Solar Panels Isolation
Submitted: Saturday, Feb 21, 2015 at 21:21
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Member - Bigred13
Hi to all ,just throwing this out there, to see if anyone has some thoughts on this .
I have 140 Watt solar panels fixed on my caravan ,and I also now have 2x200 Watt portable solar panels which I will connect via 6 B&S cables to my Redarc BMS along with the fixed panels ,what I am wanting to know is ,if the van is parked in the shade and the portables are in the sun, I am assuming as they are hooked together ,the portable panels will not be putting in the max amount of power ,due to some part of the system being in shade ??
What I would like to know is ,in that situation ,can I isolate the van panels from the rest via an on/off switch ,and will it cause problems to the van panels not being used ?? .I have bypassed the voltage controller on all panels ,so as to give the BMS with its MPPT function full power from the panels .
I am open to all thoughts
Big Red 13
Reply By: HKB Electronics - Saturday, Feb 21, 2015 at 21:36
Saturday, Feb 21, 2015 at 21:36
You don't need to use blocking diodes, blocking diodes are used to
prevent a battery being discharged by the panels at night, if you have
a controller connected between the panels and the battery that won't happen.
The panel that is shaded will might draw some current from the one that is not but it is not worth worry about some for of isolation in my opinion.
AnswerID:
546352
Follow Up By: Member - Bigred13 - Saturday, Feb 21, 2015 at 22:16
Saturday, Feb 21, 2015 at 22:16
Thanks HKB,
Yes I guess that is what I meant if I put in an isolator , will that damage the panels if they are producing and have no where to go?
FollowupID:
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Follow Up By: oldtrack123 - Saturday, Feb 21, 2015 at 23:02
Saturday, Feb 21, 2015 at 23:02
Hi Big red
No ,open circuit will not damage the panels
FollowupID:
834083
Reply By: Bob Y. - Qld - Sunday, Feb 22, 2015 at 15:00
Sunday, Feb 22, 2015 at 15:00
Big Red,
If your BMS is the same as mine, 12v-15amps, then it can only "use" 240 watts of
solar power, at any time. Even though the 'van may be in the shade, the 2 x 200 watt panels will exceed the BMS output. I have a 160w panel on top of my camper, and even in the shade, the meter shows power going into the batteries, the little battery meter shows constant input. Solar panel volts are 19-20v.
An article on Redarc site, said if you have solar output greater than the BMS can use, as you have, then you may get a longer maximum charging period through the day, than if you only had 240w. This would useful if part of day, say early morning, was overcast and you needed to get max amount of amp-hours before dark.
Bob
AnswerID:
546395
Follow Up By: Member - Bigred13 - Sunday, Feb 22, 2015 at 15:25
Sunday, Feb 22, 2015 at 15:25
Hi Bob Y,
Thanks for your reply, I rang Redarc re the 400W panels plus the 140 W and they told me it was not a problem for the BMS ,as it is regulated to 15 Amps input , and as you said it will charge longer through the day ,which is great for the reason you have stated .
My concern was if some were shaded ,it may drop the input ,but as there is plenty of capacity it may not be a problem .By the way what amps does your 160 W put in on a sunny day ???.
Thanks again
Big Red
FollowupID:
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Follow Up By: Bob Y. - Qld - Sunday, Feb 22, 2015 at 17:07
Sunday, Feb 22, 2015 at 17:07
Big Red,
Have the panel mounted on pack rack, and using a couple of gas struts, can angle it to get higher output. It folds down for travelling.
Panel in ideal position
On the day that photo was taken, noticed about 8.6 amps, about mid afternoon. Would hope for a bit better than that in cooler weather. Still have a 60w panel to fit in front of this one, mounted almost flat, and have yet to purchase a 120 or 140w folding panel to assist the others, when camped for a while.
I find the BMS is very good, and provides plenty of info, as
well as the 3 modes for charging. In a perfect world, another 10-15 amps input would be handy, but am sure it will do the job.
Bob
FollowupID:
834121