Battery s

Gregaba · February 2023

Brand new to solar.

I decided to give this a look at after being interested in it for about 20 year's. I never did check into it much but thought it was a good ideal.

I bought a 400 watt unit for experiment and just got it hooked up.

It is a Renolgy 400 watt kit along with a Epever 10415AN CC and a Renolgy 3000 watt inverter.

I have 2 of Renolgy 200 AH agm battery s hooked in parallel.

When I turned on the inverter and hooked a .04 amp LED light up to it for a load my battery % went from 97% to 87% right away.

I have it running for about 3 hour's now and my % is dropping fast, at least to me.

1:46 pm=85%

2:07 pm=68%

3:20 pm=54%.

Going to go out and turn it off as I don't want to ruin a battery.

My question is should I have bought these up to full charge with my charger before I tried to us it?

Thanks

Greg

littleharbor2 · February 2023

Clearly something is wrong. It would have been proper to fully charge your battery first but with that tiny load something is not right. Could be your inverter has an especially high idle consumption. Also voltage based battery monitoring is not at all accurate. I would turn off the inverter and FULLY charge your batteries. Then try again.

Gregaba · February 2023

Thank you

I will do that today.

Greg

Gregaba · February 2023

Starting to think that trying solar was a bad decision.

I charged both battery's today and changed my charge controller. I changed from the Epever 100 amp to the Renogy 40 amp.

Both new but I wanted to eliminate the CC as a problem.

I am going to leave my 40 watt led on all night and recheck my battery voltage. I will just take a chance on ruining one of them.

If that doesn't work I will install an old 600 watt inverter I bought in the 80's to run tools when I was on a job with no electricity and see what happens.

If that doesn't work I think I will just call it a learning experience and move on.

Greg

Marc Kurth · February 2023

The first step is to start with a fully charged battery bank. How are you determining that the batteries are fully charged? DIY solar is like many things: You need to dive pretty deep into learning about the subject. It is easy to give away a generator that won't start because you didn't know that the choke had to be set.

Gregaba · February 2023

Fully charged them today.

The apps have a soc reading in them. I have been keeping track tonight and after 2 hours of dark it was only down to 75%,

In the hour since then it has only dropped to 73% which is encouraging. In the morning I will check the voltage and compare it to what it was today and see what my % drop really is.

Thanks for the reply.

Greg

Marc Kurth · February 2023

Greg,

Do you have a way to measure the actual load on the batteries? (light plus inverter) It sounds like either the inverter has a huge overhead or you have a battery problem. Before giving up, I would find out what the actual load is and try it on one battery at a time.

Marc

Gregaba · February 2023

No way to measure load. I did check my voltage this morning with the app showing 63% soc the battery's measured 12.54 v.

The app showed 4% use from 5:30 last light which is better.

I am sure the inverter is drawing a big load as it is the renogy 3000 watt inverter.

Today I will separate the battery's and try one tonight and the other the next night.

Hope it isn't one of them as they are new.

What would I need to order to measure the load?

Thanks

Greg

BB. · February 2023

The Renogy 3k Watt inverter draws around 2.5 amps (no load):

https://www.renogy.com/content/RNG-INVT-3000-12V-P2/INVT-P2-Datasheet.pdf

2.5 amps * 12 volts = 30 Watts

I am guessing that your 0.04 amp LED load is at 120 VAC:

120 VAC * 0.04 amps = 4.8 Watts
4.8 watts / 0.85 AC inverter eff = 5.6 Watts 6DC load
5.6 Watts DC / 12 volts = 0.5 amps DC load from LED

Your total battery load would be:

34.8 Watts / 12 volts = 2.9 amps nominal
2.5 amps + 0.5 amps = 3.0 amps nominal load (adding current with load efficiency)

Battery wise:

400 AH (at 12 volts) / 3 amp load = 133 hours (to zero State of Charge)
100 Percent * 1/133 hours = 0.8% per hour of battery usage

A 3,000 Watt inverter on a 12 volt battery bank draws max current of:

3,000 Watts * 1/0.85 AC inverter eff * 1/10.5 volts "dead battery alarm" = 366 Amp max draw (2x that for "surge")

Large inverters on 12 volt battery banks is a copper wiring nightmare (thick, heavy, expensive copper cables and connections).

At 3,000 Watts, you would probably not even get 1 hour out of your 2x 200 AH @ 12 volt batteries...

For a "nominal" off grid home/cabin design, would be suggesting a 24 or 48 volt battery bank to keep DC currents "reasonable"...

And for a normal rule of thumb, a 12 volt battery bank should be around 100 AH per 250 Watt of AC inverter load... OR:

3,000 Watts * 100 AH * 1/250 Watts = 1,200 AH @ 12 volt suggested minimum battery bank size (for lead type batteries)

Your smaller 400 Watt inverter probably drew around 1.0 amps no load...

