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Author Topic: Battery curves - Converter vs Solar?  (Read 492 times)

Frank B

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Battery curves - Converter vs Solar?
« on: July 13, 2017, 08:53:01 PM »
I am running into all kinds of wildly different information on optimum charging voltages and curves for flooded cell GC-2 batteries.

Interstate has figures of 14.4 volts bulk, 15.3 for absorb, 13.4 for float, and 15.6 for equalize (for a pair in series).

Progressive Dynamics has settings on their Charge Wizard of 14.4, 13.6, 13.2, and 14.4 for the same steps.

The shore power PD converter is WAY low compared to what is being asked by a major battery manufacturer.

Solar controllers are often programmable, and with a high enough voltage solar array, one can program in the higher figures that Interstate is suggesting.  And Interstate is not the only company suggesting the higher figures than what the reputable Progressive Dynamics converters offer.

So, who is right?

And, if that were not enough, unless you have a very long day, getting a bank of batteries up to 15.3 volts for the absorb stage with solar may be quite a trick.

I was surprised to find so little discussion of this topic in the forum, and such wildly differing information on the web.  Can anyone make any sense of this?  Or is it that it just doesn't matter that much?

Frank.
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Kevin Means

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Re: Battery curves - Converter vs Solar?
« Reply #1 on: July 14, 2017, 03:23:06 AM »
Hmmm... well some of those numbers surprise me. Interstate's recommendation for 15.3 volts for the Absorption stage seems high, while PD's recommendation for 14.4 volts for Equalization seems low. I've always read that 15.3 to 15.5 are pretty standard equalization voltages. I wonder if those numbers reflect the fact that you're using 6 volt golf cart batteries - mine are all 12 volt.

I suspect that PD is recommending only 14.4 volts for Equalization, because they're also recommending that they be equalized every 21 hours. That's fairly frequent, and seems excessive, but maybe they're saying more frequent equalization requires lower equalization voltage.

With as much solar as you've got, I suspect that your batteries aren't going to be discharged very deeply, nor as often as maybe they once were, and the solar will charge them back up sooner after they are discharged. All of those things will really help minimize sulfation - the biggest battery killer of all. Based on that, maybe the milder settings that PD recommends would be the way to go.

I'd recommend PMing Gary Brinck if he doesn't see this thread. He's got a lot of battery knowledge. I'm runng strictly AGMs and they're a somewhat different animal when it comes to charging and equalization.

Kev 
« Last Edit: July 14, 2017, 03:35:53 AM by Kevin Means »
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sadixon49

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Re: Battery curves - Converter vs Solar?
« Reply #2 on: July 14, 2017, 06:53:04 AM »
I would almost bet that Interstates bulk and absorption #s are transposed. 15.3 sounds right for bulk and 14.4 is close for absorption. If you read HandyBobs solar pages, you will find that his biggest gripe is that the battery charger guys all seem to be more concerned with not "burning up" a battery, and less concerned about actually getting it completely recharged. My best advice, find a converter that will allow you to adjust the settings, and set them to the specs that your battery manufacturer recommends.
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Gary RV_Wizard

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Re: Battery curves - Converter vs Solar?
« Reply #3 on: July 14, 2017, 07:25:49 AM »
For any given battery, I would have to assume that the battery manufacturer knows the optimum charge parameters for his particular battery chemistry. However, those will be for a "laboratory environment", with new batteries, carefully controlled time periods, clean wire connections, and a battery isolated from any loads.  That is rarely the case for a battery installed in an RV or vehicle, so the manufacturers of converter/chargers have to deal with the real world, where batteries are old, cells are low on electrolyte, have corroded terminals, usually have at least a small power draw active, and may sit on the charge cycle for weeks. All these effect the voltage seen at the charge terminals, sometimes dramatically so.   And yes, these days they are extremely concerned about damaging your batteries, for which we should thank them! Back in the day that wasn't so true and "boiling a battery" was all too common.
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kdbgoat

