[RE-wrenches] Fw: Xantrex C-40 Drifting

Thu May 21 09:25:28 PDT 2015

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*
> <jarmo.venalainen at schneider-electric.com>  |   *Site:** www.Xantrex.com*
> <http://www.xantrex.com/>  |   *Address:* 3700 Gilmore Way, Burnaby, BC
> V5G4M1
>   <http://www.xantrexrebate.com/>  <http://www.xantrex.com/>
> <https://www.facebook.com/Xantrex> <https://twitter.com/Xantrex>
> <https://twitter.com/Xantrex>
>
>
> *** Please consider the environment before printing this e-mail
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>
>
>  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*
> <jarmo.venalainen at schneider-electric.com>  |   *Site:*
> <http://www.xantrex.com/>*www.Xantrex.com* <http://www.xantrex.com/>   |
>   *Address:* 3700 Gilmore Way, Burnaby, BC V5G4M1
> [image: []] <http://www.xantrex.com/>  [image: []]
> <https://www.facebook.com/Xantrex>[image: []]
> <https://twitter.com/Xantrex>[image: []] <https://twitter.com/Xantrex>
>
>
> *** 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*
> <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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