When to re-engage the solar system

[larry2c]

Due COVID & plain ole life we aren't getting out much right now. Last year I installed a pair of 6V golf cart batteries and we have a 200W solar system on our TT. I monitor the battery discharge and when it gets down to about 90% I turn the battery cuttoff switch to On and then set the solar panel switch to On. After a few days of charging I switch everything back off. Rinse & repeat as necessary...

I do the On/Off routine with the thought of less cycles on the batteries and reducing the chance of inadvertently running the water level down. My questions are this - is my On/Off routine better than just letting the solar keep them topped off every day? If On/Off is helpful, how far down should I let them discharge before recharging?

FWIW I did search for this question but didn't really find anything that matched what I'm trying to ask. Thanks to all!

[Lundy]

I have no science to back up what I do, so take it for what its worth. I never turn my solar off, I do have a reminder on my cell phone to check Batt water every month. You are causing cycles by turning off the solar and the batts discharging to 90%. I believe from my readings it's better to let the solar keep them at 100% rather trying to bring them back up to that level. The loss of water is a real concern and needs to be monitored. I ruined a set of batteries after I installed my solar. Guess How.LOL

[boondocking]

I have the same set up as you do, 200watts of solar and a pair of GC2 batteries. I never turn the solar off through the summer when I am not using the trailer.
My batteries are 8 yrs old and still going strong.
If I were you I would leave the solar running all year, whether using the trailer or not.

[richp]

I've got 600 watts flat mounted on the roof, and over many years have never turned the system off over the winter.

The master battery disconnect is off; all I have to do is top off the water once a month and trust the controller to do the rest for any internal battery drop-off.

Rich Phillips

[Flybob]

If you have a good solar controller there is no reason to ever use te battery disconnect switch. Simply leave it on and check electrolyte levels every 6 months.

[richp]

I know it's probably not necessary to kill the master switch. It's just me working off of old pre-solar/ abundance-of-caution instincts, since snow cover can cover my panels for an extended period of time here in the upper Midwest.

Rich

[HangDiver]

Originally Posted by Flybob

If you have a good solar controller there is no reason to ever use te battery disconnect switch. Simply leave it on and check electrolyte levels every 6 months.

This^^^^^^ By turning the battery disconnect switch on and off you're cycling your batteries more than you think. Let the panels keep the batteries topped off.

[larry2c]

First, thanks to all for the responses, much appreciated!

I guess my thoughts were sort of referring back to when I worked in a big aerospace plant and we had "golf carts" up the wazoo. The general consensus there was that you didn't plug them in after each trip - you waited until the meter showed about a half charge and then you plugged it in. I have no idea what that meter was measuring (most were so clouded over from being in the sun you couldn't really read them) but I'm guessing it was looking at some voltage level. Anyway, that's why I got to thinking about letting the batteries discharge over time and them bring them back up. Maybe all that GC stuff was just a wives tail...

[Hawk on the Wing]

Yea, I agree about leaving the solar system on but there are a few things that make that a better decision.

First, make sure you have a good smart solar controller with four stage charging.

And get one that has different modes for different kinds of batteries and make sure it is set correctly.

And finally, I think it is a very good idea to have one that has a remote temperature sensor that goes in the box with your batteries. The optimal rate of charge is very different if the battery is cold. This really babies your battery.

[jimmoore13]

It is NOT recommended that you remove the battery load from a solar system without covering the panels--or disconnecting their output from the solar charge controller's input.

A 200 watt panel array can be putting out 18 volts (parallel) to 36 volts (series) at 15 amps (parallel) to 7.5 amps (series) in full sun.

The solar charge controller struggles to handle the solar panels' output when it doesn't have a place to send the power and the feedback loop provided by the batteries to signal the charge controller with what to do with that energy. When the battery is full...and connected...the charge controller can throttle back the energy output, but without a battery to tell it what it needs, the charge controller may become very unhappy.

Do not use the rig's battery disconnect or remove the battery load without covering the panels or disconnecting them from the charge controller's input. OTOH, if you want to disconnect the rig from the battery bank for some reason, be sure your charge controller's output is wired directly to the battery bank.

Since you should be hooked up to the batteries full time, check your electrolyte every month or so to ensure you don't "run dry".

Obviously, covering the panels, if they are mounted on the roof, can be a royal pain. Doing so for long periods even more so. If you have another reason for disconnecting the batteries (say to prevent theft in storage), install a high amperage switch in the cable feeding power from the panels to the input side of the charge controller. Then you can disconnect the panels from the charge controller input and do what you wish with the batteries.

https://shop.gwl.eu/blog/Solar-regul...operation.html

[richp]

Jim makes an excellent point, noting the distinction between killing the power between the batteries and loads in the rig itself, and disconnecting the batteries from the controller.

I have a reminder message taped up in the vicinity of my controller telling me to pull the fuse coming from the panels if I have to disconnect the battery. But I've used the big red battery disconnect switch more times than I can count without adverse impact on the solar system.

FWIW.

Rich

[larry2c]

To Jim & Rich - understood and I have 2 cutoff switches, one for the controller and one for the battery. When I shut things down I turn off the switch connecting the panels to the controller and then the battery cutoff switch gets turned off. When I re-energize the system I go the opposite way - turn on the battery cutoff and then the solar panel to controller. I even labeled the switches to hopefully remind me to follow that sequence

[Hclarkx]

My 2 cents is, it depends. If your solar controller goes into bulk mode every morning and runs the batteries up to 14.4V during the day, then goes to absorb, then finally to float, you are taking some life out of the batteries. If instead, the solar controller comes up in float mode, and brings the batteries only up to float voltage, say, from 12.7V up to 13.5V, and hangs there throughout the day, there will be only modest wear and tear.

