Solar Controllers--Don't be a Sucker! :(
Just got to say it again, how it is we are sitting here for five months off grid on solar with no problems at all (third season on solar like this), using the non-programmable, non-MPPT, solar control...
Forum Discussion
Good points raised by all, despite my rant offending more or less everybody!
Timing. What I mean is that you have a lengthy period after noon where it is not doing its full amps because the battery acceptance rate is low at high SOC.
---So , eg, in the morning on solar that can do say 15 amps, all 15 goes to battery charging. If you watch a 10 amp TV then, net charging is 5 amps. If you wait till afternoon when charging is down to 5 amps, you can watch the TV for free, where the solar does the 10 amps and SOC is not affected. Later after solar is over, watch TV for 10 amps draw on the batts.
Your camping tactics do matter. If you only have that 5 amps instead of 15 in the morning, you can't speed things up later in the day to make up for it because now your low amp lengthy period that must follow that will be after dark-- too late-no amps at all.
---How much time is spent where amps are lower than panel potential because of high SOC? If your MPPT can do 12 amps vs a PWM's 10 amps and the batteries will only take 5, what good is that MPPT doing?
Cloudy days- solar is getting some amps but not as many as if sunny. 10% gain of not much is not much.
Charging Algorithms-- good point that not all PWMs have the same one and you can program some controllers to get a desired one for your self. But-- if the cheapo version gets you to 98.5% SOC anyway, you can't beat that. Trying to is called "Gilding the lily" if I have that expression right.
--Waiting for an example or three proving jimindenver's results are not typical. He claims 235w 24v and 20 amp MPPT gets 15amps max. Same as PWM would using Isc as max.
I am unclear on Mr Wiz's situation where his PWM controller drops to Float after four hours. Mine drops to Float after two hours of Absorption, but that is only after taking as long as it takes in Bulk to get to Vabs. How long that takes and SOC achieved when Vabs reached is a function of charging rate--charging amps wrt bank AH size.
Low rate means Vabs is reached with SOC percent in the 90s. Higher amps will just get you to Vabs sooner at a lower SOC and then you need more of an Absorption stage to do the rest. But it is all in the 90s, so who cares if you get to 95 instead of 97% ?
The weather is so variable that fine tuning the controller seems like a hopeless task?
So, all in all, except for ?rare? roof real estate issues (and what RV has a small roof but can carry a big battery bank that needs big solar?)- 12v and cheap PWM is perfect and you can't beat perfect.
Timing. What I mean is that you have a lengthy period after noon where it is not doing its full amps because the battery acceptance rate is low at high SOC.
---So , eg, in the morning on solar that can do say 15 amps, all 15 goes to battery charging. If you watch a 10 amp TV then, net charging is 5 amps. If you wait till afternoon when charging is down to 5 amps, you can watch the TV for free, where the solar does the 10 amps and SOC is not affected. Later after solar is over, watch TV for 10 amps draw on the batts.
Your camping tactics do matter. If you only have that 5 amps instead of 15 in the morning, you can't speed things up later in the day to make up for it because now your low amp lengthy period that must follow that will be after dark-- too late-no amps at all.
---How much time is spent where amps are lower than panel potential because of high SOC? If your MPPT can do 12 amps vs a PWM's 10 amps and the batteries will only take 5, what good is that MPPT doing?
Cloudy days- solar is getting some amps but not as many as if sunny. 10% gain of not much is not much.
Charging Algorithms-- good point that not all PWMs have the same one and you can program some controllers to get a desired one for your self. But-- if the cheapo version gets you to 98.5% SOC anyway, you can't beat that. Trying to is called "Gilding the lily" if I have that expression right.
--Waiting for an example or three proving jimindenver's results are not typical. He claims 235w 24v and 20 amp MPPT gets 15amps max. Same as PWM would using Isc as max.
I am unclear on Mr Wiz's situation where his PWM controller drops to Float after four hours. Mine drops to Float after two hours of Absorption, but that is only after taking as long as it takes in Bulk to get to Vabs. How long that takes and SOC achieved when Vabs reached is a function of charging rate--charging amps wrt bank AH size.
Low rate means Vabs is reached with SOC percent in the 90s. Higher amps will just get you to Vabs sooner at a lower SOC and then you need more of an Absorption stage to do the rest. But it is all in the 90s, so who cares if you get to 95 instead of 97% ?
The weather is so variable that fine tuning the controller seems like a hopeless task?
So, all in all, except for ?rare? roof real estate issues (and what RV has a small roof but can carry a big battery bank that needs big solar?)- 12v and cheap PWM is perfect and you can't beat perfect.
