MPPT Charge Controllers and power regulation

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Gonguana
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MPPT Charge Controllers and power regulation

Unread post by Gonguana » December 20th, 2013, 10:31 am

Hi Guys,
I have been wondering around the board and reviewed many articles regarding MPPT Charge Controllers.

I have one specific question that i hope someone can answer.

I have a 120watt 12V or rather 18V fold out panel.
2X 100ahr AGM batteries connected in parallel, I have these connected through 2 switches. The first switch is a battery isolation switch. So power in, and i can switch from either battery, off or both batteries. Off the main in. I have another switch that connects all the peripherals.

So in the design if i was to switch the first switch to off and leave the second switch on. Power from the panel or car would flow through the system. If both switches are off then all power is off. "I think you have the picture now"

Currently my solar panel has a pwm standard controller mounted at the panel. I want to bypass this and connect an MPPT Charge controller in the camper. I am hoping this will assist in 2 ways.

Firstly, i believe that when i do need to charge batteries the environment and charge control will be better monitored and controlled.

Secondly, And this is also my question. when the batteries are fully charged and lets say the fridge is running or someone wants water out of the tap. Will the MPPT Charge controller supply controlled power to the fridge and water pump if the batteries were turned off?

My hope is to be able to drag most of my power during the day from the panel and at night flick over to battery. What do you guys think?

mydmax
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Re: MPPT Charge Controllers and power regulation

Unread post by mydmax » December 20th, 2013, 12:16 pm

Gonguana
From what I read of your description, sometimes the solar reg will be disconnected from a battery or batteries, is that what you mean.
The solar will not like being disconnected, and especially if it is already charging something and suddenly you disconnect or off disconnected then suddenly reconnect. I would think the reg will be damaged.

The panel output through a reg may not be enough to run a water pump anyway.
A solar and reg and fridge all running at the same time is normal usage.

Probably best if you can provide a sketch of the diagram so the full idea can be seen.
Most people have the engine charging the batteries and when it is stopped the solar will continue and both are connected at the same time.

A DC/DC units chooses the best source and it has both supplies connected all the time but yours doesn't choose.

Gonguana
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Re: MPPT Charge Controllers and power regulation

Unread post by Gonguana » December 20th, 2013, 12:33 pm

Hi Mydmax,
Thanks for the reply.
So the entry or main line in to the camper is through the anderson plug at the front of the camper. I would think this is the norm for any camper. I have the choice of connecting it to the car, genny or solar. Typically when we are camping its connected to the panel. Typically when we leave home and go camping its early morning so the batteries are charged. I would run with the battery switch in the off position and when we arrive. Unpack ect and then plug the solar panel in. Typically the batteries would be turned on and all is as good as it gets. i suppose i wanted to know if i could leave the batteries turned off and run my devices directly from the solar panel. Then flick them on at night. During my research i have been noticing the way the MPPT controllers work as they will allow the panels to work at their full capacity.

This causes a problem because the panel puts out 18volt. So i need to regulate this down to 12volt to be useable i would imagine. So the thought was to install the mppt controller and load of that. hoping it would rectify the loaded current to the demand without using the batteries.

P.S. i think i was reading another post where perhaps you said you have jumpered a relay off the load port of an mppt controller. Is that correct?

mydmax
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Re: MPPT Charge Controllers and power regulation

Unread post by mydmax » December 20th, 2013, 1:44 pm

Maybe I'm not quite sure what you mean.
Can you have the devices and the batteries all connected together and be fed from an Anderson plug from the vehicle which will keep the batteries charged as you drive?

If the solar is only unfolded and in use when stopped/camped then the batteries, solar and devices can be then all together.

If no Solenoid/Relay cuts the power to the Anderson on the rear of the vehicle it just needs to be unplugged to keep the start battery untouched while the rest of the trailer system with the solar and MPPT keeps it all charged back there.

Gonguana
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Re: MPPT Charge Controllers and power regulation

Unread post by Gonguana » December 20th, 2013, 2:06 pm

mydmax wrote:Maybe I'm not quite sure what you mean.
Can you have the devices and the batteries all connected together and be fed from an Anderson plug from the vehicle which will keep the batteries charged as you drive?
Absolutely mate.

As per my original post. I just turn switch 1 and 2 on.

Bala
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Re: MPPT Charge Controllers and power regulation

Unread post by Bala » December 20th, 2013, 5:26 pm

No you cant run items directly off the charge controller, and it will serve no purpose.

When ever you can have the panel connected and charging both batteries to keep them as fully charged as possible.

