Solar Charge controller - DC input

Hey guys,

I have read about solar charge controllers being used in hybrid with solar and mains, to charge the SLA batteries,

I want to replicate this on a very smaller scale, and instead of a dc inverter, I want to use the output directly to power a 12v-500mA WiFi router.

I have found a few cheap SCC's on aliexpress

http://www.aliexpress.com/item/MPPT-Solar-Charge-Controller-Solar-Panel-Battery-Regulator-Safe-Protection-Controle-20A-12V-24V-Regulator/1932534358.html

They are good for upto 20A so its way too much for my application. I want a miniature version if it exists. Just need help authenticating my idea.

how will it be wired ?

something like

Battery ---- Charger controller ----- modem ?

Battery will charged with what ?

CMP12_solar_charge_controller_regulator_

Only in this case, instead of a 18v solar panel, I am going to use a 15v ac-dc adapter, The charge controller has dedicated terminals for splits the input supply and charges the battery+powers the load as long as there is power from the mains. When the power goes out, the load (12v WiFi router) will be powered from the batteries until the power comes back on.

The only reason I am leaning towards this idea is because of the controller has SLA charging , cut off feature, overcharge (14.4V) protection, Overdischarge protection (10.8V) , reverse polarity protection.. which is basically what is required for a 100% un-attended duty cycle 24/7 (365days a year).

[quote=“djayz, post:, topic:”]

Hey guys,

I have read about solar charge controllers being used in hybrid with solar and mains, to charge the SLA batteries,

I want to replicate this on a very smaller scale, and instead of a dc inverter, I want to use the output directly to power a 12v-500mA WiFi router.

I have found a few cheap SCC's on aliexpress

http://www.aliexpress.com/item/MPPT-Solar-Charge-Controller-Solar-Panel-Battery-Regulator-Safe-Protection-Controle-20A-12V-24V-Regulator/1932534358.html

They are good for upto 20A so its way too much for my application. I want a miniature version if it exists. Just need help authenticating my idea.

[/quote]

why not just buy a simple APC ups , a very small sized one, with very small batteries.. eg bike batteries? this should last you for around 1.5 - 2.5 years un attended with only a few drops of water every few months.

APC has better OV, UV cutoff. better sine wave control and unlike CC, no constant drain cycles.. plus their float is easy on the battery too.

if you do go for SLA, then even better, as APC are better optimized for Dry batteries primarily, we forcefully use flooded with them. this saves you a lot of cost.. cz ultimately you would still be using wapda mains for adopter power.

Thanks for the input farhan_ds I do have a dedicated 24V ups for our house which I can connect right away but I dont want to put a 5w continuous load on the UPS, and there is a complete blackout atleast twice a year for 6-10 hours (sometimes more often because of grid/transformer failures) and I dont want to be bothered even in that scenario.

I want to use a 12V 7Ah SLA battery - dedicated to the modem, but In order to go about the solution I want to do it properly.

I could use a APC UPS but I am not sure where can I get something that small (100W maybe?)

Also I donot want to add the inverter step, and cause more energy losses for such a small application, as in case of my current design idea it is fairly simple, the controller has a 4-stage SLA charging mode, and all the protection features for the battery, and the power supply is intelligently controlled on two different channels.

And even better way to go about this situation is to get a 10W ($10) solar panel with the charge controller ($8) and ditch the APC altogather.

I want to be able to make something that is solid, and can work for atleast 2-years, unattended.

Let's do some maths

12 * .5 = 6W

6 * 24 = 144WH

144 Watts*Hours * 1/12 volt battery * 1 days of storage * 1/0.50 maximum discharge = 24H @ 12V

or

144 Watts*Hours * 1/24 volt battery * 1 days of storage * 1/0.50 maximum discharge = 12AH @ 24V


6 Watts * 24 hours * 1/0.62 DC system off grid eff * 1/5 hours minimum sun (9 months a year) = 46 Watt array minimum for 12 VDC system


That is for a completely off grid system.

A charge controller do act as a parasite load, but that is included in the above calculations.

Now choice is yours.

For 24V system efficiency will be a bit higher or if you use 48V system using 4 smallest 12V available , it will be even higher, but it depends whether the solar charge controller you will be using support 24 or 48V batteries.

That explains it, thanks a bunch yousef. So I need a 50W solar panel, and a 12AH battery (12v) system to be completely off grid, for a 6W load (24/-365days) unattended.

[quote=“djayz, post:8, topic:21420”]

That explains it, thanks a bunch yousef. So I need a 50W solar panel, and a 12AH battery (12v) system to be completely off grid, for a 6W load (24/-365days) unattended.

[/quote]

a 24AH battery @12V

or

2 x 12AH batteries @24V

Does this charge controller looks okay for my application.

http://www.aliexpress.com/item/MPPT-Solar-Charge-Controller-Solar-Panel-Battery-Regulator-Safe-Protection-Controle-20A-12V-24V-Regulator/1932534358.html

I would be glad if I could get it locally, If you know of some place do let me know.

