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[Doctorbass]

or.. I could translate : Adding a ZF7.2 Long brick to a ZF13 + powertank ZF3.3 SR 2017 !

DONE !!  and yes IT WORK and handling is still awsome!

I got a long brick with a low cell number 17 with higher internal resistance problem. it was no more usable as main battery on a ZERo but at lower power to contribute as a second power"tank" it work quite well!!

So... I removed the original BMS from the long brick and installed a aftermarket BMS from Jaibaida ( aka JBD BMS) on aliexpress that I know very well and use on all my DIY battery now. It is a 28s 100A continuous with bluetooth interface. The most complicated part was to connect it to the 40 pins 2.00mm spacing connector to monitor and and balance all the cells and also communicate with all 4 temp sensors.  I bought an adaptor for it. i even published the entire pinout of that connector. see pictures below.

I also had to build a rack for that battery on the passenger seat to be able to cary the 84 pounds and make it secure in place to avoid the battery to hit me in case of hard stop etc. I made it in wook with "L" aluminum etrusion all around it to secure in place the pack.

Now the interesting part!!

I have I think opened a new way of connecting SAFELY an additional battery to a ZERO WITHOUT the need to open the dog house ( the little box on top of the main monolith battery.  Basically what I have done is connecting that battery the same way as the powertank is done, meaning it is tied to the motor controller + and - BUT !!!  there is a contactor and a 100A fuse in serie with it. The contactor is a 100a contactor salvaged from a dead ZERO brick. I have used the coil signal from the powertank existing contactor  to pilot a the coil of small relay( used as a Buffer) that take 12V from the dc-dc  when the ZERO is powered ON or also from the chargers 12V fan supply line when the DC-Dc is OFF but the chargers are ON.  That relay take that 12V power and send it to the long brick contactor coil. I could have connected the 100a contactor coil directly to the existing coil of the powertank contactor but i was not sure the BMS could safely supply 2 contactor coil in parallel.

So.. the added long brick is only connected to the ZERo IF and WHEN the powertank contactor is ON, making that battery addition safe.  The main power harness from that battery  to connect to the bike is made fo gauge 4 and Anderson connector SB50 in a way that the total long brick internal resistance  plus the contactor resistacne and wiring resistance  is sharing the current following the same rule as ratio of capacity so all 3 battery are drained equally at the same time and there are no "circulating current" when the load vary.

Pictures comming soon!

Doc

[Specter]

Just make very sure this thing is VERY secure.  Not just from sliding off the seat but in EVERY direction really.  Things like batteries LOVE to wiggle around, and get out of your harness' for them about as diligently as a puppy dog will!   (Ask me from my CB / Linear amp days what happens when 600 amps gets shorted IN the car because a battery moved and pinched a wire).  Even a bit of 'slide' while you may say, well this is safe, it can only go XX far and it's caught, that right there, is a repetitive strain on an object, which over time, may fail from that strain... what next??

Otherwise, great job, it's always a great feeling when we are able to make stuff like this work.

Is it Practical / Useful?,  Possibly
Is it Dangerous?, Probably.
But the nerd cred you get with your fellow geeks is thru the roof !   

Aaron

[Specter]

After re reading thru your setup...
I am not sure how much power this thing will EVER need in either direction, but an SB50 Anderson connector is only good for 50 amps.  Is this sufficient for your gadget here? 

Also, and I am sure this is trivial but, Anderson connectors come in different voltage ratings.  The one you picked (the color coding I think is how you can tell but please verify that), can it handle the max voltage the battery pack can be under, even with a high potential kickback from the motor etc etc?  The teeniest, tinyest, arc over, arc / burn thru will turn into a Green flash and a glowing ball of plasma in milliseconds.  Those are not fun either!

Aaron

[Doctorbass]

After re reading thru your setup...
I am not sure how much power this thing will EVER need in either direction, but an SB50 Anderson connector is only good for 50 amps.  Is this sufficient for your gadget here? 

Also, and I am sure this is trivial but, Anderson connectors come in different voltage ratings.  The one you picked (the color coding I think is how you can tell but please verify that), can it handle the max voltage the battery pack can be under, even with a high potential kickback from the motor etc etc?  The teeniest, tinyest, arc over, arc / burn thru will turn into a Green flash and a glowing ball of plasma in milliseconds.  Those are not fun either!

Aaron

The battery is protected with a BMS that I installed It is also short circuit protected so I could make a dead short to the output and the mosfet will just open and no high current spoke can happen. the SB50 anderson connector are capable of 120A continuous on 6 gauge acording to the specs when used with silver plated contacts  https://www.andersonpower.com/content/dam/app/ecommerce/product-pdfs/SB50/ds-sb50.pdf. These SB50 were even used by ZERO on a battery with a 300A fuse back in 2009. I use them on 4 gauge and these remain cold. I use these Anderson connectors as well as the Powerpole 30 and 45A for 20 years now on multiple ebikes projects and I know them very well. I understand the engineering of a proper contact installation, cromp, derating on ambient temp ans ampacity for various wire size as well.  The housing color is just an indication. ex; Blue for 48V, grey for 12-24V etc.. but I use grey for all my projets as these are the easiest to find and i am not developpong a commercial product but only making DIY projects

[Specter]

You done your research and have a solid background in the electrical side.  This is very good to know.  I was not implying you did not know what you were doing, but just making sure it was safe, since I did not until now, know your knowledge level on things electric.

You have no idea how many people think, squeezing it with a pliers, is plenty good for a power connection on their main bus    Ive done that myself at times, in the, 'get the thing running' stage of projects, to go back later and follow on with the 'keep the thing from burning to the ground'  stage.  DC is also, just such a much nastier animal too when it lets loose vs AC power.

Aaron