Supercharge Your Solar Charge Controller Settings

[pteck]

I recently checked and watered my 6V Lead Acid batts, and while at it, also checked each cells health with a hydrometer.

The hydrometer showed that not all cells were balanced. Roughly half the cells on each battery showed excellent health/charge (1.300), while the other half was a tad lower at 1.275. While this could be normal wear, my batts are rather new at 2 years old and tendered each day with 400W solar. I decided to dig in deeper and check out my solar charge controller settings.

To my surprise, while my solar charge controller was set correctly on flooded lead acid (FLA), inspection of the specific voltages showed that the defaults were way tepid, especially absorption and equalization voltages.

Default FLA solar controller voltages:
Bulk (max current), Absorption (14.4V), Equilization (14.6V), Float (13.8V)

GC2 charging recommendation:
Bulk (14.46), Absorption (15.3V), Equilization (15.6V), Float (13.4V)

Figures why the cell balances were off. So I set the charge controller to "user" profile and punched in the desired voltage targets.

One day later, checked again with the hydrometer and bam, all cells are full-up hunky dory measuring in at 1.300. Should have a bit more reserve capacity this way as well. Never figured defaults for FLA would be significantly off optimal, or perhaps they are just too conservative.

[GMFL]

I did the same with my Victron 100/30 and set it to Trojans specs for there T105 lead acids

[AirMiles]

Here are the settings I use on my Victron 100/30 with a pair of Duracell EGC2 wet-cell golf cart batteries. These settings keep my batteries testing at 13.0 on a Hydrometer. These settings cause my batteries to use significant amounts of water. I check and refill my water levels monthly.

Also, you can manually “equalize” to rebalance the cells. I only use manual equalize when the Airstream’s store/use switch is in the store position to avoid running 15.2V into my 12V appliances.

Link to charging parameters http://www.eastpennmanufacturing.com...eters-1913.pdf

[waninae39]

victron has settings on their site also, they also cover different lion chemistry types

[uncle_bob]

Hi

"Golf cart batteries" are a bit different than a normal lead acid wet cell. They are optimized for lots of fast charge / discharge at the risk of a bit more self discharge in storage. You can dig all this out by comparing the data sheets on the various batteries.

In a system like an RV where you have *two* controllers, each of them can get into the act of taking the battery up to this or that voltage to do this or that task. Given the way T-105's are designed, there isn't a lot of risk from two chargers both doing this or that. Indeed, you probably should program both your solar controller *and* your charger / converter to match what the batteries need.

Regardless of one or two devices running up to the higher voltages, you *will* need to check water levels a bit more often when "running them right". They will put out a bit more "steam" at the higher voltages.

The other risk is the same as with all batteries. The magic voltages are temperature dependent. If your charging gear all has proper temperature probes and compensates for this, you are fine. If not, there is a risk of overdriving the batteries. The voltages likely drop by around a half volt when it gets hot. Running the converter "low" matches up to the "hot battery" situation. What happens in the "over drive" case? You push a lot more water out of the batteries .....ultimately you could damage them.

Bob

[pteck]

Originally Posted by AirMiles

These settings cause my batteries to use significant amounts of water. I check and refill my water levels monthly.
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How much water are you adding monthly?

I've been typically checking my batts every 1/2 year and they take very little if any water.

I could easily switch between the default and user profiles if it proves to consume much more water.

The manufacturer Absorption voltage is specified with a time duration. Perhaps I can tweak the voltage and duration down too as it's probably the main driver for water loss.

Originally Posted by uncle_bob

Hi

In a system like an RV where you have *two* controllers, each of them can get into the act of taking the battery up to this or that voltage to do this or that task. Given the way T-105's are designed, there isn't a lot of risk from two chargers both doing this or that. Indeed, you probably should program both your solar controller *and* your charger / converter to match what the batteries need.

Regardless of one or two devices running up to the higher voltages, you *will* need to check water levels a bit more often when "running them right". They will put out a bit more "steam" at the higher voltages.

The other risk is the same as with all batteries. The magic voltages are temperature dependent. If your charging gear all has proper temperature probes and compensates for this, you are fine. If not, there is a risk of overdriving the batteries. The voltages likely drop by around a half volt when it gets hot. Running the converter "low" matches up to the "hot battery" situation. What happens in the "over drive" case? You push a lot more water out of the batteries .....ultimately you could damage them.

Bob

Great points Bob.

I don't ever bother and rarely use my factory installed converter-charger now that I have 400W solar. Heck, I rarely even bother plugging in my RV to electrical hookups.

