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Old 08-14-2014, 07:11 PM   #21
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Unfortunately charging a battery is not that simple. As battery voltage goes up it tends to resist charging which makes the process slow down. The fourth stage spoken of is equalize, this is a higher volts per cell voltage that is used to shock the process to clean the battery plates. This is only dome every three months, or when test indicate sulfaction of the battery. Most chargers limit this to 15V due to connected equipment and potential battery damage. Specific gravity is the best method for determining charge level. each manufacture will have their recommended sg when fully charged.
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Old 08-14-2014, 07:42 PM   #22
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Originally Posted by J Mac View Post
If running down the battery below 50% does have an adverse effect on the life of the battery, is there an automatic switch that will shut down high draw items to prevent this?
Yes. There are portable devices, such as mentioned in post #35 of the recent discussion of CPAP machines, similar devices intended to be built-in, load-control features of some solar power controllers, and auto-shutoff features in power-consuming devices such as inverters. Some of them cut off at much lower than 50% charge level; they're just trying to prevent unacceptable operation, or completely flattening the battery. Others are trying to prevent the use of power in a vehicle when the engine and charging system are not running (so the cutoff voltage would be way too high for this purpose).

Electronic do-it-yourselfers may choose to build their own, and could set it for a suitable voltage... but of course voltage is not a good indicator of battery charge level if there is any current flowing in or out of the battery.
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Old 08-14-2014, 07:48 PM   #23
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Specific gravity is the best method for determining charge level. each manufacture will have their recommended sg when fully charged.
I agree. I personally wouldn't bother checking specific gravity regularly, but if doing a test to see if my system really charged my battery, I would want to measure specific gravity to make the assessment. The required tester only costs a few dollars. The link is to the first one found in a Google search; it looks like the one I use on the rare occasions when I am wondering about the condition of a battery cell and thus test specific gravity.
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Old 08-14-2014, 08:27 PM   #24
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It is what ETI advertises- group #29 -- 126 Ah- I'll have to look at mine to verify. I'm only concerned as to what I need for one night as the solar will refill me the next day.

I was understanding that it was an Interstate battery, and assumed an SRM-29, is that correct?

Given this assumption, I'm going by the 5 amp hour rating from Interstate(i.e. 5 amps x 21 hours=105 Ah) which approximates the 20 hour test data on batteries of this class. The 20 hour test is the standard for deep cycle batteries.

It appears that Escape is using the quick and dirty .60 times the reserve capacity, which will give 126 amp hours. The calculation of Ah from reserve capacity is actually a bit more complicated than this, but if you can't get a true 20 hour amp rating from the manufacturer, this will give you a 'rough' estimate.

It's always best to go by the actual battery manufacturers data based on the standard 20 hour test.

All that said, it always comes down to what works for you.

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Old 08-15-2014, 01:04 AM   #25
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I have found the mantra provided by Handy Bob regarding his recommendations on solar to be interesting and informative.

In this review I am comparing the battery charging results from the built in WFCO controller that Escape provides to a solar controller that I choose specifically for the ability to adjust the charge rate. My goal is to get batteries as full as possible as espoused by Handy Bob.

..... I am using a Trimetric 2025 RV Battery Monitor and taking observations at certain points.

What about the solar system that Escape provides? I do not have that system so I cannot test the results, one reason I do not have it is the Go Power controller, while better at charging than the WFCO controller, still does not meet the recommended charge rate from Interstate Batteries.

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Originally Posted by Vermilye View Post
I have the GoPower controller with the 95 watt panel, and a Trimetric battery monitor.


Paul & Jon:

I'm working my way through Handy Bob's write up on solar power. He makes a lot of sense but is "wordy" so it's taking some time to get through it.

We have a new 180w solar panel with the stock ETI GoPower controller, and the stock WFCO "charger". They both supply similar voltages which are below what Handy recommends. We haven't travelled with our Escape 19 for more than a few days so don't have any first hand experience.

This discussion is making me think of upgrading the solar controller.

But to my main question. I just installed a Trimetric 2025 battery monitor. (In fact I just finished putting it in today.) How are you guys setting the "battery full" indications in the Trimetric? There are two set points for "battery charged" determination, voltage and current. To indicate "full" the voltage must be above the set voltage and the current must be below its set point. Trimetric gives guide lines for setting these, but I'm confused with two changing sources (charger and solar), among other confusions. They also suggest a setting if primarily in "float" mode. I wondered the thinking you used to set these and what settings you ended up using? Sensing battery full seems to be an important detail.

Thanks.
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Old 08-15-2014, 08:34 AM   #26
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Trimetric 2025 Settings

Here is my take on the settings for a Trimetric 2025. I have found a lot of variety of what people recommend so there obviously is some latitude. The key settings are P1 and P3, setting those will make it work properly. The other settings are fine tuning.

These are for dual 6 volt GC2 batteries from Interstate.

P1 = 15.2
P2 = .5
P3 = 230

P7 = L1

What these settings will do is:
Upon completion of a full charge the green light on the 2025 will start blinking.
The percentage full calculation will now show 100% and be reset to such.
The days since charge indicator will reset to zero.

