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Similar storage compartment in the front of my RV. I put down 1” foil backed styrofoam, then 1/4” aluminum plate with a 200w 48v heater sandwiched in between. 3D printed cell holders (that came with my packs purchased from Lion energy on fleabay) allow for some airgap between cells. Another...

Hardi-backer, cement-like board used behind tile work, available at most hardware stores.

Throw a thick blanket or reflective tarp over the PV panels in order to reduce their output voltage to a touch safe level.

Radio controlled aircraft, home automation, avid homebrew consumer!

Put a bigger dent in your bank account! LOL

Imagine how boring the world would be if we all thought alike! LOL

Your request reminds me of an old racing adage: cheap, fast, reliable - pick any two.

If any panels may be suceptible to shading, then parallel is best. Otherwise series as many panels as your scc will allow.

I haven’t, I’m just not a fan of having a potential single point of failure. OP asked for downsides of a single pack, just giving him one.

For me, it's not a single setting or single special feature, but a combination of features: 48V/16S compatibility and hardwired serial comms selectable top/bottom/both balancing Jason is actively engaged in continuous product development, and listens to customer requests The chargery is the...

Your understanding is more than you are giving yourself credit for. The key point is charging vs. discharging in subfreezing temperatures. I believe it’s perfectly ok to discharge LFP when cold, but charging is detrimental. Passive balancers discharge the cell with the highest voltage. Perfectly...

I have 64 of the same or similar cells, 50Ah, currently in 4P16S config in the front storage locker of my toy hauler. The pack rests on 1” styrofoam for both insulation and shock absorption. I live on a washboard road, so the pack sees its fair share of vibration. No issues so far, but it’s been...

I have my BSEE with 27 years experience in power distribution. The voltage dip on “start” and spike on “release” is characteristic of an inductive load. An inductor is basically just a coil of wire, which generates a magnetic field when current passes through it. When voltage is initially...

I'd like to see all cell manufacturers offer this type of terminal:

...and not necessarily in that order!

Spoken like a true Engineer! LOL My parents knew I was destined to be an Engineer when the first thing I would do with a new toy is take it apart!

If the pack has a BMS, a mid-pack open circuit will most likely damage/destroy the BMS.

Series connected panels are the way to go as long as your controller can handle the higher voltages (which it sounds like it can). There are several threads discussing the advantages of series vs. parallel.

Please elaborate on this statement. Show me an equally priced bms with similar features that comes in an anodized aluminum case. For us DIYers with remote monitoring needs beyond the range of BlueTooth, it's the only BMS in its price range with an auxiliary serial port. There's several of us...

I did something similar with a DIY 3-phase wind turbine which had 24 coils per phase. On startup, all 24 coils were in series. As RPMs increased coil arrangement transitioned to parallel in order to increase load on the turbine. Options were 24s1p, 12s2p, 8s3p, 6s4p, 4s6p, 3s8p, 2s12p and...

My best guess would be “arc blast”. Vaporized copper expands by a factor of 67,000 in volume, which is enough force to launch dang near anything!

I used this buck converter in my RV to eliminate the house battery. Now all 12v accessories are powered from the 48v bank.

I would guess the smaller gauge black and blue wires are from the BMS, likely mounted to the side of the battery (out of shot).

10AWG MC4 connections to a combiner box, then 8AWG from combiner box to SCC.

I finally got around to sniffing the data stream with a saleae, and saw no framing errors: Time [s],Value,Parity Error,Framing Error 0.244132960000000,$ (0x24),, 0.244219840000000,$ (0x24),, 0.244306720000000,W (0x57),, 0.244393440000000,'15' (0x0F),, 0.244480320000000,'16' (0x10)...

After seeing what you were able to accomplish on the main board, I’m confident you will find a way to make it fit! :LOL:

Comparing circular mils (cross sectional surface area) is probably a better comparison. 14awg is 4.107MCM and 1/0 is 105.531MCM, so it would take 26 14awg cables to equal one 1/0 cable.

Serial LCDs only require clock and data lines, one less than shift registers to drive LEDs. With appropriate pin selections (A4,5), both options could be made available in the design.

Griz, I placed the charge relay on the PV side of the SCC, so charging is interrupted without disconnecting the SCC from the batt bank.

An automotive test probe (old incandescent style) works great, or any automotive lamp (turn signal, brake/tail, etc) will work too. Super cheap!

Take a look at the Chargery BMS16T with a 600A shunt.

T Taps are not known for good conductivity or good current carrying capacity, so I would not use them for paralleling panels (or any application for that matter, but that's just personal preference).

