Battery monitor questions.

jackbombay · January 2016

Details on my solar system, I have a 200 AH "Universal battery" AGM in my sprinter DIY conversion van, I have never felt it has 100 useable AH of power.

Recently I camped in the van for a ~25* night, the heater ran for at most %50 of the night, and I had my laptop plugged in to a 12v outlet for an hour, that pulls 6 amps, the heater pulls 2, there were no other loads on the battery, but let's assume the heater ran 8 hours, that s16 ah plus 6 ah for the laptop, for 22 ah consumed, but battery voltage in the am was 12.5. The battery was fully charged at the start of the evening, I have a 30 amp Samlex charger int he van, that had been plugged in till charge rate dropped to 0.

The battery is in the heated portion of the van.

The battery is ~3.5 years old, I have a morning star ProStar30 PWM charge controller and 2 panels on the roof, a 145 watt and a 110 watt. I do leave the CC chargig th ebatteries when I am not using the van, according to Morning star that is fine, kind of irrelevant though as this battery has never seemed to deliver 100 useable AH as I'd hoped.

Ultimately, without a battery monitor there is no way to reallt tell what is going on, so I'm looking for advice on a battery monitor, this one should work well for me, I think, but I'd like confirmation on that, http://www.solar-electric.com/batteries-meters-accessories/metersmonitors/tr20mosy/bogart-engineering-tm-2030-rv-battery-monitor.html

In the instal instructions it says you can use a 500A shunt or a 100A shunt, BUT the 100A can be used to measure up to 300 amps. The 100 amp has the advantage of being able to measure down to a tenth of an amp, not really needed, but wouldn't hurt my feelings. I do sometimes charge the battery from the alternator, it is a 150 amp alternator, so theoretically under ideal charging conditions the Alternator could be putting out a bit more than 100 amps to the house battery, so I should be totally fine with the 100A shunt, yea? I guess I'm just scratching my head a bit that it isn't called a 300A shunt if it can deal with 300 amps...

This sin the 100A 100mv shunt that I'm looking at, http://www.solar-electric.com/mka-100-100.html

Ultimately having a more accurate means of determining charge state would be great, and I'd really like to know the true capacity of this battery, and I believe this battery monitor can do this, I'm fine with the cost, but if there is a better/cheaper/easier way to accomplish my goals I'm all ears.

Thanks for any info you guys may have!

jackbombay · January 2016

FWIW, this is the battery I have http://www.solar-electric.com/batteries-meters-accessories/batteries/unba/unba200amagm.html

Raj174 · January 2016

This is the one I have.
ECPC404 Ammeter and Voltmeter
Intelligent Digital EV Battery Pack Monitor
Amp-Hour Counting

Check it out here:
http://www.electriccarpartscompany.com/ECPC404-Ammeter-and-Voltmeter-br-Intelligent-Digital-EV-Battery-Pack-Monitor-br-Amp-Hour-Counting-br-USA-Stock_p_425.html

This is a video on how to set it up:

https://www.youtube.com/watch?v=TJcToZoVzbw

I think it's what you are looking for.

mike95490 · January 2016

Even the very smart battery totalizators (amps in vs amps out) only do a mediocre job at guessing at the remaining juice in the battery. Just using a simple voltmeter & amp meter can get you close as you develop a "feel" for the readings, A battery under load or being charged will not give you accurate voltage SOC readings, the battery needs to be idle for several hours to let the electrolyte settle and then you can use Volts & temperature to estimate the state of charge.
Even using a $300 charge meter, you will still find ways to black yourself out.

vtmaps · January 2016

You seem to be more concerned with capacity than SOC. A battery can have 100% SOC but still have low capacity. One of the many possible causes of that is chronic deficit charging, another is aging (either cycle aging or chronological aging). There are many ways to test your battery... you could check impedance or you can do a capacity test.

