![]() Okay, that's probably enough questions for now! As you can probably tell, I'm new to this electronics stuff, so I'll be grateful for any answers at all. I've googled a bit and found references to "buck" converters - would this be suitable? That's likely to be quite noisy when the alternator or mains charger are supplying it. I know little or nothing about op-amps - does anyone have a schematic (or better yet, a ready-built board) that can do that?įinally, I'll need to find a way to power all of this from the 12V supply. Is it crazy to think of using a shunt resistor and just measuring the voltage across it with the ADC? One problem with that seems to be that the voltages involved are very small - typically a maximum of 75mV with shunts like this Is there a simple way to boost that? I found another thread discussing something similar where it was suggested that an op-amp circuit could amplify the signal to give a value suitable as input to an ADC. I've seen mention of Hall effect devices but I don't know anything about them. I guess a couple of 1% resistors could be needed to divide the voltage to the input range of the ADC?īut I'm not sure about how to measure the current. ![]() Once I've got an ADC setup working, measuring the voltage across the battery terminals is pretty simple. Some sort of ADC will be needed, and I'm considering a RaspIO Analog Zero I'll probably use a Zero W to allow for a wifi connection to the Internet. ![]() So far, I'm thinking that a Pi Zero is a good choice. The power consumption of the system needs to be kept fairly low, since it will be running from the 12V battery itself. The maximum current flow will probably be when the mains charger is in use. It will be bidirectional, depending on whether the battery is charging or discharging. The current flowing will vary widely, from zero to perhaps 30A. There is also the option of measuring the raw voltage coming from the solar panels at some point in the future, which may be higher. The voltages will be in the range of about 10V to 14V - a nominal 12V lead-acid battery system. I may later want to add security cameras, motion detectors, GPS, etc - so I think a Pi is the way to go, rather than something like an Arduino.įocusing on the input side: the system needs to be able to measure current and voltage with reasonable accuracy. Ideally the data would be uploaded to the cloud so I can monitor it remotely - useful since the van is kept in storage some miles from home when we're not using it. I'd like to use a Pi to monitor the state of the battery - measuring voltage across its terminals and current flow. It is recharged by solar panels on the roof (when it's sunny!), the alternator (when the engine is running) or a mains charger (when we're connected to mains, at campsites). I own an old campervan with a 12V battery system, The battery powers lighting and a (fairly power-hungry) compression fridge - along with a 12V TV, phone chargers, etc. The series of resistors connected at the inverting terminals of each op amp makes a voltage divider and exact comparing voltage is supplied to each op amp.(First post here, hope I've posted this in the right place) Comparison is done between the two terminals of each op amp and accordingly output is shown. So 6 op amps are used to compare and display the appropriate level of voltage. Here for the development of the circuit, the 12V to 9V range is divided into 6 parts as 9V, 9.5V, 10V…11.5V. My point to say all these is that to monitor a 12V battery, it is sufficient to monitor the battery voltage from 12V to 9V range and a voltage below 9V should give a warning for LOW BATTERY VOLTAGE. Any inverter designed to use with a 12V battery should be comfortable to produce a constant AC output voltage during the fall of battery voltage from 12V to 9v approximately. So it is generally considered that if the output voltage of a 12V battery changes from 12V to 9V approximately, it is constant and after the voltage falls below 9V, it is considered to be discharged and need to be charged again. Practically, it is not possible and the output voltage of the battery decreases gradually as load connected to it draws current from it. ![]() Generally a 12V battery is expected to produce a 12V dc voltage all the time until it gets discharged. ![]()
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