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Good Chinese BMS review
#31
I might be interested in giving these a try as well.  While there is a lot of info on the Aliexpress listing I do not see a link to a manual of any kind .... is there one and is it the usual Chinese jibberish or one that is actually useful?  Thanks,  Richard
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#32
Love the discussion you guys teaching me so much, thanks guys. Im not there yet but working on it, was debating the bms no bms issue, definitely batrium is way outa my league its like some can and some cant, i'll consider the chinese bms not because its cheap but because its affordable.
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#33
[quote pid='46935' dateline='1551915698']


(03-06-2019, 10:28 PM)Cherry67 Wrote: Is there a 10s as well ?
My needs...

Here you go, 10S:
https://www.aliexpress.com/store/product...61e8Vut6Kd
[/quote]

Has arrived.
Test with a small batt coming.

Will soon be married to a 2 kWh Block. Will be interesting if it stays balanced.
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#34
(03-27-2019, 03:49 PM)Cherry67 Wrote: [quote pid='46935' dateline='1551915698']


(03-06-2019, 10:28 PM)Cherry67 Wrote: Is there a 10s as well ?
My needs...

Here you go, 10S:
https://www.aliexpress.com/store/product...61e8Vut6Kd

Has arrived.
Test with a small batt coming.

Will soon be married to a 2 kWh Block. Will be interesting if it stays balanced.
[/quote]

Can somebody pls. Tell me how to connect the PC to the BMS ? Does that run over Bluetooth as well ?
I do not really understand the instructions....

Update: Most of the problems solved. No More help needed.

This BMS is really a good investment !
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#35
Seem to work pretty good, but the app is terrible. Anybody can point out explanations or operationg instructions for the features shown in the App ?
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#36
I have been using this BMS for almost a year now. These are called "Xiaoxiang BMS" Here's my 2c:

I have put together a 7s second life battery bank. I have set up my Victron SmartSolar with a maximum voltage of 28.7V (that's 4.1V per cell) and 15A max charge. I have set the BMS disconnect voltage at 4.25V for any cell group. As soon as the voltage reaches around 27V, the current has already dropped to around 4-5A by the charge controller. Above 28V, the current is down below 500mA. The thing with this BMS is that it does not detect currents below 400mA (see CON[1] below), at least as I've set it up through its calibration function. At this point, it could be (depending on the overnight usage) that a couple of cell groups could be around 4.1V and another group at 3.95V, hence unbalanced. I have set the balancing start voltage at 3.95V and have selected the balancer to work when not charging (see CON[2] below). At this time, balancing starts and until the sun goes down, the pack is completely balanced. Every day. Quite pleased with this BMS.

However, there are a couple of drawbacks. Here we go:
CONS:
1. Current detection is a bit buggy. My BMS came calibrated at around 15A I guess. That's the current that the BMS and my DMM would agree on. However, when the current would fall to 1A, the BMS would register ZERO. I used the calibration function to fix it to 5A. Then, it would drift on high currents, but would detect currents as low as 400mA. This does suck a bit.
2. The balancer works either: a. ONLY when charging or b. ONLY when NO current goes through. I was hoping that I would run the balancer 24/7, but this is NOT possible with this BMS. It runs either when charging (which is a bit useless, since second hand cell strings tend to voltage sag under load), or when RESTING, which means that balancing will start at the end of the charge cycle. Good thing is that according to CON[1] above, the BMS ignores very low currents depending on the calibration, so you could set it to balance even when it's actually still charging at below 1A. That said, it could be that under constant charge/discharge and when there is no resting time, the balancer could potentially have no time to work at all, and the pack could become completely unbalanced. This has happened once and the BMS cut the power successfully.

Here's a very useful bonus from me: There's an iOS application under development for these BMSs that actually works and displays stuff MUCH better than the android one: xiaoxiangBMS. It's on app store as well, for €1.00. A couple of features are still missing, but overall I use it much more frequently than the android one. Also has an Apple watch skin, which is ridiculous.
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#37
(05-09-2019, 07:55 AM)thanar Wrote: 2. The balancer works either: a. ONLY when charging or b. ONLY when NO current goes through. I was hoping that I would run the balancer 24/7, but this is NOT possible with this BMS. It runs either when charging (which is a bit useless, since second hand cell strings tend to voltage sag under load), or when RESTING, which means that balancing will start at the end of the charge cycle.

That's exactly how it should be working.

The reason why it, and almost all management systems wont attempt to balance under load is for the reason you have mentioned - voltage sag, which would be trying to hit a moving target.
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#38
As Sean said. Balancing during charge/discharge causes the balancer not knowing what and how to balance.
DCkiwi likes this post
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#39
*************
As Sean said. Balancing during charge/discharge causes the balancer not knowing what and how to balance.
*************

Is this true for the Batrium also?  

my powerwall is in a constant state of charge/discharge.

It is discharging 24/7. running 3 circuits within the house.

It is getting charged during daylilght (PV).

If your statement above is true.  Then we are back to the beginnings when Jehu posed the question 'are BMSs really needed?'.
Bob - has trouble wiring a 3-way switch Blush
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#40
BMS's are absolutely needed. Otherwise if a cell/pack went overvoltage (lets say you stopped consuming as much power and more current flowed into the battery), it could end very badly. A BMS would immediately start bleeding off the excess power that is overcharged, regardless if you are actively using it or not.

I would say a BMS has a harder time monitoring proper balance when the packs are below your top threshold. ie, if your cap is 4.0V, and between charge/discharge the pack barely reaches 3.9 - 3.95, it's possible that the few seconds that "could" occur that the pack jumps to 4.01V, the BMS could false trigger a bleed/balance mode.

I think the Batrium requires a period of time before that happens, though. So, if it's set to 5mins above 4.0V, that's when it'll start to balance. Otherwise, it ignores the times the voltage jumps over the trigger voltage for a few seconds. I could be wrong on that, though
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