Renogy kit

brownbear

Hello, I finally got around to setting up a solar kit that includes one 100 watt panel, mppt 20amp,   mt-50, 1,000 watt inverter, and 125 amp hour battery. I live in Los Angeles and get around 9 hours of sunlight hitting my panel. In the morning the mppt shows a slow charge and then again when the sun is not shining directly on to the panel around 4-5PM.  My concern is to not drain my battery more than 50%. The only thing that I am charging right now is my cell phone for 3-4 hours per day, small battery bank for 5 hours, portable speaker for 2 hours,  internet modem for 6 hours, internet router for 6 hours, and roku for 2-3 hours per day.  If I have a fully charged battery will it dip below 50% with my consumption?  Should I get another panel or an extra battery?  

brownbear

mike95490

Disconnect the inverter and get a car cigar lighter socket to plug your 12V phone charger into.  The battery will take a week to get low.

The inverter is way too large, and it consumes 10x the power needed to charge the phone

As for all the other stuff, read the wattage requirement off the gear,  10w here, 20w there, you are getting close to over 100w of loads, and you only have 100w of panel.  

You merely need a small, quality,  250w inverter, pure sine wave, and that will happily run your gear.    You need to total the loads up, and see how many watt hours your will consume in a typical day.     

20w of router for 6 hours = 20 x 6 = 120wh

35w of Roku 3 hr = 105wh

20w of modem for 6 hr = 120wh     You are up to 345wh consumed, and while the sun is in the sky for 9 hours it's only got 5 effective hours.   a PV panel generally produces 70% of nameplate, so you are looking at harvesting  70w x 5h = 350wh.   And there are no other losses accounted for, so I can say for sure, you need at least 1 more panel.

a 12V 125ah battery contains 1500wh , so the battery size is fine, you just need a small, efficient inverter, and more panel.

mcgivor

The actual hours of usable sunlight is actually less than the 9 hours, as you've discovered, the weak morning and late afternoon sun provide little in the way of charging. To comment the loads without details its is not possible to estimate with any accuracy,, if you can provide this information including the inverter self consumption that would be extremely helpful. Are the loads all powered by AC to DC adapters, if so using DC to DC adapters would be more efficient than using an inverter , especially an oversized one 1000w is too large for the battery capacity and small loads. The 100W panel can at best produce 75W so using a more realistic sun hours figure of 4.5 hours, this amounts to 337 Wh, the inverter would conume around 100Wh over 6 hours  (estimate ) this leaves 237Wh to cover loads and charge the battery, not even factoring in efficiency losses. 

littleharbor2

Seems strange to me that Renogy would put together a "kit" that has only a single 12 volt panel and an MPPT charge controller.  The very first thing I would do, aside from getting the previously mentioned smaller inverter, would be to add at least one more 12 volt, 100 watt solar panel, wired in series. MPPT controllers are designed to take higher voltage input and step it down to your battery's voltage. Your controller has a max Voc. of 150 volts

Estragon

+1 on adding panel(s).  A single panel might put out ~4a in full sun.  A 50% depleted battery would have a ~60amp-hour deficit, which would take would take several days to charge (or longer if running loads as well).  Might work if it's just for weekend use and has all week to recharge, but otherwise definitely needs panels before adding more storage.

jmb

Get another RNG100D panel (or whatever the kit came with) and wire them in series (if the CC can handle it) and your MPPT controller will be more happier.

I had 4 RNG100D panels wired in parallel into an MPPT controller and got about 200 watts of charge.  After hooking 2p2s I was sometimes getting right at 400 watts of charge at mid day.  Just upping the voltage into the CC doubled my charge rate to the batteries.

brownbear

Hello again. Thanks for all the information. I still have a few more questions. My goal is to power my 65inch tv along with the modem, router, roku, charge my phone, power bank, speaker, and maybe a 2nd phone. Here is a list of how much energy they use. I plan on buying a second 100 watt panel. Should I get a total of 3 100watt solar panels? I jave the 20amp charge controller commander. Right now I have a 125ah battery.  Should I get a bigger battery? Any suggestions? Finally is it ok if I just buy the extra 100watt solar panel and keep using the 1000 watt inverter? Or is it beneficial to get maybe a 500watt inverter will I really save that much energy?
On idle the 1000 watt inverter draws 10.6 watts. My TV says typical power 91watts. Roku says 12v 1A. Router says 5V ==0.7A. Modem says 115V-0.6A. My cell phone holds 6400mAh, speaker battery 3400mAh, small battery bank I've included a picture. 
By the way the inverter has 1 5V USB port and that's what I use to charge my phone. If that makes a difference from not having a cigarette port.

brownbear

BB.

