Trojan battery charging advice please

[hammick]

I have been testing my new Schneider Conext SW4048 inverter and Trojan L16RE-A batteries (48v bank at 325ah). To my surprise the inverter does not have a setting to extend the absorption time until float. I have read the best practice is to return 110 - 120% of the amp hours removed.

The Conext inverter goes to float at the earliest of the set absorption time or when return amps are at 2% of bank capacity. The 2% cannot be adjusted.

With the inverter setting to 325ah capacity my Bogart TM2030 meter would show 103% amp hours replaced and 98% charged when the inverter went to float. If I lie to the inverter and tell it I have a 50ah battery (that's the lowest it will go) my Bogart meter will show 107% amp hour replaced and 100% charged.

Anything else I can do to extend the absorption time to get the amp hours replaced to 120%?

I have requested that Schneider put a setting in their next firmware to allow a custom absorption period after the float criteria is met. I'm not holding my breath that this will happen.

[PNjunction]

Can you adjust the float voltage to meet or be near your absorb voltage? That might be a work-around. Or at the very least, set the float voltage relatively high. I'm assuming you are doing cyclic duty, and not standby / weekend warrior stuff.

[sensij]

A few thoughts...

In general, I am cautious when a relatively cheap piece of equipment wants to override or change the logic of something that is much more expensive. Doesn't mean it is wrong, but just that it worth looking for ways the results might be misleading you.

With that in mind, battery efficiency is not perfectly linear with respect to DoD. Have you looked at different levels of discharge? The amount of "replaced Ah" required may vary.

Also, you mentioned in other threads that you are charging at 22 A. If that is true here as well, that is kind of low for this battery. You might want to try charging at something closer to what Trojan recommends and see if better mixing lets you get more charge into the battery.

These are new batteries, right? The way in which they behave initially may not represent how they behave one the plates have been formed.

[hammick]

Thanks for the responses guys. I can set the float to match the absorption (limit for both is 64v). That certainly would work but I will have to change the float setting daily once I get the desired return amps or I will be putting back much more than 120% and boiling off liquid quickly I suspect.

I guess what I am really asking is whether it really matters if I put back between 110 - 120% amps or if 103 - 107% is fine.

Sensij, the Bogart TM2030 is simply a battery monitor that uses a 500 amp shunt. It doesn't change anything in the charging process. It monitors a lot of stuff including return amp percentage during the last charge cycle.

What I am doing is changing the battery bank capacity in the inverter's charge settings to 50 amps which is the minimum setting. By doing this the inverter's charger goes to float when charging amps taper to 1 amp rather than 6.5 amps. The inverter goes to float at 2% of bank capacity amps and there is no setting to change this.

My settings that can be customized are bulk voltage, absorb voltage, float voltage, equalize voltage, ah capacity, temperature comp and either three stage charging or two stage charging.

My inverter is rated to charge at 45a but only if fed with AC to both legs (240v). When fed with just 120v on leg 1 it charges at half its rated current (i.e. 22.5 amps). My Bogart monitor is showing 22 amps of charge during Bulk charging.

Once this equipment gets installed at my off grid location the charging will primarily take place using the Conext MPPT charge controller which has identical settings as the Conext inverter so unless they add additional options in a future firmware I'll have the same issue (assuming only 107% return amps is even an issue).

When charging using my generators I suspect my 2400w Yamaha inverter will charge at 22a and with my big 7000w generator I will be charging at 45a.

Yes my batteries are new and I only have taken them down to 80% SOC and then fully charged three times. I did the initial refresh charge recommend by Trojan using a 20a 12v manual charger with two batteries in series.

My specific gravities were all at 1.280 after the initial refresh charge.

[Sunking]

First huge mistake you are making is using your Bogart to determine the battery SOC. No battery gives a chit about your Bogart. You cannot use Voltages or Amp Hours In/Out to determine SOC on FLA batteries period. The Bogart is just a very expensive toy for you to play with and has no real use. You cannot use Coulomb Counting on FLA batteries. It would have to be re-calibrated every cycle. Mr Peukert will not allow Bogart to work.

Second issue is Absorb is not a Timed Event. This is why solar cannot be used effectively to charge a FLA battery using 3 Stage algorithm. There are not enough hours to go through all the 3 cycles. Three Stage charging does not work with Solar and FLA batteries period. Give it it will not happen. Absorb is a Constant Voltage held on the battery until current tapers to .02C to .04C. Depending on DOD and Temperature can take 4 to 8 hours well after dark thrity. Only stiff commercial or generator sources can do that. That is why a Generator is mandatory for any off-grid system.

