One for the sparks :)

[skotl]

Thanks for the info, two more questions though. Would a diode fitted on each battery live stop one robbing charge from another and exactly what knife switch do I need ?

Bob

It would, but at the expense of nicking some forward voltage (which probably isn't important) and the (more significant!) expense of needing two at ~400A which are around £35 to £40 a go.

And, as rtb states, you'll also need fuses.

 

[skotl]

Doesn't do the parallel bit, but a simple switch will give you 12/24V

View attachment 131116

This is the neatest, and least explodey, solution so far IMHO.

 

[Robotstar5]

It would, but at the expense of nicking some forward voltage (which probably isn't important) and the (more significant!) expense of needing two at ~400A which are around £35 to £40 a go.

And, as rtb states, you'll also need fuses.

400A!, that must be some trailer board he's testing

 

[skotl]

400A!, that must be some trailer board he's testing

I might have misread, but I thought 8ob was talking about using car batteries? Hence the 400A.

If it's a pair of duracells, then obviously far less

 

[armalites]

Just build it as 24v and use on of these

https://www.lightinthebox.com/xinco...ply-transformer-converter-black_p2567580.html
https://www.lightinthebox.com/xinco...ply-transformer-converter-black_p2567588.html

 

[8ob]

Just to straighten a few points out.

Needs to be switchable 12/24 volts, it will have two small motorcycle/alarm/mower lead acid batteries, it needs to be charge, it needs to be 100% mobile and not rely on a power source and all circuits will be protected by fuses. Would not want any less battery capacity.

The panel and chasngeover switch on the booster pack looks ideal with its charge display, probably mega dosh from ring because other than the batteries and case I cant see where the money is in these units https://www.pfjones.co.uk/ring-rpmm3000-booster-power-pack-jump-starter.html



The reason I want the 24v option is for trailers like the one I am refurbing atm, cant get it on the bench, having the lorry hooked up with the ignition on and the buzzer howling is a ballache and you cant easily test brake/indicator lights without leaping in and out of the cab, also need an oppo to check brakelights or have to wedge brake pedal down. The box of tricks and a long trailer cable makes all this a dawdle because all the switching/checking can be done from the back.








Back to the original question How many poles on a rotary switch are needed to follow @skotl diagram on post#7 ?



Bob

 

[brightspark]

dawdle thought u wanted faster to make it a doddle

 

[ajlelectronics]

Build it as a 24V and just switch in a 12V regulator as required, simple efficient and safe. You just short out the regulator with your switch.

 

[8ob]

dawdle thought u wanted faster to make it a doddle

Further poof that a smellchecker can be your worst enema

Bob

 

[rtbcomp]

Build it as a 24V and just switch in a 12V regulator as required, simple efficient and safe. You just short out the regulator with your switch.

Need to be careful, you could put 24v on the output of the regulator, if it's got a blocking diode you should be OK.

 

[skotl]

Build it as a 24V and just switch in a 12V regulator as required, simple efficient and safe. You just short out the regulator with your switch.

I like that idea - much simpler than the earlier versions.

How about using a regulator like this one with a Single Pole / Double Throw (SPDT) switch like this?

 

[500e]

Beat me to it skotl Had one working like that 20 year ago. Modern 24\12 droppers have shot circuit circuit, reverse polarity & overload protection & life time & a warranty From alfatronx & Les Wallen aerials the other thing is Quiescent current draw is aprox 15mA
You could switch the dropper as well with a 2 pole 2 way switch so there was no current draw if left you switched to 24 volt .
We always fused just to be safe
The warranty from both are rock solid, over 30 years with Alfa\t never had one refused not dealt with Warren for so long but same.
We had over 500 units running at one time & I can only remember 3\4 fail in total
Bob a switch protector to guard against inadvertent switching + beacon lamps to show which supply you are using

 

[8ob]

A little bit of a result today , I phoned up ring the other day and asked about a price for the complete front panel of the above booster box and they came back with a price of £25 all in inc p+p. All the leccy gubbins is on this panel so it means I get my 12/24 switchover, charge indicator, cig socket and I can use my existing charger. Thanks for all the input chaps.

Chuffed

Bob

 

[8ob]

It turned up today @pdg and its the complete front panel full of leccy giblets,I suppose I will have to open mine up to see how its wired but I think even I could manage that one. Its a bargain at £25 all in and thanks to @bigfellayork for suggesting it