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

[eccerr0r]

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

We'll see how long it lasts and if it goes up in smoke. I don't know what protection this thing really has.

7.5 minutes is ⅛ hour, which is an immense load. 1.5Ah / ⅛h = 12A (in the "new" vacuum. The old battery in the old vacuum was 1.3Ah/⅛h = 10.4A) I suspect the Li-ion may last a few more seconds in the old vacuum due to 200mAh higher capacity...

[stj]

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

well you mention 10A, i would be surprised if the cell was rated above 4A
most small ones arent.

[eccerr0r]

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

The battery appears to be wrapped and no real good markings visible on it. I suspect it should be just as good as both vacuums have similar runtimes (~7.5 minutes) and initial battery capacities (3.6V@1.3Ah vs 3.6V@1.5Ah).

Heck the motor is about the same size too.

Well I put it together with some damage, the plastic seems to have gotten very brittle over the years. With the battery charged to 4.2V it seems that the charger has cut off. Have to see if it charges correctly after it's discharged a bit.

The vacuum cleaner really SUCKS now!!! Even compared with the original NiCd cells, then again the original NiCds were quite used up.

[stj]

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

post a photo of the battery markings so i can look for the spec.

[eccerr0r]

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

Well, I picked up another junk handheld vacuum cleaner for a buck. I grabbed it because it seems to still be spinning, and said "lithium 3.6V" ... Jackpot, it might actually match the specifications I need for the one I have.

I opened it up, and it appears to have a similar wiring diagram...battery straight to the switch and motor. It looks like it has a single small circuit board in it, wonderful, it's got to be a protection/charger board. Inspecting it closer...weird, no big FET on it? This thing needs to withstand 10A and no SOT-23 will do it, must at least be a D-PAK?

Oh well, so I pulled the battery and the circuit board and measured the voltage. It was down to 3V, which is probably still fine. Supposedly it's a 1.5Ah cell, and it says 3.6V, and appears to also be rated for 5.4Wh - so this is probably a lithium ion manganese cell versus a cobalt or iron phosphate cell. So I stuck it on an external charger bypassing the board, and see how it goes... up in flames maybe? Hopefully not, I still need to figure out how to charge this thing.

Well why not keep this vacuum and ditch my old one? The one I have is a wet/dry unit, and this one has a funky charger connector... Combine and get the best of both worlds.

[Dannyx]

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

(after all, I suppose you charge the customer after the item is fixed, correct?)

Yes, but in this case it's considered to be under warranty since the first set of batteries went kaput last time, so I don't think he'll be charged anything extra. I also just recently learned that it's not a client per-se, but rather another employee from a different department who asked him to take a look at this vacuum, so the rules are more relaxed here as far as fiances go at least...we'll see. No grudges against him - it's all a learning experience

You were right: I'm having just a little bit too much fun with this thread

[momaka]

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

Vac's still in the shop BTW, all packed up and ready to go. "Mr. Battery" called the client to come pick it up, but he hasn't showed up so far. Guess the chap is too afraid something might go pop and doesn't want to pick it up again LOL

Either that or the fact that it's been so long has perhaps made the owner realize they don't need this vac... or they already bought another one and don't want to come pickup this one because they don't want to pay the service fee (after all, I suppose you charge the customer after the item is fixed, correct?) In this last case, your friend, "Mr. Battery" will have a neat little vac to clean his bench... until it burns down the shop anyways... or the batteries die again.

[stj]

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

maybe the vac owner read this thread!

[Dannyx]

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

It's assumed that "he know what he's doing" given that's what he's employed for. There's no real way management can actually gauge a technician's performance and/or overall skills and knowledge, other than keeping a close eye on the service tickets they receive, how they go around handling them and how many they've actually successfully fixed.

[budm]

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

So the company gives freedom to do what ever he wants even it is dangerous.

[Dannyx]

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

So the company you work for will be reliable if something goes wrong?

Of course - there's a 3 month warranty period for all repairs, which makes perfect sense from the client's perspective (it's also in the law here AFAIK), but it can become problematic for the company if doing semi-functional repairs like these where something is bound to go wrong...

[budm]

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

So the company you work for will be reliable if something goes wrong?

[Dannyx]

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

Vac's still in the shop BTW, all packed up and ready to go. "Mr. Battery" called the client to come pick it up, but he hasn't showed up so far. Guess the chap is too afraid something might go pop and doesn't want to pick it up again LOL Occasionally "Mr. Battery" here gives it a whirl, sucks up some stuff and plugs it back in to keep it all nice and topped up and I'm like talking to those cells "hang in there, he'll relent soon enough"

[momaka]

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

Maybe the batteries burned so bad there was no evidence left of what caused the fire?

[Dannyx]

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

or he died in his sleep from smoke inhalation!!!

No police around here yet

[stj]

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

or he died in his sleep from smoke inhalation!!!

[Dannyx]

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

I find it interesting that the same mod he attempted on a similar vac is still working...or at least it hasn't returned. I can't tell if that's because the chap simply didn't use it or they simply got lucky...both of them

[eccerr0r]

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

I wonder how much longer NiCd/NiMH packs would last if there was an overcharge/overdischarge controller ... now that's a thought...

[momaka]

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

Odyssey more like
Glad you're having fun. I sure am (I'm such an ass, aren't I ?).

Well, yes and no (to all that). I mean, I would have probably done the same too, up to a point. But if I see someone is doing something stupid, I'd always offer to lend them a hand, even if it's likely to backfire on me (as in, the other person get grumpy about it, because they thought you are insulting their "intelligence". ). In any case, I would probably walk to the guy and jokingly throw a, "are you still working on this piece of crap"... then just "lightly" suggest that IKEA might have the real proper parts he needs to fix this and just get it done.

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.

Yeah, IDK... I personally hate battery-operated "power" tools and appliances. I consider them pretty much "disposable". The only batt-operated power tool I have is a hand drill / screw driver, and it's already been "converted" (more like kludged / jury-rigged) to run off an Xbox 360 PSU. It's kind of weak and slow compared to my corded drills so I rarely use it. But sometimes when I don't feel like walking to the garage to get my corded drills and need to drill into something thin / soft, the "Xbox 360 drill" (as I call it now ) does the job OK.

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.

Same with Ni-Cd.
Only problem with deep-discharging Ni-Cd and Ni-MH packs with series cells is some cells will discharge before others... and the ones that do could be forced to "reverse-charge" from still somewhat-charged cells. Neither Ni-MH nor Ni-Cd cells like this, so they'll get trashed over time. However, if you take the individual cells and deep-discharge them, you can keep them stored like that for years (and in fact is the preferred method for them, as it prevents dendrite growth).

it will probably be back!

LOL Very likely, yes.
Just like that song:
https://www.youtube.com/watch?v=LjMffHG1V_Q

Speaking of which... Danny, I think you should play that for your colleague while he's fixing the vacuum... see if he gets any hints.

P.S. I think I'm a bigger ass than you, aren't I? Or maybe we are just "disrespectful youth" as your OG colleague would say about us anyways.

[stj]

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

it will probably be back!
(hopefully not chared and in an "evidence" bag!!)