Finally found a LiFePO4 BMS with Low-temp Charging Protection

[rin67630]

That's not what I meant.
If the battery is too cold and you have solar charging energy that is available, why not use it to heat the battery to a level where it could accept a charge again?

 

[HRTKD]

That's not what I meant.
If the battery is too cold and you have solar charging energy that is available, why not use it to heat the battery to a level where it could accept a charge again?

That's why I set the low temp charge limit of the solar charge controller to be lower than the limit that the BMS uses. The warming pads can use the power from the solar panels to warm the batteries. However, the warming pads will still use power from the battery if the solar panels aren't producing.

 

[baipin]

Are the 3x 10AWG wires sufficient for sustained 100A-120A current (e.g. for several hours) on the JBD BMS?

Especially since they're soldered and 120A seems to be close to the ampacity of 10AWG, I'm worried the solder could melt, under max draw, especially if one of the 10AWG was not terminated well. As it is, I am not too keen on terminating 3 wires in a single lug, nor stacking 3 lugs.

Would I be better served connecting the battery to the BMS with a single wire, and then my two BMSes together, with 3mmx15mm bus bars? Unless I'm missing something I feel like this might help maintain better balance between both batteries (i.e. less difference in resistance), eliminate the issue of crimping multiple wires into a lug or stacking lugs, and eliminate the chance that some wires carry more current then others, leading to overheating and failure.

Or, is this needlessly complex?

 

[Sgt Raven]

The 3 wires on my 120A fit well in a 4AGW lug or butt connector. Using the later, you can extend the wires to any length you need.

 

[HRTKD]

I ordered mine with three wires, 8 awg. However, I haven't pushed the 120 amp limit.

 

[baipin]

The cables connecting my cells together will be crimped lugs with 2AWG (I'm hesitant to use busbars as they'd be in a high-vibration environment offroad). 3x 8AWG would be much closer in cross-section to the 2AWG cell connections, which themselves, have a similar cross section area to the bus bars usually paired with these cells, at roughly 40mm^2 from what I've seen.

Unless I'm missing something, I'll stick with the bus bar idea or just resolder 8 AWG as used above.

 

[rin67630]

However, the warming pads will still use power from the battery if the solar panels aren't producing.

That is exactly what they should NOT do.
In that case leave the battery getting colder instead of wasting energy to warm them up.
Once sun comes back: first warm the battery up to >0°C, then charge them.

 

[HRTKD]

That is exactly what they should NOT do.
In that case leave the battery getting colder instead of wasting energy to warm them up.
Once sun comes back: first warm the battery up to >0°C, then charge them.

I disagree. I have plenty of battery capacity. If the batteries have to wait to come up to temperature, that's lost charging time. Keeping the battery in the 35° F to 45° F range doesn't seem to be taking a lot of juice.

 

[squowse]

Are the 3x 10AWG wires sufficient for sustained 100A-120A current (e.g. for several hours) on the JBD BMS?

Especially since they're soldered and 120A seems to be close to the ampacity of 10AWG, I'm worried the solder could melt, under max draw, especially if one of the 10AWG was not terminated well. As it is, I am not too keen on terminating 3 wires in a single lug, nor stacking 3 lugs.

Would I be better served connecting the battery to the BMS with a single wire, and then my two BMSes together, with 3mmx15mm bus bars? Unless I'm missing something I feel like this might help maintain better balance between both batteries (i.e. less difference in resistance), eliminate the issue of crimping multiple wires into a lug or stacking lugs, and eliminate the chance that some wires carry more current then others, leading to overheating and failure.

Or, is this needlessly complex?

I think I asked on a different post but didn't get much response -

What's the problem with stacking multiple crimped lugs on a battery post?
Or - crimping multiple cables into one lug (something I've not considered).

I'm planning on trying the 3 x 10AWG wires and seeing what temp they get to under 100A load.. Just waiting for cells!

 

[HRTKD]

There are two problems I had with stacking three lugs on the same terminal.
1. Coordination. It was a bit of work with to keep them all in line. There's actually four on the battery post since there is also a small lead from the BMS.
2. Bolt height. The more you stack, the longer the bolt needs to be to get into as many of the terminal threads as possible. The fewer threads you get mated up, the more likely it is that you'll strip the threads.
3. Aesthetics. This isn't a problem, it just doesn't look good to have the three big wires flared out so much.

