BajaNomad - One more AGM ? UPDATE and Controller issue?

One more AGM ? UPDATE and Controller issue?

Santiago - 4-1-2018 at 05:30 PM

Small system in off grid cabin in Bahia de los Angeles. Two 190 watt panels, thru Xantrex C60 controller to four 12v Deko 105AH AGM batteries. Xantrex 1500 watt modified sinewave inverter/charger to power center. The batteries will be new and a BTS will be used. The cabin is shut down for 4 to 6 months at a time; what would be the best way to leave the system when gone?

I have been told to bring them to full charge and turn everything off. What say you?

May 30:
Installed the 4 105, 12 volt AGMs on Monday morning with temp sensor. The Tri-Metric meter showed 100% charge.

The next day, at about 3:00 in the afternoon, The charge controller showed a solid green light (fully charged) but the Tri-metric showed only 50% charged and the amps were a negative 6 amps. At 3:00pm, the only draw on the system was the router and modem. It dawned on me I forgot to change the router settings which I did: Bulk at 14.5 and float at 13.5 per Deko specs.

I go to the panels and notice they are little dirty and clean them. It change to positive 7 amps, still not much for that time of day. AT 4:00pm I hook the Honda 2000 up to the Trace inverter/charger and it start dumping 67 amps back into the batteries, bring them to 80% by 6:00. Out of politeness to my neighbors, I turn the genny off as c-cktail hour was well underway.

At 4:00am this morning, they were at 70%.

From this info, do I have a bad charge controller, are the panels weak? If by early afternoon the percentage charge is not well on its way to 100%, then I should run the genny to get there, correct? The panels, by the way, are on a flat roof and not tilted, but always worked with the four 6V golf carts, also 440 AH.

[Edited on 5-30-2018 by Santiago]

BajaBill74 - 4-1-2018 at 06:23 PM

Leave that system with a really good guard dog.

[Edited on 4-2-2018 by BajaBill74]

PaulW - 4-1-2018 at 07:15 PM

If your controller has the smart chip that provides a 3 stage charger/maintainer function then leave the batteries connected. If that controller does not have that capability the buy a 3 stage unit and leave the batteries connected directly to the panel. The size (amps) of a standalone 3 stage controller needs to be determined by calling the battery manufacturer. For my single 105AH battery the battery guy said to get a 10A max unit.
The above info was given to me by the Concord engineer.

Mendodoc - 4-1-2018 at 08:51 PM

I use the same charge controller for 770 watts of panels, and (12) 6 volt Trojan T-105's with the 2400 watt Xantrex inverter and I have left the system to it's own resources for months on end. Last saw the cabin 5 months ago but just had a friend check the system for me and the Tri-metric meter is reading 28 volts (24 volt system obviously).
Just make sure that ALL your connections are clean, and tight, and you shouldn't have any issues...

[Edited on 4-2-2018 by Mendodoc]

DanO - 4-1-2018 at 10:14 PM

I switched to AGMs awhile back and because they lose very little charge over time I'm comfortable taking them offline when I'm gone. YMMV.

woody with a view - 4-2-2018 at 07:13 AM

What DanO said.

larryC - 4-2-2018 at 07:37 AM

I agree with what PaulW said. AGM batteries like to be charged with 5 to 10% of the amphour capacity of the battery bank so in your case with 420 amphour bank somewhere between 20 and 40 amps at 12v. Your 2 190 watt panels probably put out about 22 to 24 amps so you are right in there amps wise. Just set your controller to the charge voltage that the battery manufacturer recommends, connect the temp sensor and leave them hooked up while you are gone. That is what I do and my batteries are 7.5 years old and still going strong.

Batteries that sit uncharged for extended periods of time will start to form sulfate on the plates which reduces their life span. You can see when sulfation starts to happen because the battery starts to bulge on the ends.

[Edited on 4-2-2018 by larryC]

Cancamo - 4-2-2018 at 07:57 AM

As long as you've got someone checking the water level, and the controller goes through the cycle, (charge, bulk, float), leave them connected.

Bob and Susan - 4-2-2018 at 01:10 PM

Quote: Originally posted by larryC

...You can see when sulfation starts to happen because the battery starts to bulge on the ends.

batteries bulge because of gas not venting correctly...

my advice...charge them then disconnect them

reconnect them when you get back

its a fire danger to leave them connected when you are gone long periods of time...the cables can actually vibrate loose and spark

you don't want that

or some field mouse will eat a hot wire and ground it

willardguy - 4-2-2018 at 02:25 PM

I vote for bringing em up to FLOAT ( battery mfg specs) and disconnecting :yes:

[Edited on 4-2-2018 by willardguy]

Santiago - 4-2-2018 at 03:22 PM

the Xantrex C60 is a 3 stage charge controller - I think that is what is meant by "Smart chip"?

