48v flooded led acid battery lower max charge voltage good or bad?

Fabian · February 2017

I see on the internet where most manufacturers recommend a max charge voltage or absorption voltage of 57.6v-58.8v for flooded led acid battery. I have a nova 48v 3000watt 110vac pure sinewave inverter that allows a max of 57.1v input voltage. Because of this i cannot set my charge controller to 57.6v-58.8v according to what most manufacturers said you should charge a 48v flooded led acid battery to.

If I set the charge controller to cut off at 57v or 57.1v which it will go in the absorption stage at that voltage and then afterwards it will cut down to a float charge voltage of around 54v will I still be able to fully charge the flooded led acid battery? Is there any pros and cons with charging the 48v battery bank at a lower voltage setting than the recommended charge voltage which is 57.6v to 58.8v?

Is charging at the lower voltage setting increase my charging time to fully charge the battery?
is charging at a slightly lower voltage better for the battery?

Estragon · February 2017

Does your charge controller have a way to end absorb based on current measured at a shunt?

Using a lower absorb means it will take longer to charge. Assuming charge source is solar, you may run out of sun before absorb is really done. The lower absorb voltage and potentially too short time may limit bubbling/gassing at the end of absorb. This may save water, but means electrolyte can stratify and lead to problems.

This makes it even more important to check SG regularly as using resting voltage alone may not alert you to an undercharging problem.

Another potential issue is temperature. If the bank is much below room temp it will need higher charging voltage. If warmer, lower voltage is needed. Is your controller temp compensated?

Vic · February 2017

Hi Fabian,

At room temperature (about 25 C), 57 or 57.1 Volts is just barely above Gassing voltage for many/most Flooded batteries.

For Flooded batteries even at 25 - 27 C, it will NOT be possible to fully-charge most of them, even in an infinitely long charge session. If the batteries were always HOT, you might be able to fully charge them at 57-ish volts, but who wants to keep the batteries hot?

Seems that you might want to find an inverter that can still work when the battery voltage is in the 64-ish volt range. The maximum voltage need to fully charge and EQ Flooded batteries will depend upon the exact battery model, and the coldest temperature at which an EQ would be needed.

All, just my opinions, Vic

Fabian · February 2017

Reason why I want the higher voltage is base upon this research i saw online.

"The correct setting of the charge voltage limit is critical and ranges from 2.30V to 2.45V per cell. Setting the voltage threshold is a compromise and battery experts refer to this as “dancing on the head of a needle.” On one hand, the battery wants to be fully charged to get maximum capacity and avoid sulfation on the negative plate; on the other hand, over-saturation by not switching to float charge causes grid corrosion on the positive plate. This also leads to gassing and water-loss"

Seeing that the voltage limit on my 48v inverter being 57.1v i can only set my charge controller to 57.1V or a lower max charge voltage which works out to be 2.30V to 2.37V/cell voltage max which according to the research online 2.30v to 2.37v per cell for a max charge voltage on flooded led acid battery would come with these disadvantages/limitations:

Slow charge time; capacity readings may be inconsistent and declining with each cycle. Sulfation may occur without equalizing charge.

With these limitations that is why I would need to be able to can charge the 48v battery bank to 58.8v to avoid the limitations stated above and at the same time the inverter still connected and turn on and not going into OVP.

If adjusting my input voltage max for my inverter is not possible. If I charge the battery bank to 57.1v on a daily basis but every once per week or once per 2 week or once per month i disconnect or turn off the inverter and give the battery a equalize charge up to 60v or a higher voltage charge of 58.8v until it is fully charge before connecting back the inverter would this reverse or prevent the limitations stated above?

If it would what full charge routine at 58.8v or equalize cycle at 60V or higher would be best to use, once per week? once per 2 week or once per month?

Vic · February 2017

Fabian,

OK, so you do not want to change the inverter, got it.

Exactly just what you will need to do to keep your battery happy, will depend mostly upon exactly what battery you are dealing with.

Keeping batteries happy, seems to always be, at least a bit experimental.

If the Flooded batteries are relatively tall, Stratification could be a relatively large issue when trying to "charge" with such a low voltage. The SG of the electrolyte has a large effect on the required Vabs, Veq and Vflt.

Temperature of the battery has a large effect on the charge voltages needed ... many variables.

