[RE-wrenches] Fw: Xantrex C-40 Drifting
Jarmo.Venalainen at schneider-electric.com
Jarmo.Venalainen at schneider-electric.com
Thu May 21 09:47:43 PDT 2015
Hi:
The C40 circuit is a really simple circuit made up of a set of resistors,
capacitors, op-amps, a time-base crystal and PWM. Simple electronic
components, so I don't see drift issues, except maybe under large
temperature changes.
What does change a lot is the intensity of the sun and thereby the Voc,
Vmp, Imp, etc. of the module/array.
Given that the PWM applies the varying "raw" available array
voltage/current directly to the battery, I think that's how the output
voltage variation issue arises.
It's an idea. It may be right or wrong. Some trials would be needed to
prove or disprove it.
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.venalainen at schneider-electric.com | Site: www.Xantrex.com
| Address: 3700 Gilmore Way, Burnaby, BC V5G4M1
*** Please consider the environment before printing this e-mail
From:
Steve Bell <sbell at morningstarcorp.com>
To:
RE-wrenches <re-wrenches at lists.re-wrenches.org>,
Date:
05/21/2015 09:25 AM
Subject:
Re: [RE-wrenches] Fw: Xantrex C-40 Drifting
Sent by:
"RE-wrenches" <re-wrenches-bounces at lists.re-wrenches.org>
Hello Wrenches,
I have been following this C-40 drifting thread. From my personal
experience the C-40 always had about a 0.2 to 0.4 volt drift since the
early days (1994-95). This was on a 48-volt system, so the drift might be
less at lower battery voltages. The drift was not a simple
mis-calibration; one day 0.3 volt high, another day 0.4 volts low.
I don't know if this is a component of the problem, but thought I would
mention it.
Best Regards,
Steve Bell
On Wed, May 20, 2015 at 7:34 PM, <Jarmo.Venalainen at schneider-electric.com>
wrote:
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.venalainen at 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.chamberlin at redwoodalliance.org>
To:
RE-wrenches <re-wrenches at 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-bounces at 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.venalainen at 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 <ray at solarray.com>
To: RE-wrenches <re-wrenches at 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-bounces at 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.Venalainen at 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
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