New hi-speed project

[BrianG]

While it would be nice to have 100v capability, I wonder if it would be needed. Sure, the higher resistance won't matter much if using >50v, but most won't and companies have to manufacture for the majority, not the extreme monority.

OTOH, an ESC for portable transport (like bikes) would make good use of 100v FETs. It's all about target audience. I don't see someone placing a 27s pack in their R/C anytime soon! Just the wiring of the balancer plug(s) alone would be a nightmare! Maybe if someone came out with 10v cells...

[lutach]

Originally Posted by BrianG

While it would be nice to have 100v capability, I wonder if it would be needed. Sure, the higher resistance won't matter much if using >50v, but most won't and companies have to manufacture for the majority, not the extreme monority.

OTOH, an ESC for portable transport (like bikes) would make good use of 100v FETs. It's all about target audience. I don't see someone placing a 27s pack in their R/C anytime soon! Just the wiring of the balancer plug(s) alone would be a nightmare! Maybe if someone came out with 10v cells...

The 100V can be used for only 12S lipos. My controllers are having 75V FETs in them, but they are rated for only 14S (15S max).

[Mod Man]

Originally Posted by BrianG

OTOH, an ESC for portable transport (like bikes) would make good use of 100v FETs. It's all about target audience. ...

Like this?

http://www.recumbents.com/wisil/shumaker

Matt

[BrianG]

Yeah, like that.

Lutach, why only 12s on a 100v FET? Even generously allowing for back-EMF pulses, that is still at least 20s. I wonder if the limiting factor of your 75v FETs is the other components (caps, etc)?

At any rate, for your typical 12s setup, the 60v FETs are fine IMO. And the ones you have access to seem quite a bit better than the ones currently in the HV-110 as far as the current, on resistance, and switching time goes. You'd only need one or two layers instead of 3 (of course, more won't hurt ).

[lutach]

Originally Posted by BrianG

Yeah, like that.

Lutach, why only 12s on a 100v FET? Even generously allowing for back-EMF pulses, that is still at least 20s. I wonder if the limiting factor of your 75v FETs is the other components (caps, etc)?

At any rate, for your typical 12s setup, the 60v FETs are fine IMO. And the ones you have access to seem quite a bit better than the ones currently in the HV-110 as far as the current, on resistance, and switching time goes. You'd only need one or two layers instead of 3 (of course, more won't hurt ).

Don't the controllers have a watchdog that knows if a voltage is higher then what they can actually take? I know my Schulze 40.160 will arm at exactly 60 volts and nothing more and they use a MOSFET of the same voltage as the ones my controllers will have. If Patrick can change the MOSFETs for the 100V units and I can use higher voltage, then it will be a plus. I wish they could've done the HV like the MGM with the brainboard in the middle and if you wanted more power just stack the powerboards. Kind of like a hot swap set up.

[BrianG]

Depending on the ESC, it might have some type of voltage monitoring, but that would most likely be in firmware or some dedicated IC. Even then, this watchdog thing will only prevent the ESC from functioning, but the full battery voltage will still be at the drain and source terminals of the FETs.

Using higher voltage FETs would keep them further away from the actual voltage being used (best not to run anything at their max values). But if the current, slew rate, and rds-on are not equal (or better) as the lower-voltage FETs, you're not gaining anything. I would rather have FETs that are rated around 10-15% higher voltage than what you plan to use, but use ones that have higher current, lower rds-on, and faster slew rate for thermal reasons.

As far as construction, the method Castle uses to stack the power boards is pretty good. The brains are on top where they (hopefully) won't get as hot from the FET boards, and stacking is simple even with the heatsinks. With the MGM, the brains board might be heated beyond what I would like. Oh, and the heatsinks on the HV are nice since they contact BOTH sides of the PCB so ALL the FETs are cooled. The only layer that isn't cooled is the top one, but Castle puts an Al heatspreader on there. I might contact them to see if I can get an extra heatsink piece for that. The more I look at this ESC, the more I like it! If only they would make it work with pistol grip radios a little better.

[lutach]

Originally Posted by BrianG

Depending on the ESC, it might have some type of voltage monitoring, but that would most likely be in firmware or some dedicated IC. Even then, this watchdog thing will only prevent the ESC from functioning, but the full battery voltage will still be at the drain and source terminals of the FETs.

