under $250 solar system for emergency power

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Matt Gruber
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under $250 solar system for emergency power

Post by Matt Gruber » Jul 07, 2017 2:22 pm

Hi guys
UPDATE: two 100 w panels for $199 shipped. 150 watts in actual use. and $5.11 MPP solar controller. have inverter and sla's. So the successful set-up only cost me $204 and i ended up using the 2 LA's in my 2 cars during hurricane Irma, since they can do hundreds of shallow cycles, without damage. I don't need deep cycle for emergency power. Everything is off at night, except maybe my 4" fan at my bed, and that is 1-2 watts. Was able to cook a burger on my hotplate using my ebike pack. Ice lased for 4 days so next time i'll make twice as much ice ahead of time. I plan to get one of those $99 freezers on black friday as they are said to use less power, 65-85 watts. The key to my success is having low power appliances so i don't need lots of power to run them. My HDTV is 20 watts, for example. The old freezer is 120 watts.
Last edited by Matt Gruber on Sep 24, 2017 9:01 am, edited 5 times in total.

billvon
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Re: battery in parallel with solar panel?

Post by billvon » Jul 07, 2017 2:37 pm

Matt Gruber wrote:Hi guys
i'm thinking of a low buck emergency solar to run a chest freezer after a hurricane.
i have a free UPS- has 24v inverter 750 watt, 1250 peak. dead SLA's.
so i'm thinking 3-6p 150-300 watt panels 27v under load, 36v no load into a 15-20amp buck converter($11) set to 28.8v
what happens if i hook my 7s2p 28v makita/sony pack in parallel?
i'm hoping if a cloud cuts output, the lithium-ion's will keep the freezer running a few minutes hopefully the sky clears before it runs down. and the cells will charge up w/good sun.
Not looking for a big pack like a powerwall, just want to run freezer when the sun is out. Not sure if clouds will kill all output? I have no experience with solar. Thanks.
Cheers!
Buck converters don't work well due to uncontrolled input impedance. Use either a PWM (bang-bang) charge controller or a cheap MPPT charge controller.
--bill von

Matt Gruber
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Re: battery in parallel with solar panel?

Post by Matt Gruber » Jul 07, 2017 2:54 pm

Hi bill,
i also was thinking of not using a buck cv, but put a dummy load on the solar to keep it under 30 v.
would a dummy load help the buck cv too? what will it do otherwise, fail to start up?
Thanks!
PS-any links to low cost items you recommend?

billvon
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Re: battery in parallel with solar panel?

Post by billvon » Jul 07, 2017 3:03 pm

Matt Gruber wrote:Hi bill, i also was thinking of not using a buck cv, but put a dummy load on the solar to keep it under 30 v.
You can do that but that's hard to get very accurate. I'd just use something designed for charging.

Wal-mart has a $15 PWM controller called the Moohoo.
--bill von

Matt Gruber
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Re: battery in parallel with solar panel?

Post by Matt Gruber » Jul 07, 2017 3:10 pm

found this,
https://www.walmart.com/ip/30A-12V-24V- ... /202476643
EDIT: crappy product! good for spare only
Last edited by Matt Gruber on Sep 24, 2017 9:02 am, edited 1 time in total.

billvon
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Re: battery in parallel with solar panel?

Post by billvon » Jul 07, 2017 3:19 pm

That should work. The output voltage will be around 27 volts but that should probably be good enough to not damage your batteries.
--bill von

Matt Gruber
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Re: battery in parallel with solar panel?

Post by Matt Gruber » Jul 07, 2017 3:22 pm

delete
Last edited by Matt Gruber on Sep 24, 2017 9:03 am, edited 1 time in total.

Matt Gruber
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Re: battery in parallel with solar panel?

Post by Matt Gruber » Jul 08, 2017 1:54 pm

so i used the 115v 1000w burner the emergency power plan.
it can run off ebike packs.
Last edited by Matt Gruber on Sep 24, 2017 9:04 am, edited 1 time in total.