Ideally, you should get a Kill-a-Watt type meter (for measuring 120 VAC power) and/or a Doc Wattson type meter (for DC power). Here are a couple of examples:

https://www.solar-electric.com/kiacpomome.html
https://www.rc-electronics-usa.com/ammeters/r102-amp-hour-specs.html

For solar/off grid power, you really need to accuratetly measure your energy usage... The following is an example of what it could look like (estimated energy usage--But close enough to give you an idea of how the math works out):

• 120 Watt TV (65 inch) * 6 hours watching = 720 Watt*Hours per day
• 12 volts * 1 amp Roku * 1/0.85 DC to AC converter * 6 hours per day = 85 WH per day
• 5 volts * 0.7 amps router * 24 hours per day * 1/0.85 DC to AC conv = 84 WH per day
• 7 Watts * 2 hours per day phone 1 = 14 WH per day
• 7 Watts * 2 hours per day USB Speaker charging = 14 WH per day
• 10.6 Watts * 24 hours per day AC inverter "tare losses" = 254 WH per day
• Total WH (at 120 VAC) = 1,171 WH per day total

Now, battery sizing. Nominally, suggest 2 days of storage and 50% maximum discharge for daily usage:

• 1,171 WH per day * 1/0.85 AC inverter eff * 1/12 volt battery bank * 2 days storage * 1/0.50 discharge for longer battery life = 459 AH @ 12 volt battery bank

That is, roughly 2x 6 volt @ 220 AH golf cart batteries in series * 2 parallel strings for 12 volts @ 440 AH battery bank

Now to charge that battery bank, if you are using power during weekends/non-winter time you can use 5% rate of charge for the battery bank. For full time off grid into winter, then a 10% to 13% rate of charge is a better idea:

• 440 AH * 14.5 volts charging * 1/0.77 solar panels+controller deratings * 0.10 rate of charge = 829 Watt array minimum

And you also need to take into account how many hours of sun per day you have... For a fixed array:
http://www.solarelectricityhandbook.com/solar-irradiance.html

Bellevue Washington State
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 42° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
1.70	2.81	3.54	4.17	4.57	4.78
Jul	Aug	Sep	Oct	Nov	Dec
5.23	5.21	4.71	3.15	1.97	1.53

Say you need a genset/don't watch much TV during winter and toss the bottom three months, that gives you 2.81 hours of sun per day for February as the "break even month":

• 1,171 WH per day * 1/0.52 end to end off grid AC system eff * 1/2.81 hour of sun per day = 789 Watt array minimum (Feb break even)

Now, realistically, you can use around 50% to 65% of your daily production (on average--Some days you will have more sun, other days less)... So, if you needed 1.171 WH per day in February, then te minimum array suggested would be:

• 789 Watt array * 1/0.50 base power "fudge factor" = 1,596 Watt array minimum base load support

And an MPPT controller for that size array would need to be rated at:

• 1,596 Watt array * 0.77 panel+controller derating * 1/14.5 volts charging = 85 Amps @ 12 volt minimum suggested MPPT charge controller

This is a lot of guesses and a fairly conservative design (for 9 months of the year, this system would meet your needs).

If you did things like moving to a smaller AC inverter (300 Watt unit with 6 Watt Tare), used 12 VDC to power your your smaller devices (watch the ratings of the DC devices and cigarette lighter usb converters, a true deep cycle system will see the battery bus voltage range from ~10.5 volts to 16 VDC--Not all "12 volt devices" will work on such a wide range--And an AC Inverter can make things easier).

