I just got my 100W/18V solar panel form Renogy and I want to use it for a small circulation pump in the pond - for now. What would be a good battery choice here to make this pump run 24/7. Pump is no more than 15W 12VDC. I plan to power more devices in the future like lights, clock, weather station.
I would like to use lipo batteries but there is variety of them so good advice would be helpful.
Maybe 6S drone lipos or some with large mAh. I am not sure what feature decides about how fast battery can be charged.
You need to choose a battery with the appropriate voltage and sufficient capacity (measured in Ampere hours) to run the circuitry for the longest period of night/cloudy days that you require.
To be safe, the solar panel has to be larger than required to resupply those Ampere hours during the expected periods of sunlight, which depends on your region and the weather, of course. The one panel you have may not be sufficient.
LiPo's with a solar charge controller sounds doable - the panel can provide upto 5A or so so a high current rated
LiPo pack would make sense. Alternatively throttle back the charging current when sunny (overcast days are
the worst case and you'll probably only get 0.5A then.).
Is the panel 18V open circuit, or designed for 18V battery packs? You should include links for the hardware you
are talking about...
15W for 16 hours (winter night-time) is 240Wh, which for a 22.2V pack is about 11Ah, to give a guide, but remember battery capacity drops with use significantly - if you need 11Ah, get 20Ah pack and it'll still be
able to hold enough charge for a much longer life than a 12Ah one.
As with all rechargeable batteries a charge-controller is essential - over-charging or over-discharging can
destroy a rechargable battery pack in very short order (and with lithium even cause a fire).
I see solar controllers with output 12/24V - so what do I do with non standard voltage lipo like 15V or 17V?
There are 22V and 11V - not sure if there is more. What lipo battery would be best here - there is variety of drone batteries - above calculations of Mr MarkT show 1200mAh would do justfine - but what do do with voltage?
If I buck it - will controller have any idea how to recognize battery type?
jremington:
A lead-acid battery takes more abuse and is much safer than LiPo batteries, plus the charge controllers are cheap and reliable.
I am quite happy with the Sunforce controllers. This one is all you need for a 100W panel.
That's exactly what I was thinking as I read this thread - why is the OP talking LiPo when the obvious answer is good ol' Pb-H+. I have a solar system that uses LiPo, but it runs at 3V, not 12. With lead acid, a 12 volt system is a natural.
Your panel is too small.
200 watts is nearer the mark.
Running the pump 24/7 needs 360 wh per day which will require 3.6 sun hours a day over the year.
Unless you live somewhere near the equator and have no cloudy days, your system will fail in winter.
You will also need a MPPT based charger to get all you can out of the solar panel.
Solar is unreliable power. Don't exect that you can run that pump 24/7 from a 100watt panel.
A 12volt/15watt pump draws 1.25Amp from a 12volt battery.
That's 1.25*24= 30Ah per day/night.
A deep-cycle battery shouldn't be drained below 50-60% charge if you want it to last more than a year,
so you need at least a 100Ah deep-cycle battery to bridge one day/night.
12volt/100Ah is about twice the size of an average car battery.
Don't be tempted to use a common car battery, unless you don't mind replacing it twice a year.
Rule of dumbs is that you should be able to top up the battery to 100% in four hours with a panel.
That's a panel that can deliver 10Amp during peak sunshine, or 180watt (assuming low battery efficiency and dumb controller).
So the panel must be able to deliver 180watt during rainy days.
100watt panel???
Leo..
mauried:
Your panel is too small.
200 watts is nearer the mark.
Running the pump 24/7 needs 360 wh per day which will require 3.6 sun hours a day over the year.
Unless you live somewhere near the equator and have no cloudy days, your system will fail in winter. You will also need a MPPT based charger to get all you can out of the solar panel.
Is this the case? I've been using a MPPT (Sparkfun's Sunny Buddy - which then supplied an Adafruit LiPo backpack for a Trinket Pro) and I recently discovered that going directly from the solar panel to the battery charger work better (faster, more consistent charging) than using the MPPT board.
But then I live in Arizona, where we have 3.6 sun hours per day several times over, in the shade. Why this state isn't the major proponent of solar power, I do not know.
Wawa:
Solar is unreliable power. Don't exect that you can run that pump 24/7 from a 100watt panel.
A 12volt/15watt pump draws 1.25Amp from a 12volt battery.
That's 1.25*24= 30Ah per day/night.
A deep-cycle battery shouldn't be drained below 50-60% charge if you want it to last more than a year,
so you need at least a 100Ah deep-cycle battery to bridge one day/night.
12volt/100Ah is about twice the size of an average car battery.
Don't be tempted to use a common car battery, unless you don't mind replacing it twice a year.
Rule of dumbs is that you should be able to top up the battery to 100% in four hours with a panel.
That's a panel that can deliver 10Amp during peak sunshine, or 180watt (assuming low battery efficiency and dumb controller).
So the panel must be able to deliver 180watt during rainy days.
100watt panel???
Leo..
OP could use a farm equipment battery and twice (or more) as many solar cells to get enough power.
100watt might do it if you have full sun every day.
Solar power output drops like a brick on overcast/rainy days.
100-200watt per square meter (instead of 1000) today where I live (45 south).
Where do you live (latitude).
Leo..
In your first post you stated a 15 watt pump, but that link is for a 10 watt pump.
If its a 10 watt pump then the sums change a bit.
A 10 watt pump running 24/7 consumes 240 wh, so that drops the panel requirement to
2.4 sun hours per day.
It might just work depending on your latitude.
Whats the maximum number of cloudy days that you get in a row?
I may balance the pump power load with microcontroller. The power definitely does not have to be on full load all the time but variable to the charge state. I don't know if there are sophisticated solar controllers like and it is interesting how they estimate the battery charge status which im guessing is non linear.
The only way to get a reasonable measure of battery capacity is a technique called coulomb counting, which is just a fancy way of measuring the amount of energy going into the battery and measuring how much comes out, and the differance is how much charge the battery has left.
Even this technique needs periodic calibration to keep the measurement accurate.
I may balance the pump power load with microcontroller.
Not a chance of that working, since you either don't understand or won't pay attention to the very simple, straightforward and sensible advice you have already received.
jremington:
Not a chance of that working, since you either don't understand or won't pay attention to the very simple, straightforward and sensible advice you have already received.
And why is that? Those are strong statements. Of course it is possible and feasible. Why not??
Solar controllers are in some sense power load balancers and for sure use some cpu algorithms to manage voltage and current.
The load on the pump is based on the head of water its trying to pump.
If all you do is reduce the voltage to the pump to reduce its power consumption it will simply stall and stop pumping.
The only way to conserve power to the pump will be to simply turn it off when your battery gets flat.
The safest way to run your system is to turn the pump off at night and only run it during the day.
That way you are most likley to retain sufficient charge in the battery to keep the pump running on low light days without totally flattening the battery.