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When bigger is not always better

When bigger is not always better

Bigger is better in many cases, especially when it comes to touring Australia. Well-engineered and over-spec’d equipment will generally see you through the toughest conditions with plenty of head room and ensure reliability to cope with unexpected extremes.

If you look at the specifications of leading brand equipment they are usually on the more conservative side of what the gear can actually do, unlike the optimistic specifications the competitors that sell on price point alone. Meaning more often that not the conservative approach will ensure that the equipment delights rather than disappoints.

The bigger is better approach is shared widely amongst tourers when it comes to setting up their rigs because it gives them peace of mind when heading out into the bush, keeping far away from any limits of operation.


 When heading out, the bigger is better approach is widely accepted amongst many tourers. (C) Carlisle Rogers


This theory is no different when it comes to the world of electrical, fitting a bigger battery bank and carrying additional solar panels will ensure the lights stay on and the beer stays cold, even if mother nature throws an unpredicted week of storm clouds over your head or the kids forget to latch the lid on the fridge.

Running cables two sizes above requirements ensures your 12-volt gear runs with no electrical losses and has room for future additions or changes.  

There are times however when going bigger can be detrimental and we need a more controlled approach, and battery charging is no exception.


Going nice and slow


Charging batteries can be likened to cooking a slab of beef brisket, best results are obtained by sticking to the ‘low and slow’ method. For a brisket, the right temperature, wood and cooking time ensures the smoke is able to penetrate the surface, the fat can render and the juice will flow throughout.

To save time you could always crank the smoker to 200 degrees and have your brisket ready within the hour but in reality, that approach will end up ruining the meat and leave you with something you could mend your boots with.  

Charging a battery works in a similar way by controlling the correct amount of current and voltage in the form of a staged charge profile. This allows the chemical process inside that power producing plastic box to take place.

Lucky for you, charging a battery doesn't require this amount of commitment and attention, and a quality DC-DC charger like a REDARC BCDC will handle all the control and adjustments with its three-stage charge. All you need to do is select the correct sized charger, set the profile and the charger will handle the rest.


When charging a battery low and slow, we're not suggesting fitting a 6-amp charger for your 100ah AGM and then driving around for ten hours in an attempt to gently caress the charge back into the battery. Just stick within the specification for maximum charging current that all leading battery manufacturers have recommended for their batteries and you'll be fine.


When things go wrong


Exceeding your batteries current specification with a bigger charger can have a range of different impacts, worst of all internal damage which will decrease performance and shorten life. For lead acids, this comes in the form of excessive heat causing a lower gassing point, which in effect causes the electrolyte to dry out prematurely.

In the case of an AGM, gassing causes bubbles to form on the plates which may be difficult to recombine and result in less active area of the plate to accept and deliver charge. In extreme cases, active material can be torn from the plates and reduce life capacity and also cause complete battery failure.

Too much current will also restrict the battery's ability to store its full capacity potential, meaning too much current equals wasted energy and less amp hours stored.


Some common problems with excess current can include, less capacity, reduced battery life, gassing problems and complete battery failure


Let's put this all into context, remembering amp hours are the batteries capacity like a tank stores litres of water, batteries store ‘amp hours’ of energy.

Over a 6 hour period, a 20amp charger can deliver 120ah worth of energy to charge a 100ah AGM to 100%. Using a 40amp charger which can deliver double the power at 240ah will only charge the battery to 80%, the excess energy is not stored but turned into heat.

The higher charge current does not allow for the battery to fully saturate and convert to stored energy.


Excess energy is turned into heat because the battery is incapable of storing the higher current


Getting it right the first time


At the end of the day batteries take time to charge and some are faster than others. Lithium batteries generally top the list when it comes to happily accepting more charge current in a much shorter time period, but are also on the top of the list when it comes to cost.

Also another relatively new player in the automotive battery market, lead crystal, is able to be charged from a comparatively larger charger with a quicker charge time. However, these batteries turn things on their head as many have a minimum recommended charge current.

If an undersized charger is used, the lead crystal may not get to 100%, so these batteries don’t react as well from a lower charge current sources like solar.

What it comes down to is tuning your system by selecting the best battery for your requirements matched with a suitable charger. This ensures your electrical system is operating at its optimum level, giving the best battery life and performance possible.


Tuning your system ensures everything operates at its optimal level


As an example, a 100Ah AGM with a 30A recommended charge rate would work well with the REDARC BCDC1225D (25A) In-Vehicle Battery Charger or Manager30 Battery Management System (30A), but the BCDC1240D (40A) would be too much current.

Use two 100Ah AGM batteries and the BCDC1240D or Manager30, would be a great combination.

Understanding the design of your battery system and setting it up how you need it to work is far more important than buying the cheapest 100Ah AGM you can get your hands on. Likewise, with choosing your charger – bigger is not always better. Tune your charging system and battery correctly and you will get many more miles from it than you would by just “opening the taps”.

To get you started, try our handy dual battery calculator, so you can stay in charge. 

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