LiFePO4 Battery Installation Guide

The Do's & Dont's & a Few Layouts

Solar Power Systems_
Van-Electrical-System

Please Remember that it is a legal requirement that LiFePO4 Batteries are shipped at 50% SOC and therefore will need to be charged before use.

For the Tech's, The IR will be around 5 mΩ. all other info please check the specsheets for the model of battery you need.

Things to consider:-

1/.where are the batteries to be located?

2/. Is it ventilated?

3/. One battery compartment or Two?

4/. On one side or Both Sides

5/. How much power storage do i need?

6/. How much charging system do I need?

7/. Whats the battery Layout? End on End or Side by Side

My Tip:-

If you need to run cable always go One Gauge bigger than required and do not save on the connectors, you'll thank me when the weather turns bad.....or you need the max from your system......

N.B Nothing worse than feeling those cables  & connectors getting HOT!!!

12V 100AH
12V 200AH
48V 100AH
48V 100AH
24V 100AH3
24V 200AH
24V 400AH
Fuel Gauge

Charging LiFePO4 Batteries with Solar Charge Controllers
Most standard solar charge controllers can effectively charge lithium-ion batteries, such as LiFePO4 (Lithium Iron Phosphate) batteries, because the required voltages are similar to those for AGM (Absorbent Glass Mat) batteries.

Battery Management System (BMS) in LiFePO4 batteries ensures that the cells receive the correct voltage, preventing overcharging or over-discharging, balancing the cells, and maintaining cell temperature within the safety limits during charging.

When building your system dont be tempted to mix & match aways use the batteries of the same make and size and where possible the same manufacturing batch so as to be sure that the BMS's are all the same model.

Efficiency: LiFePO4 batteries are more efficient than lead-acid batteries, meaning they require less energy to recharge after discharge. They also have a flat voltage curve, the charge voltage does not change much with different charge rates.
Float Voltage: Unlike lead-acid batteries, LiFePO4 batteries do not require a float charge They are either charging or not. If the charge controller cannot disable the float charge, set it to a low voltage (13.6V or less) to prevent actual charging.
Charging Profile of LiFePO4 Batteries
LiFePO4 batteries have a  charging profile that is very easy to follow. The following points explain the process.
Charge Voltage:                                                                                                                                                                                                The charging voltage for a 12.8V LiFePO4 battery is taken from the cell voltage. A single cell voltage is multiplied by four to get the approximate battery voltage. For example, a single cell charge voltage is  3.2V so for a 12.8V system, it would be about 13.6V to 14.4V esh.
Charging Stages:LiFePO4 there are two main stages:
Constant Current Stage (CC): The battery is charged with a constant current until the voltage reaches the absorption level, of around 14.4V for a 12.8V battery. During this stage, the voltage gradually increases.
Constant Voltage Stage: Once the absorption voltage is reached, the voltage is held constant, and the current gradually decreases. The battery is considered fully charged when the current drops to about 5% to 10% of the battery’s amp-hour (Ah) rating.
Equalization: LiFePO4 batteries do not require equalization. If the charge controller has an equalization setting that cannot be disabled, set it to 14.6V or less so it functions as a normal absorption charge cycle.
High Voltage Protection: The BMS typically allows a maximum voltage of 14.8V to 15.0V before disconnecting the battery to prevent overcharging. There is no benefit to charging at higher voltages and doing so increases the risk of triggering the BMS protection and potential damage.
While LiFePO4 batteries are generally easier to manage and charge than lead-acid batteries, understanding their charging requirements and the role of the BMS is crucial for maintaining LFP battery health and longevity. Properly configuring the solar charge controller to align with these requirements ensures optimal performance and safety.
Absorption time:
There is a lot to be said for just setting the absorption voltage to 14.4V or 14.6V, and then stop charging once the battery reaches that voltage! In short, zero (or short) absorb time. At that point, the battery will be about 90% full. LiFePO4 batteries will be happier in the long run when they don’t stay at 100% SOC for too long, so this practice will extend your battery life. If you absolutely must have 100% SOC in your battery, absorb it will do! Officially, this is achieved when the charging current drops to 5% – 10% of the battery Ah value, i.e. 5-10 Amp for a 100Ah battery If you cannot stop absorbing the current, set the absorption time to about 2 hours and call Temperature compensation LiFePO4 Batteries do not require temperature compensation! Turn this off in the charge controller, otherwise, the charge voltage will be wildly turned off when it is very hot or cold. Check the voltage settings of the charge controller against actual voltage measured with a good quality DMM! Small changes in voltage can make a big difference during charging a lithium-ion battery! Change the charge settings accordingly!
Discharging an LFP Battery
Unlike lead acid batteries, the voltage of a lithium-ion battery remains very constant during discharge, making it difficult to guess the state of charge from the voltage alone. For a battery with a moderate load, the discharge curve seems LiFePO4 Discharge voltage vs. discharge voltage SOC LiFePO4 vs. SOC Most of the time during discharge, the battery voltage will be just around 13.2 volts. it was a really bad idea ™ to go below 20% SOC for a LiFePO4 battery. This has changed and the current LFP battery harvest will quite happily discharge down to 0% for many cycles. However, there is an advantage in pedaling less deep. It’s not just that going to 30% SOC will get you 1 / 3 cycles more than 0%, the battery will likely last more cycles than that. The hard numbers are, well, hard to find, but the cycle up to 50% SOC seems to show about 3 times the cycle life compared to .cycling 100%. Below is a table showing the battery voltage for a 12 Volt battery pack with respect to depth of discharge. Take these voltage values with a pinch of salt, the discharge curve is so flat that it is really difficult to determine SOC from voltage alone: small variations in load and accuracy of the voltmeter will negate the measurement.

