12V Battery on a 230V/50Hz Pump

[Teclics]

Hey guys,

This is my first time posting here because i want to start applying my theoretical knowledge of electromagnetism ( I have a MSc. in physics ). You would be surprised by how little actual electronics we actually get taught.
I plan on buying a pump for a pond and hooking it up to a battery (entire plan will probably be posted in the project section soonish). Now my question is: How do I hook it up? Do I need to buy and put an inverter in between and what is the efficiency of the conversion? Does the pump internally use a lower voltage DC current? If so, would it be better to hook up the battery more directly?

My apologies if these question sound stupid, it is because my electric knowledge is only theoretical and not practical. I would be happy to explain the laws of Maxwell if anyone is interested

Cheers! Teclics

 

[AnalogKid]

Many of the answers are under your control. If you buy a 12 V DC pump and use a 12 V DC battery, no conversion is necessary. If it is a 220 VAC pump, then you need an inverter. Figure 80% efficiency, so 20% of your battery power goes up in heat. Step 1, what are the water-moving requiements? Step 2, what pumps are available to you? Then the tradeoffs begin, battery size vs. run time vs. cost, etc.

ak

 

[Teclics]

Hey AnalogKid,

Thanks for the quick reply! Available pumps are all 220 VAC, but I assume (or guess) they run on lower voltage DC. Don't you think? Would it be possible to open up the pump and hack it such that the battery can be applied directly instead of going through an inverter twice?

Cheers,

Teclics

 

[Bluejets]

220vac pump is 220vac....no internal inverter as you claim.

As far as hacking into a fully sealed pump, not a good idea by any means.

 

[duke37]

There are plenty of 12V water pumps on ebay, both high and low pressure.

 

[Alec_t]

Available pumps are all 220 VAC, but I assume (or guess) they run on lower voltage DC.

Absolutely not.
Pond pumps for domestic use are designed for low voltage in the interests of safety. Mains voltage and water are not good companions. Surely Belgium has somewhere (a Garden Centre?) selling 12V pumps?

 

[BobK]

I have a pond and its pump runs on 120 VAC. No internal conversion to a lower voltage, which I know because I have disassembled a broken one.

Bob

 

[Minder]

It depends on the size of the pond!
For the larger ones, a mains pump with AC motor is often used and the motor itself is sealed and filled with dielectric (transformer) oil.
M.

 

[BobK]

Mine is 1300 gallons. The pump is 500W, and pumps 3500 GPH. It would take 41A at 12V, which is a bit much.

Bob

 

[Alec_t]

It depends on the size of the pond!

Yeah. Guess I was thinking of small ornamental ones .

 

[z0d]

Just wondering, if you use the 12V DC batt to power the 230VAC, wouldn't that drain your batt very quickly? Seems a bit counterproductive. But then again, I'm guessing you're just gonna use the pump for short periods of time.

A related question that I have wouldn't you need a step-up transformer as well? Or do inverters come with it.

 

[BobK]

An inverter generally takes a low DC voltage 12 to 48 and steps it up to line voltage 120 or 230.

Bob

 

[Kiwi]

Our goldfish pond has a low voltage 12vac pump. It came with a 230vac to 12vac transformer. Brand is Pondmaster.
Easy to install. Being low voltage it doesn't need the cable to be installed to meet safety regulations. Transformer is in the garage and twin core cable runs around fences to pond.

Why do you want to run your pump from a battery?

How are you going to recharge the battery?

You can buy 12vdc to 230vac inverters from automotive supply stores. We use them at work to run laptops in the field.
They come in two types; pure sine wave, and the cheaper modified sine wave. Some devices don't run well on the modified sine wave inverters.