Help with building a 48Ah LiFePO4 trolling motor battery (Headway 38120s Batteries)

Newb to the forum and to building DIY Lithium battery packs so be gentle....

I've purchased twenty fourHEADWAY 38120 HP 3.2V 8AH LIFEPO4 LITHIUM BATTERIES 25C cells (reclaimed cells) for $10 a cell from a recent eBay deal. The Headway 38120 were recently discussed onJehu'sYT channel and I liked the idea of making a DIY battery pack using the 3820 batteries due to their high capacity and power output. I plan to eventually put this pack into a hardcase and use it to power a DIY PowerBox which will have IP65 12V, USB, speakers, AM/FM radio, voltmeter, LED lights, and dedicated power switches.

So now, the question is:

I'd like to build a 48Ah 12.8V battery pack (4s6p):

Attached is a pic of how I would arrange the batteries for this pack in a 4s6p orientation. Please let me know if my pack drawing isincorrect.





I appreciate any information you could provide. I tried getting feedback on theEndless Sphere forum but wasnot getting a lot of love over there. I'm hoping there's a strong community here for DIY battery builders here at 2nd Life Storage.


Thanks,

smithmal

Pack design is correct for a 4s setup.

Though, what is your designed max amp draw? I know the cells can handle it, but I'm more concerned about the metal connections. What gauge metal will you be using? Soldering or Spot welding? What type of metal (solid nickel, nickel coated, etc)?

Awesome. Thanks for the quick response.

Some more info for this build:

A. Headway3820 Battery Specs:link

B. 4s6p Pack Specs:
Volts: 12.8V (3.2V x 4)
Capacity: 48aH (8aH x 6)
Charge: 14.6V (3.65V x 4)
Discharge: 8V (2.0V x 4)
Watt Hours: 614.4 (48,000mAH * 12.8V/1000)

C. Trolling Motor Specs -The most current my trolling motor could pull (Minn Kota Endura Max 55) if I had it on full throttle is 50A

Additional questions I have include:

1. Choosing the correct BMS
I'd like to install a BMS with BT technology so I can monitor voltage, capacity, charging/discharging etc. on my phone. In terms of a BT BMS I was thinking of this: link

I realize that an 80A BMS might be a little overkill, but I wanted to have the versatility of hooking just about anything to this battery (i.e. future proof) and since the cells have a 200A capacity, the sky is pretty much the limit. Has anyone had any experience with this BMS and/or products from this site? Are the BT modules that they are selling functional across Android/iOS? How well do they work with older and newer BT versions? I've read about other BT modules that manufacturers attach to their BMS that have significant user connection issues.

2. Choosing the right busbars
Also, I'm assuming that I would need to use 2 hole and 6 hole busbars and that I should shoot for copper at the material. I don't think I've ever seen 6 hole busbars. Do they exist?Are there any sources you would suggest I use? How thick should the busbars be?

3. Choosing the right charger
My pack would be 614 watt hours so I wanted something that I could charge relatively quickly 4-6 hours. I also wanted to be able to balance charge, bottom balance and possibly top balance. I need it to be 1s-4s.

I was thinking about this charger (Ultra Power UP100AC Plus):link
Video Review on it here: link

Charger Specs:
Input Voltage: AC 100-240V, DC 11-18V
Charge Power: max 100W
Discharge Power: max 10W
Charge Current: 0.1-10A
Discharge Current: 0.1-5A
LiPo/Li-ion/LiFe/LiHV cells: 1-6
NiCd/NiMH cells: 1-15
Pb cells: 1-10

Another option (though muchmore expensive) is the Revolectrix GT500. I've read that many of these $50 chargers last a year and then the PSU goes on it so it's worth the investment in getting a well crafted charger that uses an external DC power supply:

Seen here: link
Video Review on it here:link

Charger Specs:
Input Voltage: DC 10-32V
Charge Power: max 500W
Discharge Power: max 500W
Charge Current: 0.25-20A
Discharge Current: 0.25-20A
LiPo/Li-ion/LiFe/LiHV cells: 1-8
NiCd/NiMH cells: 1-21
Pb cells: 1-12

Thanks,

[size=small]smithmal[/size]

Please fix your font-size. x-small or xx-small is too small. Most people leave they font on default size for readability

Trolling motors draw stuff all power from the cells - this will have heaps of range - can't help with the technical tho, unfortunately. I really need to run a test on how long my battery I build for a trolling motor will last.

Choose a bms that can do 80A isn't really overkill. Since it's a "cheap chinese" unit, also expect that the rating they give is the burst rating, so effectively 1/2 that during normal operations. You could probably get away with 50A on an 80A unit.
And, even if it is legitimately 80A standard, that gives you room to expand into later (lights, audio/radio, another motor, etc)

Not sure what you mean by a busbar having 6 holes. I figured you just drill all the holes you need in the copper bar.