OK that does not mean you are dead in the water. You just do not know what to do or how. You must use a very simple $10 peice of equipment no FLA battery owner can afford to be without, and a different strategy I call Maximum Smoke. Read "Are You Killing Your Batteries"

[hammick]

Sunking I have two hydrometers that are temp compensated, I know how to use them and use them often. That's how I determine whether my batteries are fully charged. I use the Bogart as the next best thing. If you know of a better battery monitor please enlighten me. I read you max smoke thread months ago and you make some good points.

I'm certainly not an expert but I have a 12v solar system on our travel trailer. Two six volt Interstate batteries for a 208ah bank. During Montana summer I have no problem getting them fully charged and into float using a 160v panel and Blue Sky PWM charge controller. This is from 70 - 80% SOC and we do run the generator for probably 20 minutes each morning to make coffee.

I don't agree with you that the Bogart meter is useless. When I take the bank down to 80% SOC according to the Bogart and turn everthing off and let the batteries rest for about an hour the voltages are spot on with 80% SOC. When I charge it tells me return amp as well as return amp percentage. The highest I can get with my current settings is 107% return amps according to the Bogart. I think the Bogart in combination with taking specific gravity readings makes an excellent tool and it will look great flush mounted in our living area.

PNJunction I checked and I can indeed adjust the float voltage as high as 64v. Once I get everything hooked up next spring I will adjust the float higher if needed to get them fully charged.

The Schneider inverter and solar charge controllers do have a two stage setting for just bulk and absorb. Not sure if it just terminates charging at the same time it would go into float if three stage were selected or if it uses a different charging algorithm.

Thanks for the info guys.

[Sunking]

I don't agree with you that the Bogart meter is useless. When I take the bank down to 80% SOC according to the Bogart and turn everthing off and let the batteries rest for about an hour the voltages are spot on with 80% SOC.

Hogwash you just aggreed with me. Your Bogart is useless on a working system. It only works when everything is off and rested for several hours. That is completely worthless on a working system

When I charge it tells me return amp as well as return amp percentage. The highest I can get with my current settings is 107% return amps according to the Bogart. I think the Bogart in combination with taking specific gravity readings makes an excellent tool and it will look great flush mounted in our living area.

That is useless information. Your Bogart does not take into account of Peukert, Temps, Charge Efficiency, and Age.

There is only one way to determine the true and real time SOC, and that is with a Hydrometer. There.is nothing else that can do that with FLA batteries. Coulomb Counting is only practical with certain Lithium batteries. and even then it is a Ball Park measurement that needs weekly calibration. The reason it works with some Lithium batteries is because Charge Efficiency approaches 99% and very little Peukert Effect. Temp is still an issue.

What you can do if you insist on using voltage as an indicator is make a conversion table for both Charge and Discharge profiles:
To determine SOC Set Point Voltages on Discharge

1. Put all or as many loads as possible on the battery. Disconnect any in coming charge sources.
2. Take the specific gravity of one cell, This assumes all cells are EQUAL to start with at 100%
3. Take another reading 15 minutes and ½ hr later this should give you an indication of how fast the batteries are dropping.
4. Continue to take readings until 50-55% state of charge is reached according to the specific gravity readings.
5. Take and record voltage readings (when on load) of any meters to be used for monitoring the state of charge and take a voltage reading across the terminals of the battery.bank
6. These readings will then give you a very accurate voltage reading which can be used in the future either as a set point for the inverter or as a day to day monitoring parameter.

For charge use the same process starting from 50% DOD up to 100%

PNJunction I checked and I can indeed adjust the float voltage as high as 64v. Once I get everything hooked up next spring I will adjust the float higher if needed to get them fully charged.

PN is telling you to use Max Smoke. All major battery manufactures have revised charging profiles to much higher voltages.

For Solar Trojan and Rolls have done away with traditional 3-stage Charging. They both state Bulk = Absord = 2.45 vpc until current tapers to .03C. Solar systems might be able to do that during summer months, but not likely in shorter Fall Winter and Spring Months. In that case you need to go even higher voltages to the point where a HYDROMETER says you made it to 100% SOC. With a generator time is not an issue and you can use normal Absorb single stage until current taper to .03C

It is a never ending battle and can only be determined with a HYDROMETER.

