Solar charging a 12v battery

[Bill M]

I'm not versed at all with this process. I have a Solar Panel 25W 12V Monocrystalline Panel that is part of submersible recirculating pond pump system. The power pack recommended is junk so I bought a 12v 9aH feeder battery. Will the panel work to charge the battery in a direct line between the pump and the solar panel? I have no idea if when used in a feeder application whether there are other electronics involved in the process. Hope this makes sense. Thanks.

EDIT TO ADD: I see I likely need a charge controller. The pump being run is this one. 12V - 24V DC Brushless Submersible Water Pump, 410GPH . Any advise would be great. Thanks.

[kmitchl]

To answer your question, I don’t know with the info available. Solar systems depend on replacing all the amp hours used by the pump with amp hours from the solar panel. The charge controller is used to make sure the solar panel does not overcharge the battery. I would suggest hooking it up and seeing how it works. Worst thing that happens is you over charge the battery and it’s toast.

[91cavgt]

From what I have just briefly skimmed over, the 9ah battery and the 25 watt solar panel won’t be enough to keep the pump running 24/7 even if you get a charge controller. A batteries amp/hr rating means it can provide XX amps for 20 hours. So that would be 9 amps total over a 20 hour period. So divide 9 by 20 and you get 0.45 which means that battery can support about half an amp for 20 hours. Unfortunately, if you use an AGM or flooded battery to its full capacity, it won’t last long. That’s because the battery voltage will end up dropping too low which will decrease its lifespan. A 25 watt solar panel will put out a little over 1 amp in good sunlight on average for most of day light hours…. on average. If it is cloudy or rainy, it will put out less power.


If you don’t care about it running 24/7 then just hook the pump directly up to the 25 watt panel and you will be fine. But if you want it to run 24/7 then you are going to need a larger system than what you have. Preferably, a 100 watt solar panel and a battery of at least 50 amp/hr. Then also add a solar charge controller. If you go this last route then find an MPPT solar charge controller as it will be more efficient and utilize the power from the solar panel better than a PWM charge controller.

I’ve been playing with solar for about 15 years now and it is a hobby for me. If you’ve got any questions then don’t hesitate to ask.

[Bill M]

I appreciate the replies. I am not wanting it to run 24/7, only during daylight hours. If a sunny day, the solar operates the pump fine without the help of a battery. I had hoped to store in the battery for days of less sun. Not possible with what I have I suppose? Any suggestions on reading about this. This is what it is for, small bird pond. Water comes to the waterfall, to the old pump and a small fountain head.

[91cavgt]

If you just want it for daylight hours, and the battery just for rainy days then what you have might just work.


What you would need is a programmable charge controller. Most decent ones have an output for a device to be powered off of the charge controller, like a light. Well, if you get one that the time is programmable then you can program the fountain to run, say from 10am till 4pm or so. On sunny days the battery will just be in a standby mode but on rainy or cloudy days then the battery would pick up the load. Now, if you had more than a couple of cloudy days in a row then your battery may get too low, but it all depends on how long the pump would be programmed to run. I’m going to look up the charge controllers that I use to see if the time is programmable on the output.

[Bill M]

If you just want it for daylight hours, and the battery just for rainy days then what you have might just work.


What you would need is a programmable charge controller. Most decent ones have an output for a device to be powered off of the charge controller, like a light. Well, if you get one that the time is programmable then you can program the fountain to run, say from 10am till 4pm or so. On sunny days the battery will just be in a standby mode but on rainy or cloudy days then the battery would pick up the load. Now, if you had more than a couple of cloudy days in a row then your battery may get too low, but it all depends on how long the pump would be programmed to run. I’m going to look up the charge controllers that I use to see if the time is programmable on the output.

Thank you. I appreciate any info you can provide me.

[imyomama]

if you are going to use a battery do yourself a favor and get a decent charge controller regardless.
and don't use the default settings either ... most of the ones i've used in the past have the cut off voltage way too low and will destroy the battery in no time .. same goes for the float voltage.

if it's not well balanced , be ready to constantly have to replace batteries.

also running off a panel directly could also be an issue .. if the panel can output way more than the motor uses , typical panels voltages can spike higher than recommended voltage on the motor itself and you'll end up smoking motors. a regulator can fix that..

[Bill M]

if you are going to use a battery do yourself a favor and get a decent charge controller regardless.
and don't use the default settings either ... most of the ones i've used in the past have the cut off voltage way too low and will destroy the battery in no time .. same goes for the float voltage.

if it's not well balanced , be ready to constantly have to replace batteries.

also running off a panel directly could also be an issue .. if the panel can output way more than the motor uses , typical panels voltages can spike higher than recommended voltage on the motor itself and you'll end up smoking motors. a regulator can fix that..

I realize that bundled deals may not always be perfectly matched but this panel was matched to the pump by the supplying company. It runs great with sunshine but obviously I don't know the long term results. The kit did receive good reviews however. I'm needing something in between that will help charge the battery for cloudy day standby.

