Standardizing DB37 connector pinout for up to 32s

[Doctorbass]

(Post for further references)

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Credit to Bigmoose and Camlight for the advice

[CamLight]

Hi Doc,
Not sure if you can do this but I had some thoughts based on how industrial connectors have their pins/voltages mapped out for safety....

If possible, I'd recommend moving MAIN NEG down to Pin-1 and then use Pin-20 for CELL 2+, Pin-2 for CELL 3+, Pin-21 for CELL 4+, etc. This keeps all the voltage differences between any two adjacent pins at a minimum. Right now, there's over a 100V difference between Pin-32 and Pin-33 and that can easily lead to trouble. This remapping physically bunches all the cells taps at one end of the connector (and associated cable) and all the logic and power signals at the other end.

If possible, I'd also have MAIN GND and 12V GND share the same pin so you can have a two empty pins between CELL 32+ and the logic and power signals. This would use all of the connector's pins, but I think that would be OK?

[jonescg]

D-subs are rated for 200 V between pins, so I don't think it's too bad. I plan on using these DB-37s on my race bike. Winford Engineering builds breakout boards for these plugs; I'll be making use of 4 of them.

http://www.winfordeng.com/products/brk37.php

[voicecoils]

Ratings aside, which would you rather short, 3.7v or 100+v ? And we know some shorting will happen eventually... Just add spanners and beer

Camlight's suggestions seem sound to me.

Those breakout boards do look handy and will save a boatload of pita soldering. Hopefully they can take a high vibration environment.

[jonescg]

Cause I'm thick and I like simple sequential systems like Doc's

Most importantly, making sure the power side is female would solve most potential shorting issues.

[bigmoose]

Doc I like the idea of us standardizing a pin arrangement. I also FULLY support camlights suggestions, with two of my own. Move the telemetry signals and the housekeeping power, both 12 V ground and +12V down to the low voltage end.
1 12 V ground
20 12 V +
2 Alarm In
21 Alarm Out
3 Main Negative
22 Cell 1
4 Cell 2
... etc.

It too bad we don't have 2 more pins. Ideally I would want 2 wires to top of stack and 2 to the bottom of stack.

While we are on the subject of cell level connectors, I have a question for you geniuses. I am dabbling with an inductive balancing circuit that can either individually charge or discharge individual cells at 10 A average, 17 A peak while the stack is being bulk charged at whatever rate the bulk charger can supply. I am having trouble finding a multipin connector that I feel comfortable with to bring each cell's signals off the board.

[John in CR]

....While we are on the subject of cell level connectors, I have a question for you geniuses. I am dabbling with an inductive balancing circuit that can either individually charge or discharge individual cells at 10 A average, 17 A peak while the stack is being bulk charged at whatever rate the bulk charger can supply. I am having trouble finding a multipin connector that I feel comfortable with to bring each cell's signals off the board.

Now that's the kind of high pin count connector I want, along with the balancing circuit. Bigmoose, it will work during discharge too, won't it, or would it be too wasteful?

John

[Doctorbass]

Now that's interesting!... This thread is waking up!

I like your all suggestions, Bigmoose, Voicecoils, Camlight, etc.

I have to say my idea was to have the pin number corresponding to all exact cell positives for better identifications when troubleshooting.. but maybe i should wonder when exactly it would be usefull and at wich rate it would.. in other words, does it really worth?

This is true that if we use the pins in a way that the adjacent pin are 1 or 2s higher voltage not more, it would reduce possible blast short circuit.

Also, we need to consider that the goal is to have the female connector on the battery ( source) side and the controller( load) on the male connector pins side.

In the case we would need to get one extra pin, i thought that having the case of the connector ( normally as a shield) connected to the 12V ground or the main ground. But this would create another problem of possibly shorting any pins to the ground casing easily...

But while we talk about the posibility of shorting any too close connections... maybe we should figure out How it would become possible?
-While assembling and soldering it?... hmmm usually the connector must be soldered BEFORE having the wires connected to the battery ?
-While testing with a multimeter and connecting the probe to the pins?.. hmmm... ok, but it would be not possible on the female connector.. and just on the male connector... but it is on the load side.. so....

