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Don't underestimate this. I've directly observed the difference between cables and busbars. It adversely affected my BMS due to high voltage fluctuations in the cell-level readings, causing inappropriate balancing, SoC auto-adjustments, etc. I abandoned cables in favor of bus bars for these reasons.
I’m using custom 2/0 cables about ~5” in length and have been happy so far, but perhaps I’m not looking for the right thing.

Can you describe what measurements would expose the same problems you saw and what test / stress scenarios are most likely to expose those problems?

Reading your post more carefully, seems as though the primary issue is with BMS sense accuracy.

For my use case, I am bottom-balanced and use an active balancer only activated after battery is drained to ~3.125V / cell (25V) and no charge or discharge is occurring.

The battery never charges past 80% and I have no cells getting much past 3.350V (SCC never gets out of bulk/boost).

Since the passive balance of my BMS only kicks-in above 3.55V, I never charge up anywhere close to cell HVD of 3.75V nor discharge anywhere close to cell LVD of 2.1V, the cell sense of my BMS essentially never does anything (which my be why I’ve not seen the issues you ran into).

What was the magnitude of fluctuations you encountered in cell read and at what charge and/or discharge current levels?
 
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I’m using custom 2/0 cables about ~5” in length and have been happy so far, but perhaps I’m not looking for the right thing.

Can you describe what measurements would expose the same problems you saw and what test / stress scenarios are most likely to expose those problems?

Reading your post more carefully, seems as though the primary issue is with BMS sense accuracy.

For my use case, I am bottom-balanced and use an active balancer only activated after battery is drained to ~3.125V / cell (25V) and no charge or discharge is occurring.

The battery never charges past 80% and I have no cells getting much past 3.350V (SCC never gets out of bulk/boost).

Since the passive balance of my BMS only kicks-in above 3.55V, I never charge up anywhere close to cell HVD of 3.75V nor discharge anywhere close to cell LVD of 2.1V, the cell sense of my BMS essentially never does anything (which my be why I’ve not seen the issues you ran into).

What was the magnitude of fluctuations you encountered in cell read and at what charge and/or discharge current levels?

The Orion BMS voltage sensing is highly accurate and also high resolution. So it sees the voltage fluctuations quite easily ... even under mild load (0.1C) it would see something like 100mv swings (I'd have to go look at old graphs to get the exact numbers) -- enough that when a cell was really 3.4v the Orion would sometimes see 3.5v and start balancing (assuming balancing was configured to kick in at 3.5v), for example. There are some tweaks in the Orion config (e.g. don't start SoC drift unless the voltage parameters have been met for 30 seconds straight) which can help ... but not all of them (like balancing). I don't know how much this affects other BMSes.
 
The Orion BMS voltage sensing is highly accurate and also high resolution. So it sees the voltage fluctuations quite easily ... even under mild load (0.1C) it would see something like 100mv swings (I'd have to go look at old graphs to get the exact numbers)
Thanks. My BMS has no readout but I have a battery monitor hooked up that has +/-5mV sensitivity and I have occasionally seen instability in the readout.

I don’t think it was anywhere near 100mV but certainly more that 10mV or even 20mV.

I haven’t been much concerned when I’ve seen that happening since it hasn’t triggered any change in the BMS, but I’ll start tracking the behavior more closely since it appears it may be related to what you experienced…

-- enough that when a cell was really 3.4v the Orion would sometimes see 3.5v and start balancing (assuming balancing was configured to kick in at 3.5v), for example.
My maximum charge current is ~0.07C while my maximum discharge current is ~0.14C, but as I said, since I’m staying between 3.125V and 3.350V per cell (25V to 26.8V), even a 100mV swing is not going to trigger anything in the BMS.

But I am planning to push SOC limits once I eventually add another 1kW of panels, so I’d like to understand whether what I’m seeing is related to what you’ve experienced.

There are some tweaks in the Orion config (e.g. don't start SoC drift unless the voltage parameters have been met for 30 seconds straight) which can help ... but not all of them (like balancing). I don't know how much this affects other BMSes.
It sounds as though you have figured out what is causing the instability you’ve seen and I’d like to digest all that analysis - is there a thread somewhere you can PM me a link to?

