![]() It’ll save the batteries in the long run, and it’ll keep the beers cold for longer! Now that I’ve given you a ‘get-out-of-jail-free-card’, we need to talk about the new kid on the block… lithium. If you have already gone and bought a 1250D, and you’ve only got the one 100Ah battery, tell the better half you’ve got Wes’ permission to go buy another two 100Ah batteries to make a 300Ah battery bank. ![]() Or, even better, speak to the manufacturer of your battery and to find out exactly what charging current will maximise its life. ![]() Instead of going and getting the biggest and angriest DC-DC charger you can get your hands on, it makes a lot more sense to get a charger specifically matched to what you need work on the rule of thumb outlined above. By throwing 50 amps at it, it will charge to full in just two hours (give or take), but it’ll also get hot and most likely damage the plates in the battery. Let’s just say I absolutely need the biggest, angriest, most expensive charger I can get my hands on, right? And so I go and get myself a you-beaut Redarc BCDC1250D to charge my single 100Ah lead-acid based battery. One of the biggest killers of batteries is running a whopping big charger and jamming way too many amps into your battery bank. This capacity charger is safe, will do the job perfectly and keep your batteries in good nick by not jamming too many amps down their throats.Īnd if you decide to add a second 100Ah battery down the track – making a 200Ah battery bank – the BCDC1225D 25 amp charger will still deliver enough charge (12.5 amps) to be above the minimum charging rate of 10 amps.īear in mind, the maths is different for lithium batteries you’ll see how further down. It will charge up at 25 amps maximum, which is well above the minimum the battery needs to charge at, and five amps below the rule-of-thumb maximum. There’s a pretty safe rule of thumb for most lead-acid deep-cycle batteries work on around five per cent of total amp-hour capacity as your minimum charging rate, and 30 per cent as your maximum, with somewhere around 10-20 per cent being about spot on.Ī bit of beer coaster maths will look like this:ġ00Ah battery = 5A minimum, 30A maximum and 10-20A ‘perfect’ charge current.Ģ00Ah battery = 10A minimum, 60A maximum and 20-40A ‘perfect’ charge current.įor example, if you have a 100Ah battery, a Redarc BCDC1225D (25amp DC-DC charger) would be just about perfect. The correct charging rate absolutely depends on what batteries you’ve got. charging) needs to happen at a similar rate to discharging, so while your starting battery will take just about all the amps you can throw at it, your deep-cycle battery needs to be charged at a slower rate if you don’t want to kill it. Where this gets interesting is that replacing the power you’ve used (i.e. And then, of course, there are the newer-tech whizz-bang lithium iron phosphate (LiFePo4) batteries. The difference between these and your starting battery is that they’re designed to discharge low power (say to run a fridge) over a long period of time, instead of discharge high power (say to turn an engine over) over a short period of time. These technologies include Absorbed Glass Matt (AGM), Gel or flooded wet-cell (just like your starting battery) designs. Most auxiliary batteries are a ‘deep cycle’ design, regardless of the technology inside. Your alternator is probably able to deliver in the vicinity of 70-100 amps to your starting battery, and as long as you don’t run it flat, and you keep the water in it topped up, it’ll last you more than a few years.Īuxiliary batteries are different. ![]() This works in reverse, too starting batteries can take a high-current charge quickly and happily. They’re built to be able to supply high current whether starting your engine or powering your winch, starting batteries are designed to handle a high-current draw over a short period of time. ![]() What’s of greatest importance is your batteries’ ability to take a charge, or more specifically your batteries’ technology.įirst off, let’s consider starting batteries. ![]()
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