• Howdy! we're looking for donations to finish custom knowledgebase software for this forum. Please see our Funding drive thread

My series parralel changer

Tench

100 kW
Joined
Jul 13, 2010
Messages
1,069
Location
Derby UK
Several people have asked about how i did this, its no secret i just have not got around to doing an explanation but as today is a national holiday in the UK and it is raining i have found the time.
The system is made of 6 6s zippy 8ah packs, these are permanently parralelled at cell level into 3 pairs of 2 packs, that is the main power leads and the balance port leads are permanently connected.
The change over device has 2 plugs either of which can be plugged into the socket on the bike, one of these plugs is to ride the bike and connects the 3 parralelled pairs in series and connects them to the controller so the bike is running on a 18s2p pack, the other plug is on the end of the charger cable and connects the 3 pairs in parrlel as a 6s6p pack so that it can be charged by my 6s 306b icharger.
The balance leads from the 3 permanently parralelled pairs are all fed into a 25 pin d-sub connecter in the bike mounted socket, the individual wires are arranged as folows, pin 1,2 and 3 are the first wire from each pair, pins 4,5 and 6 are the second wire from each pair etc untill all the 7 wires from each balance cable is connected into the d-sub, this does leave 4 spare pins which could be used for a temp sensor in the pack so the charger can monitor the pack temps during charging.
The other part of the d-sub is on the end of the charger lead with pins 1,2 and 3 connected together terminating in a single wire, so are pins 4,5 and 6 etc, this results in 7 wires which go into the 6s balance port on the charger.
When the Bike run plug is removed the 18s2p pack is broken down into 3 6s2p groups and isolated from the controller, the charge plug connects these up as a 6s6p pack and connects the balance wires all together resulting in 6x 6p cell strings, the icharger can display the individual 6p cell string voltages, on initial connection of the charger any out of balance readings would indicate a problematic cell which would require the pack to be broken down further to identify the rogue cell, this has never happened, all the cells have remained perfectly balanced, probably helped by balance charging every time i charge.

I dont know how people create those fancy schematic diagrams so please excuse my drawn ones, if some one wants to reproduce these nice and fancy go ahead!

The balance lead loom and connectors;
IMAG0092.jpg


The pack assembled on the bench;
P1000070.jpg


This is a drawing of how the balance leads are connected;
P1000173.jpg


The socket on the bike;
P1000089.jpg


The run plug, this has the bridges between the connectors arranged as shown by the dotted lines in the drawing below.
P1000094.jpg

P1000171.jpg


The charging plug;
P1000095.jpg


I am sure my description will be lacking in some way so if you have any queries ask away,

Also, please get a good grasp and understanding of the principles involved here before you attempt to do something like this, the consequences of a wrong connection could be catastrophic!! Expensive, dangerous or both!!


Simon.
 
Thanks a million! Very nice explanation and very inspirational!
 
Tench,

A massive fan of the skills. Love the simplicity of this idea and like that it can be made more or less parallel. I do my 18s2p pack in to 9s2p halves but I went the route of a hyperion 1420i (i wanted the chance later on to buy some 4s packs so supplement my 3s subpacks to get a 14s/(28s in the distant future) pack running. I went the route of 3s packs cause the lipo lottery gives you more tickets this way if that makes sense. Thanks for your bank holiday drawings they were perfect to bring me up to speed on the parallel/series connection idea.

regards Andy
 
What a neat and elegant solution, a lot of thought to make it really simple to use, stunning bit of work
 
Yea I am impressed. Tech you seem to be one of those people who if they do it they do it right.

Love reading and looking at your results.
 
Looking closely, the only one thing I would say is the size of the power leads.
Looks like the loom that goes to the back of the block, is made of thinner wire than the wire coming out of the packs. i would have used a thicker gauge from teh T-piece to the block,and on to the controller
 
NeilP said:
Looking closely, the only one thing I would say is the size of the power leads.
Looks like the loom that goes to the back of the block, is made of thinner wire than the wire coming out of the packs. i would have used a thicker gauge from teh T-piece to the block,and on to the controller
Hi Neil, all the cable is actually the same gauge, it maybe the fact that some of those cables are closer to the camera lens and the single point of view lacks perspective that leads the eye to believe they are different sizes (useless photographer :roll: )
 
OK.

Still maybe be worth making those main wires up in 8 gauge, assuming t ewires from teh packs are I believe 10 gauge..go up a gauge where the currents from two packs combine. My 20s 4p pack is all made with 10 gauge too, the next build will go up a gauge where the packs are paralled
 
How did you do the connections inside the white plastic pieces? Did you cut them open then glue them back together?
 
RPM said:
How did you do the connections inside the white plastic pieces? Did you cut them open then glue them back together?

I dont think so, he drilled out the blocks from the side to slide the bars in, and bolted the bullets to them.

Speaking of which, how exactly do you bolt the bullet connectors on?
 
sn0wchyld said:
RPM said:
How did you do the connections inside the white plastic pieces? Did you cut them open then glue them back together?

I dont think so, he drilled out the blocks from the side to slide the bars in, and bolted the bullets to them.

Speaking of which, how exactly do you bolt the bullet connectors on?

