# Time for a new battery pack?



## HaBi Farm (Aug 28, 2011)

How do you know when it's time for a new battery pack. Obviously when it is totally dead, but . . . 

I have Ni-MH batteries of an undetermined age (I bought the setup used a couple of years ago). They will take a charge, but after sitting for only a few minutes will need 5 minutes or so to fully charge again. When used on my layout, for the first minute or so they seem to have plenty of zip. However, then there is a noticeable drop in speed and after a few more minutes the loco stalls out on the end of the layout with a 6' diameter 180 degree turn, even though it continues to do OK (not great, just OK) on the rest of the layout. There continues to be a gradual slow down, with it needing more and more of a hand boost to get around the 6' diameter end.

These batteries have not been used very often, maybe 3 or 4 times a year. I know that using them more often, with recharging, would have helped extend their life. But as of now, do I need to bite the bullet and get new ones. And if I do, what is the best way to keep them alive, given my infrequent run times. I'd prefer to stay with Ni-MH.


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## eheading (Jan 5, 2008)

The first thing I would do is when the engine starts to bog down and need help, measure the voltage that the batteries are putting out and see if they are significantly discharged (I suspect the answer will be "yes"). If they are, then you probably need to replace the batteries. There was a time when I used a lot of ni-mh batteries, but I found that when sitting unused, they self discharge quite a bit. I have now gone to all li-ion batteries. They cost more, but they just perform so well. You get more power per cubic inch of battery, and they self discharge much less than the ni-mh batteries do. I was away traveling this summer for over 3 months, and when I got home, I started running my engines without recharging the batteries and they ran just fine. Quite a difference from my personal experience with the ni-mh batteries.

Ed


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## Greg Elmassian (Jan 3, 2008)

They have failed. Sounds like internal shorts that limit the charge capacity (dendrites usually) No question given your description. 

Get the Sanyo Eneloop batteries if you can... you are not using them often enough, or charge them periodically with a smart charger. 

Lithium batteries also have a good shelf life. 

Greg


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## HaBi Farm (Aug 28, 2011)

The Sanyo Eneloop batteries look promising and I see that there are several mail order places to get them plus possibly a "real store" about 40 miles from where I live. But it also looks like I'd have to bundle/wire 12 of them together to get 14.4 volts (with 2,000 MaH) plus the connections to the ESC. Since my hands on electronic skills are minimal, I will likely pass on them in favor of an "off the shelf" already put together battery pack that is ready to plug & play. I do have a smart charger and have been told that if I run a Ni-MH battery pack about every 2 months then top off the charge that I should be able to get along OK with a regular Ni-MH set up.


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## Greg Elmassian (Jan 3, 2008)

I'd seriously consider a li-ion pack for as often as you use it. Just topping off the charge really does not help as much as exercising them on a more regular basis. 

Regards, Greg


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## Michael Glavin (Jan 2, 2009)

Take a look at the link below for 14.4V NiMH battery at a reasonable price... The NiMH batteries work as well as others and they do suffer from higher self discharge curves than other chemistries, but they are inexpensive, deliver lots more current and have at least the same three year lifespan as Li-Ion cells. I'd consider cycling them at least every two months.

Several years ago they introduced LSD or Hybrid NiMH batteries; these offer "low-self-discharge” numbers and have nearly the same high “energy density” numbers of Lithium. These cells claim 85% capacity after 12 months, almost as good as Li-Ion. 

14.4V 3800mAh battery, $23.99 USD

LSD NiMH cells

Michael


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## Greg Elmassian (Jan 3, 2008)

Don't know about you, but don't want LSD with or without batteries ha ha! 

Funny they don't connect that abbreviation and pick something else. 

I suspect the Tenergy LSD is same as Eneloop technology. 

Greg


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## SD90WLMT (Feb 16, 2010)

do Li-ion cells only have a three year life time? 

Dirk


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## Greg Elmassian (Jan 3, 2008)

Or less... 

worst of all chemistries.. 

Greg


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## Michael Glavin (Jan 2, 2009)

Posted By SD90WLMT on 01 Oct 2012 01:03 PM 
do Li-ion cells only have a three year life time? 

Dirk 
I've seen some last longer than others, but three years or so is what I have experienced with numerous Li-Ion batteries. 
Lithium batteries start to degrade as soon as the matrix is combined, there is no maybe in this regard. In my experience a three year life cycle is very common with Lithium Ion cells. One must consider how long have the cells actually been on the shelf prior to purchase, are they really fresh when the end user receives them??? And after the first year, Li-Ion cell capacity starts falling off the chart notably[/b] and continues to degrade as they age and are utilized. The cost to own/operate the high energy density battery chemistries is significant IMO. 
Michael


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## SD90WLMT (Feb 16, 2010)

OK - more reason for me to stick with the basic lead-acid I have been using for years, and are so much lower in price! 

I had no idea regarding this in this latest battery design.. 

thanks - Dirk


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## Greg Elmassian (Jan 3, 2008)

Always remember you never get something for nothing... you get high current density and light weight from lithium-based batteries.... you also get less charge/discharge cycles, sensitivity to overcharge, and more cost. 

For our new cool electronics, space and weight is at a premium, and the business of selling replacement batteries is lucrative. 

Greg


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## TonyWalsham (Jan 2, 2008)

The longest lasting of non lead acid batteries are without doubt NiCd. 
Sanyo used to quote 1,000 recharge cycles for the SubC size. Twice what they claim for NiMh. 
NiCd has a lower self discharge rate than NiMh and can be left on 1/10th trickle charge when not in use. Something you cannot do with NiMh. 
You can place NiCd cells (as in packs of the same nominal voltage and capacity) in parallel to increase capacity (longer run times) but they *MUST* be protected with suitable diodes to prevent packs bleeding into one another. 
Each bank of batteries must be charged separately. 

A word on ENELOOP AA NiMh - Alkaline cells. They are not designed for sustained current draw much above 1/2 amp. They were designed for digital cameras to prevent self discharge. Sure they will give whatever current you want to draw, but above 1/2 amp you *WILL* shorten their life span. 

Lead acid. Normal lower cost Gel Cells drop their voltage as they discharge. You will need to use the much more expensive deep discharge variety if you want to avoid voltage drop.


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## SD90WLMT (Feb 16, 2010)

I'm using the ''Power Sonic'' version of a lead - acid.. 

They are also great for ballast and traction increases.....3 - 6 volts - 4.5 Amp Hr, in a double set gives 9.0 Amp Hr. and 18 volts, with diodes to prevent equalizing , running on 7.5 amp mini fuses per pack! 

Never stop out of the blue or under load, never have lost a fuse once I got the set-up dialed in!! about $8.00 per battery ...and run easily half a day. And with a few hours recharge time on a smart charger! say over lunch... 

Dirk


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