[quote=“djayz, post:10, topic:21420”]

Does this charge controller looks okay for my application.

http://www.aliexpress.com/item/MPPT-Solar-Charge-Controller-Solar-Panel-Battery-Regulator-Safe-Protection-Controle-20A-12V-24V-Regulator/1932534358.html

I would be glad if I could get it locally, If you know of some place do let me know.

[/quote]

By the looks of it, is not a MPPT charger.

Anyway, for your application, you don't need MPPT either, just buy a quality 5-10A PWM charger from Hall road or a solar installer, there might a few near Johar town too.

Just make sure, it has the features which you need e.g LVD (Low voltage disconnect) and Over voltage protection and get at least 1 year warranty with it.

[quote=“djayz, post:8, topic:21420”]

That explains it, thanks a bunch yousef. So I need a 50W solar panel, and a 12AH battery (12v) system to be completely off grid, for a 6W load (24/-365days) unattended.

[/quote]

i think you are not sure about using the conversion and solar power charger usage.

the CC will convert high VDC to low VDC, in your case a power adopter running on wapda i guess.. if you think, what i am assuming is right you are already doing double stage conversion and power losses

Wapda >Adopter> CC> battery or appliance directly.;; am i right?

in that case, adopter is doing AC-DC , then going to CC which will reduce voltages and even with highest efficiency will go max upto 90%. so in effect, there will be double conversions.

if you already have a home UPS system such a small load would put almost no effect on backup of the setup. as for keeping it separate totally, a separate UPS would be a much suitable .. you can simply add any solar panel on top to get free electricity in day time which would not have wastage since there would be no conversions in charging the battery.

using small panels alone would be sometimes insufficient as in cloudy days or whole monsoon rains and winters where there are multiple days without decent sun you canot charge your battery from solar alone. and then the whole adopter setup would be a time wastage every other week..

a proper practical solution for quality charging and long life of battery is a UPS.., an APC ups has a very high UV cut off, above 11V, has AVR, has good efficiency and PF, and also has a good float V to keep batteries topped up. Wet battery should easily last over 2 years with that. and since it would be 24V, it should be plenty of backup for any other thing you might want to connect with it further. Cyberpower and inverex should be plenty for such needs as well. and in any of them you can always add solar panels to keep a charging source whenever light goes in day time.

you can be billions of calculations done and then there is a practical way to solve problems.. for long durations.

a 10A PWM shouldn't cost more than Rs1500 while a UPS will be in thousands.

Calculations matter, don't they ;)

[quote=“farhan_ds, post:12, topic:21420”]

i think you are not sure about using the conversion and solar power charger usage.

the CC will convert high VDC to low VDC, in your case a power adopter running on wapda i guess.. if you think, what i am assuming is right you are already doing double stage conversion and power losses

Wapda >Adopter> CC> battery or appliance directly.;; am i right?

in that case, adopter is doing AC-DC , then going to CC which will reduce voltages and even with highest efficiency will go max upto 90%. so in effect, there will be double conversions.

if you already have a home UPS system such a small load would put almost no effect on backup of the setup. as for keeping it separate totally, a separate UPS would be a much suitable .. you can simply add any solar panel on top to get free electricity in day time which would not have wastage since there would be no conversions in charging the battery.

using small panels alone would be sometimes insufficient as in cloudy days or whole monsoon rains and winters where there are multiple days without decent sun you canot charge your battery from solar alone. and then the whole adopter setup would be a time wastage every other week..

a proper practical solution for quality charging and long life of battery is a UPS.., an APC ups has a very high UV cut off, above 11V, has AVR, has good efficiency and PF, and also has a good float V to keep batteries topped up. Wet battery should easily last over 2 years with that. and since it would be 24V, it should be plenty of backup for any other thing you might want to connect with it further. Cyberpower and inverex should be plenty for such needs as well. and in any of them you can always add solar panels to keep a charging source whenever light goes in day time.

you can be billions of calculations done and then there is a practical way to solve problems.. for long durations.

[/quote]

I understand you have some unconditional love for the APC , It definitely is an engineering masterpiece, appreciate the suggestion , but they do cost a bit more than what Im trying to accomplish here.

A Solar CC is going to accomplish nothing less than APC, and it has all the bells and whistles for SLA charging. It also offer separate channels for , Solar Panel/DC-Adapter ; SLA battery ; DC 12V Load , on the plus side It gives me room for future upgrades and replacing ac-dc adapter, with solar panels instead.

Wouldnt you go off-grid instead?

P.S: My load is 12VDC so I dont really need the inversion step 12VDC-220VAC to so I can convert it back to 12V using the stock AC-DC adapter, that just sounds pointless.

i dont have any special love for a specific brand.. its just they are better than any other option available here.. had there been a better brand i would have preferred that.. unfortunately we are stuck with limited choice and limited stock availability.. and local brands are over priced for their features and capacity.

MGE inverters used to come but they dont any more, so did a rare few pieces of Schneider industrial.. no more.

as for the steps, you are again reversing them..

