Battery Charging with a Trace Inverter - Do I have an issue?

[Lin]

As thorough as you are, I'm sure you checked the batteries individually.  Would one bad one or even one bad cell cause such a problem?

[rv_safetyman]

Lin, in June, I checked each cell with a hydrometer.  I will repeat that tomorrow.  With the same clothes that now have holes in them

[Lin]

Sorry to say this, but hearing about the acid holes in your cloths made me feel good.  I way convinced that I was the only one to continually ruin clothing whenever I get near a battery.  Hence, another plus for the AGM.

[Oonrahnjay]

(snip)  I way convinced that I was the only one to continually ruin clothing whenever I get near a battery. 

OK, that's three of us, then.

[Sean]

...
That explanation confuses me.  Almost sounds like Bulk and Absorption is the same thing (?).  In any case, the absorption is set for 2 hours and I know that the yellow light does not stay on anywhere near that long.
...

Jim,

First, let me say you are getting a lot of advice here from people who are clearly not familiar with the SW series and its byzantine settings.  At the risk of offending well-meaning folks who are just trying to help, guessing at inverter settings or trouble symptoms without a thorough understanding of these units and their peculiarities is ill-advised.

In the SW series, Bulk and Absorption are most definitely not the same.  However, as you note, the yellow LED, which is confusingly labeled simply "Bulk," does not necessarily mean the unit is in the Bulk phase.  In fact, this LED is used for Bulk, Absorption, and Equalize phases.  In Bulk and Absorption, the LED is a steady yellow, whereas in Equalize it blinks.

On a Trace SW, the only way to tell if the unit is in Bulk or Absorption when the LED is on steady is to look at the voltage.  If the temperature-compensated voltage is below the Set Bulk Volts DC setting, then the unit is in Bulk.  If the voltage is at or above this voltage, then the unit is in Absorption.

If you do a full charge cycle starting from, say, 50% SOC (for real, not necessarily what the Tri-Metric says), then you would see nearly a full two hours (if that's what you set for Absorption time) in the absorption phase.  The only way to time this, though, is to be watching the temp-comp voltage reading closely, and start your timer at the instant the voltage ticks over from a tenth of a volt below the setpoint, to the setpoint voltage.  Also, the timer is "sloppy" in the first 20 minutes.

If you are seeing the LED illuminated for less than the set time before the unit goes to Float it is because the absorption timer is cumulative.  This is described on page 47, under the detail for Set Absorption Time.  If AC power is applied before the batteries have depleted to the point of requiring a bulk cycle, the amount of absorption time will be only what the timer has accumulated.  Note that temperature compensation and load can both affect the perceived battery voltage, to the point where the unit does not enter the Bulk phase and instead goes straight to absorption.

Having batteries that are nearly full when AC power is applied will lead to this type of short cycle.  Note also that certain types of battery problems can present the appearance of a bank that fills rapidly and does not initiate the expected Bulk charge cycle.

The behavior of your system sounds perfectly normal to me, although I suspect two things.  One is that your batteries are not accepting a complete charge, probably due to insufficient gassing.  I would expect a good equalization will help with this a great deal.  The second is that your SOC meter needs tweaking.  This is just an educated guess, of course -- without closer inspection and more testing, the possibility of a bad charger control circuit can not be ruled out.  I think, however, it is the least likely probability.

The only way to know for sure what is going on is to do a fully controlled load/discharge test and a couple of full charge cycles.

I suspect the TriMetric measures amperage pretty well.  It uses a shunt (should be reliable) and the amperage is a simple conversion of the voltage across the shunt

Actually, this type of shunt system, while good, is only as accurate as its calibration, which must be done in the field.  Out-of-the-box I would estimate these meters to be no more than about 98% accurate for voltage and current (the meter itself is more accurate than that, but the shunt and cables introduce more error).  When it comes to SOC, the accuracy is a good deal less, because many factors such as Peukert exponent and Charge Efficiency are estimates, and if the meter over- or under-estimates charge in either direction even by a little bit, over time this can accumulate into large errors.

Most meters compensate for this by "resetting" to zero (or full, depending on POV) under a well-defined set of conditions.  Getting those condition settings correct is part engineering, part trial-and-error, and part voodoo.  Get them wrong in one direction, and the meter will reset prematurely, giving the impression the batteries are full when perhaps they are not.  Get them wrong in the other direction, and the meter will never reset, leading to ever-lower SOC readings when the batteries are, in fact, full.  You are better off with the former, because that error is not cumulative.

FWIW, our SOC meter, even adjusted as accurately as possible, will accumulate negative error over many generator cycles.  We don't ever go to 100% full charge on the generator, because that is very inefficient (three hours of extra run time while putting only about 90 amp-hours in, just 10% of capacity).  So the only time our SOC meter resets to "full" is when we have a solid shore power connection with enough extra power to run the charger all night.  After a couple of weeks of boondocking in one spot, our meter will be reading perhaps 80% of actual.  IOTW, at 50% SOC, the meter would read around 40% SOC.  The more charge cycles we run, the worse the error gets.

Also FWIW, I've been doing this for eight years full-time and I'm still tweaking the charge and generator settings on the Trace and the parameters on the SOC meter.  I'm on my third set of batteries, and each set requires careful readjustment of all the settings, part of which can only be done with direct load-cycle experience with that particular bank.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com

[gumpy]

Yeah, what Sean said.

if I understood what you said about your current readings at around 2 amps, then you are fully charged. The problem is not your Trace. It's your Bogart settings.  BTDT.

[garhawk]

Hi Jim,

I concur exactly and totally with what Sean said.  That should take care of it!