 

[Sgt Raven]

I think it is a cleaner look and fits better, crimping the 3 leads into one lug/sleeve. If you need more length, it's easy to go from the three 10AGW to one 4AGW cable.

 

[rin67630]

I disagree. I have plenty of battery capacity. If the batteries have to wait to come up to temperature, that's lost charging time. Keeping the battery in the 35° F to 45° F range doesn't seem to be taking a lot of juice.

Of course, there are different figures depending on where you live. Keeping the battery warm might only be advantageous, if you are really sure, that the next day will provide enough juice. In situations, where your panels might be covered by snow for several weeks, that is not valid anymore.

 

[HRTKD]

Of course, there are different figures depending on where you live. Keeping the battery warm might only be advantageous, if you are really sure, that the next day will provide enough juice. In situations, where your panels might be covered by snow for several weeks, that is not valid anymore.

Totally agree. If I knew my system was going to be under snow for more than a few days, I would just shut everything down, including the BMS.

 

[Sgt Raven]

Unless it is consistently snowing, you could broom them off. You could get more output when there is snow on the ground, from reflected sunlight off the snow.

 

[kmcintyre]

I set up two of the BMS with 4S 200Ah CALB cells, but can't seem to get the xiaoxiang BMS to work with Android 10.
According to this site, there is no support for Android 10. JBD / Xiaoxiang Smart Bluetooth BMS - wnsnty.xyz
Is there an app that will work with that Bluetooth module and Android 10?

I just looked at that site and they state Android 10/11 support but who are they as their version has a lot higher number than other versions I see from google play store, etc.? Is the wnsnty.xyz legit?

 

[Mark44]

Looks like this is the best bet if you are using Andriod 10. While the name is correct, the site may or may not be legit. Since it is for an application that has relatively little exposure to any issues, I am going to use it. I will report back if and when I get it downloaded and running. Thanks for posting this link!

 

[Mark44]

I just looked at that site and they state Android 10/11 support but who are they as their version has a lot higher number than other versions I see from google play store, etc.? Is the wnsnty.xyz legit?

OK so I got the app. Seems to work well. All details of the battery are showing, I am able to modify parameters.

I am satisfied that this works as intended.

 

[squowse]

OK so I got the app. Seems to work well. All details of the battery are showing, I am able to modify parameters.

I am satisfied that this works as intended.

Maybe test the low and high voltage cut outs. I saw someone here had found theirs hadn't cut out for some reason.

 

[Druide]

First thanks for the great info to all. I have the 4S BMS from Batteryhookup and I made the changes for the low temp cutoff. Unfortunately the discharge switch is now set to off. I tried changing the parameters back and made other adjustments but still no joy. The BMS has no output as the discharge switch is still set to off. Has anyone found a good default settings list yet? Any ideas to get this BMS out of brick status?

Did you found that in Function setting menu, the 1st switch (Switch function) must be set to off for the discharge to be on. That's strange, but that's the only way i found to make it work. Unfortunately, if there is no load or a very little load, the discharge turn off by itself after a time. I'm curious if somebody found a way to avoid this behaviour?

 

[baipin]

A question for those of you who have experimented with these BMSes and their Arduino compatibility...

I've tried to connect my BMS to an Arduino Nano and OLED to read and display SoC information. However, I never see the RX LED light up on the Arduino as I'd expect it to; it seems the BMS isn't sending anything to the Arduino, though I do see the TX LED light up as I'm assuming it should. Right now the OLED displays 0% SoC when it should be 89%.

I connected the Arduino to the BMS via UART. The TX pin on the BMS to RX0 on the Nano, and the RX pin on the BMS to TX1 on the Nano. The GND from the BMS is connected to the GND pin on the BMS (the one located between VIN and RST pins). Power for the Nano is coming via 5V from a bench supply, completely isolated from the BMS. It goes to the 5V pin, and the same GND pin as I used for the UART communication.

The code I'm using is located here: https://pastebin.com/aHgMpeSp

Would I have better luck going through the UART to USB module, then from USB to ? I have one of those, and it connects to my PC just fine - I can use JBDTools no problem. Any help would be greatly appreciated!