I wanted to have the 12V ground insulated from the main ground to avoid the current draw to it ( 12V section) affecting the voltage reading of the celllog cell 1... would it ?

This is becoming really interesting because connections standard is not as popular as it should for ourl community! so if having a standard spread enough over teh community, it wold make easy the troubleshooting.. especially during ebike event like the SoCal, TTXGP etc..

I already used the DB44 connector for a 40s BMS but.. the pins are too fragile and too close!
Well let say the DB37 seem to be the best solution from now with our voltage up to 32s lipo...

I agree to work together and find the best configuration possible. let's not forget the risk and the simplicity.

Doc

[Doctorbass]

Jogn, about the balancing circuit, that's a porblem we must solve. During the shunting o fthe resistors, the current draw is affecting the voltage reading of the celllog or the circuit that monitor the cells... Also to conteract this effect it is difficult to use wire gauge bigger size than gauge 20.

The best way i think would be to gave two female connector for the source ( the battery). one for the balancing and one for the monitoring. what is nice is that these cables for the DB37 are availlable also assembled and are easy to find, but most of them are gauge 28!.. making them useless for balancing feature.. but at least the could be used for the monitoring like for the celllog8.

I just bought the celllog breakout module from Robin of RWaudio. they fit 4 celllog connected for up to 32s and are isolated with very small relay. i'll have a DB37 installed on this module as well for the monitoring.

[John in CR]

But Bigmoose is working on some new balancing deal that does big current during high power bulk charging. My question is why just during charging? An ideal balancer would balance all the time. Then the pack isn't limited to it's weakest parallel block, and bulk charger and LVC is all we need.

[Doctorbass]

But Bigmoose is working on some new balancing deal that does big current during high power bulk charging. My question is why just during charging? An ideal balancer would balance all the time. Then the pack isn't limited to it's weakest parallel block, and bulk charger and LVC is all we need.

So i guess that we should need to switch it ON before charging the pack or before using it?.. otherwise it would do the exact same thing as the active current sharing balancer and balance the cells until they are all empty..

Because we must not forget that teh cells unbalance over the time, while the ambient temperature , pressure change! We must not consider that our cells stay balanced when being not used...


Any idea about that John?
Doc

[CamLight]

While we are on the subject of cell level connectors, I have a question for you geniuses. I am dabbling with an inductive balancing circuit that can either individually charge or discharge individual cells at 10 A average, 17 A peak while the stack is being bulk charged at whatever rate the bulk charger can supply. I am having trouble finding a multipin connector that I feel comfortable with to bring each cell's signals off the board.

Excellent! I'm definitely looking forward to hearing more about this!
What kind of budget did you want to stick to for the connector? I deal with this a lot with my designs and there are a very large number of connectors that can handle this application...but the price may be a problem.

[CamLight]

Another failure mechanism to deal with when considering pinouts....
I think we also have to consider potential long-term problems. As connectors are used, dirt and other contaminants often build up inside. Keeping the voltage between any two adjacent pins as low as possible helps prevent a short in case of water or conductive dust (either slightly or very conductive) entering or building up near/on the pins. Or any other unforeseen problem.

[Doctorbass]

Another failure mechanism to deal with when considering pinouts....
I think we also have to consider potential long-term problems. As connectors are used, dirt and other contaminants often build up inside. Keeping the voltage between any two adjacent pins as low as possible helps prevent a short in case of water or conductive dust (either slightly or very conductive) entering or building up near/on the pins. Or any other unforeseen problem.

About the porential failure would the silicon grease wouldreduce the risk ?.. i mean it is already used in many comercial EV for the low current connections ?.. I kow that the commercial connector also have sme sophisticated rubber seal but for a 37 pind iy might be $$$

At wich level should we consider the potential failure?.. i mean..all low current the connector on the controller are a as sensitive as all other but it still work for our kind of needs ?