Matt Gruber
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Re: low cost solar for emergency

Post by Matt Gruber » Jul 09, 2017 10:02 am

tested WATTS - UPS has wattmeter:
5000btu ac 384 watts on startup, 520 after 15 minutes at 123v, should be 486 at 115v the UPS v.
chain saw 600w
chest freezer in garage 111w
bench drill press 138w
stereo 7w
ebike charger 94w
20" box fan 60, 80, 100w
decided not to run fridge in house, creates too much heat. will make ice in garage and bring in ice for ice chest. keep only fresh food in house.
plan to have 1 panel(235w) in gar for freezer on 350w inverter w/12v SLA.
3 or 4 panels in front of house w/750w UPS for ac etc.
each gets a charge controller. found another for only $10.82

Matt Gruber
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Re: under $300 solar system for emergency power

Post by Matt Gruber » Jul 13, 2017 6:32 am

i like the alte store also, great videos, but high ship costs on a small order. great for a full off grid system.
Last edited by Matt Gruber on Sep 24, 2017 9:06 am, edited 2 times in total.

Matt Gruber
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Re: under $300 solar system for emergency power

Post by Matt Gruber » Jul 20, 2017 10:18 am

i opened the controller and there were no heat sinks attached to the 3 ??? MOS with no numbers :roll: SCAM?? was my 1st thought.
has CD40106BM IC "inverter MOS hex schmidtt triggers" i don't know what that means :lol: but
it sounded legit to me.
So i installed a large heavy heat sink and insulated mount kit from an old ebike. my theory is they cut costs to save $ and ship weight from china. so maybe it can now work, without quickly overheating.
saw a similar one on utube, and a guy added 60a MOS and big heat sinks and said it worked good.
my test is going to have 75' of awg14 going from the 24v PV to the controller, battery, and inverter. that will lose 2 volts at 5a. :oops:
.
also found a guy designing an impedance matching circuit for BUCK BOOST instead of a solar controller
https://www.youtube.com/watch?v=GzCDDCmOlPA#t=521.941

Matt Gruber
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Re: under $300 solar system for emergency power

Post by Matt Gruber » Jul 20, 2017 5:17 pm

so, due to the dubious power capability of this pwm controller, i think it is too risky to put the inverter on the LOAD.
start of the freezer will pull 15-30 amps, and i expect the no number MOS could blow :evil:
i've read many times that the v at the battery and the load are often equal, reduced by pwm to the proper range, so i don't see why they need to be separate.
so by keeping the sla's hooked to the inverter, the hi start up amps do not travel thru this controller, and the MOS see only amps from the solar panels, 5.5a max, as it tries to maintain charge on the sla's.
.
if anyone sees a flaw in this, let me know by 9 am 7-21.
thanks
matt

Matt Gruber
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Re: under $300 solar system for emergency power

Post by Matt Gruber » Jul 21, 2017 8:26 am

Hooked up for test! made only 1 attempt to point PV's toward sun.
Data says early morning sun good for about half power.
tried the freezer at 9:10am UPS says 133 watts.
input 26v at 4 amps so only 104w coming in. slow discharge of sla's. need more sun power! disconnect 9:14
will update this post as the world turns :)
9:50
hazy sun cuts to 1.85a :(
moved pv's were leaning against house,
now on driveway. i have not :oops: made an adjustable frame, so i put them on boxes. 15" box
on one end. will not try freezer again until better sun. in FL the weather can change in 15 minutes. thanks for reading!
.
so i have to have a plan B. since i have 2 antique cars, rarely used, i should take advantage of their LA's. each has 95 minutes of reserve capacity(25 amps) LA's don't like deep DOD, but charts say 20-25% DOD is no problem. so i need to make up a wire to connect them for 24v, then on hazy or partly cloudy days, i could run the freezer for 60-90 minutes early am, then let the PV recharge them. rinse. repeat.
i also plan to get that $99 freezer at HD which is said to use only 65-90 watts.
Last edited by Matt Gruber on Jul 23, 2017 2:26 pm, edited 1 time in total.

