few questions about solar power....

corporal_Canada said:

okay yes yes THAT is the 12,000 peso battery, i didnt realize that it is LFP...and i dont need a charge controller for this ? just jam all the pos and negative of all the all 3 solar panels into the mppt and im good ? no fire no eveil voodoo man knocking at my door.. and of course i wont forget the fuse...
will post a video of my setup as soon as i stop being naked... ...the cable used to extend the reach of only 1 solar panel is regular appliance cable.. because it sais 300 or 400 watts but would almost never produce anything above 200watts.......it is the same thickness as a cable going to my hot water kettle...
i hope that isnt too concerning...

i just want this to power a UPS that i ONLY have a pc/monitor/modem and refridgerator connected to, as long as possible or ONLY during daylight hours....

and i tested the pc wattage... 100 to 111.. monitor 27.. fridge sat at 65 watts, did not see any surge whatsoever

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Hedges said:

You most certainly need a charge controller.
Battery should already have a BMS, as last line of defense against over- and under-charge. But SCC must charge to correct voltage then stop, or drop to a float voltage.

For Lithium even more than lead-acid, there is a problem if SCC FETs fail shorted. That will apply PV voltage directly to battery. Voc is too high for BMS to block, so BMS FETs will fail too. Battery will over-charge and vent smelly toxic flammable gas.

Most people just use whatever SCC an don't worry or even know about it.
Some SCC are AC coupled (HF transformer), so if FETs fail they put out zero instead of Voc. I know of one or two expensive ones. Don't have a good idea of what cheap ones do.
One of my more expensive SCC has a relay output that says, "Save ourselves, for I have failed!" It is recommended we use that to disconnect array before battery is ruined.

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corporal_Canada said:

...and if you see a nude french Canadian in any reflection..

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Hedges said:

You most certainly need a charge controller.
Battery should already have a BMS, as last line of defense against over- and under-charge. But SCC must charge to correct voltage then stop, or drop to a float voltage.

For Lithium even more than lead-acid, there is a problem if SCC FETs fail shorted. That will apply PV voltage directly to battery. Voc is too high for BMS to block, so BMS FETs will fail too. Battery will over-charge and vent smelly toxic flammable gas.

Most people just use whatever SCC an don't worry or even know about it.
Some SCC are AC coupled (HF transformer), so if FETs fail they put out zero instead of Voc. I know of one or two expensive ones. Don't have a good idea of what cheap ones do.
One of my more expensive SCC has a relay output that says, "Save ourselves, for I have failed!" It is recommended we use that to disconnect array before battery is ruined.

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robbob2112 said:

He has a PWM, but a cheap one once he posts pics of it we know more. From the video he took it looks like the panels are either 30 or 60 watts


If his panels are really that small they won't run a laptop

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ohmboy said:

Where?

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robbob2112 said:

The inverter should connect across the battery. The charge controller should connect across the battery. The fuse and wire to the positive post is as close as you can come. Ordinarily I would recommend a MRBF and holder directly to the post but I couldn't find one on the website.

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robbob2112 said:

The cable from the roof is probably to small if the panels were actually what the labels say. Way to small.

Pictures of everything before you buy anything at this point.

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robbob2112 said:

The cable from the roof is probably to small if the panels were actually what the labels say. Way to small.

Pictures of everything before you buy anything at this point.

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corporal_Canada said:

havent purchased anything apart from the bms that wont be used since the battery you linked CLAIMS to have a built in BMS, but living here since april 2023 has driven me to be skeptical about anything coming from china...

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corporal_Canada said:

sooo 3 solar panels > charge controller > mppt > lfp battery ?
and please no need to use so many acronyms.. i feel dumb enough as it is

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robbob2112 said:

Ok, pictures and diminsuions of your panels please. Try for good pics that fill the frame on the camera. Must be clear so we can see the cells in it to identify what they appear to be.

Measure the voltage with them disconnected, preferably one at a time if you can do it without embracing the roof so passionately that it makes your girlfriend jealous.

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Hedges said:

No need for both "charge controller" and "mppt"; those refer to the same thing.

MPPT (Maximum Power Point Tracking) is a function of, and circuitry in, a charge controller. So long as the charge controller is actually MPPT, not PWM (Pulse Width Modulation).

(Don't be fooled by cheap lightweight SCC with the letters "MPPT" printed on it. It will be more expensive and heavier.)

Most AIO (All In One) inverters include PV inputs and have MPPT SCC built in.

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corporal_Canada said:

there is only 1 girl in my life and that is my 11 yr old daughter that lives on an island nearby....... but if weather permits i will try going on the roof tomorow before noon,

PS: quick question, would it be so bad if i buy 4 rectangular cells of 3.2v ? and use i dunno 3 or 4 bus bars to link all the studs ? as long as i use a bms, i should be safe no ? and before you say "i quit" again.. this method will only run me 4000-5000 allowing me to repeat the process again... and have ANOTHER 4 cells making another 12v battery.... instead of 12,500 on a store bought batt as you put, i need to learn to do this eventually, why not do it now and rip it off like a bandaid ? with all your help here, i can take steps NOT to recreate the halifax explosion that led to the atomic bomb.... strictly hypothetically, i understand most of the fundamentals of DC, Can you really give me a reason NOT to try this.. and there is no need to say "huge ass fire" as an example

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corporal_Canada said:

so ton confirm...
solar panels (all 3) > 1 mppt > bms > lfp battery..... >inverter...... (holding breath)

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robbob2112 said:

Building custom batteries is an art all unto itself. There are way to many ways to go wrong with it that end in flames. From all of your posts and pictures in other threads you aren't there yet.

If there a solar or camping or RV store in your nearest large town? If so can you go there and physically look at the batteries prior to buying one?

The battery I linked will weigh about 1/2 the SLA battery you were using before. So if you handle one that appears to be that same weight but says it is LFP you KNOW it is falsely marked.

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