Lithiums are also affected by heat and cold, just much less so than alkalines. Investing in a 12V car plug adaptor for your Eneloop battery charger is a good idea. And of course a ZTS Battery Tester is essential. It tests batteries under load so the readings are far more accurate. I have both the mini-ZTS and the MBT-1, the difference being the MBT-1 can also test NiMH, Lithium AA, coin cells, etc.