With that said there are a couple of things to keep in mind: Because the Trimetric does not allow the entry of decimal numbers in some of these settings and you are purposely setting P1 too low, the full percent on the Trimetric may be reached before the solar controller has filled the battery. It is pretty close but could be several more hours before the controller finishes charging. The way to tell the controller is finished is when it drops/switches to the float/storage/trickle mode.
Be careful with the reset button, you do not want to reset the percent full as it is determined by the settings you use in P1 and P3.
What number I find I monitor is the Ah, looking at the percent has the same affect but the Ah is the raw number of how far you are from the P3 setting of 230 Ah.

What Jon pointed out, and I thank him for this, is the last 2-3 hours of charging will proceed very slow. It is hard to get those last amps into the battery. Using the high voltage that Interstate recommends will help that process. What I do not understand is, if using a lower voltage and given enough time can you get the proper amps into the battery?
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Old 08-15-2014, 08:40 AM   #27
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Hugh
I see you have an 2011 Escape 19, assuming you have the dual 6 volt batteries you may have the prior model of batteries from Interstate, the U series. I believe the voltages are even higher for these batteries as recommended by Interstate. Charging would be at 15.5 volts and the P1 setting would be 15.4.
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Old 08-15-2014, 10:22 AM   #28
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What I do not understand is, if using a lower voltage and given enough time can you get the proper amps into the battery?
According to my TriMetric, yes, although the time it takes is more easily measured in days rather than hours. The final "topping off" of the batteries will take time because the batteries draw less current as they fill. Too high a charging voltage during the final stage will result in over heating & gassing of the battery. This is one of the reasons a solar panel is a good investment. The amount of gas needed to run a generator for the last 10% - 20% of battery fill can be annoying since your converter is only putting a couple of amps into the batteries. While the solar panel may produce far less current than your converter during the bulk charge, since it produces all day it is a good source for the absorption (final charging) phase.
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Old 08-15-2014, 07:03 PM   #29
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Hugh
I see you have an 2011 Escape 19, assuming you have the dual 6 volt batteries you may have the prior model of batteries from Interstate, the U series. I believe the voltages are even higher for these batteries as recommended by Interstate. Charging would be at 15.5 volts and the P1 setting would be 15.4.
Paul:

I should have included that. Our 19' has a single 12v battery, an Interstate SRM-27. It's 95-100 Ah, wet cell. It was in the trailer when we got it so I don't know if it was original or not. I had it checked and it's in good shape. When it goes we'll replace with two 6v of some kind.

Our stock converter, WFCO, charges at 14.4v bulk, 13.6v absorption, and 13.2v float. The GoPower solar charger uses 14.4v bulk/absorption and 13.7v float. I don't see any times associated with these.

Trimetric suggests setting the voltage set point just below the changing voltage. For these chargers that would be some 14.3v. They suggest setting the current set point at Ah capacity divided by 50. For my 100 Ah battery that would be 2A.

Trimetric also suggests an alternative method. This is to set the voltage set point just below the float voltage, for these chargers 13.1v AND set the current set point to Ah capacity divided by 90, for my battery 1.1A. For this scheme the battery is declared fully charged when it's been in float mode long enough that the charging current has dropped below 1A.

These stock chargers aren't adjustable, so I suspect the 14.4v will leave the battery under charged. I'm wondering if Trimetric's float method would give a better indication of when to declare the battery charged. Any thoughts?

This doesn't affect the changing of the battery, just Trimetrics starting point for counting down Ah to 50% discharge. But I'll use this "gage" for battery maintenance and protection so the more accurate the starting point the better.

Thanks.
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Old 08-15-2014, 08:00 PM   #30
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It may be miss leading to talk about voltage for bulk changing. My understanding is that initial, or bulk, changing should use constant current. The voltage should rise until a set amount of current goes to the battery. I've read this current should not exceed C/5 (Ah rating for battery divided by 5). For a 100 Ah battery that would be 20A. As the battery is charged the voltage will rise until it reaches some set point. I've read this point should be 14.4v, but I'm sure this varies. This leaves the battery about 80% changed.

Once this voltage is reached the charger goes into absorption mode. Here the voltage is held constant, again I've read about 14.4v (or so). As the battery charges the current will slowly decrease. This likely varies, but I've heard this should continue until the current falls to about C/100 (Ah rating of battery divided by 100). For a 100 Ah battery this would be 1A. This brings the battery up to about 95% charged.

After the absorption phase the charger goes to float mode, a lower constant voltage. Here I've seen 12.8v to 13.2v. This phase tops off the last 5% and then maintains the battery fully changed.

My stock WFCO and GoPower changers both mention a fixed voltage for bulk changing. I don't think this is optimum. I looked at the specs for the Blue Sky 30 and it seems to follow the above charging scheme. The Blue Sky should be quite a bit quicker to charge a somewhat discharged battery. But once up to about 80% they'll be about the same, and be pretty slow. Unless the absorption voltage on the Blue Sky (or similar) is increased. Likewise, I don't think additional solar panels are likely to speed changing above 80%.

But I also read that wet cell lead acid batteries can be charged at 15.5v in the absorption phase. I'd be worried this may start to boil off water though. It points to the possibility of raising the absorption voltage set point in the Blue Sky which could reduce changing times. Might be worthwhile. Any thoughts?

I'll have to get one of them "hydrometers" and go camping. Or maybe just get a couple of junk novels and go camping. Better yet, take the wife and the dogs and go camping.

Go camping.
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