Micro-Solar Setup : My First Experience w/Off-Grid Electricity

[bruss01]

Chicken and the egg scenario (catch 22).

The BMS will not come online until it is being charged north of 10 amps.

The battery charger will not come on until it detects the battery, presence of 12v.

I had to do some hunting for this online, it is not included in the instructions:

Connect the battery charger to the B+ and P- posts, and make sure it is plugged in and with the charger switch to "on".

Using a large gauge cable or wire, short the B- and P- posts, and hold it until the charger comes on.

Hold this connection an additional 15 seconds, then remove.

I've just done this and the charger is now on and running - and more importantly I'm registering proper voltage from B+ to P-.

Now to see if I can manage to find/install the correct software and connect to the BMS to see what's happening under the hood.

ETA: there is a very distracting ticking noise from the BMS now even with the charger disconnected. Still getting proper voltage between B+ and P-. I hope this is not "normal" because it's irritating as all heck and just unacceptable for something that will be right next to where I work most days.

ETA2: Discovered BMS was cutting in/out every 5 seconds... further investigation revealed the silicone heat mats were on (supposed to be temp activated!). Cutting the heat mats off, the clicking/ticking stopped, and BMS is now steadily on. I can wire in a thermostat button (non-adjustable) but that won't resolve the issue with the mats causing the BMS to cut out. I'm disinclined to open up the whole enclosure again and remove batteries right now, so I'll just leave the heaters out of it for now, while I work out how to operate the BMS software.

ETA3: Had to reconfigure the phone app - it had a standard 100 AH cell capacity as a default, these are 280 AH rated cells. Once done, it showed the battery state of charge (SOC) as 33%. I have the charger on now, and the BMS app is reporting 80 amps of power going into the battery bank. The charger was rated 75 amps so it's nice to see I'm getting just a wee bit north of the promised performance there. The SOC dial is slowly rising, it's up to 39% now after just a few minutes. I'm monitoring for hot connections, smells, anything out of the ordinary.

ETA4: After being on the charger about 90 minutes, it has entered the "float" stage, with the charge amperage falling from 80 amps to 8 amps. I'm noticing that row #2 of cells is tending higher voltage, running 3.6 to the others 3.3 - no doubt this will limit capacity somewhat until all the rows become equalized over time. I suspect this is due to incomplete balancing prior to installation... Not sure how, exactly because I had them all on a measured voltage charge for days and all were registering very close to the same voltage at that point. Maybe a tolerance stacking issue now that they're all assembled.

Now that I have the bluetooth app working on my phone, it's time to tinker with the PC application via USB so that there is monitoring redundancy. Footnote - no appreciable rise in cell temperature according to the temp probe. Looks like I can charge at full amperage without worrying about batteries over-heating. Plus, my goal of being able to fully charge this bank in under 2 hours of generator time is a realistic one.

[91CavGT]

It can be very frustrating when getting kinks worked out on technology based items like the BMS, but on the good side you are able to figure it out prior to a SHTF event!


The 2 BMSs that I own are both very basic and have no kind of controls to them. They are both 4S with one rated at 40 amps and the other rated at 200 amps. My big MPPT solar charge controller though sounds like your BMS. I pray that I can get it hooked up and working right, much like what you are doing, before I need to do it while under duress.

[bruss01]

Right Cav - no way would I have ever guessed that arcane BMS cold-boot protocol without access to the internet. It would be useful to have a folder attached to the underside of the lid, for stashing documents on this procedure plus error codes for the lights on the charger, and the various manuals for BMS, MPPT charge controller, sine wave inverter and any other operation or troubleshooting procedures. Easy to find in time of need.

Still haven't gotten the PC app up and running. Main hangup there is inability to get usb-to-serial com ports online. I've tried a lot of things found online, none have worked yet on either of the 2 PC's I've tried it on, and I'm a tech guy. Going to leave that for now, maybe come back to it later. I've got one cable in the box that gets a bit warm at 80 amps (not bad, but noticeable) and it's likely that drawing 250 amps it would get unaccepably hot. Likely a poor electrical connection inside the lug. It's short, so it may be possible to replace it with a bus bar. After that's addressed, I can move on to installing the gear on the platform and putting those batteries to use.

This is definitely "next level" stuff compared to the lead-acid batteries I started out on... if only Tdale could see me now LOL! Great memories of that first foray, now years gone by. Becoming your own power plant and doing it in a highly sustainable manner - I'm finding - is not for the faint of heart nor for those who expect it to "just work". Whew. The devil is always in the details.

ETA: After another 3 hours on the charger in "float" the amps have gradually decreased from 8 to zero, with the bank voltage stabilizing at 13.6 - that's not optimal, but I believe it will improve with time as the cells get balanced in together - getting "acquainted" as it were.

[bacpacker1513]

Always good to do test runs with new gear, no matter what it is. Good on you Bruss

[flock6]

Great job

[91CavGT]

Get a multimeter, put it on ohms or the resistance setting, and test the total resistance of that cable. One test lead should be on one terminal and the other lead should be on the other terminal. A little resistance of less than 0.5 ohms is normal. But if the resistance is over 0.5 then you need to check the cable. That was industry standard 15 years ago. On my cables that I make, I try to keep the resistance under 0.2 ohms.

There are several factors that can cause an increase in resistance besides a bad crimp on the terminals. If the cable you are using is old and has started to corrode, if the cable has internal breaks on a lot of strands of copper, if the lugs themselves have a this layer of corrosion, if the terminal is not torqued down enough, if the cable has been overheated in the past, and of course there are all the ways a terminal can be crimped in a bad way, all of these can cause an increase in resistance in a cable or can cause the temperature of a cable to increase.

[bruss01]

Bluetooth app worked perfectly all day yesterday.

Woke up this AM, now the app can't find the BT BMS.

Unplugged BT module, pluged back in - nada.

Re-installed phone app - nada

I have a spare BT module, got it out... realized the plug doesn't fit this BMS.

Might be able to swap cords... doing a little research on that, don't want to fry something at this stage of the game.

At this point, getting the UART-USB connection to my desktop computer takes on a new importance and highlights the relevance of redundant systems.


ETA: Swapped out cords - second module is now online, BMS accessibility via BT is restored... for now.

ETA2: Spoke too soon - just lost connectivity, out of a clear blue sky, just sitting here. Tried swapping back and forth a few times... now it appears neither module is working.

ETA3: I've been checking periodically and it appears this is a random, sporadic kind of thing. It works when it feels like it.

[91CavGT]

Redundant systems. 2 is 1 and 1 is none. You might look at a basic BMS module as a backup. One that doesn’t need any kind of remote monitoring in order to be setup or to use. The basic Daly ones are like that. They aren’t something that you would want on a system like yours permanently but for temporary use it would be fine. Having the ability to fine tune adjustments as well as monitoring the battery bank is pretty awesome and would help you to extend the life of your setup.

[bruss01]

Replaced the short cable that was getting hot (triple copper pipe bus), and finished a connection on the negative end that I had improvised for testing. During the process, I discovered that the BMS cold boot process has to be repeated any time the BMS loses power. It retained all the settings though. I am pondering if installing a momentary switch for that might be a good idea and a future time-saver. Especially if years go by and I forget all about this quirk.

On another note: Work inside the battery enclosure is officially COMPLETED and tomorrow we move on to populating the platform! Now the fun really begins!

[flock6]

Good work man!