Time to change batteries

Dave Angelini · August 2019

Marc has his own business in Texas. You would not be the first to have a shorter than normal life. Take his advice and try not to be guilty of anything when it comes to batteries. It is not rocket science. Have good Luck!

KenMorgan · August 2019

everything I see says undercharge. I have run AGM's for the last 8 years on my camper... and now on my cabin (1 year)

"with a Morningstar MPPT 60 controller that is set to a 2 hour absorb time Absorb Voltage is 28.6, Float voltage is 26.6V. Eq Voltage is 31.0 and set to Eq for 2 hours every 45 days. See my post on July 9 on this thread for more Equalization details."

28.6 is only 14.3VDC per battery, 26.6 is only 13.3 neither is high enough for a AGM solar battery bank I do not care what anybody in the industry says. I have "low end" batteries the entire time. none of the fancy stuff and mine are running fine and dandy 8+ years later by simply keeping the bulk and float charges high enough. even trojan and concorde have both raised their bulk and float voltages over the last 10 years... In some cases drastically. FYI I use the same morningstar controllers as well as a magnum inverter,its not the gear, its the charge cycle.

Coach Dad · September 2019

KenMorgan said:

everything I see says undercharge. I have run AGM's for the last 8 years on my camper... and now on my cabin (1 year)

"with a Morningstar MPPT 60 controller that is set to a 2 hour absorb time Absorb Voltage is 28.6, Float voltage is 26.6V. Eq Voltage is 31.0 and set to Eq for 2 hours every 45 days. See my post on July 9 on this thread for more Equalization details."

28.6 is only 14.3VDC per battery, 26.6 is only 13.3 neither is high enough for a AGM solar battery bank I do not care what anybody in the industry says. I have "low end" batteries the entire time. none of the fancy stuff and mine are running fine and dandy 8+ years later by simply keeping the bulk and float charges high enough. even trojan and concorde have both raised their bulk and float voltages over the last 10 years... In some cases drastically. FYI I use the same morningstar controllers as well as a magnum inverter,its not the gear, its the charge cycle.

Based on what you and others on here have said, I suspect you are right.
The sad reality is that I followed the Sun_Xtender manual recommendations. This is from the manual.

Image: https://us.v-cdn.net/6024911/uploads/editor/fw/p8tdafomfzfj.png

Surfpath · September 2019

I can't speak to the AGM's, but I can to the SPRE415's (L-16 REB's). My, pre-smart carbon, REB's are now 7 years old. They have been at a warmish avg of 81 degrees F, cycled between 100% and 65% SOC daily. I basically followed BB's advice in 2007 and hunted down 100% every day if possible. Only 4-5 times a year does bad weather makes this challenging.

However, I have been a little more gentle with them in old age. I have cut back absorb a tad (eg. from 2.2 hrs to 1.9hrs), EQ from 1.5 hrs to 1 hr. In other words, my 100% is a less aggressive 100%. There is no science to this, just an instinct. It probably makes little difference. Who knows.

I hope your new bank does well. I am hoping to re-battery in early 2020 with a new bank of SPRE415's. We'll see.

Coach Dad · September 2019

Surfpath said:

I can't speak to the AGM's, but I can to the SPRE415's (L-16 REB's). My, pre-smart carbon, REB's are now 7 years old. They have been at a warmish avg of 81 degrees F, cycled between 100% and 65% SOC daily. I basically followed BB's advice in 2007 and hunted down 100% every day if possible. Only 4-5 times a year does bad weather makes this challenging.

However, I have been a little more gentle with them in old age. I have cut back absorb a tad (eg. from 2.2 hrs to 1.9hrs), EQ from 1.5 hrs to 1 hr. In other words, my 100% is a less aggressive 100%. There is no science to this, just an instinct. It probably makes little difference. Who knows.

I hope your new bank does well. I am hoping to re-battery in early 2020 with a new bank of SPRE415's. We'll see.

That is great. Keep up the good work. My SPRE415's are running well. I'm doing a 2 hour daily absorb, and a scheduled 3 hour Equalize every 30 days (as recommended in the Trojan Users Guide). I'll be thrilled to get 7 years out of these if I do.

Dave Angelini · September 2019

Sure there is science to it! Especially easy with a hydrometer. Cutting back charge time on an old battery sounds to me like the wrong decision unless the SG is right.

You all should get 7 years and more if you manage loads and charge correctly. Not trying to be a snoot either. Good Luck!

softdown · September 2019

"My batteries (and system) can see temperatures from -15F to +95F."
Where is this?,

Heat shortens battery life significantly. With that range, a temperature sensor hooked to the charge controller would be mandatory.