Why do you think you have reduced capacity? I'm not saying you don't have reduced capacity, but a voltage of 12.5 in the morning after discharging 22 ah overnight is pretty good. (I assume that is a resting voltage and that your charge controller has not yet started the daily charge.

Regarding the shunt, get the 500 amp shunt. These shunts are not meant to run continuously at their rated current... they can get very hot. One of our forum members, (johnP, I think) uses shunts as precision fuses.

Regarding the Trimetric, I like mine. You must be very cautious with a shunt based battery monitor... they can give you an unwarranted sense of security that you are treating your battery well.

A battery monitor is often compared to the gas gauge in your car, but that is not a good analogy. The gas gauge in your car actually measures the level of gas in your tank. A battery monitor doesn't measure the level of anything. It is more like the odometer in your car. The odometer counts miles and the battery monitor counts ampHours.

Suppose you have a car that gets about 25 mpg and has a 15 gallon gas tank. Suppose also that your gas gauge does not work. What do you do? You use your odometer. For example: After a fill up you drive 150 miles and you expect that you have used 6 gallons and have 9 gallons remaining in your tank.

If you fill up the tank again you can, as above, use your odometer to estimate your gallons remaining.

But what if you do not completely fill your tank. For example, starting from a full tank you drive 150 miles and then you add 3 gallons to your tank and then drive 100 miles and then add 4 gallons to your tank and drive 150 miles and then add 5 gallons to your tank and drive 100 miles. At this point you estimate that you have 7 gallons remaining in your tank, but that estimate is not too accurate because your mileage is not ever exactly 25 mpg. The only time you know exactly how much gas is in your tank is when you have just filled it up (or when you run out of gas).

So it is with your battery monitor. The only time it is exactly accurate is when you fully charge your batteries and reset the battery monitor to read 100% full. It can be very accurate counting the amphours in and out of the battery, but it can only estimate the state of charge based on what you tell it of the battery capacity and of the battery efficiency. And remember, capacity and efficiency depend on temperature and vary over the life of the battery.

When a battery is cold or old, it has reduced capacity... if you draw 22 ah from a 200 ah battery, the battery monitor will say "89% SOC". But if your battery has an actual capacity of 100 ah and the battery monitor doesn't know that, it will still say "89% SOC" when your actual SOC is 78%.

By the way, you need to tell the battery monitor the efficiency of your battery... otherwise it can read 100% (by counting amps into the battery) before the battery is fully charged.

As mentioned, when your battery is 100% charged you can reset your trimetric to read 100% SOC (state of charge), but how do you know when the battery is at 100%? With flooded cells you use an hydrometer, with AGMs it is necessary to have faith in the manufacturer's recommendations. One way to know when your battery is charged is to use 'end amps', and your trimetric can use 'end amps' to automatically reset itself to 100% SOC.

When you hold the battery at absorb voltage, the current into the battery declines until the battery is 100% charged. At that point, the current declines no further and since the battery is charged, all that current is just making heat, gas, and corrosion. That current is 'end amps'.

The trimetric automatically resets to 100% based on 'end amps' criteria that you set. For example, you may program the trimetric to reset when the voltage is above 14.4 for a minute while the current is less than 4 amps.

Bottom line: the longer its been since a complete charge, the less you can trust your battery monitor. And you can't trust it at all if its not set up correctly. That said, battery monitors are valuable tools in estimating your SOC, but you have to understand their limitations.

By the way, there are a number of refinements that can improve the accuracy of battery monitors... for example, if the monitor knows the temperature of the batteries, it can adjust the Peukert factor and ampHour capacity of the battery. I don't find it necessary to have such refinements... by having the trimetric reset itself at least twice a week (using end amps criteria) it stays accurate enough to meet my needs (and my batteries get topped up to 100% at least twice a week). Also, I have flooded batteries so I can easily 'audit' the performance of my controller and my trimetric with an hydrometer.

