Solar info required.
Submitted: Saturday, Sep 16, 2017 at 17:26
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TTTSA
Howdy,
Just redoing the electrics in our camper and have a query that I can't find an answer to, any help would be great.
2X135AH deep cycle batteries fitted, Redarc 1240D BCDC charger just installed to camper.
Previously had 2x small cranking batteries on the camper, charged by Redarc 1225LV BCDC under bonnet of vehicle.
Used to plug 200W solar panels into 1225lv under bonnet and charge batteries that way while stationary.
My question is, if I am using a BCDC to actually charge the batteries, do I need 200W solar panels? Couldn't I just use a 50W solar panel to power the BCDC to charge the batteries?
I would like to get rid of the 200W panels as they take up a lot of room and are heavy.
BCDC requires minimum of 9V to operate, would 50W solar panels manage this or am I thinking off the planet?
Regards
Peter
Reply By: Allan B (Sunshine Coast) - Saturday, Sep 16, 2017 at 22:45
Saturday, Sep 16, 2017 at 22:45
.
The Redarc specification that their BCDC chargers will operate "down to 9v input" needs to be fully understood.
The purpose of the charger is to overcome the voltage drop in the cabling from the point of supply which is the terminals of the cranking battery.
Due to volt-drop in the cabling, the voltage input at the charger may fall
well below the cranking battery terminal voltage and the charger will continue to properly operate with an input as low as 9 volts. However, the charger needs to determine if the voltage at the cranking battery is at least 12.7v (typically). It does this by briefly pausing the charging every 100 seconds. When paused there is no current to cause cable volt-drop so the charger is now looking at the true voltage at the cranking battery terminals. If it is greater than 12.7v charging continues but if less then charging is suspended. The charger will not operate from a supply source (such as solar) less than 12.7 volts.
In this way the charger is prevented from drawing current from the terminals of the cranking battery below nominally 12.7v. Note that this voltage setting varies slightly with the charger model and that the "-IGN" models also shut down when the ignition circuit is off.
AnswerID:
613821
Follow Up By: RMD - Sunday, Sep 17, 2017 at 10:36
Sunday, Sep 17, 2017 at 10:36
Allan
If solar is used, won't the BCDC unit still charge the aux battery irrespective of the vehicle start battery voltage?
TTTSA said he used the solar to charge the batteries previously.
I was confused as to what he meant by cutting 200w solar down to 50w solar and still expecting the 50 w to do similar work in similar time.
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Follow Up By: TTTSA - Sunday, Sep 17, 2017 at 12:27
Sunday, Sep 17, 2017 at 12:27
Hi RMD
I was hoping to be able to use 50W panel to power the charger, I wasn't sure if it made any difference using 50W or 200W to satisfy the charger and still get the same output from the charger.
Wishful thinking it seems.
Thanks
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884368
Follow Up By: Allan B (Sunshine Coast) - Sunday, Sep 17, 2017 at 12:39
Sunday, Sep 17, 2017 at 12:39
RMD,
The solar will continue to feed via the BCDC only so long as the unladen solar voltage stays above 12.7 volts. Should that voltage fall below 12.7 the BCDC will cut out until it rises to above 13.2 volts. (These voltages are typical and vary by model)
As to the 200W/50W confusion, I think TTTSA has now realised his error.
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