[GribinIsaf]

We have a small (500 litre) pond in one of the polytunnels - for aesthetic rather than productive reasons.

Two fish, outgrowing our cold water indoor aquarium, have moved into this pond.

They do need a bit of a boost to the oxygen levels in the water and I have put in a little pump that comes with its own solar panel.

What I would really like to do is hook up an aerator to a 12v solar charged battery system I have down there so as to have more control over its running.

Nowhere can I find a 12v pump to do this, all the self contained solar ones seem to run at different voltages - the one I have got is labelled 6-9v.  The pump needs to be quiet and capable of running continuously.

So I am posting here to see if anyone knows of a solution to this?

Many thanks

[pgkevet]

I used to have a small pond in my conservatory back in the south london days. I dealt with the problem bu using the pond water for watering while topping it up by hose.Otherwise consider an inverter and a mains powered option... bound to be more variety. Or add a pump and waterfeature to mix it up.

[GribinIsaf]

I used to have a small pond in my conservatory back in the south london days. I dealt with the problem bu using the pond water for watering while topping it up by hose.Otherwise consider an inverter and a mains powered option... bound to be more variety. Or add a pump and waterfeature to mix it up.

Thanks - don't what to agigate water too much with fountain etc as it contains lilies which don't like that sort of thing.

Might have to resort to inverter as you say

[mab]

Don't know how 'electrically/electronically' savvy you are but i would look to directly drop the volts from the battery to the 6 - 9 volt range of the pump, as an inverter/mains psu system will take a disproportionately large amount of energy from the battery. Do you know/ can you measure the current draw of the pump you have and what actual voltage it runs at?


Another option might be to use a small 12v water pump - which are readily available - to create a small waterfall/fountain and aerate the water that way.

[arobwk]

I've been looking at 12v water pumps lately & I'm reasonably confident in saying that air compressors up to 12v appeared (unnecessarily) in my various search results, but skipped over w/o much attention as not what was looking for - probably ebay search results.

[GribinIsaf]

Don't know how 'electrically/electronically' savvy you are but i would look to directly drop the volts from the battery to the 6 - 9 volt range of the pump, as an inverter/mains psu system will take a disproportionately large amount of energy from the battery. Do you know/ can you measure the current draw of the pump you have and what actual voltage it runs at?

Yes - I was thinking stepping down voltage more efficient than inverter.
I will measure current drawn and actual voltage tomorrow.

Do you mean something like this:
https://www.amazon.co.uk/Voltage-Converter-Transformer-Regulator-Regulated/dp/B01KFHPX68/ref=sr_1_4?ie=UTF8&qid=1531601072

[mab]

Don't know how 'electrically/electronically' savvy you are but i would look to directly drop the volts from the battery to the 6 - 9 volt range of the pump, as an inverter/mains psu system will take a disproportionately large amount of energy from the battery. Do you know/ can you measure the current draw of the pump you have and what actual voltage it runs at?

Yes - I was thinking stepping down voltage more efficient than inverter.
I will measure current drawn and actual voltage tomorrow.

Do you mean something like this:
https://www.amazon.co.uk/Voltage-Converter-Transformer-Regulator-Regulated/dp/B01KFHPX68/ref=sr_1_4?ie=UTF8&qid=1531601072

aye something like that, provided it has enough current capacity above the continuous draw of the pump and current limiting (that one does indeed have current limiting). The only issue with something like that is that there's a lot of variability in the quality/robustness of these dc-dc convertors - hence making sure you're not running it too close to the max current rating.
failing that, a much simpler (but less efficient) way of doing it would be to put a series resistor in line with the pump to drop the excess voltage. but my 1st choice would be the dc-dc converter.

[GribinIsaf]

Don't know how 'electrically/electronically' savvy you are but i would look to directly drop the volts from the battery to the 6 - 9 volt range of the pump, as an inverter/mains psu system will take a disproportionately large amount of energy from the battery. Do you know/ can you measure the current draw of the pump you have and what actual voltage it runs at?

Yes - I was thinking stepping down voltage more efficient than inverter.
I will measure current drawn and actual voltage tomorrow.

Do you mean something like this:
https://www.amazon.co.uk/Voltage-Converter-Transformer-Regulator-Regulated/dp/B01KFHPX68/ref=sr_1_4?ie=UTF8&qid=1531601072

aye something like that, provided it has enough current capacity above the continuous draw of the pump and current limiting (that one does indeed have current limiting). The only issue with something like that is that there's a lot of variability in the quality/robustness of these dc-dc convertors - hence making sure you're not running it too close to the max current rating.
failing that, a much simpler (but less efficient) way of doing it would be to put a series resistor in line with the pump to drop the excess voltage. but my 1st choice would be the dc-dc converter.

OK - I can do basic wiring but don't know much about electronics - am willing to learn!

The pump is directly connected to its own little dedicated solar panel so obviously its rate of flow varies with energy being generated.  When I measured it today I was getting a voltage of 5-6v across the input and the current round the circuit was 133mA.  On the pump it is rated 6-9v.

So, if I get one of the reducers as per link above am I doing something stupid?

many thanks

[mab]

Not at all, it should work on that reducer I would think - but if the pump works well on 5-6v I might consider getting a reducer set to 6ish volts output simply because the pump may run quieter/live longer at 6v than at 9v.
The simple resistor alternative would be to put a  47 Ohm 1watt resistor in series with the pump. This would drop ~6.25v at 133mA leaving about 6 volts across the pump. This method is a bit more rough & ready, and less efficient, but is perhaps more robust because it's simple - although I'm not sure where you can buy a single resistor nowadays.

[GribinIsaf]

Not at all, it should work on that reducer I would think - but if the pump works well on 5-6v I might consider getting a reducer set to 6ish volts output simply because the pump may run quieter/live longer at 6v than at 9v.
The simple resistor alternative would be to put a  47 Ohm 1watt resistor in series with the pump. This would drop ~6.25v at 133mA leaving about 6 volts across the pump. This method is a bit more rough & ready, and less efficient, but is perhaps more robust because it's simple - although I'm not sure where you can buy a single resistor nowadays.

Thanks for all your help - think I can get it do what I what after reading it.  Have ordered a suitable reducer.

[cloddopper]

Not at all, it should work on that reducer I would think - but if the pump works well on 5-6v I might consider getting a reducer set to 6ish volts output simply because the pump may run quieter/live longer at 6v than at 9v.
The simple resistor alternative would be to put a  47 Ohm 1watt resistor in series with the pump. This would drop ~6.25v at 133mA leaving about 6 volts across the pump. This method is a bit more rough & ready, and less efficient, but is perhaps more robust because it's simple - although I'm not sure where you can buy a single resistor nowadays.

 Cheap resistors ...  volts equal current x resistance  , volts over current equals resistance & finally volts over resistance equals  current . 12 volt Car head light bulbs are 50 watt , stop / tail 6,21 watt . Turn light bulbs  21 watt , number plate 5 watt , caravan sidelight bulbs are often 10 watt
 Most 12 volt bulbs will run continousily for years if run at less than 12 volts .