Excessive high voltage on charge

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Excessive high voltage on charge

Postby lsilverman on Sun Mar 02, 2008 3:20 pm

I have just replaced a Xantrext 2500 Freedom with a new vfX 2812m

In charging mode, it puts out over 15 volts. This cannot be good.
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Postby tallgirl on Sun Mar 02, 2008 3:28 pm

Maybe, maybe not. What charging phase did your Mate report the FX being in? And what were the voltage set-points? And what is the battery technology?

Over 15VDC can be just fine, depending on what is going on with the charger and the type of battery.
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Postby lsilverman on Sun Mar 02, 2008 7:01 pm

here is a little more info..

(3) 4-d 12 volt AGM's by TROJAN. Trojan recomends 14.4 - 14.6 Volts for the absorb rate. I set the absorb rate on the Mate2 to 14.6
When it reached 15 volts my Xantrax Link monitor froze and I had to dissconnect it to restart it and I shut off the A/C. If the absorb rate is set at 14.6, why is it putting out 15 volts?

Is there a way to restore all of the settings back to "default" on the Mate2?

It appears that the default values are right in the middle for AGM's and perhaps I should reset it and leave it alone for now until I can understand use the features later this spring. I just need to get back to default.
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Postby crewzer on Mon Mar 03, 2008 6:07 am

Lynn,

Typical temperature compensation for 12 V batteries is -0.03 V/C. If your charger is set for 14.6 V (ref 25 C / 77 F), if an RTS is attached to the batteries and plugged into the 2812, and the battery temperature is ~56 F (~13.3 C), then 15.0 V would be the correct temp comp’d charge voltage.

However, you might want to double-check the 14.4 V – 14.6 V “recommendation”. That's usually a bit high for AGM batteries, and it’s quite high for gel batteries. Trojan’s on-line maintenance manual suggests 13.8 V – 14.1 V as the “daily charge” (Absorb) setting for “12 V” VRLA (AGM and gel) batteries.

See “Table 3” in this document: http://www.trojanbattery.com/Tech-Suppo ... rging.aspx

There is typically some combination of four reasons for the high charge voltage you’re seeing:

(1) The charger’s absorption target voltage is set wrong. The default for the 2812 is 14.4 V. This can be changed by using the Mate and following the instructions in the inverter/charger manual(s).
(2) The batteries are very cold and the temperature compensation feature has increased the charge voltage. This can be checked by unplugging the battery RTS from the inverter, which should cause the charge voltage to drop.
(3) The 2812’s internal voltmeter could be mis-calibrated. This can be fixed using a quality DVM to measure battery voltage at the terminals, and then using the Mate and following the instructions in the inverter/charger manual(s).
(4) Although unlikely, the charger could have been set for the “Equalizing” mode.

I recommend that you work through the four items listed above and then report back with the results.

HTH,
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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You are right

Postby lsilverman on Mon Mar 03, 2008 7:48 am

I don't know why I was reading a different number and the temperature compensation would also account for the difference.

Since I'm going to go in and reset the levels, should I use 14.1 of 14.4 or something in the middle?

Also, I thought that the charger automatically steps down to float when the batteries reach a certain level, why is the mate asking me for an absorb time?
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Postby crewzer on Mon Mar 03, 2008 10:23 am

Trojan’s 14.1 V recommendation is referenced at 80 F. Since the 2812’s reference is 77 F, I’d suggest setting the absorption voltage at 14.2 V.

The 2812’s absorption period is time-based. I’d suggest a 3 hour absorption time period for your AGM batteries.

HTH,
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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interesting information conflict

Postby lsilverman on Mon Mar 03, 2008 12:14 pm

This is the data sheet I was reading when I set up the 2812

http://www.trojan-battery.com/ProductLi ... lsheet.pdf

So I figured that 14.6 was safe

FYI, the Trojan tech informed me that 14.7 is the maximum voltage when temperature adjusted and if the 2812 will adjust .003 volts, then 14.4 is the number. Any thoughts? Or am I drowning in a glass of water over this....
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Postby crewzer on Mon Mar 03, 2008 2:57 pm

Would it be nice if we could just get complete and consistent specs? Grrrr… :mad:

Reading between the lines, the Trojan tech might have a point about the voltage spec including a TCF. I have my controller set at a TC limit of 29.4 V, which translates into 14.7 V per 12 V battery. My batteries are Deka/MK AGM size 4D’s.

