I am about to forward the below to East Penn Batteries to ask for comments and "?approval?".
I would appreciate any input aforehand.
Proposed Solar Charging Regimen
Let me start by thanking you and your team for all the knowledge you have shared with me over the last couple of years. You all are appreciated. I do not claim to know everything but I will begin with what I think I know.
Charging in a SOLAR environment is challenging at best.
For the sake of battery health and longevity the goal is to routinely charge a battery or battery bank to close to 100%SOC at least every third day and avoid excessive over charging.
The many variables such as the amount of solar panels, the capacity of the charge controller, the size of the battery bank and the daytime and nighttime loading of the battery bank vary widely from one system to the next. Some battery banks may start the day at 50%SOC and others at 85%SOC. Each would require different considerations.
The traditional method is a bulk charge voltage until an ABSORB voltage is reached and maintain that voltage for a specified time. Because the solar delivery of voltage and currents fluctuate greatly over the course of a day (or week), one specific ABSORB time is an inadequate solution. That time will either be to short to obtain 100%SOC or lead to extended overcharging.
One commonly used solution is to used is to use ENDAMPS to terminate the ABSORB cycle. It is unclear to me that this as accurate and reproducable as many believe. Consider a partly cloudy day with a sudden burst of sunshine. There is also considerable disagreement as to what value ENDAMPS should be.
It is also a benefit to assure adequate ABSORB time in the 85%-100% SOC range for cell equalization. This reduces the need for EQUALIZATION charges (battery longevity).
Given the above, I would like to propose the following: (variables in bold are up to debate)
FLOAT CURRENT VERIFICATION OF THE ABSORB CYCLE
Initially, the traditional BULK/ABSORB cycle would terminate at ENDAMPS = 2.15 amps (GL10 215AH example)
FLOAT would begin and run for a stabilization time FLOATtime = 5minutes
If the measured FLOAT CURRENT < +10% TARGET FLOAT CURRENT 500ma (GC10=450ma) then continue FLOAT. Set a FLAG for sucessfull Full Charge.
If the measured FLOAT CURRENT > +10% TARGET FLOAT CURRENT 500ma (GC10=450ma) then store LAST FLOAT CURRENT and return to ABSORB for an additional 25minutes (fixed time NOT ENDAMPS)..
Return to FLOAT for stabilization and recheck FLOAT CURRENT and compare to LAST FLOAT CURRENT. If there is progress, loop back to ABSORB for another 25 minute cycle (fixed time NOT ENDAMPS). .
More than 6 loop backs would suggest a decrease in ENDAMPS value or an aging battery bank and a re-assessment of the TARGET FLOAT CURRENT .
If the FLAG for successful Full Charge has not been reset in 3 days a warning that a manual utility charge is in order.
I do not believe that my suggestion is at odds with anything in your publication "Monoblock Flooded System Installation and Operation Manual". It should also work with SLA and GEL systems (different parameters).
I plan to log long term trends in FLOAT CURRENT. My understanding is 3x-6x original specifications is the start of concerns.
I also plan to monitor Parallel Battery Bank Strings for individual float current and discharge current contribution.
I would appreciate any input you may have. Obviously I would love to receive a "wow what a great idea" response, but I am aware that some issues may need addressing.
Best Regards, Barry Fields
Ending amps can be fine BUT you can't do that every single day with lead acid batteries!
LA batteries need a timed absorb cycle every now and then. At least like, once per week.
I don't really know what the ending amps should be ? I think that the battery manufacturer should show that number. But they still need to be absorbed. If you do that, I don't think you need to equalize much, if at all. Absorb and EQ are both to help reduce sulfation.
With an amp-hour system and LA, the system should really be able to let you know if the batteries have lost capacity. I know that my LA batteries which happen to be pretty flat these days could be flagged with using the WB. Jr.
As for Float time, during the day when production is good, there is no reason why the solar (or whatever source) can't keep the batteries SOC% from being drawn down by keeping the float voltage just above the batteries resting voltage. Then there should be more energy left there for the night time.
boB
boB
Quote from: boB on May 26, 2024, 05:06:58 PMLA batteries need a timed absorb cycle every now and then. At least like, once per week.
That is what this regimen does. The time for absorb is adjusted according to results (FLOAT current). Some days longer, some days shorter.
{added text to above} loop backs are fixed time NOT ENDAMPS
Quote from: Barry Fields on May 25, 2024, 06:51:54 PMI am about to forward the below to East Penn Batteries to ask for comments and "?approval?".
I would appreciate any input aforehand.
Last chance for comments before I email this proposal.
Thanks Barry
SENT 5/29
Go for it !
Quote from: boB on May 28, 2024, 02:39:05 PMGo for it !
If things go as well as I expect, might MidNIte apply for a "process patent" that could be licensable to other solar companies? Just a thought.
Quote from: Barry Fields on May 30, 2024, 09:40:00 AMQuote from: boB on May 28, 2024, 02:39:05 PMGo for it !
If things go as well as I expect, might MidNIte apply for a "process patent" that could be licensable to other solar companies? Just a thought.