--vtMaps

jackbombay · January 2016

Raj174 said:

This is the one I have.
ECPC404 Ammeter and Voltmeter
Intelligent Digital EV Battery Pack Monitor
Amp-Hour Counting

Check it out here:
http://www.electriccarpartscompany.com/ECPC404-Ammeter-and-Voltmeter-br-Intelligent-Digital-EV-Battery-Pack-Monitor-br-Amp-Hour-Counting-br-USA-Stock_p_425.html

This is a video on how to set it up:
https://www.youtube.com/watch?v=TJcToZoVzbw

I think it's what you are looking for.

Hmmm, that does do what I'm looking for at a notably lower cost.

jackbombay · January 2016

mike95490 said:

Even the very smart battery totalizators (amps in vs amps out) only do a mediocre job at guessing at the remaining juice in the battery. Just using a simple voltmeter & amp meter can get you close as you develop a "feel" for the readings, A battery under load or being charged will not give you accurate voltage SOC readings, the battery needs to be idle for several hours to let the electrolyte settle and then you can use Volts & temperature to estimate the state of charge.
Even using a $300 charge meter, you will still find ways to black yourself out.

Certainly, I don't have much concern about running out of juice, and I wouldn't rely that heavily on only a battery monitor to tell me how much juice I supposedly had left. My CC is mounted in a highly visible location so its easy to see if/when I need to eliminate loads on the battery.

I'm more wanting to confirm how many useable AH this battery actually has, and if it is significantly below its supposed capacity, I'll get a new battery, possibly from another manufacturer. If that happens I'd also like to be able to confirm that it has the AH capacity that it is advertized as having.

jackbombay · January 2016

My comments are in bold

vtmaps said:

You seem to be more concerned with capacity than SOC. A battery can have 100% SOC but still have low capacity. One of the many possible causes of that is chronic deficit charging, another is aging (either cycle aging or chronological aging). There are many ways to test your battery... you could check impedance or you can do a capacity test.

This is correct, I want to know if I am getting the 200 AH of capacity (~100 useable AH) that I paid for. Totally understood about that a battery can have a %100 SOC and also have low capacity, that is exactly what I seem to be dealing with.

Why do you think you have reduced capacity? I'm not saying you don't have reduced capacity, but a voltage of 12.5 in the morning after discharging 22 ah overnight is pretty good. (I assume that is a resting voltage and that your charge controller has not yet started the daily charge.

Math supports that I have reduced capacity, unless I am doing the math incorrectly. Well, I actually did the math incorrectly to "give the battery the benefit of the doubt" by assuming the heater ran all night which was far from the case, the heater draw was very likely 8 ah plus the 6 for the laptop puts me at 14AH for the night. The 12.5 was in the AM with no load before sun-up.

Theoretically, out of a 200 AH battery I should have 100 useable AH of power before hitting a resting voltage of 12.2, but that is not the case with this battery, at least doing rough consumption numbers on paper. [/b]

Regarding the shunt, get the 500 amp shunt. These shunts are not meant to run continuously at their rated current... they can get very hot. One of our forum members, (johnP, I think) uses shunts as precision fuses.

It would be pretty rare that 100A would go through the shunt, it would most often have a max of 12 to 13A running through it.

Regarding the Trimetric, I like mine. You must be very cautious with a shunt based battery monitor... they can give you an unwarranted sense of security that you are treating your battery well.

A battery monitor is often compared to the gas gauge in your car, but that is not a good analogy. The gas gauge in your car actually measures the level of gas in your tank. A battery monitor doesn't measure the level of anything. It is more like the odometer in your car. The odometer counts miles and the battery monitor counts ampHours.

Suppose you have a car that gets about 25 mpg and has a 15 gallon gas tank. Suppose also that your gas gauge does not work. What do you do? You use your odometer. For example: After a fill up you drive 150 miles and you expect that you have used 6 gallons and have 9 gallons remaining in your tank.

