When you realize your battery pack needs a monitor, do you struggle with whether to choose a voltmeter or a coulomb meter? Voltmeters are cheaper, but can they meet your expectations? Coulomb meters are more expensive – is it necessary to use one? Our suggestion is not to choose the most expensive one, but to select the one that best suits your situation.
(1) Analysis from an Accuracy Perspective
In a previous article, we discussed the fundamental differences between voltmeters and coulomb meters. Simply put, due to the influence of battery internal resistance and charge/discharge cycles, the accuracy of a voltmeter is generally much lower than that of a coulomb meter. Therefore, you can choose between a voltmeter or a coulomb meter based on your own accuracy requirements.
(2) Analysis Based on Battery Type
Both types of meters can be used with mainstream battery types on the market, such as lead-acid, lithium ternary, and lithium iron phosphate batteries. However, we recommend choosing a different meter based on the specific battery type. For example, both meters can be used for lead-acid batteries, but for lithium batteries, a coulomb meter is preferred. As mentioned in the previous article, a voltmeter estimates the state of charge percentage based on voltage. The discharge curve of a lead-acid battery is very steep, meaning a specific voltage value can correspond relatively clearly to a specific state of charge percentage. In contrast, the discharge curve of lithium batteries, especially lithium iron phosphate batteries, is very flat, almost a straight line. Except when nearly fully charged or nearly empty, the middle 20%-80% range cannot be judged by voltage; slight voltage fluctuations can cause the percentage to jump drastically. Therefore, we recommend using a coulomb counter for lithium batteries whenever possible.
(3) Analysis Based on Price
Voltmeters have an absolute advantage in terms of price, while even the most basic coulomb counter costs around $20 USD. If, based on the above analysis, you determine that a voltmeter is sufficient, then choose a voltmeter. If a coulomb counter better suits your needs, then looking for a cost-effective coulomb counter is also a good solution.
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