Things have really changed in the space of voltage protection.

In the distant past we had the Sollatek AVS30 as well as those plug in socket TV and Fridge Guard devices - the advantage of the Sollatek AVS30 was that it had adjustable low and high voltage cutoff points via 2 potentiometers - some finnagling was needed to get/infer the exact voltages the device would cutoff at as the potentiometer adjustment was analog. Further the device was limited to about 4mm sq wire gauge and perhaps 30amps AC pass through so could not be used for too large loads or whole house unless one used it to drive a relay or contactor.

The big disadvantage of the Fridge Guards and TV Guards was the lack of user settable trip limits - the default 260-270v high voltage cutoff and ~180v low voltage cutoff was too coarse and would let destructive voltages pass - at the very least the electronics would run hotter than design and see shorter service life at high voltages.

Enter the relay and later servo stabs which would spit out fairly clean voltage on the output side for equipment to use given a suitable range of input voltages from the supply side. A lot of these also failed above 270v and then we now have the MCB like voltage and current protection devices with a LED display and digital settings menu so that the user can precisely set the voltage tolerance he would like to pass through to his equipment.

In my typical designs, I would place a digital voltage protection device on the input to a servo stab or inverter to prequalify the supply quality for the protected devices. The digital voltage protection devices also have over current protection built in which can be useful on the output of an inverter to prevent from user abuse, wiring errors, overloads and short circuits.

OP may refer to a picture of a digital voltage protection device below at an affordable price - purveyors on here sell it between 6k and 10k for a 63a rated unit I believe

GeorgeD1:


the plug-ins have their limit. if you really want peace of mind, go for standard avrs that you can see input
and output voltage clearly displayed. that way you'll be sure your electronic equipment is getting the
right voltage needed to function properly.

To be clear you do not routinely top up the 'acid' or electrolyte in a flooded battery unless there are severe issues/degradation and you are trying to salvage or restore the battery.

The required regular/routine maintenance is to top up any low cells with distilled water and ONLY distilled water .

Just to avoid any mishaps as the actual electrolyte can be purchased open market and most people cannot tell the difference between electrolyte and distilled water and when/where to use which.

nnadychuks:
hw much does it cost to top the acid, and is it something you can do on your own?

emyfine08:
you're id

It's in my signature WhatsApp/call

clearance sale. 8k each it's brand new

Any reliable solar inverter installer around Ebute Metta axis shd pls signify...

I'm an avid DIY renewable energy guy and presently interested in actively participating in inverter installations(theory don plenty thanks to this page). If you have any installation project in Abeokuta this year end, I dont mind tagging along for the experience. Thanks

nnadychuks:
hw much does it cost to top the acid, and is it something you can do on your own?

I bought a tds meter and started checking sachet water tds level and found one with a low tds level. I've been using them since for top up

Without raining on anyone's parade, those particular models - Tomzn branded - tend to be very failure prone - the ones with complex functions numbered from 1 to 13 or so.

Meanwhile the older gen ones with just 3 - 5 menu screens/functions were rock solid reliable.

Some people may have or have had a better experience with them than I did

Valto:
clearance sale. 8k each it's brand new

NiyiOmoIyunade:
Without raining on anyone's parade, those particular models - Tomzn branded - tend to be very failure prone - the ones with complex functions numbered from 1 to 13 or so.

Meanwhile the older gen ones with just 3 - 5 menu screens/functions were rock solid reliable.

Some people may have or have had a better experience with them than I did

i have been using the same in 3 different places for over 2yrs and non has failed so far

NiyiOmoIyunade:
Without raining on anyone's parade, those particular models - Tomzn branded - tend to be very failure prone - the ones with complex functions numbered from 1 to 13 or so.

Meanwhile the older gen ones with just 3 - 5 menu screens/functions were rock solid reliable.

Some people may have or have had a better experience with them than I did

Can u share pictures and specs of models that has worked for you, links will be highly appreciated...

If you got whatever you have two years ago then they were very likely not the version with several pages of functions up to 13 or 15 functions - AFAIK those ones became mainstream fairly recently.

The key distinguishing feature is that those ones with multiple functions have high and low voltage trip and RECOVERY points and notably a VOLTAGE CALIBRATION menu usually at function A13 - those units are wack as they often go off calibration and the LED display fails or becomes blurry.