Patents are expensive and time consuming so probably not.
Build one up and sell them ? Besides, whatever you have said on this forum might be considered as published now ?
boB
Quote from: boB on May 30, 2024, 12:38:59 PMBesides, whatever you have said on this forum might be considered as published now ?
I talked to Hillary Clinton. You apply for the Patent and I will start deleting posts and emails. ;D
Quote from: Barry Fields on May 30, 2024, 04:11:45 PMQuote from: boB on May 30, 2024, 12:38:59 PMBesides, whatever you have said on this forum might be considered as published now ?
I talked to Hillary Clinton. You apply for the Patent and I will start deleting posts and emails. ;D
I LOVE it Barry !
OH ! And better contact the Japanese ambassador !
Does anyone have access to IEEE450?
Rolls battery does not believe that float current is a valid indicator of SOC. Deka's (East Penn) responses indicate that they are tacit believers.
Deka prior responses in red.
(1) Assuming a reasonable absorb time, once given a float voltage of 2.35 vpc, the float current should eventually stabilize @ approx. 450ma (for a very healthy battery). SOC=100% TRUE?
True
(4) In a parallel battery bank, the bank with reduced AH capacity would achieve 100%SOC (with reduced capacity). ????
Correct
I feel confident that float current is an accurate way of determining SOC.
For a detailed read
https://www.vertiv.com/48dfa5/globalassets/documents/battcon-static-assets/2010/state-of-charge-specific-gravity-versus-battery-charging-current.pdf
If this proposal is not a Better Mouse trap, I would love to hear detailed comments explaining perceived problems with it.
I look forward to a discussion.
Quote from: boB on May 28, 2024, 02:39:05 PMGo for it !
You would think that out of 1948 members, someone, anyone, would have something negative to say or at least a question on this Float current controlled Absorb time proposal.
Maybe I have not explained it well?
For me , I have moved on to LiFePO4 lithium chemistry batteries, this topic on float for lead acid really doesn't have much interest any longer.
That is why I don't have an opinion one way or the other.
With the cost of lithium batteries continuing to go down, that could be one reason why you don't get many comments.
Larry
Quote from: ClassicCrazy on August 17, 2024, 09:40:34 PMFor me , I have moved on to LiFePO4 lithium chemistry batteries, this topic on float for lead acid really doesn't have much interest any longer.
That is why I don't have an opinion one way or the other.
I appreciate your personal view. I prefer lead acid for the following reasons:
Wider voltage ranges (for a variety of advantages)
Cost and re-cycle-ability.
They do not catch fire.
I am sure that there are many here that have lead acid chemistries. Mid-Nite controllers support those chemistries. Shouldn't Mid-Nite do the best it can in that support?
Quote from: Barry Fields on August 18, 2024, 08:35:59 PMQuote from: ClassicCrazy on August 17, 2024, 09:40:34 PMFor me , I have moved on to LiFePO4 lithium chemistry batteries, this topic on float for lead acid really doesn't have much interest any longer.
That is why I don't have an opinion one way or the other.
I appreciate your personal view. I prefer lead acid for the following reasons:
Wider voltage ranges (for a variety of advantages)
Cost and re-cycle-ability.
They do not catch fire.
I am sure that there are many here that have lead acid chemistries. Mid-Nite controllers support those chemistries. Shouldn't Mid-Nite do the best it can in that support?
you forgot another benefit of lead acid - they will charge in freezing weather .
That is why I got my gel batteries years ago ( lead crystal chemistry)
One winter it got down to -40 F and those batteries kept me powered up . They were struggling to recharge at that temperature but luckily it warmed up a bit in a day or two and they started working better again. In hindsight I should have made an insulated box around them at the very least but they are big cells and spread quite a bit of floor space in the shed.
They still seem to perform great .
I always tried to take no more than 20% out of them for longest life.
I think these days there are balancers for lead acid batteries that will also give them a better lifespan.
I am not so sure about the cost benefits these days - I just bought a 48v 280 ah lithium for $2700 and that included shipping and an active cell balancer .
There is a lot more usable energy than equivalent lead acid since you can take them down to 20 or 30% soc no problem without the voltage sagging like lead acid would.
But yes if you can find a better way to charge lead acid that is a benefit to everyone.
Larry
Just curious, how well does waste-not PWM work with LiFePo4? (close volt tolerance)
Quote from: Barry Fields on August 18, 2024, 10:07:08 PMJust curious, how well does waste-not PWM work with LiFePo4? (close volt tolerance)
I did try the waste not with the lithium using the hawkes bay controller but it hadn't been implemented properly yet in the firmware and I haven't tried it again .
There isn't much power to recover during the absorb stage since the lithium will take in 100% of the available pv in my system - instead of only a small part of it like with lead acid. That is why the lithium battery charges so much faster. Plus there is the 98 or 99% efficiency during charging. I think the diversion function may be a better option if someone wants to use pwm control.
I would want to be able to divert the pv before it gets to the controller to a direct dc load. I am not sure if the Aux diversion could do this and still let the controller supply loads on the system. It seems like it should be able to do this though.
Larry