Matt Gruber
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Re: under $300 solar system for emergency power

Post by Matt Gruber » Jul 21, 2017 1:54 pm

sky clear 1:40
best amps 4.6 UPS says 135w sla 25.2v held until 2:30 when roof started to block sun, 6" on one panel 2.9a
plugged ups into vac, watts only 109, so cheap inverter costing 26w :shock:
moved pv to sun, now 132w 2:35pm
freezer cold! will run 'til shade or LVC. 4.43a at 26.2 into controller
this is a fun experiment!
have a lot to think about, very close to break even. sla's hold at 12.6v each
have analog meters $1.43 on order for each panel. should be better able to position them as i go for max volts rather than guess.
.
test ended 3pm THUNDER no sun :lol: such is FL
sla's charging 0.6 amp pv 125F
3:24
drizzle chg only.16a so i disconnected pv
UPDATE: switched to MPP https://endless-sphere.com/forums/viewt ... 41&t=89895

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spinningmagnets
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Re: under $250 solar system for emergency power

Post by spinningmagnets » Dec 12, 2017 1:34 am

Thanks for posting this. I lived for years in the earthquake zone of southern California, I lost power for a few days in the brushfire zone of southwest Utah, and now I live in tornado alley, central USA, Kansas. I have pondered affordable basic systems.

Once someone wants to build an off-grid system to supply all their needs, I'd go straight to 48V and make the size of the battery and solar panel array expandable...by that I mean...the solar charge controller and inverter should be good-quality units and large enough to satisfy your needs in the future. In the meantime, you can size the battery pack and solar panel array to the minimum necessary to meet only your basic needs, then expand over time.

I had at first wondered about a small 12V system, simply because the initial buy-in was the smallest possible for every component in the system. This still works for a lead-acid battery, and in a power outage where I felt I needed to drag out my solar panel to lay it in the protected back yard...I would first run to the store to buy two 12V deep-cycle batteries, hoping that they were not sold out.

I could round up several car starter batteries to use for a few days, but...they have thin plates to provide the max cold-cranking-amps possible for starting the engine on a cold morning. It would work, but if I needed to deep-cycle them, they would be worthless in a couple weeks. I wondered about buying a couple deep-cycle lead-acids and then running a long-term storage protocol I read about, but I am skeptical (fully charge, drain electrolyte and store the electrolyte, double-rinse the battery plates with distilled water, dry and store the battery. Re-fill with electrolyte when needed to use).

I wanted to try some way to leverage my recently acquired knowledge about lithium 18650's, but...when looking at the charge controllers and inverters, I was torn between 3S and 4S. Each having its benefits and drawbacks. Since then...I have fallen in love with 7S and 24V for a small system.

Nothing wrong with going straight to 48V (I have three 14S ebike battery packs that I can charge at work, to run a 48V inverter to power my TV). That being said...my 24V research has led me to used 24V UPS's (Un-interruptible Power Supplies). My work computer has a 12V UPS with a small SLA in it. During a power outage, in theory...it would continue to power the computer until the battery drained.

UPS's exist in 24V, and when the SLA inside wears out, sometimes the company simply upgrades them to a bigger and better model, rather than swap-in a new SLA (since the UPS companies often charge as much for the service call to replace the two 12V SLA's as it would cost to simply buy a new UPS). This means that....regardless of the reason...there are used 12V and 24V UPS's available at very reasonable prices. The 24V units seem to take 7S lithium very well, so these are ripe for anyone to snag a few and perform a lithium 18650 upgrade on the guts.

An MPPT solar charge controller can take-in a wide range of input voltages from a solar panel array. A 7S 24V system can be fed from panels that output anywhere from 28V-40V.

I wouldn't try to run a refrigerator off of a small system such as the type I am describing here, but...for a laptop, your smart-phone, and a few 18650 flashlights?...I think this could prove to be a smart move. Here's a 24-min youtube of what I mean:

https://www.youtube.com/watch?v=OtBI_Dr2cII

Matt Gruber
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Re: under $250 solar system for emergency power

Post by Matt Gruber » Dec 13, 2017 11:46 am

only my freezer needs ac.
tv, fan, pc, burner, radio. lights. all run on dc.
.
my emergency power should not be confused with an off-grid system. i'm 100% on grid, except for an emergency.
.
i wanted to use my 18650's BUT they are in 2p5s packs. was easier to hook 2 car LA's. their purpose is to smooth out power dips from clouds and i would run the freezer for an hour, knowing the sun will be coming up soon. No deep cycles allowed.
.

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