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gkatz

going LIPO - is it worth my time?

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12 hours ago, alvinlwh said:

Amazing how some will insist that lipos are safe as they had used it for years without any problems. It is like saying 1:1 cars or planes are safe as they never had a crash in one.

I had the personal (myself, not a mate's uncle's taxi driver) experience of a 3.7v 800mah lipo blew up before and it was quite a bang, will be far worse with a 7.4v 5000mah battery.

Also, there are some claim that lipos are safe as long as they are not abused and/or charged incorrectly. Well, I don't think the batteries on UPS Flight 6 were being charged or abused when they went up.

I am not anti lipo, I use lipo too but just wish people will at least acknowledge the risks rather than brushing them under the carpet.

I share this sentiment. A key point for me is that what we consider 'normal' use of these cells in RC models is probably considered to be abuse by the cell manufacturers. I believe this is a key reason not a single RC LiPo battery has the cell manufacturer named on the packaging.

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There are many different technologies of lithium batteries. Lipo, LipoHV, Li-ion, LiFePO4, IMR, INR, NCR are the ones I know of. Most will be familiar with the first couple.

IMR is the tech in the 18650s I use for my vaping as they are less likely to go crazy if I miss treat them slightly, only slightly though.
The Lipo we use for rc are likely the most volatile as we put them through some of the worst treatment in our cars, jumped and rattled, knocked and bumped, over-discharged sometimes etc.

The ones in phones are likely to be a different tech to them. Anyone remember the Samsung Galaxy Note 7 recall of the entire series? What a mess that was. 

And the hoverboard thing? 

And as @alvinlwh has experience of with his vape mod (and I’ve seen the aftermath of that in person) it can go wrong.

For the most part Lithium is safe and when it isn’t it’s really not. To each their own choice, or “Risk-assessment” and I respect that. If you’re anxious about it then store them with extra safety measures or avoid if you don’t want the hassle. It’s all down to everyones own want and need. 

I like my Lipos in my cars as the power is a big difference. 
 

One thing to remember is ANY battery, NiCd, NiMh, Lipo can go wrong

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@TwinfanFor me it helps to think of watt hours as energy capacity and amp hours as charge capacity. Thats how a NIMH at 7.2v 5000mAh has 24Wh of energy and a LiPO at 7.4v 5000mAh has 37Wh of energy.

Its definitely interesting looking up discharge curves of various battery chemistries across different rates. The story for NiMH is pretty bleak there compared to LiPO as well when you’re jamming on the go button. 

Discharge+capacity+Eneloop.JPG

On the original topic,  It doesn’t help with the low voltage cutoff in the car, but some manufacturers, like spektrum have smart circuitry in their batteries and chargers. The branded charger sets charging parameters per a chip in the battery. The battery keeps track of its health and automatically discharges to storage voltage after a set period. Seems like potentially a good system for someone who wants to run lipos but doesn’t want to watch internal resistance, balance currents, and such. 

https://www.spektrumrc.com/product/7.4v-6200mah-2s-120c-smart-g2-pro-basher-lipo-ic5/SPMXB2S62.html

 

 

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3 hours ago, Rasselbock said:

@TwinfanFor me it helps to think of watt hours as energy capacity and amp hours as charge capacity. Thats how a NIMH at 7.2v 5000mAh has 24Wh of energy and a LiPO at 7.4v 5000mAh has 37Wh of energy.

Its definitely interesting looking up discharge curves of various battery chemistries across different rates. The story for NiMH is pretty bleak there compared to LiPO as well when you’re jamming on the go button. 

Discharge+capacity+Eneloop.JPG

 

Thanks @Rasselbock, I did some reading around yesterday and it's the rate of discharge under heavy amp draw that I didn't know reduced the effective capacity of the battery.  Every day's a school day, eh?

What's the maths for "Thats how a NIMH at 7.2v 5000mAh has 24Wh of energy and a LiPO at 7.4v 5000mAh has 37Wh of energy."?  I thought Wh were volts*capacity so it would be 36Wh for the NiMH, not 24?

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11 hours ago, ad456 said:

If you’re anxious about it then store them with extra safety measures or avoid if you don’t want the hassle.

I'd like to bet, these are the type of people, that lipo would be absolutely fine, as they'd look after them! 

 

I was under the impression, that the different lithium chemistry, offered varied levels of discharge rates vs safety, with lipo (lithium polymer) being one of the most energy dense. 

 

battery_energy_density_graph_2

 

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@Wooders28 totally on point there on all counts, I was totally afraid of them and wound myself right up about it. Eventually educated myself properly(without the peer pressure to just jump in or the scare mongering of fires) and i use lipo bags to charge and a roller toolbox to store and a few years later I'm much more relaxed about it. I am guilty of charging/discharging without standing over them, albeit in a steel box in the shed. I'm so glad I did as it really is night and day over nimh. That said I still use nimh for a lot of my cars as some just don't really need the extra power for me, but for the models I felt that needed it suddenly they were sooooo much more fun!!

Yeah, various chems have different properties indeed. I understand of all LiFe is by far the safest but have much lower voltages.

