2s 18650 discussion

[BobC]

2S 18650 balanced wiring:
 

[blueridgedog]

BobC said:

2S 18650 balanced wiring:
 

Add a jumper wire from pin 2 to pin 3 on the balance connector as the chip expects voltage on that pin.

[mc0676]

Thank to the guy of post #66 !

If someone has a 3d printer here the project, i think to release it in a few day: http://www.thingiverse.com/thing:976359

[Mad Scientist]

For the benefit of anyone else reading this thread whose mind works the way mine does (scary thought lol) the numbers referred to are not pin numbers, they are cell numbers. Bridging 2 and 3 means cell 2 and 3 at pins 3 and 4, etc. Ground doesn't seem to be worthy of a number. Luckily the board is very forgiving of screwing that up (guess how I know lol). My latest DNA 133 creation is now done except for the 510. Hope to finish that up tonight. Pics will be forthcoming.

[mandro]

I also messed mine up on first attempt, originally I bridge the two centre pins. I also wired the balance tap using turbo's idea with ground and pin 2/3 going directly to the board, leaving just pin 1 connecting to the battery, it's working great.

[Thatguy]

tonyisballin said:

http://scriptasylum.com/rc_speed/lipo.html

 

 

Given this setup: Does anyone know for sure what would happen if I simply jumpedd 1,2,and 3 to the same power lead. They would all get power. 


reason being, i have a mod with stacked 18650's, in a tube, can't get to the middle where the cells are touching.

[Dejay]

I think I've read somewhere that you can set escribe to passthrough (no balance charging) for that case.

[Thatguy]

Dejay said:

I think I've read somewhere that you can set escribe to passthrough (no balance charging) for that case.

awesome, thank you, I sure hope so. 

[Mad Scientist]

Thatguy said:

[QUOTE=Dejay]I think I've read somewhere that you can set escribe to passthrough (no balance charging) for that case.

awesome, thank you, I sure hope so. [/QUOTE]

If you're using actual batteries with no balance tap, your best bet is to bridge the taps with resistors to the batteries (if you use the "power supply" setting with actual batteries, it seems the mod won't handle low battery cutoff or have a settable battery meter).

Use 3 identical resistors, something along the lines of 1k to 2k.  I'd recommend 1% resistors or better because they don't cost much for a few and it's more likely that the DNA 200 would then read the "virtual cells" as balanced or at least within 1%.

Using the notation for the balance tap of pins 1 to 4, pin 1 is ground: connect B+ to pin 4, run a resistor from pin 4 to pin 3, run another resistor from pin 3 to pin 2, run another resistor from pin 2 to pin 1, connect pin 1 to B-.  Basically creating a voltage divider.

The DNA 200 will read the divided voltage across the resistors as "virtual cells" and operate normally.  

MAKE SURE (emphasized) you set the USB charge current limit to 0.  You don't want it to try to charge with no actual balance tap.

[UKDTweak]

Just want to check i have the Watt hour cal settings correct, i have 2 2800 mAh 18650's, I have the mAh set to 2800 and im assuming i set the nominal voltage as 7.4v?
And should i leave the soft cell cut off at 3.09v or set it to 6.2v?

[Thatguy]

I'm running stacked 18650's (2) and I am running a ground, power in and power out to atty. I set it to power supply mode and it's working great. For the record: stacking or series cells require special caution and procedures. Balance port is not used.

[MuTong]

I want to use two 18650 batteries instead of battery in vtbox200. Space(72*35*22mm) should be able to lay down 18650?2 battery box.
1.Can I just connect the output line  to the dna200 chip and USB only for updating the firmware?
2.Annex can be used for all 18650 * 2 ?
3.I have to do is to update the discharge curve, choose 2-cell?

[UKDTweak]

1. A standard dual battery sled might not fit, think they are 37mm+ typically, an 18650 battery is typically around 18.2 to 18.5mm in diameter, so two side by side = 36mm+, too wide for the 35mm room you say you have.
2. Yes and no, you cannot plug in the USB Just for software only and therefore need to connect the taps for battery balance/charge.
3. Set Escribe to 2-Cell, then run the Watt-Hour Calculator, type in the mAh of just One of your 18650's, then in Nominal Voltage enter 7.4.

