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Old 06-28-2015, 03:11 PM   #1
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Amp hours / voltage reading question

I would like to get some information regarding what voltage reading I should be seeing for my set up.

I have a 2012 Monaco Knight with a Frigidaire residential refrigerator. I have 4 new (Dec 2014)Trojan L16 435 amp batteries wired in series and parallel, giving me 870 amp hours at 12 v, with 435 amp hours usable, if I understand correctly?
My inverter is a Magnum 2800, set up to bulk charge at 14.8, float at 13.3v, and equalize at 15.5v.
While dry camping over the last couple of months with varying quiet hours from park to park, I had a chance to see what the batteries capacity was. With the inverter running the frig and some lights in the evening, it would show that anywhere from 120 to 160 amp hours had been used in approx. 12 hours of use.
My Trimetric meter would indicate 80% to 85%, but my voltage would be in the 12.2v to 12.4v range. According to the chart that I have referenced, it indicates that 12.2 is at the 50% range??

I'm confused as to which to believe. I'm using nowhere near the 435 amp hours I thought I had, but am seeing low voltage readings at 160 amp hours. I checked the specific gravity today and all cells showed good. I also used a load meter on each battery, and they all show to be in good shape. In doing some research on this forum, I have read where some people have run similar set ups for 24 hours without charging, but I have not been able to see any reference to their voltage reading when they do
so. Is it possible to get more amp hours out of the battery bank, or am I expecting too much?



Any help in this matter would be greatly appreciated.
Thanks, Randy
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Old 06-28-2015, 07:54 PM   #2
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I'll just take a guess that you have too much battery and too little charger. L16's love 14.8 volts during adsorption. Even if you run your generator a lot u are probably not sufficiently recharging this battery bank. You probably could use about 900 watts of solar. Remember your Magnum only works when plugged in or with the generator running.
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Old 06-28-2015, 10:07 PM   #3
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You don't say how long you charge them. They need more then the 120 to 160 AH, to get them to 100%.

Have you watched the charger output, during your charging periods.

I read my Trimetric instructions many times. Somewhere in there is a caution not to set the meter to the manufactures specs on AH.

I used 600 AH on my 880 AH bank and it seem more accurate.

When in bulk charge you only get to 80% charge, the rest come in absortion mode.

Get the batteries, charged 100%, read the instruction book a few more times and try different settings.

Good luck
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Old 06-28-2015, 10:21 PM   #4
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How are you reading voltage of 12.2? Is this with no load after batteries have sat a spell without load?

ronspradley

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Old 06-29-2015, 12:39 AM   #5
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No, the 12.2 voltage reading is with a load of approx 8 amps. How should I be checking voltage, and how low is ok?

I was charging the batteries with the generator around 2 hours in the morning and around 3 hours in the evening. The Trimetric showed to be 100% and zero amp hours deficit. The charger was still in absorbtion mode , not float stage .
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Old 06-29-2015, 04:38 AM   #6
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You should check volts with NO load.


If in absorbtion mode, they are not charged to 100%. It takes a long time to get to 100%. I charge up to 80 to 90% to save fuel.


Change the bank capacity and reset the Trimetric.
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Old 06-29-2015, 08:21 AM   #7
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RP-

As TB suggests, review your Tri settings. It could be doing an auto-reset and giving a false 100% full indication when it is not full. Here are my lessons learned:

Trimetric settings – lessons learned

Have a hydrometer?
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Old 06-29-2015, 08:47 AM   #8
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How long are your charging your batteries and how many amps are you pumping back into them. I am more than willing to bet your not fully charging them.
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Old 06-29-2015, 09:15 AM   #9
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Voltage readings taken while there is a load on the batteries, are not a very meaningful indication of anything.

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Old 06-29-2015, 09:37 AM   #10
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Double check your battery data sheet for end point voltage and amp hour capacity as well as confirming the load rating.

Changing values for simple math.

