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w0ss semi DIY powerwall V2
#61
(05-21-2020, 11:22 PM)w0ss Wrote: I never measured the wire so I can't say for sure. 2amp might be ok but I don't want to say yes and have it break something.

Maybe I should isolate the Lifepo4 and do another test.

I see the balance leads on the module are 24 AWG.  Your resettable fuses are what amperage, and how did you select that?

That would be very interesting if you can isolate the LG for capacity test  Smile

Thanks
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#62
According to wikipedia 24awg can handle 2.1amps. I picked fuses that trip @ 1.5Amps. I just made a guess... sounds like my guess was close enough Smile
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#63
(05-21-2020, 11:22 PM)w0ss Wrote: I never measured the wire so I can't say for sure. 2amp might be ok but I don't want to say yes and have it break something.

Here are a few closeups with a penny for scale.


My test earlier in the thread showed the following.

Discharge test of the bank from 4.08(3.57) to 3.40(2.98) volts per cell was ~425AH. Nominal is 550ah(378 LiPo/172ah LifePO4).

So I had ~78% capacity from 4.08 to 3.40. Since I had the LifePO4 pack in as well not sure how mush capacity it really has. I was also discharging it at probably .05c. Maybe I should isolate the Lifepo4 and do another test.
Thanks,
Will


Awesome! thanks for the photos. That helps.  Keep us posted if you try another capacity test.
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#64
I did a capacity test on just the 2 LG batteries I have. Went from 4.15v to 3.22v and had 91.5%(173AH) Cell voltages stayed pretty close until fairly low. I published a graph showing delta from min to max cell. The spike at the end is when I rebooted everything to try and fix some weirdness with my inverter. https://snapshot.raintank.io/dashboard/s...panelId=19
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#65
(05-24-2020, 12:48 PM)w0ss Wrote: I did a capacity test on just the 2 LG batteries I have. Went from 4.15v to 3.22v and had 91.5%(173AH)

91.5%...sounds promising for the unit I got.  Although one of my cells may potentially be problematic (not dead, but giving a low voltage reading).  Still studying it...awaiting some testing/charge/discharge devices.

Is your capacity result for one of your 2 batteries?  an average?
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#66
Both batteries were in parallel. I pulled out 345.338AH from the pair. Here is the Batrium screen showing the cells. They were still pretty even.
Keep in mind the 189AH rating is from 4.2 to 3.0 since I only went from 4.15 to 3.22 I left some capacity unused.

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#67
(05-24-2020, 05:37 PM)w0ss Wrote: Keep in mind the 189AH rating is from 4.2 to 3.0 since I only went from 4.15 to 3.22 I left some capacity unused.

You're probably close to full rated capacity.  Nice  Smile
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#68
(05-24-2020, 05:37 PM)w0ss Wrote: Both batteries were in parallel. I pulled out 345.338AH from the pair. Here is the Batrium screen showing the cells. They were still pretty even.
Keep in mind the 189AH rating is from 4.2 to 3.0 since I only went from 4.15 to 3.22 I left some capacity unused.


Wow, that's great news.  Thanks for sharing.
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#69
I'm curious what kind of fuses folks are using in their systems. I am planning to use a class T HRC fuse (200 or 225 amp) as a main fuse from my main positive buss bar to to the inverter; however, I would also like to place lower amperage fuses (100amp) coming off each of my batteries. I've read that HRC type fuses are preferable for lithium batteries to prevent arcing, but I'm not really finding HRC fuses in the 100amp range for DC. Ideally, I'd like to install these fuses as close to the battery terminals as possible. Therefore, I am considering these terminal fuses: https://www.amazon.com/Blue-Sea-Systems-...986&sr=8-1

That's assuming that they fit the module terminals properly. I still need to check. I've used these terminal fuses on lead-acid batteries on boats, but am not sure if if they are appropriate for lithium batteries. Just wondering what other folks are doing to fuse these modules.

Thanks!
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#70
THANK YOU!!!!   ---> @wOss - for your time in designing and working out the connector.  really appreciate you sharing your pcb design as well.  i didn't know designing and printing a pcb as a hobbiest was an option.  i just received my JLCPCB printed boards and connectors, etc. soldered everything up last night and installed this morning.

Do we know if the existing bms that came with the battery actively balances?  I bought from the original batch 6 months ago and was under the impression at the time of purchase that the bms was working. 

BH sold the next batch with the language changed saying the bms isn't working and we need to actively balance....just wondering

All of my cells stay balanced through cycling.  After sitting for a few months, zero change.  capacity avgs around 8kw. 

(BTW, I have 2 extra sets of board and connectors if anyone has interest)

thanks again @wOss

(06-11-2020, 07:32 PM)HydroGeo Wrote: I'm curious what kind of fuses folks are using in their systems.  I am planning to use a class T HRC fuse (200 or 225 amp) as a main fuse from my main positive buss bar to to the inverter; however, I would also like to place lower amperage fuses (100amp) coming off each of my batteries.  I've read that HRC type fuses are preferable for lithium batteries to prevent arcing, but I'm not really finding HRC fuses in the 100amp range for DC.  Ideally, I'd like to install these fuses as close to the battery terminals as possible.  Therefore, I am considering these terminal fuses:  https://www.amazon.com/Blue-Sea-Systems-...986&sr=8-1

That's assuming that they fit the module terminals properly. I still need to check. I've used these terminal fuses on lead-acid batteries on boats, but am not sure if if they are appropriate for lithium batteries. Just wondering what other folks are doing to fuse these modules.

Thanks!

@hydro
Would this be an option at the battery?  https://www.delcity.net/store/Del-City-M...3.h_195738  ----Your terminal fuses look nice and clean.
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