Damage possible from running Ni-MH to low?

[RyanRC]

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:ApplyBreakingRules/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--> Hello all

Kinda a newbee question I guess, but being from the R/C Helo world of which there is very few Ni-MH being used, I was just wondering what kind of damage you could do to a Ni-MH pack if you run it to low?

As mentioned, being into Helo's an with our world be almost all LiPo's, we certainly know the damage going lower then 20% can do, an that can be done pretty quickly by that.

But I think if I'm correct, going below that for Ni-MH is not as bad, but I don't know, and or even if is, how bad an if there is anything that can be done about that?

Anyway, sorry for such a newbee question posted here, but just looking to learn.

Thanks greatly for any help
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[Johnnysplits]

You can run nimh to zero...they have no memory. They do need to be cycled every other month if they're not used frequently.

 

[RyanRC]

Hey Johnnysplits, thanks for the reply.

Kinda thought so but didn't know for sure.

So for this cycling thing, is this just something you would know by output/time usage, or is there some other way to tell?

For me I will be using some pretty good (some might say one of the best) LiPo charges, the CellPro PowerLab 8: Revolectrix to charge the packs.

All in all don't know what there over all rep is for Ni-MH, but their LiPo capabilities are very highly regarded in the Helo world, an they can do Ni-MH an so am assuming they're pretty good for that too.

So just wondering, if I am getting up the full normal charge of a Ni-MH, could that be a good indicator I don't need to do a cycle?

Also one other question I was wondering, an this goes for anyone who cares to reply, but should I be doing any kind of 50% storage charge for the Ni-MH's, or anything other special for the winter storage time?

Thanks again for the help.

 

[Johnnysplits]

I've learned that if you let nimh's sit for long periods without using them, they die and won't take a charge, which is why I suggested cycling them like every other month. A good charger will cycle them automatically. Three cycles is enough. I haven't used nimh since '07. They just suck...period. I can't imagine why anyone would want to use them anymore.

 

[RyanRC]

I've learned that if you let nimh's sit for long periods without using them, they die and won't take a charge, which is why I suggested cycling them like every other month. A good charger will cycle them automatically. Three cycles is enough. I haven't used nimh since '07. They just suck...period. I can't imagine why anyone would want to use them anymore.

I would tend to agree only I don't know of them in the surface world an it seems many still use them for at least crawlers from my extremely limited experience.

For me I was looking right off for LiPo's, but for one, without a LVC unless the ESC has one (don't think this first truck has one), an no way to know its voltage, I worried about that. An two while I didn't mention it, this truck is going to be for my brother, who has Downs, who will not know to stop the truck if the pack it too low perhaps even with the buzzer. Basically I will be there all the time its used, but still, if I can't get to it quick enough, or the buzzer doesn't work right, an could get a LiPo pretty low. So at least with a Ni-MH, if that even happens, I haven't greatly reduced the life of the pack.

One other thing I was wondering about too, for me living in the NE, I def go through about 4 month if not more where it is just to cold to play with anything R/C. An from six years of R/C Helos, at least for me it seems the most damage any LiPo ever seems to get is when you store it for the winter.

I don't know, is supposed to not be that bad, but all I can say an even when I do all the right things such as 50% storage, is when I go to run the packs in the summer again, they just are not the same as when I put them away. So was kinda hoping to avoid that with the Ni-MH's as they seem to do better.

Anyway, thanks for all the info, has been a great help.

 

[Meatwad]

If you'll always be in the general area, a buzzer shouldn't be a problem. I've used the low voltage buzzers in the past before alot of cheap esc's had an lvc, they get annoying way before the voltage will become a problem for the lipo. In this day and age, nimh requires more upkeep and initial cost than lipo. Some balk about the dangerous chemistry, rightly so to a certain extent. Following a normal safety routine, as with anything else, will be enough to properly make use of the better battery chemistry.

 

[allanon1965]

why not just buy a cheap AE-5 esc? under 40 bucks on ebay and they have a lipo cutoff and are set with 2 simple jumpers...and its waterproof(resistant)...I run 3 of them for basher/trail running rigs with no issues...

 

[RyanRC]

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:ApplyBreakingRules/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--> I think one other thing to consider too though is, if the truck comes with a ESC that is only for Ni-MH, would have to replace that to go LiPo.

Basically am pretty aware that there are many low costs possibilities for this, but then too as the MaxStone8 I am going with has two motors, have to either make the choice of two or one an all the splicing.

But to get more on point, if I'm going to spend the money to get something new, would probably like to go with something better an so there goes the cost for that, plus all the work of the splicing if it is not made for two, an learning how to set it up. An then more packs.

I know its not really all that much what I'm talking about, but it is something an take money from the budget I would like to spend on other.

Kinda after is all put on paper in a plus ver minus thing, seems like staying with the Ni-MH is just less money an work.
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[RyanRC]

why not just buy a cheap AE-5 esc? under 40 bucks on ebay and they have a lipo cutoff and are set with 2 simple jumpers...and its waterproof(resistant)...I run 3 of them for basher/trail running rigs with no issues...