Are the batteries outdoors? That would be quite a temperature range indoors. Can you dig a hole and keep the batteries a couple feet underground? I'd be working on the temperature. You had two expensive battery strings quit at least 50% earlier than expected.

We have a number of techies here that get caught up in esoteric theories and may overlook the basic importance of keeping batteries and electronics cool if possible. By the way, cooling and heating cycles will break electronic "solder type" connections over time. You want a stable environment. That is why electronics in motorhomes and campers like to quit before expected. Plus the bouncy/bouncy roads of course.

Marc K feels that equalizing should not be needed for the first 5 years. Another item to consider.

Coach Dad · September 2019

softdown said:

"My batteries (and system) can see temperatures from -15F to +95F."
Where is this?,

Heat shortens battery life significantly. With that range, a temperature sensor hooked to the charge controller would be mandatory.

Are the batteries outdoors? That would be quite a temperature range indoors. Can you dig a hole and keep the batteries a couple feet underground? I'd be working on the temperature. You had two expensive battery strings quit at least 50% earlier than expected.

We have a number of techies here that get caught up in esoteric theories and may overlook the basic importance of keeping batteries and electronics cool if possible. By the way, cooling and heating cycles will break electronic "solder type" connections over time. You want a stable environment. That is why electronics in motorhomes and campers like to quit before expected. Plus the bouncy/bouncy roads of course.

Marc K feels that equalizing should not be needed for the first 5 years. Another item to consider.

Thanks for your input. You are correct and I appreciate it.

My Cabin is in Adirondack Park in Northern New York. The Adirondacks is a harsh environment. We see LOTS of rain and LOTS of cloudy days through out the year. Our winter snow often piles up to over 5 feet. The temps in the Adirondacks range from +95F down to -15F. There are some weeks that never see the sun.

The batteries are in a vented battery box that is in a shed. The shed is not heated or cooled but also has plenty of ventilation and is in a shady spot. The shed and battery box help to shield the batteries a little from temp extremes. Since the batteries are in a battery box, their temps might range from +85F to +10F but the electronics which are hanging on the shed wall see close to the outside temps plus or minus a few degrees. I agree with you that electronics should be kept in a stable environment, but I don’t have that choice.

I don’t think putting the batteries into a hole in the ground would be very practical. The frost line goes pretty deep, and once the snow starts to fall, you’d have to shovel 5 feet of snow to find them. Also wonder how would the gasses be vented?

I can see that many people on here have a high opinion of Marc K when it comes to AGM batteries and I’m sure he knows his stuff. If I was going to use AGM’s again, I’d ask him some more specific and follow his advice. But I’m done with AGM’s and have switched to Flooded batteries.

I’ve set up my Morningstar MPPT Controller to do daily 2 hour absorb and a 3 hour equalize every 30 days on the flooded batteries. I’m following Trojan’s user manual. I’ll monitor that for a little while and adjust these settings if needed.

The nice thing about going to flooded batteries is that I can now verify the water levels and measure SG. This will allow me to make adjustments to my charging as needed. The bad thing about going to flooded batteries is that I will NOW HAVE TO monitor water levels and measure SG. (It’s a double edge sword)

I loved the “maintenance freedom” of AGM’s but but you pay the price for that freedom. AGM’s are a guessing game. Even the manufacturer doesn’t know if or how often to equalize (as demonstrated by the 3 user manual revisions that I detailed earlier in this thread.). You also can’t add water if they start to dry out.

Ralph Day · September 2019

The equation for the absorb time FLA batteries need (from Surrette):

0.42 x (20 hour C rate for your batteries) / amps you can deliver

For my S550 Surrette L16's: (.42 x 428ah) / 30a = 5.9 hours

2 hour absorbs just don't cut it for most of us.

Coach Dad · September 2019

Ralph Day said:

The equation for the absorb time FLA batteries need (from Surrette):

0.42 x (20 hour C rate for your batteries) / amps you can deliver

For my S550 Surrette L16's: (.42 x 428ah) / 30a = 5.9 hours

2 hour absorbs just don't cut it for most of us.

Thanks Ralph.
What does the 0.42 represent?
Using your equation. I "can deliver" 60 amps with my PV set up.
(0.42 x (20 hour C rate for your batteries) / amps you can deliver
0.42 x 750ah)/60A = 5.25 hrs

I verified my setting with Trojan Tech Support.
Also remember that the batteries are absorbing 2 hours every day that the sun comes out even though there is no electric usage Monday through Friday.