If you fill up the tank again you can, as above, use your odometer to estimate your gallons remaining.

But what if you do not completely fill your tank. For example, starting from a full tank you drive 150 miles and then you add 3 gallons to your tank and then drive 100 miles and then add 4 gallons to your tank and drive 150 miles and then add 5 gallons to your tank and drive 100 miles. At this point you estimate that you have 7 gallons remaining in your tank, but that estimate is not too accurate because your mileage is not ever exactly 25 mpg. The only time you know exactly how much gas is in your tank is when you have just filled it up (or when you run out of gas).

So it is with your battery monitor. The only time it is exactly accurate is when you fully charge your batteries and reset the battery monitor to read 100% full. It can be very accurate counting the amphours in and out of the battery, but it can only estimate the state of charge based on what you tell it of the battery capacity and of the battery efficiency. And remember, capacity and efficiency depend on temperature and vary over the life of the battery.

When a battery is cold or old, it has reduced capacity... if you draw 22 ah from a 200 ah battery, the battery monitor will say "89% SOC". But if your battery has an actual capacity of 100 ah and the battery monitor doesn't know that, it will still say "89% SOC" when your actual SOC is 78%.

This battery is getting a bit old at 4 years, it has been treated quite well for those 4 years though, only ever below 12.2v a couple of times and only briefly, everything is set up "as well as possible" with the ProStar30 CC, battery temp sensor and the "battery sense" voltage are connected so the CC has every bit of info it can use.

By the way, you need to tell the battery monitor the efficiency of your battery... otherwise it can read 100% (by counting amps into the battery) before the battery is fully charged.

As mentioned, when your battery is 100% charged you can reset your trimetric to read 100% SOC (state of charge), but how do you know when the battery is at 100%? With flooded cells you use an hydrometer, with AGMs it is necessary to have faith in the manufacturer's recommendations. One way to know when your battery is charged is to use 'end amps', and your trimetric can use 'end amps' to automatically reset itself to 100% SOC.

When you hold the battery at absorb voltage, the current into the battery declines until the battery is 100% charged. At that point, the current declines no further and since the battery is charged, all that current is just making heat, gas, and corrosion. That current is 'end amps'.

The trimetric automatically resets to 100% based on 'end amps' criteria that you set. For example, you may program the trimetric to reset when the voltage is above 14.4 for a minute while the current is less than 4 amps.

Bottom line: the longer its been since a complete charge, the less you can trust your battery monitor. And you can't trust it at all if its not set up correctly. That said, battery monitors are valuable tools in estimating your SOC, but you have to understand their limitations.

By the way, there are a number of refinements that can improve the accuracy of battery monitors... for example, if the monitor knows the temperature of the batteries, it can adjust the Peukert factor and ampHour capacity of the battery. I don't find it necessary to have such refinements... by having the trimetric reset itself at least twice a week (using end amps criteria) it stays accurate enough to meet my needs (and my batteries get topped up to 100% at least twice a week). Also, I have flooded batteries so I can easily 'audit' the performance of my controller and my trimetric with an hydrometer.

This is great info about battery monitors, thanks for taking the time to post it up. The limitations of battery monitors all make sense to me and I have no problem working with/around those limitations. Ultimately I'm not really looking for "the gas gauge" aspect of the battery monitor, I want something that will verify the batteries current capacity, and if this battery is ready for the scrap heap, I want to be able to verify the capacity of the replacement battery so I'll know I'm getting my money's worth on that purchase.

zoneblue · January 2016

Well thats simple, just load test the pack. Time a known load until you reach your cut off voltage. This is kind of hard on batterys but its the acid test of remaining life in a battery. All commerical, industrical and miltary batteries are load tested at regular intervals, and anything below say 95% is retired.

jackbombay · January 2016

zoneblue said:

Well thats simple, just load test the pack. Time a known load until you reach your cut off voltage.