I think we’re close here. FWIW, I have my controller’s absorption target voltage set at 28.6 V, or 14.3 V per 12 V battery ref 77 F / 25 C.

So, either 14.2 V or 14.3 V should be fine. Just remember to confirm the voltage at the battery terminals near the end of the absorption stage, when the charge current is low and the voltage drop in the cables between the controller and the batteries is minimized.

HTH,
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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sounds good

Postby lsilverman on Mon Mar 03, 2008 3:12 pm

So assuming the 15 volt experience was indeed a temperature correction by the 2812, I'm going to try 14.3 and watch what happens. Thanks for the tip regarding actual voltage at the terminals....

I'll let you know what happens.

BTW, on a related issue, my link monitor starts blinking whenever I start a charging cycle.. so when cruising, I carefully watch the used amp count until I hit about 35% ( 3 x 165 + 486 amphours x 35% = -170 amps )depletion and then I start the genset. The Link starts blinking and I loose the amphour count so I basically have to guess when I've charge enough. Any thoughts.
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Postby crewzer on Mon Mar 03, 2008 5:51 pm

hmmmm... It took me a bit to figure out the DoD formula. I think it's supposed to be -35% x (3 x 165 Ah) = ~ -170 Ah.

Which Link battery monitor model do you have?

Regards,
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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Charger performance

Postby lsilverman on Mon Mar 03, 2008 7:43 pm

I use the Link 10.

I programmed the Mate 2 to 14.2 volts and re-calibrated it to conform with a quality DVM at the battery poles (it was 1/10 off).

The charge cycle started and the input voltage slowly rose over the first 15 minutes from 13.8 to 14.35 Volts. So far so good.

Now for my followup question....

The 2812 is supposed to be a 125 amp charger. The output amps as indicated on the Link 10 and the Mate 2 never exceeded 75 amps. This is with everything on the boat (A/C and D/C) shut down.
I set the A/C input to "Cord" and set the perameter to 30 amps input to the inverter/charger. no change in DC amperage output. On the summary screen, the input voltage indicated 10A.

I thought AGM's could handle significant charge amperage and this scenario is only averaging about 24 amps per 4D battery.? I am not sure of the exact amount but the bank was down over 120 amps when I started this charge.
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Postby crewzer on Tue Mar 04, 2008 5:55 am

Lynn,

I programmed the Mate 2 to 14.2 volts and re-calibrated it to conform with a quality DVM at the battery poles (it was 1/10 off). The charge cycle started and the input voltage slowly rose over the first 15 minutes from 13.8 to 14.35 Volts. So far so good.

Sounds good! :cool:

The 2812 is supposed to be a 125 amp charger. The output amps as indicated on the Link 10 and the Mate 2 never exceeded 75 amps. This is with everything on the boat (A/C and D/C) shut down. I set the A/C input to "Cord" and set the perameter to 30 amps input to the inverter/charger. no change in DC amperage output. On the summary screen, the input voltage indicated 10A.

The 2812 charger’s output current is rated at 125 ADC max. This current level is available when the charger’s AAC value it set to its maximum (16 AAC for the 2812), the battery voltage is a bit low, and the charger is operating in bulk mode.

The charger default AC Amps input current value is 14 AAC. This partially explains the “low” charge current. You’ll need to use the Mate to go into the ADVANCED / CHARGER / CHARGER LIMIT menu to increase this parameter from 14 AAC to 16 AAC. This change should increase charge current during the bulk charging stage.

The charger will automatically back off on charge current when the battery voltage achieves its target value. This is normal, as the absorption and float modes limit charge current in order to maintain the target voltages. As the battery bank’s SOC rises, the charge current will continue to fall.

