We can see up to 35A of real-time current and over 200Ahr a day coming into the battery bank under sunny conditions. Therefore, temperature sensors were also placed on the alternators and will decrease the current 50% if the following maximum temperatures are reached.ġ20A Balmar alternator -> de-rated to 100A 13.8V voltage cut-off 210˚F max temperature.Ħ0A Valeo alternator -> de-rated to 40A 13.8V voltage cut-off 190˚F max temperature. Since the LiFePO4 battery bank will accept as much charge as you can give it, this can cause the alternators to continually run hot and could eventually burn out the windings. Knowing that the LiFePO4 bank will become extremely sensitive to millivolt (0.01V) differences as it approaches its charging knee, this sense wire needs to be monitoring the bank directly to ensure that there is no unintended voltage drops from tapping into other places in the circuit.įor example, the lead acid battery sense wires were connected directly to the battery combiners to read house voltage, yet they worked fine within a 0.1V tolerance for activation and transition to absorption and float stages.Įach of our alternators were de-rated as follows for safety and lifetime considerations. The alternators charge the bank via direct connection with 1/0 cable to the batteries and the regulators are set to shut-off all current flow once the voltage limit is reached. Each are regulated and now set to a voltage cut-off of 13.8 V, using a sense wire that is led back directly to the battery bank. We have two different-sized alternators from two different vendors, one for each of our two Volvo MD2030 engines. In practice, if one charging source meets the charge limit, the shut-off should be coincident at all charging sources. We will test and report back on this option in a future LiFePO4 performance evaluation.Įach of our charging sources were chosen to have customizeable regulation.
However, since the inverter can draw up to 250A, and the bank can deliver much more than that, we may have the option of running our AC water maker ( CruiseRO Water) directly off of the bank in the future. In practice, we can’t imagine how our power draw would ever draw the battery bank so low. *Voltage difference between pairs (delta > 0.150 V): monitors cell pair balance.Ī low voltage cut-off was also programmed into the Victron inverter for 12.4V. *Voltage alarms for each cell pair (3.5V/3.1V = high/low): monitors cell pairs within middle 80% of working range. *Voltage alarms for the bank (14.0V/12.4V = high/low): monitors bank within middle 80% of working range. We set this alarm to go off for the following scenarios: For such a small package it is extremely versatile and alarms can be set for various parameters. The Junsi CellLog 8M hooks directly into the LiFePO4 bank and monitors voltage for cell pairs and the bank itself. We also used the voltmeter to calibrate the battery charge monitor.
TRIMETRIC BATTERY MONITOR INSTALLATION FULL
Therefore, the most accurate monitoring we do for determining full charge of the bank is using a voltmeter to check the state of cell pairs and the whole bank. Li+ ion battery charge and discharge curves are flat, yet extremely sensitive to the 10’s of millivolts (o.o1V) once you reach the “knees” of the curves at the extremes. Our working loads seen from normal “house" usage will be in the 1-15 A range from appliances like lights, refrigerator and computers, and on a given day we draw around 100-150 Ahrs total, depending on usage ~ well within the usable capacity of our 360 Ahr bank.Ĭharge monitoring takes place at several, redundant areas in Reach’s charging system and is regulated by voltage settings. Li+ ion batteries can take and give current at high rates ( i.e., have low internal resistance).
Our battery monitor ( Tri-metric 2020, Bogart Engineering) monitors real-time current draw and daily, cumulative discharge. Once installed, there are many peripheral factors that must be attended to: charge and discharge monitoring, inverter/charger settings, charging source regulation, and starter battery charging.ĭischarge monitoring of the LiFePO4 battery bank is virtually unchanged from lead acid.
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