Battery Monitors – Explained

Right, you are camping out nicely in the sticks, and you have done your homework and installed a dual battery system. This will protect your cranking battery, allow your auxiliary to charge when driving from the vehicle alternator, and allow charging from solar if you have it fitted. So what else do you need to worry about?

Well quite a bit really. What is going on with your battery system? How do you know what your battery terminal voltage is? How do you know by how much it is charging or discharging? How many ampere hours have you drained from the battery, and how many ampere hours are left?

Worst case scenario here is that you just sit back oblivious to what is going on with your battery and then wind up with a very flat one (and more likely a write off). Best case is that you have complemented your dual battery system with a microprocessor controlled battery monitor and you know exactly what is going on with your battery system.

So what specifically will you know, and how much is this going to cost?

Let’s go simple (and cheap) first. We are just going to monitor the battery terminal voltage. If you have a multimeter handy you can use this, but you can purchase a simple monitor that indicates battery voltage via a LED array.
These can sell for as low as $10 to $20. The downside is that to get some kind of reliability you have to monitor that voltage when the battery has been off load and off charge for a while – about 2 to 3 hours. You also have to have a good idea of the voltage levels and their meanings (10.5volts is flat, flat, flat!) Do not forget that to get the best life out of a battery it should not be discharged below 50% of capacity – this usually sits around 12.2 volts. You can measure the voltage on load and you should be looking for just over 12 volts for a 50% discharge. I’m sure you can see this is a bit of ‘wet the finger and hold it up in the wind’ technology. But it is better that nothing.

Now let’s go sophisticated (and not so cheap). A microprocessor controlled battery monitor will let you monitor many parameters. Battery voltage (Volts); Battery charge/discharge current (Amps); Ampere-hours consumed (Ah); Percentage State of Charge (%); Time to go at the current rate of discharge. Some will also provide a visual and audible alarm for over and under voltage , and/or battery discharged.

Of course all of this comes at a price, and depending on the degree of complexity and information you can be paying from $100 to $500. You need to shop wisely but you also need to make sure that you are protecting your primary power source. Deep cycle batteries do not come cheap, and if you have paid out for good batteries it is surely worth your while to get as long a life out of them as possible.

You can of course find much more information on the Internet and even via some of the links on this page.

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Related posts:

1. A Dual Battery System to Boost Your Camping Power
2. 12 volt Batteries for Camping
3. Solar Panels – Considerations.
4. Lights for Camping
5. Anderson Plugs – Anderson Connectors

Filed under: General Tips, Smart Ideas