Korishan said:

Not sure what you mean by a busbar having 6 holes. I figured you just drill all the holes you need in the copper bar.

Click to expand...

Korishan,

Where should I obtain a copper bar from and what thickness should I use?

smithmal

smithmal said:

Korishan said:

Not sure what you mean by a busbar having 6 holes. I figured you just drill all the holes you need in the copper bar.

Click to expand...

Korishan,

Where should I obtain a copper bar from and what thickness should I use?

smithmal

Click to expand...

You should be able to get it at your local metal shop. You might find it in a hardware store like Lowe's or Home Depot, but probably not on the shelf. It'd be a special order item.
But most metal working shops should have it, or at least tell you where they purchase theirs from.

smithmal said:

Korishan said:

Not sure what you mean by a busbar having 6 holes. I figured you just drill all the holes you need in the copper bar.

Click to expand...

Korishan,

Where should I obtain a copper bar from and what thickness should I use?

smithmal

Click to expand...

It may be worth visiting the local scrap dealer.

As for size. 10mm2 should be plenty. A bar around 5mm X 2mm. However you may wish to go thicker, just for the sake of strength.

Geek said:

smithmal said:

Korishan said:

Not sure what you mean by a busbar having 6 holes. I figured you just drill all the holes you need in the copper bar.

Click to expand...

Korishan,

Where should I obtain a copper bar from and what thickness should I use?

smithmal

Click to expand...

It may be worth visiting the local scrap dealer.

As for size. 10mm2 should be plenty. A bar around 5mm X 2mm. However you may wish to go thicker, just for the sake of strength.

Click to expand...

Not sure what you mean by 5mm x 2mm....

There a vid of someone making busbars out of 3/4"copper piping on YT (link here)

His 2 holebusbarswere 61.6mm long by 1.5mm thick (not sure of the width but I read elsewhere that they are 24mm wide (or 1")).His notes in his vid indicated that his busbars were rated for 137.5 amps which is more than enough for me.

I figured the following:

Parallel connections:
8 strips of 1.5mm thick240mm longstrips
To get 8strips I would need to purchasefour2' pipes

Series connections:
18 strips of 1.5mm thick61.6mm long strips
To get 18strips I would need to purchase two2' pipes

Altogether that twelve 2' copper pipes (3/4 thick) = $6.90 x 6= $41.50+ labor to cut, press, and drill holes tomake strips

Any idea how much it would cost to purchase 12'of 1" wide by1.5mm thick (roughly 16 gauge)copper strips from a metal shop?

Thanks,


smithmal

Pipes would work, too. I think there are a couple users here that used copper pipes for various parts. I'm thinking Wim was one of them (he has a build thread)

The pipes can work really well, overall. Just smash them flat and drill your holes where you need 'em, and done

Now, there are 2 major different types of copper pipe. M and L. One of them has a thicker wall than the other as it's designed to handle a higher working pressure. I would go with that one as more copper equals more amps, and less resistance with same amps = less heat build up

smithmal said:

Geek said:

smithmal said:

Korishan said:

Not sure what you mean by a busbar having 6 holes. I figured you just drill all the holes you need in the copper bar.

Click to expand...

Korishan,

Where should I obtain a copper bar from and what thickness should I use?

smithmal

Click to expand...

It may be worth visiting the local scrap dealer.

As for size. 10mm2 should be plenty. A bar around 5mm X 2mm. However you may wish to go thicker, just for the sake of strength.

Click to expand...

Not sure what you mean by 5mm x 2mm....

There a vid of someone making busbars out of 3/4"copper piping on YT (link here)

His 2 holebusbarswere 61.6mm long by 1.5mm thick (not sure of the width but I read elsewhere that they are 24mm wide (or 1")).His notes in his vid indicated that his busbars were rated for 137.5 amps which is more than enough for me.

I figured the following:

Parallel connections:
8 strips of 1.5mm thick240mm longstrips
To get 8strips I would need to purchasefour2' pipes

Series connections:
18 strips of 1.5mm thick61.6mm long strips
To get 18strips I would need to purchase two2' pipes

Altogether that twelve 2' copper pipes (3/4 thick) = $6.90 x 6= $41.50+ labor to cut, press, and drill holes tomake strips

Any idea how much it would cost to purchase 12'of 1" wide by1.5mm thick (roughly 16 gauge)copper strips from a metal shop?

Thanks,


smithmal

Click to expand...

5mm wide by 2mm. 3/4 copper pipe would be quite sufficient for the current.

Okay, copper pipes it will be. Any thoughts about the charger I should get?

smithmal said:

Okay, copper pipes it will be. Any thoughts about the charger I should get?

Click to expand...

I can't say much about the two chargers you listed, as I have never used them.