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Re: Battery curves - Converter vs Solar?
« Reply #4 on: July 14, 2017, 07:33:36 AM »
And try to use a charger that has temperature compensation, and get the sensor to do so.
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Gary RV_Wizard

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Re: Battery curves - Converter vs Solar?
« Reply #5 on: July 14, 2017, 07:41:23 AM »
Some further discussion of multi-stage charging:

Voltage is not a very significant factor during the bulk charge phase. By definition, bulk charge is constant current (amps) and the voltage need only be high enough to push those amps into the battery. The battery voltage has to be low (battery substantially discharged) to even get into bulk charge mode, so a high voltage should not be necessary. In bulk charge stage, the voltage produced by the charger varies as needed to sustain a constant charge current, so there can be no single voltage for bulk stage.

When the charger shifts to absorption phase it has to maintain a voltage high enough so that the battery can "absorb" as much current as it wants. This phase is defined as constant voltage with variable current. Each battery probably has an optimal voltage for that, but the difference from one brand of flooded cell to another is probably minimal.  Battery engineers make value judgments about charge time vs battery longevity, so small differences are likely.  However, AGM vs Gel vs Flooded may vary a tenth volt or so because the battery chemistry differs a bit in each type.

Temperature compensation is a significant factor and chargers that do not have temperature sensors have to be a bit more cautious about charging rates. Voltage and amp rates that are fine at 75 degrees may be damaging or inadequate at 95 or 35.
Gary
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Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #6 on: July 14, 2017, 08:49:49 AM »
Gary:

The voltages and settings on the PD converter I cannot change.  I just found them pretty conservative.  However, as you say, given that it may get left on for months, I can understand that.

The Outback FM80 is programmable, and its default absorb voltage is 14.4.  The FM80 uses the voltage to determine when to go into absorb stage, which appears to be common with solar controllers.  When the array and controller are able to get it above the absorb set point, then it switches to absorb mode, with a corresponding drop in the current being supplied to the battery bank.  The Outback FM80 then uses a programmable  timer to determine how long to keep it in absorb.

The issue I was running into yesterday was a result of my efforts to 'test' the system.  In doing so, I inadvertently ran the battery bank down to 50% overnight.  I waited until noon the next day to switch on the solar array, expecting to get 'maximum performance' from the solar.  However, with the 14.4 volt 'switch' to absorb stage, the powerful controller and large array at noon on a clear day, the charge voltage topped 14.4 volts in about 10 seconds.  This  caused an immediate switch to absorb mode for the 1 hour default on the timer, and then into 'float'.  As you can appreciate, the batteries got hardly any charge at all.

When scouring the web, I came across the higher 15.3 volt absorb voltage suggestion, so programmed the controller for that.  Then it wouldn't come OUT of bulk, averaging around 45 amps until the sun began to set.  In the somewhat less than half day left after reprogramming the absorb set point, it never made it to absorb, staying around 14.6 to 14.8 volts charging in bulk mode.

It  seems that, with the Outback FM80,  the default 14.4 volt 'switch' to the absorb stage is too low (for a pair of GC-2's, at least), but that 15.3 may be a tad high.

As to manufacturer recommendations, I have 6 NAPA 'generic' GC2-110 batteries.  Going to the NAPA site and looking up the tech specs on these batteries shows a PDF from East Penn, who I assume is the OEM. 

http://www.eastpenncanada.com/solar-flooded.html


I cannot find recommended voltages for their product, but I do have an email in to them requesting that information.  However, as East Penn seems to be OEM for a whole slew of brand names, I doubt that there are much in the way of differences between the majority of GC-2's on the market.


So, while my PD charger was designed to use a deep cycle 12V battery, I have been using 6 V GC-2's.  That alone may be why the lower charge voltage figures for the PD converter.


My real question (after all this ado) is where I should set the absorb voltage on my solar controller.  I have already increased the absorb timer setting from the default 1 hour to 2 hours (can be set to 24 hrs, though pointless on a solar setup).  However, while the default 14.4 volts was woefully low, I am beginning to wonder if the 15.3 is a bit high, and should be reduced to 15 or so.  However, this is a 'seat of the pants' figure.


