Looks pretty cool for a BMS (compared to everyone else at least):
This is definitely gets in some top ten list for Made In India just by style points alone ha:
Balance leads and temperature sensor connectors:
Dual communication ports, I’m hoping this means I’ll have wired and wireless options:
Firmware and hardware version, with on/off switch:
Telfon coated wires, again with the style factor:
Close-up of the connectors, I don’t think I recognize the exact type they’re using:
Nice looking BMS.
So thats a 20 cell connector/ port but only 16 is used. Any documentation.
How much current can it dispate per cell during balancing, since this is a passive balancer it will bleed it off by heat.
I will also in the not too distant future will add LFP, so will be keeping a eye on your progress.
For people using regular inverters which use lead acid battery where it will trickle charge after reaching the set voltage. Usually about 100ma to 200ma depending on the size of the battery. So in those conditions a LFP battery connected with a BMS it will the bleed those excess energy as heat. Wondering how this will dispate the heat with no fans. In my inverter when it trickle/float charges the current is below what my shunt can register and in a clamp meter its within the margin of error.
They have models upto 24S, I’m guessing they’re reusing the basic design, with pricing reflecting the quality of their analogue front-end (1mV accuracy in the X3 series and 5mV for the X1 series) and the number of mosfets, depending on how much current it’s rated for:
The PCB also shows the unused pins for the balance leads for that model, there’s 24 pins in total.
I figure this is the case since all of the X3 100A models are priced the same (Rs 10k) and the cheapest X1 30A model is priced pretty high at Rs 4K, probably because it uses the same design.
It’s a really well-designed product, they just needed to make one PCB and they have over 50 SKUs based on it: LFP, NMC, 30A to 100A, 4S to 24S. Can you tell I’m a fan? haha
The balance current is just 50mA, but interestingly they say their microcontroller does coulombic balancing — I’m excited to see that since I’m mixing two different types of cells in the same battery pack.
I’m guessing they depend on passive dissipation, there’s warning text on the device saying it should not be covered and they have some models with a heatsink.
I cannot state this enough, but this is one of rare products that I’m really proud to see come out of India, right up there with Ashapower. Both of these companies do not design to meet a price target, only to meet an engineering goal.
I’ve lost count how many times I revisit your older posts about your setup. It’s really well done and a source of inspiration.
I got a bunch of lugs and a length of 50 sq mm wire from Daystar Solutions, they arrived today:
hex bit for scale, this stuff is super big!
The pin type lug is for the isolator:
The ring type for everything else:
At 1C this battery should be able to provide 5000W easily, but my inverter is ~3000W.
I might get another inverter and connect it to the same battery or I might not.
I’m thinking maybe I should build this battery to handle 100A? I guess the safety factor itself should be worth it (so that nothing overheats or melts or catches fire because of undersized connections).
So far I’ve got a 100A terminal, a 125A NH type fuse, a 100A current shunt and a 125A isolator:
I’ll also have a circuit breaker that’ll arrive next week.
Would having both isolator and circuit breaker be redundant? The circuit breaker is for external loads (inverter), the isolator is for internal loads (monitoring) if I ever need to replace the fuse.
I’m a little confused, maybe the isolator is unnecessary.
I think I want the isolator before the BMS, would that make sense? It wouldn’t be wasted there.
The current shunt sizing is another topic but later.
If you want to switch on or off the load be it to the inverter input or output, AC or DC. You need to use a Circuit breaker. You can use a isolator, only when there is zero current flowing, else expect arcing. The Arc in a DC voltage is even bigger.
Thanks, yes I’ll have a MCCB like yours for a circuit breaker, but I’d like to also use an isolator somewhere if only because I already bought it ha.
I thought maybe the isolator to disconnect the BMS for the rare instance I need to change the fuse would be a valid place for it.
You wont need a isolator for the BMS since the balance leads are already connected, so no arcing. Its like the the pre charge relay in EV before the main contactor turns On.
That makes sense. I guess I’ll need to find some other use for the isolator elsewhere.
Something I forgot to mention with this photo, I’m considering using busbars as interconnects to save on lugs and to tidy up wiring.
Bus bar are fine just to be safe I would probably put some heat shrink on Non contact area of bus bar. Never know a simple screw driver or spanner may end up touching the other terminal no matter how far it is.
I searched for welding cables on maps and found this place using streetview:
I thought it’d be cool to have orange cables like Andy from the Off Grid Garage on YouTube.
But they didn’t have 50mm sq in orange, just yellow, so I got that instead.
It was Rs 280 per meter, about half what I paid for the Daystar cable.
Also the 100A molded case circuit breaker arrived, it’s super big ha:
(regular mcb for size)
Would’ve been nice if the Amici people took pride in their work and designed the laser etch graphic properly and not just stretch/distort to fill the etchable area.
Great information and probably it gave me a much needed boost to do some DIY which I have been postponing for years .
A suggestion - I always keep the inverter and the batteries out of the house and I also have a few fire extinguishers on standby . You should invest in fire fighting equipment as a priority .
22 months, and I’ve finally reached Version 0, haha!
Wired up everything together with no safety measures, open air free range:
Connections aren’t great, I’ve measured between 0.7 milliohm to 2.1 milliohm between fasteners, but that’s probably to be expected for stainless steel hardware.
However, it doesn’t work as I wanted it to. As soon as power cuts and the inverter switches to battery, the BMS registers a short-circuit and cuts power. It keeps trying to recover, but something about this inverter won’t let it.
If I turn off the inverter, then turn on the BMS, then turn on the inverter, it works.
But that means I’ll need to be around whenever power cuts, which isn’t practical.
Then I had the idea of paralleling some 7Ah batteries I had from my other UPSs, and that did work:
There’s no current draw from these batteries, they just help during switchover for a split second.
It’s going to be absurdly hilarious if I need lead acid batteries to make this lithium battery work with my inverter.
Anyway, I’ve been doing a rough capacity test, to see if there’s been any degradation since I got these cells. I’ve put on a ~20A continuous load for almost five hours now and all of the cells are still above 3V, it’s doing great. I’ll do a proper capacity test when I’ve finished building this, in a month or three.
To note: My automation flows no longer work, the low battery shutdown and safe startup etc, they relied on the lead acid battery monitors.
I’ll need to work out a way to get communication from this BMS to MQTT and Node-RED, preferably through the can bus interface, or modbus or uart. I’ve done uart to mqtt before, but I’d really like to use the can bus interface because it’ll auto broadcast. But that’ll happen after I regrow some brain cells. I’m just relieved that I can stay online now during extended power outages.
12x 105Ah mismatched C-grade cells paired with 4x top quality 100Ah cells and and this BMS balanced it down to a delta of 29mV
I thought I would’ve needed an active balancer or a more effective passive balancer, so this is a really nice surprise.
Replying in this thread so the other doesn’t get derailed.
Yes, that is one of the things I’m going try out.
Yes, that’s the plan, I’ll be doing efficiency calculations to compare before/after.
The BMS is potted/sealed. This BMS is designed to protect against >500A short circuits, the datasheet says response time for short circuits is 8 microseconds.
Also from the datasheet:
I suspect that it’s the magnetic flux in the transformer from float charging after a power cut is triggering the short circuit.
It’s fine if I do a cold start when there’s no power.
Forgot .. the 230v line will be copper . You just need to rewind the out 24v core . If you are good with transformer winding you could probably do it within 1000 rupees .
I found this jig on banggood and it came with a step-drill bit + stop collar:
Heh, put something off long enough and someone will make it easier.
Nothing like this available a year ago when I bought the drill press.
It makes my previous setup completely unnecessary!
For posterity:
