Raptor Flip-Top VV Mod with 20A, 120W dc/dc converter...

[mamu]

I usually buy resisters here: 1/4 Watt Resistors 5% Carbon Film

I used a 220 ohm resister from there, but for the 7.5K pull down resister I wanted a tighter tolerance, so I bought this one: RES 7.5K OHM 1/4W 1% AXIAL

 

[mamu]

hey BJ - I was thinking since you're using li-poly cells, maybe you should go ahead and up the zener breakdown voltage. Li-poly batts usually need a low cutoff voltage of 3.2v per cell (6.4v series) under load.

I set the 6v cutoff for cylindrical 18650 batts. I'm thinking of upping that 5.6v zener to maybe 6v. Metering the batts, the dominant batt read 2.75v and the other read 3.44v. I really don't want a batt going below 3v.

 

[BJ43]

hey BJ - I was thinking since you're using li-poly cells, maybe you should go ahead and up the zener breakdown voltage. Li-poly batts usually need a low cutoff voltage of 3.2v per cell (6.4v series) under load.

I set the 6v cutoff for cylindrical 18650 batts. I'm thinking of upping that 5.6v zener to maybe 6v. Metering the batts, the dominant batt read 2.75v and the other read 3.44v. I really don't want a batt going below 3v.

Thanks mamu, I went ahead and ordered the 6.2v zener and will replace the 5.6v and also use it on the new Raptor coming. I used a 2 wire meter on the first one, but on the second I will wire a 1S-6S voltage reader so it will show each cell and total.

 

[Dustin Brown]

Wow, this is awesome! I will build this. Any thoughts on which Hammond enclosure would best fit all this stuff inside?

 

[mamu]

I forgot - I was suppose to update this thread with the LG batts. They did awesome for longevity and cut out at 6.4v unloaded. Range 0.2-0.4v drop input load and remained 0.0 drop output load.

So the LG 30A 18650 batt has moved to #1 spot for me (because it has the longest run time) and the Sony 30A 18650 batt #2 spot (best unloaded cutoff voltage). Hope the LG batts will be readily available soon.

oh... I was doing a search and come across an old thread where we first started talking about the problems with these converters and low voltage cutoff and the problems with the lead batt discharging more... Low Voltage Cut Out

 

[BJ43]

Wired the 1s6s like we do in RC to monitor each cell. When the DP3T on off on switch is set to the imput side, the meter reads cell 1v then cell 2v then the total v of the two, both unloaded and loaded. Excuse the hand drawing.

 

[bapgood]

Wired the 1s6s like we do in RC to monitor each cell. When the DP3T on off on switch is set to the imput side, the meter reads cell 1v then cell 2v then the total v of the two, both unloaded and loaded. Excuse the hand drawing.

The CF background makes up for the hand drawing

 

[Dustin Brown]

Well, I did it! I really appreciate all of you making this so accessible. I posted pictures of mine on Reddit and used the wiring diagram because people were asking about it. Hope that is okay!

 

[mamu]

Well, I did it! I really appreciate all of you making this so accessible. I posted pictures of mine on Reddit and used the wiring diagram because people were asking about it. Hope that is okay!

Thank you for giving me credit for the work and wiring guide, Dustin. That's aces in my book and very much appreciated.

ETA: the 18A fuse is the hold current, the trip current is ~30A, so there is that current cushion before tripping.

 

[Dustin Brown]

Thanks for the reply. I have got the modding bug now! I already have a shopping cart filled up with makings of two more. I know I can do better with component placement and wire management if I do it again.

FYI the power this device can put out is ahead of what our current wicking potential is. I wanted to try it out on the upper end and got a dry hit at around a 100watts! This is with my coil sitting half submerged in a puddle of juice.

 

[nicotime]

Hey...that looks like a Star Trek communicator...I always thought you may be receiving advanced alien technology hints!!

Good to see your still at it Mamu.

 

[mamu]

oh. my. goodness. look what the cat dragged in.

Good to see you nicotime!!

 

[BJ43]

I have now charged the 4200 mAh lipo 6 times and can safely say both cells discharge equal. There is not a lower voltage on the lead battery.

 

[mamu]

You have the lipo tabs soldered one on top of the other and one lead wire coming from the positive and one lead wire coming from the negative, correct?

With using 2 cylindrical batts in series there is a junction wire or dual connected batt contact that is connecting the batts.

Not sure the whys of a lead batt, I don't always get a big voltage difference, or at least it's maybe one tenth of a volt off, but more often than not I get a voltage difference.

We talked about it a few years ago here: Low Voltage Cut Out

How is the voltage cutoff with the 6.2v zener, BJ?

 

[BJ43]

You have the lipo tabs soldered one on top of the other and one lead wire coming from the positive and one lead wire coming from the negative, correct?

With using 2 cylindrical batts in series there is a junction wire or dual connected batt contact that is connecting the batts.

Not sure the whys of a lead batt, I don't always get a big voltage difference, or at least it's maybe one tenth of a volt off, but more often than not I get a voltage difference.

We talked about it a few years ago here: Low Voltage Cut Out

How is the voltage cutoff with the 6.2v zener, BJ?

Yes two of the the tabs are soldered together to form the series, but theoretically one cell would still be the lead cell. I know lead cell drop exists, I have a lot of experience with large inverters for household emergency power. Personally have 2 24v 5 kilo 110v inverters with 24 large 240 amp 6v gel batteries that will run my house for 12 hours and the lead battery gets warmer and lower. Every six months I rotate the batteries.
My order from Digikey with a second Raptor and parts is in Miami, should be here tues. I have been recharging at 7 v and not letting it cut off...

 

[b0bl0blaw]

Mamu, thanks for posting this!

I built mine and got it mostly together. I used a hammond project box, 1590bsbk. Pretty large box but what I needed to fit my Orion 90c 4000mah lipo . It actually fits pretty well in my hands. I used Lexan for the front case similar to your Milo mod. The ports on the side are a female Deans connector and a small female JST connector that i'm using for the balance connector. I still need to figure out a way to plug these - any ideas?

BJ, thanks for the link for the 6.2v zener and the RC car battery idea. Luckily I pulled a 5 cycle old hard-case pack out of the trash at the RC track that one of our sponsored drivers threw away when one solder tab came loose internally. I broke it open and used the short lipo inside.

The wiring still needs to be cleaned up, lexan needs to be sanded and countersunk but here are some pics:

Raptor Milo - Imgur

 

[mamu]

YW and well done, b0bl0blaw!

 

[Dustin Brown]

How is everybody's low voltage cutoff working out? I switched to the 6.2v and it seems to be going well. I have made 6 so far. One of them cuts out pretty early. At 7.2 unloaded it will not work at the highest voltage. If i turn the potentiometer down just a touch it will continue to fire. Anybody else have anything like that?

 

[BJ43]

Smaller meter. Now to get bap to draw up a frame.

DC 2 5V to 30V Red Blue Green Digital Voltmeter Meter Power Monitor Panel Meter | eBay

 

[bapgood]

What are the dims of the regular one? I think the description dims says it bigger???

Bigger than this one at least Mini 0 28" DC 2 5 30V Blue Green Red Digital Voltage Panel Meter Voltmeter | eBay