[hammick]

Here is what the SW4048 manual says about the two-stage charging:

"Two-stage (bulk and absorption only, no float) mode differs from an ordinary
three-stage charge mode in that it does not continuously maintain the battery at
float voltage. Instead, the Conext SW begins charging the battery in bulk mode
whenever the battery voltage drops below the recharge level. While the battery
voltage is above the recharge level, the inverter continues to pass power through
from the AC source to the loads but does not actively charge the batteries."

I'm thinking two stage and setting recharge to 50.9 volts will pretty much keep the batteries in bulk and then absorption all day assuming any loads are being used.

[Sunking]

OK let's make sure you know what Bulk Absorb, and Float really mean. It is really easy stuff.

Bulk is a Constant Current mode. All that means is the charger is a current supply without regard to Voltage. It just pumps a fixed rate of current. In a solar system as much as the panels can supply so it will vary with Sun Light intensity. If it is a AC charger with a stiff source the current is the Current Limit rating of the charger. So if it is say a 50 amp charger, it supplies 50 amps period. Bulk mode terminates when the a Set point Voltage is reached. As a battery charges its voltage rises in a Constant Current mode. This is due to the Open Circuit Voltage of the battery, and the Internal resistance of the battery. Example if the OCV of a battery is say 22 volts with an Internal resistance of .010 Ohms if we supply a current of 50 amps the voltage will be 22 volts + [50 amps x .01 Ohms] = 22.5 volts. As the battery charges the OCV voltage rises. So now we set Bulk to terminate at say 29 volts. When the battery OCV reaches 28.5 volts, the battery voltage is 29 volts with 50 amps flowing into it and now we terminate Bulk and enter Absorb.

Absorb is a Constant Voltage. So in reality nothing really switches between Bulk and Absorb if we set Bulk = Absorb Voltage. All that happens is the charger maintains 29 volts in this example. So when the battery OCV hits 28.5 volts the charger maintains 29 volts. What happens is the Battery OCV voltage continues to rise to equal the Charger Voltag eof 29 volts. As the OCV voltage rises the Current starts to TAPER off toward 0 amps. When the Current Tapers off to .03C the battery is fully saturated and OCV roughly equal the charger voltage of 29 volts. Since th evoltages are equal, no current flows. At that point the battery is fully charged and we terminate Absorb and can either turn of the charger, or switch to Float.

Float is another Constant Voltage mode just like Absorb. It i sjust a lower voltage than Absorb. Float i sto maintain the batytery at 100% SOC., You can even charge a Battery fully with Float Voltage, it just takes longer. In fact Float is the best charge method for Lead Acid batteries. You just cannot use it with solar because there is not enouggh time in a day to get charged.

So what you want to do with Solar is by using a Hydrometer is find what Bulk/Absorb voltage set point it takes to get to 100% when the sun sets. In winter months you may not ever be able to get to 100% no matter how high you set the voltage. In that case all you can do is set it to as higgh as you can to force the Controller to stay in BULK all day to pump as much power as the panels possible can generate. Once you reach Absorb, th epanel power is not at full power and tapers off. In winter you wil not make it to th epoint where the batteries reach full charge. Absorb is not a timed event.

[hammick]

Thanks Sunking. I do understand what the three stages mean and how they work. What I am confused about is why I would want to use two stage charging on my Schneider equipment instead of three stage. My confusion is based upon my assumption of how the charger will work in the different stages. I may be wrong on how it works.

Stage 2:
Bulk set to 59.3v per trojan specs
Absorb: 58.8 per trojan specs
charging stops when absorption current tapers to 6.5 return amps (2% of 325ah)
New charge cycle resumes when batteries drop to 50v (or whatever I choose in the settings)

Stage 3:
Bulk set to 59.3v per trojan specs
Absorb: 58.8 per trojan specs
Float set to 54v per trojan specs
Batteries go to float when absorption current tapers to 6.5 return amps (2% of 325ah)
New charge cycle resumes when batteries drop to 50v (or whatever I choose in the settings)

If my understanding is correct would it not be better to have the batteries float charging a 54v rather than no charging at all?

In reality this doesn't mean much as I won't be there most of the time, everything will be shut does except the CC and the batteries will be floating when the sun is out. I'll probably set the float to Trojan's low spec which is 52.8v to reduce electrolyte loss.

[Sunking]

Real simple if you are using a Commercial AC Charger, then by all means you want FLOAT. .

Allow me to take that one step further. If the battery is CYCLED DAILY, then you do want a conventional 3-stage charger . An application like a Floor Machine, Golf Cart, Wheel Chair or something like that where it is used during the day for 12 to 16 hours and then recharged every night. You need that speed and time to complete to FLOAT.

