Basically it starts with how you intend to recharge your batteries, I am talking about your main recharging source here.

If you are going to be using any of the smart charging solutions, like solar panels and a quality smart regulator, or a smart 3 stage mains (240v) battery charger, or the Christie Honda petrol charger (set to hi charge), then in most cases the conventional wet cell deep cycle battery will serve you well.

If treated correctly (and few are) conventional deep cycle batteries can outlast AGM’s, but only if they are well maintained and cycled within their design perimeters, with both correct discharging/charging and equalising (now that a whole other story) and with keeping electrolyte (water) levels up.

Standard car and truck alternators are designed, for various good reasons to recharge car batteries to only 70-80%, and this works very well for normal cars and trucks, but when it comes to charging our storage batteries, where of course we need as full a charge as possible, that same 70-80% is not very helpful at all.

Really, standard alternators are designed primarily to top up quickly the surprisingly small amount of energy that is removed from the battery by the starter-motor on engine start up, and then to keep up with all your accessories, radios, head lights etc, they were never designed to recharge deeply discharged batteries, and they fall short in this area unless modified or replaced with a specialised charging alternator, and smart multi stage regulator.

Automotive battery chargers suffer from much the same less than perfect regulation as car alternators, and achieve much the same results, and take a much much longer time to do it.

As an example lets imagine you have a 100 Ah (Amp hour) battery, and you main charging source is you vehicles alternator or a standard automotive battery charger, now both of these will only charge this battery to about 75% (75 Ah), and you should not discharge your batteries below 50% (50 Ah in this case) of their capacity (see note below) if you want them to last, so all you can really safely use of this 100 Ah battery is 25 Ah, not much eh?

Note. Have you heard that you can drain deep cycle batteries all the way down, and then recharge them?

I hear this almost everyday that people have been told this, and by some battery sales people that should know better.

All conventional deep cycle battery manufactures say that their batteries are designed to be cycled to 50% of their rated capacity!

So each and every time you take these batteries below this 50% you are shortening their lives, and if you do it regularly and deeply you will even more dramatically reduce their lives.

 

The truth is that most people discharge their batteries far too low, way down until their fridges cut out, or their lights start to dim (does this remind you of anyone ??), at this point they have discharged their batteries so low that they are doing serious damage to their batteries, and consequently won't get anywhere near the life out of their batteries that they could and should normally expect if the batteries were cycled within their design perimeters.

Now remember the 100Ah battery with only 25Ah useable? A huge gain can be had if you are using any of the smart charging solutions, like solar panels and a quality smart regulator, or a smart 3 stage mains (240v) battery charger, or the Christie Honda petrol charger (set to hi charge), you can expect close to 100% (100Ah) charge,

So 100 Ah capacity, discharge to 50% (50Ah), that’s now 50Ah useable, twice what you had before!

The original AGM batteries were made in the US, brands like Odyssey, Concord, Lifeline, all excellent batteries, used extensively also in the aircraft and in the motor racing fields, but hugely expensive, there are now a lot of these (AGM) types of batteries coming out of China, and some are just rubbish.

My battery supplier (ALCO Battery Sales Australia) has found a couple of company's over in China that has been in production for many years, and have been selling batteries into the European market for a long time and have built up very good reputations, ALCO now import these batteries into Australia and are selling them through their own outlets and dealers like myself.

These AGM valve regulated batteries (also called SLA or Sealed Lead Acid) offer very good value, and when compared to standard deep cycle batteries in a dollar per useable amp hour format, they come out miles ahead, plus all the added advantages that I have already outlined, but there is still more.

Using a 100 Ah deep cycle wet cell Trojan (the best), my price $325.
Useable capacity if charged with smart charging system............................ say 50Ah, cost $6.50 per Ah

Useable capacity if charged from the alternator or auto charger only........say 25Ah, cost $13.00 per Ah

Using a 100Ah  AGM Battery, my price $360.

Useable capacity if charged with anything.............................................. lets say 80Ah, cost $4.50 Per Ah

Lets say you needed 100Ah useable capacity from your batteries, and your main charging system was from the vehicles alternator.

Now with conventional deep cycle batteries because you would only have 25% of your battery bank useable you would need 400Ah of battery bank, now there are a few ways you could do this, but the least expensive way would be four x 225Ah 6 volt Trojan batteries at a cost of $1,120.

Now with AGM batteries you could have just two x 100Ah giving you 200Ah total, so there is your 100 Ah with heaps in reserve and an easy life for the batteries, so only 2 batteries, at a cost of $720 all up, or better still you could use a single 200Ah battery for a cost of $695.00.