Just what the solar controller will do depends on one setting; that is the voltage below which the battery voltage must drop to trigger a bulk/absorb/float sequence at daybreak. If this setting is below the voltage the battery drops to each night, the solar controller will likely come up in float mode. This is ideal.

If you find the solar controller is cycling the batteries to 14.4V needlessly, and you can adjust this setting, set it lower, maybe 12.6V or 12.7V. With this setting the solar controller may come up in float mode, or may do nothing until the battery has self-discharged slightly and then cycle it through the three stages. Either is better than cycling to 14.4V every day. This setting is not accessible in the solar controllers I've had. However, I've had solar controllers with "user settings" in which I could duplicate all of the lead-acid settings and change just this one setting to avoid daily cycling to 14.4V.

[larry2c]

Thanks Hclarkx - that's very helpful info! I'll check the voltages and if necessary give them an adjustment like you suggested. Not hurting the batteries is exactly what I'm aiming for!

[Hawk on the Wing]

Hclarkx,
I see where you are going here and I would agree wholeheartedly on one point: there are big differences in solar controllers and you want a good one.

But if your battery is going from float mode voltage (13.4) during the day and then dropping to 12.7 at night one of two things are happening: The battery is about shot and has an excessive self-discharge rate or there is a load on the battery. A healthy battery with no load should never self-discharge that much in one day in any temperature. So if either one of those things is the case, you better be letting your solar controller keep it charged or you are going to have a frozen battery if it's winter. Sorry to disagree but I would stick with the recommended settings.

[TitanMike]

Originally Posted by Hawk on the Wing

Hclarkx,
I see where you are going here and I would agree wholeheartedly on one point: there are big differences in solar controllers and you want a good one.

But if your battery is going from float mode voltage (13.4) during the day and then dropping to 12.7 at night one of two things are happening: The battery is about shot and has an excessive self-discharge rate or there is a load on the battery. A healthy battery with no load should never self-discharge that much in one day in any temperature. So if either one of those things is the case, you better be letting your solar controller keep it charged or you are going to have a frozen battery if it's winter. Sorry to disagree but I would stick with the recommended settings.

How do you figure battery is shot?

12.7 volts is 100% SOC for a lead acid battery after it's rested long enough for the surface charge to dissipate.

[Hawk on the Wing]

Originally Posted by TitanMike

How do you figure battery is shot?

12.7 volts is 100% SOC for a lead acid battery after it's rested long enough for the surface charge to dissipate.

Yea, 12.65v is considered 100% but that depends on the battery and the situation. I have two different lead acid batteries right now that have been sitting in Colorado mountain weather for about a month with no load/no charging and they are both still sitting at about 12.85v. I just had a friend that was worried about the condition of his battery pull it off of his smart charger for 24 hrs and then check it and it was still at the 13.4v float voltage.

The real key is the rate of self-discharge. A sulfated battery will self-discharge much faster than a healthy battery. I would be concerned about a battery that has been maintained at float voltage (13.4) all day and then drops to 12.7v in just a few hours with no load. I think you will find that once you put a load on these batteries they will all drop quickly down to that 100% level you are talking about where they then start to really put out the amperage they are designed for.

But regardless, I think the engineers that set up chargers know what they are doing and a good 4 stage smart charger is designed to take good care of your battery. I won't mess with it, that's my basic point. This worry about cycles is a little over done. It's the deep cycles that have more effect on battery life, not the small ones.

[HiTech]

This. Lead acid batteries care about time sitting discharged more than the number of shallow discharges. The best thing you can do for FLA is keep it floating as much of the time as possible, with the plates never exposed to air.

Originally Posted by Hawk on the Wing

Yea, 12.65v is considered 100% but that depends on the battery and the situation. I have two different lead acid batteries right now that have been sitting in Colorado mountain weather for about a month with no load/no charging and they are both still sitting at about 12.85v. I just had a friend that was worried about the condition of his battery pull it off of his smart charger for 24 hrs and then check it and it was still at the 13.4v float voltage.

The real key is the rate of self-discharge. A sulfated battery will self-discharge much faster than a healthy battery. I would be concerned about a battery that has been maintained at float voltage (13.4) all day and then drops to 12.7v in just a few hours with no load. I think you will find that once you put a load on these batteries they will all drop quickly down to that 100% level you are talking about where they then start to really put out the amperage they are designed for.

But regardless, I think the engineers that set up chargers know what they are doing and a good 4 stage smart charger is designed to take good care of your battery. I won't mess with it, that's my basic point. This worry about cycles is a little over done. It's the deep cycles that have more effect on battery life, not the small ones.

[Kennedy19]

Originally Posted by boondocking

I have the same set up as you do, 200watts of solar and a pair of GC2 batteries. I never turn the solar off through the summer when I am not using the trailer.
My batteries are 8 yrs old and still going strong.
If I were you I would leave the solar running all year, whether using the trailer or not.

Is it ok to take the battery out for the winter if the solar is supposed to be charging it?? Or should I just leave it in. Just bought my 2021 wolf pup and took out the batter my while storing camper... not sure I should have done that.

[boondocking]

If your solar can continue to function properly through the winter then just leave the battery in place. Let the solar keep it charged. I fully charge my batteries in the fall then disconnect and turn off the solar until spring. My solar does not work properly in the winter because of the heavy snowfall on the panels.