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Absorption stage

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CoachMcG

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Is it a big deal if i shut down my generator (stop charging ) during the absorption stage of the charging cycle?

I have a Samlex 2224 inverter charger and it automatically sets the absorption time of the cycle at 10times the length of the Bulk cycle. In other words, if it charges for 1 hour during Bulk stage, it will charge for 10 hours in absorption before going to float.

I Run 4x 12V sealed AGM rated at 82.5Ah in series/parralel.

It's a new setup so i'm still learning and very cautious. I don't let them go below 25V (approx 80%) before charging. I'm currently charging at 20A. Manufacturer recommends up to 25A. I'm thinking of going to 25 in order to speed up the Bulk stage and in return lowering the amount of time in the absorption stage.

Once in the absorption stage, the Voltage stabilizes (28.77) and the current gradually diminishes to 0Amps if i understand my manual correctly. That being said, it's been sitting at around 0.3 to 0.6A for the past hour and a half. I started charging around midnight and it,s now 09:50 (almost 10 hours). I checked throughout the night and it's been sitting at 28.77V for a long time.

So back to the original question... is it bad for my system if i shutt down the generator (solar panels not yet part of the system... coming soon) before reaching the float stage?

Thanks!
 
So that's about 330Ah total? 300mA on that sort of capacity battery says you are fully charged and have been for some time. Depending on who you believe, 1650mA absorption charge current should have you have fully charged with voltage seen on the battery posts being at your charger's target. Check with your battery's manufacturer to see if they specify a particular end current otherwise assume 0.5% of the battery's amp hours.
 
Assuming, 165Ah of 24V battery.

Charging should be at 16.5-33A optimally for a typical AGM.

At absorption voltage, and 16.5A, your battery is approximately 80% charged. If you charge at HIGHER current, you will hit absorption SOONER and will be at a lower state of charge, thus INCREASING your absorption time because absorption is starting at 25A instead of 20A. HOWEVER, your TOTAL charge time is reduced because of less time spent in bulk.

FLA/AGM batteries NEED to be run to 100% to maximize life and capacity. Running your batter from 100% to 80% daily is much less damaging than running it from 80% to 60% even though it's the same 20% total use. 80% is a safe level to charge and store for brief periods, BUT if you're cycling them, they need to go to 100%.

If your goal is to save generator time, I wouldn't make that choice at the expense of battery life. If the manufacturer doesn't specify, your batteries are near 100% SoC at absorption voltage and 5A. Additional input gives very little yield.

10 hours forced absorption is absurd. Most batteries want 3-4 hours of absorption as a max limit.

If I were you:
  1. Charge @25A to absorption
  2. Continue absorption until current drops to 5A
  3. Terminate charge
If the 25A current is for a SINGLE battery, then you could charge at 50A since you're running batteries in parallel.

Why I'm giving these numbers:

Most battery manufacturers recommend:
Charge lead acid at 10% of C (Ah rating) - sometimes as high as 20% for AGM
Absorption cut-off current of 1-3% C
 
gnubie said:
So that's about 330Ah total? 300mA on that sort of capacity battery says you are fully charged and have been for some time. Depending on who you believe, 1650mA absorption charge current should have you have fully charged with voltage seen on the battery posts being at your charger's target. Check with your battery's manufacturer to see if they specify a particular end current otherwise assume 0.5% of the battery's amp hours.
Click to expand...
165 Ah total since 2x82.5 are in series and connected in parralel to another 2x82.5 in series.

Still have lots to learn and appreciate everyone's input!

Thanks
 
snoobler said:
Assuming, 165Ah of 24V battery.

Charging should be at 16.5-33A optimally for a typical AGM.

At absorption voltage, and 16.5A, your battery is approximately 80% charged. If you charge at HIGHER current, you will hit absorption SOONER and will be at a lower state of charge, thus INCREASING your absorption time because absorption is starting at 25A instead of 20A. HOWEVER, your TOTAL charge time is reduced because of less time spent in bulk.

FLA/AGM batteries NEED to be run to 100% to maximize life and capacity. Running your batter from 100% to 80% daily is much less damaging than running it from 80% to 60% even though it's the same 20% total use. 80% is a safe level to charge and store for brief periods, BUT if you're cycling them, they need to go to 100%.

If your goal is to save generator time, I wouldn't make that choice at the expense of battery life. If the manufacturer doesn't specify, your batteries are near 100% SoC at absorption voltage and 5A. Additional input gives very little yield.

10 hours forced absorption is absurd. Most batteries want 3-4 hours of absorption as a max limit.

If I were you:
  1. Charge @25A to absorption
  2. Continue absorption until current drops to 5A
  3. Terminate charge
If the 25A current is for a SINGLE battery, then you could charge at 50A since you're running batteries in parallel.

Why I'm giving these numbers:

Most battery manufacturers recommend:
Charge lead acid at 10% of C (Ah rating) - sometimes as high as 20% for AGM
Absorption cut-off current of 1-3% C
Click to expand...
Really interesting! Much appreciated!
 
TL;DR version:
  1. 10 hour absorption is monumentally stupid.
  2. your batteries are likely at or very near 100% SoC when absorption current has dropped to 5A, so I wouldn't hesitate to terminate charging at 5A and calling it good.
 
That's exactly the one (2224).

If you look at page 94 it explains that the absorption stage = Bulk stage x 10.