I am being careful here not to ruin anyone's show as I do not know anything about the specific products you have used or are selling - just making a general advisory based on my own experience as I use these products for every single install.

Valto:
i have been using the same in 3 different places for over 2yrs and non has failed so far

Dear Boss,

In our private backchannel thread, this same matter has come up for discussion with other users sharing similar experiences

The ones marked pass are the ones I have found to go the distance. The more complex ones with multiple pages of functions including delay and recovery settings and notably a voltage calibration function easily go off kilter and become unreliable.

See pics below - first one is a pass - the others not so

saint2ace:


Can u share pictures and specs of models that has worked for you, links will be highly appreciated...

NiyiOmoIyunade:
Dear Boss,

In our private backchannel thread, this same matter has come up for discussion with other users sharing similar experiences

The ones marked pass are the ones I have found to go the distance. The more complex ones with multiple pages of functions including delay and recovery settings and notably a voltage calibration function easily go off kilter and become unreliable.

See pics below - first one is a pass - the others not so

Thanks My Oga for your response. While I might be knowledgeable about our back end discuss, folks here who have read your write up might not be so lucky, the question was aimed at enlightenment and also at providing information to those who might want to thread the path of purchasing the said item but do not possess the right information.

Once again thanks for the info and do have a great season.

Cheers

isangjohnson:
With all the rules duely observed, if lead acid battery can last for 5 to 6 years with lifecycle of about 500 to 800, then lifepo4 may get to 15 years under the same condition with lifecycle of about 2000 to 2500.
I'm waiting to see how many years my tubular will stay alive too. The highest power drawn from my battery is 30%. It's about a year now and I've never top water before.

From all the literature I have read about tubular and from over 5 years of personal experience with an average discharge of just 30%. TUBULAR (which are flooded acid batteries) does need constant top up at least once in 2 months. If yours hasn't been topped with water going into a year then something is wrong somehere and it is not good for the battery.

Not topping up your flooded acid battery like TUBULAR simply means you are charging it at a voltage that is lower than recommended for the battery chemistry. Tubular is designed to be charged at 14.4v per 12v battery or 28.8 for 24v etc (based on all the documentation I have read about them from Indian sources) 14.4 is the absorption voltage and it is best to maintain them at this voltage for at least an hour or 2 to ensure they are properly charged and reduce the risk of sulfation.

They are also expected to be "over charged" at least once a month in a process called equalization. This equalization charge helps to mix up the electrolytes to prevent concentration of acid at the buttom and it also helps to balance all the cells within a battery and bring them to parity. Ordinarily you want this equalization charge to happen at least once a month. Not all inverters support equalization though so you would need to ensure your inverter suports it.

Equalization voltage is about 15.5v per 12v cell or 31v for a 24v bank. Some chargers can do this for you automatically if you ordered program them. You might also want to get an hydrometer to check the gravity of each cell during equalization process.

I would suggest you review how your battery is being charged to ensure it lasts as long as you want it to.

nnadychuks:
hw much does it cost to top the acid, and is it something you can do on your own?

When I owned my tubular batteries, I settled to harvesting water from the AC and using that over buying "distilled" water from a source I can't verify. I did this after I saw some aldulterated distilled water sold at Games store (a major super market competitor to Shoprite) I reported the issue to them and they had to stop selling the product.

Put a container to the AC horse and you would have it filled up with distilled water in less than 30 minutes. Use a white cotton (I got a white pure cutten singlet for this) and filter the water to another container and you have a distilled water to last you a top up cycle. You can use AC at work if for this.

bigrovar:


From all the literature I have read about tubular and from over 5 years of personal experience with an average discharge of just 30%. TUBULAR (which are flooded acid batteries) does need constant top up at least once in 2 months. If yours hasn't been topped with water going into a year then something is wrong somehere and it is not good for the battery.

Not topping up your flooded acid battery like TUBULAR simply means you are charging it at a voltage that is lower than recommended for the battery chemistry. Tubular is designed to be charged at 14.4v per 12v battery or 28.8 for 24v etc (based on all the documentation I have read about them from Indian sources) 14.4 is the absorption voltage and it is best to maintain them at this voltage for at least an hour or 2 to ensure they are properly charged and reduce the risk of sulfation.

