Hi: My thought is that the mechanism by which the battery voltage slowly rises under the influence of a solar module connected through a C40 type PWM controller is due to the fact that the PWM type controllers don't regulate voltage but rather connect the full output voltage of the module/array to the battery on a pulse width limited basis.
Seems that those high voltage pulses, brief as they may be thanks to the PWM, are still none the less able to slowly raise the resting terminal voltage of at least some types of AGM batteries. I don't know enough about batteries to know if that is a problem or not. Perhaps its perfectly normal as almost any new lead acid battery will retain a higher than normal measurable "ghost voltage" just after it has been fully charged. JARMO _____________________________________________________________________________________ Jarmo Venalainen | Schneider Electric | Xantrex Brand | CANADA | Sales Application Engineer Phone: +604-422-2528 | Tech Support: 800-670-0707 | Mobile: +604-505-0291 Email: jarmo.venalai...@schneider-electric.com | Site: www.Xantrex.com | Address: 3700 Gilmore Way, Burnaby, BC V5G4M1 *** Please consider the environment before printing this e-mail From: Drake <drake.chamber...@redwoodalliance.org> To: RE-wrenches <re-wrenches@lists.re-wrenches.org>, Date: 05/20/2015 11:11 AM Subject: Re: [RE-wrenches] Fw: Xantrex C-40 Drifting Sent by: "RE-wrenches" <re-wrenches-boun...@lists.re-wrenches.org> The modules are Sunwise 22 V, 40 W modules. The model number of the modules is SW-S40P SWT. The are wired in series for a 24 V nominal system. That would be an mppt voltage of 44 V on a system that directs batteries to absorb at 29.4 volts. I'm not sure what the NOCT voltage would be, but it would seem like it would be an ok fit? I think you are on the right track with the MPPT charging graph. The CC likely allows pulses of full charge to hit when the batteries are at their maximum set point voltage. Would a very short pulse of high voltage be a problem of a VRLA battery? Could any significant gassing take place? Thanks, Drake At 06:04 PM 5/19/2015, you wrote: Hi: We haven't changed anything the in C40. The essence of my idea was that perhaps the "trouble" systems are the ones which have much higher module Voc versus battery Vfloat. JARMO _____________________________________________________________________________________ Jarmo Venalainen | Schneider Electric | Xantrex Brand | CANADA | Sales Application Engineer Phone: +604-422-2528 | Tech Support: 800-670-0707 | Mobile: +604-505-0291 Email: jarmo.venalai...@schneider-electric.com | Site: www.Xantrex.com | Address: 3700 Gilmore Way, Burnaby, BC V5G4M1 *** Please consider the environment before printing this e-mail From: Ray Walters <r...@solarray.com> To: RE-wrenches <re-wrenches@lists.re-wrenches.org>, Date: 05/19/2015 11:00 AM Subject: Re: [RE-wrenches] Fw: Xantrex C-40 Drifting Sent by: "RE-wrenches" <re-wrenches-boun...@lists.re-wrenches.org> Hi Jarmo; Early solar systems actually tried to use the principle of matching array Vmpp to battery voltage in lieu of charge controllers. The biggest issue is that when it is is hot the module voltage can drop below the battery voltage needed, and when its cold the voltage will still be too high. Batteries were either over charged or never reached full charge depending on the conditions. I've used the C40 successfully for decades, so I'm wondering if the circuitry changed recently, or if different tolerance components were substituted that may be causing the drift? Thanks, R.Ray Walters CTO, Solarray, Inc Nabcep Certified PV Installer, Licensed Master Electrician Solar Design Engineer 303 505-8760 On 5/19/2015 10:31 AM, jarmo.venalai...@schneider-electric.com wrote: Hi: I didn't know that there were systems out there where a PWM charge controller such as the C-40 was producing an unhealthy, high battery voltage. Since there are, I may have a possible explanation. The C-series and other PWM type charge controllers operate by PWM whereby they very very quickly connect/disconnect the solar module to the battery bank. The amount of time which the module is connected to the array is the PWM on-period. These controllers do not have the ability to "smooth out" the output voltage. All they can do is apply the full module voltage OR not a ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________ _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. ______________________________________________________________________ _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
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