PWM or MPPT?

earlvillestu wrote:
I just took delivery of a 120W portable solar panel from SolarBlvd, which I will use to charge a single AGM Group 31 with an AH capacity of 105. We have a popup and are minimal electricity users, so I believe this will meet our needs.

The panel specs are Vmp 18.0, Imp 6.67, Voc 22.7, Ioc not specified. I plan to ditch the cheesy supplied controller and put a 3-stage adjacent to the battery.

My question is, would there be a significant benefit to buying an MPPT controller over a good PWM? I know that if I expand the number of panels in the future, there are benefits to MPPT, but assuming I'm planning to stay with the current setup, is it worth the substantial extra cost?

http://www.solarblvd.com/Solar-Panels-&-Systems-12-Volt-Solar-Panels/c1_269/p2756/W-Solar-120-Watt-Foldable-12-Volt-Solar-Panel/product_info.html?osCsid=5bfff18c08bc1aef8f51655eae63fdba

Double check your figures, I get something different from what you are showing. VMP 17.2v and IMP 6.98 Amps. VOC 21.8v ISC 7.76 Amps


Stick with the PWM. There are other programmable PWM options like a WEN charge controller version 1.2 that now allow you to program additional "bulk" type voltage into your battery, for 12 to $15 on Ebay.

http://www.ebay.com/itm/Digital-PWM-10A-Solar-Charge-Controller-Regulator-12V-24V-Autoswitch-Solar-Panel-/171177553544?pt=LH_DefaultDomain_0&hash=item27dafa2e88

Just 2 weeks ago, at 34N, I ran some tests on mine, and had no trouble getting 6.33 to 6.56 amps measured, just pointing the panel and aiming it at the sun. Summer time is another matter, longer days, more chargeable hours... with the sun where it is now, I'd be lucky to get 30 to 35 Ah in a day. Sunlight hours are a lot longer after March 21st to Sept 23.

Get yourself one of those RV charger meters on Ebay for $12 to $15 from China, and set yourself up to be able to measure your charge per day. Your voltage in the morning, before the panels start to kick in charging, will tell you your state of charge. 12.0 to 12.1V is about 50%