LiPo vs NiMh

[100SRV]

Hi,
I've got an Axial Bomber which only gets used occasionally. I think the NiMh battery is close to end of life and was wondering whether I'd be better off changing to LiPo.

How do the two chemistries compare up for infrequent use?

Will stay with 2S so the speed controller should survive OK.

[aliperry]

I'd say stick to a decent NIMH battery.
Lipos need to ideally be storage charged and should never be stored fully charged. There's also the potential of fire risk with lipos. I keep mine in a lipo bag in an ammo tin! But I'm just paranoid!

[The_Jackal]

Just for occasional use its not worth it as you will need a proper balance charger as well (they must be balanced).
They are better with more power and last longer but Nimh isnt the end of the world.
You cant run them to empty, need to be balanced and dont leave them at full charge.
Yeah there are horror stories but they arent always like that, they just need to be treated with respect.
Once you start with Lipos you tend to use them on several RCs.
At the very least they should be left in a fireproof box or bag and NEVER leave them alone (or near flammable stuff) when they are charging.

[Simpo Two]

aliperry said:

I'd say stick to a decent NIMH battery.
Lipos need to ideally be storage charged and should never be stored fully charged. There's also the potential of fire risk with lipos. I keep mine in a lipo bag in an ammo tin! But I'm just paranoid!

Hmm, I took the LiPo battery out of my MTB and charged it before storing it over a year ago.

Is it screwed, and if not, what can I do to make it 'storage charged' short of putting back in the boat and running it dry for X minutes?

[aliperry]

Simpo Two said:

Hmm, I took the LiPo battery out of my MTB and charged it before storing it over a year ago.

Is it screwed, and if not, what can I do to make it 'storage charged' short of putting back in the boat and running it dry for X minutes?

A lipo storage charge is essentially getting all of the cells to between 3.7v and 3.8v. Most lipo chargers offer a storage charge function which basically gets all cells to 3.8v.
If they drop below 3v per cell the lipo is normally no good then but some people do revive them by sticking them on a NiMH charge, but it's risky..!!
Might be worth buying a voltage checker and you might be in luck if the cells aren't too low. ??

[Simpo Two]

aliperry said:

A lipo storage charge is essentially getting all of the cells to between 3.7v and 3.8v. Most lipo chargers offer a storage charge function which basically gets all cells to 3.8v.
If they drop below 3v per cell the lipo is normally no good then but some people do revive them by sticking them on a NiMH charge, but it's risky..!!
Might be worth buying a voltage checker and you might be in luck if the cells aren't too low. ??

Thanks. I have this https://wheelspinmodels.co.uk/i/261735/?gclid=EAIa... which is 7.2V and the voltage is currently showing 7.7.

The charger is simple, one of these https://www.hobbies.co.uk/model-boats/radio-contro... so there's no 'storage' option. But the battery seems quite happy... with time it would drop to 3.8V anyway so would then be OK, I presume?

[aliperry]

Simpo Two said:

Thanks. I have this https://wheelspinmodels.co.uk/i/261735/?gclid=EAIa... which is 7.2V and the voltage is currently showing 7.7.

The charger is simple, one of these https://www.hobbies.co.uk/model-boats/radio-contro... so there's no 'storage' option. But the battery seems quite happy... with time it would drop to 3.8V anyway so would then be OK, I presume?

Ah, that's an NiMH battery, not a lipo battery. You can run NiMH right down to empty. As long at its holding a charge it should be all good. 👍

[The_Jackal]

Simpo Two said:

Thanks. I have this https://wheelspinmodels.co.uk/i/261735/?gclid=EAIa... which is 7.2V and the voltage is currently showing 7.7.

The charger is simple, one of these https://www.hobbies.co.uk/model-boats/radio-contro... so there's no 'storage' option. But the battery seems quite happy... with time it would drop to 3.8V anyway so would then be OK, I presume?

That is just a conventional Radio Control NiMh battery. You dont need to worry about that type.
Lipo rely on a much more volatile chemical reaction, that is why they have certain safety considerations but generally higher consistent levels of power.
LIPOs in the RC hobby though are a much more mature product than they used to be, but because a Lipo fire is difficult to put out basic safety rules should be stuck to.

[Simpo Two]

aliperry said:

Ah, that's an NiMH battery, not a lipo battery. You can run NiMH right down to empty. As long at its holding a charge it should be all good. ??

DOH! Stupid me. Because I only bought it in 2019 I just assumed it would be the latest chemistry. It's what the chap in the shop recommended. I guess Li-Po is lighter but because it's for a boat not an aeroplane/drone, weight doesn't matter. Panic over, carry on

[100SRV]

Thank you all for the replies!
Decision made - stick with NiMh.

Edited by 100SRV on Thursday 11th March 09:18

[Simpo Two]

General question - why are lithium batteries everywhere else 'lithium ion', but in the model world they are 'lithium polymer'? Is it energy density?

[shedweller]

Simpo Two said:

General question - why are lithium batteries everywhere else 'lithium ion', but in the model world they are 'lithium polymer'? Is it energy density?

Lipo can generally supply much more current than li-on batteries but not as energy dense? lipo is a lighter battery but more unstable with a reduced cycle life over lithium ion. I am sure there are many other differences.....

Li-s and solid state graphite batteries are starting to appear in the hobby but only at a battery enthusiast level........the RC hobby market was using lithium batteries well before consumer market and often battery advances were seen at a hobby level early in the game..... EVs have changed that...
When I started using lipos they could be properly dangerous things to be around..... No way you would you have one in your pocket!

[Simpo Two]

shedweller said:

Lipo can generally supply much more current than li-on batteries but not as energy dense

Interesting, thanks.