I thought AGM's could handle significant charge amperage and this scenario is only averaging about 24 amps per 4D battery.? I am not sure of the exact amount but the bank was down over 120 amps when I started this charge.

AGM batteries can handle considerable bulk charge current. A typical value is 30% of capacity rating, which would be ~50 A per battery for your bank. This can be a very handy feature when the batteries are very deeply discharged. IMHO, the practicality of such a charge protocol for relatively shallow discharges is another matter.

I like AGM batteries. However, they seem to behave differently that do the usual flooded-cell models. For example, a high charge current – especially when they’re cold – appears to cause their terminal voltage to rise fairly quickly, which then causes the charger to switch from bulk mode to absorption mode. In effect, a short bulk stage seems to lead to a long absorption stage. I suspect that this behavior is part of the reason why AGM batteries have a reputation for “liking” long absorption stages.

You may need to experiment with your charger settings to find a good balance of charge time and generator loading.

I use the Link 10.

Deep cycle batteries are good for deep-cycle applications, but not for engine starting applications. I suspect the Link 10’s flashing display is caused by a momentary drop in battery voltage when the battery bank is loaded by the generator’s starter. This is likely exacerbated by the partially discharged state of the batteries. See page 27 in the owner’s manual for more information.

You may need to install a battery isolation switch to separate one battery from the others for starting operations. For example, one battery could be the “fixed” house battery supplying power to the Link-10, two batteries could be used for starting, and all three could be recombined for normal operations.

HTH,
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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Thanks

Postby lsilverman on Tue Mar 04, 2008 7:51 am

Thansks for all your invaluable help. I'll go in and change the charge limit. The Link issue is still mysterious in that it begins blinking even when I simply turn on the A/C shore power. No engine, genset or any other activities. I always start the genset with the main switch off and let it run for about a minute to acheive oil pressure and build up the capacitors. I then switch the main A.C on and the 2812 sees the line voltage and begins charging. The genset power and cord power come via the same path from a double switch with a preventer device to avoid turning them on together.

The house bank and starter batteries are separate and the link reads only the house bank.
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Postby crewzer on Tue Mar 04, 2008 10:27 am

Lynn,

The flashing display issue has me perplexed. :-k It might be worth opening the pdf user manual, searching on "flash", and then reading up on the various hits.

See: http://www.xantrex.com/web/id/72/docserve.asp

HTH,
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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Mea culpa

Postby lsilverman on Tue Mar 04, 2008 8:42 pm

I guess switching over from plug and play Xantrex to Outback is giving me the opportunity to really learn more than 12v 101 as the Outback programming instructions assume you have more than basic battery knowledge. After 18 years of sailing and apparently novice battery maintenance I am just now learning how much I don't know.

Thank you in advance for your patience and sharing your knowledge.

Here are some more observations, discoveries and questions:

1. I discovered today that the 2812 puts the bank through an absorb and float cycle daily regardless of usage or depletion. Perhaps this is why I am asked to program not only the voltage levels but also the duration. I assume the unit will absorb cycle as required to restore a charge regardless of the duration so, is the programmed duration solely for minimum daily charges? If so, what is the recommended duration for 12v agm daily absorb cycles during idle non-use days?

2. I have set the "cord" amperage to 30 amps. I think this is part of what Xantrex termed "power sharing". At this setting, the most I ever observed was 70Amps during a full charge cycle. Per your suggestion, I attempted to increase the Charge limit from 12 aac however it stopped me at 14aac. I will have to wait and see if this does anything. Why is this setting required in addition to the Genset or Cord input settings?

3. What do you suggest for a "Float Reset" voltage (default is 12.5) I am guessing that the charger will stay idle until it sees a reduction in voltage down to 12.5 and then it will float charge"

4. As a followup to the Float charge discussion, the programmed float charge time is it again a maximum or minimum time under what circumstances? and what is the optimal duration?

5. As a general question, is the float time subsequent to a major recharge different from the float time during a reset and if so, what are those times and which one am I being asked to program?