They are also expected to be "over charged" at least once a month in a process called equalization. This equalization charge helps to mix up the electrolytes to prevent concentration of acid at the buttom and it also helps to balance all the cells within a battery and bring them to parity. Ordinarily you want this equalization charge to happen at least once a month. Not all inverters support equalization though so you would need to ensure your inverter suports it.

Equalization voltage is about 15.5v per 12v cell or 31v for a 24v bank. Some chargers can do this for you automatically if you ordered program them. You might also want to get an hydrometer to check the gravity of each cell during equalization process.

I would suggest you review how your battery is being charged to ensure it lasts as long as you want it to.

Spot on, i was too lazy to type all this out.same comment came to my mind when i saw people only topping up 2x or 3x a year!!.

jonescosmos:


Appart from your Batteries being full or floating, You can't compare the efficiency of Independent CCs to Hybrid Inverters.
I had this same problem when my setup was 8x360w (4s2p Wiring) with 60A CC and 3KW Inverter on 4x220Ah FLD Batteries. The Banks never get full all day long and no matter what I switched on, I never got past 1.XXKW production from the PVs according to the display of the CC just like what you have posted here.

When I switched to 5KVA Hybrid with 100A MPPT Built-In Charging at 60A, same 4x220Ah FLDs, rearanged same PVs to 8s, The Inverter sucked almost 2.8KW from the same panels begining from around 10am till 3pm, Batteries gets fully charged before sun down while powering more loads alongside than the prior setup.

Conclusively, I nothiced that due to a broader intelligent programming of priorities on Hybrid Inverters, they tends to query for more power from the PVs than the Batteries. (Output Source Priority Setting: SUB) once you do this, S=Solar, U=Utility, B=Battery. So the SUB order means get every power you need from the Sun first, If Solar Energy is not sufficient or not available, Make it Up from Utility, If both Solar and Utility are not available, take power from the battery banks.

This is one hell of a function that Seperate CCs doesn't have. Because the Inverter sees only Battery Input as power source, it sucks from it, remember that the Battery Banks are closer to the Inverter than the PV and CC in terms of ampearage, the batteries are then always draining.

This whole Hybrid Inverter Intelligence in my own words is revolutionalised in my Deye Inverter which dumps all dependence on Grid/Battery and shifts to Solar inputs for Power, in turns, it sucks everything is can get from the solar before considering Grid or Battery.

In my humble opinion, dump the setup of CC, inverter, Battery and shift to a good Hybrid Inverter, i guarantee you won't regret it. Just make sure that yout setup is properly protected from the storms both from Grid and Solar.

What all due respect, I would like to correct some assumptions made in this post mostly for people seeing this so they don't take the wrong conclusion.

I can't speck to the performance of the seperate CC you were referring to since you didn't provide any information. CC are not all the same and just because something is called MPPT does not mean it works or has a good tracking algorithm.

We also don't know the specification of this CC but since most CC take 150v max VOC inputs configuring your panels in 4S (and I want to believe this are 24v nominal panels) already puts them out of range for most 150v CC (again we don't know the cc so it might be configured for 250v inputs or more)

In a nutshell, your poor yield experience is more due to system design or bad cc. It is definitely not resultant from using a seperate charge controller. In fact it is often recommended to use a seperate charge controller whenever you can (a good one that is) as they tend to have better MPPT tracking Algo than those that come with solar inverters (which we call hybrid inverters here)

The second thing I would like to address is the the SUB setting from your solar inverter where is defaults to Solar then Utility before battery.. is just physics. You would have the same functionality with the inverter even if your charge controller is external (from experience) SUB uses battery voltage to decide when to switch to grid. Battery voltage can give an indication if a battery is under load or charging and it uses certain battery voltage threshold to decide when to switch to the grid.

However some solar inverter like Axpert King use a process called double conversion to blend grid with solar thus allowing you to use the grid to augument your solar production (rather than using battery). They do this by converting the grid AC to high voltage DC and terminate this to a common busbar shared with their inbuilt solar controller output. The paralleled output from solar DC and converted Grid DC is then converter to AC to power the house.

Inverters like Axpert King and I think Deye also does this are those that do require you to use their built in charge controller to utilize the grid blending function.

It should be however said that Victron multiplus can also do grid blending when paired with an external Victron CC.

In conclusion it is actually better from a performance point of view to use an external charge controller as it makes the system modular and you can get a product that is dedicated to harvesting and charging.

If however you want to be able to use features like grid blending then you can get a solar inverter that supports it and use it's built in CC.

