Tips you may need to know to charge 12 volt lithium batteries
Lower your charging C rate
At low charging speed (C/2, C/5 or even less), the 12 volt batteries https://uk.renogy.com/12v-170a....h-lithium-iron-phosp are intercalating themselves smoothly in the graphite sheets, without damaging the electrodes.
When the charge rate increases, this intercalation gets harder and harder. If the rate is too strong, Lithium ions have no time to penetrate the electrode properly and just deposit on its surface, which causes the battery to age prematurely.
Fast charging rates like 4C or 10C are possible, for example for mobile or electric vehicles batteries, but the electrode constructions are different, and the expected lifespan is shorter.
Depending on how much time your application needs to be recharged and your use case, you’ll need to find the right trade-off between the necessary charging time and speed and the aging of the battery. A C/50 charging rate is better for the electrodes but not every application can afford more than 50 hours charging time! A 2C charging time (30m) is possible but will accelerate the aging of the battery.
Therefore, Saft recommends limiting the charge rate of its MP range to C or less.
Control the charging temperature
Most Li-Ion batteries use graphite type material in one electrode. An elevated charging temperature provokes the exfoliation of the graphite sheets which hastens permanent capacity loss in the battery. This phenomenon can be aggravated when associated to a high charging rate: the charging current increases the temperature and causes an acceleration of the exfoliation phenomenon.
A high voltage level coupled to a high temperature causes the electrochemistry to generate gases inside the cell which accelerates chemistry ageing. Depending on the cell construction, high temperatures can also generate cell swelling. Such a deformation can cause safety hazards when the battery casing or device location have not been designed to support it. Make sure not to exceed the limits set by the battery manufacturer, or —for example— put a cell on full charge for an extended amount of time in an overheated car in the height of summer!
If the battery design does not include the mandatory safeguards to avoid overcharge, over-discharge and over temperature, a cell internal temperature higher than 130°C could lead to a thermal runaway.
Most li-ion batteries can only withstand a maximum temperature of 60°C and are recommended to be charged at a maximum of 45°C under a C/2 charge rate, whereas Saft’s MP range can sustain a C charge rate up to 60°C and even C/5 up to +85°C for the xtd products thanks to its unique design.
Very few batteries can be charged below 0°C. The electrode sheets contract and the electrolyte electronic conductivity gets lower which complicates the intercalation of the ions in the graphite. Lithium deposit can be generated which cause permanent capacity loss. To compensate and allow for the ion to intercalate properly, some manufacturers recommend charging the battery at very slow rate (C/2 when operating below 0°C.
Saft’s MP range can handle charges at very cold temperatures —up to -30°C!— when applying C/8 and even C/5 rates.
