# Rechargeable Batteries--Initial Charge
**URL:** https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094
**Category:** Factual Questions
**Created:** [December 5, 2009, 2:05pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094 "2009-12-05T14:05:43Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@Hilary\_Algar](https://boards.straightdope.com/u/Hilary_Algar)
#### Post date: [December 5, 2009, 2:05pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/1 "2009-12-05T14:05:43Z")
Read somewhere that 24 hours or so is the optimal initial charge time to ensure maximum rechargeable battery life.
Is this a myth?
Would such a long initial charge damage the battery?
In one case, at about the 12 hour mark of an initial charge, the battery was knocked loose from the charger but replaced within a minute or so.
Would this accident have any measurable effect on battery life?
Your answers will be much appreciated.
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### Author:  [@chrisk](https://boards.straightdope.com/u/chrisk)
#### Post date: [December 5, 2009, 3:49pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/2 "2009-12-05T15:49:28Z")
I don’t know much about this subject, but I suspect that the answer is going to be very different depending on the actual chemistry of the rechargeable batteries involved - are they lithium-ion, (common in laptops and cell phones, for instance,) nickel-metal-hydride, nickel-cadmium, rechargeable alkaline, or something else??
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### Author:  [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)
#### Post date: [December 5, 2009, 4:08pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/3 "2009-12-05T16:08:19Z")
That’s what the instructions seem to always say, but I’ve never found it to be necessary. It’s not like batteries only work when they’re completely full, and you have to recharge every ten minutes.
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### Author:  [@Telemark](https://boards.straightdope.com/u/Telemark)
#### Post date: [December 5, 2009, 4:21pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/4 "2009-12-05T16:21:49Z")
It’s very different for different battery chemistry. For example, low discharge NiMH batteries are shipped fully charged.
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### Author:  [@CookingWithGas](https://boards.straightdope.com/u/CookingWithGas)
#### Post date: [December 5, 2009, 5:06pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/5 "2009-12-05T17:06:44Z")
I’ve never heard 24 hours, but generally instructions that I have seen tell you to fully charge the battery before first use. It usually takes 2-4 hours to fully charge. This is generally for cell phones and cameras, the devices that I replace the most frequently, and usually lithium-ion batteries IIRC. I can’t imagine any benefit to charging a battery past when the charger says it’s done, and certainly not to 24 hours. But as mentioned, I suppose this could be the best advice for _some_ battery types.
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### Author:  [@IAmNotSpartacus](https://boards.straightdope.com/u/IAmNotSpartacus)
#### Post date: [December 5, 2009, 6:09pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/6 "2009-12-05T18:09:25Z")
NiCD, hell yes, 12-14 hour initial charge.
NiMH, hell yes, 12-14 hour initial charge.
Li-Ion, no, just charge til it’s full.
SLA, topping charge if desired.
Cite: [http://www.batteryuniversity.com/partone-14A.htm](http://www.batteryuniversity.com/partone-14A.htm)
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### Author:  [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)
#### Post date: [December 5, 2009, 6:18pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/7 "2009-12-05T18:18:12Z")
If I may piggyback another question…
[This site says](http://www.batteryrefill.com/dvds/Tascam/Tascam_BP-D1.phtml):
> [@](#):
>
> Tascam BP-D1 Battery model is over 3 years old and Li-Ion Cells have a maximum 3 year shelf life. This means you are not getting 100% battery capacity even if it is new and sealed in the box.
Is this true? I’d like to have a battery so that I can learn how to use the deck (although I can use the a/c power supply, I’ll want to do some field tests), but I won’t actually ‘need’ audio until next Summer at the earliest. So if it’s true, there goes 1/6 of my shelf life.
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### Author:  [@IAmNotSpartacus](https://boards.straightdope.com/u/IAmNotSpartacus)
#### Post date: [December 5, 2009, 6:53pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/8 "2009-12-05T18:53:22Z")
Yes, Lithium Ion will degrade over time, especially if the voltage of the battery drops too far. You will almost certainly have a not insignificant number of bad cells.
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### Author:  [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)
#### Post date: [December 5, 2009, 7:01pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/9 "2009-12-05T19:01:39Z")
Another point to consider is the charger. Different chargers have different degrees of smarts.
I think the days of one-size-fits-all rules as the OP cites are long gone, particularly when looking for “optimum” results. The best answer is “It depends on the specific charger & battery.”
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### Author:  [@Superhal](https://boards.straightdope.com/u/Superhal)
#### Post date: [December 5, 2009, 8:39pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/10 "2009-12-05T20:39:54Z")
This is what I heard from a dealer (may not apply to your situation): In complex electronics, there’s a chip that regulates battery power. The chip is what tells your electronics to display “low battery,” “full battery,” or shut off your device. The “full discharge, full recharge” advice is to make sure the chip properly recognizes your battery, and doesn’t shut your device off when the battery is still half full.
In my experience, rechargable batteries have a certain number of uses before completely becoming useless. For laptops, for example, they are generally rated from 1000-2000 uses (3-5 years) before needing replacement, cell phones are probably less. Therefore, you can keep a battery forever if you never discharge it (which kind of defeats the point of having a battery at all, imho.) My wife’s laptop, for example, has been plugged in since the day it was opened, and the battery still reports the same usage time on battery for the past 6 years.
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### Author:  [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)
#### Post date: [December 5, 2009, 9:11pm UTC](https://boards.straightdope.com/t/rechargeable-batteries-initial-charge/520094/11 "2009-12-05T21:11:10Z")
> [@Superhal](#):
>
> Therefore, you can keep a battery forever if you never discharge it
No, lithium-ion batteries just die. A battery charged 100% and kept room-temperature will still lose 20% capacity per year. Actually, a 50%-charged battery does better, but lithium still has fundamental shortcomings. Ni-MH has advantages in that respect.