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Electrodacus: are my expectations unreasonable?

noenegdod

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Im a bit on the OCD side and I like things to work well, as defined by me.

I decided to go with an electrodacus bms for several reasons but I did like the fact that it wasnt mass produced and made in North America.

Long story short, the individual cell voltages are not as accurate as I though they would be. What I mean by this is that when all the cells are the same voltage, the display on the electrodacus says there is a 10mv deviation between high and low. Connections are all solid. I have checked/cleaned them countless times.

I was told by Dacian that that is within spec for the components. When a manufacturer is pumping out components, yes, there is going to be tolerances but when an individual is assembling a device ( in the same way that we need to match cells to work together) I assumed that a conscientious individual would match components to work together in the device. Personally I dont really care if the BMS reads 10mv high or low, but the individual channels should all have the same deviation so the displayed values are representative of what they actually are relative to the others.

This was after I parallel top balanced the cells, configured into a 12v pack, discharged and re top balanced using the active balancer to see how close things were. (very minimal intervention required by the balancer) I checked cell voltages directly with 2 different DMM and the voltages were all identical.

Attach0001.jpg


So, again, I ask: Am I expecting too much?

The SBMS0 has a balance function. Should I disable that? The SBMS0 came with very conservatives settings and I plan to stick with those for operation but should I adjust the high and low cut offs to account for the outliers?

Thanks for any and all feedback.
 
I guess it depends on what you are trying to achieve. It wouldn’t effect any of the packs i have put together, but if you want to extract the absolute maximum capacity without worrying about cell longevity it might be an issue.
 
No Im not to worried about trying to maximize capacity. For what I am doing I have way more battery than I need. As I said, its kind of an OCD thing and its difficult to be objective. Thank you for your perspective.

Should I keep its balance feature operational or do you think I should turn it off?
 
honestly i rather a robot build it, if you think they are matching components your nuts, prolly the lowest paid guy builds them, with a build sheet, and if its a Friday, his work is prolly 10 times worse.
 
Long story short, the individual cell voltages are not as accurate as I though they would be. What I mean by this is that when all the cells are the same voltage, the display on the electrodacus says there is a 10mv deviation between high and low. Connections are all solid. I have checked/cleaned them countless times.

How do you determine cell voltage, so you can say they are the same?

0.010V/3.563V = 0.003%

Here's a Fluke DMM with spec no better than 0.5%. Of course, four readings will differ less than that, but could have that much total error.

Accuracy±([% of reading] + [counts]): 0.5% + 2


Inside the electrodacus, it could have similar accuracy specs, but either has hardware to multiplex between cells or ADC per cell. If multiplexed I would not expect offset. But if they had resistor dividers per channel then I would expect differences.

If any current was flowing, location of connection would matter. I would assume you would put scope probes on the taps, so voltage drop across busbar or connection isn't different between your reading and BMS.
 
honestly i rather a robot build it, if you think they are matching components your nuts, prolly the lowest paid guy builds them, with a build sheet, and if its a Friday, his work is prolly 10 times worse.
The Chinese balancer is certainly more accurate.
 
My 2c on Dacian's products. Really cool, really innovative, really particular to his specific use case and priorities, and one of those priorities being value/cost efficiency and cost/benefit. Keeping things low-ish cost, often takes precedence over other considerations from what I've seen. This will work for some people and not for others. I think of Dacian's projects as overgrown hobby projects (I dont mean that in a bad way, I mean it in a similar sense to many open source projects--he pursues what he wants to pursue, he listens to feedback and iterates based on user feedback, but like a free and open source project, will not always bend to the wants of users if they don't fit his design model/design goals.

I don't know if any of the above accounts for the slight lack of accuracy you are noticing or if the issue is widespread. but it might give some context to what I have come to see as his design philosophy.
 
LOL Ok, slow down for those that rode the short bus to electronics school o_O

How do you determine cell voltage, so you can say they are the same?
With a digital multi meter. Mine is not a fluke but I did have a friend measure it before I did the final test and although the actual voltage reading was a little lower than min, the cells all had the same reading.
0.010V/3.563V = 0.003%

Here's a Fluke DMM with spec no better than 0.5%. Of course, four readings will differ less than that, but could have that much total error.

Accuracy±([% of reading] + [counts]): 0.5% + 2


Inside the electrodacus, it could have similar accuracy specs, but either has hardware to multiplex between cells or ADC per cell. If multiplexed I would not expect offset. But if they had resistor dividers per channel then I would expect differences.

Lost me.

If any current was flowing, location of connection would matter. I would assume you would put scope probes on the taps, so voltage drop across busbar or connection isn't different between your reading and BMS.

No current was flowing. The picture above was taken 30 minutes after charger turned off.

I was measuring directly off the ring the BMS wires were crimped and soldered to, if that is what you meant.

Is what you are saying, in general, is that I should not worry about it?
 
