Battery Test Results

AGM
During the process of battery testing there were two clear winners. Out and out first place went to the 85Ah Absorbed Glass Matt (AGM) batteries which performed the best in the 24 hour and 4 hour battery charging tests. The graph below shows the AGM 24hr test, AGM 4hr test and the best and worst results (thin lines) of the batteries in the test. As you can see there is no line above the AGM because it was the best in test, and the bottom thin line represents the Calcium 4 hour test results. The vertical scale shown is the voltage of the battery with a 4.6 amp load on it during the test and the horizontal scale at the bottom of the graph is the time elapsed in hours. My voltage data logger only reads in 0.05 volt increments, and that is why the lines in the test results arent smooth.

Marine Battery
The other battery which impressed me was the Marine Start battery which performed well, and was considerably cheaper - $186 compared to the AGMs $290. So when comparing performance with price I think the Marine start batteries definitely did very well. The Marine Start came second overall in the 24 hour test, and in third place to the AGM and Optima (in that order) in the 4 hour test.

Optima Battery
The spiral wound Optima battery was pretty disappointing in these tests. At $450 it was the most expensive battery in the test, however could not outperform the AGM. In fact the Optima came in only third place in the 24 hour test, but was a close second to the AGM in the 4 hour test. The spiral batteries claim to fame however isn’t that they deep cycle better than other batteries, it is that they charge up faster and can discharge current faster for high amperage applications like winching a vehicle or inverters. So yes, the Optima did prove its self quicker to recharge than most batteries in the test which is one of its major selling points. The other thing that you need to consider in these results is that we haven’t tested the batteries performance under high amp draws like winching or running large inverters. If you are looking at these applications the Optimas may still need to be considered against other battery types.

Deep Cycle
The basic Century Deep cycle battery (which is part calcium) costs around $189, so in my option Id go straight for the Marine start battery which is only $186 and has outperformed the basic deep cycle battery hands down. As you can see from the graph, the results for the deep cycle are close to the worst in the test, with only the full calcium battery being worse.

Calcium
This battery, as I expected at the start performed worst in the tests. Having had a lot of experience with calcium batteries in dual battery systems I knew that they would perform poorly during short charge times, however I didn’t realise how poorly they would do in the 24 hour test. The CTEK 25 amp charger is set up to charge calcium batteries; however they really seemed to struggle in our tests. Some could argue that a dedicated calcium charger is required to recharge calcium batteries properly, however this doesn’t fit in with the Real World testing that we are trying to conduct. Most of my customers want a battery that performs well in their existing dual battery systems, or on their existing battery charger. The main advantage of the calcium type batteries is that they have a longer shelf life than traditional batteries, which battery companies love, and also heard that they are cheaper to construct. None of these advantages however, really benefit customers that much and that is why some battery companies are starting to go away from full calcium type batteries.

Final Comments
Overall I’m really impressed with the AGMs, personally I think they recharge well, deep cycle well, are well sealed, take vibration well and can handle high currents from inverters and winches. Certainly, this type of battery would be my first choice. As a budget alternative I would also be happy to use the Century Marine start battery. At around $186 they are well priced, have plate locks to withstand vibrations, deep cycle well, charge well and being a starting type battery should handle and winch or inverter ok too. The Optima type battery still can’t be discounted. This type of battery has the highest amperage charge and discharge rates for applications like winching and for running inverters. However Id love to do more testing to see how they compare to the AGM types under these applications. Personally I wouldn’t bother with the basic deep cycles or calcium batteries, they just did perform well enough and the marine start battery is generally cheaper than either, meaning these batteries don’t even win on price.