[stevieg]

As above, i dont want anything complicated like varistream etc.
Just a shop bought (or E bay) type that fits in the wiring and turns the water on or off!!! At the moment i use crocodile clips and just attach them to the battery.
Thanks.

[Don Kee]

Go to maplins, for a couple of quid you can get an 'on, off' flick switch.
Put it on the positive wire between you battery and pump

(i'd probably put a fuse on the same wire as a just in case (if you haven't already))

http://www.maplin.co.uk/p/10a-toggle-switch-dpdt-momentary-on-off-on-n41kr

http://www.maplin.co.uk/c/components/switches/toggle-switches

[stevieg]

Thanks

[Ian Sheppard]

Whether you use a controller or not fitting a fuse is important

Why is fitting a fuse important

A fuse(s) is needed in any electrical system (AC or DC). These protection devices react to the amount of heat being produced by electricity passing through wires and/or components. They are used so as to protect wires and components from the extreme heat produced should there be an electrical overload or short circuit.

When a short or overload occurs, the amps being drawn spike and this increases the heat produced in the wiring and components. When this occurs, a fuse or circuit breaker reacts almost instantly to stop the flow of electricity in the circuit and thereby stopping heat production.

You should never exceed the fuse rating advised by the manufacturer. For a fuse to open in a fault condition almost instantly (a few hundred milliseconds ) it can require current of 2.2 to 3 times the rating of the fuse. We recommend 7.5 amp fuses so the actual current to open the fuse may be as high as 22.5 amps over rating the fuse is dangerous.

In very rare cases if current is only slightly above or close to the rating of the fuse for prolonged periods there is not sufficient heat or current to blow the fuse, in this case the heat can build up and cause the fuse to melt.

For example a 15 amp fuse will happily supply current up to 15 amps but will not blow. (to blow it could require current of up to 45 amps) The fuse will however gradually get hot over time in testing at Spring I have seen a 7.5 amp fuse heat to 62C and not blow

Without PROPERLY-SIZED FUSES, this quick break in the circuit would not be possible, and damage to components and even FIRE could result.

If you are having a problem with fuses "blowing" please know that these devices are doing their job! It is important that you NOT replace a fuse or breaker with a higher-rated one. Check the circuit for shorts or overloads.

 

    Damaged, rusted or worn connectors
    Damaged cable
    Bare cables touching
    Poor connection (example would be insulation not stripped back)

Why then place the fuse close to the battery?

To reduce the risk of over heating in either the cable or device in the event of an electrical fault. The shorter distance current can travel between the battery and fuse means that the amount of cable that may get overheated is reduced to a minimum. For Example: It is possible the the insulation on the red (positive) cable can become chaffed allowing the core or poorly installed cable to come into contact with the chassis creating a fault condition . Without a fuse fitted close to the battery the wire will heat to red hot, burn off all the insulation and potentially cause a fire. Fitting a fuse close to the battery protects the cable run plus pump.

[Spruce]

Whether you use a controller or not fitting a fuse is important

Why is fitting a fuse important

A fuse(s) is needed in any electrical system (AC or DC). These protection devices react to the amount of heat being produced by electricity passing through wires and/or components. They are used so as to protect wires and components from the extreme heat produced should there be an electrical overload or short circuit.

When a short or overload occurs, the amps being drawn spike and this increases the heat produced in the wiring and components. When this occurs, a fuse or circuit breaker reacts almost instantly to stop the flow of electricity in the circuit and thereby stopping heat production.

You should never exceed the fuse rating advised by the manufacturer. For a fuse to open in a fault condition almost instantly (a few hundred milliseconds ) it can require current of 2.2 to 3 times the rating of the fuse. We recommend 7.5 amp fuses so the actual current to open the fuse may be as high as 22.5 amps over rating the fuse is dangerous.

In very rare cases if current is only slightly above or close to the rating of the fuse for prolonged periods there is not sufficient heat or current to blow the fuse, in this case the heat can build up and cause the fuse to melt.

For example a 15 amp fuse will happily supply current up to 15 amps but will not blow. (to blow it could require current of up to 45 amps) The fuse will however gradually get hot over time in testing at Spring I have seen a 7.5 amp fuse heat to 62C and not blow

Without PROPERLY-SIZED FUSES, this quick break in the circuit would not be possible, and damage to components and even FIRE could result.

If you are having a problem with fuses "blowing" please know that these devices are doing their job! It is important that you NOT replace a fuse or breaker with a higher-rated one. Check the circuit for shorts or overloads.

 

    Damaged, rusted or worn connectors
    Damaged cable
    Bare cables touching
    Poor connection (example would be insulation not stripped back)

Why then place the fuse close to the battery?

