Charging LiFePO4 Batteries
Every day we get questions about charging LiFePO4 batteries. We decided to review some products that work great with our Battle Born LiFePO4 batteries. To begin the series we will cover some of the basics of charging batteries and then cover the products in other segments.
Charging a battery basically means applying an external voltage to drive current from the anode to the cathode of the battery. The charger acts like a pump – pumping current upstream, opposite the normal direction of current flow when the battery discharges. When the charger’s applied voltage is higher than the open circuit battery voltage, then the charging current flows. During this process, the battery open circuit voltage increases, approaching the applied voltage of the charger.
The charger can behave in several different ways during the charging process. First the charger can steadily increase its voltage in order to keep the current flow constant. This is the first stage of the charging process – typically called the “bulk” charging stage. During this stage, the charger adjusts its applied voltage to deliver the maximum current to the battery. For example, a 10 Amp charger will deliver its maximum of 10 Amps during this bulk charging stage, and the applied voltage will increase up to a maximum voltage, or “bulk voltage”.
Once the bulk voltage is reached, the charger enters a second stage, called the “absorption” charging stage. During absorption, the charger applies a constant voltage, called the “absorption voltage”. As the battery open circuit voltage approaches the absorption voltage, the current flow steadily decreases down to zero.
At this point the battery is fully charged. However, a lead acid battery will rapidly lose charge when the charger is disconnected. So, instead of turning off, the charger enters a third stage called the “float” stage, in which the charger drops to a lower voltage and holds at that voltage. The point of this stage is to keep the battery topped off, and account for the fact that lead acid batteries tend to drain, even when there is no load connected.
These stages combined sequentially form what is commonly called the “charging algorithm”. A battery charger may generally be classified by a charging current (i.e. the max charging current) and a target battery voltage (12V, 24V, 36V, 48V, etc.). But chargers may also include multiple charging algorithms (typically classified as “AGM”, “SLA”, “Gel”, “Wet”, etc.). A closer look reveals that each algorithm has its own unique parameters, including:
• Bulk voltage
• Absorption voltage
• Absorption time
• Float Voltage
Among charging algorithms for lead acid batteries, there is a wide variation for these values. The bulk and absorption voltages typically vary between 14.0 and 14.8 V and the float can vary between 13.2 and 13.8 V. The 12V Battle Born batteries sit comfortably right in the middle of these ranges. We recommend a bulk and absorption voltage of 14.4V. A float is unnecessary, since Li-ion batteries do not leak charge, but a floating voltage under 13.6V is fine.
Here are a few of our FAQ videos that talk about charging LiFePO4 batteries.
In this blog series, we will post the results of our tests for a variety of LiFePO4 chargers – including converters, inverter/chargers, and solar charge controllers. In each case, we will report on the uniqueness of the charging algorithms for each brand, explore the efficacy of using the factory default settings for charging Battle Born Batteries, and determine what can be done to achieve the optimal settings.
Since this is a work in progress, please contact us at any time at 855-292-2831, and we would be happy to address your concerns about charging LiFePO4 batteries.
Ming Dinh | Aug 13, 2017 at 1:45 pm
Hello,
Do you sell smaller batteries? I am looking for something in the range of a 50ah, 12V battery.
Do you ship to Vancouver, Canada, and can you supply an estimated shipping cost?
Thank you,
Ming
Will Olney | Aug 16, 2017 at 10:18 am
We will be releasing a 12v 50ah in the next week keep an eye out on our Facebook page and website.
Crosby Grindle | Dec 27, 2017 at 8:57 pm
What is the reserve capacity of your batteries? I may not be using the correct term but battery manufacturers often specify the amount of total capacity available before there is significant voltage drop. I know this capacity is typically much better with LiFe batteries – sometimes 90%. Can you provide similar information about your batteries?
Will Olney | Dec 28, 2017 at 8:09 am
Hello Crosby,
Our batteries don’t necessarily have a reserve capacity that is more of a term used with lead acid batteries, but you are able to use a full 100% of the batteries capacity. please give us a call if you have any other questions.
775 221 8897
CLIFFORD G MILLER | Jul 9, 2018 at 9:30 pm
When charging a smaller ah lithium battery such as a 7 to 9 ah do you use the same settings on a programmable ac/dc power converter as you would on a larger ah lithium battery?
Sean Nichols | Aug 3, 2018 at 8:22 am
Depends on the chemistry. Best thing to do is contact the mfg of the battery and ask them for the charging parameters.
Bradley Pfanner | Aug 12, 2018 at 4:20 pm
Could I charge this battery with jumper cables connected to a running car battery?
Dianne F | Aug 13, 2018 at 10:36 am
Bradley,
This is a possiblity as long as you don’t exceed 100ah. If you have anymore questions please feel free to call us 855-292-2831 or email us at [email protected]
HT | Nov 4, 2018 at 7:00 am
Please tell me the optimum AMPERAGE level for charging Battle Born 12v 100ah batteries. Thanks.
Dianne F | Nov 8, 2018 at 8:54 am
Hi there, I will include the criteria of amperage level for our batteries:
100 Amp Continuous Current
200 Amp Surge Current (30 Seconds)
If you have any questions, please let me know. You are welcome to reach us at [email protected] or give us a call at 855.292.2831. Thanks!
zoltan szabatin | Nov 14, 2018 at 6:33 am
Hi
I could be wrong, this is what I learned : problem with a”normal” RV battery charger is,:having a float mode?
