Pump / battery and fuse advice

[Mostly Clueless]

Hi, mostly clueless by name and nature I'm afraid.

I need to buy a pump that I can use to fill a motorhome water tank from a water carrier. In essence I will need to to shift about 60 litres of water at a time.

I've found a 12v 6A pump that moves around 6l a minute - so it would need approx 10 mins of run time. So could I get by with a 12v 3A SLA battery? When I connect them up would I need a fuse or is it just as simple as connecting the battery direct to the pump with crocodile clips?

Thanks for taking the time to read this

 

[Squid]

Why not a mains operated pump?

 

[MDJ]

Why not a mains operated pump?

I agree, you could plug it into an inverter which motor homes have

 

[MDJ]

Hi, mostly clueless by name and nature I'm afraid.

Yup

 

[Mostly Clueless]

It's really about the location of the electric points relative to the inlet for the water tank plus I can't guarantee that I'll be connected to a hook up point. Plus I've now piqued my interest .....

 

[MDJ]

It's really about the location of the electric points relative to the inlet for the water tank plus I can't guarantee that I'll be connected to a hook up point. Plus I've now piqued my interest .....

I understand what you are trying to do because I am a caravanner and see you guys on site struggling all the time, you could just use a large hose pipe and connect to a tap, it is all about parking near the water lol, otherwise try the local caravan dealer mate.

 

[buzzlightyear]

what is wrong carrying the water in a bucket then .

 

[MDJ]

what is wrong carrying the water in a bucket then .

You don't carry 60 Ltrs lol, you use an aqua roll, but with Motor homes the set up is a bit different, as are Motor home users chuckle.

 

[buzzlightyear]

You don't carry 60 Ltrs lol, you use an aqua roll, but with Motor homes the set up is a bit different, as are Motor home users chuckle.

is that one of them barrels thingy's . you pull like donkey .LOL .

 

[MDJ]

is that one of them barrels thingy's . you pull like donkey .LOL .

yep, usually only 40 Ltrs though, some are 50 Ltrs

 

[Squid]

I am a caravaner.

That explains a lot.............

 

[Lucien Nunes]

If your pump really needs 6A, then I would go for a larger battery. Lead acids perform poorly under rapid discharge, the capacity is given at the 20-hour rate i.e. a 3Ah block will only give you 3Ah back if discharged at 0.15A for 20 hours. I would use at least a 7Ah, they are standard for alarm systems and very cheap to buy. Yes, add a fuse, e.g. an inline blade fuseholder with a 10A fuse. Even a small battery can burn things up if short-circuited.

But, I wonder at the 6A requirement. If this is a diaphragm pressure pump, as built into RVs etc to supply the taps, then it won't take anything like full current when it's only working against a few feet of head, instead of the 30-60 feet that these pumps will deliver. The flow rate is approximately proportional to voltage supplied, and the current taken is approximately proportional to total head.

If it is a centrifugal pump, then the current depends more on flow rate than head, but there's not such an obvious relationship. But I'd expect to be pumping more like 30 litres per minute against about 3 feet, to need 6A.

 

[Mostly Clueless]

Thank you Lucien for such a complete reply. It is indeed a diaphragm pump and I have no idea what kind of spec I need to be honest - I just saw this one one e-bay and it cost approx £10 so I thought that I could create a pump and battery combo for about £20 all in. You're quite right in that the head is only a few feet - say 1m max. Would you suggest I look for a pump with a lower amperage?