Thanks for any further insight you can offer.

Frank.


PS:

OK, it made it out of bulk around 11 AM this morning, and is now at the absorb voltage I set of 15.3 volts.  However, I am getting some bubbling in the batteries, though they are not significantly above ambient temperature.

IIUC, a bit of bubbling is desirable in an equalization cycle, but probably not in the absorb stage, as it is just generating gas.  The PD converter NEVER bubbled the batteries -- not even in its 'equalization' cycle.

Unless anyone can suggest a reason to the contrary, I think I'm going to put the absorb 'switch' voltage to 15 to begin with and monitor if this stops the bubbling, or maybe even down to 14.8.  I think what I am looking for is JUST high enough to prevent the solar controller from going immediately from bulk to the absorb stage.  15.3 may be a more appropriate equalizing voltage.

Frank.
« Last Edit: July 14, 2017, 12:50:53 PM by Frank B »
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Gary RV_Wizard

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Re: Battery curves - Converter vs Solar?
« Reply #7 on: July 14, 2017, 12:50:21 PM »
Quote
I inadvertently ran the battery bank down to 50% overnight.  I waited until noon the next day to switch on the solar array, expecting to get 'maximum performance' from the solar.  However, with the 14.4 volt 'switch' to absorb stage, the powerful controller and large array at noon on a clear day, the charge voltage topped 14.4 volts in about 10 seconds.  This  caused an immediate switch to absorb mode for the 1 hour default on the timer, and then into 'float'.  As you can appreciate, the batteries got hardly any charge at all.

Actually, I do not appreciate that at all. It does not totally surprise me that it stayed in Absorption mode from the 50% SOC level, but that mode should charge the batteries quite well. By definition, the batteries are accepting all the charge amperage they can comfortably take in that stage, and 14.4v is plenty to push amps through. Lots of chargers, including typical vehicle alternators, run at 14.4v 90+% of the time.   If your batteries failed to charge further in 14.4v absorption mode, I think you have some other problem.

I'm thinking that a pair of GC2's can only accept 20-25A @ 14.4v. If you had all 6 connected up, it would be more like 60-80A.
« Last Edit: July 14, 2017, 12:55:09 PM by Gary RV_Wizard »
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Paul & Ann

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Re: Battery curves - Converter vs Solar?
« Reply #8 on: July 14, 2017, 12:59:12 PM »
The batteries you have are apparently made by Excide and are the same as the NAPA branded 8144, but I couldnt find the charging specs for them.

I believe I would go with 14.4 bulk charge rate, and 14.7 absorption rate, until I found the correct charging profile.

Also, it is true for the Interstate GC2 series of batteries they recommend  14.4 bulk, and 15.3 for absorption.
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Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #9 on: July 14, 2017, 01:05:26 PM »
Gary:

Quote
If your batteries failed to charge further in 14.4v absorption mode, I think you have some other problem.

Yes.  :)  I think that is what I am trying to figure out.  So, please teach me!

I have been told not to bring the batteries below 50% of charge, which according to tables I have seen, would be just over 12.0 V measured at the batteries alone.  Am I right so far?

I had assumed that 'bulk' would be the order of the day at that level of discharge, somewhere up to about 75% of charge, or about 12.4 volts at the batteries alone.

Are you saying that at 50% discharge, my solar controller should never use the bulk setting?  If so, then all is well with the default settings.  Perhaps my assumptions are wrong.

It may be that I only need to increase the timed 'absorb' cycle, putting it up from 1 hour to maybe 3 or more?  Because once the absorb timer runs out, charged or not, the controller goes into 'float'.

I am here to learn.  :-)

Frank.
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Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #10 on: July 14, 2017, 02:34:01 PM »
Paul:

Quote
I believe I would go with 14.4 bulk charge rate, and 14.7 absorption rate, until I found the correct charging profile.

