26650 build

rearden

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Feb 11, 2019
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26
I am starting my build. I started collecting 18650 but since have come across several hundred 26650 LiFePo in good condition so I am moving to those.

I purchased 4x4 battery holders on ebay.
started with 99 Sb .3 Ag .7 Cu solder and am now trying 97 Sb and 3 Ag
I am using 6.3A slow blow glass fuses soldered to the positive side and 26AWG on the negative side.
I have 12 AWG with up to 16 batteries connected to each strand. The wires will then be connected together at a 1/0 AWG lug.
The pos and neg lugs will be separated vertically with enough length to connect to the appropriate lug on the next battery, come off the front and be expandable toward the rear of the battery by adding another 12g run toward the lug (similar to glubux)
I have not decided upon the inverter, solar charge controller or BMS yet. The goal is to store excess solar energy and use it at night, on demand or grid down. I need advice on those. This design would call for one large BMS.
As each battery will be approx 3V, I will have a 8s or 16-18s and will go as deep as my shelf space can handle as I collect batteries. I think I have enough batteries for 32p at 16s initially.
I am finding that construction is taking longer and costing more than I expected.

Please give constructive criticism: Safety, design, technique, materials, etc. It is early in the construction phase and I can make changes.

rearden


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Redpacket

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Feb 28, 2018
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1,247
Looks generally OK, layout looks a bit variable, you might want thicker busbar cable, eg 3 strands twisted together.
Using cable ties or temp insulated wire down the holes between cells might help keep things in place as you build.

My system is LiFePo4 :)
 

rearden

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Feb 11, 2019
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26
Redpacket said:
Looks generally OK, layout looks a bit variable, you might want thicker busbar cable, eg 3 strands twisted together.
Using cable ties or temp insulated wire down the holes between cells might help keep things in place as you build.

My system is LiFePo4 :)

Thank you for the feedback.
The longer zipties came in last night to connect the blocks together.
The bussbar will grow as the pack grows. Each column of 8x2=16 batteries will get a bare 12 AWG run to the lug.
One of my issues is that I want the ability to expand.

Are your LiFePo4s 26650s?

rearden
 

Redpacket

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Feb 28, 2018
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My LiFePo4's are actually pouch & prismatic blocks!

I was meaning using zip ties (thinking about it they might melt!) or anther method etc to hold the copper wires in place while soldering & for better handling strength when complete.

Most people seem to expand by adding more blocks of cells in parallel or build whole new parallel strings.
 

thunderheart

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Apr 4, 2018
Messages
275
rearden said:
I am starting my build. I started collecting 18650 but since have come across several hundred 26650 LiFePo in good condition so I am moving to those.
Good idea!

rearden said:
I purchased 4x4 battery holders on ebay.
How much did they cost?

rearden said:
I am using 6.3A slow blow glass fuses soldered to the positive side and 26AWG on the negative side.
26AWG on the negative as a fuse? Why if you've already fused the positive sides?

And, as Redpacket said, busbar seems kinda thin... What max current you gonna run at?
 

jonyjoe505

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Feb 28, 2018
Messages
223
I have not decided upon the inverter, solar charge controller or BMS yet. The goal is to store excess solar energy and use it at night, on demand or grid down. I need advice on those. This design would call for one large BMS.
For bms I recommend one of the chargery models. I have the chargery bms8t (they have a bms16t and 24t) they are all the same except in how large a series your system is.
This bms uses contactors to shutoff power when the battery is full. Regular bms uses mosfets (which leak voltage) causing voltage surges when they shutoff charging.
I been using mine on my 220ah 4s40p 32650lifepo4 battery and is working excellent, once setup you don't have to mess with it again. With a regular bms I was always having to adjust the bulk setting on the solar controller.
This bms is fully programmable, has temp sensors,loud audio alarm,1.2 amp balancing, LCD screen.


image_exefqb.jpg
 

rearden

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Joined
Feb 11, 2019
Messages
26
thunderheart said:
rearden said:
I am starting my build. I started collecting 18650 but since have come across several hundred 26650 LiFePo in good condition so I am moving to those.
Good idea!

rearden said:
I purchased 4x4 battery holders on ebay.
How much did they cost?



rearden said:
I am using 6.3A slow blow glass fuses soldered to the positive side and 26AWG on the negative side.
26AWG on the negative as a fuse? Why if you've already fused the positive sides?

And, as Redpacket said, busbar seems kinda thin... What max current you gonna run at?

16x of 4x4 cost ~$30 so twenty something cents per cell for a holder.

12g wire and 16 cell per home run. I checked my math, you are correct, that is light and I need to increase it to 10g, double it or only do a string of 8 per 12g run.
By my calculations, 640 cells in 16s40p (48v) config at 3000VA would need 1.56 amps per cell and therefore 25 amps per string of 16. That is pushing 12g wire. 5000VA in 16s64p would need 1.63a per cell and 26a per string.

as for the 26awg on neg, it can act as a fuse, it is also easy to work with. Should I not use the glass fuses and just use wire as fusing? and then use larger wire for the neg?


jonyjoe505 said:
I have not decided upon the inverter, solar charge controller or BMS yet. The goal is to store excess solar energy and use it at night, on demand or grid down. I need advice on those. This design would call for one large BMS.
For bms I recommend one of the chargery models. I have the chargery bms8t (they have a bms16t and 24t) they are all the same except in how large a series your system is.
This bms uses contactors to shutoff power when the battery is full. Regular bms uses mosfets (which leak voltage) causing voltage surges when they shutoff charging.
I been using mine on my 220ah 4s40p 32650lifepo4 battery and is working excellent, once setup you don't have to mess with it again. With a regular bms I was always having to adjust the bulk setting on the solar controller.
This bms is fully programmable, has temp sensors,loud audio alarm,1.2 amp balancing, LCD screen.


image_exefqb.jpg
Thank you for this suggestion. I will read up on this one. Any comparison with the Battrium? Which I guess is the gold (and expensive) standard?
 

rearden

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Feb 11, 2019
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26
Pulled apart a bunch more battery packs, I am up around 1000 cells. 26650 3.2v LiFePo4. Some are old, but I am having a hard time finding a tester for 3.2v.
 

floydR

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Joined
Aug 23, 2017
Messages
876
many use an opus which has a switch to limit the upper voltage to 3.7 a little highbut from what I have read not too much of a problem with LIFEPO4. you can cut a small hole on the back right left side of the opus to access the switch.
the Opus BT-C3100 and 3400 have the switch.
The cells are much cooler in the 26650 holders need to make new ones for all the cells.

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Note the hole is larger than need wanted to be sure I had acess to the switch.

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later floyd
 

rearden

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Feb 11, 2019
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26
Thank you for that information.
So if you change the switch, then the voltage charging and discharging profile will be dampened so that it will not exceed 3.7v? and 3.7v is acceptable for 3.2v lifepo cells?
Will the capacity testing cycle also stay within specs which will not harm the cells?
A switch like this has not been found on the Lii-500?

Thanks!
rearden
 
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