Battery Monitoring

16
Jul 2021

Battery Monitoring and why it's important.

You've got all the nav tools to tell you where you are, but do you know where your battery is? OK, you know where it is, but do you know where its capacity is at?

Monitoring your battery isn't just about knowing its voltage, that is a small part of the picture to knowing how much charge your battery has and understanding not only its health, but the health of your whole electrical system.

Battery voltage isn't equivalent to state of charge, it may go up or down as alternator RPM changes and loads are either switched in or out of circuit. Even when the battery is not under load the voltage is not a good indication of charge level. Voltage changes with temperature and even depending on whether it was previously being charged or discharged (this effect is called surface charge).

A low voltage on your battery might mean your battery is flat, it might also mean you have too many loads attached. The combination of fridge, water pumps, lights and other equipment may be pulling the voltage down. And you have better things to do than watch if your battery is charging by watching the voltage go up over time.

A good battery monitor will show you the charge and discharge current. Using this extra feature lets you know if current is going into the battery, if your engines are running at high enough RPM to be charging the battery, or if your solar panels are working as well as you hoped.

With the engine off you can tell if you have too many loads on the battery by reading the discharge current, and importantly, before you call it a day or you leave your boat moored, you can check that all of the unnecessary loads have been switched off. This would be especially important if you use your starter battery for house battery functions, lights, water pumps, etc.

We step up a level if the battery monitor has state of charge monitoring. The Victron BMV (Battery Monitor Victron) and Smart Shunt range has this feature and when programmed with the capacity of the battery, will monitor current going into and out of the battery and can report state of charge as a percentage of the total capacity. Now we have the added capability of seeing not only how much current is going out of the battery, but how long before it is at its lowest allowable level with the present load.

This monitor can also automatically start a generator on low voltage, low state of charge, and warn you with an audible buzzer.

If you have a separate starter and house battery, both of these can be monitored by the same battery monitor.

Monitoring your battery state of charge gives you peace of mind while you are out on the water, you know all of the essential services will be kept running and you'll have enough battery power to crank the engines when you need to. But you aren't always out there to keep an eye on battery health and it's not something you want to worry about. This is where remote monitoring comes in.

Via the Victron Remote Monitoring (VRM) cloud service you have access to the readings on your boat by using the GlobalLink 520 . Connecting the BMV monitor or Smartshunt to the GlobalLink 520 you get to monitor the battery parameters and have a logged history of the battery usage. The GlobalLink 520 connects to 4GLTE-M and comes with 5 years paid connection with no monthly fees.

You can see if the battery has a full state of charge before you even leave home, if a load has been left on or if a bilge pump is running and it should not be or is not running and you expect it should be. The history reporting allows you to see repetitive loads, bilge pumps again being an example.

The Victron remote monitoring also allows you to set up alarms so you can be notified by email of a is low state of charge, low voltage or even when your battery has charged.

The GBL520 has two digital inputs making it possible to monitor a Victron MPPT charger and see how the solar system is operating. A remotely controlled relay on the GBL520 relay output allows you to control a load, maybe getting the fridge cool before you get on board.

These few simple units, the BMV monitor, smartshunt and GlobalLink 520 give you the capability of not only monitoring your battery/ies, but monitoring it remotely and controlling a load.

Most large boats have larger appliances and an inverter to power them, that requires more power. Microwave ovens, air conditioning, water makers, all require more power and a separate battery bank from the starter batteries is the best way to go.

The best part about the battery monitoring solutions from Victron Energy, is that they also integrate with many of the world's leading Marine Glass Bridge manufacturers allowing you to have full control and real-time feedback from the helm. If you have a larger vessel, having this important information available is key to ensuring an enjoyable day on the water

With multiple options available to suit small to large boats, talk to the battery engineers @ Master Instruments about the best battery monitoring solution for your vessel today...

By Robert Hoehne - Master Instruments

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