Shaker4x4
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Re: MPPT Charge Controllers and power regulation

Unread post by Shaker4x4 » December 21st, 2013, 12:26 am

Considering the solar panel you stipulate would suit a single 60 - 100ah battery and not run a fridge for extended period. Consider if you want at least half decent life from the batteries, 70% of their ah rating is not to be considered usable power by 'rough definition,' ie: say, of 200ah, 60ah is usable. Two days of cloud might require more power storage capacity to see it through rather than mistreating a battery. Battery drain goes by voltage ramp-down until you hit dangerous levels below 11.2v. You'll soon find out what you need.

Secondly, if the batteries are isolated from the MPPT controller,amperage directly from the solar panel via the MPPT controller alone would be insufficient to drive a pressure pump higher than 2amps perhaps, let alone the fridge as well. I'd suggest adding another panel. As mentioned though, why disconnect the battery bank from the charging system anyway? If the batteries are full and excess power is being generated above demand, it's pointless disconnecting the bank. Unfortunately, it appears you will not be generating excess above demand and will constantly run into the negative feedback until you need alternative charge so you can't afford to disconnect anyway and as Bala above me here says, keep them charged as much as possible. peak charged batteries last, drained batteries don't. More drain, more pain.

In regards to the solar panel you mention, consider it's construction, it's rated performance with age degradation, solar exposure, weather conditions and especially heat, because as panels heat up their output degrades. The solar output via the MPPT controller is somewhat inefficient as well, there is always loss in conversion and resistance in the entire system, especially the battery. Overkill is not really overkill in the long term at all when you're setting up. The setup you have will drive a small fridge for a while with the solar power as a buffer extending the time you'll get out of the batteries. At some point you'll need to seek alternative or additional charge to keep up with demand whilst keeping what I said about usable power in mind.

The old turn the fridge off at night ideal is futile and in fact uses more power recouping temperature in the morning as the ambient temperature begins to rise again in case you thought that was also a good idea. Insulating bags, reducing ambient temps with shade, ventilation and keeping the fridge running is the best anyone can do aside from not running the fridge like a freezer. Anything to help your little solar system.

A Whale brand 12v pump with enough pressure for a shower will use 3.6 - 3.8 amps and that's not a higher pressure caravan type pressure pump either. They call them inline pressure boosters. Your panel would be running an uphill futile marathon especially when a cloud passes over.

Shakes.

Gonguana
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Re: MPPT Charge Controllers and power regulation

Unread post by Gonguana » December 28th, 2013, 7:24 am

Hi guys, Thanks for the advise, I am going to start a new thread and detail my setup with my MPPT controller and the layout.
I'll link to this one.

whizzo
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Re: MPPT Charge Controllers and power regulation

Unread post by whizzo » December 28th, 2013, 11:36 pm

Gong mate you need to undertand one thing.
solar regulators are designed to operate with a battery connected.....this is a very important concept....the whole design concept revolves arround this asumption.

If you disconnect the battery it is wise to disconnect the solar panels from the regulator.....some regulators will cope with the unloaded voltage from a pannel...some wont.

The other concept that is important to understand is that the battery is part of the regulation system....and that is in most battery systems......a great many chargers put out other than a smooth DC stream.....the battery smooths out the pulses or whatever is comming from the charging source and makes the power usable.

The current from a car alternator for example would be very nasty if it was not for the battery.

In a situation where you have a solar pannel that is small in relation to the battery capacity...like you have.....the main function of the solar regulator is to prevent over charging once the batteries are fully charged.......if you are running a fridge and only the single pannel...that wont be very often.

A MPPT regulator may help you......but ya don't get anything for nuthin......if ya running out of schnaps...you need more pannels.

cheers

smokey05
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Re: MPPT Charge Controllers and power regulation

Unread post by smokey05 » April 25th, 2015, 10:15 am

I have 240 watt portable solar panels. Volts at back of panel to the battery fluctuates between 14 to 16.5 on a multimeter. Will this damage my battery? Battery is agm. Any advice would be appreciated.

vk3aif
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Re: MPPT Charge Controllers and power regulation

Unread post by vk3aif » April 25th, 2015, 4:52 pm

What is the voltage across the battery terminals as that is where it is important to be right? If you are reading 16.5V on the battery side of the regulator it suggests to me you may have too much resistance in the wiring between the reg and the battery. This can occur if the wire diameter is too small, the wiring is too long, a combination of the first two or an unsatisfactory connections somewhere between the two.

Tell us the voltage readings with the volt meter connected directly to the battery terminal posts and not via any other wiring.

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