Batteries Not Keeping Up

[HARG Hunter]

I may have already solved the issue, but just looking for ongoing input on my system that I'm building.

Initial Set-up:
(1) Renogy 100w Mono Panel
Renogy Rover Elite 20a MPPT C.C.
1000w Inverter
(2) Marine Deep Cycle batteries (Estimated they are 50ah batteries each)

I was having no problem getting those charged up to 13.5-14+ Volts
Several factors: In summer the sun was rockin', and there were very few shady days leading up to the times we were at the cabin. The total draw we have is typically under 100 watts at a time for very short spurts. We are only at this cabin every other weekend, so it has plenty of time to charge things up between visits.

THEN, I added (3) Mighty Max 30ah batteries. This brings my battery bank up to approx. 200 ah.

Since then, the system struggles to stay at 12.5V or more. Typically it sits between 12.0V - 12.3V
I assume several things. First, we are now in the fall season in Wisconsin. The sun is lower (Which I did adjust the panel angle to maximize exposure).
We've had more frequent clouds, plus I feel the single 100w panel just can't keep the bank charged.

I just bought another Renogy 100w panel.
I'm hoping that when I get this added, the battery bank will get back up to where we need it.

This will be the system when I get that panel hooked up:

(2) Renogy 100w Panels
Renogy Rover Elite 20a MPPT C.C.
1000w Inverter
(2) Marine Deep Cycle batteries (Estimated they are 50ah batteries each)
(3) Mighty Max AGM 30ah Batteries

Just hoping you all can look at my system and pick it apart for me in case there is a glaring imbalance or something.
I truly think that when I doubled the size of the battery bank that I wasn't getting enough charge from the single panel.
A combo of that plus the diminishing sunlight conditions aren't allowing the battery bank to get the charge it needs.

FIRE AWAY!!!

 

[snoobler]

Your poor sun and 1 panel was probably just enough to keep the battery mostly charged. Note that full charge is not attained until absorption voltage (14.4-14.8 typical) is attained, and even then, it's not full until the current flowing AT the absorp voltage tapers to 2% of capacity.

So, your 100Ah battery is full when it charges to 14.4-14.8V and the current has dropped to 2A at the 14.4V-14.8V.

Your daily usage is limited to your daily solar harvest, or your battery level will continually drop. With only 100W of panel and presumably poor sun, that means you could only get about 300-400Wh of energy per day. That's only about 1/4 to 1/3 of your 100Ah battery's total capacity.

You basically doubled your battery and likely increased your usage because... you know... more battery!

Unfortunately, with only 100W and 190Ah of storage, you can't begin to get anywhere near fully charged. In fact, your 100W panel is supplying insufficient current - MAYBE 8A to a battery that should be charged with at least 19A, preferably closer to 25-30A. Charging at too low of a current below the bulk voltage encourages sulfatio and capacity loss.

Even doubling the panels isn't sufficient. You should likely double it again to 400W total.

The only thing that bugs me is that the battery should get fully charged while you're away, BUT another consideration is that cold batteries deliver less capacity and they need higher charge voltage to ensure they get full. If the Renogy has temperature compensation available, you should use it.

 

[HARG Hunter]

There was only a 1 week break between the time I added the extra batteries (which came fully charged) and the second weekend we were there to use the batteries again. It just happened to be a week of bad sun. I was hoping after almost a full week of no draw on the batteries that they would be up to that 14.4+ range, but they were only at 12.5 when I arrived. Probably just the circumstances.

At the same time I never thought about the low level of amps coming from the single panel either.
I will see what doubling the amps with the second panel does. Adding a 3rd panel wouldn't be a big deal again if it's necessary.

The Rover Elite does have a temp sensor for the battery bank, but not sure if that is there for reference or if it actually does make adjustments.

I will post an update after I install the second panel at the cabin Halloween weekend.

 

[Steve_S]

Quick search says Renogy 100W/12 Panel is $100. +/-
When 300W/24V class panels can be had for $120 and up.
The Lead Batteries are 50AH so 50% DOD allows for 25AH per... beyond 50% and the damage is being caused.
20A @ 12V is also not very much so do not expect that to charge the batteries too fast

 

[HARG Hunter]

Steve - I would love to know where I can get 300w panels for only $120.
I've been searching, and can't find anything close to that.

