They are able to build a bank model down to the cell level and these are not small installations, 10kW, -48V banks using on the order of 120 VRLA batteries (each the size of a 40mm ammo can) in a room-size rack. There hasn't traditionally been a fast and accurate method to judge battery health without taking the batteries off line and test them so they're developing reliable remote sensing to do that without waiting for failures or wasting good batteries as well as not requiring periodic site visits. They are doing electrochemical impedance spectrometry and intelligent charging and metering to eliminate the biennial standard replacement schedule the tower owners usually follow. They were primarily concerned with UPSes (the primary customer is cell tower owners) and to a lesser extent electric vehicle banks. One of the places I recently worked had ongoing work with INL battery lab and a project they are involved with at Montana Tech dealing with online SOH calculations for large banks. How much depends on the unit and how often you test your battery and recalibrate the gauge.Ĭlick to expand.This statement has a ton of truth in it. Your charger will do it's thing and you'll find over time your fuel gauge will no longer match the capacity of the battery as the actual SOH drifts from the measured and assumed. Most fuel gauges are very simple and don't even adjust for rate of current usage (knowing rate is much better than just amp-hour counting at eliminating Peukert effect), charging efficiency or self discharge, which are critical to know true SOC. Another I know builds a faithful model is the Balmar (not on your list, here: Balmar Smartgauge ) units, their learning technique is sound but they do AFAIK a voltage-only technique, which is valid if done right. I know the SmartGauge has a sophisticated technique to judge SOC and the Xantrex Link boxes are well understood by boat owners. Even then I wouldn't put that much faith into them without knowing the algorithm they are applying to judge SOC, which should at least know current battery temperature. My plan will also include a solar setup, shore charging port (thinking CTEK), inverter, fridge, etc.Ĭlick to expand.They are all just glorified VOMs, measuring voltage and current in & out to infer a state of charge from an initial trained (or possibly an entered value) baseline. I guess that could be fine, since the starting battery is really only used for starting, so doesn't really need to be monitored. Looks like the same as the xantrex unit, but rebrandedĪre there any others I'm missing? It seems that none of them are capable of monitoring the State of charge of more than 1 battery/source. This is the one I'm most excited about, it's new, but it's rather large, and you can only monitor the SoC on one battery. Here are the options I've discovered, and all require the use of a shunt: The National Luna devices are basically glorified voltmeters. Minimum Current Draw: 1mA in Standby Mode (The 7517 has the option of a power saving / Standby Mode which turns the display off after / 4 hours of being stationary.I'm planning out my setup, so far I've settled on the Blue Sea ML-ACR.Īs far as battery monitors go, voltage is an okay measurement, but I like overkill and the ability to truly monitor the battery's capacity. Specifications: Accuracy: ± 1% at 36 Volts DC
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