Lipo batteries for battery conversions?

JimmyB

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Lipos used in model aircraft tend to have thinner internal construction, as this allows for much higher discharge rates. Compare this to a mobile phone or laptop battery and the model R/C batteries are much less stable.

If you are using model r/c batteries in a railway model - even with quite low discharge, all the same safety information applies. I personally use lower discharge rate lipos designed for robotics and toys, as these are safer to charge in the model. I use a 5V usb charger for my 7.4V packs, as this has a very low charge rate - about 1 hour for a full charge.

To maintain good storage, charge batteries to only about 75% of full capacity and only fully recharge prior to a running session. This stops cell rot.

"Spicy Pillows" (You can safely google this!) are when a Lipo starts to expand due to failure of the cell structure. When they go like this, they can be quite dangerous, so need disposing of at a local tip or battery disposal point at a supermarket. You must first FULLY discharge the battery - I use a 12V 5W light bulb and immerse it in salt water for a about a week to neutralise the battery chemistry somewhat. Don't just dispose of a dead battery in the dustbin, as they can start fires. If this happens in the bin lorry, it can be quite exciting to watch, but on the whole is a bad thing...
My charger has variable charge rates, balance charging storage charging, and discharge options, also options for the various type of Lithium batteries and other rechargeables. My opinion is if you are using this type of technology (lithium) which has know hazards, then buying good quality ancillaries (charger) is important.
 

ge_rik

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I suppose it's down to personal preferences. I've been using lithium batteries in my locos since 2012 because most of my locos are quite small and the only way I could get the 12v (well 11.1v nominally) in the space available was to use lithium. Initially, I used lipo cells in pouches but I now use cylindrical 18650 or 14500 (AA size) cells made up into packs with battery protection boards.

All my locos are charged with their battery packs in situ. Like Jimmy B, I use a charger designed for lithium cells and only ever slow charge (at 0.5A).

In my my nine years of usage, I've only ever had one thermal runaway with a li-ion cell, and that was my fault. I accidentally shorted out an 18650 cell when soldering up a battery pack. The cell get very hot and vented gas but that was it. Interestingly, I've also had a short circuit with a pack of NiMh cells which melted the wiring loom and which could have caused a fire had it been in a loco body. All my packs (both li-ion and NiMh) now have polyswitches to protect against short circuits.

I recognise there are risks with any sort of rechargeable battery power and so try to take adequate precautions. The way I look at it is, the li-ion cells I use in most of my locos are identical or similar to those used in laptop computers, tablet computers and mobile phones and so will never leave any of these devices or my locos unattended when they are being charged.

Rik
 

JimmyB

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I suppose it's down to personal preferences. I've been using lithium batteries in my locos since 2012 because most of my locos are quite small and the only way I could get the 12v (well 11.1v nominally) in the space available was to use lithium. Initially, I used lipo cells in pouches but I now use cylindrical 18650 or 14500 (AA size) cells made up into packs with battery protection boards.
Rik, like you I started with LiPo, and still have couple, but with on-board protection and their construction, I am moving slowly to Li-Ion batteries which are in far more use in domestic appliances, often left plugged in and unattended, which gives me that warm fuzzy feeling about safety with their use.
 

ge_rik

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Rik, like you I started with LiPo, and still have couple, but with on-board protection and their construction, I am moving slowly to Li-Ion batteries which are in far more use in domestic appliances, often left plugged in and unattended, which gives me that warm fuzzy feeling about safety with their use.
I've still got one Lipo powered loco - the pack is now over ten years old and going strong. The other three have gone puffy. They are all sitting benignly in the bottom of a steel dustbin at the end of the garden. One of them has been there for around five years now and nothing untoward seems to have happened. One day I'll take them all to our local recycling centre.

Rik
 

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Rik, like you I started with LiPo, and still have couple, but with on-board protection and their construction, I am moving slowly to Li-Ion batteries which are in far more use in domestic appliances, often left plugged in and unattended, which gives me that warm fuzzy feeling about safety with their use.
Not wishing to burst your bubble, but Lithium Ion is simply the collective term for lithium batteries and pretty much all consumer lithium batteries will be lithium polymer.

I think what you mean is that you are going for metal encapsulated batteries with thick cell protection and higher internal resistance, so maximum discharge current is lower and hence, safer in the case of a short.

Lithium batteries should not be left plugged in all the time, but stored at 75% charge. This is why when you get a new phone or laptop, the battery has 40-80% charge out of the box. Also bear in mind that lithium batteries cannot be run dead flat, as they will not recover, so a cut off circuit to kill the power once the cells drop below 10% or so is a good idea in unattended locations like providing power to accessories where the battery could be left connected and switched on.

I use the same sort of packs on my trains for the same reason as you - they are safer to use and charge in situ.
 