Also - Would there be a benefit to me switching my system to 24v by wiring everything up in series instead of parallel @12v?

 

[GMB]

Solar panels can be found at www.santansolar.com
I bought my new LG 350 watt panels for $150 each with no tax. I picked them up, so not sure what shipping would be to your location. A lot of members here have used Santan for their panels. Good company to deal with.

 

[Master Dalor]

Hello.
100w panel will produce about 5amps in the best conditions, during 1 hour, you get 5Ah.
During 1 summer day, maybe you had 5h sun, 5days x 5hours x 5 ampères = 125Ah
Now, with shadow/bad weather, maybe it produces less than 1amp, you should measure it with the ammeter.
With 20A mppt charge controller, you can't put more than 400W panels.
With 24v you'll get better efficiency.

 

[Steve_S]

Cheap Panels if you are in USA: https://store.santansolar.com/product-category/solar-panels/
Lots of the members here have bought from them and are happy with their purchases.

An SCC has a few values to look at. The Max Amps, Max Volts are key.
The SCC does not care about what panels are attached, it's only concerned about the volts, watts & amps.
You can use 12,24,48 or higher Volt Panels, as long as you do NOT exceed the max Volts, Watts/Amp ratings for the SCC.

Your SCC specs; (btw: I am absolutely NOT a fan of Renogy so this is as far as I'll look at this.)
Sadly it is quite limited as to what it can take.


Sample 300W Panel Info:

Specifications:

• Rated Power: 300w
• Open Circuit Voltage (VOC): 39.85V
• Max Power Voltage (VMP): 32.8V
• Short Circuit Current (ISC): 9.71A
• Max Power Current: 9.16A
• Maximum System Voltage: 1000V IEC

Sadly Will have never looked at Midnite Gear as that was not his focus (budget / value) and he completely missed these and so no one here knows much about them sadly...

Here is the Midnite Solar MNKIDBASIC KIT using the KID controllers. All in it's a bit more but look at it and ponder it.
This is Tier-1 Grade gear and the "Kit" is comprehensive.

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

KID specs & data page: http://www.midnitesolar.com/pages/kid/index.php

KID Solar Panel sizing tool, to figure out best combinations with your panel specs for maximum production:

MidNite Solar - KID Sizing Tool.

MidNite Solar is the industry leader and manufacture of quality Renewable Energy System electrical components and E-Panels.

www.midnitesolar.com

 

[Liam M]

Search Craigslist for local panels.
Many used panels and also new available from surplus orders etc.

 

[Master Dalor]

Cheap Panels if you are in USA: https://store.santansolar.com/product-category/solar-panels/
Lots of the members here have bought from them and are happy with their purchases.

An SCC has a few values to look at. The Max Amps, Max Volts are key.
The SCC does not care about what panels are attached, it's only concerned about the volts, watts & amps.
You can use 12,24,48 or higher Volt Panels, as long as you do NOT exceed the max Volts, Watts/Amp ratings for the SCC.

Your SCC specs; (btw: I am absolutely NOT a fan of Renogy so this is as far as I'll look at this.)
Sadly it is quite limited as to what it can take.
View attachment 25633

Sample 300W Panel Info:


Sadly Will have never looked at Midnite Gear as that was not his focus (budget / value) and he completely missed these and so no one here knows much about them sadly...

Here is the Midnite Solar MNKIDBASIC KIT using the KID controllers. All in it's a bit more but look at it and ponder it.
This is Tier-1 Grade gear and the "Kit" is comprehensive.

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

KID specs & data page: http://www.midnitesolar.com/pages/kid/index.php

KID Solar Panel sizing tool, to figure out best combinations with your panel specs for maximum production:

MidNite Solar - KID Sizing Tool.

MidNite Solar is the industry leader and manufacture of quality Renewable Energy System electrical components and E-Panels.

www.midnitesolar.com

Wow. I didn't thought the charge controller could only accept 260W at 12V.
Better go 24V.