Wiring my batteries *fizzle-spark-oops-help*

[RogueTwoRobots]

Ok, was wiring up my feather prototype last night, had drawn a diagram to make sure all the connections were right, connected all the wires together, put the link in.......and managed to short the battery connections. Checked my wiring and it all seemed to be right, and looking at my diagram I can see any obvious short (but that doesnt mean to say there isnt one) but I am wiring it up in a slightly unorthodox manner...

Basically, Ive got two 14.4V 1800mAh batteries as my power source; I want to run my drive at 14.4V and 3600 mAh (connecting the two batts in parallel) while the weapon (24V linear actuator) I want to run at 28.8V and 1800mAh for more oomph (connecting the batts in series)

Is it possible to take both a series and parallel connection off of two packs in the way above or does the short circuit in my system prove it wont work (hoping I wired it wrongly)

Ive wired up the actuator so far and powered the drive off one battery for the meantime (only at half the capacity that I want though), but as soon as I try to connect the other pack to the drive for more Ah, I start getting sparks.

Any advice or magical non-shorting circuits would be great

Thanks,
Jamie

[woody]

Is it possible to take both a series and parallel connection off of two packs in the way above or does the short circuit in my system prove it wont work (hoping I wired it wrongly)

Possibly.

A version of this setup could I think work.
http://www.teamonslaught.fsnet.co.uk/4_Switch_control.jpghttp://www.teamonslaught.fsnet.co.uk...ch_control.jpg

(Message edited by woody on September 12, 2007)

Edit (Kane): Fixed link

(Message edited by kane on September 12, 2007)

[woody]

Cheers Kane.

@Jamie ...Ive drawn a sketch that MIGHT work and sent it to your email addy.

Jamie..I hope you got my sketch ... but just in case you didnt Ill try a quick explanation.
You MUST have two seperate speed controls.
Youll need to run each motor / speedo from just ONE battery.
Youll need to connect the batteries in series ..... and take a center tap off for the supply to one side of each speed control.... the actuator could then be connected across the two batteries giving you your required 28.8v.

To be safe Id add in fuse of around 10-15 amps on all three battery connections....Id also consider a LARGE diode on one feed to the actuator ......just to be sure that there isnt any possibility of some sort of feed thru.

pic uploaded on my profile

There is a much simpler solution if your speed controllers can handle the 28.8 Volt packs and you use a transmitter like the spectrum that can alter the stick range, just set the stick range to 50% (measure the motor voltage just to be sure). This is infact what we do with big nipper, the weapon is on 36V and drive on 24V.

[RogueTwoRobots]

Hi guys, thanks for the replies

Woody: Ive been away from home (and more importantly, my computer ) since Wednesday and wont get back til Sunday (borrowing someone elses comp just now) so I wont be able to try the circuit on your profile til then but it looks a lot better (and a lot less complicated!) than the way I had it . Didnt get the diagram email but got your forum PM - will add you when Im back home.

Mark: My speedos are Electronizes that only go up to 24V, and cant currently afford a Spectrum so I cant go for that solution just yet but it is as you said a very simple option.

Many thanks
Jamie

[sam_t]

If the speedos are not opto-isolated the center tap method can short the second battery through the speedos signal lines, it should be pretty easy to spot if you do as the signal cable will probably melt. This is because all the earth connections (power and signal) are internaly connected.

[RogueTwoRobots]

Yeah the second battery ended up shorting when I wired it all up so Ive just left it for now as Im currently back at uni - when I get back to it though I think Ill replace the motors with 24V ones and run the whole thing at 28.8V, seems the simplest option for the meantime