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Cheap Bluetooth BMS
#21
(02-08-2018, 08:07 PM)gpn Wrote: How is this working for you? It looks like what I have been wanting to do. I'd love to integrate this information from the bms into a grafana dashboard.

I'm building a portable 2kwh battery with 1kw inverter and solar/grid charging inputs. I have a raspberrypi with 7" touchscreen already that I was going to use for a display of battery state and function.

It is working just fine.

Grafana dashboard looks interesting. There would have to be an interface written between my software and the grafana dashboard.

Do you have any experience with writing Python code? I would be happy to help with this.

A quick look at how Grafana works makes me think that you would write code to generate a data sream that would output the data from my BMS software to say OpenTSDB. Interesting.

Simon
Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger https://github.com/simat/BatteryMonitor/wiki
Latronics 4kW Inverter, homemade MPPT controller
2 pushbikes using Bafang BBS-02 electric motor kits, 6 x 4s 5Ah (10Ah 12s2p) LiPo batteries, bluetooth BMS
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#22
Nope but I am planning on learning! But I will be a novice at best. I haven't written code seriously for about 12 years. Things have changed a bit...!

That is my understanding as well about grafana. I downloaded and flashed darometers grafana pi image and started to play with it. I ordered a 7s smart bluetooth bms as well. Look forward to getting that in the mail and firing it up. It seems that since we know the serial protocol for the smart bms it would be feasible to write a script to poll it and retrieve things like cell charge and load and then return that into a data stream that grafana could use and display.
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#23
(10-30-2017, 03:06 PM)karrak Wrote: As far as I can see you can configure just about everything, below is the configuration screen of the software provided

I came across that BMS also and is considering to buy it for my e-bike project. I checked the specs and according to it you can set the cut-off voltages in a rather narrow range, I think 4.22-4.28V for overcharge protection and 2.42-2.58V for overdischarge protection. I don’t see the reason for limiting those ranges so much and assume that you can set even other voltages, like 4.1V for charge and 3.0V for discharge cut-off. Can you check if it is possible and if the board performs appropriately? Another question: is it possible to limit the discharge current, for example buy a 30A BMS but set it to cut-off at 17A? Since the difference in price is not big I consider buying a BMS for higher current and with time upgrade the battery with more cells in parallel and use the same BMS.
Thanks in advance!
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#24
These values are hardware protection values, that's because you have typical, min and max values, by software you can of course set other values, I have 4.2 max and 3.15 min.


You can set too the overcurrent protection, I have set 80A and my BMS is 100A




Regards
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#25
(06-10-2018, 06:13 PM)jesusangel Wrote: These values are hardware protection values, that's because you have typical, min and max values, by software you can of course set other values, I have 4.2 max and 3.15 min.


You can set too the overcurrent protection, I have set 80A and my BMS is 100A




Regards

Thanks! Already bought the BMS and am looking forward to test it!
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#26
I read that they require the cells be matched to within 5mR?
Is this a disclaimer to avoid covering the BMS or because it actually doesn't do balancing?

Reasoning, if internal resistance are that closely matched than the resultant charge should be the same for each cell in the series..... thus this bms doesn't do balancing.

Anyone have these with recovered cells that is seeing it work correctly?

If so, if you set max V to 4.0, what is your ending voltage for each bank?
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#27
If the IR is so close and your packs doesn't self discharge you don't need a balancer.

I only had this BMS to over/under voltage and over current so I don't really know how balacing works, but 55mA is not enough if packs are not in good conditions, and my recovered cells aren't. Today after almost one year I've take appart first 40 cells of my pack 14 that was always the first to reach top and botton voltages, I have to change 7 cells.

You set under/over voltage by cell, so multiply by number of series to get the whole pack voltage. But if you set exactly that number in the inverter you can be sure that the overvoltage protection will trigger.

You must set the over voltage a little under whole_pack_V/series and set balance turn-on voltage a bit under too, in my config I start balancing only while charging and at 4.02 V

Regards
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#28
Hey jesusangel,

When your BMS stops charging the cells what is the typical Voltage of each series string? (do you see a large difference?)
What is you configuration 14s40p?

Are you charging you pack to 4.02V per string or till 4.2V
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#29
"When the inverter" stops charging at 57.8V, the cells are a little under 4.13 per cell, theoretically. But now are unbalanced, I'm testing and changing bad cells.




Watch Pack 14, it is the weakest (until yesterday I think, I've replaced some cells), under loads goes to the bottom and while charging goes to the top. Pack 13 and 12 are the next to check.

My config is 14s80p. 40 installed a yer ago, 40 a month ago.

My packs charge until 4.13V but the BMS starts ballancing at 4.02V
Regards
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#30
Question,
Since the BMS is programmable can a 14s unit be programmed for 7s or 4s?
I want one to start at 4s and work my way up a pack at a time.
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