Solar Battery Charge Issue

[KenS999]

Hello I have a 100W Renogy solar suitcase charging two AutoZone Duralast lead acid Marine deep cycle group 24 batteries. Batteries are 3 years old. Lately I have noticed the charging cycle time drastically increasing especially during the absorption phase of the charge cycle. Charging is now nearly twice as long as before. I have cleaned and inspected the terminals and connections. I have checked individual cell fluid levels as well. These batteries have been babied and never taken below 12.3V. My power usage requirements are minimal and have not increased.

I am wondering if these batteries are just getting long in the tooth as far as charging cycles? Would investing in a good specific gravity battery tester be the next step?

Thanks, Ken

[KenS999]

Ok thank you.

[Almot]

KenS999 wrote:
Not sure where you came up with a depletion of 50% unless you are using it just as an example.

My bad. You mentioned 12.3V, this would be 60% SOC.

With 100W solar you only harvest 25-28 AH by the end of a good sunny day. For 135Ah bank this is 80% SOC or 12.5 morning voltage.
For equalizing you need full battery, so 12.5% in the morning won't cut it - you won't have any sun left by the time the battery is full. You're not getting equalizing unless your cycle is really shallow, with morning voltage above 12.5.

[KenS999]

Not sure where you came up with a depletion of 50% unless you are using it just as an example. 25% daily depletion rate would be a more accurate assessment from the next morning's voltage readings from a voltage meter prior to setting out my panels for the day. What is puzzling to me is that I would always reach Full/Float at 13.6 volts by midday in southwest Arizona according to the charge controller display... until just recently. I guess my charge controller must have been lying to me for the last 3 years and I did not know it. I just don't know.

[Gdetrailer]

Boon Docker wrote:

Gdetrailer wrote:

KenS999 wrote:
The two lead acid Duralast batteries that I charge with the Renogy 100W solar suitcase are rated at 65 amp hours each.

100W "suitcase is not "rated 65Ahr", more like 6.5A hr and that would be in full sun at noon during the summer solstice with the panel pointed directly at the sun with no clouds in the sky. That max only lasts at best 4hr-5hrs a day.

If it was 65Ahr, that would be on the order of 57.1A!

To get the 65Ahr you would need 10 of those panels.

I think you misunderstood what KenS999 was saying. his batteries are 65 AH each.

Granted, yeah I missed that was the batteries at 65Ahr..

However,

Draw half of that from each battery would be 65Ahr for TWO batteries PLUS more for losses that needs to be put back in..

Call it say 70Ahr that needs to go back in..

100W panel can only give you 5.71 Amps PER HR for max of 4-5hrs..

So on a GOOD day with full sunlight in the middle of summer the OP has the potential of 28.55Ahr of max charging provided they kept moving the panel with the sun..

Might get a few amphrs the rest of the day so we will call it 35 Ahr total for a 24 hr period..

That is a 35Ahr DEFICIT each day..

In other words they will never, ever get the batteries fully charged with only one 100W panel..

They need about 10A of constant charge current per battery for 8-10hrs just to fully recharge both batteries..

Not gonna happen with 100W of panel, as it is each battery is only getting 50W at max sun and at 50W they could even connect the panel directly to both batteries without the charge controller.. There is not enough wattage to over charge the batteries if they are drawing them down halfway.. 2.5A per battery for 5 hrs is not much more than a trickle charger..

Think back to the days when the ONLY charger you may have had was a 2A trickle charger and attempted to charge a flat battery.. that could take days before your battery had enough charge to turn the engine over if you were lucky..

[KenS999]

Thanks to everyone for your input. I can see I have much more to learn about matched solar systems.

[Almot]

For equalizing to work the bank should be fully charged first. 100W solar won't fully charge 130AH bank discharged to 50-60%. So your automatic 28-day equalizing might not happen when you need it.

100W solar generates 25-30AH a day max. Unless your are cycling very lightly (doesn't sound like it is), 100W solar leaves your 135 AH bank undercharged and need equalizing maybe more than once in 28 days - but you might not be getting this automatic equalizing at all (see the previous paragraph).

Charge it fully at home whenever possible.

[Boon_Docker]

Gdetrailer wrote:

KenS999 wrote:
The two lead acid Duralast batteries that I charge with the Renogy 100W solar suitcase are rated at 65 amp hours each.

100W "suitcase is not "rated 65Ahr", more like 6.5A hr and that would be in full sun at noon during the summer solstice with the panel pointed directly at the sun with no clouds in the sky. That max only lasts at best 4hr-5hrs a day.

If it was 65Ahr, that would be on the order of 57.1A!

To get the 65Ahr you would need 10 of those panels.

I think you misunderstood what KenS999 was saying. his batteries are 65 AH each.

[time2roll]

Could separate and equalize the batteries one at a time.

[Gdetrailer]

KenS999 wrote:
I am charging strictly by solar. Charge controller is a Renogy Voyager. Absorption phase of charging cycle always runs at 14.7V. Equalization is automatically run by charge controller when necessary. Until recently I was able to achieve float within 3-4 hours. Now it can take 6 to 7 hours to achieve float. Thanks,Ken

Impossible with a 100W panel alone, you have killed your batteries capacity by drastically UNDER CHARGING!

There is no way a 100W panel can sustain enough amperage to effectively charge a battery to full in 3-4 hrs at 2.5A per battery.

KenS999 wrote:
The two lead acid Duralast batteries that I charge with the Renogy 100W solar suitcase are rated at 65 amp hours each.

According to the charge controller specs, Equalization will automatically occur every 28 days in the charge cycle @ 15.5V unless otherwise required.

Just ordered a temperature correcting hydrometer online. Thanks, Ken

100W "suitcase is not "rated 65Ahr", more like 6.5A hr and that would be in full sun at noon during the summer solstice with the panel pointed directly at the sun with no clouds in the sky. That max only lasts at best 4hr-5hrs a day.

Specs on the panel are..

"If you're looking for a convenient and portable power solution, the Renogy 100W Monocrystalline Foldable Solar Suitcase is an ideal choice.
The Renogy 100 Watt 12 Volt Monocrystalline Portable Solar Suitcase is an entire solar power system incorporated into one small package. Weighing in at about 27.60 lbs, this lightweight suitcase includes two 50 Watt Monocrystalline Solar Panels, one 30 Amp Adventurer Charge Controller with an LCD Screen for power regulation, one 10ft tray cable with alligator clips for easy connection to the battery, one temperature sensor, one battery voltage sensor, and a protective casing for safe portability. The Renogy 100 Watt Solar Suitcase will make charging on the go as easy as 1-2-3!
Please Note: The Charge Controller is Not Waterproof.
Renogy 100W Foldable Solar Suitcase
Maximum Power: 100W
Maximum Operating Voltage (Vmp): 18.0V
Maximum Operating Current (Imp): 5.71A
Open-Circuit Voltage (Voc): 21.6V
Short-Circuit Current (Isc): 6.17A
Operating Temperature: -40°F to +185°F
Folded Dimension: 19.9 x 27.2 x 2.4 inches
Weight:27.65 lbs
Renogy 30A ADV Charge Controller
Nominal Voltage: 12 VDC
Rated Charge Current: 30A
Max. PV Input Voltage: 25 VDC
Float Voltage: 13.8 V
Under Voltage 12 V
Operating Temperature: -13°F to +131°F
Terminals: Up to #4 AWG"

Note the bolded text, yeah that is 5.7A..

If it was 65Ahr, that would be on the order of 57.1A!

To get the 65Ahr you would need 10 of those panels.

Just because your controller may shift voltages, doesn't mean the batteries are getting more than a trickle charge.

You NEED more panels if you want to stop killing your batteries or connect to shore power.

[KenS999]

The two lead acid Duralast batteries that I charge with the Renogy 100W solar suitcase are rated at 65 amp hours each.

According to the charge controller specs, Equalization will automatically occur every 28 days in the charge cycle @ 15.5V unless otherwise required.

Just ordered a temperature correcting hydrometer online. Thanks, Ken

[pianotuna]

KenS999 wrote:
I am charging strictly by solar. Charge controller is a Renogy Voyager. Absorption phase of charging cycle always runs at 14.7V. Equalization is automatically run by charge controller when necessary. Until recently I was able to achieve float within 3-4 hours. Now it can take 6 to 7 hours to achieve float. Thanks,Ken

It is not physically possible to equalize a 200 amp-hour battery bank with a 100 watt panel. You would need at least 120 watts, with absolutely perfect solar conditions, and perfect tracking of the sun. I suggest bumping up to 200 watts of panels.

I'm not familiar with the Voyager controller. On mine, I have to move a dip switch to allow for equalization (or not), which then allows equalization every 30 days. I added an external switch to my controller to allow me to easily toggle an equalization charge. Sometimes I do that to get a few more amp-hours of harvest.

Does the Voyager do temperature compensated charging?

So I repeat, fully charge the bank. Then do a proper equalization charge most probably using 14.8 volts. You may need to "push" that to 15.3 volts. Finally, check the battery bank with a hygrometer.

You are extremely frugal on your power use. So kudos for that!

[time2roll]

Are you certain you are getting the same amps out of the panels? May improve some by mid June.
Otherwise just use it until the system no longer provides what you need.

[MrWizard]

You don't mention type of RV, or if you have a generator
In my previous RV I had a residential 120v fridge, powered by inverter 24/7, solar and generator
I made it a point to run the generator every morning to do the heavy recharge from nightly use, then the solar could do the top up, and supply the usual daytime needs
Batteries need good voltage and amps, when being cycled daily, otherwise they sulfate, this will continue to degrade battery capacity and charge acceptance until they are useless !

If your needs are minimal, a 1 hour charge from the rv converter in morning, powered by a generator will go a long ways in keeping your batteries in better shape giving you more life from them, or you can add 200 more watts of solar, and hope for good sunny weather every camping day

[KenS999]

I am charging strictly by solar. Charge controller is a Renogy Voyager. Absorption phase of charging cycle always runs at 14.7V. Equalization is automatically run by charge controller when necessary. Until recently I was able to achieve float within 3-4 hours. Now it can take 6 to 7 hours to achieve float. Thanks,Ken

[time2roll]

Give us some actual numbers. What is the absorption voltage measured on the battery? And how are you measuring absorption time that has increased? What is the time? What controller (make and model) do you have?

I rate the batteries fine as long as they meet your needs. When you are getting to 11.5 volts or lower while in use then you can call them shot but 12.3+ is just fine.