Assuming 400 amp hours capacity at 8 hour rate then load should be 50 amps average to last 8 hours. 8x50=400.

Next end point voltage is usually 1.75 VPC or volts per cell which is 10.5 volts total.

You consumed about a third capacity so voltage looks close.

You were at 12.2 volts so a long way before dead.

You need to be fully charged and floating to actually get full capacity out and it does take some time to do that.

Not fully charging while continuing to cycle load may step the battery to a low operating voltage which may not be good.

Solar would add some charging to assist.
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Old 06-29-2015, 08:53 PM   #11
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Ok, I have read the Trimetric paperwork again, and I did not any reference to setting the AH in P3 lower than the manufacturer info, but I did change it from 870 to 550. This should allow the float voltage to 11 before it shows fully charged?? I changed the auto reset on the % full to off.
I also changed the absorb charge time on my Magnum from 3.0 hours to 2.5 hours.

The MH is currently plugged in to 50a as it is most of the time when I'm at home. Its floating at 13.1 and the Trimetric indicates 100% fully charged.

Let me know if I missed something or completely misunderstood.

Thanks
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Old 06-29-2015, 08:55 PM   #12
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Did some research, my meter is the 2020. It is explained in the instructions. Sorry.
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Old 06-29-2015, 10:32 PM   #13
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Quote:
Originally Posted by RPrince View Post
Ok, I have read the Trimetric paperwork again, and I did not any reference to setting the AH in P3 lower than the manufacturer info, but I did change it from 870 to 550. This should allow the float voltage to 11 before it shows fully charged?? I changed the auto reset on the % full to off.
I also changed the absorb charge time on my Magnum from 3.0 hours to 2.5 hours.

The MH is currently plugged in to 50a as it is most of the time when I'm at home. Its floating at 13.1 and the Trimetric indicates 100% fully charged.

Let me know if I missed something or completely misunderstood.

Thanks
If your 2 pair of L16's have a listed 20 hour combined rating of 870 ah (2x435) than that is what you should use.

Change the absorb time - why?

I have no idea what you mean by "the float voltage to 11 before it shows fully charged?" Do you mean 11 amps?

Turning the auto-reset to off is fine. Remember that when it goes above 100% you should do a manual reset (hold the reset button in for about 4 seconds) to recalibrate the capacity.

The Tri numbers in your original post looked ok. IMO, it was the voltage under load that you compared to the chart for voltage "at rest" that caused this confusion.

We can discuss this further via PM if you would like.
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Old 06-30-2015, 12:07 AM   #14
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I too would reset back to your actual battery capacity.

I would ignore your volt reading while under any load. If you want to play with this, turn off the main battery switch back by the battery compartment area. Then let things sit for at least an hour. Then look at the readings you get using a multi meter at the actually battery. Compare this to what you see see via the meter reading for voltage. (This will get you an idea of what the voltage is 'at rest'. Do this after running the fridge all night, and maybe leave on some lights too, to draw down the battery to simulate what you use overnight.)

And yes, to getting the batteries to full charge and reseting the meter to let it know that they're at 100%.

And, you are not alone on being confused. I have X's 4 L16 Lifelines, for 800AH. I use the Magnum BMK component with our Magnum ME2800, vs the meter you're using. (I wanted all Magnum when I upgraded the Converter/Charger, as figured they would play well with each other.). I also have 1200W of 48V solar panels, feeding down thru a Midnite Classic 150. When first getting out and using the new batteries, solar panels, and Magnum ME2800 - I kept getting pretty confused on the reading of SOC vs Voltage. It was some gents on the Escapee's board that suggested I ignore battery voltage reading while not 'at rest', as a reading under any kind of load would be meaningless. And, they too suggested that I re-read the manuals one more time, and to reset to 100% SOC when I know I have a full charge under my belt.

Pretty happy with the performance so far, and still learning too...

Best to you, and all,
Smitty
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