Directly replacing NiMh cells with Li-Ion cells - bad idea ?

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

btw, do you have a DC clamp meter??

Aye. An UniT UT-210e. He's packed it back up unfortunately, so measuring stuff is no longer an option at this point I'm afraid...

[stj]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

there may not be discharge protection - ni-mh dont need it.
you can just run them into the ground and charge them just fine after.

btw, do you have a DC clamp meter??

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Vac works once again with the LiIon "mod" and I have mixed feelings: first of all, he's tested it under light load conditions all this time. Once you activate those roller brushes and they start dragging along the ground, I can imagine that causes additional load which may be detrimental to the cells. Overdischarge could be handled by the IC after all, despite the chemistry being different.
Second, the charging: as previously discussed, not sure if the IC that's in there is "tuned" for LiIon cells - different current, different voltages....all sorts of problems, so I definitely wouldn't sleep soundly after doing such a mod for a client and charging for it...

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Currently I just use my power supply to power it if I need to use it.

Yeah, a friend of mine did this with an ATX supply

[eccerr0r]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Yeah it's unfortunate that messing with li-ion cells by themselves can cost more than replacement cost, unless you get a good deal on the cells.

I don't know what I want to do with my handheld. Currently I just use my power supply to power it if I need to use it. Better to have a cord than to leave the mess on the floor...

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Pfftt...it got even better: just yesterday I was strolling through a mall and found the Li-Ion version of this Electrolux ErgoRapido, exactly the same vac on the outside, for almost the same price that was invested in the job my buddy is trying to achieve - I lost a bit of sh!t there No joke, I did the math: 2 sets of batteries, plus labour so far ended up costing the guy the same exact price as the Li Ion version off the shelf ! It's not even funny anymore !

On a side-note, I'm actually thinking of getting that one for myself as a smaller, more portable and ready to go alternative to my main Karcher vac I use around the house. I'd keep it round the kitchen to suck up crumbs and junk off the floor as well as to tidy up my car a bit every now and then. It's a good thing I had it round the shop, even in this semi-functional form, because it enabled me to assess its suction power, which is certainly not going to be on-par with a canister or mains powered vac, but still satisfactory for the aforementioned endeavors.....dat vocabulary tho

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Man, this thread is too funny!
Glad you're sharing this story ("repair"?) with us, Danny.

Odyssey more like
Glad you're having fun. I sure am (I'm such an ass, aren't I ?). Just yesterday he rummaged through the box of wall-warts hoping to find one of lower voltage to try and replace the 20v 200mA the vac comes with...don't know what he was hoping that would achieve, since I'm willing to bet that chip would just "UVLO" and would tell that inferior charger to f-off....he couldn't find one, so he abandoned the idea (thankfully ?). He's still fixated on the idea the batteries overcharge, but there's definitely more to it than that....current consumption, overdischarge, temperature...OMG. While it MIGHT just be possible the circuit DOES protect against overdischarge by cutting out the motor and probably blinking an LED or something, it's threshold is probably not "tuned" for LiIons...

Now about the circuit: it's actually not possible to "remove" the charge circuit by ITSELF, at least not with extensive mods, since the "system control" is part of that board I pictured in the handle and it's required for speed control, on/off and other functions. It's got a 1-button, 3-speed setting on it, as well as control for the roller brushes, so all those would be lost along with the board unless you have a lot of time on your hands to emulate those functions again.

It's about to get even funnier since he's not done with it yet, so I'm REALLY curious to see where all of this is going and how it shall end. That's another thing about this guy: he takes on 20+ different projects, starts work on several of them simultaneously, completes none, sets them aside, comes back to them after days/months/years(!), eventually completes (or half-asses) some of them and hands them back AFTER said time period. No joke: just a couple of days ago he returned some doohickey that's sat in the shop for 3 years ! 3 ! (Actually it was I who eventually fixed it, but NVM >_>) Big surprise: the chap on the phone had no idea who we were and what that device was - took a few minutes to reenact the whole story to him. Needless to say by that point he had purchased a replacement for said device....so now he has a backup At least props to "Mr. Knowitall" for being persistent, what can I say...

[momaka]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Man, this thread is too funny!
Glad you're sharing this story ("repair"?) with us, Danny.

so a question:
if the old fuck was willing to buy new pink-fire li-ions, why the fuck didnt he go to ikea and buy a pack of ni-mh's

LOL. Probably because it makes too much sense.

A fairly easy alternative method would have also been to rip out the charging circuit and build a simple LM317 voltage reg circuit and put a resistor to the Li-Ion cells for current limit, so that the reg circuit doesn't burn out when the batts are low and charging.

This "solution" of course still wouldn't address the batteries from over-discharging. But with a few MOSFETs/transistors, Zeners, and possibly a 358 op-amp, you could design a very crude shut-off circuit. But I imagine all of that is way over your "pal's" head.

Come to think of it, he should have just put a long cord on the vacuum and wired the motor straight to AC. Then tell the customer, when you want to use it, just plug it in.


Come to think of it, this is what a "technician" at a repair shop I worked at before did to some PS3 fans. He thought that since the PS3 fans are 12V and the AC line is 120V in the US, they would just run "10 times as fast".
The result can be seen in this thread, where I actually managed to repair his mess.
https://www.badcaps.net/forum/showth...ht=playstation

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Well LiIon always sounds better than NiMih, doesn't it ?

"Pink-fire"....I see what you did there

[stj]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

so a question:
if the old fuck was willing to buy new pink-fire li-ions, why the fuck didnt he go to ikea and buy a pack of ni-mh's

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

UPDATE: the solution ? Tell the client to simply not to leave it plugged in for charging more than 6 hours

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

we call that the "tight ass" method here.

Ditto

[sam_sam_sam]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

we call that the "tight ass" method here.

Boy did you say a mouthful

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

UPDATE: here's the IC at last: a MC9s08sh8, so it's like a "computer" in there, making the job even harder, since it's likely going to do "UVLO" if he tries to modify just the incoming adapter voltage in an attempt to decrease the charge voltage, or sense any number of different things. "Charge voltage" is a bit of a misnomer in this case, since it's not the sole factor - CURRENT is just as important of course...

[stj]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

we call that the "tight ass" method here.

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Yeah, but he's trying to do it "as is" with what's already in there, that's the catch

[sam_sam_sam]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Not really if you take out the charging controller board that is in there now and replace it with a battery charger controller board that is made for the type of battery that you want to use you can find them on eBay

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

Ok guys update: so my brilliant co-worker, who is a genius (he is ! a ge-ge-ge-ge-genius ) came back to this vac which he set aside for a few days and is still trying to hack the charger portion, which is probably a good idea at its roots, but not as easy to pull off with such a complex circuit in practice.

According to him, he discovered the batteries are being overcharged to 20v or something and that's what kills them....which is true - LiIons certainly don't take to overvolting as kindly as say SLAs do, so it's plausible, but adapting a circuit designed for NiMhs to charge LiIons is tough or maybe impossible IMO (and might be called a complete waste of time in the long run)...

[Dannyx]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

I shall find out on Monday

[stj]

Re: Directly replacing NiMh cells with Li-Ion cells - bad idea ?

so it burns down with lots of noise??