From this the electronic tester is able to calculate the health of the battery and whether any of the cells has failed. Instead they send a low level electrical signal through the battery and measures the batteries internal resistance. This type of tester does not put a load through the battery as a resistance type battery tester does. If one of the cells is low on electrolyte, below the cell plates, a load that great could cause arcing inside the battery and a possible explosion! This can cause serious injury and sulfuric acid burns to the person carrying out the test! Because of this sealed 'maintenance free' batteries must be tested with an electronic conductance tester. This type of test can be extremely dangerous on a sealed lead acid battery. Note the resistance coils glowing red inside the tester! These simple testers apply a massive resistance of three times the battery cold cranking amps (CCA) rating for 20 seconds and in the case of a 12-volt battery a reading of greater that 9 volts indicated a good battery.Ī 'resistance type' of battery tester in use. The usual way to test a lead acid battery was to carry out a 'high-rate resistance discharge test' using a resistance type battery tester. Because of this these 'Maintenance Free' batteries, for example, are excellent for use as a trolling motor battery on a bass boat.īut there is something very important to know about 'Maintenance Free' sealed lead acid batteries and that is how you go about testing one.

This is a great feature especially when the battery is difficult to get access to.

These are often called 'maintenance free' because their sealed construction means that there is no longer a necessity to check the cells and add distilled water. So what does this mean for boat owners? The most common type of advanced marine battery is the Sealed Lead Acid type. You do that don't you?īut times are changing and now we have Sealed Lead Acid, Gel and Absorbent Glass Mat (AGM) batteries. This type of battery requires a regular check of the fluid (known as electrolyte) level in the cells and add distilled water as necessary. It used to be all marine batteries were of the simple open vented lead acid type that had been around since the early 1900s. We even have LED lights and GPS speedometers! The heart of our boats electrical system, the humble battery has also been changing lately.

We now have electronic computer controlled engine management systems, advanced electronic navigation and fish finders. It seems that everything electrical on our boats has improved dramatically over recent years.

Sealed marine batteries