willardguy - 4-2-2018 at 03:30 PM

Quote: Originally posted by Santiago

the Xantrex C60 is a 3 stage charge controller - I think that is what is meant by "Smart chip"?

your controller has no idea what your battery bank consists of, obviously the default set points have to be conservative....this is why most batteries end up under charged. listen to the battery manufacturer!

rts551 - 4-2-2018 at 04:27 PM

The xantrex c40 and c60 controllers have to be set for your batteries. Jumpers and dials inside. Read the instructions on how to set for AGM batteries per the battery manufacturer settings. They are a three stage controller...but the first 2 stages are manually adjustable.

larryC - 4-2-2018 at 06:35 PM

Quote: Originally posted by Bob and Susan

Quote: Originally posted by larryC

...You can see when sulfation starts to happen because the battery starts to bulge on the ends.

batteries bulge because of gas not venting correctly...
That statement is completely wrong. Google it if you still have doubts.

Santiago - 4-4-2018 at 05:50 AM

Deka provides a tech bulletin that sets the charge parameters for these batteries at the bulk, absorption, float and equalization stages. The C60 has two adjustable dials: the Bulk can be set from 13.0 to 15.0 volts and the Float from 12.5 to 14.5.
The Float parameters given by Deka is between 13.44 and 13.56volts - am I to assume that this is what I set it to while at the cabin and on leaving? By the way, I have the charger set so that equalization charge is manual, not automatic.

woody with a view - 4-4-2018 at 05:59 AM

Set it and forget it. I was under the impression agm batteries dont require equalization. Am i wrong again?

larryC - 4-4-2018 at 07:48 AM

Usually you set the float about 1v below bulk.

Woody, agm batteries can be equalized but it is usually a fairly mild equalize compared to a FLA battery. Again follow the manufacturers recommendations. AGM batteries are sensitive to over charging and if you screw up and let some of the electrolyte boil out there is no way to replace it and the battery life is shortened.

Bob and Susan - 4-4-2018 at 01:11 PM

you mean if you overcharge...the fluid inside expands and the battery explodes? seems pretty dangerous

disconnect the batteries if you are not home

larryC - 4-5-2018 at 08:07 AM

Bob, I have no idea where you come up with this stuff. AGM batteries are also sometimes called VRLA (Valve Regulated Lead Acid) batteries which means they have valves/vents built into each cell and if the battery is overcharged or the internal pressure of the cell is too great the valve will open and vent the pressure to the atmosphere. FLA (Flooded Lead Acid) do this all the time while being charged those are the bubbles you see in the cell during the charging process but the fluid in an FLA battery can be replaced periodically during maintenance the advantage to using an AGM battery is that no fluid needs to be replaced because if the proper charge voltages are maintained then no fluid is lost . That is what makes AGM batteries a good choice for a solar system that is not maintained but once or twice a year.
Hope I explained it clearly.

Santiago - 5-30-2018 at 06:06 AM

Update on first post, above

woody with a view - 5-30-2018 at 10:59 AM

My guess is your panels are not putting enuf juice into the bank. Ad two more and you’ll be happi(er). I’m having the same issue. Need more panels.

ncampion - 5-30-2018 at 12:07 PM

Calculating for 10 - 15% loss from the panels, as Larry said you should be putting out around 20 amps (14.5v) by midday. The Xantrex C60 is not an MPPT controller so it is important that the panel voltage output is appropriate to the battery bank voltage. Check that the panels are wired correctly (parallel if Pmax is around 17 v.) the controller will "down size both the voltage and amperage to match your settings so you may not realize the full 20 amps however it should not be anywhere what you are seeing. I suspect the controller is OK, just need to be sure everything is wired correctly. If you're in BoLa you might have Larry take a look. Sorry Larry, don't mean to volunteer you services but I know you know what you're doing.

willardguy - 5-30-2018 at 12:28 PM

ugh, with only a very small load your new battery bank fell from 100% (12.7) to 50% (12.4).....does the tri-metric attest to these voltages (or close)? solid green light on the controller would show it in float, double check bulk settings. good luck!

[Edited on 5-30-2018 by willardguy]

Santiago - 5-31-2018 at 05:56 AM

I had to re-set the Tri-Metric and according to their web-site, it can take a couple of charging cycles before it starts to accurately report the "% Charge". It is accurately reporting the voltage, I think. I got as high as 18 amps going into the bank mid-afternoon so I think I got that part worked out.
Initially, my bank was only 220 AH so the two 195 watt panels were fine, but a few years ago I added another 220 AH but never any more panels. On most trips, the system would go to float by late afternoon so I figured I was still OK. LarryC stopped by (thanks) and recommended a couple more so will do that next trip.