I have long since abandoned lead acid except for use in pro bono systems for elderly relatives and folks in the village or other very low load demand applications. I am loath to besmirch my hands with such chemistries or think about them too much these days

I agree with virtually all that you have said about flooded battery chemistry - you need a positively good charge to agitate/bubble/gas the electrolyte and let things mix up well.

The only mod I would make is that flooded batteries do better at 14.6v per 12v as the minimum for the absorb voltage target. Anything from 14.6v to 14.8v as a regular charge is good. Then the periodic equalization at or above 15v.

14.4v is better suited as a cap for AGM and Gel where you want to minimise gassing and stay within the recombination (ability to make gas generated during charging back into liquid) capabilities of your 'sealed and maintenance free' battery - since you are not ordinarily expected to top up water in AGM and Gel, the need to preserve the liquid electrolyte mix from factory overrides the need for a better charge at higher voltages.

This then is the delicate balancing act that the system designer must master for each battery he deploys - charge the battery at the highest possible voltage it can take and you get max capacity but a shorter service life, charge at lower voltages and you sacrifice some capacity but get longer service life. Finding the optimal point to stay at is the core skill to master as battery charge and discharge are inevitably destructive processes.

But I digress - anyone who is deep cycling his flooded batteries daily but has not topped up distilled water after 6 months is very likely charging at too low a voltage and slowly strangling/sulphating the battery to death.

bigrovar:


From all the literature I have read about tubular and from over 5 years of personal experience with an average discharge of just 30%. TUBULAR (which are flooded acid batteries) does need constant top up at least once in 2 months. If yours hasn't been topped with water going into a year then something is wrong somehere and it is not good for the battery.

Not topping up your flooded acid battery like TUBULAR simply means you are charging it at a voltage that is lower than recommended for the battery chemistry. Tubular is designed to be charged at 14.4v per 12v battery or 28.8 for 24v etc (based on all the documentation I have read about them from Indian sources) 14.4 is the absorption voltage and it is best to maintain them at this voltage for at least an hour or 2 to ensure they are properly charged and reduce the risk of sulfation.

They are also expected to be "over charged" at least once a month in a process called equalization. This equalization charge helps to mix up the electrolytes to prevent concentration of acid at the buttom and it also helps to balance all the cells within a battery and bring them to parity. Ordinarily you want this equalization charge to happen at least once a month. Not all inverters support equalization though so you would need to ensure your inverter suports it.

Equalization voltage is about 15.5v per 12v cell or 31v for a 24v bank. Some chargers can do this for you automatically if you ordered program them. You might also want to get an hydrometer to check the gravity of each cell during equalization process.

I would suggest you review how your battery is being charged to ensure it lasts as long as you want it to.

To add to this already long discourse.

One of the key determinants of ideal charge voltage is the battery electrolyte composition - higher concentrations of sulphuric acid will require higher charge voltages to charge effectively and will give more capacity but also the battery internals corrode and degrade faster with higher acid concentrations.

A flooded battery that can do well at 14.4v per 12v charge very likely has a relatively weaker concentration of acid in the electrolyte mix - this can be positively determined by taking SG readings with a temp compensated hydrometer and comparing to reference SG data from credible published sources. e.g Rolls, Trojan or US Battery.

I recall that @ BigRovar originally had concerns that his now retired flooded batteries had capacity less than spec or expected. The people who put the electrolyte in the battery likely used a relatively weaker mix either by accident or they chose to stay on the lower capacity with longer service life end of the curve - this is further corroborated if they recommended 14.4v absorb charge for their flooded battery as other manufacturers spec a much higher charge voltage.

NiyiOmoIyunade:
I have long since abandoned lead acid except for use in pro bono systems for elderly relatives and folks in the village or other very low load demand applications. I am loath to besmirch my hands with such chemistries or think about them too much these days

I agree with virtually all that you have said about flooded battery chemistry - you need a positively good charge to agitate/bubble/gas the electrolyte and let things mix up well.

The only mod I would make is that flooded batteries do better at 14.6v per 12v as the minimum for the absorb voltage target. Anything from 14.6v to 14.8v as a regular charge is good. Then the periodic equalization at or above 15v.

