Old BMS Hardware Thread

[GregsGarage]

Still waiting for my current sensor pcbs to arrive, but just saw this.

[hohisilver]

They don't seem to do a 200A version though; not sure if I need it but I bought the 200A bidirectional sensor. Due to an oversight, 2 of them in fact...

[GregsGarage]

My Allegro pcbs arrived this morning. The current sensor fits , but no time to actually test it over the next week or so.

You need to add the current limiting resistor and the board also has space for a couple of decoupling caps, see app notes of sensor for recommended values. Sorry about the poor picture quality.

[hohisilver]

I'm definitely interested - have you got a spare I can buy?

[GregsGarage]

I can post one out to you. Be aware that I haven't tested them yet so you will need to check everything carefully, I will not be responsible for any damage caused by mistakes to the board. I am using the 50 amp version, I have no idea how the pcb traces will hold up when using a 200 amp sensor, for that matter I don't know how they will hold up at 50 amps!

PM me your address and we can arrange something.

[hohisilver]

Sent

I was planning on reinforcing the high-current tracks with solid wire/solder anyway, so I'm sure it'll be ok.

[hohisilver]

You need to add the current limiting resistor and the board also has space for a couple of decoupling caps, see app notes of sensor for recommended values

I'm going to be mounting and hopefully testing my current sensor this week, but apart from a .1uF decoupling cap, the application notes on the data sheet I have give no clue as to the value for Rf, and simply "Cf is for optimal noise management, with values that depend on the application". Anyone any suggestions please?

[GregsGarage]

Ian I used around a 300 ohm resistor, it's just for protection in case of a wiring short. I don't think it's value is too critical, but you will have to fit one to the board. As for the 2 caps, not sure. The they are wired in parallel, so can be left off. I don't think Peter is using any caps on his setup, also if you are using V2 of the master pcb, it has some noise filtering components on board. Maybe try it without the caps first and see how it works, then add as necessary. I haven't had the time to try mine yet.

[hohisilver]

Thanks Greg - I've still got a load of 330R resistors left over from my master/slave build, I was going to stick a .1uF across the supply anyway but I'll probably leave the other cap off.

Cheers

[GregsGarage]

I have been working on my noise issues when the controller operates. The software change to the slaves has helped. I still have an issue with the front slave pcb not receiving commands on the slave bus. Seems to be a limit to how long the slave bus can be, so if all your batteries are close together, shouldn't have a problem. For now I am going to use Peters isolated bus trick on the slave bus between the 2 slaves.

Since I will need my isolated supply for the slave, thought I would try something different on the master bus. Here is the schematic.

Evi-masterSch.jpg (31.72 KiB) Viewed 16030 times

This was inspired by the EVILbus designed by Lee Hart and others.

The waveform isn't as clean as the isolated bus waveform, but it is perfectly acceptable as far as the master is concerned, haven't seen any data errors.

Evi-masterBus.jpg (20.11 KiB) Viewed 16030 times

The little spikes are the 16khz switching noise from the controller. I am sure that some tweaking could reduce it further, but if it works, I am happy.