JimmyB

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Lithium batteries should not be left plugged in all the time, but stored at 75% charge. This is why when you get a new phone or laptop, the battery has 40-80% charge out of the box. Also bear in mind that lithium batteries cannot be run dead flat, as they will not recover, so a cut off circuit to kill the power once the cells drop below 10% or so is a good idea in unattended locations like providing power to accessories where the battery could be left connected and switched on.
I don't disagree, but your toothbrush, flosser, vacuum, and many other cordless items, when not in use sit in their charger, which is plugged in, and when charged, is not unplugged in most cases.
So as I say I don't disagree, and my loco batteries are removed from the charger as soon after charging as possible, though my charger does stop charging when the cycle is complete, and requires a manual restart, so do not "trickle" charge after charging.
Stored at 75% of full charge, agreed, but what is storage, not running overnight, not running for a week, not running for a month, however is a battery "in storage" before it needs a storage charge. Normally after use I fully charge my batteries ready for next use, however batteries removed to "not in use" are then discharged to 75%.
 

ge_rik

British narrow gauge (esp. Southwold and W&LLR)
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Not wishing to burst your bubble, but Lithium Ion is simply the collective term for lithium batteries and pretty much all consumer lithium batteries will be lithium polymer.

I think what you mean is that you are going for metal encapsulated batteries with thick cell protection and higher internal resistance, so maximum discharge current is lower and hence, safer in the case of a short.

Lithium batteries should not be left plugged in all the time, but stored at 75% charge. This is why when you get a new phone or laptop, the battery has 40-80% charge out of the box. Also bear in mind that lithium batteries cannot be run dead flat, as they will not recover, so a cut off circuit to kill the power once the cells drop below 10% or so is a good idea in unattended locations like providing power to accessories where the battery could be left connected and switched on.

I use the same sort of packs on my trains for the same reason as you - they are safer to use and charge in situ.
I think most of us use "li-ion" to refer to the cylindrical cells and "lipo" to refer to those in floppy bags for convenience. I tend to use "lithium" as the catch-all. Not entirely accurate, I appreciate, but it sort of works in my mind.

The reason I use battery protection boards is to help prevent over-discharge. They cut off the power when the charge falls below roughly 3v per cell. In addition, the Deltang receivers I use include Low Voltage Cut-off - so I like to think I'm covered if one system fails.

I try to remember to balance charge my packs at least once a year but generally I find they have remained balanced anyway.

Rik
 

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I don't disagree, but your toothbrush, flosser, vacuum, and many other cordless items, when not in use sit in their charger, which is plugged in, and when charged, is not unplugged in most cases.
So as I say I don't disagree, and my loco batteries are removed from the charger as soon after charging as possible, though my charger does stop charging when the cycle is complete, and requires a manual restart, so do not "trickle" charge after charging.
Stored at 75% of full charge, agreed, but what is storage, not running overnight, not running for a week, not running for a month, however is a battery "in storage" before it needs a storage charge. Normally after use I fully charge my batteries ready for next use, however batteries removed to "not in use" are then discharged to 75%.
Anything with a Li-ion battery will have an intelligent charger, which will not float or maintain the battery as a lead acid or ni-mh charger might, but will cut off entirely once the battery has charged to about 95%. Some will perform discharge cycles if the battery has been at full charge for any length of time. In some cases, the technology is built into the battery, so the charger is just supplying power, that's all.

Anything over 24 hours at full charge will start to degrade batteries, so unless you intend to run the following day, it's better to just keep them at a storage charge.
 

Greg Elmassian

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Theoretically, per the manufacturer, ANY charging after the cell is at 100% starts to damage it. The big question is how accurately most systems measure 100%, the majority are conservative.

If you ever want your head spinning on lithium batteries, charging regimens etc, go to an electric car forum. Many new laws of physics are invented daily by "experts".

I realize that it's "safter" to remove a battery from a loco when charging, but as Jimmy B said, do you know anyone who disassembles their shavers, toothbrushes, laptops, cordless phones, cell phones when charging?

And as also already mentioned, we don't have the same high discharge needs as model airplanes, cordless tools, etc. Even laptop batteries get a harder workout with the new processors.

I really cannot see any reason people would not use lithiums, although I think using the more physically robust cylindricals is a better idea over the flexible pouches.

Greg
 

ge_rik

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I really cannot see any reason people would not use lithiums, although I think using the more physically robust cylindricals is a better idea over the flexible pouches.

Greg
I couldn't agree more, Greg. As long as suitable precautions are taken, they are just as safe as any other rechargeable.

Rik
 

GAP

G Scale Trains, HO Trains, 1:1 Sugar Cane trains
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Just to add to the discussion I have been looking at using LiFePO4 batteries when my NiMH batteries require replacement.
I have read that they are safer than Lipo and LI ion batteries hence my considering them.
As I am naturally, and by training, risk averse I always look at the worst case scenario when making my decisions.

A couple of examples of what I have read
"Safety: LiFePO4 is more chemically stable, and it is incombustible, which means that it is not prone to thermal runaway (and remains cool at room temperature). It can also withstand high temperatures without decomposing, and it is not flammable."

