Building a Lithium Ion Battery Pack. Need help.

My goal is this:

To be able to power a 21W HID bulb for 3hours using AA sized lithium- ion batteries and to charge them using one charger. Basically I am building an underwater canister dive light, but I'm not 100% on the battery pack and how to wire it.

I understand I can buy a bunch of batteries at ~3.7V each, but I need to know how to wire them up to the PCM and other such niceties. If someone could point me in the right direction, that would be excellent!

Let me know if anyone could tell me what I'll need to make this so.

Thanks,

Reply to
Bighiller
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And you wanna trust your life to the low life yahoos on this group!?

Never heard of AA 3.7V lithium ion cells. You got a link?

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"Are Lithium Ion batteries available in standard sizes like AA , C or D cell size? No, Lithium-ion batteries are not available in standard sizes. "

I'd point you in the direction of a diving supply store. And of you still want to build something like this yourself, I'd point you to a stretcher in the back of the truck driven by the men with the butterfly nets.

Reply to
a7yvm109gf5d1

A 63 Watt hour AA sized battery would be quite a trick. You could go voltage I suppose, and have a *lot* of batteries, but they why limit yourself to AA sizes? That said, there is no such thing as a AA sized lithium battery anyway.

Reply to
PeterD

link?

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He is probably talking about 18650 cells. They are slightly longer and wider in diameter than AA cells.

Lithium-ion batteries require more attention to safety than nicad or nimh.

Reply to
bob9

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James Arthur

Reply to
James Arthur

Confining a large lithium-ion pack in a pressure-tight container is DANGEROUS. Be careful.

A safety vent's a good idea.

Best of luck, James Arthur

Reply to
James Arthur

I Would rather have a nickel-iron battery pack, very long service life. You could use 5 nimh D cells 12ah.110 dollars. You would need 22 li aa cells 0.8 ah at 75 to 150 dollars. This is what you are competing with

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Bob

Reply to
<castlebravo242

Absolutely. My camera takes them. They are nifty gadgets! The batteries have a tiny circuit board built right in the end that handles all the electronic sensing and charging folerol for Li-ion batteries too.

Reply to
Benj

could use 5 nimh D cells 12ah.110 dollars. You would

competing with

I don't get this:

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"Through Case Charging - Reduced possibility of leakage due to seal damage"

It looks terminals are in contact with sea water.

M
Reply to
TheM

I downloaded the data sheet for JJJ-LC14500 and it did not appear to "handles all the electronic sensing and charging folerol for Li-ion batteries too"

Reply to
IanM

That's a nice thing to say. And useful too.

Buddy, just keep your useless comment to yourself. You know jack and squat about what I am doing and you just want to seem like you know something....which is doubtful.

Good luck with that.

Well, thanks for the useless comments, they've made all our lives better.

Reply to
Bighiller

I've check batteryspace.com and they have A LOT of lithium ion batteries and chargers, but I can't make out exactly what I need. It's a matter of wiring the batteries together and getting the right charger. As for the size, well I don't really care, so long as they fit into a 2"x~12" PVC tube (roughly).

Reply to
Bighiller

Yeah, I think I was.

This is understand, hence my posting.

They will be in a sealed container, but not permanently sealed. It's a canister dive light, using PVC, proper O-rings, etc. SS latches hold the top on making an air-tight seal.

Reply to
Bighiller

I understand that, but it shouldn't be a problem as the pack would only be sealed for ~2hrs MAX. It's a dive light and I don't plan on any LOOOOOOOONG dives.

Reply to
Bighiller

A diode on one of the terminals would probably deal with that, and also protect against a reversed connection.

Bob

Reply to
<castlebravo242

wrote in news:2fqAl.14737$8 snipped-for-privacy@flpi147.ffdc.sbc.com:

how do you recharge it then? the diode would block charging current.

--
Jim Yanik
jyanik
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Reply to
Jim Yanik

The diode would block the discharge current. The diode is between the battery and the positiveterminal of the charger input.

Bob

Reply to
<castlebravo242

CONNECTION: several cells in series, or series-parallel, to get the voltage the HID needs.

SAFETY: you need battery pack electronics, thermal switch, + a one-way valve (vent) for the containing vessel.

The battery pack electronics protects each cell in the series pack against reverse voltage, overdischarge, overcharging, and the entire thing against short-circuit. The thermal switch (PTC, positive temp. coefficient thermistor) is built-in to many LiIon cells' anode contact. It's a back-up short-circuit protector.

Numerous vendors offer pack electronics configured for common pack voltages.

CHARGER: current-limited to C/2, voltage-limited to 4.15v per cell.

You might consider the 18650 size cells--they're the standard, bigger, stronger, and cheaper. 14500's not so much.

The dangers are many--LiIons will vent with flame if abused, sometimes not for hours or days after the insult. I don't know how they'll like being pressurized.

You need the one-way safety vent. They're common, and cheap. Otherwise, you're making a pipe bomb.

HTH, James Arthur

Reply to
James Arthur

-

The canister will only be air-tight with no-venting as I am in the water (max ~1hr). The pressure inside the canister will remain at

1bar, while the outside pressure on the canister will max at about 4bar. The battery pack will be housed in a air-tight/water-tight (both) canister for the dive. The battery pack will be contained with heat shrink wrapping. The batteries will NEVER (as long as I can help it) come in contact with water. As for the venting, please, if you could, explain why I need to vent this canister? The battery pack will stay in there only while on my dive and it's not likely to create an explosion underwater. When you say vent, do you mean out of the battery pack or out of the canister?
Reply to
Bighiller

I mean that if and when the battery pack catches on fire, a vent will keep it from killing you. The excess pressure has to have an escape all the way to the atmosphere, otherwise it'll build up, burst and shred most any container. That throws shrapnel, fire, and incandescent burning metal everywhere inside your car, boat, or backpack.

It doesn't happen often, but it happens.

Vents are common in flashlights, even dive lights IIRC. They keep external pressure and water out, but let internal pressure escape.

One method uses a silicone rubber plug--it'll pop out under overpressure conditions. Another is a simple seal arrangement that compresses and seals tighter under sea pressure, but which lets internal pressure out. AKA "check valve."

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battery / plug | .--..--. | --> (== | || | | | | || | | | | || | |

Reply to
James Arthur

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