My 2c on Dacian's products. Really cool, really innovative, really particular to his specific use case and priorities, and one of those priorities being value/cost efficiency and cost/benefit. Keeping things low-ish cost, often takes precedence over other considerations from what I've seen. This will work for some people and not for others. I think of Dacian's projects as overgrown hobby projects (I dont mean that in a bad way, I mean it in a similar sense to many open source projects--he pursues what he wants to pursue, he listens to feedback and iterates based on user feedback, but like a free and open source project, will not always bend to the wants of users if they don't fit his design model/design goals.

I don't know if any of the above accounts for the slight lack of accuracy you are noticing or if the issue is widespread. but it might give some context to what I have come to see as his design philosophy.
What he has built is basically exactly what I was wanting. It is lacking a little functionality for me in that when the temperature drops below the programmed limit, it stops charging (good) and discharging (sub-optimal for me) but I worked around it. From my little bit of interaction with him I would say you nailed it. He has a really hard time entertaining or accepting use outside of what he intended.

I am not here to rip on the guy or the product. I am fully aware I often have unrealistic/unpractical expectations on a lot of things and am just looking for some perspective and possibly some advise on how best to work around any potential issues.
 
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A Fluke meter had spec of 0.5% of reading (plus additional errors in least significant digits)
The BMS having a discrepancy between cells of 0.3% doesn't seem terrible in comparison.
That would be 10 mV difference you mentioned. Picture I only see 0.001V difference.

There might be a hardware implementation inside BMS which introduces variations you don't see when moving probes between terminals.
It might have an ADC able to read 3V or 5V. A multiplexer to switch between cells might have similar voltage limitation. The battery is about 14V, so one solution could be resistors to divide down the voltage, and each resistor could be a bit different.

Probably 10 mV isn't something to worry about. Just don't want balancer trying to balance something that is already balanced.
 
Picture I only see 0.001V difference.
in the picture, on the left is the app for the neey active balancer and it displays a 0.001v differential. On the right is the electrodacus display and the highest voltage is 3.579 and lowest is 3.569.
 
Is this BMS a design you can study, measure, modify?
If it is something like resistor tolerances, you might be able to improve it with 0.1%, 0.01% resistors. Or, paralleling a much higher value resistor to trim the value.
 
Is this BMS a design you can study, measure, modify?
If it is something like resistor tolerances, you might be able to improve it with 0.1%, 0.01% resistors. Or, paralleling a much higher value resistor to trim the value.
It is not a design I could study, measure or modify, that is for sure. Unfortunately I have no education or even rudimentary, bush league, novice/hobbyist electronics skills, equipment or the desire or time to learn.
 
I have doubts the consistent accuracy you are looking for exists in any of this equipment.
Leave the balancer on and keep one eye closed.
 
Thank you to everyone who replied. For now I think I am going to leave the balancer disabled and just do a full voltage balance with the active balancer occasionally to tune it back up.

Expectations lowered.
 
Expectations need to have a base. If every other BMS on the market was accurate to 0.001V, then your expectations would be reasonable. For a LiFePO4 system to operate “normally” (ie, as most people would actually use it), accuracy of 0.05V would be acceptable.

Use the Electrodacus as recommended for a while, and see how well it works for you.
 
Im a bit on the OCD side and I like things to work well, as defined by me.

I decided to go with an electrodacus bms for several reasons but I did like the fact that it wasnt mass produced and made in North America.

Long story short, the individual cell voltages are not as accurate as I though they would be. What I mean by this is that when all the cells are the same voltage, the display on the electrodacus says there is a 10mv deviation between high and low. Connections are all solid. I have checked/cleaned them countless times.

I was told by Dacian that that is within spec for the components. When a manufacturer is pumping out components, yes, there is going to be tolerances but when an individual is assembling a device ( in the same way that we need to match cells to work together) I assumed that a conscientious individual would match components to work together in the device. Personally I dont really care if the BMS reads 10mv high or low, but the individual channels should all have the same deviation so the displayed values are representative of what they actually are relative to the others.

This was after I parallel top balanced the cells, configured into a 12v pack, discharged and re top balanced using the active balancer to see how close things were. (very minimal intervention required by the balancer) I checked cell voltages directly with 2 different DMM and the voltages were all identical.

View attachment 72265


So, again, I ask: Am I expecting too much?

The SBMS0 has a balance function. Should I disable that? The SBMS0 came with very conservatives settings and I plan to stick with those for operation but should I adjust the high and low cut offs to account for the outliers?

Thanks for any and all feedback.
I have two rebranded “Neey” clones and both are dead on for voltage and crazy fast for balance. It will bring it to .001 or better lol before it goes to standby. The only thing is they are early version + apple app and the sleep/start voltage is nuts so I have to turn it on through the app.(above 3.4V). To get the desired “EqualizationVol” feature in the app you need a later version+Android.
 
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