Estragon · September 2019

I'm also not sure about that formula. After the first couple of hours, I could likely keep my 350ah rated 48v bank at absorb voltage with just a couple of panels (~5a with no other loads). My setup terminates absorb at 3hrs, or when current required to hold Vabs drops to ~1% of bank capacity.

I wonder if the formula is more appropriate to (eg) an industrial application using a grid attached constant current charger.

mike95490 · September 2019

3 hrs EQ seems a bit harsh. I'd extend the daily absorb a bit instead, and only EQ if cells are not holding their SG.

papab · September 2019

@Marc Kurth

Can you review CoachDads post and comment on what he may have done wrong?

https://forum.solar-electric.com/discussion/comment/401412#Comment_401412

@Coach Dad

Are your charging voltages temperature compensated?

@kenmorgan

What 'low end' batteries are you using that you've had good luck with?

Dave Angelini · September 2019

mike95490 said:

3 hrs EQ seems a bit harsh. I'd extend the daily absorb a bit instead, and only EQ if cells are not holding their SG.

It depends on the make of battery. US battery does recommend 3 hours EQ on L16FLA.

I tell my clients that use them to find a pilot cell that seems to have the most difference and use that for when to terminate EQ, or just do what is recommended. Batteries are expendables and there is a tendency to overthink the basics of EQ.

softdown · September 2019

Nothing like beating a dead horse here. The batteries were replaced and he spent a lot of time coming up with a new charging regimen. I know everybody has good intentions but it confuses when so many opinions are proffered.

He is going with battery mfr recommendations and that is maybe hard to second guess. Though I think we will all agree that a Battery Temperature Sensor needs to be hooked up with a battery temp swing of -15F to 95F. If it was me I'd try to work on that. Says the guy with the 1650 pound forklift battery sitting next to the shed. Moving it could have killed me twice last time. Not worth the risk - big 24 volt forklift batteries are too easy to tip over in sand. "Do as we say, not as we do?"

Coach Dad · September 2019

softdown said:

Nothing like beating a dead horse here. The batteries were replaced and he spent a lot of time coming up with a new charging regimen. I know everybody has good intentions but it confuses when so many opinions are proffered.

He is going with battery mfr recommendations and that is maybe hard to second guess. Though I think we will all agree that a Battery Temperature Sensor needs to be hooked up with a battery temp swing of -15F to 95F.

Exactly correct. I don't mind seeing opinions but will still use manufactures (Trojan) recommendations. I've sent questions to Tech Support based on opinions given in the thread.
Yes I have 2 temp sensors on the batteries. 1 goes to the Charge Controller and 1 goes to the inverter/charger.

I think it is good to discuss this stuff, as a way to help people in the future with their setups.

softdown · September 2019

Huh - I have not heard of employing two temp sensors. We all know how the CC sensor works. I wonder how the inverter sensor works.

Estragon · September 2019

I also have a sensor hooked up to the inverter. It works the same as the controller RTS. My controllers don't speak to the inverters, so can't share temp data. If the were integrated, they probably could share a sensor.

IMHO, it's best to start with vendor charging specs unless there's a compelling reason not to. As the system gets used in a particular application though, some tweaking may be needed.

Coach Dad · September 2019

softdown said:

Huh - I have not heard of employing two temp sensors. We all know how the CC sensor works. I wonder how the inverter sensor works.

Here are Temp sensor descriptions from both manuals. Hope this helps.

Image: https://us.v-cdn.net/6024911/uploads/editor/fj/rc3skptj71ps.jpg

Dave Angelini · September 2019

One of the problems I see with sensors all the time is the person who installed the sensor did not finish the job by calibrating the battery spec to the electronics. The second is the sensor is installed and the default temp was not updated to the bts. Pretty basic power system configuration.

Image: https://us.v-cdn.net/6024911/uploads/editor/w4/s16ms8vjdud9.png

mike95490 · September 2019

Dave Angelini said:

One of the problems I see with sensors all the time is the person who installed the sensor did not finish the job by calibrating the battery spec to the electronics. The second is the sensor is installed and the default temp was not updated to the bts. Pretty basic power system configuration.

You need to start a Wall of Shame with all the dumb mistakes.

ElectricLove · September 2019

I think I know what is the problem with your batteries lasting a long time... First to qualify, I've seen this exact problem on a large scale from a corporate level; I was with a company and the company was selling AGM batteries for a long time and started analyzing the failures that were happening prematurely and generating large warranty claims (systems we installed would have 40, 80, 400 large AGM batteries in them). It was concerning and after all of the analysis we finally realized that AGM batteries should NOT be equalize charged.

