SONAR II 17670 protected

Hey,

This thread is of interest to all of the members who bought themselves the murudai+dark_horse SONAR II kit.

For anyone who wants to use a boost driver with the sonar II, the 17670 battery is the ideal choice with its high capacity and ideal voltage for a boost driver. However, as daguin and other users found out it will not fit into the SONAR II. However, drlava was able to fit an unprotected (presumably bare) 17670 into his sonar. This poses an interesting predicament, the 17670 is without a doubt ideal for the sonar, however lithium batteries without protection are a disaster (kaboom) waiting to happen.

I am still waiting to recieve my kit, it is probably gathering dust somewhere in the customs office . I have however given quite some thought to the issue and have come up with and idea that, at least on paper, seems like a decent solution.

Retrofiting the protection circuit from the 17670 into the driver compartment, and using bare cells with the SONAR. It would be the ideal solution no need for dummy batts, a high capacity and no need for a diode, while still having the reassurance that the battery will not be discharged beyond its limit.

Since I do not have the sonar in house I cannot say whether or not it is possible due to size restriction etc. but I do have the batteries and the is quite a bit that can be trimmed of them to potentially make them fit.


What do you guys think, a possible solution, or a hit and miss?



thanks
brtaman

One possible solution, is to use a silicon diode in front of a FlexDrive. This would drop the 4.2 (full charge) voltage of the unprotected 17670 to about 3.5 volts. (.7 volt drop)

Using a FlexDrive, which needs at least 2.5 volts, the driver will stop working when the battery drains to about 3.2 volts, letting you know that it is time to charge. (before it gets dangerously low)

This is just a theory, I have not tried this... (I wish I got in on that Sonar project)

This set up would also give the option of using 2 X 3.0 volt lithium primaries!
Jay

RPL'S use 18650 unprotected no problems yet (now that I said that my unit will explode) lol

The RPL's have a protection circuit built into the laser itself. This is similar to the protection circuit that the protected batteries come with.
Jay

ahh ok that makes sense now

Thats actually a good idea jayrob, didn't even think of it. It would apply to all flexdrive users. I have the IgorT driver though, and I think it has a lower cut-off, which would put me in dangerous territory, gonna have to ask him. But the image of a lithium batt. popping inside one of a laser is not nice, (ive experienced a couple of batts exploding :, one time I wanted to run a vacuum electric motor from a 12v 10 amp power supply needless to say it was too much, then in an infinite show of wisdom i decided to use a AA batt as a resistor due a lack of parts...5 minutes into the "experiment" BAAAAM my entire wall covered in toxic sludge...good times.)

john_lawson no need to worry the RPL's driver has a protection circuit built in, it performs the exact same function (just probably better). From what i've read using a protected 18650 in the RPL is not a good idea, nothing will happen however there will be added resistance to the circuit, nothing drastic, but still everyone wants their laser running 100%.
****jayrob beat me... ****



brtaman

The protection circuit on the cells does a few things:

1) limits discharge voltage to (usually) 3V minimum
2) limits charge voltage to 4.2V
3) sometimes protects against overcurrent, but the cells can have protection for this internally, too

So, the only thing you need to worry about is 1) while in the laser.  
2) should be covered by your charging system.
Note that if you discharge the battery past 3V, it won't explode, it will decrease its capacity.  The recommendation of using a drop diode is a good simple solution.  But if you're not interested in the option to run 2 CR123s, you could in fact put the protection circuit right there in the laser chamber with the driver (with some trimming probably).    This would give you slightly longer run time and slightly better efficiency than the diode method.

Hey drlava,

The main reason I am iffy is that I have heard some horror stories on the RC forums I used to frequent, batteries puffing and worse. But those cells are put through much more brutal cycles, in my heli I use 25C cells exclusively (2ah x 25= 50 amp sustained output capability ), but I am very careful about runtimes and charging and discharging (7-10 minutes avg. runtime on my heli depending on how acrobatic I feel like being, but I have a timer on the TX), therefore have not had problems. Perhaps my paranoia stems primarily from RC and the tons of horror threads that I have read).

From what I have read 17670 cells are able to put out ~1.5C which allows for >2amp draw without problems so over-discharging them in not a prob, but the insane runtime per battery could lead me to forget about the batt voltage with a negative outcome. The main reason I am iffy, is if I go away for the weekend with the laser and use it a lot I am without a DMM, and do not want to piss of the gods of lithium.


Thanks
brtaman

Yeah those guys on the RC forums puff liths because they draw so much current the batteries overheat. we are drawing 25x less than that. If you can find a small generic lith protection circuit on DX or somewhere that would be perfect.

I ordered the protected 17670 ultrafire off DX. So the protection circuit is included. I have stripped the batt of the outer layer and filed down the protecton circuit to be inline with batt diameter, I then isolated the lead to the circuit using some sticky see-thru tape. I hope the batts fit this way, would be the simplest way.

Do you have any space left over when u pop a 17670 into the sonar or is it completely snug? The lead running the lenght of the battery is quite thin as is the tape, so maybe there is a chance. But if it doesn't work out, ill just recycle the protection circuit that came with the batt, if the idea works out I will have an extra one left over if you will find any use for it.


Thanks
brtaman

I have the Sonar 1 (silver) and it's pretty snug. In fact the threads were a little tighter than the bore so I had to sand them just a bit. From my measurements 664 mils is the limit of what will fit.

Uh oh, you got a SONAR I? I remember reading a post by dark_horse in which he stated that the 1st sonar had a larger bore Oh well, I will quit guessing until I have it in hand, theory only gets one so far...

664mils is 0.664 inch (IIRC?)...16.8656 mm ouch that is going to be tight crap.


Thanks
brtaman

My Ultrafire protected cells have a hard time fitting my Sonar II case. I can get the CR123A to fit in there, but not the 17670. The inner diameter of the barrel is around 16.7mm while the CR123A (without wrapper) is 16.56mm and the 17670 (without wrapper) is 16.82mm. So, one barely fits, the other barely doesn't. Really annoying that WL made the battery compartment so small.

Yeah it is really annoying and confusing at the same time... :-?

Oh well guess my dream of a nice 17670 SONAR II has gone down the drain -.- Oh well...I shall live on, but this scar will haunt me til the end of my days.


:

I'll be using a CR123a and a dummy CR123a with the Flexdriver. Should work okay

I got mine to work fine with a 17670 and it's a sonar II. I did have to take a dremel to the inside of the barrel and remove the sheilding on the outside of the battery. I'm not concerned about using a protected cell at all. but if it were an issue, it would be an easy matter of just adding it into the circuit before the driver.