NIMH battery care

[Superluminal 3750]

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[Superluminal 3750]

Hello, 

Today was one of the first dry (albeit cold) weekends Ive been able to get out to run a car and I got about a minute out of what I thought was the fully charged battery before it died. Bit disapointing to say the least.

I dont get the chance to run my cars very often since changing jobs and now it may only be a couple of times a year at most. 

Im definitely not down with the lipo or brushless revolution so all my runners are nimh and brushed. I use the same batteries - 5000mah Enrichpower ones from Modelsport (got four or five) and a NX86 charger.

After this afternoons performance im thinking they might all be knackered now as i havent looked after them properly so will need check them. The one I used this afternoon was bought about two years ago, and may have been used once before or possibly never used - I charged it this morning which seemed to be very quick for the light to go green, maybe ten minutes? 

So, I have some questions if anyone can help (most of my search results have bee youtube results which i cant view)

When they are bought new is there anything you need to do with them first?

Should they be fully discharged after use, before charging again? 

Should they be recharged after short periods of running to top them up or fully discharge first before charging?

Do they need to be fully charged before storing again for long periods of time?

I dont have a smart charger just one with a dial on for different charge rates - all my batteries are the same 5000mah ones, should they always be charged at the 5.0a setting or should I use one of the lower rates?

Can nimh batteries be restored in anyway if they dont hold much charge?

Ive just ordered a lead to convert deans to tamiya which should allow me to use the smart charger i have for my RC plane.

Thanks!

[Twinfan 1253]

I'm no expert, but I don't think they should ever be fully discharged.  If they've sat for years unused they may have discharged below a recoverable point?

The fast charge you did was way too short for it to have been correct, so I'd try one on a trickle charge.  Set the charger at 0.5A or 1A and let it run for as long as it takes.  It may be 12 hours or more.  See how the battery is after that.

I trickle charge my batteries after use and only fast charge them as a top-up before using them.

[MadInventor 3884]

For me personally, I never fully discharge my nimH. They naturally lose voltage over time, so if you don't use them for a year they'll be at a low voltage anyway. I've got cells that are nearly 20 years old that still work, but if I don't use them for a long time they need repeated charge / discharge cycling to get the capacity back in them. You're not going to like me saying it but invest in a smart charger. You can at least see the ambient voltage of the battery packs and the capacity that goes in with each charge or discharge cycle. They are also great for revitalising packs as you can set them to do up to 5 discharge / charge cycles, which can bring the cells back to life, and you can't overcharge packs. 

To get the capacity in the packs back I would charge them at 2.5  to 5 amps and repeatedly charge and discharge them. Using a trickle charge won't hit the cells with enough current to bring them back to life. I have done this successfully with a smart charger but it should work with your peak charger. If you have a multi-meter you could set it to measure volts and connect it to the battery leads whilst you're charging them so you can see what's happening with the voltage. This will help you determine if the packs are toast or not. I've found 6 cell packs with voltages as low as 3 volts that I've been able to bring back to life, so don't give up on them too easily :).

 

[alvinlwh 5895]

As madinventor said, practically NiMH requires minimal maintenance and last for almost ever. Here is some datasheet from manufacturers and temperature is more important than anything else, and some mentioned a few cycles will be needed to bring a "dead" battery back to life.

https://www.pmbl.co.uk/blog/how-to-store-nimh-battery-packs

 

[Wooders28 4723]

6 hours ago, Superluminal said:

allow me to use the smart charger i have for my RC plane.

The modern LCD chargers, usually have a 'cycle charge' option. This charges them, then a controlled discharge, then charges etc and really wakes old cells up.

You should be able to set the charge rate, discharge rate (although the cheaper ones are usually only 1A discharge) and how many cycles. 

[SupraChrgd82 1425]

Give ‘em a chance. Cycle the batteries (charge>discharge>charge>discharge) a few times. I run exclusively NiMH as well and found that after a long period of sitting the capacity is very low.  After a few cycles they come back to life and capacity increases.

The general rule for charging is 1 ampere per 1000 mAh.  So a 5000 mAh battery should be charged at 5 amperes.  You’ll note that once charged it will be warm to touch, about the same temp as a comfortable cup of hot chocolate.

NiMH batteries are fantastic in the way that you can abuse them with charging/discharging/storage with little consequence.  

[Willy iine 18806]

I keep at least 50% charge at all times in my NiMh packs.  And only charge after allowing them to rest overnight.  

No other guideline.. I like simple.  Some of my NiMH packs are like 10 yrs old, still holds charge well. 

[Superluminal 3750]

Thanks chaps, i do have a Flysky smart charger with a discharge / charge cycle capacity but i dont have the right connectors for the Tamiya type plugs to put these batteries on it. Have ordered one off ebay - will probably be here in May.

 

[Wooders28 4723]

9 hours ago, SupraChrgd82 said:

NiMH batteries are fantastic in the way that you can abuse them with charging/discharging/storage with little consequence.  

Apart from exploding......

Only lipo /liHv that I've not had an issue with...yet 😬

Someone posted their nimh fire to so long ago, but mind one from a while back (didn't think it was a decade ago, but...🕰)