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DIY 100ah lithium battery


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#11 kmcintyre

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Posted 15 June 2021 - 12:04 PM

An update. I put in an order through alibaba for 4 of the 120ah cells that member kmcintyre used. This was my first experience with alibaba. I received only one response from China suppliers. The cost was $43 a piece plus $114 to get it here making a total around $280. Prices are up. Add in a BMS and cost for a DIY is approaching the sale price on the Renogy battery and the SOK that Will Prowse gave favorable reviews. Note, these are both 100ah batteries.

 

I considered the SOK because it can be disassembled and parts replaced.

 

I'm going ahead with a DIY mainly for the learning experience and I like to understand how things work.

 

Thanks all for the information and insights.

 

I think you'll like them.  It'll take a while to get them.

The next thing will be getting the app installed and figuring out all the settings assuming you got the bluetooth BMS.

 

I'm not sure what prices you see for those other battery packs on sale but you should be around $325 for your 120ah cells and BMS which is about what I have spent on AGM batteries.

 

Have fun!

 

Kevin


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#12 Lunch

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Posted 10 August 2021 - 09:17 AM

Hey Ski3pin,

 

Just saw this thread. Will be following your DIY project. If successful, maybe we can work on the next one together. Remember that table top you helped me build? When Li-Polymer prices drop and life cycles increase, we can build another table top that also houses a  LI-Po battery.

 

I was going to go the DIY route but was worried about the BMS. I was pretty confident about cell quality but not about third party BMS and BMS systems. Just too much at stake and I knew that I would always worry about it. I know lots of people have successfully incorporated these BMS' into their builds and I am happy for them. I guess I am just a little more risk averse.

 

I called up Battleborn and spoke with the chief engineer (well, I assume he was an engineer b/c he didn't usually talk to people). I asked him lots of technical questions about the cells and BMS and he answered them pretty quickly and with a lot of confidence. And he gave me a nice discount. Good enough for me.

 

Another decision factor was the resale value. Battleborn claims 3k-5k life cycles. It's common practice in the industry to understate battery service life (BB even recognizes the actual lifetime cycles will likely be higher on their webpage). I assume in their testing they discharged to 80% DOD (lower than I ever get) and charged faster than I do (0.3C on DC-DC and 0.4C on charger/inverter). So, maybe my battery will last even longer, say 6k cycles minimum. So, in theory, I could pull ~80 A every day for almost 16.5 years or, more realistically, 20 Ah about 70 times/yr for about a billion years. So, when a new battery technology leader emerges I will be first in line and will hopefully be able to sell my current BB.

 

BTW, I don't usually watch Will's vids (energy level is a little too high for me). But it was cool to see him dissect the BB and give it a positive review. 


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#13 lmwilco1

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Posted 10 August 2021 - 02:25 PM

Have  you already ordered a BMS? I have an extra one you can have if you pay shipping. It is rated at 100A draw and has bluetooth.

 

Link to the BMS: https://batteryhooku...=2267412.b1bf25

 

Louis


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#14 ski3pin

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Posted 10 August 2021 - 04:22 PM

Have  you already ordered a BMS? I have an extra one you can have if you pay shipping. It is rated at 100A draw and has bluetooth.

 

Link to the BMS: https://batteryhooku...=2267412.b1bf25

 

Louis

 

Louis, thank you but mine arrived weeks ago. That is a very kind offer and I appreciate it.


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#15 ski3pin

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Posted 10 August 2021 - 04:28 PM

Hey Ski3pin,

 

Just saw this thread. Will be following your DIY project. If successful, maybe we can work on the next one together. Remember that table top you helped me build? When Li-Polymer prices drop and life cycles increase, we can build another table top that also houses a  LI-Po battery.

 

I was going to go the DIY route but was worried about the BMS. I was pretty confident about cell quality but not about third party BMS and BMS systems. Just too much at stake and I knew that I would always worry about it. I know lots of people have successfully incorporated these BMS' into their builds and I am happy for them. I guess I am just a little more risk averse.

 

I called up Battleborn and spoke with the chief engineer (well, I assume he was an engineer b/c he didn't usually talk to people). I asked him lots of technical questions about the cells and BMS and he answered them pretty quickly and with a lot of confidence. And he gave me a nice discount. Good enough for me.

