Need DIY guide for high power LiPo box mod

[Derrick Wang]

I'm very interested in learning how to build my own LiPo box mod similar to the Gen Two 504w Mech. i've been searching for information throughout this forum but i'm quite confused and still need a lot of information. the closest i've seen is someone's DIY 450 watt box mod but he doesn't use lipo.
currently i vape on 18650 mech's at 0.09 ohm and my average VD is 0.5, and typically run through 2 vtc4's a day. i'd like to have a 8.4V mod capable of upwards of 500watt (overbuilt) and last me at least a full day or more (4000-6000mah?).
thank you.

 

[novamatt]

Any standard mech box build should work, you'll just want to substitute your lipo in place of the 18650(s). With that kind of power, you should definitely be using fuses and a mosfet, and you want to make sure you pick materials (battery, wire, etc) that will handle the amperage load. Multiple-cell lipos need to be charged carefully, so you're going to need a good lipo balance charger as well.

Honestly, you're looking at almost $100 just for your battery (about $40-50) and a good charger ($30-40). Once you add in the other parts, time to put it together, and the stuff you'll need to learn to do it safely, $180 for the Gen Two doesn't look so bad.

 

[Derrick Wang]

i'll definitely be wiring in a fuse and mosfet. all i have figured out right now is what i'd ideally want which is:
1. all day power at ~200-300 watts (currently vaping 100-135w with VD in consideration on my 18650 mechs)
2. bottom feed
3. cut out on box for charging ports

going by what i have found, the hammond 1590N1 would fit a Turnigy 4600mah 7.4V battery. the issues are, aside from learning how to wire, is figuring out if there is sufficient room for a juice bottle inside still, how to make square cutout for the battery charging ports. i'd like to add a simple volt meter but that also requires a square cutout. i dont want this to come out looking totally diy job with crooked/jagged cutouts. if i had carpenter skills, i'd make a custom box out of wood.

as for wiring the lipo, (Turnigy nano-tech Ultimate 4600mah 2S2P 90C Hardcase Lipo Short Pack (ROAR Approved)), i dont know if it's worthwhile taking it out of its hard case in an effort to save space. this guy's guide on it doesn't seem to show that much space savings: Converting a Hard Case Lipo to a Soft Pack - RC Groups

at first i had eyes on the gen two mech but i think this build would trump it easily with the bigger battery capacity and bottom feed. plus it'll give me knowledge on how to build future/better mods

 

[novamatt]

Sounds like you've got a good idea of what you're doing - if you don't have a full metalworking shop, the easiest way to do a square cutout is to drill the 4 corners and then clean up the sides with a small file. You end up with a nice square with rounded corners, but you need to be pretty precise with the drill. The other option is to drill the center and then file outward into a square shape.

If you can fit it into the enclosure in the hard case, I don't see any reason to take it out. It's not a significant space savings and it IS a significant reduction in physical protection for the battery. The only good reason I'm aware of is if your screw holes in the hammond interfere with the corners of the hard case. I'm not familiar with that particular hammond box or the lipo, so I can't help with fitting the juice bottle in. Best suggestion is to mock it up out of cardboard or something and see how you can make everything fit. Make sure you leave extra room to work with the wiring... at some point in the process, you're going to have to solder something while it's installed in the case, even if you're planning not to. Something will need tweaking, and working inside those tight spaces is a pain.

 

[Derrick Wang]

After trying to source a better fitting box, I can't seem to find a better match than the 1590N1, so the juice bottle will have to be squished a bit.

I'm still confused as to how the wiring needs to be done for the battery. The pictures that show in the link I provided above show that the Turnigy comes with loose positive and negative lead wires. I'm not sure how I'm supposed to work with that in terms of creating a charge port for the charger. I'm guessing I'm going to have to find a suitable connector for it, but I don't know which one.

I'm starting to think this project is beyond me considering I don't have any experience doing this and there isn't any step by step DIY wiring guide for lipo's

 

[tj138waterboy]

I'm right there with ya on this mod. Any luck with wiring info yet?

 

[tj138waterboy]

Some parts that may help you on this journey are http://www.e-cigarette-forum.com/forum/modding-forum/654141-new-builder.html

 

[tj138waterboy]

Finally got mine built.
1st time build disaster, kinda

 

[Tbev]

That is dope!

How much were those lipos each. How long do they last with what build? What charger do you have.?

 

[tj138waterboy]

Lipos were about $12 each I just got a charger for them yesterday but I ran them for 3 days medium vaping on 1.7 ohm dripper and they went from 7.7 to 7.55 and charger is a cheap clone gt power a607.

