Heating Controller - Gloves vs Vest

[Leto]

I hope this is the correct board as this is a mix of questions about heating gear.

I'm rebuilding a BIG old Halcyon Pro 14 canister with a Li-Ion battery pack to power heated undergarments (gloves & vest/suit, not bought yet). I got some questions which I hope you can help me with, sorry for the long read ;-)

- 3S vs 4S pack. I can either build a standard 3S (11,1V nominal 12.6 peak) or a 4S (14,4V nominal, 16,8 peak) pack. Most vests/gloves/etc have their output rated at 12V. So the 3S will be underpowered most of the time and the 4S pack overpowered. Most of the gear I'm looking at (Santi, Yellow Diving, Lola, Heizteufel) is 'motorcycle' technology where more Volts translates into more heat (watts).

Has anyone experience with using a 4S 14,4V pack for heating? Santi states that only 12V should be used but i'm not sure, aside from heat output, why 14,4 should be a problem (connectors maybe?).

One option would be to go with a 4S pack and the use a heating/pitkin controller set on 80% to bring down the heat in the beginning of the dive when pack is peaking and set the controller to 100% when the pack voltage is dropping later.

- A different strategy would be to build a 7S pack (25,9 nominal) and then use a buck converter to bring it down to a steady 12V. However all good buck converters are either way to big or get way too hot when doing more then 100W for multiple hours. I know UWLD has pulled this off, hats off to him.

- Gloves vs Vest. I've noticed people commenting that heated gloves are never too warm, no reason to turn them off or reduce output. However, for the vest people mention that they often turn them off or down for different reasons (prevent on-gassing / save battery / simply too warm). So using a pitkin controller works fine for turning down the vest output but also reduces output of the already 'not so warm' heating gloves.
A solution would to use a Yellow Diving shirt (with a build in controller 100%/50%, switched by toggling the canister on/off) and heated gloves and no pitkin controller between the pack and heated gear. Any thougths on that?

Thanks!

 

[rjack321]

The pro14 canister is too big and heavy unless you are doing through dives at Plura or something crazy. That is like half a day of heat. A ~175wh battery (15ah li-ion in an old 9ah NIMH canister) is about 3 hours of useful heat with a 50w vest.

4S in a 12V vest is insanely hot (~65w). You'll be dropping it to 30% power for awhile.

100w+ for multiple hours? Are you planning on going naked with just a heater in a shell suit or something?

 

[Leto]

I got the canister almost for free and I want to make good use of it. Yes the canister will be heavy in the surface ~11 lbs (~5 kg) but less then 1 lbs (0.5kg) negative in the water with ~400 wh inside. I can always put a smaller battery in there to make it neutral but the difference in price is minimal.

I want to use the heat for doing 2h dives in 5c (41 F) water (fresh water lakes) with a scooter so aside from a vest/suit i'll be wearing heated gloves also. My hands are freezing after 50 min now (drygloves showa 720, bz400). I'm planning on 100W for the vest and gloves and want to have atleast one extra hour of heating for unexpected events. These are all non-deco dives, I just hate diving cold.

 

[in too deep]

I don't have any experience with building battery packs, but i do have experience with the Yellow Diving shirt, this is my second one.
I use the shirt's built in controller to adjust the heat as you suggest. I've wired a pair of SF Tech heated gloves to the input side of the controller so they get full power whenever the canister is on and the shirt gets 50% or 100%.
I wear the shirt directly against my skin with a marino wool sweater over top plus other wear.
The gloves never get hot but do take the bite off.
The shirt - I typically leave it on high for colder temps and adjust to 50% when needed.

 

[rjack321]

I got the canister almost for free and I want to make good use of it. Yes the canister will be heavy in the surface ~11 lbs (~5 kg) but less then 1 lbs (0.5kg) negative in the water with ~400 wh inside. I can always put a smaller battery in there to make it neutral but the difference in price is minimal.

I want to use the heat for doing 2h dives in 5c (41 F) water (fresh water lakes) with a scooter so aside from a vest/suit i'll be wearing heated gloves also. My hands are freezing after 50 min now (drygloves showa 720, bz400). I'm planning on 100W for the vest and gloves and want to have atleast one extra hour of heating for unexpected events. These are all non-deco dives, I just hate diving cold.

The 14ah SLA can is going to be about 800wh as a li-ion. Unless you are stashing it for long decos in a cave its an insane amount of bulk that is just extraneous. Plus its hard to even use enough of that capacity to draw it down into the storage voltage range.

A 100w vest is too hot all in one place - seriously that is going to burn you. Nobody even makes a vest this powerful for a reason - to use that amount of power over that small of a surface area means it will be crazy hot. The Santi heated suit is 100w and that is spread all over your body.

I've done 3 hours in 3C with a 50w vest mostly running at 30W with no heated gloves and the last hour I wasnt even moving - and I am very cold blooded. Coming from no heat at all I think your sense of scale is a bit off kilter here. Assuming you have a decent undergarment and hood you don't need that many watts to be comfortable. Besides you should always be prepared to finish the dive without the heat if it dies.

I would replace that bz400 unless it is nearly brand new. The weezle extreme+ is FAR more durable. If you really want 100w then get the santi full heated undersuit, just expect it to compress down and lose loft fast.

An extra unplanned hour on a non-deco dive in 5C water? Sorry but why, just get out.

 

[Leto]

First of all thanks for sharing your experience with cold water diving!

I”m not putting a 800wh pack in the canister, ‘just’ a ~400wh one as i use a more robust and space consuming way of building the pack.

You are correct, I made some calculations (amp, voltage, resistance -> watt and temp) and yes 4s is way overkill for a vest.

Just a theoretical exercise. The full suit, which ‘feels’ less warm then the vest (more suit between wires and skin) COULD benefit from a 4s pack when voltage has substantially been reduced however would require a lot of dimming to keep the temp acceptable during most of the dive.

A good 3S (large parallel) pack and a vest and gloves with a pitkin controller seems the most efficient and simple solution.

 

[Leto]

Which vest are you using btw?