More Solar for "Us"

[MrWizard]

Ok, I went off.the deep end?
Bought 3 used 37watt uni-solar panels and a blue sky 2000e controller for the hefty price of $400,
They were being listed as 75w panels, they are not

The tested open circuit voltage was 21+, short circuit amps 2.9
I tested each panel multiple times tilted into the sun and laying flat on the ground , got the same readings each way, that was the deciding factor, they appear to put out full power while laying flat, I will try to mount them tomorrow before it gets hot, right now 104°F
I will use the existing wiring until I buy & install the new wire

[MrWizard]

CA Traveler wrote:
BTW Wiz what I interpret from you posts is that your batteries are never fully charged by your solar so no apparent down side to maintaining the voltage.

But for reference your situation is not typical. ie For a discharged battery use bulk charging voltage and when the batteries reach the bulk end stage they start reducing amps while the controller maintains the bulk/absorb voltage. Then when the amps reach the float level the voltage is reduced.

So what I get from your posts is a very unique situation which should not necessarily be a guide for others.

BINGO.. give the man a beer

i've over 600w of Solar, but this time year doesn't come even close too supplying daytime use AND recharge from overnight use

in summer it supplies more and comes closer

everything i've done with the solar and batteries, is document in this thread

just reading the part about the controller change then criticizing the operation of the system, and the care of the batteries

is just guessing, with out knowing the facts of daily operation

i never suggested what i was doing is for everybody

if i had 3000w of solar and an OFF grid stick house battery bank of several thousand amphrs, things would be different

the pictures of my control settings,
were too show, what can be done, what can be changed, what i have changed

not a proposal of what somebody else should do

and depending on which 'battery guru' you wish to follow

AGM batteries are fully charged when they reach less than 1 amp per battery at 14.8v charge rate

or 0.5% charge rate at 14.8v

my bank of (5) batteries is 675 amp hours
that means full is some place between 5amps at 14.8 and 3.75amps at 14.8

pretty narrow range huh?
they aren't full, when taking 4 amps at 14.2 or floating 13.2 because vtab reach 14.4 and shut off
most days the solar output drops off before reaching that point
'No reason' for premature float stage based on 60 minute timer turning off boost
strange i changed those setting over 3 months ago and put up pictures
and just got all these postings in the last few days

the controller data says operation 111 days
it did take me a little while to settle on those settings
but a few more days will be 4 months of operation

[BFL13]

You guys are not getting that Mr Wizard has a 120v fridge on inverter all day, plus other loads. He needs all the daytime he can get at 14.x to keep the batts up or from going down too fast after they get up, while there is still some sunshine.

The batts are not full when they reach Vabs--they need a long time at Vabs, even longer if that drops to 13.6. Even more difficult if there are loads stealing what could be going to battery

You are talking as though you just have to get the batts up before dark and it all should be so simple.

I have the same sort of thing in the summer when we are on solar for weeks at a time. Some days you want a shorter Vabs time if the batts are bubbling too much, and other days you can't get enough with all the clouds. You have to pay attention every day what is going on with the batteries and how to play the solar settings. It only takes a few minutes of the day but you have to do that few minutes. No big deal. The Trimetric gets used too.

[Almot]

CA Traveler wrote:
So what I get from your {Mr Wiz} posts is a very unique situation

A lot of loads, not enough solar. Full-time living. People on a seasonal camp where I used to stay, were running genny 60-90 minutes every evening, like a ritual, after keeping batts on 200-300W solar all day. I would probably do this the other way around if I had to.

[CA_Traveler]

BTW Wiz what I interpret from you posts is that your batteries are never fully charged by your solar so no apparent down side to maintaining the voltage.

But for reference your situation is not typical. ie For a discharged battery use bulk charging voltage and when the batteries reach the bulk end stage they start reducing amps while the controller maintains the bulk/absorb voltage. Then when the amps reach the float level the voltage is reduced.

So what I get from your posts is a very unique situation which should not necessarily be a guide for others.

[Almot]

BFL13 wrote:
If the controller drops to Float voltage before you want it to, it is very frustrating trying to get it back to Bulk, since the batts have to get down to 13.2 (eg) which can take a long time.

Yes, it would have to go through Absorb again.
No, it won't take a long time if controller is smart enough to shorten the Abs stage accordingly to the current and/or voltage at the beginning of this "new" Abs stage. Those cost more than Grape though.

BFL13 wrote:
If you can program Float to be near the same higher voltage as Bulk, then you are good all day.

Why keeping batteries all day at elevated voltages is good?

BFL13 wrote:

If the controller is set to do two hours at Vabs after getting there, and it gets there before lunch, then you have a problem depending on the situation.

Vabs plus 2 hours = +95% SOC, this is early in the day yet. Scenario that most users would consider ideal. Then it would float without (hopefully) having to cycle through Vabs again due to high demand or low sun, and even if it would cycle again, a lower end controller would then do what Mr Wiz does (increasing total Vabs time), and a higher end models would quickly transit to Float and stay there. I don't see any possible problem here.

BFL13 wrote:
The MPPT controller has a buck converter in it to "make amps", which it still does even when not in Bulk (tracking active). A PWM controller does not have the buck converter and "makes amps" a different way. Apples and oranges.

PWM doesn't increase the amps, it gives as many amps as there are available at that time of the day. It cuts the voltage off to setpoint, instead. (I was wrong earlier saying that "any" controller would do this - PWM won't increase Amps output, it simply gives all it has as long as battery accepts it).
MPPT "makes" amps out of this cut-off voltage and uses those amps to maintain whatever stage the controller is on. I don't think this matters (much), or if it does, then you guys have not enough solar.