[Mad Scientist]

MuTong said:

I want to use two 18650 batteries instead of battery in vtbox200. Space(72*35*22mm) should be able to lay down 18650?2 battery box.
1.Can I just connect the output line  to the dna200 chip and USB only for updating the firmware?
2.Annex can be used for all 18650 * 2 ?
3.I have to do is to update the discharge curve, choose 2-cell?

Great minds can differ so I have a different opinion for answers lol.

1. In device monitor under "Diagnostics" choose "Set USB Current Limit" and set it to 0.  This will disable USB charging if that's what you want. Read on though -- that's not what you want.

2. I don't know what "Annex" means in this context.

3. If you are using 2 batteries, select 2 cells under the Mod tab in device monitor and setup the Wh capacity of the pack using the calculator.  Now you want the low cell cuttoffs to work to avoid destroying your batteries, and having the battery meter work would be a plus also, not to mention having USB balance charging work.  At the balance tap using the pin numbering convention of pins 1 through 4, pin 1 is "ground," connect pin 1 to B-, pin 2 to the junction of +- on your two batteries, pin 3 to pin 4, pin 4 to B+.  If you do this, USB charging will work, low cell cutoff will work and the battery meter will work.  If you don't do this, you're on your own lol.

[MuTong]

Thanks UKDTweak and Mad Scientist,
I don't have a clear description of my question.
Even if I do not use USB charging function(external charger), all of the connecting line is necessary?

[Mad Scientist]

MuTong said:

Thanks UKDTweak and Mad Scientist,
I don't have a clear description of my question.
Even if I do not use USB charging function(external charger), all of the connecting line is necessary?

One problem with not using any of the balance connector pins and just telling the mod it's a power supply is there will be no low cell cutoff function and the battery meter won't work. That combination spells a lot of damaged batteries and possibly flames and fire when you try to recharge them externally. It's only a few wires to connect it all properly and well worth the effort.

[MuTong]

Thanks  Mad Scientist,
I will try to re weld all the connecting lines.

[wojzilla]

So I've changed my mod to 2x18650 from lipo.
I've loaded the LG HE2 curves in this thread and I'm finding I get "Weak Battery" warnings when the capcity is at 40%
When I had a lipo i could "run it dry" ie down to 0% or close enough to.

2x Samsung 25R 2600 mAh
Calculated capacity 21.84 Wh (2Cell)
Voltage on Cell 1 3.71
Voltage on cell 2 3.71
Pack voltage 7.42

when firing
Cell 1 3.09
Cell 2 3.16
Pack voltage 6.25

firing Watts 111.8

Looking at the cells when firing i can understand why i get weak battery warnings but the battery life seems so much shorer than when using a lipo - is this normal?
Without hard stats it feels that the DNA doesn't last as long as say an x-cube 2

Does anyone have a curve for Samsung 25R batteries?

[VapingBad]

I would depend on the power setting, the higher that is the higher the voltage sag and once it gets to 3.09 V on either cell the DNA will consider it flat, you can lower the 3.09 V to 3.0 V but I think that is the min.

[UKDTweak]

For your comparison:

Im using 2 Efest 2800mAh batteries, bought two pairs to match, the first pair gave me 578 puffs at around 5 seconds a puff, 100w 1s pre heat, punch 5, and mod set to 40w, before it showed Weak battery.
Running a .2ohm Titanium single coil in temp mode... and i set the soft cell cut off to 3.2 to be safe....

Edit: forgot to add i am using the default curve that was already in escribe.

[VapingBad]

And the age of the batteries can make quite a difference.

[wojzilla]

All makes sense to me, I just wish I paid more attention to the lipo battery levels to get a better understanding. Do they get less sag under load?

What i'd like is for the battery level to show 10/20% before it hits "low battery" but i guess that's dependent on power being put through it.

[VapingBad]

This shows how much small batteries sag under load.
http://www.kidneypuncher.com/18650-battery-tests

[wojzilla]

Champion! Cheers

[UKDTweak]

I have Escribe soft cell cut off set to 3.2v and when I finally got the weak battery message with the dual 18650's, I connected up to escribe and ran the monitor, the batteries were showing as around 3.45 to 3.55v but when I fired the mod they dropped to 3.2 and weak battery was displayed again.