Experiments with solar panels

[alanmalk]

Originally Posted by alanmalk

...
Awful hard to take a specific gravity from my SLA batteries.

And after many months of procrastination, the two SLA batteries are installed in parallel. They are Sears size 31, 100 AH each. (Now out of production.)

Here is a before photo - prior to strapping down for travel.

Since someone is bound to question hooking up batteries in parallel...
The theory says if they are identical in construction and electrical characteristics, then the "parasitic drain" of one battery charging another should be negligable.

I measured my drain at initial hookup at 165 milliamps, and after five days at 7 milliamps. (No charging during this time.) I can live with 7 milliamps of drain for a long time. And the standard 160/150 Watt solar installation can replace the loss with about 5 minutes of sunlight.

Battery maintenance - gone!

--
Alan

[jxoco]

Originally Posted by alanmalk

And after many months of procrastination, the two SLA batteries are installed in parallel. They are Sears size 31, 100 AH each. (Now out of production.)


--
Alan

Remember to set the solar controller to 'GEL' batteries or 'AGM' or what ever yours are, just take them off 'Flooded'.

Flooded and AGM are the same 14.4 volts but flooded equalizes (boils the acid a bit) every 28 days.
Gel uses 14.1 volts.

Is it the Go power 30 controller that you have?
if so hold down the 'B' button for about 8 seconds, the display will start to flash.
Then each time you press the B button again it will show '1' for flooded, '2' for AGM and then '3' for GEL, press the 'A' button to lock it in.


And the red wire with the fuse should go on the left battery, because the black ground appears to be on the right battery. And if you are going to be running an inverter with more than 150 watts, now would be a good time to upgrade the wire to a larger gauge. with 200amps on tap you can seriously overheat 10 gauge.

[alanmalk]

Originally Posted by jxoco

Remember to set the solar controller to 'GEL' batteries or 'AGM' or what ever yours are, just take them off 'Flooded'.

Flooded and AGM are the same 14.4 volts but flooded equalizes (boils the acid a bit) every 28 days.
Gel uses 14.1 volts.

Is it the Go power 30 controller that you have?
if so hold down the 'B' button for about 8 seconds, the display will start to flash.
Then each time you press the B button again it will show '1' for flooded, '2' for AGM and then '3' for GEL, press the 'A' button to lock it in.

That's good information - Thanks! And highlights the fact that I should have read the Go Power instruction manual. These particular AGM batteries do not recommend an equalize cycle.

Originally Posted by jxoco

And the red wire with the fuse should go on the left battery, because the black ground appears to be on the right battery. And if you are going to be running an inverter with more than 150 watts, now would be a good time to upgrade the wire to a larger gauge. with 200amps on tap you can seriously overheat 10 gauge.

My setup has the two batteries in parallel, which for all practical purposes means there is no "left" or "right" battery anymore. The red wire with the main fuse could be connected to either positive terminal without changing any electrical characteristics.

No inverter permanently connected in my trailer (one is available but in that rare instance I will connect it directly to the battery with dedicated heavy, short wires.)

I have calculated an "average worst case" battery current drain - water pump, fans, furnace and many lights, on simultaneously, at around 15 amps. (That's the "taking a shower on a cold night" scenario.) I believe the existing wire to be sufficient. An "unlikely worst case" would be to add the 'fridge running on 12v which would double that - but I intend to avoid that scenario.

--
Alan

[jxoco]

Originally Posted by alanmalk

My setup has the two batteries in parallel, which for all practical purposes means there is no "left" or "right" battery anymore. The red wire with the main fuse could be connected to either positive terminal without changing any electrical characteristics.

No inverter permanently connected in my trailer

--
Alan

Battery purists like to have the wires to the batteries the same length so that during charging and discharging the slight difference in voltage is equalized or I guess negated.
So from the charging source or the discharge load each battery 'sees' the shortty jumper just once.
The left side battery will see the jumper in its negative line and the right side battery will see the jumper in its positive line.
Rather than one battery sees no jumpers and the other battery sees two jumpers.

I haven't found the need for anything larger than a 75 watt inverter that plugs into the 12 volt socket, to charge my electric razor and an old coleman camping lantern, so I'm with you on that front.

And your 'shore power' the brown box with the fuses on it has a charger as well, it is 14.4V so your AGM's are ok with it.

[gbaglo]

I'm convinced my $12.95 75 Watt inverter with my MacBook plugged into it is what sucked down my batteries one evening ( furnace also on for those three or four hours ).

[Greg A]

I don't user the trailer batteries when boondocking any longer to charge my devices, but use the external battery packs to recharge ipad, phones, etc. http://amzn.to/1M6ED56 You can top these up real quick over the week by just putting them on the usb charger on the car when running around touring.

They are also making these external battery packs(some include solar panels built in the top) that will recharge laptops as well, or you can get a laptop automobile charger with a 12V plug that will go straight into the cig lighter or a similar plug in the trailer and bypass a need for an inverter.

These external battery packs are awesome when not camping as well, and I find I'm using them all time now.

[alanmalk]

Originally Posted by jxoco

Battery purists like to have the wires to the batteries the same length so that during charging and discharging the slight difference in voltage is equalized or I guess negated.
So from the charging source or the discharge load each battery 'sees' the shortty jumper just once.

At the risk of alienating any forum readers that may still be following this...

At 20 degrees C, a 10 AWG wire has almost exactly .001 ohm resistance per foot.
At a nominal 10 Amps charge or discharge, and assuming my short jumpers are 6 inches each, then the voltage loss in my system is .01 volts from not "balancing" the jumpers.



--
Alan

[cpaharley2008]

Since your converter sees your batteries as "one" and they are both same age and type, I suggest you place the negative on battery A and the positive on Battery B feeds to the converter, that way it will be treated as one unit versus a single plus a slave.