The math, while not great, does not really show why your battery SoC readings are "crashing" so quickly... Should be dropping at less than 1% SoC per hour with your inverter+LED loads...

If you want to do a bit more detailed review/understanding of your solar power system, an AC+DC Current Clamp DMM (Digital Multi-Meter) would be a good tool to have:

https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (example of "good enough" inexpensive meter)
https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (mid-range priced meter)

Very simple to use... Just "clamp" the meter around one cable and it will show the current (for DC current measurements, you do need to "zero" the meter). Very safe/easy/quick.

Note there are AC only, and AC+DC current clamp meters... AC only meters work fine for 120/240/etc. VAC work--But working with batteries/DC power systems, an AC+DC clamp meter is much more useful.

-Bill

Gregaba · February 2023

Thank you bill. I printed your answer out so I can reread it.

I did find one problem while just out there just now, I removed the 10 amp fuse from the pv line and my charging rate picked up.

I was just getting about 50 watt's of charge from the panel's and am now getting 151 w and 6.97 amp's from the panels.

Still will have to find out why either cc shows such a fast rate of charge and discharge.

Changing from 12 V to 24 was planned for the future but will hold off because my inverter is only rated for 12V. Wish I would have known that before I ordered one.

I have ordered the AC-DC clamp meter.

Thanks again

Greg

Gregaba · February 2023

Yesterday while waiting for my meter to come in I went out and changed the way I have my batterys hooked up.

I was running both the + and - off one battery.

I changed it up to run the+ from one battery and the - from the other battery to my cc.

I am charging it up today and hope it make's a difference.

Meter will be in tomorrow and I will be able to check my load then.

Greg

Marc Kurth · February 2023

While you are waiting, disconnect the batteries after they are fully charged, and let them stand for at least a couple of hours. Measure the voltage of each battery.

Marc

Dave Angelini · February 2023

The by far biggest problem we see, is how you are measuring Soc and how you calibrated Soc. Do not place much faith in it until you know how to do this!

Gregaba · February 2023

Maec

I will do that. Should tell me if I have a week battery.

Dave

I was using the Epever app to tell my SOC in the beginning. I have a battery charger that tells me the SOC that I am using now.

I also found a web site that gives me theSOC by battery voltage.

I did notice that with the way I have hooked up my batterys to the CC that it is taking a lot longer to bring them to 100%.

May be a good sign.

Greg

Marc Kurth · February 2023

Greg, Dave's point above is critical to understand. I cannot count the number of battery monitoring systems that have helped to destroy expensive lead-acid battery banks. They have to be calibrated on a regular basis.

One AGM battery manufacturer flatly says that your battery bank is fully charged ONLY when it will accept less than 0.5 amp per 100 ah of its C/20 rating while charging at the Absorb voltage. (1/2 of 1%) Example: A 12v, 400 amp hour battery bank is fully charged only when it draws less than 2.0 amps while charging at 14.4v. Terminating charging before reaching this point, will result in undercharging and sulfation. Other AGM manufacturers have different numbers, but I see around 1% (1 amp/hundred) most often.

Remember that a sulfated battery bank will reach this low current more quickly because it cannot absorb a full charge. Typical Absorb times are 2-4 hours depending on how deep the discharge was. You will often see the internet megaphone screaming about avoiding overcharging AGM batteries, but 99% of the early battery demise that we see is caused by sulfation caused by undercharging. A quick way to spot sulfation is a low standing voltage after fully charging. (Should be measured 4+ hours after charging.)

Gregaba · February 2023

I just went out and disconnected my battery's and will let them set and then remeasure.

I left my charger on all day yesterday and last night.

Yesterday the charger showed 100% charge at 5 PM so it should be fully charged this morning.

When I unhooked it was showing that it was charging at 1.61 amps.However the SOC on the app was showing 61%, so I am coming to the conclusion that the SOC shown on the app is all BS.

I will just go on my voltage reading's from now on.

The battery's are new and have about 2 week's time on them now.

Well be glad when I learn some more about how all this work's.

Greg

Marc Kurth · February 2023

Gregaba said:

I just went out and disconnected my battery's and will let them set and then remeasure.
I left my charger on all day yesterday and last night.
Yesterday the charger showed 100% charge at 5 PM so it should be fully charged this morning.
When I unhooked it was showing that it was charging at 1.61 amps.However the SOC on the app was showing 61%, so I am coming to the conclusion that the SOC shown on the app is all BS.

It was showing 100% last night at 5:00 PM, then read 61% this morning after running all night?

What is the charging capacity of the charger?