For off grid power systems, conservation is your friend here. It costs more to generate power than to conserve it.

A system 1/2 this size could work quite nicely for you if this was for use in a summer cabin. But if this was a full time off grid 9-12 month per year "home", then the larger system is going to work much better for you.

-Bill

brownbear

Question. How many 100watt panels can a 20amp charge controller take? I'm going to order a 2nd one but considering maybe getting a total of 3 or 4?   Can someone suggest a 250-300watt inverter pure since?  I also wanted to do the 6V battery and get two of them to make 12V just have to series them?  Did I get that right?

BB.

I forgot you are in Los Angeles CA, and not in Washington state... The hours of sun would look like this (a lot more winter sun vs Washington State):
http://www.solarelectricityhandbook.com/solar-irradiance.html

Los Angeles
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 56° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
4.50	4.82	6.05	6.78	6.83	6.80
Jul	Aug	Sep	Oct	Nov	Dec
6.69	6.67	6.40	5.85	5.07	4.41

How many panels can the controller support--You really need to check the manual for that... But the rough math would be:

• 20 amps max * 18 volts Vmp = 360 Watts for PWM (or some may derate by 0.80x)
• 20 amps * 14.5 volts charging * 1/0.77 panel+controller derating = 377 Watts for a MPPT charge controller

Yours looks like it may be a PWM controller (MPPT controllers generally have better heat sinking).

Yes, 2x 6 volt @ ~200 AH "golf cart" batteries in series would give you nice 12 volt @ ~200 AH battery bank.

-Bill

brownbear

Another question. If I get two 6V 200ah batteries and series them will I have a total of 400ah?

mcgivor

No you'll have 200Ah at 12V 

BB.

When you put 2x batteries in series, the voltage adds (6+6=12 volts).

To answer your question. 2x 6 volts @ 200 AH "golf cart" batteries in series will give you a 12 volt @ 200 AH battery bank

When you put 2x batteries in parallel, the capacity adds (200+200=400 AH)

If you have (for example) 4x 6 volts @ 200 AH batteries...

Put 2x batteries in series (for a 12 volt) string, put the 2nd set of batteries in series for another 12 volt string. Then connect the two strings (12 volts @ 200 AH) together in parallel and now you have 12 volts @ 400 AH.

You could also take those 4x batteries and put all of them in series and get 6+6+6+6=24 volts @ 200 AH.

Note, we are obeying the laws of physics here... The 4 batteries in different configurations still store the same amount of energy:

• 12 volts * 400 AH = 4,800 Watt*Hours of stored energy (2x series and 2x strings in parallel for 4 batteries)
• 24 volts * 200 AH = 4,800 Watt*Hours of stored energy (4x series connected batteries)

Amps and Volts are "partial units"... You need to know both to figure out the amount of power (Watts--a Rate of energy flow) or energy (Watt*Hours--total amount of energy).

Watts (and Watt*Hours) is a "complete" unit. It tells us the amount power or energy in the system... For example:

• Volts * Amps = Power (Watts) -- Rate of energy flow
• 12 volts * 10 amps = 120 Watts (a rate, like miles per hour)--such as a DC load (at 12 volts)
• 120 volts * 1 amps = 120 Watts -- Such as an AC load at 120 Volts

And, how much energy is used (the amount, like miles driven):

• Volts * Amps * Hours = (Watt*Hours) -- Total amount of energy used (or stored in the battery bank)
• 12 volts * 10 amps * 5 hours of use = 600 Watt*Hours (at 12 volts DC)
• 120 volts * 1 amps * 5 hours of use = 600 Watt*Hours (at 120 Volts AC)

-Bill

Estragon

I have a 300w Morningstar PSW inverter (bought from our hosts) that I'm quite happy with.  It has low idle/low-load losses, and the ability to easily add a remote on/off switch.

brownbear

I don't understand why they advertise these batteries as 500ah when its two 6v batteries 260ah each.  If I series the two it would be 12v 260ah. Is that correct?

BB.

You are correct... This seems to come from the Cell Phone/small lithium battery device.

