Standby & Cyclic=Float & Absorption?

[solarstuff]

My 4-battery bank of 100Ah AGM batteries list a constant voltage chage for 'standby use' is 13.6-13.8V, and cyclic use is 14.5-14.9V.

Am I right in assuing my 'standby use' is my float & 'cyclic' is absorption?

I want to set custom values for my Renogy Li MPPT to stop it from trying to equalize my AGM's, but I don't want to blow anything up

Putting the numbers together, please tell me if I am correct in assuming I can set equalisation voltage to float voltage (13.6-13.8V) via the front panel and float and absorption voltages to 14.5-14.9V?

Thanks, all!

 

[snoobler]

Mostly.

If you're using your batteries in a telco to provide backup power, that's standby operation, i.e., long periods sitting at 100% waiting to be used. In that case, both absorp and float are 13.6-13.8V. This also typically enables higher charge currents (0.3C) due to the lower peak voltage, which is desirable in a standby operation... get 'em charged back up to a high SoC quickly and then top them off slowly.

Cyclic is daily or frequent cycling. In this case, you charge to 14.5-14.9V absorption at a lower rate, typically 0.1-0.2C and then float at 13.6-13.8V.

Set equalization to the absorption voltage.

If I were you:

Float: 13.7
Absorp: 14.5
Equalization: 14.9

Let it equalize once a month for an hour.

 

[solarstuff]

Mostly.

If you're using your batteries in a telco to provide backup power, that's standby operation, i.e., long periods sitting at 100% waiting to be used. In that case, both absorp and float are 13.6-13.8V. This also typically enables higher charge currents (0.3C) due to the lower peak voltage, which is desirable in a standby operation... get 'em charged back up to a high SoC quickly and then top them off slowly.

Cyclic is daily or frequent cycling. In this case, you charge to 14.5-14.9V absorption at a lower rate, typically 0.1-0.2C and then float at 13.6-13.8V.

Set equalization to the absorption voltage.

If I were you:

Float: 13.7
Absorp: 14.5
Equalization: 14.9

Let it equalize once a month for an hour.

Thanks for the confirmation .. but I thought AGM's and equalizing didn't get along? I'm confused on that one.

 

[snoobler]

Thanks for the confirmation .. but I thought AGM's and equalizing didn't get along? I'm confused on that one.

They don't based on what you do when you equalize FLA (16.2V and boil off electrolyte), but they do if you stay in the voltage limits.

Higher absorption voltages are more stressful.
Lower absorption voltages may encourage light sulfation and may not get battery to true 100%.

Why:

Operate at 14.5V absorption to reduce stress on your battery and then press the reset button once a month by running to 14.9V. Grab the last bit of capacity and undo what tiny amount of sulfation may have occurred.

You'll find some charge controllers are set similarly for sealed batteries.

https://www.epsolarpv.com/upload/file/2103/Tracer-BN-Manual-EN-V2.0.pdf

 

[solarstuff]

Mostly.

If you're using your batteries in a telco to provide backup power, that's standby operation, i.e., long periods sitting at 100% waiting to be used. In that case, both absorp and float are 13.6-13.8V. This also typically enables higher charge currents (0.3C) due to the lower peak voltage, which is desirable in a standby operation... get 'em charged back up to a high SoC quickly and then top them off slowly.

Cyclic is daily or frequent cycling. In this case, you charge to 14.5-14.9V absorption at a lower rate, typically 0.1-0.2C and then float at 13.6-13.8V.

Set equalization to the absorption voltage.

If I were you:

Float: 13.7
Absorp: 14.5
Equalization: 14.9

Let it equalize once a month for an hour.

Thanks for the answers but even more for taking the time to explain, and send links.

One more small q: Renogy only inputs by 2 volt inplements, am I better to program my 2 MPPT's to one volt above or below your recommended values of:

Float: 13.7
Absorp: 14.5
Equalization: 14.9

Thanks again.

 

[snoobler]

If I understand what you're saying, return them. They are garbage.

 

[solarstuff]

Thanks for the answers but even more for taking the time to explain, and send links.

One more small q: Renogy only inputs by 2 volt inplements, am I better to program my 2 MPPT's to one volt above or below your recommended values of:

Float: 13.7
Absorp: 14.5
Equalization: 14.9

Thanks again.

If I understand what you're saying, return them. They are garbage.

Heh. Sadly, had them over a year and can't return them. Will Prowse videos gave them the thumbs up for the price range and hopefully I won't have to replace.

For now, I'm opting one volt down from your recommendations That's still within the battery's universal power brand specs--and I'd rather be safe than sorry (again

 

[snoobler]

Are you absolutely certain there's not a way to adjust them in a more precise way? I can't articulate how horrific this concept is. The idea that a charge controller can only be adjusted in 2V increments is beyond absurd.

