leaving a charged battery hooked up for long periods

I was wondering if it damages a battery to leave it hooked up to the PWM charger all the time. I see the battery SOC at 13.8 when I get home from work and after the sun goes down it will have dropped to 13.1 by the time I get up in the morning and I am worried that is not good for my lead acid batteries , should I disconnect the batteries once charged and just hook them up once a month or am I worried about nothing.
I dont use the system vary much its just there for when the power goes out for a few hours so I wont have to fuel up the genny.
Thanks
Eddie

Float charge shouldn’t damage a lead acid battery.
Here is some info:

That sounds like a normal drop in voltage once there is no more charge or float going into the battery. 13.8v is a float charge when it’s full, 13.1v is a normal resting voltage after it sits for a while with no float charge (at night) Your PWM isn’t drawing power because most CCs have a blocking diode built in to prevent the battery from back feeding your solar panel at night.

Most multi stage FLA battery chargers offer a timed period of bulk charge voltage to stir up the electrolyte to avoid stratification. It is also good policy to periodically discharge the bank and equalize charge it to re-balance the cells. You must water before & after this "equalize charge" procedure.
(Equalizing is inappropriate for sealed or AGM batteries as that process causes gassing and removes water.)

I guess the question I need to ask does it damage the battery's to be float charged every day or should I disconnect the batterys from PWM CC once they are charged and leave them at a resting voltage for a month or so before charging them again . It looks like from the first reply from Dnnap that it is ok to just bring them up to 13.8 volt every day and dont worry about it. Is there any body out there that disagrees ?

Your battery will be fine staying connected. To disconnect them means over time (less then a week in some cases) they will slowly self-discharge which will lead to sulfation. As for the voltage drop 13.8 and 13.1 are both surface charges, not deep charges and the fact your battery only hits 13.1 overnight means your battery is in awesome condition. Just check the water once a month and refill with distilled water only and you're set.

SCClockDr is correct in everything posted also excpet the red stuff. Read LifeLine batteries instruction pamphlet that comes with every single one of their AGM batteries the part titled "Is your battery not performing like it should?" or something like that about their AGM batteries and equalizing. To sum it up Equalize at 15.3v for 8 hours.

That'd be the first AGM battery I've come across where the manufacturer says ok to equalise. It must have pretty impressive recombination ability to do that. Most batteries will start audibly blowing gas past the relief with extended absorption charging let alone equalisation.

This thread made me look up the manual for my battery. It says nothing about equalizing. However, there are some pretty good informational charts and such in the document, so I'm linking it here. The manual is specific to my WindyNation 100Ah AGM RA-12, so while specific to that, the general info can be adapted for any AGM. It talks about 6 month storage.

Okay gnubie guess it's time for me to tell my story about why I know so much about batteries. lol. Short version, 5 seasons of RV solar installs at a place that refurbishes and sells used batteries (I hate the practice personally).

Year 1: I had to test and process all the used batteries while installing new battery banks- at that time no AGM batteries were to be equalized for reselling, they're all cores, "You can't equalize AGM batteries!"

Year 2: Back in the same position, while unboxing some LifeLines to install I read the 4 page sheet, held it up and practically screamed "Can't EQ AGMs? I call b*******! LifeLine themselves say you can!"

Since then: We've equalized all sealed lead acids with 'variable valve tech' and AGMs which are just sealed lead acid that don't gas with only a problem on 1 variable valve that started spitting out. Again, Full River AGMs are the only ones that the 'tech' said can't be equalized. That 'tech' said to completely drain the AGM and re-charge it 3 times to get rid of any sulfation which makes zero sense. As for LifeLine batteries they pride themselves for being in police cars and ambulances so they think they're 'top of the line' and recommend equalizing.

The valve is actually a little slot on the sides of the stem the rubbery cell cap fits over. Each cell has one and starts discharging gas once pressure is around 2psi above atmosphere. Excessive absorption charging will cause a typical AGM to start blowing gas out. You can actually hear the pfft pfft if you listen carefully. They all recombine to some degree to cope with it but only so much gas production per interval can be handled. The higher the charging voltage the more gas.

I've seen quite a few AGMs dried out by overcharging over the years so it is quite surprising to me to see a company recommending equalisation charging on them. A battery built with that sort of charging in mind would be able to cope with it, but a typical off the shelf wouldn't appreciated it one bit.

None the less, thanks for the tip about LifeLine batteries. You learn something every day, hopefully.

gnubie said:

I've seen quite a few AGMs dried out by overcharging over the years so it is quite surprising to me to see a company recommending equalisation charging on them.

Click to expand...

I saw another forum try to figure out when AGM is 100%, and it landed at 12.7 or 12.8 Do you think 12.8 is significantly more than 12.7 and potentially risky?

Overcharging being when the battery is held at elevated voltages for one reason or another for too long. I'm not talking about the resting voltage.

To confirm @gnubie 's crazy claim:

> There are two types of Valve Regulated Lead Acid (VRLA) Batteries: the Gel Cell and the Absorbed Glass Mat (AGM).
(source)

Killing batteries is a skill I've really honed in on. Can you tell which of these batteries died from undercharging, and which from overcharging?

Kcp said:

Your battery will be fine staying connected. To disconnect them means over time (less then a week in some cases) they will slowly self-discharge which will lead to sulfation. As for the voltage drop 13.8 and 13.1 are both surface charges, not deep charges and the fact your battery only hits 13.1 overnight means your battery is in awesome condition. Just check the water once a month and refill with distilled water only and you're set.

SCClockDr is correct in everything posted also excpet the red stuff. Read LifeLine batteries instruction pamphlet that comes with every single one of their AGM batteries the part titled "Is your battery not performing like it should?" or something like that about their AGM batteries and equalizing. To sum it up Equalize at 15.3v for 8 hours.

Click to expand...

thanks for your help