IIUC, the bulk voltage on my solar controller is not adjustable.  The controller controls that.  :)  The controller appears to give the batteries all the array can produce at as much voltage as the controller can muster -- up until the battery bank stops pulling the input voltage down.  Once the controller is ABLE to get the charge voltage up over the absorb voltage setting, THEN it switches into the absorb portion of the cycle - which is controlled  with a timer.

In my case, the controller with the array that it has to work with was able to push my 50% dead battery bank up over 14.4 volts in just a few seconds, whereupon it dropped into the absorb cycle.  I saw that as a problem.  Perhaps not.  I am waiting for more input from Gary on that.  My whole set of assumptions may be wrong.

In any case, with 15.3 causing gassing in the batteries, I did as you suggested and backed off the absorb voltage to 14.7.  I have it set to hold that for 2 hours.  Then it will drop into float (13.4, I think) for the rest of the day.

Still willing to learn!

Thanks.

Frank.
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Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #11 on: July 14, 2017, 02:37:39 PM »
Gary:

Quote
I'm thinking that a pair of GC2's can only accept 20-25A @ 14.4v. If you had all 6 connected up, it would be more like 60-80A.

Yes.  All 6 are connected.  I was expecting closer to 50 amps, which is about the most I think I can expect with flat mounted panels at this lattitude.  I was trying to see what I needed to do to achieve that.

Frank.
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Gary RV_Wizard

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Re: Battery curves - Converter vs Solar?
« Reply #12 on: July 15, 2017, 01:19:12 PM »
You are looking for black & white answers and fixed numbers where gray and variable is the order of the day.

Quote
I have been told not to bring the batteries below 50% of charge, which according to tables I have seen, would be just over 12.0 V measured at the batteries alone.  Am I right so far?

Pretty much, but neither the 50% nor the 12.0v is an absolute. Consider them rules of thumb, not concrete facts. There is nothing magic about the 50% level - a lead-acid battery's ability to be recharged deteriorates as the charge percentage goes down  At 70% charge it has already lost a little, and more is lost as the SOC percentage goes down further.  And it's cumulative small deterioration, not just a one-time thing when it hits 50%, so its how often you discharge as well as how far. 

As for the 12.0v (plus or minus a few hundredths), that's text book for a new battery with zero load. Age and previous discharges can alter that a bit, and the condition of the connections to the battery affect the accuracy of the measurement as well. Trying to make judgements concerning a 0.1v difference in an RV system is an exercise in futility (my opinion - others probably disagree).


Quote
I had assumed that 'bulk' would be the order of the day at that level of discharge, somewhere up to about 75% of charge, or about 12.4 volts at the batteries alone.

Are you saying that at 50% discharge, my solar controller should never use the bulk setting?  If so, then all is well with the default settings.  Perhaps my assumptions are wrong.

I'm no charging system design engineer, but no charge controller I've used works quite that simply. Nor do I know just how your controller determines when to use which mode.  It is juggling voltages and current flows, trying to guess battery state.  I doubt if the engineers ever tried to relate their parameters to SOC percentage.

Does your controller have a battery bank size parameter, e.g. total AH or similar? That affects the charge algorithm because more AH means it can accept more charging amps. some controllers use a one-size-fits-all algorithm while others try to adjust for the battery capacity (usually the total number of AH).

I can tell you that my Xantrex RV2500 3-stage charger rarely entered bulk mode and never stayed long if it did. If the SOC got down to 30%-40% I would see Bulk flash up, but absorption was quick to arrive. I never learned why, but it was never a problem either.  My 380 AH battery bank sucked a lot of amps at absorption rates and quickly got back to Float (13.6v in that charger).  When the SOC is low, any positive voltage at all moves a lot of amps because battery internal resistance is extremely low. If the amps don't flow, than the resistance is higher than it should be, either because of a bad connection or an internal high resistance between plates. One slightly bad battery can blow a sophisticated charger out of the water and cause it to make bad decisions.