Doc

[Doctorbass]

It too bad we don't have 2 more pins. Ideally I would want 2 wires to top of stack and 2 to the bottom of stack.

While we are on the subject of cell level connectors, I have a question for you geniuses. I am dabbling with an inductive balancing circuit that can either individually charge or discharge individual cells at 10 A average, 17 A peak while the stack is being bulk charged at whatever rate the bulk charger can supply. I am having trouble finding a multipin connector that I feel comfortable with to bring each cell's signals off the board.

Bignoose, have you a thread about that project? I agree with all other here, it look pretty interesting!

Doc

[CamLight]

Another failure mechanism to deal with when considering pinouts....
I think we also have to consider potential long-term problems. As connectors are used, dirt and other contaminants often build up inside. Keeping the voltage between any two adjacent pins as low as possible helps prevent a short in case of water or conductive dust (either slightly or very conductive) entering or building up near/on the pins. Or any other unforeseen problem.

About the porential failure would the silicon grease wouldreduce the risk ?.. i mean it is already used in many comercial EV for the low current connections ?.. I kow that the commercial connector also have sme sophisticated rubber seal but for a 37 pind iy might be $$$

At wich level should we consider the potential failure?.. i mean..all low current the connector on the controller are a as sensitive as all other but it still work for our kind of needs ?

Doc

My understanding about those greases is that they're only on the parts of the connector pins not actually touching the mating contact. That is, the grease is rubbed off where the two contacts, plug and receptacle, rub against each other when mating. I'm not sure that using a grease would help for us except for water intrusion? Grease is also a great dust magnet. Somebody with more knowledge about these greases and their use will hopefully chime in.

I like your choice of DB37. I don't think a different connector would be better. Projects here are budget-driven and DB37's are dirt cheap compared to other connector types. And electrical tape around the place where the connectors are mated goes along way.

The application for this connector are all low current...until two pins short together.
And while a sealed connector might prevent contamination and water intrusion, it still wouldn't address all the potential problems in having over 100V between two adjacent pins. Not sure how we should consider any potential trouble. I guess each person will make their own decision based on cost, time, and risk. But IMHO, any change that costs nothing but could even potentially prevent a problem should be made. Personally, I can't remember how many times my DMM probe tip has slipped off one pin and bridged two together.

[bigmoose]

John, I would be interested in what you might have as to a connector recommendation irregardless of price. It might open up my thinking.
1) I have MiniFit with a 9 amp rating if 3 pins are energized, dropping to 5 amps with 12 to 24 pins.
2) I also have some large TYCO 0.156 in spacing IDC style headers with 10 amp pin/terminal rating.
3) Then we go to the 16 contact size MIL-C-26482 mil spec stuff in a 24-31 insert shell arrangement, that will do the job at 13 amp tested; but is price uber prohibitive.

I would like to work in modules of 12 cells, with Kelvin leads on the top and bottom of stack, so something around 14 pins per bank.

So either way (cheap or expensive), I would appreciate your thoughts.

Next you gents need to know that I go real, real slow on this "fun stuff" development. I also do not like to release any details until I have successful prototypes running at TRL-4 which is: A system prototype demonstrated in a relevant environment. It just gets everyone all anticipatory, and typically it is a dry hole for me... (What can I say, I am pragmatic over my career, and more ideas fail then succeed.) I have been thinking about how to skin this cat differently for two years now. It takes custom magnetics and is currently heavy. Therefore I don't like the idea of it being on the bike/vehicle while it is "on mission." The current topology can prop up weak cells however while the main discharge is happening, but would require the magnetics to "hit the road..."

I also follow methy's threads in detail. I am a bit dismayed at how much work his HVC/LVC boards have been to manufacture in quantity in this country and by hand. I should be realistic and run the hand work numbers... because it just took me 20 minutes to R&R a single blown SO16 chip in one of my scopes this morning.

[johnrobholmes]

......

