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German Powerwall 280xLG 18650MJ1 7s40p+ 450Wp Balcony PV System and a small question
#21
(04-07-2019, 09:34 AM)drbacke Wrote: Wow that was a *!"$= bunch of work. I cleaned every battery twice (mechanical and chemical) and had to rewrap them all.
But now I have the most colourfull Powerwall in the world i guess ^^
If you are interested in the process of 2 days stupid cleaning batteries:

At least you found out before it caused any harm. Especially being new batteries.
Korishan likes this post
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#22
(04-07-2019, 11:40 PM)Geek Wrote:
(04-07-2019, 09:34 AM)drbacke Wrote: Wow that was a *!"$= bunch of work. I cleaned every battery twice (mechanical and chemical) and had to rewrap them all.
But now I have the most colourfull Powerwall in the world i guess ^^
If you are interested in the process of 2 days stupid cleaning batteries:

At least you found out before it caused any harm. Especially being new batteries.

Absoluty! Nevertheless my hands hurt now  Big Grin
I can't say it often enough, thanks again for the tip :-)

The next project will be the extension with used batteries and try to add some fire resistant plates. To get a little more safety in the event of fire. At the moment I have a fire extinguisher for lithium and a fireclay pate under the pack.

Anything important to know about used 18650 batteries? 
I know about the voltage range (will use 3.5V-4.1) and the load current will be maximum 0.375A for each battery.
Only original cells.
And of course I will not use the flux again ^^
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#23
You should check them for capacity and self discharge. Also while charging the batteries you should check temperature. Measuring of the temperature would be the best but you can check once or twice with your hands. Important to find heaters, everything getting over 40 degrees °C has to go to the bin (My personal opinion!). But here are a lot of threads with tips and tricks about harvesting and testing.

What do you mean with load current? Charge or discharge current? Load is something else I think (German: Last) !? I test my cells with 1A charge and discharge. So I could go that high in the powerwall, too. But maybe for safety the maximum is 0.5 A for both charging and discharging. And yes a voltage range from 3,5 to 4,1 V is good for cycle life you could even go to 4V or 3.95V. I think deeper will give us more problems.

Do you have tester / charger already? I'm from germany and i got several chargers for sale. https://secondlifestorage.com/t-SELLING-...in-Germany maybe these could be interesting for you? Especially the VP4Plus Dragon units? They are quite new and i got up to 4 of them ;-)
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#24
(04-08-2019, 06:45 AM)Maniac_Powerwall Wrote: You should check them for capacity and self discharge. Also while charging the batteries you should check temperature. Measuring of the temperature would be the best but you can check once or twice with your hands. Important to find heaters, everything getting over 40 degrees °C  has to go to the bin (My personal opinion!). But here are a lot of threads with tips and tricks about harvesting and testing.

What do you mean with load current? Charge or discharge current? Load is something else I think (German: Last) !? I test my cells with 1A charge and discharge. So I could go that high in the powerwall, too. But maybe for safety the maximum is 0.5 A for both charging and discharging. And yes a voltage range from 3,5 to 4,1 V is good for cycle life you could even go to 4V or 3.95V. I think deeper will give us more problems.

Do you have tester / charger already? I'm from germany and i got several chargers for sale. https://secondlifestorage.com/t-SELLING-...in-Germany maybe these could be interesting for you? Especially the VP4Plus Dragon units? They are quite new and i got up to 4 of them ;-)

I will buy already checked batteries. But I will test them once again and also self discharge and heating additionally. Better to check it once again by myself. 
Loading = Ladevorgang/Laden, but you are right charging is the correct term. I meant maximum possible charging current per cell (from the panels).

Yes I'm interested in your chargers. I will send you a message.
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#25
As said if you test your cells at 1A you could also go up to 1A per cell while charging from solar. Half would be save enough, if you want it safe and for sure the slower you charge the better for the cells.
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#26
Ok I got my first notebook batteries and two of them are already sleeping fully charged in a box for 2 weeks till now. 9 batteries are still in the capacity tester and will be stored in the box tomorrow ^^
66 notebook battery packs on the way, so a lot of work.

Maybe its time for another question:
If I finished to build up the new packs (7x 40-50p) and want to connect one new pack to an existing 40p pack in parallel. How much difference in the voltage is acceptable? I think the difference must be quite close, because one pack can deliver over 200A. 
So how to connect them safely without burning the house down?
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#27
My active packs basically reach any voltage during the day while charging / discharging, hence its only a matter of timing. I don’t allow more than 100mV (per cell) difference when connecting a pack.
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#28
(04-11-2019, 06:41 AM)stevelectric Wrote: My active packs basically reach any voltage during the day while charging / discharging, hence its only a matter of timing. I don’t allow more than 100mV (per cell) difference when connecting a pack.

I see what you mean. In my case I don't reach any voltage during the day, but maybe the best is to load them externally to a defined voltage and connect them balanced. Or maybe I can use my active balancers to do this. 
I think it should be also better to do this at a low SOC, since the energy content is lower. Or am I wrong?
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#29
I think I somehow did not get your question right. A battery (pack) in my setup is 7s40p. After building it will have around 4.1V per cell, 28.7 at the terminals since the cells are almost fully charged. So I just need to wait until the existing packs to reach that same voltage which will happen some sunny day after noon to connect the new pack.

Balancing happens inside of the pack in my setup, therefore I don't need to check each parallel block voltage. But since a newly built pack should not be terribly disbalanced, I would not expect issues here.

I made good experiences joining them on high SoC, I don't think it matters much. Many BMS only balance on high SoC. My guess would be that the difference on voltages is less important on high SoC, therefore the equalizing currents are smaller. Between 3.6V and 3.7V the SoC difference is larger than between 4.1V and 4.2V.
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#30
(04-12-2019, 09:50 AM)stevelectric Wrote: I think I somehow did not get your question right. A battery (pack) in my setup is 7s40p. After building it will have around 4.1V per cell, 28.7 at the terminals since the cells are almost fully charged. So I just need to wait until the existing packs to reach that same voltage which will happen some sunny day after noon to connect the new pack.

Balancing happens inside of the pack in my setup, therefore I don't need to check each parallel block voltage. But since a newly built pack should not be terribly disbalanced, I would not expect issues here.

I made good experiences joining them on high SoC, I don't think it matters much. Many BMS only balance on high SoC. My guess would be that the difference on voltages is less important on high SoC, therefore the equalizing currents are smaller. Between 3.6V and 3.7V the SoC difference is larger than between 4.1V and 4.2V.

Ok, you connected an existing 7s40p battery to another one in parallel?
In my case I use active balancing for each of the 7 p40 pack and want to use it further. So I need to upgrade the 7s40p battery to (for example) 7s80p.
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