What are you seeing for an Absorb voltage?

What was the voltage being sent to the battery bank when you saw the 1.61 amps?

Gregaba · February 2023

Marc

!00% was with the battery's fully charged. Did not run a load all night [inverter turned off] and left the charger in trickle.

The app showed 61% this morning but when I restarted the app it showed 100% just before I disconnected the battery's. .

The charger is a Schumaher that charges sta, agm,or gel. Max amps are 15.

It has a power sport or auto marine choice. I use the power sport because it will charge slower.

Have never seen an aborb on the app. It just all ways says normal.

The 1.61 was with the charger and running off the pv did not think to check the voltage but it was real cloudy with snow on the ground.

By the way thanks for taking the time to help me with this.

Greg

Gregaba · February 2023

Just re hooked up my battery's.

They measured 13.05 volt's on each battery.

The system is putting out 20.89 volt's, 1.89 amp's and 39.51 watt's.Sunny with some shade on my panel's.

I would think this mean's my battery's are good.

Restarted the app and with 13.05 volt's it is showing 70% capacity so I guess the app is no good.

Guess I will hook up my 40 watt light up tonight and see where I am in the morning on voltage.

Greg

BB. · February 2023

Hmmm... Maybe not(?).

Generally for AGM type batteries you want to see ~14.2 to 14.4 volts "held" for ~2-4 hours when charging...

ANY SHADE on solar panels will dramatically reduce their output current.

At high noon, with battery bank "under" 14.0 volts, 400 Watts of panels (pointed at sun, no shade, working charge controller) should be a (maximum) of:

400 Watt array * 0.77 panel+controller deratings * 1/14.0 volts charging = 22 Amps DC Charging current to battery bank

Or roughly 11-22 amps "typical" charging current ("average day", discharged battery bank)... 2 amps on a sunny day into your (probably not fully charged) battery bank.

Regarding your solar panels... If you have 4x 100 Watt panels (Vmp~18 volts)--You can wire all 4 in series (for around 60-80 volts Varray)... With your Epever 10415AN charge controller--That would be a "nice" configuration (all panels in series). The higher voltage array allows you to use longer cables from array to charge controller--So you can put the array in full sun, and the battery+equipment in a shed/shaded area).

Anyway, you need to get a lot more solar charging energy into your battery bank to be successful... 2 amps is a 0.5% rate of charge.

Ideally, a 10% to 13% rate of charge. You can "get away" with 5% rate of charge for light loads/weekend/emergency backup power:

400 AH * 10% = 40 Amps "rated" charging for full time off grid
400 AH * 5% = 20 Amps "rated" charging for backup/weekend/emergency use

A solar array for 10% or 13% rate of charge (usually minimum for full time off grid) to upwards of 20/25% rate of charge (depending on your average weather, how many AH/WattHours per day for loads, etc.):

400 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 748 Watt "nominal" array
400 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 973 Watt "typical cost effective" array

One way to understand how fast (or slow) 2 amp rate of charge is:

2 amps / 400 AH capacity = 0.005 = 0.5% rate of charge

If you get 5 hours of "good sun" per day, that is:

0.5% * 5 hours of sun = 2.5% per day charging (excluding battery losses) for a 400 AH battery bank... This is not enough to keep a battery bank "happy"... For an "off grid" power system, 10% rate of charge or 50% bank capacity per day is pretty much the minimum needed....

And we have not talked about how much sun you have (location, seasons), and what power you will need (Watts of power * Hours per day)...

-Bill

Gregaba · February 2023

Bill

Thanks for the answer.

A lot to go over.

I live in southern Oklahoma and get 4 1/2 to 5 peak hour's a day of sun.

When I said my panel's were partially shaded I meant that they are in a temp location and the shade is the bare branches from a tree and cover about 6x2 inches of 1 panel and 4 x2 inch's of another panel.

I guess tomorrow I will disconnect my battery's again and charge them with the charger set on automotive instead of atv.

The charger shut down with 13.7 volt's and said 100% charge.

I did have my panels wired in series at first but with the fluctuation in my system I wired them in parallel.

I will change that around in the morning. I was getting 97 volt's out of them in series but don't remember the amp's.

Thanks again for all the help.

I hope to get this whipped by at least the year 2525.

Greg

Gregaba · February 2023

Had to work yesterday, had to do an emergency service call 180 miles away so got in late.

Wired my panels in series this morning and moved them to a sunnier location.

I now have both battery's disconnected and am charging each one separate at a full 15 amp's.

I will charge them up to the full 14.7 V each and give them another try tomorrow night and see if I have a big drop or not.

Greg

BB. · February 2023

AGM batteries should be around 14.4 volts max (held for 2-4+ hours).