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37 minutes ago, Wooders28 said:

 

battery_energy_density_graph_2

 

Now that's a graph. Lipo has around triple the energy density (Wh/kg) of NiMH then? Wow. I hadn't realised the difference was that much. 

I wonder is this useable Wh, measured as the energy difference between full and safe low voltage cutoff (vs some defined point you stop with a NiMH because it's slowed down)? Or all the energy stored including that which would take voltage down to zero if used? 

For me, the runtime and performance advantages of LiPo are big enough that I use it, even though I'm not racing, just having fun, but I certainly wouldn't belittle the safety concerns, whether I've experienced failure personally or not (I haven't, but I don't ever want to).

On that note, I am tempted to buy a couple of steel boxes (ammo boxes I read are a good option? Love a trip to the army surplus store - it's a treasure trove) for storage in place of (or as well as) my lipo bag which I'm not entirely convinced by. And as @ad456 also then to charge/store in the shed, albeit mine too would be unattended but the penalty for failure much less. Honestly, I'd be lying if I said I always stay in the room while they charge anyway. If you do, what will you see that then triggers what action to prevent fire?

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This reminds me, I don't think this has been posted on this thread but when I asked similar questions a year or so ago I was pointed this way. 

It is quite a long read but it's an easy read and gives a really useful education on the subject. Well worth it IMO. In fact I should probably refresh my memory with it. 

https://www.rogershobbycenter.com/lipoguide/

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Re. the last graph, I think it's showing that for the same capacity rating (e.g. 5000mAh) LiPOs are lighter (weight, on the y-axis) and smaller (volume, on the x-axis) than NiMH batteries.  I don't think it's saying they contain three times the energy!

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1 hour ago, Twinfan said:

I don't think it's saying they contain three times the energy!

Triple the energy density,  which is measured in,  Watt hours per kilogram. 

Could translate that, to mean that Nimh are just three times as heavy? 

 

1 hour ago, BuggyDad said:

ammo boxes I read are a good option?

Aye, But remove the lid seal. Having them sealed, kind of ,turns them into a bomb, as the smoke can't escape, and the pressure builds.

I've a mixture of ammo boxes, and a batsafe, but all are stored in their own lipo bag too.

The Batsafe are meant to filter the smoke, although, I'm still betting it'll still stink 🦨

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18 minutes ago, Wooders28 said:

Triple the energy density,  which is measured in,  Watt hours per kilogram. 

Could translate that, to mean that Nimh are just three times as heavy? 

You could, but as I said on page 1:  "Some Googling says a 5000mAh NiMH is ~400g vs a 5000mAh LiPo at ~250g.  So a 150g saving."  Which makes them 50% heavier, not 300%, when put into an RC-ready pack.

I guess the packaging comes with weight, and LiPOs will need to have fairly solid casings for safety purposes?

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On 1/25/2023 at 1:30 PM, alvinlwh said:

Amazing how some will insist that lipos are safe as they had used it for years without any problems. It is like saying 1:1 cars or planes are safe as they never had a crash in one.

I had the personal (myself, not a mate's uncle's taxi driver) experience of a 3.7v 800mah lipo blew up before and it was quite a bang, will be far worse with a 7.4v 5000mah battery.

Also, there are some claim that lipos are safe as long as they are not abused and/or charged incorrectly. Well, I don't think the batteries on UPS Flight 6 were being charged or abused when they went up.

I am not anti lipo, I use lipo too but just wish people will at least acknowledge the risks rather than brushing them under the carpet.

There's always a risk even with NiCd & NiMh when mishandled. You can't brush that fact under the carpet too. I have seen many NiCd/NiMh burned, harmed people and burned RC cars in flames just because of simple battery shortage due to small pieces of metal laying/flying on the tracks or mishandling. So there's always a risk and owners/handlers should be responsible enough to take extra care when using, charging, storing and transporting batteries regardless of what kind.

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Going back to the original title question...

Yes it's worth switching to Lipo (for me and for thousands of other people). Why? I have used NiCd & NiMh since the 80s to the early 2000s. And LiPos are so much easier to work with. Longer running time, double or triple as compared to the NiCd/NiMh, lighter (as mentioned many times) easier to maintain and cheaper. Also LiPo chargers are much nicer, cheaper and have more options. Some Lipo chargers can charge two to four batts at the same time. I remember back in the day when we raced, we had to have several chargers, ate least 6 NiCd/NiMh batteries minumum, several battery dischargers, and several battery conditioners. Plus the amount of heat that builds up every single charge. Now with LiPos, none of those have to be present.

This

jcE6rAG.jpg

vs this

17fc1fc9-4692-422a-9916-ca735e9ca4d8.jpg

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On 1/15/2023 at 9:06 AM, gkatz said:

Hi all;

for someone who is the occasional driver, is it worth moving to LIPO?

it seems like its a hassle charging and discharging, low voltage cutoffs (i am suprt confused).