Looks like you own the inverter and batteries. Good thing that the batteries are Flooded, making measuring the actual SG easy. SG readings are the Gold Standard for KNOWING the SOC of a battery. Stratification will still make it difficult to manage battery charge parameters.

As batteries age, changes to charge parameters usually need to be made, usually this includes increasing charge and EQ voltages somewhat.

That is all that I have on this. Good Luck! Vic

mvas · February 2017

What if you added a Quick Disconnect Switch?
http://www.jegs.com/i/Moroso/710/74103/10002/-1?ref=paid&brand=&channel=Shopping&gclid=CKziy-7IkNICFZK6wAod_QoFrQ
http://http//www.jegs.com/i/JEGS-Performance-Products/555/10320/10002/-1
Instead of Equalizing once per week, what if you changed your Bulk Voltage up to 59.6 Volts = ( 14.9 volts x 4 ) @ 70° F ?
And then perform a proper Bulk Charge and Absorb Charge to see if SG returns to a normal value?
If, and only if, that does not work, then perform an Equalize Charge.
You do not want to do an Equalize without first doing a proper Bulk & Absorb.
An Equalize Charge should be done only when SG will not return to normal levels or a variance > 30 points between cells.

You need bubbling to prevent stratification of the electrolyte.

Equalize ( ONLY after a proper Bulk Charge and Absorb Charge is complete ) ...
1) Once every 30 days OR
2) SG in any cell is below the minimum value OR
3) Difference in SG values between the cells exceeds 30 points

STOP the equalize charge when the SG value stops rising between two consecutive SG readings

Fabian · February 2017

If I use the same low voltage of 57.1v for the cutoff voltage for the charge controller and the battery starts to charge going through the normal stages: bulk, absorb and then reaches a point where the float charge current is now charging at 1% of the battery bank amps capacity, would this suggest that the battery bank is completely charge? And in that case would the SG of the cells always be in the full charge stage/normal level whenever the charging stops and the battery comes to the rest voltage?

Would this prevent electrolyte from stratifying once the battery SG reading is showing normal level for all the cells when you check them at the rest voltage?
Would you still need to equalize the battery bank even thou the battery bank has got a full charge at least once in less than one week? or in less than 2 weeks?
Would you still get maximum capacity and avoid sulfation on the negative plate once you manage to get full charge for the battery at this low voltage setting?
Would you manage to get full charge for the battery at the same low voltage below room temp once you have high amps kicking into the battery most of the time from an oversize solar array?

Therefore if you oversize on you solar array so that you can get full charge and get the SG readings for the cells in the normal level most of the times then these limitations would not occur charging at the low voltage setting all the time
"Slow charge time; capacity readings may be inconsistent and declining with each cycle. Sulfation may occur without equalizing charge"

Am I correct?

Estragon · February 2017

You should check specific gravity on each cell to be sure you have charged completely. If SG is correct for your batteries (eg. 1.27), and all cells have close readings, the bank is properly charged.

What kind of inverter do you have? 57.1v sounds low for an unadjustable HBCO value. Maybe this is a default adjustable value?

mvas · February 2017

Fabian said:

If I use the same low voltage of 57.1v for the cutoff voltage for the charge controller and the battery starts to charge going through the normal stages: bulk, absorb and then reaches a point where the float charge current is now charging at 1% of the battery bank amps capacity, would this suggest that the battery bank is completely charge? And in that case would the SG of the cells always be in the full charge stage/normal level whenever the charging stops and the battery comes to the rest voltage?

If your Float Voltage ( 13.5v x 4 = 54 v ) is pushing 1% of C20 amps into your batteries then no your battery bank was not fully charged at the end of the Absorb Stage. My float charge usually pushes less than 0.1% C20 amps into the battery bank. Are you seeing a good amount of bubbling near the end of the Absorb Charge at 57.1 volts? Without bubbles, I do not understand how you are mixing the electrolyte or how you are getting to 100% SOC. How many hours does your 57.1 volt Absorb Charge require before the Amps drop below 1%?

Fabian said:

Would you still need to equalize the battery bank even thou the battery bank has got a full charge at least once in less than one week? or in less than 2 weeks?