Is the AE-5 pretty programmable, or is it it just fixed or with few options/variables?

Can it be used with both brushed an brushless motors?

 

[Meatwad]

I think one other thing to consider too though is, if the truck comes with a ESC that is only for Ni-MH, would have to replace that to go Lipo...

Any esc works with any battery. But in the case of lipo, there must be a low voltage safety in place.

 

[Alexander_0_1]

Wait! How highly regarded are revolectrix lipos....I use them in my wraith, should I have bought more....

 

[RyanRC]

Any esc works with any battery. But in the case of lipo, there must be a low voltage safety in place.

Good point, that would make sense. DC electricity is DC electricity. Shouldn't matter the chemistry source. Most likely the ones I see where they say they can do both is as they have a setting where one gives you a LVC, the other doesn't so you can run it as low as you want.

Only thing I might add though is you might want to watch the capacity of the ESC if the motors could pull a lot.

Perhaps I'm wrong on this as I don't know all, an really haven't learned about the Ni-MH an what kind of C (amps) they could put out. But if your motors could pull it, an you got some high C LiPo's, would think you could smoke a ESC if it couldn't handle it.

Don't know, what dictates a Ni-MH's amp or C output (?), so far have not seen that info in any of packs I've looked at, or say seen it be something that could vary for the same other spec's like you see for LiPo's.

All in all I think (?) Ni-MH packs can't really do the high amp outputs an burst things a LiPo can, so if so, even if the motors could pull it, you wouldn't get the overload of the ESC. But could be entirely wrong on that.

 

[RyanRC]

Wait! How highly regarded are revolectrix lipos....I use them in my wraith, should I have bought more....

For me I couldn't say. For all my time, I have never seen them used, or talked about in the helo world.

Didn't even know they made them till you posted about em, but checked them out an seem like a good price for what they offer.

Company is known for many other good things, but doesn't guarantee obviously.

But if their working for you, I would say stick with them.

For sure might try out a pack or two myself.

 

[Meatwad]

Batteries don't "push" amperage, but rather the motor "pulls" amperage from the battery through the esc based upon trigger position. Having the highest c rating you can afford is always better. If the motor amperage exceeds the esc spec, there may be problems depending on application/gearing/etc. Correct on nimh not having the amperage output of lipo.

Then of course there's the stress from the internal bec, it's best to just get an external.

 

[RyanRC]

Batteries don't "push" amperage, but rather the motor "pulls" amperage from the battery through the esc based upon trigger position. Having the highest c rating you can afford is always better. If the motor amperage exceeds the esc spec, there may be problems depending on application/gearing/etc. Correct on nimh not having the amperage output of lipo.

Then of course there's the stress from the internal bec, it's best to just get an external.

Yeah, I completely agree an work with an have worked with enough of the related things we are speaking of to know just what you mean.

I know it would be lengthy to explain what I was meaning, but kinda think it really isn't that relative so no point in going into it.

At any rate, thanks much for all the help.

 

[Olle P]

I've learned that if you let nimh's sit for long periods without using them, they die and won't take a charge, which is why I suggested cycling them like every other month. ...

* A NiMH that gets a deep discharge will lose capacity.
* Usually a "dead" battery can be awoken by putting a high voltage on it until the charge current starts flowing. (Some capacity will have been lost though.)
* Charge full before storage, and then top it up every two or three months.
Running a full cycle each month will only eat capacity, but once a year or so is fine.
* Do NOT keep a NiMH on trickle charge over extended periods. That will also eat capacity way faster than you want.

Any esc works with any battery. But in the case of lipo, there must be a low voltage safety in place.

The word "must" is a little over rated. It depends on the use.
If normal use is to run until the battery is drained by only 30% or so there's no practical need for voltage warnings.

 

[z50king]

I remember when NiMH was new! People were afraid of it back then just like people are now of Lipo. If you bang a cell too hard the cap would fill with gas and explode off, often blowing a hole in your chassis.

It's hard to drain a cell to below 0.8 volts while driving. It will just stop moving around there. It's easy to drain a cell to 0.1 if you stick it on a light bulb and forget about it... I've done that before....

They are safe to bring back from deep discharges. I have found you need to set your controller on a lower voltage with high amperage and it will shock the thing into taking a charge while the controller won't freak out about the low voltage.

NiMH set the rc world on fire becuase you could charge them more than once a day. That's why people say they have no memory. They have no memory of that day's use like a NiCd battery did.

memories

 

[z50king]

Don't know, what dictates a Ni-MH's amp or C output (?), so far have not seen that info in any of packs I've looked at, or say seen it be something that could vary for the same other spec's like you see for LiPo's.

NiMH cells aren't C rated like lipos, they are rated in resistance of the individual cell. You can test the internal resistance of a cell and find what amperage it will put out and what the voltage will sag to. In the old days when we raced NiMH companies would test thousands of individual cells and group them by IR. They would create batteries packs with similar IR cells and sell them for more money with a lower IR. Those were the good old days of pack ratings you could rely on. Every cell in the pack would be labeled with the IR.