Equalize is an old-school and rough method for balancing batteries, it is only effective with Flooded Lead Acid batteries which can boil off some of their water content during the equalization process. An AGM battery can't do that, Equalize means "over-charging" and over-charging means permanent damage to the battery structure. If you are concerned with battery balance (you have 4 in series, so you really don't need to be as long as you install them together and balance them prior to install and then periodically check the two to see that they are still equal in voltage) you can add a balancing device that will keep the 4 series batteries balanced.

Honestly, I am 99% certain you are prematurely killing your batteries by having not removed the Equalize mode (or if you can't set the Equalize voltage to be same as fully-charged).

Also, if you want batteries that last a very long time (and temperatures you reported are OK) look for Lithium Iron Phosphate. But again don't ever Equalize them as it will only destroy them in time.

BB. · September 2019

What is an "EQ Charge" in your experience? Typically, from what I have read, an EQ Charge for AGM is simply holding the setpoint for Absorb (around 14.4 volts for a 12 volt bank) for something like 8 hours every 6 months.

-Bill

Marc Kurth · September 2019

Bill, yes I see that number thrown out a lot.

When used as a corrective measure for undercharging damage, Concorde uses 15.5v for 8 hours. They call it "Conditioning" to reduce confusion. Yes, it is slightly destructive so it should be used judiciously, I have extended the operating life of hundreds of batteries with one to two 8 hour runs at 15.5v. It always depends upon how long the sulfates have been allowed to accumulate. Concorde has recently been recommending a "mild EQ" of 2-4 hours every few weeks, for systems with chronic undercharging problems. It should not be done unless it is needed.

Keep in mind that the batteries must be monitored for overall temperature, localized hot spots and excessive off gassing.

I'm sure that some people will gasp, but we often go to 3v per cell as part of the deep discharge 15-20 hour recovery process. Remember that quite often, the goal is simply to extend the usable life of already abused/damaged batteries.

Marc

softdown · September 2019

The fact that many manufacturers have changed their mind so many times gives some pause for reflection. It would be of some interest if a clear battery case was possible.

Marc Kurth · September 2019

softdown said:

The fact that many manufacturers have changed their mind so many times gives some pause for reflection........

In the case of Concorde, I saw a reaction to the internet megaphone screaming that "the sky will fall of you overcharge an AGM." The result has been people consistently abusing their batteries by undercharging. There really wasn't a change of mind - it is a self defense posture to suggest that mild equalization is required when you abuse the batteries with undercharging. Their tech manuals have always recommended conditioning after abuse, at least for the last 12 years that I have been deeply involved with them. I am currently replacing a lot of batteries that I originally sold in the 2009 and 2010 time range - most of which were never equalized. I work hard to educate my customers.

The only two changes that I can recall was a slight narrowing of the required charge voltages and the suggestion that their batteries should be mounted in a standard vertical orientation for best performance - as opposed to "any orientation except with vent caps down."

Marc

BB. · September 2019

Marc,

I know that Concorde has that "high voltage" corrective EQ"--And that (at least so far), it has not be suggested for other brands of AGM batteries. And the corrective EQ (as I understand) is only suggested when the battery has lost significant capacity (loss 20% or more?). "Mild EQ" is what?

What is the voltage/time recommended for the standard charging regime (day in--day out/month in--day out)? Does it change between brands/models of AGMs on solar power systems (limited hours of sun per day, less than daily "100% recharging")?

-Bill

littleharbor2 · September 2019

If you can see, or can enlarge the photo, These CSB AGM's recommend a cycle duty charge voltage of up to 15 volts. Are they getting better at recombining the hydrogen gas? Stronger vent valves?

Image: https://us.v-cdn.net/6024911/uploads/editor/lu/avoqs6on6pn8.jpg

Dave Angelini · September 2019

I think they are in the business of selling batteries.
If the user does not know how to set end amps and voltage they are repeat customers before their time.

mvas · September 2019

softdown said:

The fact that many manufacturers have changed their mind so many times gives some pause for reflection. It would be of some interest if a clear battery case was possible.

All deep cycle Lead Acid batteries, have always required equalization - even AGM batteries.
This has never been refuted, by any AGM battery manufacturer.

The problem is ... the "maintenance-free" battery was originally designed for the brain-dead consumer
The catch-22 is ... equalizing an AGM battery, to maximize its cycles / life, requires skill / knowledge

No two batteries are identical
No two battery chargers are identical
No two discharging applications are identical

Lead Acid battery technology is evolving.

Given these facts ...
It is irrational for you to assume that - one generic set of charging parameters is best for everyone and should never change.
Life Line has helped owners design a custom set of bulk / absorb / equalize / float parameters, optimized for their environment.

Time to change batteries

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