electrical expertise please

[fred]

I want to buy a small 12v diesel transfer pump

I won't always have it close to a car to allow me use the car battery. So the question is could the Bosch 12v batteries used in their cordless equipment be used to drive this pump and if so for how long.

I hesitate to buy a small 12v lead acid battery as it would inevitably be discharged when I wanted to use it.

Or could I get a 240v to 12v transformer to drive it as access to 240v isn't a problem

Many thanks for all assistance

[Dave Plowman (News)]

Batteries are usually marked in amp.hours. Multiply that figure by the voltage to get watt.hours. Divide that figure by how many watts the pump takes to give a rough idea how long it would run for. You won't get that full amount, though.

If the pump says how many amps it takes, the calculation is easier.

If the pumps says 0.5 amp, and the battery is 2 amp.hr, the theoretical time would be 4 hours. But in practice, perhaps 3.

[Andy Burns]

160W / 12V = 13.3A

Assume (since you didn't mention capacity) a 4Ah battery, that gives you a theoretical maximum battery life of

4 x 60 / 13.3 = 18 minutes

but will be lower in practice.

[newshound]

Probably needs DC, not AC. Drawing about 13 amps. So you would need a fairly meaty transformer, but a medium sized car battery charger would be OK (except that these give around 14 volts on load). The standard 12 volt wall warts used for CCTV only give an amp or two.

Cordless power tools these days are commonly 10.6 or 14.4 volts rather than 12 volt. I think my 14.4's are about 1.5 amp-hour so that would give you about six minutes pumping. Mobility scooter batteries (about a third of the size of a small car battery) are typically 15 AH (so an hour of pumping).

[Roger Mills]

The link says it's 130 watt - which is over 13 amps at 12v. A typical

12v power tool battery has a capacity of 2 amp-hours - so would only power your pump for about 9 minutes, assuming that it could deliver 13 amps (which it may not be able to).

I know you said that you didn't want to buy a small battery - but how about something like this

which has plenty of uses other than just powering your pump? I always carry a similar in my car, but I do make sure I top up its charge every now and then.

If you want a mains power supply, your usual wall wart won't be anything like powerful enough. Something like this

may well do the job. You'd have to modify the connections on your pump, of course.

[Clive Arthur]

Loads of these, for example...

(Ebay no 181881169501)

Chose a 12V 240W (20A) one, why not, it's under a tenner. It needs connecting and putting in a safe place.

Cheers

[newshound]

Agreed, if mains really is not a problem and you feel competent to make a safe box for your environment (is it wet? the PSU may need some ventilation) then that is the cheapest and most reliable way to go.

[Peter Parry]

Problem I have found with many Chinese Switched Mode Power Supplies such as the one above is that they really dislike the high start up pulse of inductive loads such as a pump motor and immediately switch themselves off.

[Dave Plowman (News)]

Ebay usually had a fair selection of 13.8v power supplies designed to run car accessories (radios, etc) off mains.

[fred]

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Many thanks to all who contributed.

I have a diesel powered blow heater in my garage/workshop so when we are ha ving an oil delivery I get them to fill a barrel I have. I then have to tra nsfer from the barrel into a 20l container to allow me fill the heater. I'v e tried various hand pumps but all are too slow and messy and diesel is the dirtiest thing to deal with no matter how careful i am. Hopefully one of these 12v pumps will make it easier and cleaner. Time will tell.

[dennis]

The pump is 160W so about 16A which is a lot of current for a small battery. A 4AHr drill battery will last about 10 minutes if it doesn't overheat and melt first. You may need to cool it somehow.

You will need some good connectors too.

A 16A mains to 12V supply isn't cheap.

Do you need 2400l/hr or can you find a smaller one.

[tabbypurr]

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having an oil delivery I get them to fill a barrel I have. I then have to t ransfer from the barrel into a 20l container to allow me fill the heater. I 've tried various hand pumps but all are too slow and messy and diesel is t he dirtiest thing to deal with no matter how careful i am.

160W seems like real overkill for that. I also would have thought it not ha rd to make a simple PVC handpump that lifts a pint or 2 on each stroke.

NT

[dennis]

If its like the one I bought a few years ago they lie about the capacity. Mine had a 7ah SLA battery in it and it only weighed half of what other

7Ahr batteries did.

A 7Ahr sla battery is much cheaper.

[The Natural Philosopher]

best way to get 12V DC is a cae battery replacement PSU sold for e.g., CB radios in a fixed base unit

Dozens on ebay. I got a really good one for under £30 and there are often even cgheaper ones

[The Natural Philosopher]

Fat capacitor fed via a revrse diode with a restiosr across it will be slow to charge, and handle the switch on surge if the PSU is started a second before the pump.

Or use a thermistor in series with the pump

[Harry Bloomfield]

fred pretended :

Also, you might look at a pump as used on a diesel car, they are made for pumping diesel. Mine has two, one in the tank, a second in the engine bay. The engine bay pump is perfect for your needs, pipe in, pipe out and a 12v socket. There should be a selection available, in a car scrap yard.

[Dave Plowman (News)]

Remember there are different types of pump. Your engine bay one is likely pressure fed from the tank one - and may not 'lift' fuel any distance.

[Brian Gaff]

You need to know its starting current at 12 volts really to decide this. Brian

[spuorgelgoog]

Are the Bosch batteries just batteries or do they incorporate circuitry whi ch matches them to a Bosch drill in some way, which means they wouldn't be just a simple voltage source (like some computer power supplies which negot iate the power required/available)?

Or what about the small pumps you can get that attach to a drill chuck?

(expensive) (not expensive)

Or fit a tap, put the barrel on a platform and allow gravity to do the job.

Owain

[Bill Wright]

Why? Even if you don't use it for months it will still be 90% OK. After use put it on slow charge for a few days. Then put it on the shelf. I have two 15Ah deep discharge batteries that are used maybe once or twice a year and they have been fine.

Bill