Finally found a LiFePO4 BMS with Low-temp Charging Protection

[Stupid Monkey]

between the main cell pack negative and everything else I guess (Its @Will Prowse diagram from his website)

 

[Woggs1]

Can anyone post some screenshots from the app?

It also has "Battery State" view, "App Setting" and "About Xiaoxiang" views.

 

[Woggs1]

I found out that you can cut off the batteries from the app.

If you see this screen then there is currently no electron flow:


This screen means electrons can flow:


The default is no flow (had to figure that out the hard way).

 

[Steve_S]

Typically it goes between the battery and everything beyond it, the first item for the negative to touch. Then you need to calibrate for it by taking the voltage @ the batt terminals and then on the shunt to see if there is any voltage change with a good DVOM (digital volt meter) and programming in the difference if there is one. I don't know if your SCC or Inverter can use that but if they can, they also need to know if there is a difference, my equipment is different but it can use shunt values. Be aware the a good standard brass shunt is 500A / 50mv with calibrated accuracy, I've seen some nasty knock offs that aren't that accurate.

 

[Bob B]

Does anyone know if the BMS Will is recommending can be connected in parallel with another ..... 2 100A batteries connected in parallel to give 200A capability? @Will Prowse

 

[FilterGuy]

Does anyone know if the BMS Will is recommending can be connected in parallel with another ..... 2 100A batteries connected in parallel to give 200A capability? @Will Prowse

Do you mean like this?

I do not have experience with this BMS, but for the most part I would think it would work fine.

My one concern would be this: If one of the BMS's kicked off (Low temp, under voltage...etc), the other bank would suddenly be trying to carry the whole load. Depending on what the other BMS does, this could stress the other bank.

* If you can set both BMS's to kick off at the max continuous current rating of the battery (typically 1C) you would be fine, but you would not be able to handle short term peak loads that the battery specs typically allow.

* If the BMS has a setting that allows a peak load for x seconds, you are golden. (The BMS in the Battleborn has this function.)

 

[FilterGuy]

Actually, now that I think about it, the Peak Load vs Continuous Load could also be a problem with a BMS on a single 12 V bank.

If the BMS only has a single over-current setting, the most conservative approach would be to set it at the max continuous current that is specified for the battery... but that does not allow you to over-current.

If you have a big battery bank compared to your load, this should not be a problem because your peak load will probably be less than the max continuous specification. However, if you have a 100 Ahr battery rated at 1C continuous, but your load occasionally peaked to 120 Amps for a few seconds, what should your BMS over-current protect be at? If you set it to handle the peak load (say 125A) , you are not protected from a continuous load between 100 and 125.

Does anyone know if the BMS Will reviewed has both continuous and peak over-current settings? It seems to me that it would be a SMOP (Small Matter Of Programming) for the developers.

 

[Steve_S]

Each "Battery" requires it's own BMS. A battery as defined for this is any combination of cells connected together to make one battery unit as a whole. Just like Lead Acid batteries have 3 or more cells that make up the entire battery.

Be careful of being penny wise & dollar foolish. Cheaping out and kludging things can & often will come back to bite you while draining your wallet. A BMS is cheap safety insurance for expensive cells. Don't rush, think it out and appreciate that "shit happens" and you want to cover yourself for when it does.

 

[FilterGuy]

BTW: if you were to buy two Battleborn and hook them in parallel, you would have the diagram I show above. That is a good indication that there is nothing fundamentally wrong with parallel BMS setups, but you have to think through the implications. The battleborn BMS covers the concern I raised above, Other BMS set ups might not)

 

[Bob B]

Do you mean like this?
View attachment 4571
I do not have experience with this BMS, but for the most part I would think it would work fine.

Yes .... That is the configuration I was considering. I know that some BMS can be configured in parallel and others can not. Battleborn and others can be connected in series and in parallel but I don't know for sure with this one.
The supplier I bought my battery from says their non-smart BMS can be parallel connected, but their smart BMS cannot.

 

[FilterGuy]

The supplier I bought my battery from says their non-smart BMS can be parallel connected, but their smart BMS cannot.

That is an interesting statement.... did you ask them why? I would be curious.

Also, it might be worth asking battery hook-up since they are selling it.

 

[Bob B]

That is an interesting statement.... did you ask them why? I would be curious.

Also, it might be worth asking battery hook-up since they are selling it.

I didn't ask .... I will send an email to my contact and see if they can find out.

I sent battery hook-up a message a couple days ago ..... no response yet, but it's the weekend. Just figured I'd ask a wider audience.

 

[Stupid Monkey]

Well mine's arrived in the UK, with a £25 bill for import duties/tax etc

 

[lmwilco1]

How many wires are in the individual cell wires? I see 1 black, 1 red, and maybe 3 white? Does it say how to connect them?

 

[simple2010]

How many wires are in the individual cell wires? I see 1 black, 1 red, and maybe 3 white? Does it say how to connect them?

I believe it came with a wiring diagram but it's wired up the same as most any BMS. The black wire goes to your overall negative, the red wire goes to your overall positive. The white wires are for the other positives and need to be done in order. Check out a wiring diagram for a Daly version and it's the same with variation in the color of wires.

It's also a good idea that when you plug it into the bms, try to do it at an angle that ensures the negative wire is being plugged in before the other positives. Several / most of the ones I've done don't have a longer post to ensure negative is always in first. If you screw that up, in all likelihood you'll fry the BMS (ask me how I know.)

 

[atatistcheff]

Just got this BMS and it works great. I'm not sure what all the settings mean in the app though. In particular:

"Open Balance" can be open or close
"Balance Mode" can be charge balance or static balance
"Balance turn-on voltage" currently is 3.4. I assume that means it will only balance if the cells are above this voltage?


I can guess at some of these settings but I'm betting someone here actually knows what they mean.

Thanks!

 

[Steve_S]

Balance mode:
Open Balance = On / Off ?
charge Static = when the battery is not charging or discharging, only when in storage / static mode
charge balance = Balance when battery is charging
"Balance turn-on voltage_ you have that right.

I so love the Chinese to English chinglish translations. Surprising the translation software is still so bad after so many years.

 

[chevymike]

@Will Prowse When are we getting the video on this system? I am sure we are all hoping you will explain the settings as well.

 

[Will Prowse]

@Will Prowse When are we getting the video on this system? I am sure we are all hoping you will explain the settings as well.

Yes, planning to film it today after I edit my LTO video. Its super long haha. Doing that now.

 

[FilterGuy]

From the manufacturers website https://www.lithiumbatterypcb.com/p...e-and-e-scooter-protection-2-2-3-2-2-2-2-2-3/

View attachment 4297

Note that it does not mention the under-temp cut-off.