I suppose I could wire up a few incandescent lights to get a 4 amp draw (or so) and see when it hits 12.2, but when it hits 12.2 and I remove the load the resting voltage will come back up. In light of this, I'm not exactly sure what is the correct way of doing a load test, how is the voltage under load vs at rest issue addressed?

zoneblue · January 2016

For load testing you ideally need access to the published discharge curves. All (decent) battery manufacturers provide these for different discharge rates. Pick a place on teh curve thats pretty low, but not as low as 0 (else youll risk reverse charging the low cells.
In other words under discharge 20% SOC at 0.1C discharge rate will have a different terminal voltage than using a 0.2C rate The rest voltage doesnt really factor here, however if you have the luxury of being able to truly rest teh pack after, you should be able to use that to verify the load test final SOC. SG even better for FLA. However a load test is somewhat desctructive in that you can only know if it will go to 10% by actually taking it there. Catch 22.

Vic · January 2016

When doing Load Tests, would suggest that one carefully monitors the battery bank voltage. Initially, the rate of change in bank voltage is fairly steep.

Then there is a fairly broad, flat part of the discharge curve, where the rate of change in voltage is quite small verses time.

When the rate of change in battery voltage increases again, one should really terminate the test, and begin recharge, as this second knee of the curve usually indicates that about 70 - 80% of Capacity has been removed from the battery (or at least removed from the weakest cell).

To the extent possible, when this second, higher rate of change part of the curve is reached, one should measure each individual battery or cell (to the extent possible). As, this will indicate the battery or cell which is weakest.

Further discharge of the bank can easily and quickly result in one cell becoming completely discharged, and quite possibly be "charged" in reverse. This reversal is almost always sudden DEATH for that cell/battery.

Some batteries do not like to be this fully-discharged. There is a reasonable judgment involved when doing load and capacity tests.

For load tests, and for cycling batteries here, we use electric heaters, connected to the AC output of inverters.

Just my opinions, Vic

vtmaps · January 2016

There's not much I can add to zoneblue and Vic's responses.

zoneblue said:

For load testing you ideally need access to the published discharge curves. All (decent) battery manufacturers provide these for different discharge rates.

Vic said:

There is a reasonable judgment involved when doing load and capacity tests.

Manufacturer's published rates are usually for batteries used in applications where a battery is scrapped if it's lost a small amount of capacity. For example, a forklift battery is considered scrap if it is at 80% capacity. But that "scrap" could give you a few good years in an off grid situation. That's why Vic writes of judgement... don't try the manufacturer's load test on a battery that might fail the test.... failure could be death to the battery.

And don't try any load test on a cold battery... cold batteries have lower capacity and higher internal resistance. You could design a load test for a cold battery, but you would have to compensate with a reduced discharge rate as well as a reduced capacity.

--vtMaps

zoneblue · January 2016

What Vic said is spot on. An older battery is by defintion not going to perform like a new one, and there will always be a weaker cell or cells. Its those cells that will make the terminal voltage tumble at the bottom of the discharge curve. If you have a data logger you can easily plot the curve as you discharge, otherwise take regular readings and watch for the trend.

Vic · January 2016

vtmaps said:

There's not much I can add to zoneblue and Vic's responses.

zoneblue said:

For load testing you ideally need access to the published discharge curves. All (decent) battery manufacturers provide these for different discharge rates.

Vic said:

There is a reasonable judgment involved when doing load and capacity tests.

Manufacturer's published rates are usually for batteries used in applications where a battery is scrapped if it's lost a small amount of capacity. For example, a forklift battery is considered scrap if it is at 80% capacity. But that "scrap" could give you a few good years in an off grid situation. That's why Vic writes of judgement... don't try the manufacturer's load test on a battery that might fail the test.... failure could be death to the battery.

