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Help with building a 48Ah LiFePO4 trolling motor battery (Headway 38120s Batteries)
#21
Geek,

Thanks for the advice,  guess I'll skip that one.

How about this model: link
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#22
Decided to go with this 24V/21A/500W power supply (link).  Hopefully not Chinese junk.  I guess time will tell but it gets decent reviews on Amazon.
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#23
More questions:

1. Is there a thread on 2ndLife that specifically goes over the do's and don'ts when building a battery pack using high energy lithium batteries?
2. Regarding the purchasing of the BMS and balancing wire, I was going to just get a 4S BMS with a 4S balancing wire, but I've seen packs where people wire up every single battery to their BMS. Is it really necessary to balance every battery in the pack, or are you good just balancing each cell?
3. After making my copper busbars, should I wrap the middle of each busbar (i.e. between the contacts) with electrical tape to protect from shorts? I've seen off the shelf copper busbars like this.
4. What gauge wire should I use for transferring power from battery to a switch (I'm thinking 12 gauge, but wanted to make sure)

Thanks for everyone's help.

smithmal
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#24
Wire gauge is dependant on what you'll be expecting to draw, the size then ditates your fusing and other protective devices.

Heat shrink does a good job of partially covering busbars.

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#25
(10-14-2018, 01:04 PM)smithmal Wrote: More questions:

1. Is there a thread on 2ndLife that specifically goes over the do's and don'ts when building a battery pack using high energy lithium batteries?
2. Regarding the purchasing of the BMS and balancing wire, I was going to just get a 4S BMS with a 4S balancing wire, but I've seen packs where people wire up every single battery to their BMS.  Is it really necessary to balance every battery in the pack, or are you good just balancing each cell?
3. After making my copper busbars, should I wrap the middle of each busbar (i.e. between the contacts) with electrical tape to protect from shorts?  I've seen off the shelf copper busbars like this.  
4. What gauge wire should I use for transferring power from battery to a switch (I'm thinking 12 gauge, but wanted to make sure)

Thanks for everyone's help.

smithmal

1. I suggest watching some youtube videos on this one. Lithium batteries are capable of delivering a huge amount of current. Be very careful to avoid short circuits. Make sure all connections are secure.

2. You must balance each parallel group. Make sure your BMS is designed to suit your batteries - top and bottom voltage, and amps drawn. Many cheap BMS will not do close to their rated amps. Do your research.

3. Sean answered this one - heat shrink is the best.

4. I would probably opt for at least 10 Gauge. But that's me - I like to overbuild things where possible. I would also consider using a relay, if the distance between your battery motor and switch is significant.
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#26
(Yesterday, 04:29 AM)Geek Wrote:
(10-14-2018, 01:04 PM)smithmal Wrote: More questions:

1. Is there a thread on 2ndLife that specifically goes over the do's and don'ts when building a battery pack using high energy lithium batteries?
2. Regarding the purchasing of the BMS and balancing wire, I was going to just get a 4S BMS with a 4S balancing wire, but I've seen packs where people wire up every single battery to their BMS.  Is it really necessary to balance every battery in the pack, or are you good just balancing each cell?
3. After making my copper busbars, should I wrap the middle of each busbar (i.e. between the contacts) with electrical tape to protect from shorts?  I've seen off the shelf copper busbars like this.  
4. What gauge wire should I use for transferring power from battery to a switch (I'm thinking 12 gauge, but wanted to make sure)

Thanks for everyone's help.

smithmal

1. I suggest watching some youtube videos on this one. Lithium batteries are capable of delivering a huge amount of current. Be very careful to avoid short circuits. Make sure all connections are secure.

2. You must balance each parallel group. Make sure your BMS is designed to suit your batteries - top and bottom voltage, and amps drawn. Many cheap BMS will not do close to their rated amps. Do your research.

3. Sean answered this one - heat shrink is the best.

4. I would probably opt for at least 10 Gauge. But that's me - I like to overbuild things where possible. I would also consider using a relay, if the distance between your battery motor and switch is significant.

Sean/Geek,

Thanks for the advice.  I had planned on heat shrinking the pack in general (BTW, what heat shrink (thickness) would you suggest), but was thinking that taping the of busbars between contacts would be advantageous if, for some reason, I needed to reopen the pack at some point to fix bad leads or a faulty BMS, etc.  I was wondering if there are any cons to taping the busbars that I didn't know about.

In regards to the safety technique question, I have seen many YT videos regarding pack building, but was wondering if there was a thread here and 2ndLife which brings safety knowledge when building DIY packs into one concise thread.  I think this would be especially important to newb pack builders such as myself before starting to build a new pack.  If there isn't a thread yet, maybe I'll start one up.  

In terms of a BMS, are there manufacturers or models that you would suggest I look into?  I mentioned the BMS that I was targeting to use earlier in the thread but didn't hear back about what people thought about it's quality (I believe it has all the specs I need for my build).

If I'm understanding a relay properly, putting in a relay between the battery and the motor would disallow power to the motor unless the switch is engaged making it safer to hook up/remove the power to the motor.  Is that correct?  Wouldn't a switch already act as a relay (i.e. if it's not triggered, there's no power to the component the switch is associated with).  Would the use of a relay be present to act as a safety redundancy?

Thanks,

smithmal
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