Equalize ( ONLY after a Bulk Charge and full Absorb Charge is complete ) ...
1) Once every 30 days OR
2) SG in any cell is below the minimum value OR
3) Difference in SG values between the cells exceeds 30 points
STOP the equalize charge when the SG value stops rising between two consecutive SG readings

I think you you are asking ...
"... Is it OK to use a weekly Equalize Charge to finish charging the battery bank to 100% SOC because of an incomplete daily Absorb Charge? ..."

If your Absorb Charge never reaches 100% SOC, then your only choice is to start a weekly Equalize.
But a weekly FULL Equalize Charge is very hard on a battery bank.
If you must do a weekly Equalize then manually STOP the Equalize as soon as two consecutive SG reading are the same.
Two consecutive SG readings of the same value means the batteries are at 100% SOC, so why continue?
I would not do a full equalize every week, your brain is way smarter than any so-called smart charger.

Fabian said:

Would you manage to get full charge for the battery at the same low voltage below room temp once you have high amps kicking into the battery most of the time from an oversize solar array?

Therefore if you oversize on you solar array so that you can get full charge and get the SG readings for the cells in the normal level most of the times then these limitations would not occur charging at the low voltage setting all the time

Are you really getting the same SG readings twice in-a-row, at one hour intervals when the Absorb is set to 57.1 Volts?
Only you can answer that question.

Regarding: "High amps during bulk" and "oversized array" ...
Pushing more amps during Bulk Mode, within reasonable limits, will recharge your battery bank to 57.1 volts more quickly, but more amps will not ever get your battery bank to a higher SOC at 57.1 volts. Your Bulk Mode will only get your battery bank to 70% - 80% SOC max because your 57.1 voltage cut-off is so low. Now, you will need a longer than normal Absorb Mode to get your battery Bank up to 100% SOC because you are switching from Bulk Mode (higher amps) in to Absorb Mode (lower amps) too soon. Roughly - for each hour that your low 57.1 Volt limit prematurely stops the the Bulk Mode too early, adds 2 hours to your Absorb Mode !!! There are only so many hours of sunlight per day.

So you need to balance your daily depth of discharge vs your daily hours of sunlight vs the need to do a "partial equalize" weekly.

Aguarancher · February 2017

From reading your post on another forum, you are running a nova 48v 3000watt 110vac pure sine wave inverter. From the specs I see your inverter has over voltage protection “Protection: Overload, Short Circuit, Reverse Polarity (Fuse), O.T, Over/Under Input Voltage, Fan Failure & Remote Control Standard on all models.”.

I would take care of your batteries and let the inverter take care of itself. This is only my opinion.

https://novaelectric.com/product/48v-pure-sine-wave-output-inverter-3000-watt/

mvas · February 2017

Aguarancher said:

From reading your post on another forum, you are running a nova 48v 3000watt 110vac pure sine wave inverter. From the specs I see your inverter has over voltage protection “Protection: Overload, Short Circuit, Reverse Polarity (Fuse), O.T, Over/Under Input Voltage, Fan Failure & Remote Control Standard on all models.”.

I would take care of your batteries and let the inverter take care of itself. This is only my opinion.

https://novaelectric.com/product/48v-pure-sine-wave-output-inverter-3000-watt/

So, what happens to the Inverter when the Charge Controller outputs more than 57.1 Volts <edit>, an Over Input Voltage condition?
Will the Inverter shutdown or ?

Aguarancher · February 2017

"So, what happens to the Inverter when the Charge Controller outputs more than 51.7 Volts, an Over Input Voltage condition?
Will the Inverter shutdown or ?"

the specs say 56 v input and i read in one of his posts 57v. my guess is for the small amount of over voltage it clips the OV. if it were his cc i would be more concerned. i didn't read the op manual, figured he could do that. the pdf is on the website..ok i just read the pdf..lol.. over voltage cuts in @ 61.2VDC

mvas · February 2017

I mis-typed as 51.7 Volts, I should have typed 57.1 Volts.
Yes, it is his Charge Controller that needs to output more than 57.1 volts to the battery bank but the Inverter is limiting max voltage
I do not understand ... what do you mean by: "The inverter clips the Over Input Voltage" ?
Are you saying the inverter will continue to work with an Input Voltage greater that exceeds the Maximum Input Voltage rating?

