offgridfarmgineer
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- Jan 22, 2022
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Anyone else have thoughts on my post. Appreciate the excellent info here.
I haven't seen Solarod posting since maybe March,Anyone else have thoughts on my post. Appreciate the excellent info here.
I guess this as good as we can get on the SOK racks.I've done some calculations on a 5 battery parallel string and here are my results.
I'm using a value of 1 milliohm for the battery IR, and .1 milliohm for the link resistances which I think is more representative of what one gets with busbars rather than cable links. The load current is 100 amps. I'll reference this image:
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The red and black load connections are the standard diagonal connection, and that connection gives me the following theoretical battery currents in amps:
Example 26
23.5
18.2
16.6
18.2
23.5
Some have suggested moving the load connection toward the middle of the string. If the black load connection is moved to the point on the busbar adjacent to the negative terminal of battery 2, and the red load connection is moved to the point on the busbar adjacent to positive terminal of battery 4, we get these theoretical currents in amps:
Example 27
18.3
21.8
19.8
21.8
18.3
This is a substantial improvement. In some of the earlier hookups it was possible to get a perfect balance by connecting the load to the right place on the busbars between the last and next to last batteries in the string. Of course, I have tried to do that for this 5 battery string by varying the connection point. It isn't possible to get perfect balance, but it is possible to get improvement. I had to consider how to measure the improvement, and what seems reasonable is to get the least variation in the battery currents. I had my calculations include the standard deviation of the battery currents, and tried all the connections between the end batteries and the next-to-the-end batteries in 5% increments. For this 5 battery string, the connection which is 66% of the way from the last battery to the next battery inward gives the minimum variance in the battery currents. This would be a connection like the yellow/blue connection shown in the image above, at the 66% point. Here is the result of the 66% connection theoretical battery currents in amps:
Example 28
20.0
20.6
18.7
20.6
20.0
I haven't given up on the possibility of a perfect balance for this string, but no joy so far.![]()
Thanks for replying, yes two racks of 6. Looking back at post 57 he does cover banks of 6 and I plan to do it that way by drilling my own holes in the busbars for precise balancing. Would be interesting to see @Will Prowse do a geeky video on this subject. Tricky part may be controlling variables for a good test.I haven't seen Solarod posting since maybe March,
I assume your 12 100Ah packs are in two racks of 6 each? and if you have the racks, these will have bus bars for connection of each pack.
From his earlier comments, there will be no 'ideal' way to connect your main 4/0 feeders, close best option may be between 1/2 on pos and between 5/6 on neg (or vise versa) but this would be better with a four pack set up. There will be some imbalance with six batteries.
I would just try it and then monitor the packs for a while, after some cycling up and down the SOC range. See how it does.
I suppose if it doesn't work well, you can change your 12 batteries to 3 sets of 4.
In my own set up, where I have the ackward use of 2 100Ah packs plus 3 280 Ah packs, connecting the two 100's up as a pair (as if a 200 Ah pack) has worked out pretty well, and now that the bus bars have only four connections, I was able to shift the main pos and main neg to the 1/3 2/3 locations Solarod noted for a four battery set up on bus bars and this has been far better than where I started.
If you follow the link @Danke posted you will see the discussion retired EE 'Solarod' explained not only how to balance multiple batteries better, he also explained why. In PM he assisted me with balancing 6 packs - two 304Ah, two 280Ah and two 100Ah and I am eternally grateful.Hi,
I have this setup connected as such:
Four Battery Packs
I use 50mm² wires to interconnect them as shown.
Two Deye Hybrid Inverters
Deye1 has ~10% more Solar Panels than Deye2.
I use 35mm² to connect Inverters to Battery
Inverter Cables are 2meters, except for Deye1's Negative which is ~2.5m (Deye1 is ~0.5m farther away)
View attachment 238729
Are you sure it's not the beginning of this thread?It has been done, but I have no idea how to locate the particular thread where that analysis was carried out.
Ah... I missed that, but I do remember that thread.Are you sure it's not the beginning of this thread?
Hi,after reading the thread i still have some mouses in my head and that’s..
I am planning to have 3 banks from 2p16s lifepo4 304Ah(608Ah) connected to a tinned copper busbar and from there going to a t-class or HRC fuse with 2 95 mm(2/0 AWG) copper cables but now i need to find out where i can put my cables on to the busbar going to fuse,if i see this thread it’s not that easy…or do i overlook something
All battery’s have same manufacturer,age and gonna be balanced before connecting them
Thanks for help advice and recommendations
Thanks for replying, yes two racks of 6. Looking back at post 57 he does cover banks of 6 and I plan to do it that way by drilling my own holes in the busbars for precise balancing. Would be interesting to see @Will Prowse do a geeky video on this subject. Tricky part may be controlling variables for a good test.
Why not just try it out and see?Does anyone want to take a guess at the best configuration for 10 batteries with bus bars?
I ran for a month or so with both connected to one end. Once I was able to inspect the cell dayta I did see imbalance, and have now reconfigured to "diagonal", where I am seeing much closer balances.
However I am still seeing more current throughout 1&2 and less through 9&10, which I think is indicative of some wear from when they were initially misconfigured.
Initially: red: 1 black: 1
Now: red: 10 black : 1
I am wondering if I would get better performance from: red 7 black :3.
I had a similar nightmare trying to initially balance thirty lithium cells with very long and very crappy improvised busbars.Does anyone want to take a guess at the best configuration for 10 batteries with bus bars?
I ran for a month or so with both connected to one end. Once I was able to inspect the cell dayta I did see imbalance, and have now reconfigured to "diagonal", where I am seeing much closer balances.
However I am still seeing more current throughout 1&2 and less through 9&10, which I think is indicative of some wear from when they were initially misconfigured.
Initially: red: 1 black: 1
Now: red: 10 black : 1
I am wondering if I would get better performance from: red 7 black :3.
This should help: https://diysolarforum.com/threads/calculation-of-parallel-string-currents-addendum.94178/Does anyone want to take a guess at the best configuration for 10 batteries with bus bars?
I ran for a month or so with both connected to one end. Once I was able to inspect the cell dayta I did see imbalance, and have now reconfigured to "diagonal", where I am seeing much closer balances.
However I am still seeing more current throughout 1&2 and less through 9&10, which I think is indicative of some wear from when they were initially misconfigured.
Initially: red: 1 black: 1
Now: red: 10 black : 1
I am wondering if I would get better performance from: red 7 black :3.
Break up the string of thirty into 5 strings of 6. Use the optimum connection for a string of 6I had a similar nightmare trying to initially balance thirty lithium cells with very long and very crappy improvised busbars.
Diagonal connection should have worked in theory, but once everything becomes seriously unbalanced, its difficult to get it to recover quickly.
It probably will recover and settle down, but it might take a great many charge and discharge cycles to slowly get back.
I don't think you can really force it, just be very patient and keep an eye on progress.