I do have a thermostat on my solar charger which I believe is key to protecting the batts and helping them perform optimally.

[rmkrum]

Agree. 250 watts of solar panel on the roof with an MPPT solar controller with the temperature probe in the battery box is the best route. That’s what I have, and it coddles the 6 volt GC-2 wet batteries.

Only a couple ounces of water a month, and a lot of that is probably due to the stunningly low humidity and high temperatures here in the SoCal desert areas. I have a battery watering system so it’s quick and easy.

Airstream is parked in full sun, with one FantasticFan open. The fan probably runs all day when the sun is out, but batteries are still fully charged at dusk. I set to “Use” to help keep internal temperature ‘reasonable’ in storage yard.

[AirMiles]

How much water per month? I typically add two or three full Big Red hydrometers of water per cell each month. You will need to check more frequently with your new higher voltage settings. I do have Temperature and Voltage compensation on my Victron solar controller and also leave my PD4655 converter disconnected except when I need to boost charge the batteries a few hours per year.

[uncle_bob]

Hi

As you add more water, you need to get more careful ( or at least be careful ) of the water source. Tap water is generally a bad idea. The stuff that goes in it at the water plant to keep the pipes from rusting isn't the best of the best for your batteries. Most well water has the same issues. Distilled water is best, a gallon jug should last you a *long* time.

Most grocery and drug stores have real distilled water (it will be on the label) on the shelf these days. Even at a couple bucks a jug, it's a lot cheaper than taking a few years off the life of the batteries. Will this or that water source take a few years off? ...... who knows .... I for one would not want to discover that

Note that normal bottled water likely is no different than what comes out of your tap at home in this regard. You are after something a bit different. Even water from an RO setup is not quite as good as distilled water. It's a *lot* better, but not quite the same thing.

Bob

[pcskier]

Originally Posted by pteck

So I set the charge controller to "user" profile and punched in the desired voltage targets.

My controller is set to the default position of '2' on the rotary switch on the controller. Do you just leave it in that position and then change the voltage targets via the app? I have two brand new Trojan T105s and want to get this little twist in the plot dialed in for sure.

[AirMiles]

Originally Posted by pcskier

My controller is set to the default position of '2' on the rotary switch on the controller. Do you just leave it in that position and then change the voltage targets via the app? I have two brand new Trojan T105s and want to get this little twist in the plot dialed in for sure.

Yes. I just realized my temperature compensation setting was incorrect and changed it to -18mV. Six cells times -3mV

Here is a link to Trojan T105 charging parameters. https://www.trojanbattery.com/pdf/da...ata_Sheets.pdf

[CarterKraft]

Originally Posted by pcskier

My controller is set to the default position of '2' on the rotary switch on the controller. Do you just leave it in that position and then change the voltage targets via the app? I have two brand new Trojan T105s and want to get this little twist in the plot dialed in for sure.

from the manual

User defined algorithm:
Any setting change performed with Bluetooth or via VE.Direct will
override the rotary switch setting. Turning the rotary switch will
override prior settings made with Bluetooth or VE.Direct.

[pcskier]

Originally Posted by AirMiles

Yes. I just realized my temperature compensation setting was incorrect and changed it to -18mV. Six cells times -3mV

Here is a link to Trojan T105 charging parameters. https://www.trojanbattery.com/pdf/da...ata_Sheets.pdf

Thanks. I had that sheet printed out and in my pile along with various other diagrams etc. for my solar and 6v upgrade. I went ahead this afternoon and changed my float voltage to 13.50 and bulk to 14.82, and equalize to 16.20 as per the specs. Thanks for bringing it up pteck and starting this thread. I might have gotten there eventually, but who knows when I might have actually taken the time to read the manual.

Originally Posted by CarterKraft

from the manual

User defined algorithm:
Any setting change performed with Bluetooth or via VE.Direct will
override the rotary switch setting. Turning the rotary switch will
override prior settings made with Bluetooth or VE.Direct.

Thanks. Once I finish this install I need to spend some time and actually read the manual(s) a bit more thoroughly!

[uncle_bob]

Hi

Another thing to check any time you set up one of these controllers: Is the temperature compensation number in "per degrees F" or the far more common "per degrees C". I have seen devices that happily switch the *display* units from C to F, but keep the other entries in C no matter what .....

