AGM battery type setting

[chriscam2]

I'm totally new to this but very excited to learn. I have been searching all over and just find conflicting information. That probably because I am so new and I am not even searching the right thing. I got 2 Weize 12V 100AH Deep Cycle AGM SLA VRLA Batteries and I am going to hook them up to a Renogy Rover 40 Amp 12V/24V DC Input MPPT Solar Charge Controller. I am reading the manual and not sure if I should set the battery type as gel, sealed, or flood. I'm am thinking sealed is the correct type. But have read gel and also read sealed. Since I'm so new to this I want to make sure before I hook it up I don't cook my new batteries or do any damage.

What also confusing is the battery manual lists information about charging in v/cells. How many cells are this AGM battery. I didn't think they had cells?

 

[mikefitz]

I'm am thinking sealed is the correct type. But have read gel and also read sealed.

With AGM you dont usually need or use an equalization stage. The GEL default setting has no equalization so would be suitable. However the boost volts at 14.2 may be a little low as 14.4 to 15 volts is recommended for your battery, The sealed default setting is 14.4 and the flooded 14.6, these may be more suitable voltages, but have the disadvantage of the equalization mode.
Its possible to use the 'user mode' to set up your own settings.

I suggest you use the GEL settings, and if possible with the user mode, alter the boost voltage to 14.6 or 14.7 volts. Most AGM perform better at higher voltages.

also confusing is the battery manual lists information about charging in v/cells

You 12v AGM batteries are made up from 6 cells in series, typically a full cell it would read just over 2.1 volts. When charging, the cells are charged up to a voltage of around 2.40 volts.

Mike

 

[Substrate]

Cool - got yourself a neat little learner-bank.

There are SIX, 2v cells wired in series to produce the nominal 12v.

What you have is an AGM battery. It is not a gel. Even though it is "sealed" one can be fooled by that "sealed" setting if the voltages aren't right.

Regarding what to set your Renogy to, GO BY WHAT THE VOLTAGE settings are, not any "canned" settings unless they actually match what you need.

AGM's of the "conventional" type, which yours is, want to see at LEAST 14.4 for the CV or so called absorb setting. Like all agm's, they tout themselves as "deep cycle". Which is a misnomer really for the "conventional" types. All that means is that yes, you can deep cycle them, but you will pay for that in cycle life. The general rule of thumb is to not exceed 50% capacity each cycle. Less leads to more cycles.

AGM's are notoriusly UNDER-charged, especially so in a solar installation where charge levels are not constant like they are with a dedicated AC charger, we want to put in as much as we can quickly without going beyond they rated input current limits.

Thus it is better to set your SCC to a slightly higher value, like 14.7 to 14.8v. Ideally, even if your SCC has mandatory temperature-compensation built in, an \at the battery\ temperature compensation probe attached to a terminal of the battery itself is even better.

Here's the thing you should know. AGM's are undercharged by not getting that last 1-percent of charge in. It takes at least 12-16 hours at a float charge of 13.6v to do so to actually finish the charge, before what would be considered long-term float.

If you can, take advantage of the AGM's ability to charge with a rate as high as 0.25 to 0.3C. That means you could theoretically over-panel them by using an array to supply 25-30A of current.

What this means on a practical level is that if you are doing a weekend-warrior kind of thing, vs a dedicated install, because agm's are usually under-charged, plan on devoting a whole day of no-load and just letting them sit there in float, because you can't rush this vital last 1-percent of charge.

There are other ways to accomplish this, but this should be enough knowledge to get your feet off the ground, and not prematurely kill the agm with solar.

 

[Substrate]

Heh, see this is the problem, and how agm's get killed with canned settings. Gels are too low. Flooded is initially ok, but the EQ charge kills agm's that aren't designed for it.

Simple: For solar, where one is most likely to UNDERcharge on a daily basis, we need to get that CV/absorb up higher 14.6-14.8v to get in as much as we can as fast as we can.

And a higher setting for float - 13.6v Because we don't have time to go any lower and get that last 1-percent charge. If you don't get that last 1% charged, your 100ah agm quickly \walks down with sulfation\ into a 75ah, then a 50ah and so forth. But at that point, it sure charges up quickly! (sarcasm).

So pick settings that are close to these two values.

In a more advanced setting, where we are cycling, the preferred solar method is even simpler:

BULK=ABSORB=FLOAT

Which simply means set \everything\ for 14.6-14.8v, including float.

Why - because of that annoying aspect of the sun turning off the power every night. We run out of time to get agm's properly charged daily.

It really can be that simple, but is frequently over-complicated.

Take advantage of the AGM to charge at the 0.25C rate and over-panel if your budget allows. It's a race against time in a cyclic setup.

 

[chriscam2]

Wow thank you for the very educational response! I am going to take some time to review this information and re the mppt and battery manual again. I might sound like the best route is to use the user mode and program my own values for the different charging modes. Thanks again. I'm so excited to learn and get into this. I'm in not rush. Half the parts are still in the mail.

 

[Substrate]

I really am so sorry, because stepping into the world of agm, especially via solar, can produce a bad case of TMI or too-much-info immediately.

It's a rite-of passage. And then one day you discover "just set EVERYTHING for 14.7v", (with temperature compensation, at the terminals is best) and the clouds disappear.

This is under the assumption that you are actually using the battery 2-3 times a week at least. Cyclic.
If you go longer than that without use, it is considered standby, and then a float of 13.6v would be fine.

The moral if nothing else is simply do not UNDER charge your agm's. It takes time to get that last 1 percent charged, which is vital for longevity.

 

[Roberto2]

Boost=Absorb=Float=Equilise

Hi from Sunny South Africa

I found with 700watt panels that now during Winter, my 360Ah Bank is struggling to keep up with our use.

Have 2x Controllers (one pmw and one mppt) running the show.

Decided to try advice to set the mppt to 14.8volts(Boost=Absorb=Float=Equillise).

I must say that within 3days of no drain off the Bank, the resting voltage of the Bank measured in the morning, reads 13.27volts.

Built a 10 Amp charger and plan to use it during night when solar goes into hibernation mode, charging for 10hrs, pushing 100Amps back and then at 8AM, let the Solar take over.

Do you guys think this will keep my Bank @ 100% SC ?

 

[pollenface]

Boost definitely doesn't = float

For AGM, set your Boost/Bulk/Absorb to 14.4 and if you're able to set the duration... 1hr if above 12.7, 2hrs if between 12.2 and 12.6, 4hrs if between 11.9 and 12.2, 6hrs if below 11.9

 

[Substrate]

One has to take their application into account when using agm. Is it daily-cyclic, or standby (which can mean more than 2 days of non-discharge)?

If it is daily-cyclic, then the generic boost=absorb=float applies. That is more simply, the CV and FLOAT are set the same value to help ensure you get the maximum charge in before the sun sets. This avoids the walk-down in capacity that occurs when you don't get that last 1% charge in.

If you *aren't* daily-cyclic, then the standard routines in most SCC's can be used since you have much more time to charge.

SCC's take the conservative route assuming the user is not daily-cyclic with agm's.