Using higher voltage FETs would keep them further away from the actual voltage being used (best not to run anything at their max values). But if the current, slew rate, and rds-on are not equal (or better) as the lower-voltage FETs, you're not gaining anything. I would rather have FETs that are rated around 10-15% higher voltage than what you plan to use, but use ones that have higher current, lower rds-on, and faster slew rate for thermal reasons.

As far as construction, the method Castle uses to stack the power boards is pretty good. The brains are on top where they (hopefully) won't get as hot from the FET boards, and stacking is simple even with the heatsinks. With the MGM, the brains board might be heated beyond what I would like. Oh, and the heatsinks on the HV are nice since they contact BOTH sides of the PCB so ALL the FETs are cooled. The only layer that isn't cooled is the top one, but Castle puts an Al heatspreader on there. I might contact them to see if I can get an extra heatsink piece for that. The more I look at this ESC, the more I like it! If only they would make it work with pistol grip radios a little better.

I found the problem about voltage with the Traxxas VXL controller which could be a nice 4S controller, but the thing won't do nothing if you plug 4S to it. I also like the HV110 design. The MMM could've looked like it.

[BrianG]

Well, I ordered the ThunderPower TP-210 balancer and a HV UBEC.

I know I could have simply gotten another LBA10 and networked them, but didn't like having to use the network cable, not to mention the added mess from the input/output Y adaptors for the main charge current.

The choice between balancers was between the DimensionEngineering HVBEC and Western Robotics. The WR BEC was kinda pricey, but is capable of higher current (3.5A vs 2.5A for the DimEng one), and the components on the WR looks beefier. Once the BEC comes in, I'll perform a test on it like I did with the other BECs. The other option I was tossing around was to daisy-chain 8 diodes in series to drop ~5v to bring the 10s battery voltage down from a max of 42v to ~37v. This would have allowed me to use the KoolFlight UBEC (which tests out and performs quite well). The KF BEC has a max input of 40v - actually, the switching IC is rated for an absolute max voltage of 45v but that's pushing it.

Now I'm looking for connectors. I was going to use Deans, but they don't handle the current I'm expecting. I don't want to use bullet connectors because they are a PITA to connect/disconnect IMO. What is available that is polarized/keyed, rated for 100A+, connects both poles at the same time (like Deans), yet is still small/light?

[Arct1k]

Two sets of deans?

[speedracer1129]

Have you taken a look at the Power Pole connectors that are offered at the Mega Motor site?? www.megamotorusa.com, under connectors in the shop.

[BrianG]

Arctic: Maybe, if nothing else works like I want. 50A X 2 would be sufficient I think. Kind of a PITA, but oh well I guess. Deans really outta make a higher-current version...

Speedracer: The 75A version of those powerpoles is probably what I will have to go with. They're big, but I don't want something that won't handle the current I anticipate without voltage drops. I ckecked out powerpoles before, but all I saw was the 30A version. Thanks for the tip!

[Mod Man]

It is good to focus on connectors. I run Deans without issues, But, I am pushing them beyond what I really trust them for.

One thing to consider too is minimizing wire length. You are much more knowledgeable in electronics than I. But, I have seen huge voltage losses in my wiring. Make EVERY effort to shorten the wires from cells to ESC and ESC to motor as much as possible. It may seem like "Ya, ya, ya, I know that......" But, it is easy to overlook when dealing with the more involved aspects of the project.

I strive for NO wire heat after a run. Heck, if you are running an Eagle Tree, I would suggest running a temp probe on the main power wire to the ESC at the center point to read wire temp.

Just a thought.

Matt

[BrianG]

Oh yes, I'll be keeping wires short as possible. The HV-110 uses 10GA wires, so that will help. If you look at the pictures, you can see I tried to position the ESC so all connections are made with the shortest wire length, but it had to be "pretty" too.

I don't have an eagletree, but a finger check of the wires after a run for warmth should give me a decent clue.

[Arct1k]

I know it is a pain but with this kind of one off setup I'd go for 5.5 or 6.5mm castle connections...

[ziggy12345]

Hi

I havent read all of this thread but am wondering how is the build coming along? Are you entering the speed event in October?

Cheers