You need to talk to the charge controller tech support people to learn exactly what their charger should be doing under any given set of circumstances, but you will probably need more than just rough voltage levels. A quality shunt ammeter is a key tool to know what is really happening.
« Last Edit: July 15, 2017, 01:26:14 PM by Gary RV_Wizard »
Gary
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Gary RV_Wizard

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Re: Battery curves - Converter vs Solar?
« Reply #13 on: July 15, 2017, 01:28:44 PM »
LOL! Far too many words in the previous post.  Makes my head hurt to write or read them!  Don't try to overthink these things, cause an RV is not a laboratory and conditions are neither perfect nor immutable.
Gary
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Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #14 on: July 15, 2017, 06:41:40 PM »
Dear Gary:

Quote
LOL! Far too many words in the previous post.  Makes my head hurt to write or read them!  Don't try to overthink these things,

Nope.  Just what I needed!

Quote
cause an RV is not a laboratory and conditions are neither perfect nor immutable. Trying to make judgements concerning a 0.1v difference in an RV system is an exercise in futility

Wisdom distilled.

Quote
Does your controller have a battery bank size parameter, e.g. total AH or similar?

Not that I am aware of.  But this is a new machine to me.  Input from other members here that know the Outback FM80 better are welcome.

Quote
I can tell you that my Xantrex RV2500 3-stage charger rarely entered bulk mode and never stayed long if it did.

What I needed to know.  My assumptions seem to be wrong.  I was assuming that I would see figures similar to what Kevin Means has seen, seeing as how his system and mine are somewhat similar.   I'll have to check with him as to what the circumstances were when he saw north of 50 amps.

Quote
If the SOC got down to 30%-40% I would see Bulk flash up, but absorption was quick to arrive. I never learned why, but it was never a problem either.

Again, what I needed to know.  But you may take flak for admitting that you let your batteries get that low!  ;D

Quote
My 380 AH battery bank sucked a lot of amps at absorption rates and quickly got back to Float

As noted earlier, the Outback FM80 absorption period is just a timer, and that is user programmable.  Likely a consequence of the fact that shore power converters always have full input power to work with, and solar controllers don't.  This may be the parameter that I will need to watch to both get a full charge, yet not 'boil' the batteries either.

Quote
When the SOC is low, any positive voltage at all moves a lot of amps because battery internal resistance is extremely low.

That is why I was expecting in excess of 50 amps with the setup I have with the bank down to 50%.  Didn't happen.  When it got close to 46 amps (and reached the 14.4 volt default set point of the controller), the controller switched to the current limited absorb stage.  Even then I got about 36 amps or so, which went down with time.  But never the 50+ amps I should have been able to achieve.

Quote
If the amps don't flow, than the resistance is higher than it should be, either because of a bad connection or an internal high resistance between plates. One slightly bad battery can blow a sophisticated charger out of the water and cause it to make bad decisions.

Something I need to look at.  I am using the trailer's own wiring between the onboard PD shore power converter (to which I have paralleled the Outback solar controller), and the battery bank.  #6 as near as I can tell, over about 20 feet.  Maybe not enough?  Dunno.

Quote
You need to talk to the charge controller tech support people to learn exactly what their charger should be doing under any given set of circumstances, but you will probably need more than just rough voltage levels. A quality shunt ammeter is a key tool to know what is really happening.

I don't think I care that much.  I just want to keep my battery bank charged when boondocking in the winter in Arizona and SoCal.  While it would have been nice to beat Kevin's figures for 'bragging rights' ( ;D ), I have not paid nearly as much attention to detail as Kevin has.  In the final analysis, it really doesn't matter that much to me anyway.  If the end result is no more running the generator, then that is all I want.  And Kevin can keep his crown.   ;D

I do very much appreciate the time and thought expended on your answer to this question.

And I publicly thank Kevin Means for his kind help and guidance during this project.

This forum continues to be a wealth of good advice and information.  I still have it linked on the opening page of my browsers as the CompuServe RV Forum.  Thats how far back I go.   :)

Time for me to make another contribution toward expenses.   ;)
 
Thanks all!