Aguarancher · February 2017

the inverter will operate if the input voltage is under 61.2 vdc, over that i assume it shuts down. he should be able to set his cc to not exceed that voltage and all should be happy (inverter and batteries) .. read the pdf in the above link for the info.

Fabian · February 2017

is not the charge controller is at fault. I can adjust the output voltage for the charge controller way pass the 57.1v. The issue is with the inverter not been able to operate pass 57.1v. the specs on it says 42-60v input, but once you reach 57.1v it goes into red and starts beep showing OVP and then you don't have any output coming out of it. Why does the manual and the specs sheet and also the labelling on it says input up to 60v but yet still it won't pass 57.1v? I am confused. I really need to be able to can charge the battery up to 58.8v without the OVP kicks in. Is there a way to disable the OVP instead of adjusting it?

Aguarancher · February 2017

if it was me, i'd go to the horses mouth..and contact: howard@theallpower.com
that is the link for tech questions

Vic · February 2017

Hi Fabian,

YES, it really appears that this inverter is not really appropriate for Flooded Lead Acid (FLA) batteries.

Those of us here know nothing whatsoever about your batteries, Charge Controller (CC), your goals for this system, etc.

In general, top tier (best quality, with many features and settings - expensive) 48 V Inverter/Chargers will accommodate battery voltages up to about 66 V, or so, and still function well, and meet almost all, if not all of their specs.

Because we do not know very much at all about your batteries, it is quite possible that an Inverter that can function up to 60 V may not be able to charge or EQ a FLA battery, even at room temperature (about 25 - 27C). It could be possible that your Flooded batteries have a low SG electrolyte, which can reduce the required voltage for Absorb and EQ.

And, once again, for most FLA batteries 57-ish volts will not be fully-charged, even with days and days of trying. If the FLAs are at room temperature, most FLA batteries 57 or 57.1 volts is insufficient for Absorb, let alone EQing.

IMO you should look very carefully at the detailed specifications for the exact batteries that you are using, note the range of voltages for Absorb and EQ that are recommended. Then apply the recommended Temperature Compensation value to the highest of these voltages, for the coldest temperatures that you honestly estimate that the batteries will encounter. This will help guide you to selecting an appropriate inverter/charger for your system.

Have not looked at the specs on the inverter, but good quality inverter/chargers include a Battery Temperature Sensor (BTS), or offer it as an option. The CC needs to either share a single BTS, or have one of its own. It is essential for good battery health, that every charge source be able to use battery temperature data from a BTS.

Hope that you can return the inverter for full-credit of the amount that you paid for it, and find one that meets the needs of your system. It seems that the specifications for your inverter are incorrect, which would seem to make if not useable for the batteries that you are using.

As a general statement, a CC that has a battery voltage limit of about 60 volts, is not up to the task of charging most FLA batteries.

Just my opinions. Vic

Fabian · February 2017

If I disable the ovp I don't think the inverter will fry. The Labelling and the specs shows that it can
Handle 42-60v input. I am just wondering if is the manufacturer limit it to 57.1v. The voltage during charging won't pass 58.8v. The charge controller will limit it from going any further. So is there a way to disable the ovp instead of adjusting it?

Aguarancher · February 2017

we don't have the answers you seek~

contact: howard@theallpower.com
that is the link for tech questions for your inverter

Fabian · February 2017

If i place a Battery Desulfator Circuit on the battery bank will that prevent sulfation from occuring charging the battery bank to only 57.1v at all times and not performing any equalizing?

Or suppose I place the battery desulfator circuiut on the battery bank and I equalize every once a month will this method give me back my full capacity ready every once a month and prevent long term sulfation from occuring on the battery bank due to the fact the the desulfator circuit is always connected and doing this routine will allow me to get the full life span out my battery bank?

Estragon · February 2017

The only way to know is for you to check specific gravity regularly. Hydrometers aren't very expensive and are a very basic tool for FLA battery maintenance. Your bank may or may not need EQ, and even if it does, doing one properly involves checking SG during the process.

mcgivor · February 2017

Read what everyone is directing to you towards, forget the desulfator, you need to focus on the battery requiments, not the inverter limitations, turn off the inverter if need be, don't sacrifice the battery for the sake of the inverter.

48v flooded led acid battery lower max charge voltage good or bad?

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