Designing the ultimate heated undersuit

[elvenhome21]

Any specific type of wire to try to get that will hold up to continually being moved and bent in an undersuit?

Thhn is one of the higher temp rated wires but you can go 2 routes, welding/jumper cable style wire is super flexible because is has many small gauge wire strands, vs thhn is less larger gauge strands so less flexible. Biggest thing with wire is having it ran inside a sewn in tunnel that it can't move around freely.

 

[rjack321]

Personally I would avoid wires getting warm inside a dry suit.

That said 18ga wire *is* suitable for this heating solution (and also works with the table linked).

Only if you keep the system to <100W. Above that and 18ga is getting pretty iffy.

100W of heat is A LOT and requires crazy large batteries. Personally I would stick to 18ga and try to keep the max wattage in the 70W neighborhood just to not go crazy on batteries

 

[RedSeaDiver2]

Thhn is one of the higher temp rated wires but you can go 2 routes, welding/jumper cable style wire is super flexible because is has many small gauge wire strands, vs thhn is less larger gauge strands so less flexible. Biggest thing with wire is having it ran inside a sewn in tunnel that it can't move around freely.

Many thanks - that is really good information to have as well!

 

[RedSeaDiver2]

Only if you keep the system to <100W. Above that and 18ga is getting pretty iffy.

100W of heat is A LOT and requires crazy large batteries. Personally I would stick to 18ga and try to keep the max wattage in the 70W neighborhood just to not go crazy on batteries

The Santi vest is 55 watts, the Santi Flex 2.0 is 110 watts.

I think that these graphene panels are more efficient than other heating methods. With the two circuit design we should be able to limit each circuit to 70 watts.

 

[rjack321]

The Santi vest is 55 watts, the Santi Flex 2.0 is 110 watts.

I think that these graphene panels are more efficient than other heating methods. With the two circuit design we should be able to limit each circuit to 70 watts.

The effective output is less than as the voltage in a 11.1V nominal battery drops

There is no way to "make heat" more efficiently.

70W x 2 (12-14amps) will exceed the ability of a single BMS in the battery pack to handle the load. The compact BMS-s available are limited to 10A each. You will also need thicker wire in the battery itself and thicker or doubled up nickel strip in the battery. Net you will need 2x BMS, 0.15x7mm nickel strip, and 16ga wire at least up to your splitter to handle ~13amp loads. The 0.15mm thick nickel strip will be marginal in a garage grade spot welder.

 

[elvenhome21]

The other part is you don't need to run only 1 wire set. 18 is a nice size for connectors and soldering. You can run individual set of 22/24ga to each panel and really have unnoticeable wires but they are stupid fragile and a pita to solder and attach connectors

 

[RedSeaDiver2]

The effective output is less than as the voltage in a 11.1V nominal battery drops

The battery canister we are planning to use is a nominal 14.4V 13.4Ah battery that will be regulated with four heat settings, the maximum setting will be 12V. We may find that 11V is the highest that is needed - which would be even better, but we won't know until we get the first ones made and tested.

70W x 2 (12-14amps) will exceed the ability of a single BMS in the battery pack to handle the load. The compact BMS-s available are limited to 10A each. You will also need thicker wire in the battery itself and thicker or doubled up nickel strip in the battery. Net you will need 2x BMS, 0.15x7mm nickel strip, and 16ga wire at least up to your splitter to handle ~13amp loads.

I should have explained it in a little more detail, the maximum per individual circuit will be 70W, but the combined total will be limited to 110W by the number of heating pads fitted.

The 0.15mm thick nickel strip will be marginal in a garage grade spot welder.

The entire battery canister system will be made for us by a company that already makes them - they will just be providing us with a slightly modified version of what they already sell.

 

[RedSeaDiver2]

The other part is you don't need to run only 1 wire set. 18 is a nice size for connectors and soldering. You can run individual set of 22/24ga to each panel and really have unnoticeable wires but they are stupid fragile and a pita to solder and attach connectors

Any advice you or anyone else can give on how small becomes too fragile would be good. I've got to try to find some waterproof connectors for 18 gauge that aren't too big so that they become uncomfortable in the suit.

 

[rjack321]

Any advice you or anyone else can give on how small becomes too fragile would be good. I've got to try to find some waterproof connectors for 18 gauge that aren't too big so that they become uncomfortable in the suit.

Not a scientific flex test, but 18gauge is probably double the durability of 20ga. The more strands in the wire bundle for a given gauge, the more flexible it will be, but thinner strands also break easier. So it's a bit of a balancing act.

I'm curious what you are using for heat now?

 

[rjack321]

The battery canister we are planning to use is a nominal 14.4V 13.4Ah battery that will be regulated with four heat settings, the maximum setting will be 12V. We may find that 11V is the highest that is needed - which would be even better, but we won't know until we get the first ones made and tested.

Down regulating a 4s pack is ideal. But a 200wh pack is pretty modest. I would go up to a 250-300wh pack if you're willing to put up with the bulk. Especially if you are looking at 140W of potential power draw on high.