bluetooth BMS?

Batteries, Chargers, and Battery Management Systems.
dh68
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Re: bluetooth BMS?

Post by dh68 » Dec 04, 2017 5:46 am

Hello there!
I have put together 13S5P battery with Sanyo/Panasonic NRC18650GA cells with smart bluetooth BMS. The BMS arrived with basic settings already there (see picture). this is fine, but I would like to change this seetings to achive longer cycle life of the pack and to adjuts the BMS to the GA cells. I was thinking to limit useful voltage between 3,1 to 4,1 V? Which parameters should I change? I am not very familiar with this, so I would apperiate your help very much.
THX
PC tool User instructions.pdf
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cycborg
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Re: bluetooth BMS?

Post by cycborg » Dec 04, 2017 10:55 am

dh68 wrote:
Dec 04, 2017 5:46 am
Hello there!
I have put together 13S5P battery with Sanyo/Panasonic NRC18650GA cells with smart bluetooth BMS. The BMS arrived with basic settings already there (see picture). this is fine, but I would like to change this seetings to achive longer cycle life of the pack and to adjuts the BMS to the GA cells. I was thinking to limit useful voltage between 3,1 to 4,1 V? Which parameters should I change? I am not very familiar with this, so I would apperiate your help very much.
The BMS voltage limits should be set outside the normal operating range. Normally, the charge termination voltage should be determined by the charger, and the low-voltage cutoff should be handled by the controller. If you implement these limits in the BMS, it will shut down charging before actually reaching the desired voltage (due to excess voltage across the battery's internal resistance), and it will disconnect from the controller while there's still capacity in the battery, as the voltage dips when you apply the throttle. It looks like you can partly avoid the second problem in this BMS by adjusting the "Delay" parameters, but it's still not ideal.

Usually it's possible to adjust the termination voltage of even inexpensive chargers. The controller LVC may not be adjustable, so in this case you'd need to have some sort of display so you can keep an eye on the voltage. Read the voltage when the throttle has been at zero for several seconds, to allow the battery time to recover from being loaded.

The function of the BMS is to protect the battery from conditions outside normal operation. For example, a runaway charger that doesn't stop at the termination voltage, an out-of-balance cell group that hits its termination voltage before the rest of the pack, a short circuit, or a load (e.g. lights) that's inadvertently left connected when the bike is in the garage.

All that said, whatever limits you decide on, the CellOVP, CellUVP, PackOVP, and PackUVP are the relevant parameters. If it were me, I'd just rely on the cell-level protection and set the pack levels to something the pack would never reach, but in some cases there may be legitimate reasons to use these.

See also my post about 5 back regarding balancing.

dh68
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Re: bluetooth BMS?

Post by dh68 » Dec 05, 2017 9:20 am

Thanks for help. I need some time to think it over. I'll leave it as it is till then.

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Re: bluetooth BMS?

Post by cycborg » Dec 06, 2017 10:58 am

dh68 wrote:
Dec 05, 2017 9:20 am
Thanks for help. I need some time to think it over. I'll leave it as it is till then.
BTW thanks for posting the instructions. It's been hard to find documentation on these.

General question for those who have used these - have you gotten them to work with arbitrary numbers of cell groups? I'm thinking of getting a 20s model for an 18s battery, but I messaged the Aliexpress vendor in the first post and they said this is not possible. However, Inwo says it works if you set the Pack Num parameter. No detail beyond that, though. If you've done this, what parameters did you need to set other than Pack Num? Which balance taps are used?

dh68
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Re: bluetooth BMS?

Post by dh68 » Dec 07, 2017 9:13 am


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cycborg
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Re: bluetooth BMS?

Post by cycborg » Dec 07, 2017 11:21 am

dh68 wrote:
Dec 07, 2017 9:13 am
Well, it's all here: http://www.lithiumbatterypcb.com/%E5%8D ... -download/
Thanks, that's helpful. It looks like each model can be configured within a range of cell groups by short-circuiting specific pairs of balance taps. Turns out the one I was looking at is for 20s-30s so 18s wouldn't work, but there's another model listed on the Aliexpress site as 16s but it looks like it can be configured for anything from 16s-20s. I have another message in to them to verify this.

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Re: bluetooth BMS?

Post by dh68 » Dec 13, 2017 9:24 am

I've got this answer after I send my question to the seller/producer (see picture with new settings) although he didn't take my picture with real data as background. Still I don't understand the purpose of those "release" input boxes.
Shouldn't be adjusted settings in the "Capacity Setting" on the right side of the window, too?
How can I calcultate the new capacity of the battery?
Settings 3.1V-4.1 V from seller.jpg
Settings 3.1V-4.1 V from seller.jpg (113.44 KiB) Viewed 53 times
Thanks everybody.

The specifications for NCR18650GA are:
- Rated Capacity: 3300mAh (0.67A discharge at 20°C)
- Minimum Capacity: 3350mAh (0.67A discharge at 25°C)
- Typical Capacity: 3450mAh (Reference only)
- Nominal Voltage: 3.6V
- Discharging End Voltage: 2.5V
- Charging Current (Std.): 1475mA (other source 1675A)
- Charging Voltage: 4.20V (+-0.03V)
- Charging Time (Std.): 4.5 hours (other source 4 hours)
- Continuous Discharging Current (Max.): 10A

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Re: bluetooth BMS?

Post by Buk___ » Dec 13, 2017 9:49 am

dh68 wrote:
Dec 13, 2017 9:24 am
Still I don't understand the purpose of those "release" input boxes.
I would assume it means that for over-voltage (CellOVF), the protection cuts in if the voltage goes above 4250, and releases again when it drops back below 4100.

For under-voltage (CellUVF) the protection cuts in when the voltage drops below 2700, and releases again when it move back above 3000.

And so on.

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cycborg
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Re: bluetooth BMS?

Post by cycborg » Dec 13, 2017 10:37 am

dh68 wrote:
Dec 13, 2017 9:24 am
How can I calcultate the new capacity of the battery?
thunderheart recently posted some discharge curves for the GA; you should be able to estimate capacity from that. Look at the lowest-current curve and calculate capacity between 4.1 and 3.1 V, then multiply by your parallel count.

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Re: bluetooth BMS?

Post by dh68 » Dec 14, 2017 6:23 am

Thank you for both replies. About the "releases" - it looks logical now.

My TSDZ2 motor is 500 W/48 V, so it would take ~10A at max although there is "15A" label somewhere inside (maybe is it 750W!?). So if I have 13s5p battery, that would be 10to15A/5p=2to3A per cell max. This means, that is better to look somewhere near the red 2A curve in the discharge chart?
In that case I get these estimations:
per cell-___~3A___-____2A___
3,1V ---- 2930mAh - 3050mAh
3,0V ---- 3080mAh - 3140mAh

per 5p-___~3A___-____2A___
3,1V --- 14650mAh - 15250mAh
3,0V --- 15400mAh - 15700mAh

The "logic" about the "Capacity Setting" box in the window is still "black box" :?

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