, unplugged for 1.5 weeks, the house batteries read 12.5, and the chassis battery was around 12.3.

(We're trying to figure out how long we can safely leave her alone in storage)

Thanks!

[graysailor]

Go with a 3 stage smart charger and most of your battery problems will solved.

[dznf0g]

Dave's chart is what I have seen for regular old fashioned Lead acid batteries (automotive and deep cycle) from many sources and my personal professional experience for decades. I've never seen a fully charged resting LA battery at 12.8 - 13.2 in a resting state. (after several hours minimum resting)

I have seen some minor variations in the scale, but I use 12.06 as my 50% level. Some say 12.1 is 50% and some say 12.0 is 50%.

[lewster]

Originally Posted by weirdstuff

Lew, do you have, or can you post a similar chart of what you think these numbers are? This would be very helpful.

After having ours in indoor storage, unplugged for 1.5 weeks, the house batteries read 12.5, and the chassis battery was around 12.3.

(We're trying to figure out how long we can safely leave her alone in storage)

Thanks!

AGMs in general and Lifelines in particular have higher voltages due to their much lower internal resistance. Here is a chart from the Lifeline owners manual:


State of Charge 2 Volt Battery 6 VoltBattery 12 VoltBattery
100% 2.16V or more 6.50V or more 12.8V or more
75% 2.08V 6.25V 12.5V
50% 2.03V 6.10V 12.2V
25% 1.98V 5.95V 11.9V
0% 1.93V or less 5.8V or less 11.6V or less

The most important take-away from this 12.8-13.2VDC is 100%, 12.2VDC is 50% and 11.6VDC is 0 % for Lifelines

I would use the 12.2 VDC as a bottom level for storage and would re-charge them when they hit that voltage.

[dznf0g]

Yup, I was aware that AGMs do generally have higher voltages than Lead acid.