Frank.
« Last Edit: July 15, 2017, 06:54:42 PM by Frank B »
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Kevin Means

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Re: Battery curves - Converter vs Solar?
« Reply #15 on: July 16, 2017, 02:46:32 AM »
Frank, the highest output I've ever seen was just over 50 amps at the end of last May. That's what I've actually seen. It's entirely possible that we've gotten more than that, but I'd have to download the log files from the Outback or the Trimetric to check. I've never done that before and honestly, I'm not too interested in doing so. On sunny days, we routinely see 40 to 45 amps from Feb to May with the panels tilted directly toward the sun.

A couple things... I used quality thick gauge wire throughout my entire system, and I'm convinced it makes a difference. I've also only got about a 4 foot run from the controller to the batteries with 2 gauge wire. There's no measurable loss there.

And remember, temperature has a huge affect on the output of solar panels. Panels are rated using 77 deg F (25C) but for every degree above 25C, there's more than a 1% reduction in output. One problem with roof-mounted (flat) panels is the lack of airflow under/around the panels. They're an average of 20 deg C warmer than ambient air. That's significant. That's another reason why tilting them is beneficial - it gets them away from the roof, into cooler air. Here's an article about it. It's about home solar, but the issue is the same.  http://homeguides.sfgate.com/effects-temperature-solar-panel-power-production-79764.html

You said you've been having some pretty warm weather up there, so as conditions improve, you'll likely see more output. And with your relatively low consumption, I doubt you're going to be disappointed with your system.

Kev

By the way, here's a YouTube video of a couple who has the same system we have - six 160 watt Grape panels with an FM80 controller. Watch how tilting them dramatically improves their output. It's the same output we see - both before and after we started tilting our panels.   https://www.google.com/url?q=https://www.youtube.com/watch%3Fv%3DG01A51L-5Vc&sa=U&ved=0ahUKEwjckPCkqY3VAhUnsFQKHQRcDT4QtwIIIDAC&usg=AFQjCNGoB1NZ-EZWFkk6J0GcWgp41i0ZNQ
« Last Edit: July 19, 2017, 11:56:42 AM by Kevin Means »
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Lakeside, California

Gary RV_Wizard

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Re: Battery curves - Converter vs Solar?
« Reply #16 on: July 16, 2017, 09:59:55 AM »
I see no reason why you might not see 40-50A in absorption mode. My Xantrex would do low 40's.

Quote
But you may take flak for admitting that you let your batteries get that low!
Yeah, I know, but I'm not a purist.  And the batteries were AGMs, which hold up better under deep discharge than flooded (more charge cycles).   It's important to understand that deeper discharging has a cost penalty, but the distinction between 55% and 45% is not crucial. If the batteries are down to 49% when I wake up in the morning, I still turn the coffeemaker on. There are priorities, ya know!

My Trojan AGMs lasted 8 years, but for the last 2 years they were down to about 60% of their original AH capacity. I would have replaced them at 6 years if we boondocked more, but they were ok for just travel time.
« Last Edit: July 16, 2017, 10:25:54 AM by Gary RV_Wizard »
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Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #17 on: July 25, 2017, 04:20:08 PM »
Kevin:


Quote
A couple things... I used quality thick gauge wire throughout my entire system, and I'm convinced it makes a difference. I've also only got about a 4 foot run from the controller to the batteries with 2 gauge wire. There's no measurable loss there.


I agree heartily. At 12v, there is no substitute for a lot of thick copper.  And this is the attention to detail that you have put in your system that I was referring to earlier. My choices were more a question of practicality and ease of installation. Rewiring my trailer with heavier wire from converter to batteries would be a really big job. I don't think I care that much. :-)  Maybe one day if I ever decide to move my battery bank further aft in the trailer, then I will consider that.


Thank you again so much for all of your help and encouragement!


Frank.
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Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #18 on: July 25, 2017, 05:46:48 PM »
Gary:

Quote
It's important to understand that deeper discharging has a cost penalty, but the distinction between 55% and 45% is not crucial. If the batteries are down to 49% when I wake up in the morning, I still turn the coffeemaker on. There are priorities, ya know!