The iChargersarevery popular choice around here. I have a Charsoon Antimatter 300w, which is an iCharger 206bclone. I like it a lot. The Turnigy Reaktor is another reliable clone (available from Hobbyking).

Suggestions are buying a charger that uses an external DC supply. Used server power supplies are often readily (and cheaply) available and can easily be converted into high current DC power supplies. Very reliable too!

It is very handy having a good quality hobby charger around. I charge all sorts of batteries with mine. I also own several cheaper chargers too. Most of which I am very pleased with.

Geek said:

smithmal said:

Okay, copper pipes it will be. Any thoughts about the charger I should get?

Click to expand...

I can't say much about the two chargers you listed, as I have never used them.

The iChargersarevery popular choice around here. I have a Charsoon Antimatter 300w, which is an iCharger 206bclone. I like it a lot. The Turnigy Reaktor is another reliable clone (available from Hobbyking).

Suggestions are buying a charger that uses an external DC supply. Used server power supplies are often readily (and cheaply) available and can easily be converted into high current DC power supplies. Very reliable too!

It is very handy having a good quality hobby charger around. I charge all sorts of batteries with mine. I also own several cheaper chargers too. Most of which I am very pleased with.

Click to expand...

Geek thanks for the response. I really appreciate the feedback. I researched both the Charsoon and Turnigy Reaktors chargers, which are both very highly praised chargers so I'm glad I'm using the same models as a baselineto compare with themodels listed above.

Concerning the Reaktor models, I read about some of them dying after a couple of years. I've also read that the new models have different firmware thathave hampered their functionality somewhat. People are high on the Charsoon 300W chargers.

After reading a bunch of comparison review threads between the Reaktor, Charsoon and Revolectrix chargers, I decided to go with theGT-500 charger due how it sets up it's menu, and higher power rating (500W, 20A). People are also impressed with is larger heat sink and overall construction. Also with it being on sale for $75 I thought it to be a good investment if I'm ever interested in going down the solar pathway.

Regarding pack charging and power supplies, I have a couple of questions:

1. In terms of the power supply, the GT-500 manual (link)calls for a 25W DC/25amp power supply in order for the GT-500 to provide it's full power potential(500W/20A). If I'm understanding charge/dischargerates, people generally charge @ 0.5C - 1C. Is the C rating based on each individual battery (which would be 8Ah) or the whole pack (which would be 48Ah)? From what I've seen people are charging similar packs using between 3A-5A so I'm thinking the former in terms of C rating. Is that correct?

2. For a power supply, I was thinking of getting this (link). Thoughts? Is this good/bad?

3. If I purchased this, I believe I would need them to stick a male EC5 on the end of it to connect to the GT-500. Is that correct?

4. The vendor also allowsfor customization to add additional power output adaptors. Are there any that you think are worth adding?

Thanks,

smithmal

C rating is the capacity in mAh / 1000. So if the pack is 48000mAh, 1 would be 48A. .5C is 24A.
However take into consideration your cells. Being new, and headways, i doubt you'd have any issues though.

If you had used old cells, then .25C would be better. 18650's are generally .5C manufacturer rated. So again, you should be fine

Korishan said:

C rating is the capacity in mAh / 1000. So if the pack is 48000mAh, 1 would be 48A. .5C is 24A.
However take into consideration your cells. Being new, and headways, i doubt you'd have any issues though.

If you had used old cells, then .25C would be better. 18650's are generally .5C manufacturer rated. So again, you should be fine

Click to expand...

Okay, so if I've got this right:Amps x Volts = Watts

Therefore if I charged at 0.5C (24 amps) usingthe power supply/charger linked above timesthe combined voltage of my pack(14.6), the amount of watts I'd be charging into my pack would be

24 amps x 14.6 volts = 350.4 watts

Since my pack is 614 watt hours, thatwouldmean that I should be able to fully charge my pack in less than two hours. Is that correct?

Sounds about right. But would probably take about 3hrs total due to losses along the way.

http://www.revolectrix.com/support_docs/item_1452.pdf said:

Continuous maximum output power rating, 500W @ +24VDC input voltage, 250W @
+12VDC input voltage

Click to expand...

Actually, you can only charge at a max of 250W, so about 4 hours

Anyone have any thoughts about my power supply questions above?

Korishan said:

Sounds about right. But would probably take about 3hrs total due to losses along the way.

http://www.revolectrix.com/support_docs/item_1452.pdf said:

Continuous maximum output power rating, 500W @ +24VDC input voltage, 250W @
+12VDC input voltage

Click to expand...

Actually, you can only charge at a max of 250W, so about 4 hours

Click to expand...

smithmal said:

Anyone have any thoughts about my power supply questions above?

Click to expand...

Ummm, you mean, does "anyone else" have any thoughts?