? for the solar experts

[rastaman]

System...... 2 6 vlt battery, 2 100 watt panels.
Usage...mainly running a 12 volt refridge and computer

Panels will NOT be permanently mounted on roof. They will hang form the side of TC and be taken on and off as needed or placed on the ground when parked in the shade.

Question: Can I connect the panels directly to the batteries to get max voltage in shortest possible time....seeing that I can determine when and how often the panels are charging

thanks

 

[jimindenver]

I have seen people connect the panels directly to the battery, the voltage of the battery is the regulator. This won't charge the battery any faster but it will allow you to reach higher voltages for equalizing if your controller doesn't allow for it. The down side is the panel will take your battery above 15v, possibly damaging the battery and your systems.

A inexpensive charge controller wont be any slower, just more hands off. Spend $100 on a MPPT controller and run your panels in series and you will get some more power at peak. The difference is you won't be losing watts early on when the battery voltage is low.

I do know of some one with their panels on the side as you say, they can tilt up or be removed and act as a portable.

 

[blars]

Directly connecting panels to the battery is not recomended, you won't get any more power than with a pwm controller and could easily damage your battery unless you are constantly monitoring it.

 

[jimindenver]

Add in that the controller to handle those two panels is incredible inexpensive. PWM controllers on ebay are $30 or less and more than functional. Want more power, a $102 shipped MPPT controller will give you a bit more but honestly I'd buy another panel first.

 

[akrvbob]

Different batteries want to be charged at different speeds. If you have a battery that wants to be charged fast, then you could go direct for short periods of time. But once over the bulk phase of charging, all batteries want a slower charge rate. If you don't give it to them, they will be damaged and fail soon.

Getting all that just right would be incredibly time-consuming and very unlikely to happen. Get a charge controller!!

On the other hand, all batteries need to be equalized which is essentially giving them a high voltage and boiling them for about 8 hours. It would seem like a valid way to that as long as the voltage of your panels happend to match the voltage needs of your batteries. But they only need it once or twice a year so you will still need a controller.

Bob

 

[jimindenver]

Many controllers automatically equalize. Bob is right though, that slow float charge is required to get your batteries back to 100%. You will never get there without a controller.

 

[highdesertranger]

get a controller. even my dinky 15watt panel overcharged my batteries. so I put a cheap controller on it and I am on my 4th year on my el cheapo Costco batteries. highdesertranger

 

[ccbreder]

"boiling" a battery is only applicable to wet cell batteries. But the others need to be balanced in their own way.

 

[rastaman]

I am sorry I should have noted that I do already have a controller, PWM supplied with the kit from Renology. My thought was that since the panels were not be permanently mounted and may have limited used when using them I was going to try and squeeze max out of them....We based on the response I will use a controller.
Now I just have to decide if I should use what I have already purchased connected in parallel or toss it and purchase a MPPT and connect the panels in series

 

[jimindenver]

The least expensive MPPT controller is the one I have been using at $102 shipped unless you win it for less in a auction on ebay. Nice little controller with a display and adjustable settings for absorb and float.

http://www.eco-worthy.com/catalog/mppt-solar-charge-controller-free-shipping-p-182.html

Honestly for the money, I think you would be better off buying a third panel. The MPPT controller will get you some more at peak and will convert wasted volts to amps, especially early on when the battery voltage is low. It wont however provide as much extra as a third panel would.

 

[TucsonAZ]

The MPPT will net you more watts into the bank but not more than a third panel would, unless you're planning to add a few more panels I would get another panel as well. Also, the only reason to go in series is to up the voltage to avoid power loss for longer wiring runs, if that isn't needed there isn't much point honestly for what you're doing.

You will struggle to keep those batteries happy for long if you only plan to hook the solar up from time to time though so stay on top of their condition.

 

[rastaman]

Well based on the advise I have gotten here. I have decided to try my present system with 2 panels and PWM controller and see how it works, but I will be saving for an extra panel.


Thanks for all the helpful suggestions.

 

[GrantRobertson]

On the other hand, all batteries need to be equalized which is essentially giving them a high voltage and boiling them for about 8 hours.

Bob, could you explain more about this "equalizing" thing or provide a link? I've heard of balancing packs of Li-Ion batteries, but never heard of "equalizing" a single lead-acid battery.

As an ancillary question: does anyone know of a book or web site that has a truly thorough explanation of all this battery use and charging wisdom? I would kind of like to become a true expert in it all. Seems like people who really know how all this works are going to bee in high demand.

 

[Seraphim]

I am sorry I should have noted that I do already have a controller, PWM supplied with the kit from Renology. My thought was that since the panels were not be permanently mounted and may have limited used when using them I was going to try and squeeze max out of them....We based on the response I will use a controller.
Now I just have to decide if I should use what I have already purchased connected in parallel or toss it and purchase a MPPT and connect the panels in series

Renonogy will take the old controller back and upgrade to the MMPT.

 

[SternWake]

As an ancillary question: does anyone know of a book or web site that has a truly thorough explanation of all this battery use and charging wisdom? I would kind of like to become a true expert in it all. Seems like people who really know how all this works are going to bee in high demand.

http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

http://www.lifelinebatteries.com/manual.pdf

The lifeline manual has some things specific to their AGm batteries, but they say lots and say it well.

 

[akrvbob]

The details of how to equalize vary with the specific battery, but the idea is always that you first fully charge the battery and then bring it up to a very high voltage (from 14.8-to over 15) and hold it there for 8-12 hours.

Lifeline recommends 14.8 for 8 hours for their AGMs. It can take a battery you think is trash and bring it back to life.
Bob