Bob

[pteck]

Originally Posted by AirMiles

Yes. I just realized my temperature compensation setting was incorrect and changed it to -18mV. Six cells times -3mV

Here is a link to Trojan T105 charging parameters. https://www.trojanbattery.com/pdf/da...ata_Sheets.pdf

I could very well be wrong, but I'm not sure multiplying by 6 is the right interpretation.

The parameter is usually spec'd in units as 3mV/℃/2V

The controller knows the operating voltage. In our case, 12V. It's going to take that into consideration and multiply the 3mV/℃/2V within its own logic. These controllers typically also support 24V systems as well. So upon detection of that, it knows to compensate 3mV/℃ per every 2V of system voltage.

Much like the temperature part, it's the dependent variable based on operating conditions.

[pteck]

Originally Posted by uncle_bob

Note that normal bottled water likely is no different than what comes out of your tap at home in this regard. You are after something a bit different. Even water from an RO setup is not quite as good as distilled water. It's a *lot* better, but not quite the same thing.

Funny that you bring up reverse osmosis water. That's what I use as it's just easy and accessible.

It could be argued that RO water is purer than distilled in some qualities. I wouldn't sweat between using RO or distilled for the average flooded lead acid battery.

To your point, definitely not good to use regular bottled or tap which many times are indistinguishable depending on where one lives. It wouldn't be "healthy" water for batteries.

[AirMiles]

I

Originally Posted by pteck

I could very well be wrong, but I'm not sure multiplying by 6 is the right interpretation.

The parameter is usually spec'd in units as 3mV/℃/2V

The controller knows the operating voltage. In our case, 12V. It's going to take that into consideration and multiply the 3mV/℃/2V within its own logic. These controllers typically also support 24V systems as well. So upon detection of that, it knows to compensate 3mV/℃ per every 2V of system voltage.

Much like the temperature part, it's the dependent variable based on operating conditions.

You are right. The controller uses Celsius/Volt and the battery is stated in Fahrenheit/cell. So now I need to recalculate. Maybe I had it right the first time? I need someone better than me at this calculation to give me the right answer.

[AirMiles]

Originally Posted by AirMiles

You are right. The controller uses Celsius/Volt and the battery is stated in Fahrenheit/cell. So now I need to recalculate. Maybe I had it right the first time? I need someone better than me at this calculation to give me the right answer.

I still have the above statement wrong and it’s too late to edit. The controller uses “mV per degree Fahrenheit” and the battery is stated as “-3mV/cell/ degree Celsius”. There are six cells in the batteries. This calculation is above my pay grade!

Ok, I believe I figured it out! My original setting of -32.40 is probably correct if the formula is -3mV x 6 cells / .5555 = -32.40. The .5555 is to convert to Fahrenheit.

[uncle_bob]

Originally Posted by pteck

Funny that you bring up reverse osmosis water. That's what I use as it's just easy and accessible.

It could be argued that RO water is purer than distilled in some qualities. I wouldn't sweat between using RO or distilled for the average flooded lead acid battery.

To your point, definitely not good to use regular bottled or tap which many times are indistinguishable depending on where one lives. It wouldn't be "healthy" water for batteries.

Hi

Ummm .... errr .... not in terms of the conductive stuff that matters to a battery. Good clean water has less "crud" in it than your normal RO system output. An RO system is doing well at the 100K ohm level. Distilled water should be above a mega ohm "as delivered". Most plants I've seen run around the 4 megohm range when it goes into the bottle. The process water we used at work was around 18 mega ohms.

This assumes we are talking about a normal / simple single stage RO that runs a reasonable ratio of water in to water out. They don't have ion cartridges on them that you replace every month, though they may have a carbon cartridge.

Bob

[pteck]

Originally Posted by uncle_bob

Hi

Ummm .... errr .... not in terms of the conductive stuff that matters to a battery. Good clean water has less "crud" in it than your normal RO system output. An RO system is doing well at the 100K ohm level. Distilled water should be above a mega ohm "as delivered". Most plants I've seen run around the 4 megohm range when it goes into the bottle. The process water we used at work was around 18 mega ohms.

This assumes we are talking about a normal / simple single stage RO that runs a reasonable ratio of water in to water out. They don't have ion cartridges on them that you replace every month, though they may have a carbon cartridge.

Bob

Sure, if I want only the absolute best for my $90 batteries. For the minor ounces a year my batteries have taken, I'll admit I'm more than happy to compromise on many things and sometimes good enough (and RO is plenty good enough) will do.

We'll see what the new watering needs will be. Depending on that, I'll take your advice and keep a jug of distilled around.