Small MPPT Charge Controller?

[sensij]

And 15amp is on the low side of properly charging that 205Ah battery system but based on 195w and Vmp = 37v you are only getting ~ 5amps (195w / 37v = 5.3a) for each panel which is a little over 10A total. That is not enough for your battery system."

Would that not be closer to 15A into the batteries? 390w/24v = 16.25amps minus loses. Regardless, I understand that is on the low side for charging amps, but that battery bank spends 7 months a year in float. It does sound like the Epever may be the way to go though.

The 10 A is his estimate of the charge you might be getting from the PWM controller.

[NorthRick]

And 15amp is on the low side of properly charging that 205Ah battery system but based on 195w and Vmp = 37v you are only getting ~ 5amps (195w / 37v = 5.3a) for each panel which is a little over 10A total. That is not enough for your battery system."

Would that not be closer to 15A into the batteries? 390w/24v = 16.25amps minus loses. Regardless, I understand that is on the low side for charging amps, but that battery bank spends 7 months a year in float. It does sound like the Epever may be the way to go though.

[SunEagle]

400 W of panels will not produce more than 15 A of charge current on a 24 V system. Even if the panels were producing STC wattage (they probably won't for any meaningful length of time), the charge controller efficiency would eat up enough to keep the output to 15 A. That said, the Epever 20 A CC with remote monitor is $120-$130, and going smaller doesn't save much unless you go all the way down to 10 A, which is too small for this system.

I guess when you figure in the inefficiency of the system 400w will work with a 15A MPPT CC and a 24v battery system.

I just didn't want the OP to try to save a few bucks and limit the CC if they find out 400watts is not enough to run their system. Not worth painting yourself into a corner if you don't have to.

[sensij]

Usually if you have more than 200 watts of panels and a PWM CC you are losing about 33% of the wattage. Going to an MPPT should use more of the panel wattage but with ~ 400 watts a 15amp CC might be cutting it close even for a 24Volt battery system.

400 W of panels will not produce more than 15 A of charge current on a 24 V system. Even if the panels were producing STC wattage (they probably won't for any meaningful length of time), the charge controller efficiency would eat up enough to keep the output to 15 A. That said, the Epever 20 A CC with remote monitor is $120-$130, and going smaller doesn't save much unless you go all the way down to 10 A, which is too small for this system.

[SunEagle]

Usually if you have more than 200 watts of panels and a PWM CC you are losing about 33% of the wattage. Going to an MPPT should use more of the panel wattage but with ~ 400 watts a 15amp CC might be cutting it close even for a 24Volt battery system.

And 15amp is on the low side of properly charging that 205Ah battery system but based on 195w and Vmp = 37v you are only getting ~ 5amps (195w / 37v = 5.3a) for each panel which is a little over 10A total. That is not enough for your battery system.

[sensij]

EpEver's Tracer series offers a good entry level mppt at a lower price point.

[NorthRick]

I have a small solar system for our greenhouse, primarily to power circulation and exhaust fans. It has two 195 watt panels with a Vmp of 37v. The battery bank is flooded lead acid - 205ah at 24v. Currently I have a fairly basic SunSaver PWM charge controller (SS-20L-24V).

The issue is that the actual fan loads are higher than what I had estimated when setting up the system. This comes into play latter in our growing season when we typically get more cloudy weather. Several times I have had to disconnect the load for a day or more to allow the battery bank to get back up to full charge.

My thought for a fix is to replace the PWM charge controller with a MPPT. I believe with my current setup the PWM is leaving about 25% of the available power on the roof. I am looking at getting a SunSaver MPPT (SS-MPPT-15L) to replace the PWM controller. It is about $210 online. I've seen cheaper ones but not sure about them.

Two questions:

1) Does switching from a PWM to MPPT seem like the best fix for my situation?

2) Are there other small MPPT charge controllers I should consider?