I'm looking at two different controllers that I wondering about. What are opinions on these?

Controller 1

Controller 2

[Bill M]

This is helping "educate" me a bit on the subject. Hope y'all will bear with me. Hoping to get a bit of confirmation to what I think I've figured out.

If amps are equal to watts divided by volts, this pump would draw less than .5 amps. Is this correct? I found a battery run time calculator that would indicate a 12v 9aH AGM battery would run +/- 19 hours at that draw. Am I off base on this?






I found this controller to consider. There are different amp models available from 10 to 40. Using the below shown specs from the back of my solar panel, would this controller work and am I looking at extreme lengths of time to charge the battery with this panel?

LNEX Solar Charge Controller Waterproof, 20A Super Thin Solar Panel Battery Intelligent Regulator with LCD Display 12V/24V PWM Solar Controller for LiFePO4,AGM, Gel, Flooded and Lithium Battery




I thank y'all again for your patience and help.

[91cavgt]

I haven’t forgotten about this thread. Been super busy this weekend but I’ll post up on this later this week.

[Bill M]

I haven’t forgotten about this thread. Been super busy this weekend but I’ll post up on this later this week.

Appreciate it.

[Bill M]

TTT so the thread isn't buried.

I continue to research while waiting to hear from 91cavgt but either there isn't much info out there or I'm not looking in the right place.

[Bill M]

I am not sure I have been thinking about this correctly or explaining what I want to achieve well. This pump works well for my application which is a small bird pond/bath with a small waterfall, a "leaking" old hand pump, and a fountain at the opposite end from the waterfall. Photos earlier in the thread. The pump furnishes the correct amount of water to each of these when running at full power. This system supplier also has a battery backup that I returned for a couple of reasons. It is a 14.8V/2600mAh Backup lithium battery . It supposedly stored power for cloudy days but only for a 4-6 hour run.

I hoped to achieve having a battery on standby to use on these cloudy days when there isn't enough brightness to power the pump. It will operate on overcast days that are bright. After further digging, I'm thinking I can't do this with the equipment we have been discussing. I believe if I use a charge controller, the pump will be constantly drawing from the battery (not storing power) instead of running straight solar on sunny days. For this reason, I see why it would be important to be able to fully charge the battery with the controller/solar panel combination. For those that understand this technology, is this correct? If so, I'm looking to go the wrong way.

[Pedernal]

I believe you can accomplish what you want to do with a charge controller (CC) and a solar panel. There will be certain limitations depending on which devices you decide to go with.

Some CC are made specifically to run lights at night and therefore can be programmed to run the lights at certain times. I am not sure if the low end, inexpensive ones will be programmable. Most of the low end ones will just run lights in low light conditions to a certain level of battery capacity and cut off to prevent from overly discharging the battery. Obviously you would be running the pump versus lights so you need a programmable one to run the pump during daylight hours.

In my opinion, it would be best for you to find a timer circuit that activates the pump at whatever time you choose via programming . A simple sprinkler systems might be able to accomplish what you want. Also, relay timer circuits are inexpensive and are readily available. Obviously any additional electronics will be an additional power drain but it will be minimal.

Going off the battery capacity and run time listed in post # 13 I would venture your pump runs at about .5 AH. Based on that guesstimate I would multiply that .5 by the number of hours per day you want to run the pump to figure approximately how much capacity it will take to run the pump per day. Obviously if you want to run the pump for consecutive days of low light conditions you will need to figure that into your battery capacity.

Hope this helps and not add confusion. PM me your number and I can confuse you further

[Bill M]

I believe you can accomplish what you want to do with a charge controller (CC) and a solar panel. There will be certain limitations depending on which devices you decide to go with.

Some CC are made specifically to run lights at night and therefore can be programmed to run the lights at certain times. I am not sure if the low end, inexpensive ones will be programmable. Most of the low end ones will just run lights in low light conditions to a certain level of battery capacity and cut off to prevent from overly discharging the battery. Obviously you would be running the pump versus lights so you need a programmable one to run the pump during daylight hours.

In my opinion, it would be best for you to find a timer circuit that activates the pump at whatever time you choose via programming . A simple sprinkler systems might be able to accomplish what you want. Also, relay timer circuits are inexpensive and are readily available. Obviously any additional electronics will be an additional power drain but it will be minimal.

Going off the battery capacity and run time listed in post # 13 I would venture your pump runs at about .5 AH. Based on that guesstimate I would multiply that .5 by the number of hours per day you want to run the pump to figure approximately how much capacity it will take to run the pump per day. Obviously if you want to run the pump for consecutive days of low light conditions you will need to figure that into your battery capacity.

Hope this helps and not add confusion. PM me your number and I can confuse you further

I'd be happy to talk with you. I'll PM the number in a bit. Take a look at post #9 if you would. I saw timer that could be added on at Amazon. I'll have to see if I can find it again.