I am setting up a house battery bank with two group 31 AGM batteries in parallel, and would appreciate recommendations on a MTTP charge controller.
Thanks, Duke
Thanks, Duke
Solar Charge Controller
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What size panel? (watts)
You may want to read this paper put out by Morningstar. (They build both kinds of controllers, PWM & MPPT)
"PWM Over MPPT?
The preceding discussion of PWM vs. MPPT may cause some to wonder why a PWM controller would ever be chosen in favor of an MPPT controller. There are indeed instances where a PWM regulator is a better choice than MPPT and factors which will negate advantages the MPPT may provide. The most obvious consideration is cost. MPPT controllers will cost more than their PWM counterparts. When deciding on a controller, the extra cost of MPPT should be analyzed with respect to the following factors.
Low power (specifically low current) charging applications may have equal or better energy harvest with a PWM controller. PWM controllers will operate at a relatively constant harvesting efficiency regardless of the size of the system (all things being equal, efficiency will be the same whether using a 30W array or a 300W array). MPPT regulators commonly have noticeably reduced harvesting efficiencies (relative to their peak efficiency) when used in low power applications. Efficiency curves for every Morningstar MPPT controller are printed in their corresponding manuals and should be reviewed when making a regulator decision. (Manuals are available for download on the Morningstar website www.morningstarcorp.com.)
As explained in the Environmental Considerations section, the greatest benefit of an MPPT regulator will be observed in colder climates (Vmp is higher). Conversely, in hotter climates Vmp is reduced. A decrease in Vmp will reduce MPPT harvest relative to PWM. Average ambient temperature at the installation site may be high enough to negate any charging advantages the MPPT has over the PWM. It would not be economical to use MPPT in such a situation. Average temperature at the site should be a factor considered when making a regulator choice (See Appendix).
Systems in which array power output is significantly larger than the power draw of the system loads would indicate that the batteries will spend most of their time at full or near full charge. Such a system may not benefit from the increased harvesting capability of an MPPT regulator. When the system batteries are full, excess solar energy goes unused. The harvesting advantage of MPPT may be unnecessary in this situation."
http://www.morningstarcorp.com/en/support/library/MS.WP.MPPTvPWM.01.EN.pdf
The efficiency of of MPPT controllers decline somewhat depending on the details of a particular application. Cost, lower current applications and even temperatures where the system will be operating should be taken into consideration.
You may want to read this paper put out by Morningstar. (They build both kinds of controllers, PWM & MPPT)
"PWM Over MPPT?
The preceding discussion of PWM vs. MPPT may cause some to wonder why a PWM controller would ever be chosen in favor of an MPPT controller. There are indeed instances where a PWM regulator is a better choice than MPPT and factors which will negate advantages the MPPT may provide. The most obvious consideration is cost. MPPT controllers will cost more than their PWM counterparts. When deciding on a controller, the extra cost of MPPT should be analyzed with respect to the following factors.
Low power (specifically low current) charging applications may have equal or better energy harvest with a PWM controller. PWM controllers will operate at a relatively constant harvesting efficiency regardless of the size of the system (all things being equal, efficiency will be the same whether using a 30W array or a 300W array). MPPT regulators commonly have noticeably reduced harvesting efficiencies (relative to their peak efficiency) when used in low power applications. Efficiency curves for every Morningstar MPPT controller are printed in their corresponding manuals and should be reviewed when making a regulator decision. (Manuals are available for download on the Morningstar website www.morningstarcorp.com.)
As explained in the Environmental Considerations section, the greatest benefit of an MPPT regulator will be observed in colder climates (Vmp is higher). Conversely, in hotter climates Vmp is reduced. A decrease in Vmp will reduce MPPT harvest relative to PWM. Average ambient temperature at the installation site may be high enough to negate any charging advantages the MPPT has over the PWM. It would not be economical to use MPPT in such a situation. Average temperature at the site should be a factor considered when making a regulator choice (See Appendix).
Systems in which array power output is significantly larger than the power draw of the system loads would indicate that the batteries will spend most of their time at full or near full charge. Such a system may not benefit from the increased harvesting capability of an MPPT regulator. When the system batteries are full, excess solar energy goes unused. The harvesting advantage of MPPT may be unnecessary in this situation."
http://www.morningstarcorp.com/en/support/library/MS.WP.MPPTvPWM.01.EN.pdf
The efficiency of of MPPT controllers decline somewhat depending on the details of a particular application. Cost, lower current applications and even temperatures where the system will be operating should be taken into consideration.
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Yep size and type are needed. We started with a PWM controller on a 40 watt panel ....
http://purplesagetradingpost.com/sumner/macgregor/outside-22.html
....and now have a MPPT controller ...
http://purplesagetradingpost.com/sumner/macgregor2/outside-33.html
.... on 200 watts of panels (3 panels, same cell type and same working voltages). We are using a Blue Sky MPPT 2512iX 25 amp, 3 stage controller but have flooded batteries.
Make sure the controller will work with the AGM's you have. I don't think ours will as it was designed for flooded cells. Also for the highest efficiency the panels should be the same or at least the same cell type and working voltage.
They claim up to 30% efficiency with the MPPT, but the key words here are "up to". We went with the MPPT not expecting 30% all of the time, but any increase we did get would sure be benificial considering that we run a frig and the computer a lot. There is only so much room on a boat for panels, so if you want the maximum potential I'd spend the extra on the MPPT. We have 480 watts of panels on the Endeavour and got the next larger MPPT controller from Blue Sky for that boat.
Good luck,
Sum
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