6. There is also a programming choice for the controller to be "on" or "auto" , what is the difference?

That's all my brain can handle tonight, back to election coverage.
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Postby crewzer on Thu Mar 06, 2008 5:36 am

Lynn,

Haven't forgotten you... just busy with "real" work.

More later,
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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Postby crewzer on Fri Mar 07, 2008 6:32 am

Lynn,

1. I discovered today that the 2812 puts the bank through an absorb and float cycle daily regardless of usage or depletion. Perhaps this is why I am asked to program not only the voltage levels but also the duration. I assume the unit will absorb cycle as required to restore a charge regardless of the duration so, is the programmed duration solely for minimum daily charges? If so, what is the recommended duration for 12v agm daily absorb cycles during idle non-use days?

I’m having trouble following you on this topic. As I understand it, there are three basic charger modes: AUTO, ON, and OFF. Selecting OFF in the CHARGER CONTROL menu (pres AC IN button three time) will disable the charger until you turn it back on.

If your AGM batteries are being cycled daily, then an absorb charge period of perhaps three hours should be about right. It just has to be long enough for the charge current to drop to ~1% of battery capacity. For your 495 Ah battery bank, the charge current should drop to less than 5 A and be fairly stable.

If your AGM batteries are in standby, they should require recharging but once a month or so. A longer absorption period might be warranted. The Mate can be used to program the FX and it’s charger to operate on weekend days only, so this might be an “automatic” twice-weekly recharging option. Another option is to plug the FX into a heavy duty timer.

2. I have set the "cord" amperage to 30 amps. I think this is part of what Xantrex termed "power sharing". At this setting, the most I ever observed was 70Amps during a full charge cycle. Per your suggestion, I attempted to increase the Charge limit from 12 aac however it stopped me at 14aac. I will have to wait and see if this does anything. Why is this setting required in addition to the Genset or Cord input settings?

Something seems to be amiss here. Both the new FX manual (page 31) and the old FX manual (“Mobile”, page 8) indicate the 2812’s default/max charging currents (from 120 VAC) to be 14 AC / 16 AAC. Assuming 90% charger efficiency, it would be very difficult to deliver 125 ADC using just 14 A from 120 VAC.

The two settings are required to avoid overloading the invert/charger’s rating. If the combination of pass-thru current and charger current exceed the input limit, then the FX will reduce input current to the charger to return to the input limit setting. For example, if the input limit was set to 30 AAC, and you were to be passing 20 AAC though the FX to downstream 120 VAC loads, then the maximum AAC current into the charger would be 10 A.

3. What do you suggest for a "Float Reset" voltage (default is 12.5) I am guessing that the charger will stay idle until it sees a reduction in voltage down to 12.5 and then it will float charge"

12.5 V is probably a good “Float Reset” point. A full 12 V AGM battery reads ~12.8 V, and the voltage will drop quickly once a load is applied. This “Float Reset” setting will attempt to power the downstream DC loads and keep the battery fully charged.

4. As a followup to the Float charge discussion, the programmed float charge time is it again a maximum or minimum time under what circumstances? and what is the optimal duration?

5. As a general question, is the float time subsequent to a major recharge different from the float time during a reset and if so, what are those times and which one am I being asked to program?

This may be a tough one, I think, as there are many variables. Is this a cruising issue or a question about what to do when tied up?

6. There is also a programming choice for the controller to be "on" or "auto" , what is the difference?

See #1 above. Also, see page 53 and 54 in the new Rev C Mate manual.

HTH… my brain hurts too…
Jim / crewzer
090805 System Configuration: 966 W STC (849 W CEC PTC) 48V PV array, FM80, 24V x 400 Ah AGM battery bank, FX2524T w/ BTS, Hub-4 & Mate; Link-10 w/ BTS, & E-Panel.
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Thanks

Postby lsilverman on Sat Mar 08, 2008 8:45 am

Allot to absorb.. I'll review my Q and A's and take another look at the manual.

This has been a tremendous help.

Thanks
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