While we are on the subject of cell level connectors, I have a question for you geniuses. I am dabbling with an inductive balancing circuit that can either individually charge or discharge individual cells at 10 A average, 17 A peak while the stack is being bulk charged at whatever rate the bulk charger can supply. I am having trouble finding a multipin connector that I feel comfortable with to bring each cell's signals off the board.

I have a 24 pin connector that I use to charge my 20s pack. Harting Han E model, it was about $200 for the full thing with male/ female sides, bulkhead, waterproof cover, and strain relief compression nut. I've been testing it for about 6 months now. Wiring is done with pins 1 and 13 most negative, and ascending voltage pins going 2, 14, 3, 15.... with most positive at pins 24 and 12 IIRC. Pin 18 is the first 10s pack most positive, and pin 7 is the second 10s most negative. They are split so I can use two chargers. It is rated for 10a continuous (16a in some specs) on each pin and 18a bursts. 500v between pins, and 1000v if you skip every other pin. Commonly used in automated car washes. They make up to 24 pin with screw terminals and 46 pin with crimp terminals. They also offer bulkeads that allow for combining two smaller units into one large plug.

Specs on the Han-E line here http://www.harting-usa.com/imperia/md/c ... ess.ee.pdf


So far I can absolutely recommend it with flying colors. One of my friends is a sales rep for an electric supply house. We both searched for hours and couldn't find a single better choice for HV charging combined with balance charging. Certainly the single best thing I have done for an electric bike. I use two 1420I chargers with one big plug on the pack. Couldn't be any easier without an integrated BMS and bulk charger. If you want to try one out I can get a vendor discount for you.

[johnrobholmes]

I also concur that it would be best practice to place cell taps in a way that keeps pin to pin voltage differences to a minimum. I have built 4 packs using D sub connectors and I always did it this way. I have also had a few accidents and it saved my butt from totally blowing up the balance wires.

[Doctorbass]

OK so let's declare that we can conclude that the pins arrangement MUST be in a way that keeps pin to pin voltage differences to a minimum

But i stick with the idea of a simple , cheap and compact connector type.

The DB37 appear to be the best. I recall that the main idea is to provide a connector NOT FOR CHARGING but for monitoring and\or balancing.

I think that bypassing everyone that want a 30 or 32s setup in a profit of using the saved pins in parallel for carying higher current for charging is not the best solution.

lt's keep this standard for the rest of the connection than the charging current right?

Doc

[johnrobholmes]

For something cheap the db37 can't be beat! I needed to charge through the same plug as balance, and the low connect/ reconnect of computer cables made me search out more industrial solutions.

[jonescg]

I still can't see how you would short something no matter how the boards were laid out. Provided the female plugs are used for any power application, the only risk of a short is during construction. Once built, it's impossible to short them if the same wiring format is used. Personally I like the pin one = cell one pin two = cell two arrangement...

I think these DB-37s are "the shizzle" (Trademarked copyright Hyena all rights reserved)

[bigmoose]

Thanks John, that is a fine connector! With charging to every cell we have to factor in a connector that can do more than 20 or 30 mate cycles. You found one! Was it correct to summarize that one mated pair with hoods etc. was near that $200 mark in wholesale terms?

[CamLight]

I still can't see how you would short something no matter how the boards were laid out.

All sorts of ways you can still short things out...
Water, conductive dust (more common than you think at >100V), overheated insulation being pushed aside due to pressure and/or vibration, debugging a pack problem, testing after replacing a cell. But, there's always room for different pinouts!

[CamLight]

John, I would be interested in what you might have as to a connector recommendation irregardless of price. It might open up my thinking.

OK, at 10A-17A we're limited. I was going to recommend the circular MIL connectors, but you're right, they are expensive. The plastic shell versions are less so though. The Han-E's that John recommended are also fabulous.

For lower pin count, Neutrik has up to 7-pin XLR circulars that are incredible for applications that require over 1000 mating cycles. But, you're limited to 7-pins. The 3-pin versions are rated up to 16A but the 7-pin drops to 5A. I haven't had any problems at >10A though as long as the wire insulation isn't 80C-rated stuff.

If the Han-E's look good for you, I say go with them. Especially with that discount.