From what I have seen, the small Li battery mfg will tell you it is a "4,000 mAH" battery.... But, it appears that it is two (for example) 3.5 volt cells each 2,000 mAH--But the device needs two batteries in series to operate or ~7 VDC @ 2,000 mAH.

I don't know how wide spread this is, but it is sort of correct--There are two 6 volt @ 260 AH for "520AH of 6 volt batteries" that can (and usually will) be configured into a 12 volt bank (but, as you say, a 12 volt @ 260 AH).

Yes, it is false advertising. You could find 5 hp air compressors that would plug into a 120 VAC 15 amp circuit -- Which can only deliver around 1.5 HP maximum worth of power (losses, power factor, etc.).

Look at this shop vac:

https://www.homedepot.com/p/RIDGID-16-Gal-6-5-Peak-HP-Stainless-Steel-Wet-Dry-Vac-WD1956/100638347

6.5 HP peak vacuum... On a 120 VAC (@ 15 amp circuit?)... At best (100% efficiency), you could get 1.5 to 2 HP--And nothing is 100% efficient (other than an electric heater). And look at the specs:

• 6.5 peak HP motor provides powerful suction for heavy-duty cleanups
• Peak Horsepower represents a level at or below the maximum horsepower output of an electric motor tested in a laboratory using a dynamometer

Peak Horsepower a level at or below the maximum output of an electric motor being tested in a laboratory... What the heck does that mean (peak HP is less than actual HP).

My guess, they connect the motor to a dyno and hit the motor with a huge torque from the load, and the momentum of the motor slowing down is "peak HP" (momentum HP + motor HP from electric power). 

There was a lawsuit the was settled in ~2014 for advertising a 1 HP compressor at 6 HP, etc. They would buy motors that had nameplates with the HP rating conveniently blank (same electrical ratings as last year's 1 HP compressor motor, etc.).

And there were issues before that with stereo systems that had crazy high (wattage) audio outputs that the federal government put laws in place to "fix" the marketing hype.

When I used to work in an auto repair place 45 years ago... The auto dealers had a saying that that they wanted to hire sales people that knew nothing about cars. Because they would say pretty much anything (probably a lot of that learned from their coworkers) and believe it--And the customers believed it too (no evidence of lying--It is not a lie if you believe it).

Sort what we help do here--Help to educate people about solar/off grid power. Even if most people end up paying somebody to design and install their systems, the customers are now enformed and can (better) separate the wheat from the chaff.

-Bill

brownbear

My MT-50 doesn't show the State of Charge (SOC) is there a way to read my battery level? I don't want to discharge it lower than 50%. Can I read it by the voltage under the battery? Ive attached a pic but having a hard time figuring it out.  

BB.

That is a tough question with AGM batteries.... You could always go with a Battery Monitor (and current shunt):''

https://www.solar-electric.com/bogart-engineering-tm-2030-rv-battery-monitor.html ($150 + $50 for current shunt and wiring)
https://www.solar-electric.com/midnite-solar-mnbcms.html (voltage only monitor $52)

You can use the charge from the voltage only monitor as a starting point for state of charge:

https://www.solar-electric.com/lib/wind-sun/MNBCM-brochure.pdf

Problem is that lead acid battery voltage varies with state of charge, current draw/charging, age, temperature, etc... Probably don't want to draw the battery below ~12.0 to 12.2 volts (light load)... We have used ~11.5 volts to not go below when substantial loads are on the battery bank.

And why a flooded cell lead acid battery is nice, especially for learning about solar/battery systems. You can use a hydrometer and measure the specific gravity of the electrolyte at any time--This is "more or less" the gold standard for determining battery state of charge (FLA battery).

Current shunt BMS are nice--More or less, lead acid batteries are near 100% efficient for current (i.e., 50 AH out to load, need ~50 AH back for charging). But even BMS can get confused and drift over time (typically, the BMS resets back to 100% charge if the battery is >14.7 volts for FLA for 2 hours or so).

Batteries are a "consumable" for off grid power systems... Depending on how you use them, they may last 3-5 years (for smaller/cheaper batteries) or they may last a few weeks (if murdered by the user--Which is pretty common for first time users).

