paper: FRC Battery Upgrade

battery
frc900
upgrade
wires
cables
zebracorns

#1

Thread created automatically to discuss a document in CD-Media.

FRC Battery Upgrade
by: deusXmachinist

We upgraded our battery cables to 4-gauge.

During preseason we decided to upgrade out battery cables. This is a paper detailing our process and reasons behind the change.

FRC900 Battery Upgrade.pdf (10.1 MB)


#2

Happy to answer questions about this if you have any!


#3

Which wire are using? Did you have to cut any strands to get it into the SB50 crimp?

We found using multiple heat shrink layers over the bolted connection helps keep things in place.

I like the washer setup and will likely start doing that, we had been using internal star washers but your setup looks better.


#4

The total cost for each cable we made was less than $10.00

vs


Nice!

We are currently using 97527A005, the king of all lockwashers, but after seeing how clean this solution is, I’m also interested in trying some of these Nordlocks.

What crimper are you using? Is it really pneumatic? We’ve been using the Harbor Freight cheapo hydraulic crimper and it’s just fine.

Good work Annie and Levi!


#5

Are you really gaining an advantage by using two sets of washers?


#6

I love nord-lock washers. Is there any reason why you use 2 sets per connection? It seems like one on the bolt head side would do the trick.


#7

This is extremely helpful. To someone with more electrical knowledge than me, how much of an effect does thicker battery cables have on performance?


#8

Where did you source your SB50 connectors with 4 gauge lugs? The SB50A at Andymark only come with lugs for 6 gauge.

The same 6 gauge lugs from Powerwerx, plus those SB50SB’s don’t match up with FRC connectors.

Getting new SB50 could double your $10 budget on this.


#9

4 AWG over 1 foot (each side) at 12V and 120A load is a 0.060V drop.

6 AWG, .095A.

It gets more pronounced if your robots have higher current draws, longer wire runs, or crappier crimps–but there’s your baseline. I’d be inclined to tackle other places first (especially upping drive motors from 12 AWG to 10 AWG, which has a higher percentage effect, and shortening runs there), but if you’re sweating every bit of your battery voltage that’s one to do as well.


#10

Yeah, I don’t know if I have more electrical knowledge than you, but it looks to me like if your robot is wired with 36 inches of red and black 4awg, and you’re drawing 240 A, it would give you access to an additional tenth of a volt at your PDP.

[240 A * (.3951-.2485 ohm) * 36 in]/(1000 ft) = .1 V


#11

I think the reduction of waste heat is a more significant improvement.

0.1056 Volt x 240 Ampere = 25.3 Watt.

With 6 AWG, that extra wasted power is heating the cables, and that heat is flowing from the cables to their contacts; cycles of that heating, with cool-off periods between, accelerate loosening of those contacts. When contacts get too loose, they will exhibit momentary high resistance during mechanical shocks, causing brown-out. Because the contacts are hidden under insulation (tape, heat shrink, or connector housings) they don’t get inspected and their failure comes as a surprise.

With 4 AWG, that 25.3 Watt goes to the PDP as usable electric power, putting less cyclic thermal stress on contacts and allowing the robot’s electrical system to do more.


#12

It’s just 4awg wire from Amazon with decent strand count (370) - Price has increased by slightly more than $6 since we ordered it:

http://a.co/9MzuKmN

We did not cut any strands and the students took their time using the correct stripping tool (http://a.co/1c9esHm) for this gauge of wire and then carefully slid the wires into the 6awg connectors.

More on the washer setup in a minute…

The crimper is not pneumatic… I’ll pretend it’s an allusion to the hydraulic arm video from FIRST and not a mistake though. :wink:

Advantage? No… but we are using them the way Nord-lock recommends.

Yes, that’s how they say to use them: http://www.nord-lock.com/nord-lock/wedge-locking/washers/joint-guide/

http://cdn.nord-lock.com/wp-content/uploads/2012/05/Joint_through-hole-250x250.png

I have no idea why you think they don’t match. See above info about lug sizing. Also, price with new SB50s doesn’t break the bank and since you don’t believe me, you can do some math:

  • SB50: $1.24
  • 1 ft Red cable: $1.00
  • 1 ft Black cable: $1.00
  • PP75/SB50 Loose Piece Contact (Gauge: 6): $0.58
  • PP75/SB50 Loose Piece Contact (Gauge: 6): $0.58
  • THOMAS & BETTS 54906BE 4 AWG LONG BARREL 1/4 " SINGLE HOLE - BLIND END: $0.80
  • THOMAS & BETTS 54906BE 4 AWG LONG BARREL 1/4 " SINGLE HOLE - BLIND END: $0.80
  • 10-32 Nylock Nut: $0.09
  • 10-32 Nylock Nut: $0.09
  • 10-32 Bolt: $0.23
  • 10-32 Bolt: $0.23
  • Nord-lock Washer: $0.52
  • Nord-lock Washer: $0.52
  • Nord-lock Washer: $0.52
  • Nord-lock Washer: $0.52
  • Red Heatshrink: $0.39
  • Black Heatshrink: 0.39

#13

Easy Hoss,

I’m not trying to start a war. I think they don’t match because I just ordered one of these for our new battery analyzer (https://powerwerx.com/anderson-sb-connectors-sb50-50amp) and it doesn’t match any of the FRC connectors on our batteries without significant modification!

Also, my question was for where you sourced the SB50 with 4 gauge lugs. Your paper does not state that you are using 6 gauge lugs. That makes a difference, look at the 4 gauge options and the price climbs.

While, I know this is a safe practice; with some of the inspectors I have ran into the last two years, justifying jamming a 4 gauge wire into a 6 gauge lug, is a battle I’m not willing to take on right now.


#14

Interesting… I’ve only used them on studs in industrial applications, but after seeing your post and thinking about the locking mechanism it makes since to need them on both sides of a bolted connection.


#15

Did you order a color other than red? I don’t know what you mean by it doesn’t match? Got pictures?


#16

Did you get a red SB-50 connector from them? The only colors that mate with red are red and pink, the latter presumably a custom run for FRC so Anderson’s donated housings are obvious.

edit: sniped


#17

Did you give any thought to using the SB120 connector instead of the SB50?


#18

We have decided to make the plunge this year. We have purchased 2 awg wire. SB120’s and a hydraulic crimper. Now I’m going to purchase those washers.

Should be an interesting challenge.


#19

We did but ultimately the size is a bit too much to swallow. I’ve got one kicking around somewhere that I ordered just to hold it and it’s YUGE.


#20

Yep, evidently that is where we went wrong. We got orange for our team color.