Series paralell switching battery pack

moostrodamus

100 W
Joined
Aug 30, 2009
Messages
173
Location
Toronto
Howdy,

I found "instructable" on how to hook 2 motors up with a DPDT switch so you could run them either in series or parallel.

http://www.instructables.com/id/SIMPLE-ParallelSeries-Select-Switch/step2/Wiring-the-switch/

So I used that and came up with this to hook up two 36v batteries to a DPDT switch to run either in series or parallel.

dpdt.jpg

My understanding is top position would be Parallel, middle position off (use for charging?) and bottom position series.

Should this work?
Can i assume i should buy a 30 amp switch as i am using a 30 amp controller?

Lurning is hard. Any comments/ corrections appreciated,

Moo
 
Normally DPDT switches have the two centre pins as common and they either connect to the two upper or two lower pins - only some switches have a centre off position, so you would need to check.

A controller rated at 30A may actually put out much higher peak currents for short duration so you should use a switch rated for a minimum of at least double the controller current. You would prabably need to use a battery isolation switch, but they are quite large. You can buy these from boating/4WD/caravan shops. The other option is to use a smaller switch to activate a DPDT relay to switch the hgh currents.

Depending on the battery chemistry you also might want to install some diodes per this thread http://endless-sphere.com/forums/viewtopic.php?f=2&t=14744
 
thanks for the link to that thread, lots of great info.

Thanks

Moo
 
I am looking at this also, only I want to be able to run 100amps through the switch.

An important consideration is that, as you have to throw 2 switches to change between S and P, one MUST NOT close before the other one is open, or POOF!

So you need either a mechanical connected switch DPDT (Double Pole Double Throw), or 2 stage switching, eg a three position micro switch driving 2 relays, Position One=Series, Position 2= Break Series, Position 3=Parallel

Here are some DPDT Relays I found

100, 200, and 300Amp DPDT Relays. Note these are huge, heavy and draw a bit of current to keep them switched.

http://www.geindustrial.com/products/specs/EV100Contactors.pdf

These would suit you, 30amp continuous, also 50amp available.
prod153_small.jpg

http://www.rvpowerhouse.com/category.php?cat=10

Another option, which has failed me before due to them not switching at the same time is to use automotive headlamp relays.
You can get up to 150A ones. Get them from 4x4 accessory stores.

5-pin-automotive-relay.jpg

5-pin-12V-automotive-relay.jpg

http://www.pickercomponents.com/Data_Sheets/PC7150_Data_Sheet.pdf

I am planning to try again with these, but this time switch them one at a time, as below

series%20parallel.jpg


So, you could have a small toggle switch on your bars, with series, disconnect and parallel positions.
P1010107.gif


You would also need a 12v dc converter to drive the relays.

I have yet to see a high current(100A) manual DPDT switch. Any one know of one?
 
The lovely NKK DPDT switch can be bought for around $53 at other online dealers.

http://www.alliedelec.com/search/productdetail.aspx?SKU=8700593
and
http://parts.digikey.com/1/parts/980869-switch-toggle-dpdt-50a-sldr-5pcs-s732-ro.html
and
http://www.mouser.com/ProductDetail/NKK-Switches/S732-RO/?qs=93uzuGORGqeoyvV5VttaPw%3d%3d

There are also much less expensive DPDT or 4PDT center off switches that allow you to switch between series and parallel on the *Bay.
http://cgi.ebay.com/DPDT-Toggle-20-amp-Switch-Center-Off-ON-OFF-ON-K203-/190425882010?pt=Model_RR_Trains#ht_1312wt_886
http://cgi.ebay.com/4PDT-Toggle-Switch-Center-Off-ON-OFF-ON-20-Amp-K403-/190427875108?pt=Model_RR_Trains#ht_1254wt_886

I am currently installing a 4PDT center off switch in my Bosch Fat Pack setup which consists of 8 BPFs that can be switched to 8 parallel packs 8P (37V) to charge or 2S4P (74V) to run. The center off allows me to switch without worrying about shorting or overloading anything. I'm trying to implement a Cell-log battery monitor as well.

http://endless-sphere.com/forums/viewtopic.php?f=3&t=20000

Doctorbass has used this configuration with his Sony/Konion cells for many years without trouble. Of course, he's working on something more powerful and advanced now!
http://endless-sphere.com/forums/viewtopic.php?f=14&t=7240

Ambrose
 
Awesome resources guys! Thanks!

Moo
 
I may have missed somthing but...

I do this now on my geared setups between 10S/20S and 12S/24S and the first thing I didn't note in your explaination was the controller you will use. It will need to be able to either work with the given voltage range (Tip122 transistor mod) or you will need 2 different voltage divider bridges to the LM317T voltage regulator to handle the different voltages - these will need to be switched while the pack is in disconnect state - the actual state model should be:

1.) Interrupt throttle return (relay)
2.) Remove Parallel Connection between packs - breaking the connection so you have 2 packs
3.) power the relay needed to switch from the 36v divider network to the 72v divider network
4.) power the relays needed to engage in series
5.) re-engage the throttle return.

This will ensure smooth and safe switching between the 2 possible voltage inputs :)

Hope this helps a bit !

-Mike
 
Hay all,
Check out these heavy duty DPTD toggle switches 30A Amp rated for $22

http://www.mouser.com/Electromechanical/Switches/Toggle-Switches/_/N-5g2j?P=1yzshdm&Keyword=dpdt+toggle&Ns=Pricing|0&FS=True

Check out the Ebike my brother and I are building

http://www.youtube.com/watch?v=lByACVoDoyw

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if I use 2 battery packs of 48V 12Ah(96V in series and 24Ah in parallel) how many Amps should be the dpdt switch?
 
amberwolf said:
How many amps is your controller going to pull from the pack(s)? That's how many amps the switch has to take.

40-50 Amps almost..
 
Subscribing. This is extremely useful information. I think I'll copy it to the reference area.
 
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