 

[twgbonehead]

Very nice job! I'd just like to mention that you really need to be careful with the LiPo packs! These are designed primarily for applications where the battery is not right up against your face! And this battery technology CAN catch on fire, even while it's not being used or charged (particularly after a heavy discharge session).

A co-worker's son had an RC helicopter, one day, after flying it, he left it on his bed.

About 5 hours later, my co-worker heard a loud bang, and ran into the bedroom to find the whole bed on fire. Fortunately he was able to scoop up the whole mess in the blankets and get it outside, but if they hadn't been home it's likely the whole house would have gone up in flames. There was nothing wrong with the wiring, apparently the hard flying session caused a micro-short internal to the battery, which slowly grew over the next few hours until it went into runaway.

So be aware of the characteristics of these batteries and stay safe!

 

[chefjoosie]

Very nice job! I'd just like to mention that you really need to be careful with the LiPo packs! These are designed primarily for applications where the battery is not right up against your face! And this battery technology CAN catch on fire, even while it's not being used or charged (particularly after a heavy discharge session).

A co-worker's son had an RC helicopter, one day, after flying it, he left it on his bed.

About 5 hours later, my co-worker heard a loud bang, and ran into the bedroom to find the whole bed on fire. Fortunately he was able to scoop up the whole mess in the blankets and get it outside, but if they hadn't been home it's likely the whole house would have gone up in flames. There was nothing wrong with the wiring, apparently the hard flying session caused a micro-short internal to the battery, which slowly grew over the next few hours until it went into runaway.

So be aware of the characteristics of these batteries and stay safe!

Yes , on lipo packs you need to leave quite a bit more headroom than on imr 18650s. The lipo pack you chose is a great choice. You'll never get anywhere near the discharge rate in a PV unless you short it.

 

[tj138waterboy]

Yeah I just crunched the numbers and in parallel 40c 1650 mah, (80C 3300 mah continuous discharge is 264 amps). I have 18 amp fuse to limit the device because I will be adding a li-ion pack with xt-60 connector. I don't think the lipo even knows it's being used. BTW I don't plan on sub ohm'ing in any case. This thing hits harder at 35 watts than my friends sigelei set on 100watts

 

[tj138waterboy]

Given the right mosfet if there is one that could handle the amperage and no protection fuse, in theory my build can safely drop down to a .032 ohm coil and still be under the safe amp draw limit at 2,205 watts at 8.4v.

 

[twgbonehead]

Yeah I just crunched the numbers and in parallel 40c 1650 mah, (80C 3300 mah continuous discharge is 264 amps). I have 18 amp fuse to limit the device because I will be adding a li-ion pack with xt-60 connector. I don't think the lipo even knows it's being used. BTW I don't plan on sub ohm'ing in any case. This thing hits harder at 35 watts than my friends sigelei set on 100watts

Careful there! When putting the batteries in parallel, you can add the mAh, but the C doesn't change, so your max is only 132 amps!

(Still should be more than sufficient, though!)

 

[chefjoosie]

Given the right mosfet if there is one that could handle the amperage and no protection fuse, in theory my build can safely drop down to a .032 ohm coil and still be under the safe amp draw limit at 2,205 watts at 8.4v.

Still a bit short of the Legalvape 4000 but I guess it'll do.

 

[tj138waterboy]

Careful there! When putting the batteries in parallel, you can add the mAh, but the C doesn't change, so your max is only 132 amps!

(Still should be more than sufficient, though!)

I thought that too about C rating but went back and verified and parallel shares the workload so double the amp rating but keep C rating if that makes sense. So 40c is what it actually is but with 80C discharge capability.

 

[tj138waterboy]

Still a bit short of the Legalvape 4000 but I guess it'll do.

Phil Busardo is too hardcore some times.

 

[twgbonehead]

I thought that too about C rating but went back and verified and parallel shares the workload so double the amp rating but keep C rating if that makes sense. So 40c is what it actually is but with 80C discharge capability.

No. Think of it this way. A single battery, 40C, 1650 mAh can supply 66 Amps. 2 in parallel can only supply twice the amps, so 132 amps.
The second battery doesn't allow the first one to discharge any faster, it just adds its own current to the current supplied by the first one, if that makes sense.

You might think of it like a 1650 maH battery with an 80C rating (that wouldn't be correct, but it would be closer). But putting them in parallel definitely does NOT double both the C rating and the maH rating, you're counting the same thing twice!

 

[tj138waterboy]

Ok got it now. So I'm safe around .064 ohm coil 8.4v 1,103 watts. Should be drawing 131 amps safely.