My concern would be the machine screw termination at 200A continuous.

It’s not a good idea to series batteries with different capacities. During discharge, the 100Ah battery will reach 50% dod long before the 200Ah battery, likely resulting in reduced lifespan.

Your guess is correct. The current exceeds the ampacity rating of the switches, which will likely overheat and fail.

Assuming an 8SxP wiring configuration, Pros of smaller cells: Redundant strings. If one cell gives up, you're not dead in the water (bad pun) Cons of smaller cells: Dedicated BMS per string of cells. 500ah cells would require 4 BMS for a 2000ah pack, while 200ah cells would require 10 BMS...

Not much different than having exposed busbars, so my vote is the advantages outweigh the risk.

Yes, definitely feasible. I use a rc hobby charger to top off or discharge individual cells that are way out of balance. One word of caution when using multiple chargers simultaneously: Cheaper chargers may have inadequate isolation between their input voltage source and their output.

Looks a lot like my AIMS...

What shift registers are you planning to use for the LEDs and balancers? I’m sketching up an active balancer, and want to ensure full compatibility.

https://diysolarforum.com/threads/off-grid-solar-battery-monitoring-and-control-freeware.6662/

The Daly should measure ALL current in & out of the battery, and should therefore be the only thing connected to B-. All other equipment should be connected to P-.

An argument could be made there is some inherent redundancy in having 2 100Ah packs. If a cell goes bad in one of the packs, you still have 100Ah of capacity to get by on. If a cell goes bad in your single 200Ah string, you’re SOL. “Two is one, & one is none.”

I used to think folks that put heatshrink on all of their tools were just being “safety sallies”, until I dropped a wrench across my bus bars. Now my battery tools are either cut short to not reach adjacent busses, or wrapped in tape.

Svetz, I believe he meant “shore power inlet” vs. outlet on the RV.

It was a good deal at the time. If I could start over, I'd buy 280ah cells. My cell selection did not affect other equipment choices. I've been following @BiduleOhm design of a new BMS here.

Interesting. I'll try the same experiment this weekend to see if the framing errors are an "undocumented feature" and the Mega is masking them, or if it's specific to your unit. What is the cable distance between the BMS, your inverter ckt, and the Mega?

There are 10 kinds of people in this world: those who understand binary, and those who don't.

I’m more of a Teensy fan compared to the Raspberry, especially when interfacing with an Arduino. Teensy has a ‘Teensyduino’ IDE snap on which allows all code to be generated on a common platform. That being said, I was gifted a Red Lion CR1000 display (which has both serial and TCP/IP interfaces...

Any reason not to increase the size of the traces between the R30x resistors? They look thin in comparison to the mosfet traces.

Your CLK/SDO/OE pin descriptions on D6/7/8 were a big hint for your intentions. I have a collection of 74HC595 BOBs floating around, which meet all of your requirements except power consumption. They will work for my proof of concept, and I will follow your choice of IC when the time comes. I...

Currently balancing on both charge and discharge to help compensate for cell capacity differences. I need to do capacity tests on all cells individually then regroup them to have better matched 4p capacities, but testing 64 cells individually is a pita.

Will the nano use male/female headers? If so, you can use the space between the headers for several smd components. Also, have you considered usb access on the nano while connected to the balancer (assuming pins 0&1 are still unused) or will the nano have to be unplugged from the balancer for...

In that state, think of them as a charged capacitor or battery not connected to load.

A capacitor is much like a battery with high charge/discharge current but very low ah capacity. How many Farads you will need depends on how long the 720w surge from the ice maker lasts. I’m guessing 2 or 3 Farads of capacitance might be enough, but I’m not sure this is the most cost effective...

I spy, with my little eye, a coaxial cable stripper tool.

+1 for adding a capacitor to the load side of the Daygreen. I have the 13.8v 30a model (A4D13R8C30) and was seeing similar flickering issues when the water pump kicked on and especially when using the tongue jack. Installed a 1farad cap and dimming/flickering issues went away. Inductive loads...

Or Craig if u want it faster

Short answer: yes, it’ll work fine. Longer answer: some will argue that both legs of the 240vac circuit need to be switched off for safety. I’m assuming your contractor is single-pole. A double-pole relay would be a better choice. My .02, Cass

I had my doubts it would all fit on that board size, but you’ve done it!

Wow, sorry to hear of all the sw issues. Hoping all is back to normal without any loss.

Cool, thanks for the detailed explanation!!!

Impressive! Are 3D views available?

