Any preassembled relay set ?

[Externet]

Hi.
Is there in the market an assembly of relays to put batteries in parallel/series combinations ?

Like having the device connected to 4 automobile 12V lead-acid batteries and with a selector that in
position 1 will put them all in parallel for 12V output;
position 2 will put two in parallel and 2 in series for a 24V output, and
position 3 will put them in series for a 48V output.

Can be done with a several relays and some thinking, but curious if anyone knows if such is available assembled as a unit.

Miguel

[haklesup]

I imagine that the applications for such a circuit would be limited (I can't think of any standard apps off hand) and demand for such a thing would be miniscule (unless accompanying a killer app). I doubt anyone would have such a device.

However, designing and making such a thing should be pretty easy using any vector board or bare PCB material as a substrate to mount the relays and hand wiring them.

However, depending on the current load, you may need some very hefty relays and if you plan to switch the load while hot, you may need even larger ones than DC current would imply. The relays absolutely must break before make but if the load is high current there may be an arc of sufficient size to create conduction between all contacts for a moment. Care must be taken so that no relay hosts more than one hot terminal (+ or - of any battery) to avoid shorting a battery and creating a smoke and fire show. Finally I recommend fuses, fusable links or circuit breakers whenever powering with car batteries on each of the + posts at least, maybe more.

[Externet]

Thanks, haklesup.

Yes, would be tens of Amperes current, and never seen such relay assembly available.

Once I built an electric motorcycle with a single 12V battery/motor in one mini-bike of the seventies with its BriggsStratton engine removed and worked very well with a plain on/off switch !. Was wondering to build another with 4 batteries and 3 speed simple selector, no variable speed control.

Once I made the schematic of the relays that would be needed for the task and was not simple, actually a mind twister.
Miguel

[jwax]

Look into solid state motor controllers. They have become way cheap with the high performance MOSFET's. Infinite speed control for not too much cost.
Here's one:
http://curtisinstruments.com/index.cfm? ... 1&siteID=1

[fripster]

hi,

Older Mercedes 508D transporters have a relay that normally (not activated) puts two 12V car batteries parallel. When activated, it puts them in series (in order to be able to start the engine, which has a 24VDC starter motor).
These are VERY heavy duty units, as the starter engine current must pass through it.

just my two cents....

fripster