14.7 volts is usually a bit high. You don't want the batteries to gas and vent... That shortens AGM battery life.

Looking around and found this:

https://m.media-amazon.com/images/I/91f0wZKgDgL.pdf

14.7 or 14.8 volt charging maybe the first time... While you are monitoring (watch that battery does not overheat, you do not hear gassing, etc.)... And they recommend recharging every 3 months (if stored at 100%, and left sitting without charging/float charging).9

EQ charging for AGM is that 14.2 volts held for 8-24(?) hours... This is to ensure that all cells are fully charged (not one cell at 100%, another at 80%, etc.). You may want to do this once every six months (my guess)--But it is not really necessary as AGMs in general cells stay pretty balanced (all cells about the same state of charge).

I would "auto charge" with 14.4 volts as a starting point.

And solar electric panels... Almost any shading (even just one cell) can cause 50% loss of charging power on that one panel (or even more--Depending on array wiring, solar controller type, etc.).

-Bill

Gregaba · February 2023

Thank you

Neither battery would take over 13.8 V charge.My charger is automatic and I can't set the charge amp's like I could with my old one.

I am not to concerned about the charge rate from the PV array as I don't expect much with my temp setup. I am more worried about the fast discharge when I try to use it over night with a 40 W load.

I bought this set up to learn on before I install a bigger system,but I wanted to make sure I could get this cheap unit running before I spent a lot of money.

Looks like I am getting an education.

Very frustrating.

Greg

BB. · February 2023

Battery voltage (charging, discharging, resting, etc.) is based on current (plus or minus), state of charge, and to a degree temperature... As well as age, any sulfation, etc...

An example of what an FLA battery graph looks like:

Image: https://us.v-cdn.net/6024911/uploads/attachments/6285/3535.png

Image: https://us.v-cdn.net/6024911/uploads/attachments/6285/3536.png

Marc Kurth · February 2023

At the risk of being repetitive, all AGM batteries are not the same:

Fullriver charging: 14.7v Absorb and 13.65v Float @ a maximum initial charge rate of .25C to .30C. Chronically charging at lower than the specified values will result in sulfation and early battery demise.

Concorde AGM: 14.3v Absorb and 13.3v Float (+/- .1v) @ a maximum initial charge rate of 3C to 5C. (.2C Minimum) Exceeding these values will gradually dry out the batteries.

Image: https://us.v-cdn.net/6024911/uploads/editor/12/tzkjrrlnsb44.png

I can tell you from experience that operating outside of these parameters for long periods will shorten the battery bank lifespan.

Marc

Marc Kurth · February 2023

Gregaba said:

Thank you
Neither battery would take over 13.8 V charge.My charger is automatic and I can't set the charge amp's like I could with my old one.--------------------------------------------

Your batteries will "take" whatever voltage that your charger gives it. If you saw a max of 13.8v, that is all that the charger supplied to it.

In a simplified form: You PUSH voltage into a battery and the battery PULLS amps.

Your batteries need to see 14.xx volts continuously for 2-4 hours (depending upon how discharged they are) in order to properly charge. Read the label on the batteries to find the actual value of 14.xx is.

Marc

Gregaba · February 2023

Thanks for the info.

After charging up the battery's day before yesterday I saw that they went into float stage for the first time. Only saw boost stage when I first installed them. Have never seen absorb stage.

The battery's showed 14.7 volt's while in float stage so I decided to leave them alone for a couple of day's before I put another load on them.

Hopefully they will start working like they should. I really hope I don't have a big fast draw down on the battery's when I check them again.

If I do I will contact Renogy and see what they say.

Greg

Marc Kurth · February 2023

Greg, please read the info above. Float should be in the 13's. Floating at 14.7v will certainly (gradually) destroy your batteries.

littleharbor2 · February 2023

When the charge controller transitions from absorb to float 14.7 will likely show briefly but should drop to the float voltage setting. If it remains at 14.7 there is a problem. Additionally when you lose solar power at the end of the day your voltage will again settle to somewhere in the high 12's till your loads start pulling current from the full batteries.

Gregaba · February 2023

I may be making some progress.

Yesterday with my batt's fully charged I put a 12.2 amp load on the system and left it on all day. It showed full charge all day as it was a nice day.

At 9 PM I lowered the load to the single 40 watt load and left it on all night.

I got up before the sun at 6:30 AM and my app showed 48% SOC but I checked my batt's with my meter and they showed12.48 Volts which is close to 80% SOC according to my chart.

I have decided that these app's are not right and not even close on the SOC reading but will say that their battery reading's are right on as to what is left in the battery.

Will play with it a while gradually increasing the load each night and see what happens.

Again thanks for everyone taking the time to help me with this.

Greg

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