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Issues with my first 18650 build (24v PCB 7s2p holders).

Badacatt

New Member
Joined
Jun 8, 2021
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2
Hello Everyone!



Let me begin by thanking all of you for posting your journey. I find countless hours of reading and I would like to think I am learning at a amazing clip thanks to you.

Forgive me if I have missed this posting somewhere.

I’m wanting to build a 24v 7s2p 18650 battery bank and I believe I’ve bought all of the right pieces still somehow I’m not having any luck.



Ive purchased 8 - 7S Power Wall Balanced PCB 18650 Battery Holders off of eBay. These are the double sided soldered PCB holders that connect with brass posts and a ribbon cable.

I also purchased a 60 amp BMS (3 x 20 amp

Bms units all soldered onto one board)

Additionally I purchased a State of Charge unit.



my plan was to purchase a few used 18650

Battery packs and then stock my PCBs with the salvaged 18650 I get from disassembling the used banks.

Everything was going to plan….pulled apart the used packs and i began populating the PCB holders. Once populated I began assembling the holders (installing and stacking them using the brass posts and the ribbon cables).

iI filled them up and installed the BMS unit and figured I was looking good.

This is when I ran into trouble. I’ve been trying to charge the assembled 24v 18650 PCB monster I made and I’m having no luck.

Am I over looking something. Do I need some special charger. The BMS and pcb units I purchased can be found here:






I was Under the impression that this be a mess unit and PCB holder set up would allow me too balance and charge all of my 18650s using the power input on the BMS….is this not the case?



I’ve bought two different lithium chargers and still I can’t get it to charge at all.



Any help

Would be greatly appreciated!



Thanks again guys,



Joshua from Oregon
 
Hard to say. Have you put each of those cells through something like an nice Xtar analyzing charger so you can weed out the garbage, and try to get as many as you can close to each other in both capacity and internal resistance?

If you don't do that, then your best bet is to stop playing with trash and purchase brand new cells. And run THOSE through the Xtar, charging before assembling.
 
i am doing something similar ,what i found is with these packs when charging they don't like a large amps ,i used a variable amp charger and the lowest setting was to too much ,plug in a small charge (1.5 amp) and charged up the packs fine ,so i think its the built in bms that is too small or just the design,faulty or just bad , i did take out the rack with the bms and seemed to have charged well no matter what charger i used
that being said i d i wouldn't want to run these packs without a bms
 
Last edited:
Hi,

I have a similar question. I've built exactly the same system as Badacatt. Fitted it with used 18650 batteries that I tested beforehand and all the batteries are of a similar capacity. I'm trying to charge it from solar panels (3x100W Renogy panels) and bought a Renogy Voyager (RV for short) and connected the battery pack to the RV. I managed to change the RV to lithium and it detected the pack without any problems including the correct voltage of the pack and the max voltage. So far so good. I then connected the solar panels up to the RV and it also detected the voltage coming in from the panels. However, the RV is refusing to charge the batteries from the the panels. Also, the RV is displaying the voltage from the panels but no amps. Just to make sure the RV was working I disconnected the 18650 pack and connected up a motor cycle battery to the RV. Changed all the settings so the RV was showing 12v Sealed battery and everything works fine; solar panels are charging the battery and the RV is displaying incoming voltage and amps from the solar panels. So has anyone successfully connected 18650 batteries to solar panels.

The reason I want to do this is I want to create a portable energy bank that I can charge up from the solar panels and then carry it round with me. Not easy with the motor cycle battery as it is heavy.

Regards, Tim
 
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