14.4v is better suited as a cap for AGM and Gel where you want to minimise gassing and stay within the recombination (ability to make gas generated during charging back into liquid) capabilities of your 'sealed and maintenance free' battery - since you are not ordinarily expected to top up water in AGM and Gel, the need to preserve the liquid electrolyte mix from factory overrides the need for a better charge at higher voltages.

This then is the delicate balancing act that the system designer must master for each battery he deploys - charge the battery at the highest possible voltage it can take and you get max capacity but a shorter service life, charge at lower voltages and you sacrifice some capacity but get longer service life. Finding the optimal point to stay at is the core skill to master as battery charge and discharge are inevitably destructive processes.

But I digress - anyone who is cycling his flooded batteries daily but has not topped up distilled water after 6 months is very likely charging at too low a voltage and slowly strangling/sulphating the battery to death.

AC condensate run off water is not distilled water but is probably as close as one can get with bonus points for knowing exactly what you are putting in your battery.

If one can get the AC condensate runoff water to be filtered clean of impurities then one is on to a good thing indeed.

bigrovar:


When I owned my tubular batteries, I settled to harvesting water from the AC and using that over buying "distilled" water from a source I can't verify. I did this after I saw some aldulterated distilled water sold at Games store (a major super market competitor to Shoprite) I reported the issue to them and they had to stop selling the product.

Put a container to the AC horse and you would have it filled up with distilled water in less than 30 minutes. Use a white cotton (I got a white pure cutten singlet for this) and filter the water to another container and you have a distilled water to last you a top up cycle. You can use AC at work if for this.

Boss man!

Thank you very much and much love and respect always.

Merry christmas to you and yours!!!

saint2ace:



Thanks My Oga for your response. While I might be knowledgeable about our back end discuss, folks here who have read your write up might not be so lucky, the question was aimed at enlightenment and also at providing information to those who might want to thread the path of purchasing the said item but do not possess the right information.

Once again thanks for the info and do have a great season.

Cheers

NiyiOmoIyunade:
I have long since abandoned lead acid except for use in pro bono systems for elderly relatives and folks in the village or other very low load demand applications. I am loath to besmirch my hands with such chemistries or think about them too much these days

I agree with virtually all that you have said about flooded battery chemistry - you need a positively good charge to agitate/bubble/gas the electrolyte and let things mix up well.

The only mod I would make is that flooded batteries do better at 14.6v per 12v as the minimum for the absorb voltage target. Anything from 14.6v to 14.8v as a regular charge is good. Then the periodic equalization at or above 15v.

14.4v is better suited as a cap for AGM and Gel where you want to minimise gassing and stay within the recombination (ability to make gas generated during charging back into liquid) capabilities of your 'sealed and maintenance free' battery - since you are not ordinarily expected to top up water in AGM and Gel, the need to preserve the liquid electrolyte mix from factory overrides the need for a better charge at higher voltages.

This then is the delicate balancing act that the system designer must master for each battery he deploys - charge the battery at the highest possible voltage it can take and you get max capacity but a shorter service life, charge at lower voltages and you sacrifice some capacity but get longer service life. Finding the optimal point to stay at is the core skill to master as battery charge and discharge are inevitably destructive processes.

But I digress - anyone who is deep cycling his flooded batteries daily but has not topped up distilled water after 6 months is very likely charging at too low a voltage and slowly strangling/sulphating the battery to death.

Please what if the person's daily consumption is ridiculously low thus no major daily drain on the battery cycle? Should the person still be topping up water that hasn't gone down at all?

My total battery capacity is 24V 440AH and I only draw about 1,500W on a day of intense use. I'm still on the grid and NEPA is behaving well now so I don't have reason to really on the batteries fully yet.

Topup is in response to low water levels in a battery cell.

If none of your cells are short of water after a careful visual inspection then there is no need to topup.

Beware that any flotation based battery water level indicators are indeed working correctly and not deceiving you hence I said after a careful visual inspection of the water levels per cell.

Once the above checks out and you satisfied yourself that you are charging at a proper voltage for your battery then you are good to go.

vta2008:


Please what if the person's daily consumption is ridiculously low thus no major daily drain on the battery cycle? Should the person still be topping up water that hasn't gone down at all?

My total battery capacity is 24V 440AH and I only draw about 1,500W on a day of intense use. I'm still on the grid and NEPA is behaving well now so I don't have reason to really on the batteries fully yet.

merry christmas to all men (and women) of goodwill in the house!