And don't try any load test on a cold battery... cold batteries have lower capacity and higher internal resistance. You could design a load test for a cold battery, but you would have to compensate with a reduced discharge rate as well as a reduced capacity.

--vtMaps

vt, good point about not wanting to do a load test on a cold battery. Thanks, Vic

arby · February 2016

Vic posted--
"The trimetric automatically resets to 100% based on 'end amps' criteria that you set. For example, you may program the trimetric to reset when the voltage is above 14.4 for a minute while the current is less than 4 amps. "

Vic, what would those numbers be for a 48 volt system?
Would they be 57.6 V and current less than 16 amps, or current less than 4 amps?

Thanks,
arby

vtmaps · February 2016

arby said:

Vic posted--
"The trimetric automatically resets to 100% based on 'end amps' criteria that you set. For example, you may program the trimetric to reset when the voltage is above 14.4 for a minute while the current is less than 4 amps. "

Vic did not post that, I did. For a 48 volt system you quadruple the numbers. However, the numbers you should use on your system depends on what batteries you have. Different batteries have different needs. Even identical batteries can have different needs... what a battery needs depends, in part, on its history... how the loads are applied (continuous, intermittent, high or low current), and similarly, its charging history.

The numbers I picked in the quote were used to make a point, they are not necessarily the numbers that you should use.

Ideally, a charge controller will go to float as soon as the battery is fully charged, and that would coincide with end amps being achieved.

I don't believe (I could be wrong) the MX charge controller can regulate the absorb time by end amps criteria. I think it uses time. Your trimetric and your MX are using different methods to decide the battery is fully charged. Therefore, there are likely to be days where the MX goes to float (based on time) without the trimetric meeting its end amps criteria. And there are likely to be days where the trimetric resets while the MX is still absorb charging.

Of course, all of that assumes the trimetric end amps settings are correct for your battery. If you set them wrong it will reset every day whether or not your battery is fully charged, or it will never reset.

--vtMaps

arby · February 2016

Thanks vtMaps,
I believe you are correct. The MX60 doesn't seem to have the end amps feature.
When I add my new panels this summer I will be switching to a Midnite 200.

vtmaps · February 2016

arby said:

Thanks vtMaps,
I believe you are correct. The MX60 doesn't seem to have the end amps feature.
When I add my new panels this summer I will be switching to a Midnite 200.

Don't forget the whizbangJr if you want to do end amps charging. Why a Classic 200 instead of a Classic 150?

--vtMaps

arby · February 2016

I have the whiz bang as well. I was concerned about too high voltage on cold mornings blowing my MX60. I have seen voltages as high as 125, 130 with the panels I now have. The MX60 is supposedly good to 150 so I went for the Classic 200 to be on the safe side.
Going to be adding 6X280 watt panels wired at 72 volts.

vtmaps · February 2016

arby said:

I have the whiz bang as well. I was concerned about too high voltage on cold mornings blowing my MX60. I have seen voltages as high as 125, 130 with the panels I now have. The MX60 is supposedly good to 150 so I went for the Classic 200 to be on the safe side.
Going to be adding 6X280 watt panels wired at 72 volts.

I strongly suggest the Classic 150. More capacity and more efficiency. It will take an input voltage of 198 volts to damage a classic 150 on a 48 volt system.

--vtMaps

arby · February 2016

Too late for me. I already purchased the 200 last Spring. I was under the impression that you had to add battery voltage to incoming voltage.

Vic · February 2016

vtmaps said:

arby said:

Vic posted--
"The trimetric automatically resets to 100% based on 'end amps' criteria that you set. For example, you may program the trimetric to reset when the voltage is above 14.4 for a minute while the current is less than 4 amps. "

Vic did not post that, I did. For a 48 volt system you quadruple the numbers. However, the numbers you should use on your system depends on what batteries you have. Different batteries have different needs. Even identical batteries can have different needs... what a battery needs depends, in part, on its history... how the loads are applied (continuous, intermittent, high or low current), and similarly, its charging history.