Thats right, the connection bars where fed in through the side holes and bolted to the bullets, i used these bullets as they had sufficient wall thickness to tap them M5 where the cable would normally be soldered in;

http://www.ebay.co.uk/itm/5x-6-5mm-Gold-Bullet-Connector-plug-RC-battery-LIPO-UK-SELLER-A-331-/320845673707?pt=UK_ToysGames_RadioControlled_JN&hash=item4ab3e474eb
 
Tench said:
sn0wchyld said:
RPM said:
How did you do the connections inside the white plastic pieces? Did you cut them open then glue them back together?

I dont think so, he drilled out the blocks from the side to slide the bars in, and bolted the bullets to them.

Speaking of which, how exactly do you bolt the bullet connectors on?

Thats right, the connection bars where fed in through the side holes and bolted to the bullets, i used these bullets as they had sufficient wall thickness to tap them M5 where the cable would normally be soldered in;

http://www.ebay.co.uk/itm/5x-6-5mm-Gold-Bullet-Connector-plug-RC-battery-LIPO-UK-SELLER-A-331-/320845673707?pt=UK_ToysGames_RadioControlled_JN&hash=item4ab3e474eb


holly balls mate you tapped the bullets?!?! that's something I'd never thought of! how good is the connection though/any chance of them working loose? or did you fill them with some conductive paste or something before screwing 'em in?
 
sn0wchyld said:
holly balls mate you tapped the bullets?!?! that's something I'd never thought of! how good is the connection though/any chance of them working loose? or did you fill them with some conductive paste or something before screwing 'em in?

I had to make a clamp to hold the bullets from spinning so i could tighten the bolts enough, the clamp also had to fit inside the female bullets so the clamp didnt colapse them. i also had to machine the bolts to exactly the right length and reduce the bolt head dia, took more than a few hours on the lathe to get all the components ready for assembly!
 
Tench that's a very nice way to overcome the mess of wires I have in my 18s3p pack that I have to split to 6s packs for charging.

I will have to re-read this a few times to completely get it then I am off to source the bits.
Thanks for the excellent explanation. :D :D
 
Question Tench,
When all the balance leads come together for charging, has the out of balance at cell level between batteries been a problem ?
E.g. does battery 1 cell 1, being different from battery 3 cell 1 cause any arcing on insertion of the dsub connector.
Considering this as i have the same zippy pack build happening, but using a switch instead of plug & socket solution
http://endless-sphere.com/forums/viewtopic.php?f=14&t=40875, tag strip :oops: HK stuffing me around.
The next job was issues with balance leads, or if it was needed if medic's or similar were hanging off each 2P group.
 
Very nice setup, i understand how you did this parallel wire
IMAG0092.jpg

But i do not understand how you did the parallel wire from the charger
P1000095.jpg
 
megacycle said:
Question Tench,
When all the balance leads come together for charging, has the out of balance at cell level between batteries been a problem ?
E.g. does battery 1 cell 1, being different from battery 3 cell 1 cause any arcing on insertion of the dsub connector.
Considering this as i have the same zippy pack build happening, but using a switch instead of plug & socket solution
http://endless-sphere.com/forums/viewtopic.php?f=14&t=40875, tag strip :oops: HK stuffing me around.
The next job was issues with balance leads, or if it was needed if medic's or similar were hanging off each 2P group.
I have never noticed any arcing, each time i have connected the charger all the cell voltages displayed by the charger which is in fact the voltages of the 6p strings are identical. Any one cel in the pack that was lower would be supported by its permanently parralleled mate, these would also be supported by the other 2 pairs when connected for charging, so during charging they are all perfectly balanced as they are connected to each so cannot be anything other. During discharging they have upto now remained in perfect balance.
 
rojitor said:
Very nice setup, i understand how you did this parallel wire

But i do not understand how you did the parallel wire from the charger
P1000095.jpg

The pins in the D-sub connector on the charge lead each connect into a 2p cell group when plugged into the bike, then 3 of these pins are terminated into 1 wire, so this termination is connecting 3 2p groups into 1 6p group, the end result is 7 wires which go to the balance port on the icharger.
 
Expect the leads are adding resistance probably limiting current to an extent that's good was thinking might need to limit currents won't bother now.
Thanks
 
Echoing everyone's amazement; one small question thought: do you not need a precharge system at 18s or is the voltage low enough? (At least I can't seem to see one in the pictures and diagram. It would be simple enough to figure one in, but I'd like to hear what you would come up with. Perhaps a Jeremy/Kfong comparable soft start system?
 
I am trying to make a pack for one of my projects that will accept a plug for several channels like you have there with the brass fittings.

What kind of plastic is that and how did you imbed those fittings? I'm impressed and would like to be able to mimic.
 
Great piece of art. I would appriciate if you could show a picture from underneath the carbon fibre lid on your charger assembly, i would love to se the balance wiring down ther to. :)e
 
Tench and others. If you use these connectors, be sure to get rid of the metal frame edge (around the male/female pins). I had a setup like this, and if you aren't careful (me) and you accidentally put the metal frame in contact with 2 of the male pins while you are plugging in, then pins/wires will melt. Don't ask how I know this.

Adam
 
Back
Top