NiyiOmoIyunade:
Topup is in response to low water levels in a battery cell.

If none of your cells are short of water after a careful visual inspection then there is no need to topup.

Beware that any flotation based battery water level indicators are indeed working correctly and not deceiving you hence I said after a careful visual inspection of the water levels per cell.

Once the above checks out and you satisfied yourself that you are charging at a proper voltage for your battery then you are good to go.

Thanks a lot sir. My body don calm down small. This whole lead acid battery drama can be one kain
Merry Xmas

NiyiOmoIyunade:
Topup is in response to low water levels in a battery cell.

If none of your cells are short of water after a careful visual inspection then there is no need to topup.

Beware that any flotation based battery water level indicators are indeed working correctly and not deceiving you hence I said after a careful visual inspection of the water levels per cell.

Once the above checks out and you satisfied yourself that you are charging at a proper voltage for your battery then you are good to go.

I agree with everything you said above nothing to add but to double click on the statement concerning the concentration of acid on the tubular lead acid sold here in Nigeria.

These batteries are usually shipped dry to lower the shipping cost. Shipping them mixed with electrolyte automatically makes them Hazmat and shipping cost goes through the roof. The quality of the electrolyte they are filled with here in Nigeria then bring to question and it is why many tubular batteries are plaqued with severe case of voltage sag once a small load is placed on them. I personally don't recommend tubular. They are not worth the stress and are very difficult to use properly.

Merry Christmas Oga GeorgeD1.

All the best to you and yours.

GeorgeD1:
merry christmas to all men (and women) of goodwill in the house!

bigrovar:


I agree with everything you said above nothing to add but to double click on the statement concerning the concentration of acid on the tubular lead acid sold here in Nigeria.

These batteries are usually shipped dry to lower the shipping cost. Shipping them mixed with electrolyte automatically makes them Hazmat and shipping cost goes through the roof. The quality of the electrolyte they are filled with here in Nigeria then bring to question and it is why many tubular batteries are plaqued with severe case of voltage sag once a small load is placed on them. I personally don't recommend tubular. They are not worth the stress and are very difficult to use properly.

Abeg what would you call severe case of voltage lag? My battery only lags when I turn on my air fryer. The inverter load rises to like 30% and voltage drops from 24.9V to 23.2V. Once I'm done, it rises back to say 24.8V

A very merry xmas to your all.

To the veterans and DIYers and installers in the house. I am beginning my solar journey and would welcome una input. and advise.

I have been pushing this forward for some time but have decided to start somewhere. And reading some experiences, I believe the very first thing to do on the solar journey if one is disposed to will be to
1. audit your electrical wiring connection and safety installations (is it properly grounded. is your earth system still working. is your DB properly installed with functional safety breakers (if its something you will consider). This is to ensure nothing fries or damages the solar connection.
2. decide what kind of solar setup you want to have based on your present situation/circumstance or vision and then work upwards as the case maybe.
3. ask questions about the quality of the brands in the market (solar panel, inverter (hybrid), safety gears, cables, battery type)
4. It is advisable not to not go for the cheapest product. In the same note, the most expensive isn't automatically the best value for you. (your circumstance may mean you are fine with a 5 year service as against a 15 year service).
5. research and consult widely with people and learn from their errors or mistakes
6. And do not compromise on safety.

So for no 1. - What kind of tests should I be asking an electrician to carry out to ensure the wiring is proper and their are no "leakages"?

So for no 2. - I have decided my circumstances will require hybrid inverter because I intend to be doing it small small. I have heard Deye, Growatt, Felicity, Mpower, Prag ... etc Please make una help me recommend top three from your experience

So for no 6. - Can one have a configuration that allows for an isolator. Most of the setup I see dont seem to have isolators any where.

Thanks all as your respond and read.

tipsy242:
Any reliable solar inverter installer around Ebute Metta axis shd pls signify...

Is Surulere close enough?

MERRY CHRISTMAS EVERYONE

vta2008:


Abeg what would you call severe case of voltage lag? My battery only lags when I turn on my air fryer. The inverter load rises to like 30% and voltage drops from 24.9V to 23.2V. Once I'm done, it rises back to say 24.8V

.
Your illustration on the performance of your battery once load is applied is called voltage sag. Those ones with severe voltage sag may not easily return to the previous voltage when the placed load is released, though still depends on the running time of the said load.