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

[stj]

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

laptop pulls? those are usually only rated for 2.8A continuous load before bad shit ensues!!

[Dannyx]

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

No, they were bought brand new by me personally from a local shop, though I believe some packs may use those indeed...

[redwire]

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

BMS boards are only a few dollars. Look at 4S 30A 14.8V li-ion battery BMS using S-8254AA protection IC. They have pack over-current and over-discharge, over-charge protection.

[stj]

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

i suspect this is the type of repair shop that would re-use the solder if they could.

[eccerr0r]

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

Alas, even having a BMS board that handles 30A, it doesn't help if the cells themselves can't handle 30A.

Incidentally, if people saw the few posts I made about one of my HTs that someone swapped 7 NiCd cells for 3 Li-ion with NO protection circuitry... surprisingly the radio still works...and I am still thinking about how to best add protection circuitry as currently there's no good way of charging the pack, either.

[Dannyx]

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

i suspect this is the type of repair shop that would re-use the solder if they could.

Correct...not so much the shop itself (it certainly could afford A LOT more - even a superficial glance at its budget tells me this !), but this particular chap who I suppose doesn't have the guts to ask the boss for better/new stuff so he makes due with what he has... Remember: used capacitors in clients' stuff - can't get over that ! >_>

Not sure how much a motor on one of those handheld vacs draws at startup TBH, though I remember a friend of mine had one whose batteries died and he tried hard-wiring it to a 5a power brick and it entered protection upon startup. The only way he was able to get it going was to use a PC power supply. I was thinking of designing an inrush current limiter for him to hopefully keep the load down at least until after the motor has spun up to keep the brick from turning off, but now that I think back, I think the RUN current itself was greater than 5a anyway, so it was no good. I'm surprised at how much current a small motor draws ! :|

[stj]

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

until a motor is moving, it's a dead short.
and it probably needs the current to start - so inrush limiting has to be done carefully.

[Dannyx]

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

I'm still keeping an eye on my colleague who is still working on this vac. Curious to see how it ends up Today he fiddled with it some more and the vac itself actually works, but doesn't charge, at least not properly: the LED on the dock is not coming on, though it does push some voltage into an otherwise low battery, for he tried draining the batteries with the vac itself and then charging it on the dock and it appeared to work...how well is debatable and could very well shorten the lifespan of the batteries...

I'm also laughing my ass off because this PERFECTLY reminded me of THIS episode from Dexter's laboratory - I won't spoil it for you, so feel free to watch

[stj]

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

so is the idiot still using lithiums in it?

[Dannyx]

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

'fraid so...he even cracked open another laptop pack to score himself some cells to try out Something's gonna pop in his face one day

[stj]

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

show him this!!!
https://www.youtube.com/watch?v=WdDi1haA71Q

[budm]

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

He will burn down the house while charging the batteries when he is not at home.

[eccerr0r]

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

I've charged my Kenwood's batteries overnight once by mistake... lucky lucky it didn't blow up as there's no protection circuitry...

[stj]

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

then add some - you get 10 for a $ now!!!

[Dannyx]

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

He will burn down the house while charging the batteries when he is not at home.

Worse, since it's not HIS vacuum

[eccerr0r]

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

then add some - you get 10 for a $ now!!!

But aren't people supposed to like living on the edge?

[stj]

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

not like that.

i was testing some used 18650's yesterday and charging them at 1Ah,
one got so hot i pulled it out and threw it into the garden!!!!

[Dannyx]

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

At least you have a garden

[sam_sam_sam]

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

That is why I charge and discharge these batteries before I use them

I have had some that just do not have the load capacity that they claim to be

I will not use them if they get warm when charging them at 2 amp or at 1 amp

If when discharging then a 2 amp and get warm or at 1 amp I will not use them

I use caution when using Chinese made batteries because either the quality of the cells or that the quality control is very poor ( meaning that no two cells are the same )

That video was some real serious shit

[sam_sam_sam]

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

not like that.

i was testing some used 18650's yesterday and charging them at 1Ah,
one got so hot i pulled it out and threw it into the garden!!!!

What brand of batteries were they