State of Charge

Storing lithium-ion batteries
It is not a problem to put a lithium-ion battery away for a year, but make sure it is charged beforehand. Storing between 50% and 60% SOC is ideal. Storing batteries below freezing is fine even at very low temperatures than -40 degrees Celsius  or even less! The electrolyte in LiFePO4 cells does not contain any water. Even if it freezes (which happens at around -40 degrees Celsius depending on the formulation). Allow the battery to warm up a little before discharging it again. This is fine at -20 degrees Celsius and above. When discharging at temperatures below freezing point, an obvious loss of capacity occurs, reversed when the battery rises above freezing point and has a slightly accelerated effect on aging. Storage at low temperatures is certainly much better than storage at high temperatures: the aging of the calendar slows down dramatically at low temperatures. Avoid storing them at 45 degrees Celsius and above, and try to avoid keeping them as full (or almost empty) as possible. If you need to store batteries for a long time, just unplug all cables from them avoiding any possible discharge.

LiFePo4 Lifespan
The lifespan. If you don’t abuse the battery bank, avoid extremes and generally only use the batteries within reasonable limits, there is a maximum limit of about 20 years on calendar life. In addition to the cells inside the battery, there is also the BMS, which is made up of electronic parts. When the BMS fails, the battery will too. Ultimately the battery management system has to survive for as long as lithium-ion cells do. The processes within the battery conspire over time to coat the boundary layer between the electrodes and the electrolyte with chemical compounds that prevent lithium ions from entering and leaving the electrodes. The processes also bind lithium ions into new compounds chemicals, so they are no longer available to switch from electricity ode to electrode. These processes will happen regardless of our intervention, and are very temperature dependent! Keep the batteries below 30 degrees centigrade and they are very slow. Go beyond 45 degrees centigrade and things speed up considerably! Number 1 public enemy for lithium-ion batteries is heat. The calendar life has more to offer and how quickly a LiFePO4 battery will age. Bad at high temperatures, these batteries really don’t like to sit at 0% SOC and very high temperatures!

Also bad, although not quite as bad as 0% SOC, is sitting at 100% SOC and high temperatures for them. Very Low Temperatures As we discussed earlier, you cannot charge LFP batteries below freezing (and the BMS will not allow you to). It turns out that while it can be discharged below freezing, it also has an accelerated effect on aging. Nowhere near as bad as leaving your battery at a high temperature. However, if you are exposing your battery to freezing temperatures, it is better to do so while it is neither charging nor discharging and there is some gas in the tank (though not a full tank). In general, it is better to put these batteries away. a t around 50% – 60% SOC if they need to be stored longer. Molten Battery If you really want to know, what happens when a lithium-ion battery is charged below zero is that metallic lithium is deposited on the negative (carbon) electrode. , which end up puncturing the membrane and shorting out the battery (leading to a spectacular, unscheduled rapid disassembly event as NASA calls it, involving smoke, extreme heat, and most likely flames). Lucky for us this is something the BMS prevents from We move on to cycle life It has become common to get thousands of cycles, even at a full 100% charge-discharge cycle, with lithium-ion batteries There are some things you can do to maximize cycle life.

LFP Does & Donts
Keep the battery temperature below 45 degrees centigrade (below 30 degrees if possible) – This is by far the most important! ! Keep charge and discharge currents below 0.5 ° C (preferably 0.2 ° C) Keep battery temperature above 0 degrees Celsius when discharging if possible. Do not cycle below 10% – 15% SOC unless Do not float the battery at 100% SOC if possible Do not charge 100% SOC if you have no need That’s it! Enjoy