Solar taking forever to charge batteries, power disappearing

[DuneElliot]

System: 4 100W Renogy Eclipse panels connected to Renogy Commander 40A MPPT controller. 4 100AH batteries connected with 6AWG or larger. Four panels in series parallel configuration

It is taking ALL day to recharge batteries even from 80%

Yesterday I had my Xantrex 2000W inverter charging my electric toothbrush...nothing else (fridge is on propane so uses a tiny bit of 12V power)...during the day I lost 15% power by the time I got back to the RV after 6 hours. I know the inverter uses some power...but that seems like a lot during the day when my panels should be keeping up with minimal demand like that and feel lile they should accomplish charging the batteries AND have enough power left-over to charge my toothbrush and power the inverter.

I feel like I'm missing something. I am using the default settings on the MT Tracer meter that controls the controller paramters for charging. Should I be changing the parameters for AGM batteries to get more out my panels?

 

[tx2sturgis]

It could be the percentage numbers are not calibrated for your battery bank. What does the voltage display show at 2PM or 3PM in the afternoon on a sunny day?

BTW a 2000 Watt inverter standby losses are almost certainly higher than the drain from the toothbrush charger.

You might need to buy a smaller pure sine inverter (around 150 watt) for powering those smaller loads more efficiently.

 

[DuneElliot]

I have a smaller inverter and have mostly been charging stuff in the truck like camera batteries and computers when I am driving. I have a 12V 4 slot USB charger in the RV for those things that can use it like phones and tablets. I might pick up another small inverter for things can don't have a USB cable to charge with.

I will check the voltages at that time of the day in the next day or two but when I have checked it before it looks like around 36.5 volts which at 18% efficiency from these panels (according to website) should be accurate.

I will look again later but have no cell service where the camper is parked so might be a day or two.

 

[gapper2]

AGM brand and model nos.   Most AGMs require large charge rate on occasion.

 

[tx2sturgis]

Are your batteries 6v, and also in series parallel? (or 4, 12v in parallel) Yielding 12v?

They should have a battery voltage display of around 12.5 to maybe 14.1 or so...They should settle at 'float' voltage at around 13.8v.

Or are those batteries in some other configuration?

The 36.5v is, I think, the reading of the panels.

 

[jimindenver]

This is why I do not like the accepted 1 to 1 ratio suggested for watts to Ah's. I first heard that that was what was needed to equalize and that is the only reason I have ever seen for using that ratio. In my experience is that it is painfully slow to watch a 1 to 1 system charge a big bank that is really hungry. So slow that in the winter it may take a few days to get caught up, even longer if you are still sing power. Once a system gets behind the batteries do not get to full for a extended time and causes progressive loss of capacity. Some people that use generators seek out hook ups every few weeks so that they can get the long charge and the batteries back up to full.

Right now use as little power as possible to let the bank get fully charged. Once it is charged equalize it to minimize any damage done by having them under charged. A boost from a generator pushing your converter or a charger may help get it done sooner in the day. Also check the settings on your controller to make sure they are what you think they are.

 

[John61CT]

It is taking ALL day to recharge batteries even from 80%

What gives you that impression? In other words what tools are you using to estimate SoC?

What brand/model batts, how old, estimated cycles?

Have you double-checked all your connections?

What are the setpoints on the SC, when does it go from Absorb charging back to float?

Do you have a ballpark on your average and/or peak AH per day?

 

[DuneElliot]

Batteries are 12V Mighty Max AGM in parallel. They are almost new and have never been discharged or used until now.

So far I have not got lower than 73% capacity...so half of what is technically available is still left if I keep eith the 50% minimum.

I am relying on my Trimetric battery monitor to tell me where they are which was calibrated when I knew they were full. Also my Tracer meter tells me in and out volts. The 36.5v is from the panels to the controller.

I am potentially think to order another two panels while they are still making the same model so nothing is mismatched

 

[tx2sturgis]

Ok...are you sure that the Trimetric monitor is set for AGM? I assume it can be programmed for AGM setpoints.

Also, what are you running at night that is pulling the percentage down to 73%?

We do need to get the raw voltage reading of the batteries, preferably in the morning before the sun hits the panels, and then in mid-afternoon. Then we can see if those readings for percent of charge are somewhere close to this information:

 

[DuneElliot]

Okay. And how do I do all this...I don't have a meter or the means to be getting one. I can tell you what the Tracer meter says, and what the Trimetric meter says is coming and going out.

Yes, I believe I set the Trimetric up for AGM batteries and 400AH but will check. Will be out of cell service until tomorrow as we camped in the bottom of a canyon.