"Lithium-iron is a newer version in the lithium battery family, its anodes are also made up of carbon in batteries.
Phosphate based technology possesses superior thermal and chemical stability which provides better safety characteristics than those of Lithium-ion technology made with other cathode materials. Lithium phosphate cells are incombustible in the event of mishandling during charge or discharge, they are more stable under overcharge or short circuit conditions and they can withstand high temperatures without decomposing. When abuse does occur, the phosphate based cathode material will not burn and is not prone to thermal runaway. Phosphate chemistry also offers a longer cycle life."
 

Greg Elmassian

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They have been out for a while, but finally getting to reasonable prices. I believe I saw a demo where someone drove a nail through a pack with no thermal runaway.

Definitely a good idea, although I do believe the energy density is a bit less.

All going in a good direction. Also for our uses, I believe balancing charging is not necessary, due to the low current draw and low charging rates. We also usually do not discharge our packs to the degree the airplane guys do.

Greg
 

trammayo

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I just had a mail from Hobby King as I have recently bought some NiMh Batteries from them, for my money the notes below relate to Lipo Batteries but I though it worthwhile to post them for all‘s consumption as the notes come from a big supplier of LiPo’s. Whilst I would imagine many of the Don’ts apply to fast charging and extreme use with Cars and Planes they are interesting none the less. Meanwhile my 2 LiPo’s are still living in my old WW2 Ammunition case. It was the (my) Underlined Don't that has always worried me.

“So we just want to make sure that you are up-to-date on your knowledge of how to use batteries in a safe manner.

Here is a little reminder of the dos and don'ts when using batteries.
DosDon'ts
  • Always charge/store batteries in a non-conductive, fireproof container or bag, outside and away from combustible material.
  • Always use a compatible balanced mode charger, specifically designed for the chemistry of battery you are using.
  • Always set the charger for proper cell count and/or voltage listed on batteries’ labels.
  • Always set the charger to the amp charge rate as listed on battery labels.
  • Never alter, puncture or impact batteries or related components.
  • Never allow the terminals of the battery to make contact with conductive objects, such as metal.
  • Never store loose batteries together, the battery terminals may contact one another causing a short circuit.
  • Never expose Batteries to extreme temperatures or direct sunlight. The temperature range must be between 40-120° F (4-49° C).
  • Never charge batteries that are hot to the touch (above 100°F)
  • Never charge Batteries inside of the model.

Useful info (even if I don't use those batteries) - so I copied said info as a Word Doc!
 

JimmyB

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I believe balancing charging is not necessary, due to the low current draw and low charging rates. We also usually do not discharge our packs to the degree the airplane guys do.

Greg
Similar to Rik, I only balance charge occasionally, as it takes longer, I need to ensure I have "time to hang around" as they are not left totally unattended when charging. A small mitigation to the risk :)
 

Greg Elmassian

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Agreed, while the idea of balanced charging is clear, I find from my over 50 years of experience with cells in series:

1. properly maintained, I can get most quality packs to wear out before failing.
2. cheap packs often have one cell go shorted or open, but the rest of the cells are not far behind.
3. the worst experiences I have had was discharge to zero, and getting polarity reversal on a fully discharged cell, most of the time this has been nicads (I did say 50 years!)

To me, when a pack starts to wear, the run time reduction is noticeable, and usually the pack is ready for the bin.

Greg
 

GAP

G Scale Trains, HO Trains, 1:1 Sugar Cane trains
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They have been out for a while, but finally getting to reasonable prices. I believe I saw a demo where someone drove a nail through a pack with no thermal runaway.

Definitely a good idea, although I do believe the energy density is a bit less.

All going in a good direction. Also for our uses, I believe balancing charging is not necessary, due to the low current draw and low charging rates. We also usually do not discharge our packs to the degree the airplane guys do.

Greg
I always use balance charging but as I said earlier I am risk averse (working in aviation will do that to you) the LiFePO4 batteries are becoming vey popular with the grey nomads (caravan/Winnebago people) mainly because of the safety factor.

I had a brand new, read charged only once the put into storage with charge for 12 months, fail when I tried to balance charge it again. Out of warranty of course, but the other 2 purchased at the same time are still going strong after being treated the same way.
 

PhilP

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One thing I would say :

It is NOT a good idea to use button-top Lithium batteries in standard battery holders..
There will not be any protection electronics.
These holders (and the 'snap' connectors) are no-way near man-enough to cope with the current that Lithium batteries are capable of supplying.

Please also install a fuse (as close to the battery as possible) and choose a sensible value! - Just because it says '20A' on the cells, your little loco does not want that sort of current running through it, EVER!

PhilP
 

Paul M

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Just because it says '20A' on the cells, your little loco does not want that sort of current running through it, EVER!
Certainly not! Unless of course you're trying to use the poor thing to pull a 1:1 sized wagon