[quote=", post:, topic:"]
I dont really need the inversion step 12VDC-220VAC to so I can convert it back to 12V using the stock AC-DC adapter
[/quote]

its 220V UPS ---> direct adopter DC V... one step solar power is coming from another source and simply adding upto batteries.. not being converted.

your original way in 1st post was Wapda 220 -> Adopter 15V> CC 12V > Battery> Router. dont you see any problem in this?

now you propose offgrid Panel > CC > battery > router.

even in this situation, consider having 2-3 rainy/ cloudy days, when all your battery power is consumed and you have no way to charge it except using wapda again which you didnot connect cz trying to make its independent.. offgrid completely isnt possible then in such situation.

also

why go total offgrid when you can do hybrid? add panels to same battery set in future along with UPS and it will keep it topped up for free and wont consume wapda at all in day for charging battery, as they will be in float from solar and more backup from unused power in night .

also

you WILL 100000% increase your load demand in future.. everyone does, power is most important necessity. will your entire setup be able to provide any AC power? no, cz it would be just a DC 12v setup, you would have to add an inverter to utilize your excess power for anything 220V else. the cost of adding an inverter will again add up to your current scenario.. or would you rather buy a new set of CC, panel, and battery for Every single item you need to add in future every time you need free solar?.

you are going to spend quite a few bucks for your current setup. why not go for a one time more for future proofing it.. you can do with ANY UPS..even a good desi ups will work will future solar upgrade as yousaf is already using at his home fine. cheaper ups will save you a lot.

PS: i am not in mood to fight / Behas for the sake of Behas for proving self righteousness with anyone else.. it was just a practical suggestion for OP from my perspective only... if OP is up for electrical experimentation, he is most welcome to try .. this post is NOT UP FOR DEBATE ..

and djayz.. please let us all know results of success., we all learn from our trials . please do share your results so we all can learn and improve.

For 2-3 days just modify the calculations

144 Watts*Hours * 1/12 volt battery * 2 days of storage * 1/0.50 maximum discharge = 48H @ 12V

or

144 Watts*Hours * 1/24 volt battery * 2 days of storage * 1/0.50 maximum discharge = 24AH @ 24V

6 Watts * 48 hours * 1/0.62 DC system off grid eff * 1/5 hours minimum sun (9 months a year) = 93 Watt array minimum for 12 VDC system

That is for a completely off grid system.

Your other loads are on the current UPS aren't they ?

IMO there is no issue of expansion.

[quote=“farhan_ds, post:15, topic:21420”]

1. your original way in 1st post was Wapda 220 -> Adopter 15V> CC 12V > Battery> Router. dont you see any problem in this?

2. why go total offgrid when you can do hybrid? add panels to same battery set in future along with UPS and it will keep it topped up for free and wont consume wapda at all in day for charging battery, as they will be in float from solar and more backup from unused power in night .

also

and djayz.. please let us all know results of success., we all learn from our trials . please do share your results so we all can learn and improve.

[/quote]

1. My Original way was (WP DIY-ish UPS Tutorial)

220VAC > 13.5VDC Adapter > SLA Battery > WiFi/Router

Cons: Pretty basic, but not a proper way. Huge capacity drop in batteries over a matter of few months.

I Upgraded to, 3 Step - Charger (SUOER 5Amp) specially designed for SLA.

220VAC > 5A (3-step) SLA Charger > Battery > WiFi Router

This is my current setup. It is working flawlessly for about a year, But I read somewhere that is also is not the proper way. If the battery is under constant load the 3-step charger will only work on a CV mode (because the load current never falls low enough to enter Float mode) and keeping the battery at 14.4V at all times.

2. I have a giant ass UPS and a decent battery bank for the house, This is more of a personal challenge and to come up with a way which is cheap-as-possible and works for years to come. Just a matter of time and figuring out economics.

I like the idea of being completely off-grid, but for a 6W application I highly doubt I personally(or anyone ftm) would jump right into it.

For a second , disregard if the power comes from a solar panel or AC-DC adapter, Its just a matter of how deep one can dig into his pockets.

This looks more like a science project than a convenience facility.. in that case, your experiment could be fruitful and a fun activity.. :) do post results..

[quote=", post:, topic:"]

If the battery is under constant load the 3-step charger will only work on a CV mode (because the load current never falls low enough to enter Float mode) and keeping the battery at 14.4V at all times.
[/quote]

this is exactly why i suggest using a ups.. as long as its on wapda, ups will bring it to 27V and not use its power. further solar will simply add to 28.4V and keep it at whatever float V is set since no power is being used as ups is maintaining the minimal Voltage and no cycle use. if you connect the CC to charge battery it will always be in constant cycle use, and also in variable voltage under any solar or similar source..

[quote=", post:, topic:"]

I Upgraded to, 3 Step - Charger (SUOER 5Amp) specially designed for SLA.

220VAC > 5A (3-step) SLA Charger > Battery > WiFi Router

[/quote]

for keeping battery on float at that rate, you would have needed a 10 amp charger atleast which would be able to provide enough amps to produce a decent boost and float volt. that would solve your problem.

with off-grid solar , batteries do a 1 cycle per day unlike UPS which will do multiple partial cycles (as high as 12 cycles or even more ). Battery life is directly related to number and depth of cycles.

Battery will last longer on solar.

During the day, when batteries are in float (after 9-10Am), load will be using solar power "directly".