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Re: E63 LG 63Ah NCM battery group buy

Posted: Fri, 26 Jul 2019, 12:40
by Richo
Looks nice
But I will suggest one change...
CN1 I assume is your programming header.
Can you please upgrade to using TC2030-MCP-NL or similar?
Even if its not for this design but future designs.
http://www.tag-connect.com/TC2030-MCP-NL
The cable is available through your usual line card suppliers.
Ignore the fact its for ICD it'll work just as well for any Micro.

Re: E63 LG 63Ah NCM battery group buy

Posted: Fri, 26 Jul 2019, 14:29
by francisco.shi
I have made exactly the same as that plug but using test probes and a small pcb.
There is no connector soldered to the pcb.
There is another pcb with the spring loaded probes that make contact on the pads and has the standard plug to the programmer.
I am probably going to make lots of these boards so I need to build a jig for programming and testing.

Re: E63 LG 63Ah NCM battery group buy

Posted: Sat, 27 Jul 2019, 07:42
by 4Springs
Ah, now I see. The boards are basically soldered onto the nuts, then there is another piece of flat aluminium to take the pressure against the clamp. A very neat way to do it.
They are round nuts though, so you can't put a spanner on them to tighten against. You're tightening the bolt against your solder joint and pad - good enough to get them nice and tight?

How many cells do you have in a row (end-to-end)? Let's say you have two. You have a BMS board between them. If your BMS does one cell per board, then with two cells you'll need two boards. Where is the other board mounted?
Or perhaps your boards do two cells each? I can see two "Battery +" holes.

Burying the BMS boards is one thing that I'm thinking about. My battery box design would mean that access to half the cells would be difficult, I'd have to remove the other half first. I'll have to think about that design challenge, it might be easier to re-design the box than to design the battery to suit. As you say, access to the BMS boards should not be required, but 'famous last words' and all that...

Re: E63 LG 63Ah NCM battery group buy

Posted: Sat, 27 Jul 2019, 13:43
by francisco.shi
4Springs wrote:
Sat, 27 Jul 2019, 07:42
Ah, now I see. The boards are basically soldered onto the nuts, then there is another piece of flat aluminium to take the pressure against the clamp. A very neat way to do it.
They are round nuts though, so you can't put a spanner on them to tighten against. You're tightening the bolt against your solder joint and pad - good enough to get them nice and tight?
You only need to tighten the clamps enough to close the ends. If you overtighten the clamps it will try to bend them in the opposite direction and will not have even pressure. As the aluminium expands or moves the clamps take up the movement. The clamps would need to loosen 4mm or so before you start loosing contact pressure.
4Springs wrote:
Sat, 27 Jul 2019, 07:42
How many cells do you have in a row (end-to-end)? Let's say you have two. You have a BMS board between them. If your BMS does one cell per board, then with two cells you'll need two boards. Where is the other board mounted?
Or perhaps your boards do two cells each? I can see two "Battery +" holes.
I have two module lengths one has 5 the other has 2. On the end of the module there is a BMS board that has no thread on the spacers. The bolt goes thru the board then the spacer then the clamp then the aluminium bus bar.
The two battery holes are for two separate connections to the other terminal. One is for the bypass the other is to run the BMS and to read the voltage. The reason for the two wires is that the bypass can handle 10A continuous so you can have a peak as high as 20A there can be a significant voltage drop on that wire and since the BMS can balance during charge and discharge we do not want to read the wrong voltage because of the current running thru the bypass wire.
4Springs wrote:
Sat, 27 Jul 2019, 07:42
Burying the BMS boards is one thing that I'm thinking about. My battery box design would mean that access to half the cells would be difficult, I'd have to remove the other half first. I'll have to think about that design challenge, it might be easier to re-design the box than to design the battery to suit. As you say, access to the BMS boards should not be required, but 'famous last words' and all that...
The BMS board is very straight forward to interface with a master controller.
You need a master controller for the battery pack that will disconnect the battery if the current, temperature or voltage gets out of preset limits so you protect the battery. That controller also does the handshaking with the charger.
It only has a few commands one reads the inputs (voltage and temperature)
The other tells the BMS what voltage to aim for and how hard to bypass. The BMS then will try to bypass if the voltage is above the setting.
If you want to use it as a conventional BMS you set the voltage to your bypass voltage as with any other BMS. If you want to balance while charging or discharging then when discharging you set the bypass voltage to the lowest cell voltage. So any cells with higher voltage will need to supply more current. As the voltage drops you need to keep changing the setting. When you are charging (like during regen or charging) you set the voltage to the highest cell voltage until you get to the maximum allowable cell voltage.
Just remember that the energy that is bypassed is pumped back to the output of the battery pack so the energy is not lost as heat.

Re: E63 LG 63Ah NCM battery group buy

Posted: Wed, 18 Sep 2019, 19:51
by Schultz
Hello,

What is the maximum current that you managed to discharge with the actual mechanics that you use?

Re: E63 LG 63Ah NCM battery group buy

Posted: Wed, 18 Sep 2019, 21:11
by francisco.shi
The maximum I tried was 2C continuous for 30min. That was about 400A.
I didn't do a higher current because I didn't have a load that could handle it. The pack voltage was 40v.

Re: E63 LG 63Ah NCM battery group buy

Posted: Thu, 19 Sep 2019, 21:43
by Schultz
400A is a lot of current, are you using busbars for connecting your load?
Anyway very nice design, hope it will serve you well

Re: E63 LG 63Ah NCM battery group buy

Posted: Fri, 20 Sep 2019, 05:09
by francisco.shi
I put an 8x50mm short piece of copper that connects to the tabs on one end and the other side goes to a length of welding cable that goes to the load.