LifePO4 (LFE) batteries are great, but they are still batteries. Proper setup and use is critical to ensuring their longevity and performance. More importantly, without proper safety precautions LFE batteries have the potential to be extremely dangerous. Take safety seriously! You can and will hurt yourself if you don't. If you read nothing else on this site, read this.

Summary for Lifepo4 cells (tl;dr):

1. BE SAFE

2. Maximum/Minimum Voltage

   1. maximum voltage per cell: 3.65v, minimum voltage: 2.5v

   2. recommend maximum voltage per cell: 3.35, recommended minimum voltage: 3v

3. Maximum Charge/Discharge Rates

   1. maximum charge current: check data sheet, but often 1 C,

   2. maximum discharge current: check data sheet, but often 1 C

4. Temperature

   1. discharge temperature range: 32 F / 0 C to 110 F / 43 C

   2. charge temperature range: 4 F/-20 C up to 140 F/60 C

   3. optimal temperature range: 50 F/10 C and 70 F/21 C

5. Get a BMS

6. Orient your cells correctly (check manufacturer data sheet)

Basic Battery Safety: the primary danger of batteries their unintended, uncontrolled or unanticipated discharge. Basically, the greatest risk is that you will accidentally electrocute yourself or something else. Consequently the most important precautions you can make are to ensure conductive materials do come in contact with the terminals or anything connected to the terminals, like wires.

• This means you should first remove all jewelry like watches, wedding rings, bracelets, etc. Secondly, wear gloves and eye protection (large sparks can and will shoot molten metal into your eye). Terminals that are not being worked on should be covered with tape or some other nonconductive material. Once a terminal is set, for example all the necessary wires are attached to it, it should also be covered.

• Any tools that are used on the battery, like a wrench, ratchet or wire clippers should be non conductive or should be wrapped carefully in electrical tape so that every portion of the tool that can be covered is (it is OK to leave the working portions of the tool unwrapped if it would impair their function to do so).

• Before attaching any wires or connecting any battery cells, triple check your cells for the correct polarization. Make sure what you think is positive is positive and what you think is negative is negative. Accidentally short circuiting a battery is not pleasant.

• Read the data sheet for you battery or battery cells. Before you do anything with your cells get all information you can from the manufacturer, distributor or online concerning the cells. You can also typically find the data sheet for any cells online with a little searching. This will tell you all the important information you need to know to use your cells safely without damaging you or the cells.

• Finally, always keep your batteries secure. Do not keep your battery in the open where children, pets or just inquisitive friends could potentially touch it. Batteries are dangerous and leaving one out is a bad idea.

Maximum/Minimum Voltage: all batteries operate within a voltage range - which depends on the chemistry and is always listed in the datasheet of the battery. What that means is that when batteries are fully charged they reach a maximum voltage, and providing addition power to a battery can overcharge it, which will raise its voltage above its maximum voltage. This can permanently damage a battery, and potentially physically compromise it as well, for example causing it to explode, catch on fire, or leak. Do not overcharge your battery - once the voltage of the battery reaches its maximum it is critical that charging stop. The same is also true, but reversed, for the minimum voltage. When a battery is at its minimum voltage it is effectively out power, and continuing to drain the battery can damage it and potentially lead to leakage or physical damage. Once a battery is at its minimum voltage any discharge of the battery must cease and the battery should be charged. For LFE batteries, they should not stay at their maximum or minimum voltages for extended periods, as this can lead to damage - best practice is to leave a battery around 50% percent if it will not be used for an extended period, for example for more than a week. For LFE cells, individual cells should never be charged above 3.65v or discharged below 2.5v.

Maximum Charge/Discharge Rates: similarly to maximum/minimum voltage, all batteries will have appropriate rates of charge and discharge that will depend on the chemistry and should be confirmed in the data sheet. For the maximum charge rate, this mean that the battery can only be charged with power equal to or less than the maximum charge. For the maximum discharge rates, this means that the battery can discharged at a rate equal to or less than the maximum discharge rate. Sometimes these rates are the same, but just as often they are different - make sure to confirm with the manufacturer or the battery data sheet. Charging or discharging your battery at rates greater than its limits will damage the battery and could potentially lead to explosions, fire or other serious problem you most likely want to avoid. Charge and discharge rates are usually expressed in 'C', which is the capacity of the battery. For example, a 100 ah battery cell may have a maximum discharge rate of .5C, meaning the cell can only discharge up to 50 ah at a time. Also note that many batteries have surge charge and discharge rates - these are higher rates that batteries cells can sustain only for brief periods (e.g., 30 seconds, 5 minutes, or whatever is specified on the data sheet)

Temperature: batteries are just like you, they prefer certain temperatures, and just like you if they get too hot or too cold they can get permanently damaged. Check the data sheet of your cells to find out what the appropriate temperature ranges is for your cell. LFE the optimal temperature is between 50 F/10 C and 70 F/21 C - keeping your cells in this range will maximize their performance. But LFE cells can be used outside this range. Specifically, LFE cells can be safely discharged from 32 F / 0 C to 110 F / 43 C. Charging LFE cells once they are below freezing absolutely will damage the cell, while charging a cell when it is above 110 F/43 C is not as certain to hurt the cell as charging it below freezing, but is still not a good idea. For discharge, they can be safely discharged from 4 F/-20 C up to 140 F/60 C, although using the cell at the extreme ends of this temperature range is likely not good for the longevity of the cells. Any temperature needs for the cells should also be confirmed with the manufacturer or data sheet.

Importance of a BMS : a BMS is a Battery Management System. If you are going to build a battery out of individual cells then getting a BMS is absolutely critical. A good BMS protects your battery from all the things this pages describes, specifically it keeps your cells from having voltage go too low or too high, it prevents charge and discharge currents that are too great, and stop the cells from charging or discharging when the temperature is too high or too low. A quality BMS that is appropriate for the cells and battery it is being used with will essentially ensure the safety of that battery while also helping it to provide maximum performance. Moreover, most larger BMS now come with bluetooth, which provides tons of data on your battery and also allows you to customize parameters to suit your specific needs. While you can technically operate a battery without a BMS, it is a genuinely terrible idea. Please check out the BMS page to learn more.

Cell Orientation : this is the only part of this page (and maybe website) that may be controversial, but I would suggest keeping your prismatic cells upright. What does that mean? Well most battery cells come in two types - cylindrical and prismatic. Cylindrical cells (like 18650 cells), which look alot like AA batteries, can be oriented in your battery however you like. Prismatic cells (which are rectangular in shape) on the other hand should typically have their terminals pointed up, rather than on their side. Why? Well this is a complicated and controversial topic, but let me give my reasons here. There is no debate that having your prismatic cells with the terminals up is perfectly safe and standard use. There is some controversy though concerning putting them on their side, with some claiming this can cause them to leak or perform poorly and other defending the practice. Prismatic cells are rectangular, so they can be oriented on their side long ways down or short ways down, which some claiming that one way is permissible while the other is not. In my opinion, unless the data sheet explicitly permits specific alternative orientations, go with terminals up. We know that is safe and standard, and deviating from that without the explicit blessing of the manufacturer or distributor is a bad idea.