No. If you’re concerned about the exposed conductive ends, feel free to insulate them by covering in tape, but leave the center element exposed for inspection.

https://www.daygreen.com/collections/24v-to-12v-13-8v/products/24v-to-12v-60a-720w-dc-dc-step-down-converter-voltage-regulator?variant=7091449692193

Separating the balance board from the Main board gave me another thought: a dedicated watchdog monitor on the balance board, monitoring either CLK or OE. The shift registers could then be disabled (therefore inhibiting balancing) in the event an IDC connector comes loose or the BMS hangs. I...

Assuming temperatures are dropping while charging, you could begin (perhaps around LTD+10deg?) ramping down the charging current by modulating the mosfets. PWM signal would be at 0% at LTD. Not knowing the capacity of users battery, is difficult to select an acceptable resistor to parallel with...

Printing now to review. One step closer!

Some good discussion on them, along with an arduino sketch, Here.

The 7th wire is the ground reference for cell 1, labeled “-“ on the harness.

Wait... Geri Ryan has hair? I never noticed...

You’re correct, the Teensy 3.2 would be needed for 5V tolerant pins. $8 more than the LC. I didn’t look at power consumption, but should have prior to making the recommendation. I am envious of your knowledge of opamps, I need to brush up on them!

Wouldn’t an OLED or 4x20 serial LCD be. More cost effective and versatile display solution?

Yes, that would be some impressive balancing currents! LOL

I will study this today and get back to you.

Just don’t run safety wire between + and - of the same cell!?‍?

Yes, I’m confident using capacitors vs. torroids is a better approach. I’ll start with 0.1F 6.3V for testing. Are you planning to switch both sides of a common dump resistor, or have a dedicated resistor per cell and only switch one side? What MOSFET are you considering?

Passive balancing refers to dissipating excess energy from the highest voltage cell across a dump resistor. Active balancing transfers excess energy from the highest voltage cell to the lowest voltage cell.

Did some research, and it looks like they’re called castellated holes. OSH park design recommendations: https://docs.oshpark.com/tips+tricks/castellation/

Little ‘m’ is milli, big ‘M’ is mega.

Your frustration seems to be shared by many. The workaround seems to be store components in the centralized location, then archive the components with the project. It may be too late for this, but might be worth a try? You can also export all the modules in a .brd file at once via...

So, as I go back and forth between relays and SSRs with an inverter/charger, while wanting individual Charge & Discharge protection, I had the following idea: Working left to right, the RC network in series with the relay coils is to lower the holding current of the coils, with flyback diodes...

My current pack configuration is 4P16S. Top balancing has been less than successful, so now I’m in the process of capacity testing 64 cells one at a time with a 10A cycler. Yes, tedious. This has led to my fascination with active balancing, which should (somewhat) compensate for a weak cell in...

Revising my answer: Orange, Band Aids

Short answer: no. Long answer: Fuses have a voltage rating in addition to the amperage rating. Lightning potential will exceed the voltage rating of most if not all fuses we use, meaning the lightning will arc across the blown fuse gap.

Using a common dump resistor with complex switching is one step closer to closing the gap between our active/passive designs! The biggest difference I see now is 16-bit shift registers for passive balancing vs. 32-bit for active (16 for high cell selection, 16 for low cell selection), then using...

Thanks for the feedback, and welcome back! Haven't seen much of you the last few weeks.

For per-cell temperature monitoring, the only capable product I’m aware of is Stuart Pittaway’s DIYBMS.

We have a similar “traveling trophy” here at work, affectionally named the DA Award. I’m sure you can figure out the acronym!

https://www.eaton.com/us/en-us/skuPage.CCP2-2-30CC.html

Versatile, elegant. I like it!

Comments: Is J15 truly needed? The traces between J1&J15 would need to be very wide, plus J15 will consume significant board space. Or, thinking in reverse, if you keep J15 on the balance board, is J1 needed? Do you think the U930 input filtering is overkill? The +batt should have very little...

Have you considered placing the mosfets on a “modular” daughter board, replaceable by a terminal strip for those of us wanting to use external shunts and high-amperage relays?

Great explanation, thanks!

One trick to determining whether the panels are series or parallel connected is to cover one of them up with cardboard or other light blocking material. Parallel connected panels output current will be half, while series connected panels output will approach zero.

So close!!!

The 70A breaker on the PV positive is overkill, considering the Isc of the panels. Also, isolating the batteries using the kill switch will most likely damage the MPPT charge controller.

Assuming you stay above 10% SOC, I agree the cell voltage deltas will be below the balancer trigger voltage. Below 10% SOC, some cell voltages may fall off steeply, which would trigger balancing. Several cold sunless days in succession with no low voltage cutoff protection could put your pack in...