My apologies for multi-quoting. Profound essay deserves detailed comments, no? 🙂

[Almot]

CA Traveler wrote:

BTW Grape products are something I like to enjoy in the evening with a good dinner! :B

Italians have a hard booze called "grappa". A horrible moonshine, though could be a matter of taste 🙂

[CA_Traveler]

Like Almont my Morningstar MPPT60 with a charged battery kicks up the amps when house loads so dictate so no need or benefit for keeping the voltage up on charged batteries.

BTW Grape products are something I like to enjoy in the evening with a good dinner! :B

Just trying to inject a little humor.

[Almot]

MrWizard wrote:

Afaik this is true of all solar controllers, even the Grape 40
Granted as load is applied and amps increase voltage drops and there will be an increase in solar amps output
But the previous controller xantrex did not change anything

Correction: voltage doesn't always drop. It will drop when the incoming amps are not enough to keep it where you want it, and until this happens - due to higher loads or low sun - voltage won't drop.

Controller (any controller, IMO) would cut the excess solar amps off when battery or loads don't demand amps (subject to setpoints). And it would increase the amps when demand increases. Maybe you got a faulty Xantrex, because what you described doesn't sound normal to me.

[MrWizard]

Yes I raised the float voltage, and I raised the voltage point at which the controller goes back to boost
This summer when and if needed I can change my settings
Using a shorter boost time, or lower voltages , " IF needed "

[BFL13]

If the controller drops to Float voltage before you want it to, it is very frustrating trying to get it back to Bulk, since the batts have to get down to 13.2 (eg) which can take a long time.

I used to run the inverter for a minute to knock down the voltage, but the batts soon got back to Vabs and then Float started. If you can program Float to be near the same higher voltage as Bulk, then you are good all day.

If the controller is set to do two hours at Vabs after getting there, and it gets there before lunch, then you have a problem depending on the situation. Mr Wizard has programmed that Vabs time to last longer, which is one way around it, if you cannot just make Float voltage the same as Vabs.

You get your break from being at Vabs "too long" when it gets dark.

BTW, some confusion in the previous posts. The MPPT controller has a buck converter in it to "make amps", which it still does even when not in Bulk (tracking active). A PWM controller does not have the buck converter and "makes amps" a different way. Apples and oranges.

[brulaz]

MrWizard wrote:
The xantrex C-30 dollar controller did not respond the way you are thinking
Once it dropped to float it stayed at float voltage output until battery voltage dropped then it would increase voltage
It does not increase amps to maintain float voltage
Afaik this is true of all solar controllers, even the Grape 40
Granted as load is applied and amps increase voltage drops and there will be an increase in solar amps output
But the previous controller xantrex did not change anything
This is simply a function of decreased battery voltage aka resistance allowing more amps flow
It is a set voltage maintained with no load drain, any amps is determine by battery acceptance
With a load it will at some point switch back to boost after a low voltage threshold switch point is reached
...

My Rogue MPPT works this way too. Once battery voltage drops to 0.5V below the float set point, it reverts to MPPT (boost) mode.

So when boondocking, not in storage, and actually using the batteries routinely, I increase the float set point to 13.6V from the usual 13.2V used in storage. So the controller goes into mppt once the battery V drops to 13.1V.

[MrWizard]

Yes the grape 40

You think I'm over charging my batteries because I'm keeping a longer boost and No float

But I'm not
I'm maintaining my batteries at top charge because they are constantly being cycled
A long float period in the middle of the day will do me more harm than the charging profile I'm using

[Almot]

Alright, C-30 has poor charging algorithm (or malfunctioned). Need a better controller.

[MrWizard]

The xantrex C-30 dollar controller did not respond the way you are thinking
Once it dropped to float it stayed at float voltage output until battery voltage dropped then it would increase voltage
It does not increase amps to maintain float voltage
Afaik this is true of all solar controllers, even the Grape 40
Granted as load is applied and amps increase voltage drops and there will be an increase in solar amps output
But the previous controller xantrex did not change anything
This is simply a function of decreased battery voltage aka resistance allowing more amps flow
It is a set voltage maintained with no load drain, any amps is determine by battery acceptance
With a load it will at some point switch back to boost after a low voltage threshold switch point is reached

it does not work like an LED light controller maintaining a constant
current setting

With the grape solar controller
I am able to set all those points and create my own charge profile
My batteries are Never at rest
As soon as charging stops they are in discharge use mode
If they are not being charged they are being discharged

I run the generator every morning
The solar Basically just covers day light use, running the fridge ,pc , lights , inverter etc..
So that my batteries have stayed charged without running the generator all day
From dusk till dawn I'm on battery power
There is NO storage mode float non use, unless the RV is in the shop

[Almot]

MrWizard wrote:

And response is better when the fridge is on or I use the inverter for MW etc..
By setting the higher voltage and the longer boost times plus the return to boost voltage
The controller doesn't wait for the voltage to drop low before returning to boost
This lessens the strain on the batteries

I thought that Float mode had the fastest response - controller current would increase immediately when loads come online, while still maintaining Float voltage. At least, this is the case with my MPPT.

That is, - if there is enough sun and enough panels. When there is not enough, I don't understand how higher voltage setting can help. My controller in this case would revert from Float to Boost/MPPT, and would bring the voltage up only as high as the available net current into battery would allow. It would attempt raising it to 14.6V setting if possible and then go into Float again.

If there is too much load and too little solar input, then the current out of the battery exceeds the current in way too much, and the voltage would drop no matter what. You can't give batteries more solar power when there is nothing to give.