 :) :D ;D

Yep!  Glad that someone with your experience agrees with me!  I hesitate to post here sometimes because of the purists that keep telling me how wrong I am.   ;D

I think I may deliberately run them down to below 50% just to see what my new solar system does with them.  I got to 46 amps input before the solar controller flipped from bulk to absorb mode.  However, this can happen, I am told, if the batteries are somewhat sulphated, which is entirely possible with my 3 year old flooded cells using only the conservative PM converter to keep them charged.

I may also have to look into more of the programming capabilities of this Outback FM80 solar controller.  IIUC, absorb mode is simply timed -- unless you put an amperage limit on it.  I think that if I put a higher amp limit on it (I think default is 0 amps), then it will kick into float earlier. 

I am finding that a 1 hour absorb time (default) when the batteries are already almost fully charged tends to make them gas at 14.4V, which is the default absorb voltage.  I have a certain amount of 'idle current' that comes out of the system because of fridge, Wifi repeater, cell booster, and so on, so the charge current into the batteries never gets to zero amps in absorb. There is a constant drain, so only the timer on the absorb mode controls how long it stays at 14.4 V.  Maybe setting the absorb current limit to 5 amps or so will cause it to go into float before they start gassing.  It seems that 'float' mode (13.6 v) will provide the extra current needed for 'idling' while the sun is up.  After that, tomorrow is another day when the controller starts again at 'zero' in assessing the condition of the battery bank, and its needs.  And it looks like I have ample solar capacity to 'catch up' the next day.

I'll also have to do a cost analysis of AGM's vs flooded cells, and see whether it is worth my while to spend more for the AGM's.

Thanks again for the input!

Frank.
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

Gary RV_Wizard

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Re: Battery curves - Converter vs Solar?
« Reply #19 on: July 26, 2017, 11:14:10 AM »
Quote
I hesitate to post here sometimes because of the purists that keep telling me how wrong I am.   ;D

Happens all the time, usually by well-meaning people who heard a "rule of thumb" second hand and didn't realize it's  "guidance" rather than a hard & fast law. Many practices are possible if you know what you are doing and pay good attention to operating status. The same thing may yield poor results or even be dangerous if done by someone who lacks skills and knowledge.  It's like those demonstrations you see on TV that say "don't try this at home".
Gary
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Summers: Black Mountain, NC
Home: Ocala National Forest, FL

AStravelers

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Re: Battery curves - Converter vs Solar?
« Reply #20 on: July 27, 2017, 08:46:25 AM »

By the way, here's a YouTube video of a couple who has the same system we have - six 160 watt Grape panels with an FM80 controller. Watch how tilting them dramatically improves their output. It's the same output we see - both before and after we started tilting our panels.   https://www.google.com/url?q=https://www.youtube.com/watch%3Fv%3DG01A51L-5Vc&sa=U&ved=0ahUKEwjckPCkqY3VAhUnsFQKHQRcDT4QtwIIIDAC&usg=AFQjCNGoB1NZ-EZWFkk6J0GcWgp41i0ZNQ
Everyone should watch the above video to see and excellent example of the problems with wiring several panels in series.  The RV in the video has all 6 of the panels wired in series.  The total amps from all 6 panels at the start of the video is about 37amps.  As they tilt each panel there is almost no increase in output until they tilt the last panel.  Then the output jumps from about 38 amps to 51 amps.  This also shows the affects of shading on panels in series. 
Al & Sharon
2006 Winnebago Sightseer 29R
2009 Chevy Colorado 4X4

http://downtheroadaroundthebend.blogspot.com/

Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #21 on: August 01, 2017, 04:07:52 PM »
Aha!!  One of the major reasons that I went for high-voltage residential panels! You don't have to put them in series. ;D


And, just one look at the hassle involved in tilting those panels, and I'm out!  Yeah, big roof with many flat mounted panels is a much easier way to go!  Just cover the whole stinkin' roof with panels, and then sit on the gro 89und with a cold drink in your hand!  ;) :D ;D


That video, and the other one that followed it with regards to running an air conditioner off the batteries gets me thinking. I may be able to run the air conditioner just off solar if I use a soft start device on my low capacity air conditioner.  Not that one needs an air conditioner in the winter in Arizona, but it would be nice to have the ability if one gets a particularly hot day. 


