Technical information
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Here we present a wealth of technical information relating not only to our products, but also to many other subjects that are directly connected with DC battery power systems. Most of the topics covered here have been compiled in response to questions from customers and installers.

The questions answered here are probably the most commonly asked questions or, perhaps more importantly, the subjects most commonly misunderstood.

An excellent example of this is Peukert's equation. Everyone seems to have heard of it. But few outside the purely technical arena seem to truly understand it, or even to know the correct formula. This is a great pity as not only is the formula simple to understand and apply, it is also extremely useful.

Many of these subjects are surrounded with urban folklore and myth, some of which have been around for so long it is the devil's own job to dispel them.

Each subject covered has a link on the left of the page along with a very short description of the subject on this page.

Peukert in brief. A quick explanation of the two main versions of the formula. For those who understand the effect but need a quick reminder of how to apply the formula.

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Peukert's Equation. (Peukert's Law), Sometimes known as "the shrinking battery effect". A 100 amp hour battery can provide 1 amp for 100 hours, or 5 amps for 20 hours, or 50 amps for 2 hours right? If only it was that simple. The heavier the discharge current, the lower the apparent battery capacity. Peukert devised a formula for calculating this effect. The extent of the effect is often greatly underestimated. Indeed the formula, though quoted by many, is usually incorrectly quoted or incorrectly applied and consequently gives incorrect results. Read our explanation which contains the correct version of the formula to see just what a huge difference to available battery run time heavy discharges make.

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Peukert Calculator. A spreadsheet in Microsoft Excel format that allows you to enter the battery capacity and Peukert's exponent. It then selects various discharge rates, calculates run times (note that the times are in decimal hours i.e. 1.5 hours is 1 1/2 hours = 1 hr 30 minutes), Peukert corrected amps and total amp hours available at the different discharge rates. It also incorporates a graph of discharge current against available amp hours. The extent of the effect may surprise you.

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The 50% rule states that deep cycle batteries should, on average, only be discharged to 50% available capacity. Many people have heard of this rule. It is a very commonly used guideline. So it is somewhat surprising that whilst many people successfully use this rule, few actually seem to understand it. So, where exactly does it come from and what is the reasoning behind it?

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More on the effects of Peukert shows a not often appreciated benefit of this otherwise irritating effect. Of course, it's not really a benefit but it can sometimes seem like it when a larger battery bank is required. Be sure to have read and understood Peukert's Equation before reading this. It will make no sense until you have done.

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Split Charge Diodes don't work properly. Because diodes have been around for so long, in so many installations, it is often forgotten that they are are inefficient, cause battery over charge and/or undercharge problems and necessitate the installation of expensive, complicated to install, external alternator controllers where, in many cases, they would otherwise not be required. Most engineers have learnt this from bitter experience. Diodes also don't allow for simple future expansion of the system. Click the link on the left to discover the many benefits the SmartBank split charge system has over split charge diodes.

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What size charger do I need? A very simple question, which should have a very simple answer. Unfortunately, like most things electronic, a simple answer rarely exists. Anyone who says something along the lines of "10% of the battery capacity", or "15% of the battery capacity" is a salesman not an engineer. Click here to find out why.

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How should a battery isolator switch be wired up? A seemingly very simple question. Many people fit one each in the engine and auxiliary positive leads. Others fit a single one in the combined negative lead and think they are being clever by saving one switch. Read this to understand why the isolator switch should NEVER be installed in the battery negative.

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What is Galvanic Corrosion and is it serious? Galvanic corrosion is accelerated depletion of a metal as a result of electrolytic action due to electric currents. It has an effect similar to simple "rusting" but is far quicker in it's effect. Yes it is serious, damned serious. Only recently have some people learnt just how serious. For a fuller explanation have a look here.

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What size relay should I install with my SmartBank? This depends upon your installation, battery bank sizes, charger sizes and possible loads. It is extremely important to install the correct size of relay. Fitting the wrong size could cause premature relay failure. In extreme cases it could cause a fire or other serious consequences. But this is no different than any other high power electrical equipemt. The system must be specified correctly in order to operate safely. You could read this to enable you to work out the required relay size yourself or you could contact us when you order your SmartBank Split Charge System with full details of your entire DC installation and we will happily work it out for you.

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Relay based split charge systems do NOT cause a dangerous initial current surge. There is a rumour that a fully charged battery, connected via a split charge relay to a very flat battery can cause a very high current surge from the fully charged battery into the flat battery which is not only dangerous but also flattens the fully charged battery. It is a rumour, and that is all it is. Click here for a technical explanation of just how and why it cannot possibly happen.

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My SmartBank Cycles between connected and disconnect. Why? Several possibilities. Charger too small, SmartBank set incorrectly, SmartGauge set incorrectly (in the case of SmartBank Advanced), see here for full details.

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How should I set the SmartBank Voltage adjustments? This is actually far easier than many suspect. Here are a few pointers.

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Everyone "knows" that external Alternator Controllers are required in order to properly recharge deep cycle batteries. That was perhaps true 10 to 15 years ago. It simply isn't always the case anymore. Unfortunately conventional wisdom says they are still needed in every case, when in reality they are not. Read this rather illuminating document to discover why they aren't always required.

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More on split charge relays. Why do some people have so much trouble with split charge relays? Mainly because the relays are not sufficiently rated for the job. Click here to see a comparison between a very common (undersized - badly rated) split charge relay and the type of relay we use with the SmartBank split charge system.

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Modifying SmartBank Standard to SmartBank Advanced. Full technical details in order to benefit from the added functions and features of SmartBank Advanced. Not a complicated modification but for experienced technicians only.

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Defeating the power-save function on SmartGauge-Smartbank installations. In certain very rare cases the power save feature of SmartGauge-SmartBank combinations can cause problems. Full technical details here to defeat this function. Very simple to carry out.

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Simple remote operation of SmartBank Standard. The remote/interface socket on SmartBank Standard allows communication with the old standard remote panel and also the new SmartGauge battery monitor. This socket can also be used to give a simple remote indication of "connected" status and allow remote emergency connect to enable engine starting from the auxiliary battery.

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Wiring Schematics and further details of SmartGauge operated in conjunction with SmartBank.

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Splitting battery banks is something we often see. By this we mean an auxiliary battery bank split into two separate banks, one feeding some loads, the other feeding other loads. Unless there is a very good reason for doing so it is something that is best avoided. The only real reason to do this is where it is considered absolutely essential that certain equipment maintains a battery supply in the event of the other batteries becoming completely discharged. There are sound scientific reasons for avoiding this practice at all cost. Click here for an explanation of why splitting battery banks in this way is such bad practice.

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Where should a single alternator be connected? Typically a single alternator installation comes as supplied from the factory. It will be connected to the engine start battery. Click here to see what a huge difference can be made by wiring it up properly.

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 Technical information
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Page last updated 02/04/2008.
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