 

Another decision factor was the resale value. Battleborn claims 3k-5k life cycles. It's common practice in the industry to understate battery service life (BB even recognizes the actual lifetime cycles will likely be higher on their webpage). I assume in their testing they discharged to 80% DOD (lower than I ever get) and charged faster than I do (0.3C on DC-DC and 0.4C on charger/inverter). So, maybe my battery will last even longer, say 6k cycles minimum. So, in theory, I could pull ~80 A every day for almost 16.5 years or, more realistically, 20 Ah about 70 times/yr for about a billion years. So, when a new battery technology leader emerges I will be first in line and will hopefully be able to sell my current BB.

 

BTW, I don't usually watch Will's vids (energy level is a little too high for me). But it was cool to see him dissect the BB and give it a positive review. 

 

Mr. Lunch, I expect the chief engineer at Battleborn was very pleased to speak with someone with your credentials, expertise and background.

 

I have all the components now except for the cells.

 

I'd be happy to play with electricity with you. Anytime! :)

 

But first off, you two need to tag along with Julie and me on a Death Valley area adventure in the winter.

:) 


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#16 ski3pin

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Posted 22 September 2021 - 04:48 PM

An update -

 

I have assembled my first DIY lithium 12v battery with 4 3.2V 120ah cells using xiaoxiang 4S 120A Li-ion BMS. I followed the overkill solar directions. I've top balanced successfully and then connected the BMS and final assembly. I have this issue - the cell voltage measures 13.6V at the cell terminals but through the BMS at the final terminals the voltage is 11.9V. The android BMS app confirms battery voltage is 13.6V. I've double checked the balance wires and overall assembly and can find nothing. What I'm I missing, what should I look for?

 

This morning I redid each crimped connector on the balance leads and the push connector is fully seated with no change to the low voltage issue.

 

A few photos of the project.

 

 

 

Batteries-Sept2021-016-copy.jpg

 

 

 

 

 

Batteries-Sept2021-015-copy.jpg

 

 

 

 

 

Batteries-Sept2021-014-copy.jpg

 

 

 

 

Batteries-Sept2021-013-copy.jpg

 

 

 

 

Batteries-Sept2021-012-copy.jpg

 

 

 

 

Batteries-Sept2021-011-copy.jpg

 

 


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#17 rando

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Posted 22 September 2021 - 07:04 PM

Your BMS is probably off.    When you first connect the cells, it doesn't know what the SOC is so it may assume it is too low and turn off.   Configure it through the app, and then either force it on through the app, or charge the pack for a bit, which will turn it on.   It will take a while to sync up the BMS. 

 

PS Very nice job on your pack!


Edited by rando, 22 September 2021 - 07:41 PM.

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#18 ski3pin

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Posted 24 September 2021 - 12:01 AM

Your BMS is probably off.    When you first connect the cells, it doesn't know what the SOC is so it may assume it is too low and turn off.   Configure it through the app, and then either force it on through the app, or charge the pack for a bit, which will turn it on.   It will take a while to sync up the BMS. 

 

PS Very nice job on your pack!

 

Thanks Rando! I put a charge on the battery last evening - 14.4V until the DC unit's amps were near .0 and then disconnected. I checked the battery this morning and the voltage is still low - the same as above - through the BMS.

 

When you say "a while" above, how long to sync up the BMS.

 

For anyone who enjoys data, here is what the BMS app is showing -

 

 

 

Batteries-Sep2021-024-copy.jpg

 

 

 

 

 

Batteries-Sep2021-025-copy.jpg

 

 

 

 

 

Batteries-Sep2021-026-copy.jpg

 

 

 

 

 

Batteries-Sep2021-027-copy.jpg

 

 

 

 

 

Batteries-Sep2021-028-copy.jpg

 

 

 

 

 

Batteries-Sep2021-029-copy.jpg

 

 

 

 

 

Batteries-Sep2021-030-copy.jpg

 

 

 

 

 

Batteries-Sep2021-031-copy.jpg

 

 

 

 

 


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#19 rando

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Posted 24 September 2021 - 03:01 AM

That is a different interface than the one on my BMS, however everything looks to be in order and the battery and BMS seem to be in sync ie the battery is fully charged with a 13.6V resting voltage and the BMS thinks the battery is fully charged. 

 

Silly question, but have you tried loading the battery?  Apply a load to the output and see what the voltage is.


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#20 ski3pin

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Posted 24 September 2021 - 03:07 PM

Not a silly question, Rando. I was at the point in the build process to do a capacity test of the battery - a la Will Prowse - when I discovered the discrepancy in voltage at the final terminals. I will hook it up today to see what happens.  :) 

 

Thanks for your time in looking this over. I appreciate it.


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