Endless Sphere

From left to right: Main's 240VAC goes into a Voltage (V) stabilized and current limited (A) power supply that outputs 12V. These 12V feed the BMS of the 3s li-ion battery (around 10Ah). The boost converter comes only into play when there's a power outage - though it's inline all the time (convertin...

Just wondering: Is there still some development done? I don't see any progress or anything since teklektik left the forum.
Is it just me that has this feeling?

My plan is to let it all have the same level. Output, Input and BMS are connected all together. Input will have a diode to avoid current flow into the power supply. I will draw a circuit.

I think something like this should be fine feeding the battery. Limited to 1A charging they will surely survive :) https://www.aliexpress.com/item/5A-Adjustable-Power-CC-CV-2-in-1-XL4015-Step-down-Charge-Module-LED-Driver-Voltmeter/32964535758.html?spm=2114.10010108.1000013.2.381651d2udtbHA&gps-id=p...

I'm aware of the calibration procedure of the CA. And this is why i assume that the BB is broken. Sometimes it shows the correct voltage and zero Nm at standstill. Sometimes it's way off. And the Sempu doesn't need calibration - it's a fixed and calibrated voltage for 0Nm. If you change that, the CA...

These little boards claims 4A output. Sure this is chinese amps, and it will not work converting 5V to 30V@4A, as it's the input current AND the output current that count. But if you say your working battery range is from 9V to 12V and your output is 2A@12V you should be fine. You can then decide if...

john61ct wrote: ↑

Jun 13 2019 6:11pm

PSU ordinarily feeds loads, and keep backup 3S batt charged at 5A and 3.8Vpc, in a power cut, millisecond cutover to the backup.

Setting the power supply to 3.9V would give the same result? Wouldn't it? I would like to keep it as simple and small as possible (and cost effective of course )

Why not take an existing UPS unit sold for electronics backup, and replace the SLA battery with a lithium pack with a nominal ~12.9 volts, with a BMS in line between the UPS and the pack, I think... Good idea, but probably to bulky, and this then again means i'd need many seperate power supplies as...

Ah ok. Didn't think about that. I need let's say 2A for all connected devices. The power supply will be able of let's say 4A. If no device is connected those 4A would go directly to the battery. The 6p pack makes this 750mA per cell. That's 0.3C. Worst case. Normally the max charge is 2A as the othe...

Everthing agreed on, and nothing i will argue about. I should have been more precise when i asked about your thoughts. It was not about chemistry or batteries in such, but about the layout, or the practical approach. Feeding the devices and the BMS with the same power line at the same time shouldn't...

Btw: I could also just charge to like 3.9V per cell which is close to storage voltage. This would make it last very long. But then i'm losing capacity - which is no big deal, i may just add one or more cells in parallel.

Battery life is not really a concern. If you don't mind finding out your batteries are shot when power goes out - then you don't need a UPS. I'm with your arguements, but your heavily exaggerating. It's really not the case that batteries will just fail from one day to the other just because they ar...

Battery life is not really a concern. I got enough of those cells. And 4V/cell is not fully charged (well almost). So it should last quite a while. If they are dead i can replace the pack. Buying Lifepo4 for this application is a waste of money - in MY case. I will also need to add some dc/dc conver...

I plan to install a new smart home security systems. Therefore several low voltage devices need to stay powered during a power outage. This includes cable modem, switch, smart home hub and the security system itself. All of them run off 5/12V. So i thought of building a small UPS from 18650 batterie...

It STARTS, but it doesn't STOP if cell voltage falls BELOW that value. At least it seems it didn't do with my battery. Then how is this useful? Seems to me the "stopping" is an indispensable part of the balancing process. Theory is one thing. Reality a second one. I don't know if my assumptions are...

BotoXbz wrote: ↑

Jun 11 2019 3:35am

It clearly says "Start Voltage: 3900 mV", it'll only balance above that voltage.

It STARTS, but it doesn't STOP if cell voltage falls BELOW that value. At least it seems it didn't do with my battery.

No. It's a T4.3 type. I contacted Sempu and they gave tech support, and will send a replacement for free. This is what they said: " The bad reason is that the internal electronic components are not in good contact with each other. In the future, we will strengthen the solder joint detection of elect...

What would be advisable settings for 42V pack? Its 14AH. this is what i have atm: Untitled.png I guess this screenshot shows why your last battery FAILED. IMHO if you got "balance" activated it will balance ALL THE TIME. It will try to reach your 30mV delta ALL THE TIME. So it will never really sle...

john61ct wrote: ↑

Jun 05 2019 10:16pm

So 20% of the capacity remaining at 3.3V loaded is not "600mA left" but 600mAh.

Damnit. Such a mistake happening to me... Me, that constantly corrects other people's posts about SE units, and urges them to use the correct one.
Shame on me! Of course it's mAh.

john61ct wrote: ↑

Jun 04 2019 4:44pm

In practice even 3.1Vpc is empty, insignificant range left after that

Normally I'd say correct, but this cell has a lower discharge cut off then other cells. Where you normally got till 3.0V max, this cells goes to 2.8V. But of course this is not where the meat is anymore.

So does a 2.5V discharge cutoff mean that a 14S pack can be used down to 39.8V and still be at 20%? (4.2-2.5 = 1.7V/cell total capacity, 0.34V = 20% capacity. 2.5V x 14 = 35V at cutoff, .34x14 = 4.*V for 20% residual capacity) Asking because 42V seems to be a default LVC for 14S and that would be 3...

I did some more investigation and the sensor gives some strange readings. First of all it now shows 1.88V resting voltage and 20Nm w/o touching the pedals (where as it was 1.5V before). When i set sensor to "custom" i can reset the ZERO torque voltage, and then it shows 0Nm again. And when i ride it...

You don't say which version of Sempu you're using. Maybe post a picture as naming differs quite a bit as well. I got a T4 and it behaves strangely as well. But not as you write. Wiring is straight forward as well, and not much to do wrong in my eyes. I also can't imaging how you could produce HW whi...