If you go 1V below the recommended voltages, you will dramatically shorten the life of the batteries. Period.

I'm not kidding or being dramatic. Either you're wrong about only being able to only adjust in 2V increments, or those are the worst charge controllers ever conceived of by Man.

If it only allows 0.2V increments, then that sucks, but it's much closer to sane. 0.1V below those values is fine. 1V below will be catastrophic in terms of reduced life.

 

[solarstuff]

They don't based on what you do when you equalize FLA (16.2V and boil off electrolyte), but they do if you stay in the voltage limits.

Higher absorption voltages are more stressful.
Lower absorption voltages may encourage light sulfation and may not get battery to true 100%.

Why:

Operate at 14.5V absorption to reduce stress on your battery and then press the reset button once a month by running to 14.9V. Grab the last bit of capacity and undo what tiny amount of sulfation may have occurred.

You'll find some charge controllers are set similarly for sealed batteries.

https://www.epsolarpv.com/upload/file/2103/Tracer-BN-Manual-EN-V2.0.pdf

View attachment 44082

I'm using these batteries in a 24v series-parallel bank now.

Can I just double the numbers for the 12v use case? EDIT: never mind, I read the attachment that says I Can (sorry, blindness setting in)

 

[Substrate]

All it means is this: Are you drawing down from the batteries daily? If so, because solar insolation is limited, set both "absorb" and "float" to the same higher value of 14.4 to 14.5v to get the most in as you can before mother nature turns off the sunlight. Do not use the "EQ" voltage if you see it.

AGM's actually need 8-12 hours of float AFTER absorb is over, and you typically can't do that with solar daily. It's something that just simply can't be rushed - so a work-around for daily cyclic is in order to minimize the problem of not getting back to 100% charge daily.

If you are NOT discharging them daily, and they get solar exposure over multiple days without any discharge, then use the conservative value of 14.5v "absorb", and 13.6v float. This is because the batteries have been given adequate time over the course of a couple of days to get recharged and can just float until you decide to use them again.

The first situation, daily cyclic solar and dropping to float too soon daily, is a major reason that agm's get undercharged and walk themselves down in capacity over time due to hard sulfation.

SCC manufacturers take the conservative route by default, and don't address daily-cyclic solar users needs - leaving that to the end-user to educate themselves about the workaround, and manually make the proper choice themselves. OR rely on the following:

In fact, the "EQ" function is NOT A TRUE EQ. Every 30 days or so, it will apply the "EQ" voltage for about 2 hours. This is a compromise attempt to get the typical undercharged agm healthy. The assumption is that this slightly elevated voltage to a badly undercharged battery - for a very limited time like 2 hours - won't be harmful.

So identify your usage. Pick your strategy. If you are daily cyclic, set absorb and float the same. OR just go with the defaults where every 30 days, a FAKE EQ of a slightly elevated voltage will be applied for a very limited time automatically every 30 days.

 

[solarstuff]

All it means is this: Are you drawing down from the batteries daily? If so, because solar insolation is limited, set both "absorb" and "float" to the same higher value of 14.4 to 14.5v to get the most in as you can before mother nature turns off the sunlight. Do not use the "EQ" voltage if you see it.

AGM's actually need 8-12 hours of float AFTER absorb is over, and you typically can't do that with solar daily. It's something that just simply can't be rushed - so a work-around for daily cyclic is in order to minimize the problem of not getting back to 100% charge daily.

If you are NOT discharging them daily, and they get solar exposure over multiple days without any discharge, then use the conservative value of 14.5v "absorb", and 13.6v float. This is because the batteries have been given adequate time over the course of a couple of days to get recharged and can just float until you decide to use them again.

The first situation, daily cyclic and dropping to float too soon daily, is a major reason that agm's get undercharged and walk themselves down in capacity over time due to hard sulfation.

SCC manufacturers take the conservative route by default, and don't address daily-cyclic solar users needs - leaving that to the end-user to educate themselves about the workaround, and manually make the proper choice themselves.

In fact, the "EQ" function is NOT A TRUE EQ. Every 30 days or so, it will apply the "EQ" voltage for about 2 hours. This is a compromise attempt to get the typical undercharged agm healthy. The assumption is that this slightly elevated voltage to a badly undercharged battery - for a very limited time like 2 hours won't be harmful.

So identify your usage. Pick your strategy. If you are daily cyclic, set absorb and float the same. OR just go with the defaults where every 30 days, a FAKE EQ of a slightly elevated voltage will be applied for a very limited time automatically every 30 days.

Thanks for an amazing description!