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electrical:charge_controller [2016/12/31 19:40]
frater_secessus [Solar charge controllers] |
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| Counterintuitively, the job of a solar charge controller (CC) is to keep the batteries from being //over//charged. [[electrical:solar panel|Solar panels]] run at higher voltages than batteries, often at voltages high enough to damage the batteries. The CC provides the correct amount of power the battery needs at the correct time; this is called [[electrical:smart_charger|smart or three stage charging]]. | |
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| ===== PWM and MPPT ===== | |
| The two main types of CCs are Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT). As is the case with [[electrical:inverter|inverters]], one costs much less than the other but may not work as well in some cases. It is the subject of [[http://www.cheaprvliving.com/forums/Thread-looking-for-a-cheap-charge-controller-for-a-single-100w-panel|Holy Wars, particularly concerning small PV systems]]. The RVer will have to be comfortable with their own decision. | |
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| A **PWM charger runs the [[electrical:solar panel|solar panels]] at the voltage needed to charge the battery at a given time**. This is unlikely to be at the panel's rated output but that may not be a practical concern for reasons given below. | |
| An **ideal scenario for PWM** might be: low voltage panels (nominal 12v) in parallel, hot ambient conditions, and shallow [[electrical:depth_of_discharge|Depth of Discharge]], a surplus of sunlight, lots of room for extra panels, limited funds. | |
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| A **MPPT charger runs the panel at panel's maximum power output** under present conditions then **downconverts the voltage to match charging needs**. This can yield a significant increase over PWM. Ohm's Law requires the amperage increase when the voltage decreases, so **the MPPT charger can provide more amps to the battery** than PWM //if// the charging stage warrants. Since the bulk phase is the only phase that uses heavy amperage the increase may only be noticeable during that phase. Additionally, **around 2% of the max power is consumed during downconverting**. Overall, an MPPT CC will generally harvest 10-30% more power from the panels than PWM. Note that it cannot harvest more than the panels' rated power, only more than PWM would. | |
| An **ideal scenario for MPPT might be**: high voltage panels in series, cold ambient conditions, heavy battery use, limited or poor quality sunlight, limited room for panels, no limit on funds. | |
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| ===== sizing your charge controller ===== | |
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| Again as with inverters, sizing the controller correctly will help reduce wasted parasitic draw. | |
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| ===== what experts recommend ===== | |
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| **HandyBob** recommends only the [[http://amzn.to/2gz4sr9|Morningstar Tristar PWM]] (or [[http://amzn.to/2fekXTv|Tristar MPPT]] if running at least 600w of panel). He runs identical panels in series runs of two panels.((https://handybobsolar.wordpress.com/rv-solar-quick-answer/)) | |
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| **akrvbob** (Bob, guru and forum admin) recommends MPPT controllers: [[http://amzn.to/2gc3cX3|Blue Sky]], [[http://amzn.to/2fekXTv|Morningstar Tristar]], [[http://amzn.to/2gc1Xat|Outback]], and [[http://amzn.to/2gtf8qr|Midnight Solar]]. He prefers Blue Sky.((http://www.cheaprvliving.com/forums/Thread-the-solar-charge-controller-MAZE?pid=123149#pid123149)) | |
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| He has also mentioned the [[http://amzn.to/2gtbixj|Renogy 200w kit]] for beginners or those with minimal power needs (including a 12v refrigerator).((http://www.cheaprvliving.com/forums/Thread-charging-marine-batteries?pid=128379#pid128379)) | |
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| Charging guru **SternWake** uses a [[http://amzn.to/2fvdKPV|Blue Sky SB2512i]] with a IPN Pro battery monitor. He has said he wishes he had spent the $30 extra to get the SB2512ix which has built in ability to adjust voltage setpoints, compensate for temperature, etc.((http://www.cheaprvliving.com/forums/Thread-Energy-Budget?pid=90197#pid90197)). He now uses a power supply as a manual charger when shore power is available. | |
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| There has been a flurry of internet interest in the inexpensive Chinese [[http://amzn.to/2fvciNu|Tracer MPPT controller]]. They appear to be the least expensive real MPPT units available although there is not yet enough information to assess quality and longevity. | |
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