So, does anyone know where I can get a soft start device for a low capacity Coleman Mach air conditioner somewhere in the neighborhood of 1300 Watts?  With a soft start device, I may even be able to run it off a 2000 watt Honda generator. It is the surge current for startup that is the killer on a 2K Honda generator.


Frank
« Last Edit: August 01, 2017, 04:13:26 PM by Frank B »
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #22 on: August 03, 2017, 04:18:42 PM »
Kevin:


I wonder if those numbers reflect the fact that you're using 6 volt golf cart batteries - mine are all 12 volt.[/size]
Quote
[/size]

[/size]
[/size]You mean, you have 8 x 12v batteries! Now, THAT is a battery bank!
[/size]
[/size]Frank
Linux:  Free, open, elegant.
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Kevin Means

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Re: Battery curves - Converter vs Solar?
« Reply #23 on: August 04, 2017, 11:27:49 AM »
Frank... that last post didn't come across well - couldn't read the tiny font.

Kev
2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ or an Acura MDX
RVI Brake 2, Minder TM-66 TPMS, 970 watts of solar
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Lakeside, California

Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #24 on: August 05, 2017, 09:04:12 AM »
Kevin:

Quote
Frank... that last post didn't come across well - couldn't read the tiny font.

I have to read those on a phone or tablet where I can zoom the view.

Yeah, the forum software does that every so often, and it seems no one knows why.  One of the sysops usually fixes posts like that, but I guess they missed this one.  I'll try again.  Here is what I posted:





Quote
I wonder if those numbers reflect the fact that you're using 6 volt golf cart batteries - mine are all 12 volt.

You mean, you have 8 x 12v batteries! Now, THAT is a battery bank!

Frank.
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

Gary RV_Wizard

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Re: Battery curves - Converter vs Solar?
« Reply #25 on: August 06, 2017, 09:46:21 AM »
Quote
So, does anyone know where I can get a soft start device for a low capacity Coleman Mach air conditioner somewhere in the neighborhood of 1300 Watts?

Take a look at yours. The Coleman Mach's on my previous rig already had soft start capacitors.  They also were rated at 1400 watts (13.5k btu heat pumps).  I think you need to get down to the smaller 8000 btu a/c units to get much under that.

This previous thread addresses those kits:
http://www.rvforum.net/SMF_forum/index.php?topic=97677.0

And here is a kit if you need one:
https://www.microair.net/products/easystart-364-3-ton-single-phase-soft-starter-for-air-conditioners?variant=30176048267
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Frank B

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Re: Battery curves - Converter vs Solar?
« Reply #26 on: August 06, 2017, 05:22:41 PM »
Thanks, Gary.


Now I have to figure out exactly which model I have. No, correction. I have to find specs on the particular model that I have. :-) There appear to be an almost unlimited number of variations on the 8333 Coleman roof mounted air conditioner. :-(


Basically, I need to find out if there is any way on God's green earth to run this air conditioner off a 2000 watt eu2000i Honda generator.  They make a low-power model that runs on a thousand watts, but I cannot determine from anything I can find on the web whether my machine meets those criteria or not. I may end up having to ask Coleman themselves what this means. Their website is not a great help.


And, in the final analysis, I will probably have to sell the 2000 watt Honda, and buy a 3000 watt unit from somebody else. With all the solar that I have now, I don't need the quiet generator. I just need something that will run the air conditioner on a particularly hot day if required. Extension cords are cheap, so I can put it a long way out in the desert. :-)


Feel free to split this off into another thread.  In fact, I may repost this myself as a separate question.


Frank.
« Last Edit: August 06, 2017, 05:26:15 PM by Frank B »
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

 

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