Salvo
California
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bigfootford wrote:
Salvo, Yes in the chart examples they were obtained with one AGM 110ah battery. I do have others derived from 2 group 24's.
Jim, The converter didn't go into current limit with just one battery discharged to 50%. We may not see 60A with 2 batteries. However, if you turn on extra loads in the MH (perhaps power the fridge on 120V inverter) you will go into 60A current limit.
bigfootford wrote:
The math shows a .37 volt drop.....actual measurements during initial charging showed less than .3 measured at the converter and then at the battery. (200 mv of that from 2 100 mv shunts). I was attempting to keep under .3 for my actual system.
I don't understand your math nor what you're referring to. When doing math, it's always good to start with an equation and provide real numbers. The voltage drop (I'm assuming you're talking about line drop) is a function of charging current. I calculated your (chart 2) line drop to be 15 mohm. So the current corresponding to a .37V drop is: 0.37V/.015 ohm = 25A.
bigfootford wrote:
If I was to put a 20 ah battery that was down 50% SOC and I put the XADC 60 on it to charge I would expect it to do the bulk mode and give the battery what ever it can accept, It wouldn't be much but still it should be bulk mode, then after bulk mode It should switch to absorb mode and do that for 2 hrs or so. in theory get the battery close to 100%. Then drop into Float of 13.5. I have not seen the XADC perform that way.
Same applies to the others PD, WFCO etc. Do they perform exactly as specified???? No. But the PD is the one that does the best in my book.
Your interpretation of the specification is not correct. Whether or not the converter enters current limit is dependent on external factors to the converter. It depends on two things: the line resistance and the voltage on the battery. If the line resistance and battery voltage are low enough, guaranteed the converter will deliver 60A.
It's easy enough to calculate maximum battery voltage for 60 charging:
I already gave the equation: Vconv = I * resistance + Vbat
We solve for Vbat and get:
Vbat = Vconv - I * resistance
For graph 2, with Vconv = 14.35V and resistance = 15 mohm, we get:
Vbat = 14.35V - 60A * .015 ohm
Vbat = 13.45V
The battery voltage needs to be below 13.45V for the converter to supply 60A. Your graph shows the charging voltage starts at about 13.9V (@ the 4 minute mark). The converter will not go into current limit as the battery voltage is already too high.
bigfootford wrote:
Maybe this has hijacked the OP's post and I apologize for that.
His problem is not resolved, although early on we all said his wiring was probably to fault. I hope we haven't scared him off.
There are a few things that could be bad. Perhaps the battery disconnect relay? I didn't activate my relay for over a year. Over time, the closed contacts developed a higher resistance. This caused my converter charge time to be worse than ever. Besides the mod to the Parallax converter I also deleted this relay from the circuit. Other than line resistance, the only other thing that could be the problem is the battery. Has the battery charging resistance increased? The larger the resistance, the slower the charging time.
Cal
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mapguy
Puget Sound
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Joined: 09/02/2007
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You need more charger to get the recharging results desired.....Xantrex recommends the True Charge RV-80 unit for 400Ah battery banks. They recommend 220 Ah battery banks for the 40 and 60 amp units. heck the spec here:
Xantrex XADC
Undoubtedly the factory wiring between the charger and batteries is minimal size for the run length but reworking it isn't going to magically increase charging rate to a 2 hour window from a 65% SOC on that size battery bank using a 60 amp maximum charger.
I am in the same boat - True Charge RV-40 is OEM for my 2008 Rage'N FA 3005 to support the two OEM Group 24 Marine batteries. I have just installed 4 x 6v GC2b batteries and will be investing in a larger charger soon too. Isn't funny how these modifications just turn into snowballs of greater $$$
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bigfootford
Fair Oaks, California
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Salvo wrote:
Jim, The converter didn't go into current limit with just one battery discharged to 50%. We may not see 60A with 2 batteries. However, if you turn on extra loads in the MH (perhaps power the fridge on 120V inverter) you will go into 60A current limit.
The battery voltage needs to be below 13.45V for the converter to supply 60A. Your graph shows the charging voltage starts at about 13.9V (@ the 4 minute mark). The converter will not go into current limit as the battery voltage is already too high.
Cal
Cal, we don't expect a converter to charge at current limit unless our battery banks can handle it. We just don't want it to stop like the XADC did in chart 1.
What we want is for the converter to charge at the highest rate possible, raising the voltage to 14.X and then after a timed duration go into a preset absorb stage and then to a float voltage. That applies to a small bank 75 ah or a hugh bank of 400+.
Even a small 20 amp smart converter can perform this task, it will just take longer.
If a smart converter was hooked to a battery and there was a 1 + volt drop in the wiring the battery would finally reach the charge voltage of 14.x if you left the voltage at 14.x long enough.
Keep in mind that my agm battery in this test has a higher resting voltage than a flooded wet cell. +.2 to +.3 Thus the Xadc is already in trouble because it's just like voltage drop caused by wire size and connection issues.
I don't see a cure for this other than something like the truecharger Xantrex or others which has settings for AGM's. Several guys have had good success with the PD charging AGM's.
Blue Sky solar charge controllers have an adjustment to compensate for this issue of AGM's.
