Handy solar info for lead acid batteries

[hbski]

Handy Bob

[pianotuna]

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[BFL13]

You always need to read more than one book on any subject. It doesn't even work out to read three and believe that last one when the first two disagree! 🙂

[Salvo]

Not sure what you stated is dead wrong, but it for sure is wrong.

You should know better than that! pwm controllers need "big" cables for other reasons. High panel temperatures will lower PV voltage. Combine that with a sizable cable voltage drop and voltage at the controller can lower charge current.

pianotuna wrote:

His recommendation for HUGE cables with PWM controllers. Once you have cable that will carry the number of amps safely then there is no need to go larger.

[TechWriter]

hbski wrote:
I too find him cranky and opinionated, but he also provides some good info. He definitely has a bias for Bogart and Tristar, but admittedly says he has not tried many others and recommends what HE knows will work from experience.

Judging from his review of MideNite's Classic controller, this should be rephrased to he recommends what HE can get to work.

Handy B could not get his Classic working the way he wanted and gives some details about it on his blog.

For example, he had trouble with the controller's arc fault detection. Let me say that I have a Classic and on the advice of others, I just turned arc fault OFF. The Classic manual (page 45) recommends you do this if you're having problems like Handy B did.

About that Classic manual -- it stinks. Could not agree more with HB about this, but that's what Adobe Reader is for . . . searching for stuff instead of paging through a paper manual . . . which I think is exactly what HB did.

Anyway, I think this HB quote about the Classic (and Outback) controllers says it all: "I know there are many people who claim to love the things. Well, people who buy any expensive thing will brag about how smart they are."

Inferiority complex much?

Instead of HB's site, I recommend Jack Mayer's site -- www.jackdanmayer.com.

[pianotuna]

Hi Gale,

We owe you for your efforts on the spreadsheet. The least I can do is help promote it.

Doing solar without an energy audit may be unwise.

I know that on shore power I use about 20 kwh per day. That has led me to abandon going to a much bigger solar farm--so I'm back to using solar as an assist and for battery charging.

[N8GS]

pianotuna wrote:
Some of handy bob is dead wrong. I've included a much better less wordy and less opinionated link below.

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

If you use solar as a battery charger, one rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!
solar spreadsheet by N8GS

If you full time or use an inverter lots, then populate the entire unshaded area of the roof with panels. I'm considering replacing my awning with solar panels.

For a nice explanation of solar, try this link:
Golden rules of solar

Handy Bob's info was good when written but today the available parts are much different and the solar industry has matured.
For those wondering about what size wire to use please refer to my spreadsheet it has an extensive wire calculator page that includes voltage drop and how much energy is wasted in heating the wire.

Don - I'm glad to see that you are still recommending my spreadsheet.

[red31]

Huge?
2. WIRE SIZES: My complaints about wire size started out in 2000, when every solar guy on the planet thought #10 was big. Stop taking this to mean that bigger is always better. It is NOT. Learn about how wires are sized for the amps they carry (the amps your solar panels actually produce, not the rating of the controller or the wires) and voltage drop is directly proportional to the amps and the length of the wire. You might Google ampacity chart or wire sizing. When people brag to me that they ran #2 for one or two panels I just want to scream. That is pure and simple waste.

let's not forget the drop in peak voltage due to panel heating, starting with 17v poly Vmp! I note NOTC Vmp of 16 for a 17.7 Vmp panel. It does get hot in places.

[JiminDenver]

Mex

The only reason I would be that deep in a rain forest would be to take pictures of the native bugs. Solar can't do it all of the time but it wouldn't hurt the big bank to get off it's lazy plates and do something for once, generator too.

There are some nice bugs down your way though. 🙂

[dclark1946]

MEXICOWANDERER wrote:


For me? Solar?
Well I can always dream.
Image a house and rig in an environment like this...

That is close to what our camp sites look like in the Smokies.
That is why solar is only good for maintaining our battery at home in sunny TX.

Dick

[Joel_T]

grizzzman wrote:

pianotuna wrote:
I have read it cover to cover carefully.

Victron does a Peukert calculation. The one he recommends does not. My personal favorite would be a smartgauge, which is better than either of the above if the information presented is correct. I don't use an amp-hour counter. Now that I live in the AGM world I probably should acquire one.

Have you bothered to read Ralph Hiesey's reasons on why he dosen't use the Perkert calculation or the use of temp compensation? Also take a look at the price difference in the smart guage and the trimetric. How accurate do you wish to be? And at what cost? Just some food for thought.

http://www.bogartengineering.com/sites/default/files/docs/PeukertsComments.pdf

[JiminDenver]

That's one nice thing about the Lifelines. Take them up to absorb voltage until the acceptance rate drops to a certain point and they are done. I can run conditioning charges if the capacity is off somehow but I'm not doing it all the time for tiny increases and shorter life.

Cover the roof, fill the battery bank and live with it.

[time2roll]

I would sooner spend the money on more battery capacity or more solar that actually provide power vs a monitor.
When my battery is low my simple voltmeter indicates just fine.

[grizzzman]

pianotuna wrote:
I have read it cover to cover carefully.

Victron does a Peukert calculation. The one he recommends does not. My personal favorite would be a smartgauge, which is better than either of the above if the information presented is correct. I don't use an amp-hour counter. Now that I live in the AGM world I probably should acquire one.

Have you bothered to read Ralph Hiesey's reasons on why he dosen't use the Perkert calculation or the use of temp compensation? Also take a look at the price difference in the smart guage and the trimetric. How accurate do you wish to be? And at what cost? Just some food for thought.

[grizzzman]

hbski wrote:

pianotuna wrote:
Hi,

His bias against all charge controllers except for Morningstar. There are other reliable units. Outback makes quite wonderful stuff. And there are some Chinese knock offs that are essentially identical to the Morningstar MPPT units at 1/4 the price.

I've not read that blog cover to cover, but I have read a lot of it and never seen him bash anything other than the Midnite stuff he's personally had problems with. Also he has actually said on the blog not to ask him about controller X or Y because he can't evaluate without having used one.

pianotuna wrote:
His bias that the trimetric is the 'only' amp hour counter that is perfect. Victron makes one that is cheaper and better.

I can't comment on which one of you is more accurate on this since I've not used either one, but I can say that obviously you are biased to your choice as well.

pianotuna wrote:
His recommendation for HUGE cables with PWM controllers. Once you have cable that will carry the number of amps safely then there is no need to go larger. MPPT is a different matter and size is important

Working with small voltage differences 1 to 3 volts difference from battery voltage to charge voltage will rob you of a lot of potential power at small voltage losses since the losses are based on the line voltage.....on his charging puzzle page he indicates 3% drop or less from the roof......that doesn't equate to "HUGE" cables.


I too find him cranky and opinionated, but he also provides some good info. He definitely has a bias for Bogart and Tristar, but admittedly says he has not tried many others and recommends what HE knows will work from experience. He also alludes here and there about his frustration with folks asking him to evaluate this or that and asking questions without reading what he has already posted......generally understandable positions.

What I got out of it was some good info and perspective. I personally don't subscribe to all of his opinions and bias, but it was a good read all the same and I found nothing that was listed as fact that was "dead wrong"

Well said. I agree 100%

[pianotuna]

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