mppt charger
Submitted: Monday, Mar 27, 2017 at 17:35
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Member - wozza
I have 3 12v solar panels 1x160w and 2x300 w they are wired in parallel into a Tracer 3210A 30amp MPPT regulator charging 2 120ah batteries. My question is would it be more efficient to have the panels in series instead of parallel.
Reply By: HKB Electronics - Monday, Mar 27, 2017 at 18:10
Monday, Mar 27, 2017 at 18:10
It would be more efficient to have them in series, the problem is the mix match of the 160W and the 300W panels. Even if the have similar OC voltages your going to basically lower the max current to that of the 160W panel.
Your present setup would produce around 36A so you excess solar in good conditions.
You could just have the two 300W panels in series which would give you similar output I would guess to what your now getting with the three in good conditions.
In poor conditions you might do better with the three in parallel when the batteries are in a high state of charge.
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Follow Up By: Member - wozza - Monday, Mar 27, 2017 at 18:18
Monday, Mar 27, 2017 at 18:18
Thanks for that i think i will save myself the trouble and leave things as they are.
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Follow Up By: RMD - Monday, Mar 27, 2017 at 21:49
Monday, Mar 27, 2017 at 21:49
You would already be getting around the max for the regulator and two 300W panels in series wouldn't pass 30 amp through themselves. The max OC voltage would be near or more than 40volts. Will your regulator cater for that.
AS it is will work just fine and use the MPPT feature quite
well.
That amount of panel for 2 x 120ah should see them fully charged most of the time with normal amp loadings.
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Reply By: Member - Boobook - Tuesday, Mar 28, 2017 at 09:36
Tuesday, Mar 28, 2017 at 09:36
You should also put blocking diodes in series with each panel if some are subject to sun and some shade at the same time.
When solar panels are placed in parallel, those in the sun generate power, those in the shade consume power. If you don't have blocking diodes, the shaded panels will consume much of the power you generate. Worse, they are not designed to do this and can overheat causing damage.
This is different to the normal parallel bypass diodes installed in many panels.
You should get schottky diodes to reduce the power loss in them.
You can get them at Jaycar / ebay.
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Follow Up By: HKB Electronics - Tuesday, Mar 28, 2017 at 12:28
Tuesday, Mar 28, 2017 at 12:28
Hi Tony,
I did some testing a while back with 100W panels, with 22V being feed to the panel its draw was very small ,it worked out that you would loose more across the series diodes than you would loose form the back flow into the panels.
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Follow Up By: Member - Boobook - Tuesday, Mar 28, 2017 at 19:43
Tuesday, Mar 28, 2017 at 19:43
I also tried it on my 80w flexible ones before adding the diodes.
When I had one in the shade and one in full sun, the current went up about 0.7A by disconnecting the shaded one. That's about 12w. I read that this heat is usually dissipated in one solar cell, the one with the lowest voltage in the panel. I didn't want to take the chance of blowing a solar panel while away.
Although the diodes introduce a loss, this can easily be compensated by a few dollars more on panels.
Each to their own, but every reasonably respectable solar site seems to advise it.
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Follow Up By: HKB Electronics - Wednesday, Mar 29, 2017 at 12:43
Wednesday, Mar 29, 2017 at 12:43
Maybe depends on the quality of the panel, can't see why one cell would dissipate all the heat as all cells in the string would have the same current flowing through them and similar voltage drops across them so they should all be dissipating similar power levels, even at 12W over say 36 cells that's 333mW per cell, can't see that doing any damage?
I would have thought if it was a big problem as the manufactures usually include bypass diodes they would also include blocking.
I have been using multiple panels in parallel for years without blocking diodes, if where camped under trees etc I put one out in the morning sun and position the others so they will pickup the sun as it moves through the day when where not there. Never had any issues or noticed any significant loss caused by the ones in the shade.
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