[thoer]

Greg I have started doing that same thing. The prices of those backup batteries has really dropped lately. I picked up a 16000 mAh Li-ion on eBay for less than $15

[alanmalk]

Originally Posted by cpaharley2008

Since your converter sees your batteries as "one" and they are both same age and type, I suggest you place the negative on battery A and the positive on Battery B feeds to the converter, that way it will be treated as one unit versus a single plus a slave.

Next time I visit the trailer (in storage), I'll see if I can detect a voltage drop from A to B. And I'll check that at least one lead, either positive or negative, is long enough to reach the far battery.

--
Alan

[citabria90]

Ha! That's funny!

[ronkat]

My head is spinning with solar options and my wife says I cannot talk to her anymore about this subject. The rules are keep it simple and don't destroy our 21" escape to be delivered in April 2016. I ordered the 2 6volt batteries and inverter.

So the facts are, I have a portable 95 watt solar kit with PWM controller that I used with my previously owned RV with a single 12v battery, and would like the option of using the 95 with the Escape. I believe I can connect directly to the Escape battery, if no other solar equipment is involved. i have a special door ordered from ETI.

If I purchase an addition portable 130 watt solar kit with a PWM controller, can I connect both directly to the battery in full sun, and would partial shade on one panel affect how the controllers read and delivers power to the batteries?

If I purchase the installed ETI roof 150 watt panel and PWM controller, can I connect directly to the battery with my portable 95 panel with PWM and all will work well?

My complicated other option, is to have the two portable kits mentioned above and set them up to use both with their PWM controllers bypassed and use one MPPT controller inside the Escape?

I spoke with a solar rep from one of the solar companies and he said a MPPT controller was required if two portable units with PWM were used , and the PWM units needed to be bypassed if connected directly to the batteries. I am skeptical this this information is correct.

It appears choosing counter tops and dinette color option were not enough. Anyway thanks in advance for any help.

[float5]

ETI uses a Samlex controller. They will not install MPPT that I know. You could do that yourself?

[jxoco]

The simplest is to just connect all of the panels together, in parallel, at the input to the solar controller, the samlex or gopower or what ever one they have installed.
The panels just have to be the lower voltage, '12 volt' ones. the actual voltage of these are 12 to 20 or so volts, they are 36 cell panels not the 44 cell high voltage ones.
the controller can take 30 amps which is about 450 watts of panels and a safety margin.
MPPT is not required in 12 volt systems, save your money and instead get a trimetric meter and shunt to accurately measure the amps into and out of the batteries.
After reading a bit and living with your system you can add the trimetric controller to the system, down at the batteries.
There is quite a bit of information on the internet about this stuff.
I would reccommend you at least read 'Handy Bobs Blog'
https://handybobsolar.wordpress.com/
I have found everything in his blog very accurate.
I have found his criticisms well founded.

[tractors1]

I'd use the ETI setup for a bit and see if augmenting with more panels is really needed. Easy to overcomplicate things when your camping style may not really need all that solar.

[alanmalk]

Originally Posted by jxoco

The simplest is to just connect all of the panels together, in parallel, at the input to the solar controller, the samlex or gopower or what ever one they have installed.

I'll second what jxoco is saying...

Multiple panels play together nicely, even if one is shaded, as long as each one has an isolation diode (which is very likely installed already). And in the rare case where a diode is missing, they are a buck (1 USD) or so. I'm planning to do just that with my second panel.

Originally Posted by jxoco

MPPT is not required in 12 volt systems, save your money...

Yes, MPPT is nice on paper but the higher price can not be justified when the chosen panels are designed for 12 v. charging. (Aside: The innards of MPPT is a DC-DC converter that changes 24-36 volts down to 14 without loss. An ordinary voltage regulator would have to waste much of that power as heat. Nice technology but our trailer panels are typically 18-20 volts so there is really no advantage to MPPT.)

--
Alan

[Parker]

That's what we did last year while camping off the grid in the Keys for a month. We had to park in the shade, so I ordered a portable panel from Amazon and paralleled it into the existing controller. Worked great.

[alanmalk]

Originally Posted by Parker

That's what we did last year while camping off the grid in the Keys for a month. We had to park in the shade, so I ordered a portable panel from Amazon and paralleled it into the existing controller. Worked great.

My thinking exactly.

Our next trip - in a few weeks - will be to the Gore Canyon area of the Colorado River (aka "Pumphouse" ). I expect to get a couple of hours of low-angle sun at best. The portable (aim-able) panel will be much more efficient than the roof panel in this instance. I hope to have a working arrangement - it charges the batteries while I go fishing...

--
Alan

[ronkat]

Thanks everyone.

I think I can use all your comments and head down the right road with regards to solar. I always do my own mods, but when electricity is added I usually have the look of a deer in headlights.

I live in Las Vegas, Nevada, and spend a lot of time in southern Utan, Northern Nevada, Arizona and California, which all have considerable sunshine. I think I will start without the ETI roof mounted solar panel, try to park in the shade and augment with my 95 watt portable kit.

If I can't keep up, I can cut my usage or add another solar panel, and save my money by not buying the MPPT controller. I was disappointed that the solar expert, I called gave me incorrect information, but I have every confidence, the information received from all of you is 100% correct.

After I get used to my new Escape 21' maybe I can return the favor and answer some questions on this forum, but not electrical questions.

[alanmalk]

Originally Posted by ronkat

Thanks everyone.
...
but I have every confidence, the information received from all of you is 100% correct.

Be careful. There is an old saying that I just made up...
Answers are free, correct answers cost $$$.

Remember, I said "I hope to have a working arrangement...". I'll let you know in a couple of weeks if it really does work as planned.

--
Alan