The numbers I picked in the quote were used to make a point, they are not necessarily the numbers that you should use.

Ideally, a charge controller will go to float as soon as the battery is fully charged, and that would coincide with end amps being achieved.

I don't believe (I could be wrong) the MX charge controller can regulate the absorb time by end amps criteria. I think it uses time. Your trimetric and your MX are using different methods to decide the battery is fully charged. Therefore, there are likely to be days where the MX goes to float (based on time) without the trimetric meeting its end amps criteria. And there are likely to be days where the trimetric resets while the MX is still absorb charging.

Of course, all of that assumes the trimetric end amps settings are correct for your battery. If you set them wrong it will reset every day whether or not your battery is fully charged, or it will never reset.

--vtMaps

FWIW, the venerable MX-60 DOES have CC EA capability -- that is all that I've ever used with the MXes. BUT, one needs to be sensitive to loads on the Inverters when setting an acceptable EA value. This is probably moot, as arby has a Classic, and can use REAL EA, with the WBjr.

And for the Flooded batteries here, we use an EA setting of about 1.11% of 20 hour Capacity ... today it is 14.7 A on a 1280 Ah bank, at a reasonable Vabs (which is temperature-compensated).

If any of this matters. Vic

arby · February 2016

Thanks Vic-- interesting for sure..
The Classic is still in the shed in its box waiting for the new panel pole , cement mixing and all the hard work.. The MX60 is the one in the system.
My 530's are 400 AH, so by the 1.11% calculation I get 4.44 end amps.
RB

Vic · February 2016

arby said:

Thanks Vic-- interesting for sure..
The Classic is still in the shed in its box waiting for the new panel pole , cement mixing and all the hard work.. The MX60 is the one in the system.
My 530's are 400 AH, so by the 1.11% calculation I get 4.44 end amps.
RB

Hi RB,

OK on the Classic not yet being in service.

Couple comments about CC EA. As you know, the MX-60 should have the EA function, BUT, perhaps if it has very old Firmware, it might not ...

Setting MX EA amperage is either in the Advanced, or perhaps the Misc menu. You will need to estimate the approximate, average loads on the Inverter, and add this current value, in amps to the place that you want to start for the 1 - 1.5% of 20-hour Capacity.

If you have time to watch the latter part of an Absorb stage, when the battery charge current just stops decreasing, this is about the nominal value for EA ... But, it helps a lot, if you have a Shunt in the Negative battery lead, that can tell YOU what the charge current is, that is going into the battery. Your system may not have this Shunt.

Flooded batteries are quite forgiving, and batteries are good at averaging out the effects that loads on the inverter have on the CC's EA function.

And, for Surrette batteries, the actual 20 hour Capacity is quite close to the 15 hour C, as these Capacity values are stated, as if the battery was filled with 1.280 SG electrolyte, when 1.265 is almost always used, except for Locomotive Starting batteries, and perhaps those shipped to Tropical locations.

If your inverter will have large loads running when the batteries are nearing the end of Absorb, this could affect the effectiveness of an Absorb stage, but, if such an event is not a common occurrence, the batteries will average out these things, and all should be OK.

The real test of how well Flooded batteries are being charged, is, of course, SG measurements with your Hydrometer. You can make adjustments to the EA setting based on these SG readings.

One other thing, is that the 1 - 1.5% (actual) battery charge current for the EA setting is really the measure of only the charge current going into the battery, and it needs to be at a reasonable Absorb voltage, AND must be temperature-compensated. Here the nominal Vabs is about 2.42 or 2.43 V per cell.

As batteries age, the EA value will probably need to be adjusted by small amounts.

I hope that you have the WBjr, and a Shunt for use, when the Classic is installed, as this setup will show exactly the battery charger current, and of course, allow the Classic to use actual charge current to end Absorb.

FWIW, Vic

Battery monitor questions.

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