[rv_safetyman]

OK Folks, it does, indeed, look like the TriMetric is out of whack.

First of all, the batteries are labeled "Energizer" and are made by Johnson Controls (like most batteries).  I do recall reading that Sam's sells three different Golf Cart batteries, depending on the part of the country.  Mine were purchased in Denver.

My plans (dreams?) for this battery change was to go to L16 AGM batteries.  However, I did not hit the lotto, so it was back to golf carts.  The last set served me pretty well for well over 6 years.

Last nights testing was interesting.  After 3 hours without AC input, the SOC dropped from 76 to 73%.  That is about normal with all the AC and DC loads I have.  The discharge current without the fridge showed 3.7 amps and 5.8 amps with the fridge (both at 12V).  I have quite a bit of electronics running in the background.  Those currents suggest I don't have a big draw.

As soon as I turned on the AC input, the charge current in bulk went to 84 amps @12V (sort of confirmed with my cheap straddle type DC ammeter).  It decreased to about 35 amps in a few minutes.  I did some looking at the Trace meters and they suggested about the same values (converting 120V current to 12V current in my head).  I unplugged the temp sensor to see if that made a difference (didn't). 

About a half hour into the test, I took one quick hydrometer reading and it showed in the middle of the green area.  The green area has number values from 1.275 to 1.300 and the level was between the two.  That sure suggests that the SOC meter is off (it read 77%)

The bulk yellow light (includes absorption) stayed on for close to 2 hours.

As I think about it, I may has messed up the SOC integration process.  Two or three times over the past few months, I have taken the lazy approach to maintaining the charge of the start batteries.  I simply connect the house and start batteries and let the inverter charge both.  The current to the start batteries does not go through the SOC shunt.

During the testing process, I used my infrared temperature gun to check all connections and battery temperatures.  All were in the ambient temperature range (about 80* F).

Today I will do a full hydrometer study of all cells and start working on the TriMetric settings.  That will be a challenge, as the manual seems to have been written by a monkey.  Almost like it was written off shore, but I am pretty sure it is made by a small company in the US.

Again, I am amazed by the great help from this group.  I should not be surprised since it happens every time I have an "issue".

Jim

[Ace]

Jim not that this is any help but my six golf cart batteries were also purchased at Sam's and my friend John Silver who owns central florida bus is always ragging on me about switching them out because the date on mine is 2004 which makes them 8 years old! Im the type that if it isnt broke dont mess with it and they are still working great! The inventor charges them automatically and heck I think i put water in them twice since installing them which reminds me I have to go...


Sent from my iPhone using Tapatalk

[eagle19952]

you need one of these for your birthday...


http://www.ebay.com/itm/RHA-200ATC-Glycol-Antifreeze-Battery-Refractometer-/290614967217?pt=BI_Cellular_Optical_Television_Test_Equipment&hash=item43aa007bb1

[rv_safetyman]

Well, I have nailed it down to my TriMetric SOC gauge needing to be reset.  I had set it up to reset itself after every full charge, but apparently that did not work.

So, let's catch up.  A couple  of days ago after at least 24 hours of charge on the inverter, I reset the TriMetric.  That night I removed the AC source.  The next day I had to run a bunch of stuff to get the meter down to 55%.  I checked all of the cells with the hydrometer.  They were all pretty close (a bit operator sensitive ) and all indicated to be at mid-range.  That seemed to verify that the SOC meter was close. 

I then applied the AC.  I turned off most of the loads that I had fired up to get the battery down to 55% and the inverter was charging the batteries at 122 amps (12V).  That slowly tapered off to a bit over 60 amps after close to 2 hours.  At that point, the SOC was 80%.  At the end of 2 hours, the inverter went into float.  All of that looked like the process I had been used to in the past.

This morning the SOC was 92%.  I reset the meter again.

I think I am good to go.  Sure glad that I did not have an Inverter problem!!

Again, thanks for all the help!!

Jim

[Sean]

Well, I have nailed it down to my TriMetric SOC gauge needing to be reset.  I had set it up to reset itself after every full charge, but apparently that did not work. ...

As I said, "voodoo."  Getting these meters to correctly detect completion of a full charge cycle is a challenge; I would estimate that I've spent nearly a half dozen hours fiddling with mine to dial it in, and dozens of charge/discharge cycles.

I don't have a Bogart, so it's harder for me to give you precise advice, but often the problem is the finishing current setting.

For us, the optimal settings lead to a situation where the meter never resets while we are boondocking with the generator, but always resets when a finishing charge has been applied by shore power.  We typically find a power outlet at least once a month, so the meter is usually accurate enough for most purposes.

A bigger issue for us on a daily basis is that the generator auto-start system is based on voltage and not SOC.  Even the less-than-fully-accurate SOC reading would be a better metric, considering the voltage is so widely variable depending on load.  Where we are parked right now, running the air conditioner full time when we are home, the generator starts after fewer than six hours, even though I know we can go for eight.  I don't dare lower the voltage setting, though, because it would then be too low for the scenario where there are no major loads present.  Still, not a big enough problem for me to want to replace my "free" autostart system with something else.

-Sean
http://OurOdyssey.BlogSpot.com

[wagwar]

I am certainly not presuming to be any kind of expert, but I also have a Trace SW4024 and a Trimetric 2025 monitor. I have had several conversations w/ Ralph at Bogart Eng. and he has been very helpful, informative and patient. If you are having a problem getting the settings correct on the Trimetric, give him a call.  I was also a little confused by the text in the Trimetric docs, but after a few discussions with Bogart, I realized that I was the weak link in the chain - not the docs.