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cuffy 12-06-2018 10:58

Solar controller

Does anyone know how these work?

How does it know when absorption has finished?
Not much technical info on web site.

john61ct 15-06-2018 11:52

Re: Solar controller
They only need to know that the bank is near full, accepting only a small fraction of the SC's potential output.

A shunt on the bank is how that should be measured.

I'd want to carefully test it did not prevent that even very low current going to finish off the long tail getting the bank to 100% Full.

Be aware that most solar setups don't put out enough power to heat up water much.

cuffy 16-06-2018 02:37

Re: Solar controller
Yes, with a lack of information difficult to tell

rgleason 17-06-2018 14:02

Re: Solar controller
Some AltE about Solar Controller good information and you tube

(She is pretty clear in her explanations)

Maximum Power Point Tracking Solar Charge Controllers (MPPT) aI have a Genasun MPPT Controller which increases the current when converting a panel from 20v to 14v (approx)

travellerw 17-06-2018 14:58

Re: Solar controller

Originally Posted by cuffy (Post 2650358)

Does anyone know how these work?

How does it know when absorption has finished?
Not much technical info on web site.

Yes.. A very interesting concept, but damn do they seem expensive.

Like the others have said, I would be worried they would leave you with undercharged batteries. I'm guessing that they are installed between your solar controller and the batteries. They most likely have a shunt inside the monitors the current flow. Once the current drops to a set number (probably hard coded), they start diverting the power.

This could also be achieved with a Victron battery monitor and the relay connection.You would use the "Invert Relay" function, so the relay would energize at a set SOC and voltage and de-energize at a set SOC and voltage. Then have the relay turn on another high amperage relay that energizes a 12V heating element. I think this would actually be a better solution as you could at least control those values.

On our boat, we do actually heat water from the solar through our inverter. We have a fairly small water heater (5gal) and only a 500W element in it. 30-45 minutes is enough to heat the water for 2 warm showers.

john61ct 17-06-2018 18:25

Re: Solar controller
There are controllers that include the "load shedding" functionality, often those also capable of handling wind power, which I guess requires that feature.

You do **not** want a design that heats water from power stored in your bank, only from the "free excess" over and above what's being accepted by the batt.

I've seen a DIY version on cheaprvliving forums, I'll keep my eyes out for it.

secessus 19-06-2018 09:41

Re: Solar controller
Not a sailor, but John may be referring to my "opportunity circuit" experiments on CRVL. Mods please delete if this is inappropriate for your forum.

When designing the electrical system for my campervan I installed a redundant 12v circuit alongside the normal house power 12v runs. This second circuit is only energized when there is more power available than needed for critical loads. In my application:

Critical loads: FLA charging, ventilation, LED lighting.
Opportunity loads: charging devices, running laptop, donating power to others, dehumidifier, etc

My first thought was that anytime the charger was in Float we are good to power the circuit. Another time we have excess power is later in Absorption. The most elegant way to do this is probably to poll the controller through its interface (with a pi or arduino?). I'll do this in the future in my Copious Free Time. I think some higher end controllers will also energize the LOAD output when Float is active but I cannot recall now (pre-coffee).

For now I am using ~Vfloat (a little less) as the indicator for excess power. Unfortunately this causes a false positive in Bulk when Vbattery is more than Vfloat but not yet Vabs. I mitigate this issue by chaining a 12v timer to the LVD. I am somewhat overpaneled so a delay of less than an hour is enough to ensure I am far enough into Absorption that falling acceptance means power is available for opportunity loads. The timer is not intended to run loads directly, so it triggers a relay.

LVD --> delay --> relay == opportunity circuit energized
disconnect: 12.7v
reconnect: 13.7v (just under my Vfloat == 13.8)

It has worked well for me. Before dawn my bank is usually 80-100% SoC because the opportunity circuit/loads were shut off when the sun went down.

john61ct 23-06-2018 05:58

Re: Solar controller
Super, thanks Frater

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