To reduce the risk of over heating in either the cable or device in the event of an electrical fault. The shorter distance current can travel between the battery and fuse means that the amount of cable that may get overheated is reduced to a minimum. For Example: It is possible the the insulation on the red (positive) cable can become chaffed allowing the core or poorly installed cable to come into contact with the chassis creating a fault condition . Without a fuse fitted close to the battery the wire will heat to red hot, burn off all the insulation and potentially cause a fire. Fitting a fuse close to the battery protects the cable run plus pump.

Hi Ian

Thanks for this. I found this very interesting and informative and appreciate the time and trouble you went to with the experiment and posting the findings.

What I found most interesting was the current it takes to blow a 7.5amp fuse. I thought 10 amps would have done it every time TBH.

[Ian Sheppard]

TBH Until I started looking at this more closely I was unaware of the amount of current needed to take a fuse out almost instantly.
It really brings home why over rating a fuse is not just a bad idea but can be dangerous.

[Plankton]

Ian, could you maybe explain how I burnt my finger on the negative croc clip attached to the battery. Shurflo pump and an analogue controller with a 7.5 fuse. I've recently changed the setup but always wondered why the connection became so hot. Any ideas.

[soapsudtw]

If the croc was hot, then it's connection to the terminal was at best poor.
Current will heat up a connection if it cannot flow freely past it

[Ian Sheppard]

Ian, could you maybe explain how I burnt my finger on the negative croc clip attached to the battery. Shurflo pump and an analogue controller with a 7.5 fuse. I've recently changed the setup but always wondered why the connection became so hot. Any ideas.

Good question Alan. The reason the crocodile clip may get hot is down to resistance created in both the clip and the cable it is connected to.
While copper is a good conductor of electrical current ( has the second highest electrical conductivity of all metals (5.96 × 107 siemens/meter at 20 °C))  it is not 100% efficient. The copper can also act as a resister to current.

This small resistance factor means the current that does not conduct is turned into heat. In the same way as a mobile phone charger or Lap top power supply do.

A crocodile clip is also not forming as good a connection to the battery terminal as a a battery terminal clamp would.
This again creates some resistance at the clip which is turned into Heat.

The thinner the cable wire the greater the loss of current to heat so for example a 2mm cable will conduct better than 1mm and create less heat. Although the difference is not very much.
A greater impact would be worn cable and or connectors. These again increase resistance and create heat chaffed cable where the core is exposed can make this worse.

The faster the pump runs the more current is drawn. As current is conducted in higher amounts the greater the resistance and heat generated. An older pump may not be as efficient as it was, this slight inefficiency in the motor as the brushes wear do two things 1. The pump has to work a little harder drawing more current & 2. This can lead to more current being turned into heat.
Chances are at the end of the day a pump is pretty hot some of this heat will transfer back through the cable.

The battery terminal itself can also be a source of heat due to the connector and resistance outlined above.

My suggestion would be to consider terminal clamps that will improve the connection at the battery terminal, Plus have a quick check of all the cables and replace any that is looking a bit sorry for its self.

[Plankton]

Thanks for that Ian. Good info

[PoleKing]

As this has turned into a battery thread...

I heard that running 2 6 volt batteries in series (?) was better for power discharge?

Anyone (Ian?) know anything or researched it in depth?

I know the 6v's are more expensive but if they're worth it...

[Ian Sheppard]

To be honest I have not looked at the comparative discharge rates of two 6V against a 12V. In effect the battery is made up of a series of 2V cells so a 12V battery will have six cells and a 6V three.

The battery AH rating is the info we are looking at as the higher the AH rating the longer the battery will take to discharge to 10.5V. One of the benefits of a controller is that it reduces the pump speed to match the water flow require. Reducing the current draw will extend the discharge period of the battery.

http://www.springltd.co/node/139

[Spruce]

As this has turned into a battery thread...

I heard that running 2 6 volt batteries in series (?) was better for power discharge?

Anyone (Ian?) know anything or researched it in depth?

I know the 6v's are more expensive but if they're worth it...

I saw this last night.

https://www.youtube.com/watch?v=tGNMenyNqwU

[Steve foster]

Going back to the fuse. I found a 7.5a blew every now and then. A 10a worls fine.

[Spruce]

Going back to the fuse. I found a 7.5a blew every now and then. A 10a worls fine.

The latest digital Varistreams we have are fitted with 10 amp fuses where Spring recommend 7.5 amp for their controllers.

The Varistream analogue controller we still have in the one van also has a 10 amp fuse from what I can remember (the van isn't here to check) but I see the original instructions say its a 15 amp automotive style fuse.

I will check that in the morning if I remember.