If we are talking Stand By or Emergency Power then you want FLOAT only with the ability to EQ once in a while. Float is the kindest and Gentle algorithm there is. This is what all critical applications use. Down side is it can take up to 24 hours, or as quick as 4 hours. Example your typical Cell Tower uses a 1200 amp rectifier on a 1500 AH battery meaning they charge them at near 1C rate. However Telecom batteries have more in common with SLI batteries than Deep Cycle so non eof that applies to you.

But let's answer your question directly. You want Float if you can get 100% charged up. If you had a true Off-Grid Battery system if you can ge to 100% SOC, you differently want to go to Float so the panels can supply power to the loads while reserving battery power for after dark. In a Hybrid like you have, you still want FLOAT to keep the batteries fully charged and ready to go like an Emergency system.

Only thing I can think Schnider is thinking is batteries need cycled which I do not buy into. At least on a daily basis. You can make a good argument for an exercise say once a week to discharge them, and then recharge. Bu tin that week of rest you want them on Float. There is not much else you can do to destroy a battery to leave it off a charger, especially at room temps or higher.

Experiment a bit with voltage set points. Let your Hydrometer tell you what is really going on. No voltage device or Coulomb Counter can tell you what is really going on with your batteries. They are just an indicator of what MIGHT be going on. Think of them like a weather forecast as that is all about all they are worth. They are wrong more times than they are right. Hydrometer gets it right every time anytime.

Hope that helps.

[Riley5781]

Interesting thread.
I have a number of lead acid batteries from my boat and RV type solar setup that just sit in my garage all winter (not being used).
I've been leaving them on a commercial AC charger that has what I assume is a Float mode (multi-stage charger).

My question is: after a month or so of being on this charger, what's the best thing to do for the batteries? Leaving them on Float OR disconnect them and just leave them over the winter?

[Sunking]

Interesting thread.
I have a number of lead acid batteries from my boat and RV type solar setup that just sit in my garage all winter (not being used).
I've been leaving them on a commercial AC charger that has what I assume is a Float mode (multi-stage charger).

My question is: after a month or so of being on this charger, what's the best thing to do for the batteries? Leaving them on Float OR disconnect them and just leave them over the winter?

Batteries can remain on Float. Indefinitely providing the voltage is set correctly.

In older Telephone offices that use ole Western Electric Round Cells have been on Float for 30 plus years.

[hammick]

I heard back from Schneider tech support. They asked for the charging specs on my batteries and said that in addition to increasing the equalization voltage in the next firmware they would do their best to implement a setting for additional absorption charging time

[Sunking]

I heard back from Schneider tech support. They asked for the charging specs on my batteries and said that in addition to increasing the equalization voltage in the next firmware they would do their best to implement a setting for additional absorption charging time

Is the charging done by commercial AC power or generator as most hybrid systems do?

If correct, their answer is unacceptable. Absorb is not a timed event, Even if it were could never be done repeatably with Solar. With respect to FLA batteries manufactures charging specs do not differ much, they are all so close, the differences are insignificant and can be easily modified to fit any manufacture. The only real difference, and it is small is the voltage set points.

Generically they all do this.

Bulk Charge at 10 to 15% of C where C = the 20 hour rate AH capacity of the battery. So if you have a 100 AH battery is 10 to 15 amps in a Constant Current Mode until the battery reaches 2.35 to 2.5 volts per cell. As you can see it is the voltage that varies the most.

Absorb Charge holding a Constant Voltage of 2.35 to 2.5 vpc until current tapers to 2 to 3% of C. Again using a 100 AH model you hold the voltage until the current tapers to 2 to 3 amps. Again the only thing that varies is the actual voltage. There is no time assigned to that. It can take 2 to 8 hours.

Float at 2.2 to 2.3 volts.

Any battery charger manufacture that makes Smart Chargers can do that for any battery. They do not care what the manufacture or model is. It is up to you to buy the appropriate size charger in Amps to match the battery capacity. Again if you had a 100 amp battery, you are looking for a 10 to 15 amp charger. Then all you do is set the Absord and Float Voltage, and set the Absorb Amps cutoff value.

Now if you charge with Solar, you cannot do that. Instead they make Absorb a timed event. Problem is it is not a timed event. So you ask why they make it a timed event. Answer is because there are not enough Sun Hours to complete a proper Absorb cycle. So what can you do? Simple crank the Voltage up and use you hydrometer to make up for it as quick as you can.