 

[John61CT]

I am relying on my Trimetric battery monitor

Excellent choice, congrats.

Are you aware that this can control up to 62A actual charging output using their SC-2030 controller(s)?

Not MPPT, but actually delivers most excellent service where it counts, coddling your bank for maximum longevity.

Batteries are 12V Mighty Max AGM in parallel. They are almost new and have never been discharged or used until now.

I am not sure if these are what I would call "true deep cycling". Do you have data on "lifetime cycles vs DoD" or if the mfg specifies a breaking-in protocol?

It may be worth doing a 20-hour load test AH benchmark so you can accurately calibrate the Trimetric as capacity walks down over time.

Did you purchase from a source woith a generous returns policy?

I am potentially think to order another two panels while they are still making the same model so nothing is mismatched

That would be smart in any case, my advice is always to install as much solar as you can get on the roof in a mobile context.

 

[tx2sturgis]

Okay. And how do I do all this...I don't have a meter or the means to be getting one.

There should be a voltage readout available on the monitor.

Either stepping thru the readings, or in a menu somewhere.

If not, then it will have to wait until you can get a digital volt meter.

 

[John61CT]

I have a smaller inverter and have mostly been charging stuff in the truck like camera batteries and computers when I am driving. I have a 12V 4 slot USB charger in the RV for those things that can use it like phones and tablets. I might pick up another small inverter for things can don't have a USB cable to charge with.

My preference with deviced that actually use DC, is to charge / power them directly from my bank. Usually a cheap DCDC converter will do if the mfg doesn't sell a "car adapter" for their product. Biggest challenge is the plug size and polarity, but you should have a DMM voltmeter, and there are cheap "universal kits" available for tips.

An inverter is far less efficient, one more expense and point of failure.

But none of that should be a factor wrt your OP problem.

I will check the voltages at that time of the day in the next day or two but when I have checked it before it looks like around 36.5 volts which at 18% efficiency from these panels (according to website) should be accurate.

Don't worry too much about voltage from the panels.

IMO the weak link is that controller; others consider it fine, but monitor its total AH charging output to the bank.

And again, verify wiring connections, proper crimps etc.

 

[Blanch]

Maybe this is a stupid question, but where are you? My solar system was almost useless when I was camped near a wildfire. The smoke must have diminished the amount of power available from the sun. So, could there be a problem with your location? Did this system properly charge your batteries on previous boondocking trips?


Sent from my iPhone using Tapatalk

 

[tx2sturgis]

Maybe this is a stupid question, but where are you?

Wow! Good catch...not a stupid question at all....she did say she was camped in the bottom of a canyon...


She might not be getting a full day of charge...


Duh!


:blush:

 

[LWalker]

In regards to inverters... I've learned that smaller in not necessarily better (more efficient)

I have a 600w pure sine and uses less energy (with no load) than my cheap 150w inverter (with no load as well)

So basically quality (price) matters.... way better to use my 600w even for a small load than my 150w inverter

Sent from my SM-G930F using Tapatalk

 

[DuneElliot]

Trimetric is not programable for AGM but the MT Tracer is programmed for Sealed. Trimetric is set to call the batteries charged at 14.3V and it is saying 98% full...has been since I got back at 2:30pm. Currently pulling in 38.5v and 1.8 A at 4pm from solar panels to controller. Batteries read 13.9V and 2.7 A according to Tracer meter. No output as everything is off.

Flashing lights on controller which supposedly mean batteries are full but Trimetric disagrees.

 

[DuneElliot]

I'm in Utah, near Vernal. I say Canyon but it is along sside the Green River...very very wide and not very deep canyon...full sunlight from dusk to dawn.

This is my first trip out period so haven't used the system before, boondocking or otherwise.

I'm actually thinking my inverter is way too big for what I need...2000W for basically charging a couple of things, a TV that says 28/48W (not sure which as the TV says both) and my PS3. Everything else can be plugged into 12V.

So what is wrong with the controller I have? I wanted an MPPT controller so I could enlarge the array if necessary and manke best use of all available sun and power

 

[regis101]

disconnect two of the batteries for awhile. This will put you at the 2:1 ratio . See how things go. 400ah is a lot. A 10$ VOM is better than nothing

 

[tx2sturgis]

Trimetric is set to call the batteries charged at 14.3V and it is saying 98% full.

This is why I wanted to see the voltages. I will defer to John and/or Jim on this but I think that value is set too high.

In other words, the monitor is reporting a lower state of charge than what you really have available.

Unless these guys disagree, I would try setting the full charge voltage reading (for 100%) at something a bit less.

John? Jim? What say you?   :huh: