Require Schematic-Charge Batts in Parallel run in Series

[Gerry OGrady]

11 September 2003 6:52 PM

I have three identical 12VDC batteries that I would like to use for 40 amp
36 Volt DC motor testing. I need a schematic on how to hookup the batteries
in series (36V) for testing the motors and when the batteries get discharged
I can activate a switch to connect the batteries in parallel (12V) for
charging with a 12V battery charger. I currently swap the connections
manually which is time consuming at best. I can envision using a multi pole
high power relay to accomplish this. I just can't get my brain around the
actual wiring.I would appreciate a schematic or a link to any website that
illustrates the solution.

Cheers ...Gerry

[email protected]

 

[Ian Stirling]

11 September 2003 6:52 PM

I have three identical 12VDC batteries that I would like to use for 40 amp
36 Volt DC motor testing. I need a schematic on how to hookup the batteries
in series (36V) for testing the motors and when the batteries get discharged
I can activate a switch to connect the batteries in parallel (12V) for
charging with a 12V battery charger. I currently swap the connections
manually which is time consuming at best. I can envision using a multi pole
high power relay to accomplish this. I just can't get my brain around the
actual wiring.I would appreciate a schematic or a link to any website that
illustrates the solution.

A six pole double throw relay could be used.
Connect the moving contacts to each of the battery terminals.
Now, you have two "copies" of the battery terminals, which you can pick
between using relay.
Wire up one set in series, and one in parallel.
You will notice that the wiring actually only needs 5 poles.

However, you cannot safely use two or three relays instead, and assume
they will switch as one.

 

[clare @ snyder.on .ca]

A six pole double throw relay could be used.
Connect the moving contacts to each of the battery terminals.
Now, you have two "copies" of the battery terminals, which you can pick
between using relay.
Wire up one set in series, and one in parallel.
You will notice that the wiring actually only needs 5 poles.

However, you cannot safely use two or three relays instead, and assume
they will switch as one.

No, but if you have two series strings you want to connect either in
series or parallel, it can be done with ONE SPST relay and a diode. -
or is it two diodes.Can't find the schematic from my old Electric Fiat
- had 2 24 volt strings that were paralled for charging and low
speed, and switched to series for high speed. The diodes were BIG.

IIRC there was a diode between the pos of one string and the neg of
the second string to connect them in series. There was a second diode
between the negatives that was back biased by the first one, By
connecting the two positives together, the "series" diode was back
biased and shut off, while the "shunt" diode became forward biased,
going into conduction. The charger energized the contactor, putting
the batteries in parallel to charge.

Strange setup I'll admit - but it WORKED.