I am used to NiMH where I dont really care about this stuff. are this disclaimers for real? i mean, I dont want to work for the battery i want the battery to work for me :)

it would be nice to bump us the run time of the car though...

thanks in advance :)

My experience -  
Most non-competition Tamiya kits are sprung for NiMH or LiFe packs.  Lightweight LiPo leave the car feeling stiff and prone to loose handling on packed dirt or asphalt.  
In crawlers, the heavy NiMH packs add needed weight and forward weight bias. They are big and restrict me from using forward motor trannys, but it’s not a detriment to my rigs.

I occasionally drive a makeshift parking lot track with friends.  They run LiPo (5000 mah) and I run NiMH (3000 mah).  They hit low voltage cut off within minutes of my battery being completely drained.  My car is not “punchy” at all, but  being smooth and steady suits my driving style.  My friend’s cars are punchy enough to break traction at will.

I leave all 22 on my NiMH packs stored with a full charge.  I can drive any RC at will with zero time needed to plan, prep, charge or store batteries. Minimal safety precautions are needed in charging areas, and zero regard is given to battery voltage at any stage of use.

I’m obviously a proponent of NiMH…

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6 hours ago, Nicadraus said:

There's always a risk even with NiCd & NiMh when mishandled. You can't brush that fact under the carpet too. I have seen many NiCd/NiMh burned, harmed people and burned RC cars in flames just because of simple battery shortage due to small pieces of metal laying/flying on the tracks or mishandling. So there's always a risk and owners/handlers should be responsible enough to take extra care when using, charging, storing and transporting batteries regardless of what kind.

I am not trying to brush anything under the carpet. I say again, I am pretty sure that the lithium batteries on UPS6 were not being charged, raced or otherwise abused or mishandled when they autoignited. I don't know, maybe it was a scrap piece of metal on the runway like AF4590 that caused the fire. And when they do go up, they require specialist extinguishers to put out rather than the more common ABC type. Also, lithium of any kind are subjected to serious amount of shipping restrictions and regulations while NiMHs are not. If they are not that dangerous, why?

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2 hours ago, alvinlwh said:

Also, lithium of any kind are subjected to serious amount of shipping restrictions and regulations while NiMHs are not. If they are not that dangerous, why?

Like I said, there's always a risk. As I mentioned, NiMh battteries builds heat faster during charging and while in usage than can cause the batteries burst or leak too. So different types of danger lies within when improperly used or mishandled. Again, regardless of the battery.

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I think many others have covered all essential points.

A bit off topic but I'm afraid it's going to be an inreversable trend of technological improvement.

Look at our cell phones or other mobile devices and they are all using Lipo batteries.

No offense but it's just like NiMh replacing NiCd two decades back.

I bet we won't be able to buy NiMh batteries in a few years. Just no manufacturer will be making them.

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11 hours ago, Twinfan said:

Which makes them 50% heavier, not 300%

Must be the combination of more watts and lighter.

 

11 hours ago, Twinfan said:

LiPOs will need to have fairly solid casings for safety purposes?

Naa, not really.

This is a 2s shorty I accidently shorted out (reverse plugged in, rushing to get to the line for a final), which dropped down to one cell (safety feature?) 

Had to split it open, and use Croc clips on the circuit board, and a car headlight bulb, to safety drop it to zero volts for disposal.

Thought the hard case would be thicker, but they're fit for purpose.

2019-11-26_10-14-26

 

Soft case lipos, are just the lipo pouches, wrapped in shrink wrap. They're okay for in enclosed chassis, but not that great for the likes of the boomerang, with the battery hanging out of the sides.

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9 hours ago, Nicadraus said:

I have seen many NiCd/NiMh burned

Only battery chemistry, I've personally had go up (so far....😬).

We used to fast charge those, until they where hot to touch.

 

9 hours ago, Nicadraus said:

vs this

I've not long got the same charger, great charger, and quite like the Bluetooth function, as I can check on the charging out in the garage, from the kitchen , but that'll charge/discharge nicad / Nimh too anyway? 

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18 minutes ago, Wooders28 said:

Only battery chemistry, I've personally had go up (so far....😬).

We used to fast charge those, until they where hot to touch.

 

I've not long got the same charger, great charger, and quite like the Bluetooth function, as I can check on the charging out in the garage, from the kitchen , but that'll charge/discharge nicad / Nimh too anyway? 

Yes. LiPo/LiHv/LiFe/LiIon/NiMh/NiCd/Pb. Works with most RC batteries if not all.

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4 hours ago, Fabia130vRS said:

In 2023 if you are still using nimh. You are missing out big.

 

 

Nah. NiMH is good solid safe fun. No Lipo necessary :D

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Totally agree.  I don't need quicker than I can get just as easily with faster motors. or the extra hassle  :D

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I was at the track with my little TT-02 spec racer. I've 2 2S 7.4v 6000mah lipos and one 3800mah NiMH that I had in my bag that I'd never used.

I could go for 15-20 minutes constantly on the lipo's without noticing any difference, only pulling in to let my tyres and motor cool. I threw the NiMH in to see how it went, first lap or two was fine then each lap after that I noticed I was having to turn and brake in different places and the car was notibly getting slower and less responsive (in power and steering) as the laps went on. For me, lipo's give the consistancy needed to progress as a driver and not have to relearn the car/track as the laps go by.

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