Also, in terms of triggering behavior, is there a specific test condition that most easily triggers the instability you’ve seen?

My sense was that the instability I’ve seen was related to charging or discharging around to ‘mid-strep’ about halfway through the flats. Do I thought it had more to do with the precise SOC of the cells and whatever charge or discharge currents were flowing than anything associated with my 2/0 battery cables…
 
It sounds as though you have figured out what is causing the instability you’ve seen and I’d like to digest all that analysis - is there a thread somewhere you can PM me a link to?

Also, in terms of triggering behavior, is there a specific test condition that most easily triggers the instability you’ve seen?

My sense was that the instability I’ve seen was related to charging or discharging around to ‘mid-strep’ about halfway through the flats. Do I thought it had more to do with the precise SOC of the cells and whatever charge or discharge currents were flowing than anything associated with my 2/0 battery cables…

It's probably buried in the middle of my build thread somewhere. But charging (even .1C) above 80% SoC prematurely triggered the events. I wasn't sure what it was until I switched one of the connections to a bus bar instead of a cable and I couldn't believe my eyes.
 
It's probably buried in the middle of my build thread somewhere. But charging (even .1C) above 80% SoC prematurely triggered the events. I wasn't sure what it was until I switched one of the connections to a bus bar instead of a cable and I couldn't believe my eyes.
So the behavior you saw was only triggered at a high SOC when charging at 0.1C or higher? And was it consistent (went unstable whenever those conditions were reached)?

I’ll search through your build thread to try to find the discussion but is there a Cliff Notes version of your theory as to the cause?
 
Not aimed at anyone in particular but may I respectfully request that we try to keep this thread focused on this relatively new supplier Doncan ?

The topic drift seems to be accelerating.
I believe the name is Docan.
 
Not aimed at anyone in particular but may I respectfully request that we try to keep this thread focused on this relatively new supplier Doncan ?

The topic drift seems to be accelerating.
My apologies - I’ll follow up with conergi via PM…
 
Anyone else been asked to make final payment outside of paypal? Been working with Libby and she sent an email saying Docan's paypal has not been able to receive money and requested final payment with a bank transfer.
 
Libby? Don’t think that name has been mentioned before.

Have you been direct messaging jenny?
 
I used PayPal. Personally, I don't recommend you use anything but a major credit card via PayPal or another merchant payment system in case you need to dispute the charge. If you wire them money, you have no additional protection. I'm not saying they'd do anything nefarious and my experience with Docan was aweseome. But, I'd still suggest prudence on your part.
 
I used PayPal. Personally, I don't recommend you use anything but a major credit card via PayPal or another merchant payment system in case you need to dispute the charge. If you wire them money, you have no additional protection. I'm not saying they'd do anything nefarious and my experience with Docan was aweseome. But, I'd still suggest prudence on your part.
I tend to agree I just figured others might have had the same ask here.
 
Anyone else been asked to make final payment outside of paypal? Been working with Libby and she sent an email saying Docan's paypal has not been able to receive money and requested final payment with a bank transfer.
Not sure who llibby is. Most of us use @Amy Zheng or @Jenny Wu. I have used amy several times using paypal.. maybe one of these girls can chime in and clear this up. When using alibaba you can always request a person to deal with.
 
Are you paying a 2.6% fee on the Paypal platform to send the money? I like the added protection of using credit card but didn't want to foot the hefty fee. Has anyone paid in cash?
 
Are you paying a 2.6% fee on the Paypal platform to send the money? I like the added protection of using credit card but didn't want to foot the hefty fee. Has anyone paid in cash?
Hmmm... Amy just quoted me 5% paypal fee. Looking back, Michael Caro said 3% when I was first looking to buy through him. Is there some variation?
 
Hmmm... Amy just quoted me 5% paypal fee. Looking back, Michael Caro said 3% when I was first looking to buy through him. Is there some variation?
The 5% fee is if you want buyer protection. If you pay using freinds to freind pay pal charges 2.9% because it's a international transaction using a credit card. If you trust your supplier you can transfer the money from your bank into your PayPal account and there will be no fee.
 
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