Solar Batteries not charging all the way

karenyamil

Hello guys, I am new to the solar system, I currently live in a van and I have two solar panels and two AGM batteries from Renogy. I use their new 1000W 12 volt pure sine wave inverter with power saving mode and a 20 AMP MPPT charge controller.

When I first got them, obviously working fine, I notice I was getting more voltage than W so I bought something called “Branch Connector Y in pair MMF + FFM” for parallel connection for my 2 solar panels. I look more information into it and they said I need this to get my solar in parallel and get more energy to charge my batteries. Is that right?

I used the batteries from time to time (at that moment I wasn’t living in the van yet) and they charged normally, but after a couple of weeks I notice that my batteries were not staying charged, it was so bad that it drain almost completely. I decided to turn off my inverter and not use the batteries. I did that, it took around 2 months to get to 50% charged. I also want to say that I live in Mass and this was happening between October and November so it was most of the time cloudy during the time I turn off my inverter.

I notice that turning off my inverter helps the battery charge. Now for the past 3 weeks I been getting not so bad weather, I have more sunny days then I though and somedays it says is 100% charged but as soon as I connect my ipad, my iphone or switch it goes from 100 to 90 to 70 to 66 or 61 and it stays like that for a while. I have charged my ipad or switch in 61 for an hour or more and it stays the same but my batteries are never actually charged 70 to 100%. I even had time where my batteries were 51% or 56%.

So I explain what I could here, honestly I know nothing about solar, batteries, wiring. I did my best looking up videos, watching them more than 10 times, going back to my system and checking if I did everything right but still I just can’t figure out if I am doing something wrong or bought something that doesn’t go together.. PLEASE help me understand this, I don’t know the terms or names of a lot of this things so explain it to me as if I was a child because seems like that’s the only way for me to get it.

Oh and I forgot to say that I end up just using one battery to see if the solar/sun was not enough to charge two batteries. I did this a week ago and still is not charging all the way, it stays in the 60’s.

I apologize for my bad English, I am trying to get better at it.

mike95490

That is a very large inverter and it consumes power just by being turned on.   Leaving it on 24/7 eventually drained your batteries and with cloudy weather, they never recharged and have eventually become ruined.
 When batteries charge up from dead to full in a short period of time, confirms they are sulfated and if it was a one day event, they might be recoverable, but after months, they are just dead.
  Sorry, but you have learned an expensive lesson - that you cant take more out of a battery than you charge into it.

BB.

Hi Karenyamil, welcome to the forum.

The direct answer is what Mike said above--You have a small solar power (charging) system and a relatively large battery bank+load.

Lead Acid (and AGM) batteries need to be recharged pretty quickly after they have been discharged. If you let them sit at less than ~75% state of charge for days/weeks/etc... The batteries will tend to "sulfate" and lose most of their capacity--Permanently.

We have several ways we can proceed here... One is to measure/understand your daily loads--Which defines the size of the battery bank. And then with the daily loads, size of battery bank, and where you are located/etc., we can design a system that will meet those loads.

In areas with poor sun (like the North East), you don't really harvest much energy in the winter. For example, a 200 Watt array mounted flat to a van roof, in Boston Mass:
http://www.solarelectricityhandbook.com/solar-irradiance.html

Boston
Average Solar Insolation figures

Measured in kWh/m2/day onto a horizontal surface:

Jan	Feb	Mar	Apr	May	Jun
1.80	2.62	3.61	4.46	5.13	5.50
Jul	Aug	Sep	Oct	Nov	Dec
5.60	4.99	4.04	2.93	1.89	1.54

For example, in January, 200 Watts of panels (flat) will harvest an average daily energy of:

200 Watt array * 1.80 hours of sun (January) * 0.52 off grid AC system eff = 187 WH per day
200 Watt array * 1.80 hours of sun (January) * 0.61 off grid DC system eff * 1/12 volt DC battery = 18 AH @ 12 volts per day (if you were running DC loads)

Your 12 volt 1,000 Watt sine wave inverter draws about 1 amp @ 12 volts just being turned on:

• 1 amps * 12 volts = 12 Watt "tare" losses
• 187 Watt*Hour harvest / 12 Watts average inverter tare loss = 15.6 Hours per day of power just to run the inverter

So--For your setup (making lots of guess), just running your inverter with no loads for 16 hours per day, uses more energy than you harvest (in January) on an average day...

When running solar in a van--You need to 1) have very efficient/low power loads; 2) a battery bank to support those daily loads; 3) a solar array sized to recharge your bank daily; 4) if you don't have enough solar--Then a backup means of charging (shore power, Van alternator, backup AC genst + AC charger, etc...

We are very happy to walk you through the design process... So, if you can help us with understanding your loads (amps * hours per day, Watts * Hours per day, rough location, any backup charging sources, etc.).

Doing it step by step will help you to better understand your system and its capabilities, and hopefully save you money in the future (your batteries should last around 3-5+ years in a van).

The reality is that you need to have as few loads as possible and an "over sized" solar charging system (to allow for a day or two of bad weather, and the occasional heavier loads). And for a van--You do not have much room for solar panels or battery bank... Off grid solar power is a limited commodity.

-Bill

karenyamil

mike95490 said:

That is a very large inverter and it consumes power just by being turned on.   Leaving it on 24/7 eventually drained your batteries and with cloudy weather, they never recharged and have eventually become ruined.
 When batteries charge up from dead to full in a short period of time, confirms they are sulfated and if it was a one day event, they might be recoverable, but after months, they are just dead.
  Sorry, but you have learned an expensive lesson - that you cant take more out of a battery than you charge into it.

Wow, I didn’t know that 😐.
i mean after a month I turn if off because of that problem although during the process of the batteries dying I never thought the inverter was the problem. I should have done more research on which inverter to buy and I guess one battery is enough for the solar panels I got and the amount of sun I receive. Thank you so much, I appreciate your help. 

mike95490

Sadly, solar power is not all the effortless joy the hucksters make it to be.  And then when you discover it, you are out some serious money..

Photowhit

mike95490 said:

Sadly, solar power is not all the effortless joy the hucksters make it to be.  And then when you discover it, you are out some serious money..

So long as there is reasonable expectations, to me, it is exactly the effortless joy I expect!

No sun, no joy!

bwh1969

I just saw this and it was last replied to 3 years ago but it might help anyone who sees this thread.  I have an AGM based solar system for my workshop.  I eventually went to LiFePO4 for the house and RV for this very reason.  I did mostly recover two 75 AH AGM batteries from a similar mistake over a year ago when I was just starting.  I used a moderately pricey charger with a repair function and it ran for about 24 hours.  The next day, they appeared to be fully charged and the battery meter showed a gradual and seemingly normal drop when used again so if the original poster sees this, you could give that a try to recover the batteries.  It uses a high frequency pulse that pushes the insoluble sulfate back into the solution in the glass mats.  Depends on how badly the battery is “choked up” but I was able to recover mine.