Solar panel regulators

Submitted: Friday, Feb 10, 2017 at 23:18
ThreadID: 134280 Views:3830 Replies:5 FollowUps:5
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Is it safe to charge your battery directly using the regulator supplied on the back of solar panels or is it necessary to go through a secondary charger, ie BCDC?
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Reply By: Allan B (Member, SunCoast) - Friday, Feb 10, 2017 at 23:45

Friday, Feb 10, 2017 at 23:45
Directly from the supplied regulator should be fine.

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Reply By: Peter_n_Margaret - Saturday, Feb 11, 2017 at 00:03

Saturday, Feb 11, 2017 at 00:03
Probably OK except the regulator supplied is likely to be very basic and therefore may not be ideal for your particular battery type and it won't be MPPT, so won't get the maximum harvest that is possible.
It is also better to have the regulator as close to the battery as possible.

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Reply By: Sigmund - Saturday, Feb 11, 2017 at 06:03

Saturday, Feb 11, 2017 at 06:03
Yes, safe but not that efficient probably. Bulk charge takes 14.6 v and more and a basic regulator (ie PWM) fixed to the panel doesn't deliver it IME so the battery never properly charges.

It's worth swapping to an MPPT regulator set close to the battery as Peter mentioned particularly if you're in cool to moderate climates. Victron do units with some charging smarts.
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Follow Up By: Gronk - Saturday, Feb 11, 2017 at 09:08

Saturday, Feb 11, 2017 at 09:08
My agm's recieve 14.4V from a Steca pwm controller mounted near the batts.
Depending on size and length of wiring, they CAN still recieve that from the controller mounted at the panel, but yes, nearer to the battery is best.
If you keep your batts fairly well topped up during camping, the advantage of a mppt is negated.
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Reply By: swampy - Saturday, Feb 11, 2017 at 11:25

Saturday, Feb 11, 2017 at 11:25
Regulating a solar panel output twice is counter productive
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Follow Up By: Enormous Racing - Saturday, Feb 11, 2017 at 19:06

Saturday, Feb 11, 2017 at 19:06
So would you remove the supplied regulator altogether & run straight to an MPPT charger?
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Follow Up By: Gronk - Saturday, Feb 11, 2017 at 20:00

Saturday, Feb 11, 2017 at 20:00
If the supplied regulator is per specs, remove it from the panel and use it nearer to the battery.
No need to spend money on a mppt controller if it's not needed !
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Follow Up By: Sigmund - Sunday, Feb 12, 2017 at 07:17

Sunday, Feb 12, 2017 at 07:17
At peak times I'd see around 13v at the battery from 150w of panels and a cheap PWM regulator stuck to the back of one. That rose to 14v with an MPPT job next to the battery (full sun, mild temps). The amp jump should be from something like 5.5 to something like 6.5 but I haven't measured it yet.

Whether it's worth it depends on what you have to replace and how long you've got to do it.
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Follow Up By: Gronk - Sunday, Feb 12, 2017 at 08:37

Sunday, Feb 12, 2017 at 08:37
There you go.....a cheap pwm ?
But you compared one at the panel to one at the battery.......
My steca pwm will output up to 14.4V at the battery and 13.8V on float. It will do the same at the panel, but the voltage you get at the battery will depend on size of wiring.
For a battery with around 80% or more charge in it, the mppt charger will have very little advantage, but if it's fairly flat, then that's when it comes into it's own.
But I always aim for fully charged batteries, so it's only rare times that I'd benefit from a mppt.
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Reply By: HKB Electronics - Monday, Feb 20, 2017 at 09:51

Monday, Feb 20, 2017 at 09:51
If your panels come with a good PWM regulator that's all you need to start with, just check the quality of the PWM controller though as there are some pretty cheap and nasty ones out there.

Both PWM and MPPT can provide the same charge voltages so nothing to gain really from that perspective, a MPPT is more efficient though in that it keeps the solar panel around its max power generation point for example:

PWM using 2 x 120W panels in parallel:

2 x 120W panels, ISC = 7.26A, IMP = 6.72A, VMP = 17.85V
Two panels in parallel (PWM), questimate 7Ax2 = 14A@12V=168W, 14A into battery

MPPT using same two panels in series:

Two panels in series (MPPT) = 6.72AX35.7V= 239.9W, I=P/E 239.9/12 = 19.99A@12V into the battery.

Above assumes no loses, please forgive any errors.

A good quality MPPT can supply more charge current when the battery volts are low, the gain decreases as battery volts rise, if your thinking of using a multi functional unit ie DCDC charger with solar input your not going to get the same efficiency as you would out of a high end MPPT unit.

Looking from a different perspective though you could probably buy three panels and a cheap PWM to give you 21A into the battery for less than the cost of the MPPT setup.

There can be other advantages of using a MPPT with series panels, ie smaller cable, more output under low light conditions, get the most out of what already installed etc, its all a balancing act.

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