Question Looking for advice / sources on a new suit-heater battery

[stretchthepenn]

TL;DR: I need a new heater battery pack that fits in a DiveRite can (52mm diameter, 143mm length; trailer connector).

First off, yes, I know that if I'm really serious, I should get a Light Monkey / Underwater Light Dude battery with a Pitkin controller, but I'm not doing five-hour cave dives, and I ain't got the cash for a honkin' battery right now. If that's the comment you intend to leave, then please buzz off, kthxbai. On with the post...

I frequently dive a quarry that's ~51F at the bottom, and my runtimes are starting to exceed two hours. I typically wear a wicking base layer under a 4th Element Argon jumpsuit, and these do a good job, but I usually get chilly about 3/4 of the way through and start shivering. Thus, I've used a Light Monkey heated undershirt (35.300.-Heater Base - Top), particularly during the winter months, to ward off the chill.

Problem is, my battery pack, which I bought a few years ago used, is dying/dead. It's a 12V 4.5AH NiMH pack that fits into a converted Dive Rite light can. The pack's dimensions are 52mm x 143mm, and it has a trailer connector.

I've found the actual replacement battery pack (NiMH Battery Pack: 12V 4500mAh (54Wh) for Diving light) but I'm wondering if I can upgrade to a more capacious Li-Ion battery that fits in the same space.

Do you know if such a thing exists, or do you know somebody who's an expert on battery packs of this nature?

 

[Whitrzac]

I've built a 4s7ah pack into these cans. Could fit a 3s7ah too.

The 4s is nice if you're using an external liken controller and can turn it down

 

[greeniguana]

These would fit, but they are 14.4v.

 

[grantmac]

I'll piggyback on this question since I have a similar can and considering a similar build.

Is 3S worth doing to avoid needing a controller? Or can a fixed DC/DC converter be used inside the can to limit it to something like 10v?

 

[Whitrzac]

A controller like that generates heat, and there's not a lot of room for one

 

[grantmac]

I suppose another simple system would be a switch to go from 2S to 4S. Not hugely variable but simple and inexpensive.

 

[stretchthepenn]

I've built a 4s7ah pack into these cans. Could fit a 3s7ah too.

The 4s is nice if you're using an external liken controller and can turn it down

I'd probably go for a three-cell package, as I don't have an external controller; my can has a simple on/off switch that I toggle as needed.

How does the build work? I've been looking online, but most of the instructions are crap.