Jim
94 F-250 ex cab,460, E40D tranny,airbags w/pump,bilstein shocks, 2000 Bigfoot 9.6 2500 camper, Progressive Dynamics 9260, Trimetric monitor and an eu2000i honda genny.
Wife and Molly- Ausie,Queensland healer
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Oswald38
3rd Rock
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Joined: 12/04/2007
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"What we want is for the converter to charge at the highest rate possible, raising the voltage to 14.X and then after a timed duration go into a preset absorb stage and then to a float voltage. That applies to a small bank 75 ah or a hugh bank of 400+."
That is precisely what my observations have been on the XADC. Been watching it in my friends RV that we upgraded to the Xantrex. Not sure why you see different but saw your graph.
When he runs them down to about half or a little farther, it slowly raises the voltage maintaining 60 amps for well over an hour and then the current tapers and the voltage hangs out for a period. Not always exactly the same time but varies depending on how discharged they were.
I'll have one in a few days and try and graph it as well.
My PD doesn't even give a chance and falls on its face after about 20-30 minutes. Go figure.
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Hurricaner
Hurricane Utah
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Joined: 02/17/2007
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Jim if you look at your charts the Xantrex is doing exactly what is designed to do. The thing you have to remember is as soon as the converter sees 14.2 volts at its terminals it goes into what Xantrex says is an absorption mode, even though the only thing that changes is a 2 hour timer is started. If you look at the last chart it clearly illustrates this, as the converter went into the absorption time(mode) almost immediately because it measured 14.2 volts at it's terminals and 120 minutes later it went to float.
Of course with no indication and no change in output voltage, I'm not sure how you tell when it enters this so called mode, other than to assume it happens at 14.2 volts.
Sam
Sam & Kari
Hurricane, Utah
2004 34' Damon Challenger 315
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Salvo
California
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bigfootford wrote:
Keep in mind that my agm battery in this test has a higher resting voltage than a flooded wet cell. +.2 to +.3 Thus the Xadc is already in trouble because it's just like voltage drop caused by wire size and connection issues.
I don't see a cure for this other than something like the truecharger Xantrex or others which has settings for AGM's. Several guys have had good success with the PD charging AGM's.
Blue Sky solar charge controllers have an adjustment to compensate for this issue of AGM's.
Jim
Jim-
Sounds like we're getting to the bottom of this. Your Xantrex isn't setup of agm batteries. I also don't believe you discharged the battery far enough to reach 50% discharge state. I consider 12V the 50% discharge point for a standard battery. What is that level for agm batteries?
BTW, you may want to open up the XADC 60 converter and look for a voltage adjustment pot on the circuit board. You may be able to increase your output voltage by 0.3V to match the agm batteries. I have a pot on my Parallax 7345 converter that I needed to re-adjust after modifying the voltage feedback loop.
Cal
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Hurricaner
Hurricane Utah
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Jim, do you have Optima batteries? They have a very high at rest voltage and arn't exactly a true AGM battery.
Sam
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bigfootford
Fair Oaks, California
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Hurricaner wrote:Jim, do you have Optima batteries? They have a very high at rest voltage and arn't exactly a true AGM battery.
Sam
It's a Universal AGM gp 30 110 AH battery.
Wayne (Reddog1) has a Lifeline gp 31 100 AH and it's resting voltage is the same as mine.
Jim
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bigfootford
Fair Oaks, California
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Salvo wrote:bigfootford wrote:
Keep in mind that my agm battery in this test has a higher resting voltage than a flooded wet cell. +.2 to +.3 Thus the Xadc is already in trouble because it's just like voltage drop caused by wire size and connection issues.
I don't see a cure for this other than something like the truecharger Xantrex or others which has settings for AGM's. Several guys have had good success with the PD charging AGM's.
Blue Sky solar charge controllers have an adjustment to compensate for this issue of AGM's.
Jim
Jim-
Sounds like we're getting to the bottom of this. Your Xantrex isn't setup of agm batteries. I also don't believe you discharged the battery far enough to reach 50% discharge state. I consider 12V the 50% discharge point for a standard battery. What is that level for agm batteries?
BTW, you may want to open up the XADC 60 converter and look for a voltage adjustment pot on the circuit board. You may be able to increase your output voltage by 0.3V to match the agm batteries. I have a pot on my Parallax 7345 converter that I needed to re-adjust after modifying the voltage feedback loop.
Cal
Now you understand the issue. There are adjustments inside the XADC. My goal was to test AS_IS first. It is my feeling that if the MFG sells something it should work as advertised with AGM or WET Cell.
I have the skills to modify circuits and tweak voltages but many on this forum and others that purchase these units don't. And if they run into certain issues they are stuck....Randy at BestConverter and the tech's at PD etc beat their heads against the wall dealing with this issue all the time.
Cal, check your PM's, I sent you one a couple of days ago.
Jim
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Hurricaner
Hurricane Utah
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I don't understand the voltage issue, what difference does the at rest voltage make? If anything AGMs recommend a lower charging voltage not higher. I also do not understand the complaint that the charger was not functioning as advertised when the graphs you posted clearly show it is, please clarify.
Sam
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