Keeping NiMHs in the fridge?

Discussion in 'General Electronics Chat' started by moeburn, Aug 18, 2013.

  1. moeburn

    Thread Starter Member

    Aug 16, 2013
    Okay, so I finally got myself ahold of some LSD NiMHs, and they certainly last longer than the others. But for the other NiMHs that I have, that were made before low self-discharge technology was common, can I keep them in the fridge to reduce their self discharge?

    Because I know from chemistry that pretty much any chemical reaction happens slower at lower temperatures. I also know that people have actually done the tests, and I think it was something like 25%/day self discharge at 21°c, vs 25%/month self discharge at 4°, for NiMHs. I've also actually been told by smart people that I should keep my NiMHs in the fridge between uses.

    But I've also heard tons of warnings, from other people, about keeping them in the fridge;

    • If you chill them too fast, and they were in humid air, said humid air will condense on the surface of the battery, and may short the terminals, and even if it doesn't, it may oxidize the metal surfaces.
    • If you chill them too fast, IE right after they finished charging and are still hot from the charger, and you put them in the fridge, the rapid dramatic change in temperature could physically bend/contract the metal, causing something to break internally
    • If you let them get too cold, the "whatever" stuff inside could freeze and form crystals, which is apparently really bad.

    I don't even know if any of the above is true or not, I just heard it from smart people, not scientists who had actually tested NiMHs in fridges. So half the people I've talked to have said "Yes, keep your NiMH in the fridge, not only will the charge hold longer, but the batteries will last longer too!", and the other half have said "No, don't do it! They might hold their charge a little longer, but you are at a very high risk of ruining the batteries!"

    So whats the general consensus on this? Is it a good idea to keep my rechargeables in the fridge? Or is it very risky? Are the above warnings completely unfounded, or are they very unlikely to happen, or are they really true and I should heed the warnings?

    Thanks for any input!
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    I never store rechargeables in the fridge since I can easily replace any charge lost by recharging them. I do store alkalines in the fridge.

    You can create condensation putting a warm battery in the fridge in a plastic bag.
  3. Metalmann

    Active Member

    Dec 8, 2012
    Used to do that for a year or so, but soon found out I was using them too often to bother.
  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
    I think that's high. I believe NI rechargables discharge more like 20 - 30%/month at room temperatures unless they are internally leaky.

    here is what Energizer claims for their NIMH:

    That may be a little optimistic...?
    Last edited: Aug 18, 2013
  5. Shagas

    Active Member

    May 13, 2013
    If you are worried about the batteries getting cool too fast then you can maybe wrap them in some insulating cloth which will slow the heat transfer.