I was definitely in absorption stage. At least thats what the remote panel said;)
 
Yuck. I didn't bother reading about the adaptive option as I was searching for greater control. That process is inconsistent with their charge discussion in 1.4.3.2 a) where they say a 4-8 hr absorp may result in overcharging.

Can't help but think we're misinterpreting it.

They do bring up a good point about a battery under a load while charging that I neglected. If you find that you're typically using about 5A of load during charge, your cut-off should be 10A (5A cut off + 5A use).

The adaptive algorithm explicitly indicates it's for a battery without a load.

Almost any setting would be better than the adaptive algorithm (60 minutes absorp or 4A cut off by default).
 
There shouldn't be any load on the Batteries since a transfer switch isolates the battery bank when the generator runs.

I noticed the manual you linked is a bit different than the one i received with my 2224. Your link refers to Firmware 0.78 for the Inverter/charger and 0.28 for the RC. My owner's manual is for version 0.70 for my EVO and 0.20 for the Remote. Firmware version of my system is 0.77 and 0.24... looks like i need to update...

If it's any help... my batteries are FIAMM FLX300.
 
Good.

We discussed those batteries in another thread.

Either you need to update, or you need to use your manual to select the proper settings.

Searching your posts indicates you have a 3kW generator? Are you just charging the battery with the genny, or are you powering other things at the same time. 3kW of genny to recharge at a 700W rate is pretty inefficient.
 
LOL... glad I'm consistent:

diysolarforum.com

Charge rate and capacity for FIAMM FLX 300 AGM batteries

I just installed my SAMLEX EVO 2224 at my cabin. I have 4*12v batteries. I believed they were 75Ah but the sheet attached says 82.5. They are setup in a series/parallel configuration so i guess my system would be 165Ah. At one point i was told that i should charge at no more than 20Amps. I...
diysolarforum.com diysolarforum.com

"5A termination" :)
 
Consistent indeed! Lol

The Generator, for the most part, would all go to the battery except if the fridge motor kicks in (80-100W) for approx 7mins.
 
It may not be practical, but getting a smaller generator on the order of 1000-1200W would likely be significantly more efficient than a 3kW generator. They tend to be most efficient at max load. Your fuel burn could be 30-50% less with a smaller generator.
 
Where are you getting the 700W from? forgive me... i'm a NOOB:giggle:. Even though my FIRMAN 3083 is 3000W it has Eco feature so it runs at lower idle unless a heavy load demands more power. Not sure if this makes a difference. I e-mailed Samlex for a firmware update. Your continuous input is greatly appreciated! I'll keep you posted!
 
Hmmm... From:


2.35V/Cell = 14.1V absorption
2.26V/cell = 13.56V float

They also indicate 0.1C charge rate in the typical charge curves chart I don't see anywhere that 50A charging is acceptable, but:


Appears to be the same battery under a different label.

P.16, less than 0.3C (.3 * 165 = 49.5A). They also recommend 2.45V±.05V, so 14.4-15.0V absorption and a 0.01C current termination (1.65A).

If that's truly the same battery, then I'd switch to a 50A charge rate and stick with the 5A (.03C) termination current. This should get you very nearly fully charged in the least amount of run time possible. Pulling 50*28.8V = 1.44kW from a 3kW genny will be a little more efficient.

It's worth logging time and current data every 15 minutes or so. Then you can estimate if you're fully charged or not, or how close you can get. If it takes an hour to drop from 5.5 to 5.0A, the 4Ah you got in that time frame is probably not worth the wait.

Probably also worth investing in solar soon - even 200W of panels could take over and provide (160W/28.8V) 5.5A of current at that voltage and easily restore up to 42Ah of capacity in a typical day. If you're only using 20% of your battery capacity overnight, then that might cover you.
 
snoobler said:
Hmmm... From:


2.35V/Cell = 14.1V absorption
2.26V/cell = 13.56V float

They also indicate 0.1C charge rate in the typical charge curves chart I don't see anywhere that 50A charging is acceptable, but:


Appears to be the same battery under a different label.

P.16, less than 0.3C (.3 * 165 = 49.5A). They also recommend 2.45V±.05V, so 14.4-15.0V absorption and a 0.01C current termination (1.65A).

If that's truly the same battery, then I'd switch to a 50A charge rate and stick with the 5A (.03C) termination current. This should get you very nearly fully charged in the least amount of run time possible. Pulling 50*28.8V = 1.44kW from a 3kW genny will be a little more efficient.

It's worth logging time and current data every 15 minutes or so. Then you can estimate if you're fully charged or not, or how close you can get. If it takes an hour to drop from 5.5 to 5.0A, the 4Ah you got in that time frame is probably not worth the wait.

Probably also worth investing in solar soon - even 200W of panels could take over and provide (160W/28.8V) 5.5A of current at that voltage and easily restore up to 42Ah of capacity in a typical day. If you're only using 20% of your battery capacity overnight, then that might cover you.
Click to expand...
Solar panels, 2x270Watt, are coming soon (proably within a month).

How do you get 4Ah from dropping 5.5 to 5 in an hour?
 
Decreasing Coulombic efficiency at higher states of charge, i.e., the 5.25Ah input (average of the start/end current) may only impart 4Ah of added charge. It's probably closer to 4.5Ah.
 
snoobler said:
Decreasing Coulombic efficiency at higher states of charge, i.e., the 5.25Ah input (average of the start/end current) may only impart 4Ah of added charge. It's probably closer to 4.5Ah.
Click to expand...
I'm way over my head!! Lol However, once explained... the math makes sense! thanks for your patience(y)
 
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