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LFP LiFePO
LFP LiFePO
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Recommendations
Recommendations
Our LFP program is a generalized version of the recommendations provided by the top LFP battery manufacturers. For best
performance and compatibility, please consult your battery manufacturer and use the regulator’s advanced programming
features to adjust the LFP program as needed. LFP batteries are more sensitive to abuse than a traditional chemistry battery
and can fail catastrophically. It is HIGHLY recommended that the charging system as a whole be installed or inspected by a
qualified marine electrical installer that has experience with Balmar charging system products and LFP batteries. The LFP
profile is intended to work with the battery manufacturer’s battery management systems (BMS). The LFP profile IS NOT a
replacement for a BMS.
Many LiFePO
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batteries have a Battery Management System (BMS) that may disconnect the battery from the
alternator as a protective action or when charging is complete. The regulator must be shut down before the battery
is disconnected .Running an alternator without a battery will damage the alternator and may damage any attached
system. This is doubly true if the battery can be disconnected during high current charging, causing a load dump.
The load dump can easily cause a high voltage spike which will destroy the alternator’s rectifier, at minimum. This
is not a warrantable failure. To reiterate: THE ALTERNATOR MUST BE SHUT DOWN BEFORE DISCONNECTING
THE BATTERY. THE ONLY SAFE WAY TO SHUT DOWN THE ALTERNATOR IS TO TURN OFF THE REGULATOR.
The preferred method of turning off the regulator is disconnecting the regulator’s ignition (brown) wire, but if used
as an EMERGENCY ONLY shutdown, disconnecting the regulator’s power input (red) wire in addition to the ignition
wire has a very low chance of damaging the regulator.
LFP batteries will readily accept a damaging amount of current. Applying too much charge current to a LFP battery
will, at the very least, permanently damage the battery’s capacity. It is CRITICAL to ensure that the alternator is
not capable of exceeding the maximum continuous charge current rating of your battery (or batteries). As always,
check with your battery manufacturer for specifics. Your battery manufacturer may supply you with a “C-rate” for
charging and discharging. The maximum amount of charging current your battery can safely handle is determined
by multiplying the “C-Rate” by the capacity of the bank. i.e. 4x 100Ah 12V batteries rated at 0.5C charge = 400 Ah
* 0.5C = 200amps MAX. If your alternator is capable of outputting more current, at any time or condition, than the
battery (or batteries) can handle, you may use the Max Field % (Belt Manager) feature on the MC-618 to lower
the maximum field drive output, and thereby lower the maximum alternator output current. See page 10 of your
regulator manual for details and instructions. Be aware that it is not an exact 1:1 correlation between field output and
alternator output, so start with more reduction (lower output) than you think you need and adjust accordingly.
It is strongly recommended that an alternator temperature sensor (MC-TS-A) be used when charging LFP batteries.
Given the extremely high charge acceptance rate of LFP batteries, the alternator will be driven to full output for
almost all of the charge cycle. This can cause overheating in automotive style alternators resulting in a significantly
shortened lifespan. When equipped with the MC-TS-A temperature sensor, the MC-618 will help you protect
your investment by performing active alternator temperature control. This is accomplished by scaling back the
field voltage to the alternator when over the “AL1” temperature threshold. If you cannot use an MC-TS-A in your
application, you should monitor the alternator’s temperature (measure as close to the loop ends of the stator as
possible) and discontinue charging if the alternator temperature rises above the maximum recommended level. You
may also use the Max Field % (Belt Manager) feature on your MC-618 to reduce maximum output until a tolerable
alternator temperature is maintained under all conditions.
Battery Temp sensor
Most LFP battery manufacturers specify minimum and maximum charging temperatures to be from freezing (32°F,
0°C) to around 111°F (44°C). Again, consult with your battery manufacturer for specifics. When equipped with
a MC-TS-B, the MC-618 will lower charging to a negligible amount if the battery temperature exceeds the high
temperature threshold (b1H), or falls below the low temperature threshold (b1L). Charging will be re-enabled when
the temperature falls within the normal range. This feature is intended to supplement, not replace, your BMS’s
temperature protection features. Both battery temperature thresholds (b1L and b1H) should be adjusted such
that they trigger before the BMS engages in any protective actions. “B1H” should be adjusted to be slightly less
than BMS’s temperature high threshold. “B1L” should be adjusted to be slightly less than BMS’s temperature low
threshold. Be ware that an internal BMS would be measuring inside the battery, and the regulator temperature
sensor outside, so there may be a difference between the two readings at any given point. The battery temp sensor
will also reduce charging to very low amount if the temperature falls at or 32°F (0°C). This value is not configurable.
When triggered, charging will resume when the temperature rises above 39°F (4°C).