Dianne F | Nov 16, 2018 at 2:53 pm
Zoltan,
That’s a good questions. Our batteries do not require a float charge. But they can be in float mode as long as the float is around 13.6, it is OK for the batteries to float around that voltage.
Jim Rout | Dec 23, 2018 at 8:05 am
We currently use 2 external Alphacell 220 GXL 109AH batteries in serial, connected to an APC Smart-UPS 700. We are looking to replace the 220GXL batteries but keep the APC-UPS. We remove the internal battery from the APC-UPS. Will a LiFePO4 battery work in this instance as a replacement for the Alphacell 220 GXL lead acid batteries? We have to replace about 20 of these batteries.
In some instances we use a single 220 GXL connected to an inverter and a standard marine battery charger. This is then connected to a transfer switch which switches from wall outlet power to inverter power in the event of a power failure. Can the LiFePO4 batteries be charged with a standard marine battery charger ?
Dianne F | Jan 3, 2019 at 8:39 am
Hello Jim,
lithium batteries power 12 volt devices with the proper voltage just as a regular lead acid battery so running devices will not be a problem. Charging Lithium batteries requires a voltage in between 14.2-14.6 volts for bulk/absorption, 13.6 or lower for float and should not have an equalization stage. Typical lead acid chargers can work in some instances but we would have to get the model # for your marine battery charger and check the settings for compatibility. Please give us a call at your earliest convenience so we can go over the details. 855-292-2831
Thank you,
Wayne Robey | Jan 5, 2019 at 7:02 pm
The Pb battery chargers I know of have a fixed absorption time (which may be programmable) BUT it seems that the best way to charge a Li battery is to switch from absorption to float when the charging current reaches a prescribed value, so I have 2 questions: Do you know of any PV powered chargers that can switch from absorption to float using a external signal (logic level input) and if using a constant but programmable absorption time, what is a good time (for a specific voltage)?
Dianne F | Jan 7, 2019 at 5:42 pm
Hi Wayne,
The Victron MPPT charge controllers allow you to set the absorption time(and voltage 14.4v) to the desired level. In the case with our lithium batteries its about 20 minutes per battery. You can also set the float voltage to the recommended 13.6v after the absorption time is achieved.
Thank you,
John Bell | Jan 7, 2019 at 9:20 pm
I frequently use my RV in below freezing conditions in the winter. I plan on an inside, normally heated battery location, however, their are times when the battery temp might drop below freezing. I understand that your internal BMS has a low temp disconnect to prevent damaging the cells when charging when the batteries are too cold. Could you elaborate on the process of the disconnect/reconnect if this occurs.. In my application would you advise that I add external charger disconnects to prevent accidental charging, such as from solar panels, until I’m sure the battery warms above freezing? Or will the BMS provide this function?
William S. | Jan 10, 2019 at 11:18 am
I have 6 12V 200AH lithium ion batteries, and I was wondering what would be the best way to charge them all at once, and how many Amps and volts my charger would have to put out to charge them in at least 10 hours from being completely depleted.
Dianne F | Jan 10, 2019 at 1:10 pm
Hello William,
We don’t make 200AH batteries, so I’m assuming these are another manufacturers batteries. I would check with your battery manufacturer to answer this question for you. I can only speak for our 100AH batteries.
John Bell | Jan 15, 2019 at 7:04 am
Recently installed my 2 100AH Battleborn Batteries in my RV and programmed my solar and inverter/charger to your recommended specs. In case you missed my earlier post, regarding the low temp disconnect of the internal BMS. My question is weather you recommend I install additional charger disconnects to protect the battery from charging in freezing conditions or is the BMS designed to disconnect and reconnect when temp rises to a safe level. Thanks.
Dianne F | Jan 15, 2019 at 8:39 am
Hello John,
The BMS is programed to handle temperature compensation. No need to add a battery disconnect for charging. When the BMS senses the temperature is below 25 degrees F, it will not let the battery accept a charge. Once the temperature is back up above 25 degrees F, the battery will be able to accept a charge again.
James Griffith | Jan 17, 2019 at 11:54 am
What percent increase in battery life would you expect if your battery were only charged in the range 25-35F vs only charged in the range 35-45F?
Dianne F | Jan 17, 2019 at 3:14 pm
James,
The colder the temperatures you are charge in, the less life expectancy you will incur. We don’t have a specific % increase or decrease calculation for these temperatures but around 70F is optimal for maximum life expectancy.
Thank you,
Jeff B Bohrer | Jan 23, 2019 at 10:03 pm
Sorry I forgot to include my name and email on the first comment I sent.
I just received 3 of your 100 ah 12v batteries, do I need to charge them before installing or using them?
If I decide to add another in a few months, are there any special procedures that I need to follow?
Dianne F | Jan 24, 2019 at 11:17 am
Hi Jeff,
We always recommend charging the batteries completely before the initial use. This becomes even more important when connecting batteries in series.
Adding another battery in the future will not be an issue, again just bring all the batteries to a full state of charge before using.
Thank you,
tim conley | Mar 17, 2019 at 4:18 am
Hello
can I leave my rv plugged into shore power for an extended period of time with out harming the batteries.
Dianne F | Mar 20, 2019 at 8:27 pm
Hi Tim,
If you are storing your rv and wish to have it plugged in, we would recommend a float voltage of 13.6 volts. If you have a higher voltage applied in float(such as 14.6) then we would recommend that this be no longer than 3 weeks at a time.
Thanks,