Use the system, be consistent, and keep track at how it performs. When the battery dies--Then you know the life based on your usage. And you can decide what to do next (more solar panels, less loads, change charging set points, recharge during bad weather with a genset/utility power, try different battery, etc.). And sometimes, folks end up with "dead batteries" and they have no idea how or why they died (user error, mfg issues, distributor issues, etc.).

-Bill

brownbear

I found this on the internet and it says to not let the battery go below 12.35.   So I turned off my inverter at 12.3 and then it went up to 12.5.  What does that mean?   Does it mean that when I have a small load like modem, router and roku and it reaches 12.1 I'll turn off the inverter the battery will go up to 12.3?  

mcgivor

The 12.25V for 50% DOD is correct, loads will depress the voltage, as you've discovered, the amount of rebound in voltage would largely be influenced by the  load current as well as the amount of time given to recover. Not an exact science, some experimenting would be required, try the 12.10V as a cut off voltage see what it recovers to after 4 hours, if higher or lower than the target 12.25V adjust accordingly. Don't get too hung up on exact figures just aim for close, +/-  a few hundredths of a volt won't make much difference in the big picture, even measured voltage with a digital multimeter can be as much as +/- 5% of actual.depending on quality of the instrument.

littleharbor2

State of charge by voltage isn't very accurate, as already mentioned. The meter does show an approx. state of charge though. The state of charge is represented by the battery symbol and how full the battery is with the dark lines. As you can see the battery SOC here appears to be 100% with a lower voltage. 12.7 volts is 100% for a fully charged, rested battery. Yes, it is a tad confusing. You should get to know your system in time and be able to decipher the approx. state of charge a bit better. Bear in mind, as batteries get closer to their end of life. they will appear to charge up faster, but will discharge faster yet because of lost capacity. 

mike95490

And this is why folks will forever be disappointed with batteries.  They are not really plug-n-play gadgets.  They are electro-chemical power plants, and until you understand how all the interrelated parts work together, you will be baffled with voltage sag, voltage recovery, sulfation, and a boatload of technical stuff that goes wrong.  Packing it into a tote and putting a graphic monitor on it, does nothing to solve the problems, the user still has to learn to interpolate what the display means.   x4 for Li battery systems.

 

brownbear

Right now I have a VMax 125ah battery.  I'm leaning towards buying a 2nd VMax 125ah battery and parallel them? To get 250ah battery at 12V.  I wanted to ask if there is a better option out there like one 12V battery with around 500ah.   I can't find anything like that online. Can someone suggest a battery bc I really want to run my 65inch tv.  I'm already going to get a 2nd 100watt panel.   

BB.

Just to be clear (and safe) you parallel connect 2x 12 volt @ 125 AH for a 12 volt @ 250 AH battery bank. (+ to +, - to - battery connections).

If you put the batteries in series, you will get a 24 volts @ 125 AH battery bank.

Be very clear and careful with your DC battery connections. You can easily fry your electronics and or get some electrical (or even chemical) fire works.

Bill

brownbear

Yes parallel to get 12V 250ah

MrM1

brownbear said:

Right now I have a VMax 125ah battery.  I'm leaning towards buying a 2nd VMax 125ah battery and parallel them? To get 250ah battery at 12V.  I wanted to ask if there is a better option out there like one 12V battery with around 500ah.   I can't find anything like that online. Can someone suggest a battery bc I really want to run my 65inch tv.  I'm already going to get a 2nd 100watt panel.   

I think the reason you cannot find many 500ah 12v batteries is because it would be a very large and heavy battery.  IMHO the load requirements you are describing are moving more and more away from a 12v system.  You would be better served with 24 or 48v

brownbear

Is it ok if I parallel 2 or 3 of these 125ah batteries to get 250ah or 375ah at 12V 

MrM1

Yes but the parallel batteries you have,  the harder it is to get consistent charge current going to each battery so you end up with charge variations ranging from some batteries being undercharged and some possibly being over charged.  General rule of thumb is 2 parallel strings and no more than 3. 

MrM1

If you must parallel

http://www.smartgauge.co.uk/batt_con.html