Is upgrading from 8 gauge to 6 gauge wire worth it?

[zombiess]

I'm currently in the process of upgrading my Lyen 18 FET 150V controller to 8 gauge wire for battery and phase.

The setup is a mix of gauges due to connector fitment. Battery harness connections are all 12 gauge, 3 paralleled together, then put in series for 30S which is five 6S packs. The negative and positive then feed to 8 gauge wire and a 60A car audio fuse on the positive. These then connect to about 3 inches of 10 gauge wire that go into a hobby king 4mm bullet. On the other side is the mating bullet which has 10 gauge wire for about 2.5 inches, then goes to 8 gauge for about 3 feet into the controller soldered directly to the B+ and B- on the board. I also have a 10 gauge feeder connecting the tabs of the FET banks to the same B+ feed to help feed the FET's directly instead of jut through the board traces.

My phase wires are still stock 12 gauge coming out, but the connections to the motor are 10 guage for about 3 feet and then are soldered directly to the 12 gauge phase wires I upgraded to.

Less interconnects = less resistance.

Old battery setup was a mix of 8-10-12 gauge with most of the battery wire length being 12 gauge. After doing some math I found out that with 12 gauge and 2 interconnects (each one estimated at .003 ohms total /XT60 + a charred 4mm bullet from no precharge resistor) and it looks like I was dissipating about 217 watts into the 7 feet (3.5 each way including that inside the controller) wires feeding the controller at 60A battery draw resulting in 1.1V of drop from the battery to the controller.

By going to all 8 gauge and just having one connector I'm estimating my interconnect will be .0015 per side I should no only see a waste of 102 watts total and 0.4V drop @ 60A. I'm planning to go to 100A so I know the 12 gauge stuff just won't cut it, the inductance is also almost triple that of the 8 gauge wire and I've read inductance on the battery wires = bad.

With my upgrades at 100A draw I'm calculating a loss of 282W into the 8 gauge battery wire and a drop of 0.7V, this seems acceptable since it's I'll only be peaking these numbers during hard acceleration.

Do you think I should bump up to 6 gauge for the battery feed?

What about my phase wires. They are currently 10 gauge with the stock 12 gauge feeding from the controller. I was also planning to build a new harness for the Croatian Hubzilla out of 8 gauge wire and upgrade the controllers internal wiring to 8 gauge as well. I'd also ditch the spades for the 4mm bullets I have on hand by trimming just enough of the wire to make it fit and then heat shrinking it to fit, then same on the other side to the motor with it's 10 gauge wires cut shorter and soldered to my 8 gauge feeders. Since this is 3 phase each wire isn't carrying the full amps for very long so they share the load.

Thoughts?

 

[John in CR]

You have neither a controller nor motor that can handle 100A, unless you want to join Methods in burning up perfectly fine 9C's.

 

[zombiess]

You have neither a controller nor motor that can handle 100A, unless you want to join Methods in burning up perfectly fine 9C's.

You don't know what I have

I don't know what my controller is capable of with the mods done to it but it's very hard to get the FETs over 55C while drawing 60A from the battery unless I use a lot of regen and they cool off fast. In normal stop and go commuting with a top speed of 42 (70% throttle setting) they FETs stay in the 35-45C range, enclosure ambient temp is 30-35C). Programmed for 47A battery 130A phase, no idea what the phase really is outputting though. I sure as hell am not going to try and dump this kind of power into my 9C, do you think I'm nuts? I'm going 55+ mph with a 2806 which means I'm probably putting out over 6 HP to the ground. I think I'm right at the saturation point of the motor. Got it up to 130C the other day after letting a 220lb friend abuse in 105 throttle mode it right after I rode it for 8 miles and he kept using lots of regen.

Now answer the question Punk!

 

[neptronix]

You have neither a controller nor motor that can handle 100A, unless you want to join Methods in burning up perfectly fine 9C's.

:lol: :lol: :lol:

I run 12 gauge phase wires when dumping 55a/80v ( >4kW ) and they do the job pretty well and never get warm. I'd imagine that 8 gauge would be just fine for the job at hand here.

 

[ZOMGVTEK]

8 Gauge phase is about as thin as I would run for that build. If you can get 6 into the connectors, by all means run it on the phase wires. Those can see some very high currents, at least momentarily. Using the largest wire you can get, minimizing the connectors used, and minimizing the contact resistance, will all have rather marginal impact. However, if you are doing it anyways, I don't see why you would pick a thinner wire if you can manage to jam thicker stuff in.

I'm running 10 AWG all around and it gets warm under heavy loads. I'm only running 6-7kW, I'd imagine you would want to pump a bit more than that into hubzilla. It should be able to take 10kW without much complaint, I would build for 15...

I would run 6 AWG of the highest stand count silicone wire you can find, into 75A PowerPoles. Might as well drill out the controller, and run the phase straight to the motor. No need for any connectors aside for the 75A PP's a few inches away from the hub. While you're at it, might as well run the 6 AWG off the battery , with a single connector into the controller. Try and only have a single connector for all high current applications, and of course use good connectors. Inductance on the battery side is more of an issue when you are running the controller close to the edge. If you are running 30S and 150V FET's, you are better off than most with 24S on 100V FET's. Minimizing the power wire length is a good idea, the long wires should be the phase, making the controller as close to the battery as possible.

Are you running an ANL fuse? The few I've screwed around with at 100+V did not blow very well. A high voltage DC fuse might be a good idea, if you're into what little protection a fuse provides. With really thick wires, and a lot of LiPo, it's recommended, but I don't have one. :x

 

[zombiess]

Thanks for the input. I'm gonna price out some 6awg or maybe 4 awg silcone wire since it's pretty reasonably priced on ebay and often the 4awg is more like 5awg but does have a very high strand count. Last stuff I used on my car wast quite nice.

Sigh... more money, but if your gonna build it, might as well attempt to do it sorta right :lol: