Solar panel powered pump - need advice

[capitanissa]

I plan to install a 12v tiny comet pump to pump the water from my cistern to the roof, where it will be stored for a gravity stored water system, house and garden. I have tons of sun, I only need to pump during the day, slow time. The pump I am looking to use is a 3amp comet pump from www.cometpumps.biz. What would be the recommended size of panel to do the job..do I actually need something that will constantly supply 3amps, or would the pump run on less - I don't plan to use a battery, unless it is absolutely necessary.
thanks for the answers, great site.

[Mike90250]

You need a Linear Current Booster to keep from burning the motor up at 8V when it can't run.

http://www.solar-electric.com/7amplincurbo.html

I would use a 17V 5A panel to drive this with, and a float switch to keep it off, when tank is full

[capitanissa]

many thanks!

This has got to be the fastest reply that I have ever received on a forum, I am very grateful, and I will now research the advice that you have given me and get busy building the system.
The "extra" advice is really important, and I will add a float switch.
many thanks

[bbug]

Sounds like you will need a 12 volt solar regulator, otherwise you wont be able to use it on a 12 volt system. Solar panels are usually about 18 volts each. So you cant connect them to anything, without a regulator, charge controller onto your MOD DELETED URL . You can even install a little battery, and keep the battery charged up by your solar panels and regulator. So you will have power all the time not just during the day time.

[capitanissa]

among the boating community there are varying opinions about using regulators,(I currently live on my boat) many say it is not worth it. I am surprised about the panels running at 18 volts, a lot of us have them directly connected to our boat batteries without any problem. I have used a regulator in the past, currently I don't have one as they seem to have a finite life...Usually a couple of years.
I take the point of using a small battery, adding that would not cost much and the system would be more efficient. I don't need to run the pump all the time, but I am wondering if having a battery is easier on the pump?
thanks for your advice and contribution.

[Mike90250]

I'm not sure what you call a regulator, but Solar Charge Controllers are needed when the PV produces more than 1% of the battery capacity. 1% charge rate, is considered a trickle charge, and won't generally hurt the battery.
Between 1% and 3% is a gray area, maybe the site has poor sun, or there are loads that prevent overcharge, but above 3% of battery capacity, you really need a 3 stage charge controller to prevent battery overcharge. These are not found on ebay which has lots of counterfeit parts. Try here for some reliable controllers.

In your case, with the pump and cistern, you need a "Linear Current Booster" as I wrote about in my earlier post to you, and you would not need any battery.

Also - disregard "bbug" comments, he's a spammer, making random solar sounding comments in order to post links and likely to be banned soon.

[capitanissa]

continued info

Thanks for the heads-up Mike.

[reststop]

Hello all, I'm new here and interested in this topic. I know just a little about solar system an by no means an expert. I would like to ask Mike about his adivce to use a device to limit the current. I am sure it would work as you suggest but I would like to know if it would work as well or better with a small battery and charge controller. Considering the cost of the current device I would have thought a good battery for less cost and maybe additional benefits of having a battery in the system might be the better choice. I am not disagreeing with your advice just trying to get a better understanding of this interesting use for a small solar system. Yea, first post. Regards,

Reststop

[Mike90250]

I would like to ask Mike about his adivce to use a device to limit the current. I am sure it would work as you suggest but I would like to know if it would work as well or better with a small battery and charge controller. ..

?? a device to limit the current ?? I said:
You need a Linear Current Booster to keep from burning the motor up at 8V when it can't run.
When you take a 12V motor, and feed it 8V, it does not have enough power to run the motor, so it sits in a stall condition, feeding current through only 1 coil winding, instead of cycling through all the windings as intended. A Linear Current Booster stores and manages the available power from the PV, and powers the motor in short bursts when there is low power, and full speed when conditions allow.

A charge controller and battery is more complicated and the battery needs water and replacing every year (under these conditions, the battery will wear very quickly).

[ecusolar]

http://cgi.ebay.com/DC-12V-Electric-Centrifugal-Water-Pump-103-GPH-P-38I-/250722722210?pt=LH_DefaultDomain_0&hash=item3a603d21a2

Try that, it's an energy saver made for it, runs since some moons for me.

Joe

(link points to DC 12V Electric Centrifugal Water Pump 103 GPH (P-38I) ) Mod.

[ecusolar]

Correction

Want to add something, I use this pump for heat circulation, for pumping water to the roof it might not be enough powerfull.
For that purpose I use Shurflo diapragma pumps, they cost about 60 USD in Ebay and are very reliable, use about 60W depending on model.

[reststop]

?? a device to limit the current ?? I said:
You need a Linear Current Booster to keep from burning the motor up at 8V when it can't run.
When you take a 12V motor, and feed it 8V, it does not have enough power to run the motor, so it sits in a stall condition, feeding current through only 1 coil winding, instead of cycling through all the windings as intended. A Linear Current Booster stores and manages the available power from the PV, and powers the motor in short bursts when there is low power, and full speed when conditions allow.

A charge controller and battery is more complicated and the battery needs water and replacing every year (under these conditions, the battery will wear very quickly).

Thanks for your reply. I mispoke when I used "limit the current". You stated the battery would wear very quickly under these condition, may I ask why would it wear any faster than in other applications. Regards,

reststop

[Mike90250]

The suggestion was for a small battery. Batteries have a long life when only used for about 20-30% of their capacity. Using a small battery, you would be going into deeper discharge of 50-80%, which shortens their life.

Unless you need to pump more hours, there is no reason to use batteries, as the recharge efficiencys, charger, and controls eat up more power than just running the pump off solar.

[hawaiianfishkee]

Mike,
I am trying to do the same thing but for a small garden stream.... i want to run a small 12v .5amp pump off of solar panel(s).. the panel i have is rated at 12v but max at 17v...with max .28amp < i suppose the panel wont run the pump due to lower amperage.. But, if i get two panels at 12v-17v= 24v-34v max with total of .56amp max< this should run the pump, but risk burning out...

*I believe that linear current boosters minimize voltage levels and maximize amount of amps(current)

in theory, will this setup work?

-2 solar 5w panels rated at 12v-17v(@.28) each = total of 24v-34v(.56)
-linear current booster or a voltage regulator(to stablize to 12v)
-12v(.5amp) water pump

[Mike90250]

Mike,
I am trying to do the same thing but for a small garden stream.... i want to run a small 12v .5amp pump off of solar panel(s).. the panel i have is rated at 12v but max at 17v...with max .28amp < i suppose the panel wont run the pump due to lower amperage.. But, if i get two panels at 12v-17v= 24v-34v max with total of .56amp max< this should run the pump, but risk burning out...

*I believe that linear current boosters minimize voltage levels and maximize amount of amps(current)

in theory, will this setup work?

-2 solar 5w panels rated at 12v-17v(@.28) each = total of 24v-34v(.56)
-linear current booster or a voltage regulator(to stablize to 12v)
-12v(.5amp) water pump

no. You need a 3rd panel added to the mix, as panels generally put out about 80%,
and the thin film 5 watt panels, seldom are. The should be wired in PARALLEL where amps add, not volts. Just the linear current booster, no regulator.