SES Flexcharge?

[seneysolar]

Does anyone have a SES Flexcharge charge controller in use?

These are made here in Michigan. They claim superior efficiency without being mppt design.

What is it?

Flexcharge LLC

www.flexcharge.com

 

[highwaypirate]

I checked out their Flexcharge NC25A and ran into this little bit:

"With a peak charging efficiency of 99.9% and an operating current of only 4mA, more of the systems charging energy will get through a NC25A into your batteries than with any other controller on the market. Models are available for charging 12V, 24V, 36V, and 48V systems. Use with Lead Acid, Gel, or Flooded NiCad battery technologies. Not for Lithium."

I'm still scrolling through their site, although if the rest of their products aren't designed for lithium these might be best suited for projects that still utilize FLA/SLA batteries.

EDIT: Yes, it looks like every product of theirs states not to be used on lithium chemistries.

 

[seneysolar]

They have a unique way of expanding the system with using just 1 charge controller and these "expansion kits" , very interesting

 

[highwaypirate]

They are interesting. I would recommend checking their products out if one was building a smaller-sized system and DIY mini-projects. I might even consider that NC25A a try for my 18AH AGM.

 

[HarryN]

They work just fine - for AGM and similar. It isn't compatible with Li batteries.

They are perfect for when there is not a very large difference between the solar panel voltage and battery voltage.

I have used the NC25A units. There is a variation that helps with temp compensation in cold weather.

Efficiency is similar to a pwm unit. I have one in the 24 volt x 100 amp-hr Lifeline battery based power system in my explorer.

There is a little more voltage range occurring during the charge cycle, which can be good for knocking off deposits on plates. Just make sure your devices can deal with it. It has not been a problem for me, but I am mostly using the 1000 watt inverter and a DC - DC converter for a 12 volt power outlet.

This type of charger and PWM are ideal - even better than MPPT if the panel voltage is 5 ish volts above the battery voltage, for instance an 18 volt Vmp panel and a 12 volt battery. ( charge voltages are in the 14 - 16 volt range depending on battery temperature )

If the panel voltage is at least 10 - 15 volts higher than the battery voltage, then it makes sense to use MPPT. Without that 10 - 15 volts, MPPT does not really make any sense.

 

[seneysolar]

They work just fine - for AGM and similar. It isn't compatible with Li batteries.

They are perfect for when there is not a very large difference between the solar panel voltage and battery voltage.

I have used the NC25A units. There is a variation that helps with temp compensation in cold weather.

Efficiency is similar to a pwm unit. I have one in the 24 volt x 100 amp-hr Lifeline battery based power system in my explorer.

There is a little more voltage range occurring during the charge cycle, which can be good for knocking off deposits on plates. Just make sure your devices can deal with it. It has not been a problem for me, but I am mostly using the 1000 watt inverter and a DC - DC converter for a 12 volt power outlet.

This type of charger and PWM are ideal - even better than MPPT if the panel voltage is 5 ish volts above the battery voltage, for instance an 18 volt Vmp panel and a 12 volt battery. ( charge voltages are in the 14 - 16 volt range depending on battery temperature )

If the panel voltage is at least 10 - 15 volts higher than the battery voltage, then it makes sense to use MPPT. Without that 10 - 15 volts, MPPT does not really make any sense.

Then how do they accept up to 140v of pv input and claim 99.5% efficiency??.

 

[Hedges]

Seems to be PWM, and optional diversion load for turbine sources.

PWM charge controller is highly efficient, just milliohms or less series resistance between PV panels and battery.
The PV panels? Not so efficient unless battery voltage just happens to be exactly Vmp (which varies with temperature.)

Avoids high frequency switching noise, so lower EMI at higher frequencies.

Then how do they accept up to 140v of pv input and claim 99.5% efficiency??.

Too small to have an inductor for 25A SMPS.
I'd guess just a transistor able to hold off more than 140V. Used with a 48V battery, PV system still works with half the panels shaded.

Efficiency of the SCC is high, near zero power dissipation. Power harvested from panels greatly reduced.

 

[seneysolar]

Used with a 48V battery, PV system still works with half the panels shaded.

Thanks! - Now this has my wheels turning. time for another experiment

 

[Hedges]

I'm not saying that like it's a good thing!
This just seems to be PWM with high voltage transistors.
If you've got that much voltage headroom, MPPT will harvest more watts.

 

[seneysolar]

Understood. I just never gave thought to a 48v pwm. I have 2 panels that would series up nicely for that application

 

[HarryN]

@Hedges is more or less correct.

Let's take an example to make it easier to see how it works.

I have some experience with solarland panels, so here is an example panel data sheet from the web site. It is just an example, nearly all solar panels will more or less behave similarly.

https://solarlandusa.com/content/Product spec sheet/SLP200S-12U 200031201A.pdf I also attached it for convenience.


_______________________

Look at the voltage / current curve on the data sheet. What is shows is that over quite a range of temperature and output voltage, the current will remain more or less the same. ~ 12 amps on a very bright sunny day. On a very overcast day, it might drop to 2 amps and the voltage will also drop some.

______________

So now imagine that you have this solar panel directly feeding your 50% discharged AGM battery through fuses for safety reasons. The solar panel output at 12 amps is a small fraction of what the battery can accept in terms of bulk charging.

For fun and as an example of this, I built a small test fixture so that it is easier to follow:

Small test fixture

Sometimes it is easier to show people things in photos than to describe them. So I made a little test fixture from left over parts, nothing fancy. In this case, some people asked about methods of dealing with pre-charging the capacitors on the input stage of inverters, and I had suggested that...

diysolarforum.com

The battery will pull down the panel voltage to match what it is at while it charges. Literally all of the power coming off of that panel ( minus small losses in wires and fuses) will be pumped into the battery for charging.

You can even use this as an emergency method to charge a starter battery in the middle of no where.

The limitation is that at some point the battery will reach full charge, and you will need to manually disconnect the solar panel from it.

What the flexcharge does is that it monitors this voltage and turns on an off an internal relay to control the charging. They use a relay to get very low impedance and RF noise in a small package.

____________

So the efficiency is very high ( it is a hard connection ). What is lost is small delta in voltage being turned into useful power that is from roughly 15 to 14 volts that the panel could in theory produce, but in reality, there are wire losses, etc so it is not all that significant for this example.

 

[HarryN]

If instead you used a PWM solar charge controller like a Bogart, it is turning on / off a FET fairly fast, so you won't see as much voltage spiking like you get with the flexcharge. ( look at their data sheet )

The losses for this type of configuration again are fairly small.

Comparing this to a fairly common MPPT charge controller like a victron 100 / 30 can be insightful as to when each type is ideal to use.

The 100 / 30 requires IIRC a 5 volt difference between the Voc of the panel and the V battery to turn on. If you were to use a 100 / 30 in that application, it would not turn on in nearly as overcast of sunlight as the flexcharge or Bogart as they only need something like a 1 volt delta.

They will collect sunlight in conditions that the 100 / 30 will not.

On the other hand, if you put 2 or 3 of those panels in series to raise the panel array voltage, then the 100 / 30 will give far superior results.