Alternative Energy systems troubleshooting for dummies, version .001 July, 2002. Some glaring errors fixed on 06.06.03

This document is and will be a work in progress so it will change as time and inclination permit.

Copy freely, just don't take credit for my work or the work of others.

Started by TomW

Since this document is geared towards the Alternative Energy [AE] and Renewable Energy (RE) fields I will try to concentrate on the systems and components most likely to be encountered in those fields.

Please, please always consider safety in your work. It is much esier to remove an eye or an arm than it is to replace it. Electric current can burn you, sparks can blind you heavy items can fall on you. Aything that spins has the potential for enormous kinetic energy, even light weight object can be lethal at high speed. Consider the 240 grain (about 1/2 ounce) pistol bullet very light and non lethal in your hand. The same object travelling at several hundred feet per second (a piece off your windmill blade) and suddenly it becomes lethal.

Batteries can be dangerous. Let me repeat, Batteries can be DANGEROUS.

Not only do they contain a fairly strong acid that can consume metal, clothing, eyes and flesh but when charging they produce a combination of oxygen and hydrogen in a good mixture of explosive gases. Keep flames, sparks, cigarettes, lighters, welders, etc well away from the batteries especially when they are charging . Provide plenty of ventilation. Wear eye, skin and clothing protection and flush any spills with plenty of water.

Batteries are able to put out an amazing amount of current [1000s of amps] instantly so keep metal objects well away from the terminals. In higher voltage systems like a 96 volt bank you could draw a spark across a quarter inch of airgap in the right circumstances. I have heard stories of wrenches getting across a big bank like that and the resulting short spewing molten lead from the battery terminals into the guys face and up the wall. Be very aware of this potential for destruction in high current sources, especially at higher voltages.

This document and any suggestions, plans or procedures are intended for adults and those without mental deficiencies that could cause errors in judgement where safety is concerned.

The most basic rule of troubleshooting:

Never assume a part or piece of test equipment is good, even if it is new and unused. Always test your meters, gauges, leads, connections and other components before you chase your tail looking for circuit problems. Miswiring is one big problem with the uninitiated. Always be certain of your connections to be sure that its wired properly and your connections are solid. Again never assume its wired right just check it with a clear head and don't rush it.

Even a brand new component can be bad. I like to test new components before I install them or at least before I energize a circuit. This simple step can avoid a cascade of damaged components from installing a bad component and energizing the circuit. It is also critical that you pay close attention to component lead markings and connect them properly. Misconnecting things can lead to circuit damage and weird problems that are confusing to the newbie. When you are using large battery banks the potential for destruction is immense. You can draw enough power from a large battery bank to instantly vaporize even fairly heavy copper cable and certainly kill things like diodes, inverters and controllers in an instant. It is very important that you pay attention and get help if you are unsure of how to connect something.

Basic test equipment needed is simply a volt-ohm-ammeter and I prefer analog [with a needle] because they need no battery to use except to read ohms [resistance]. These can be had new for about $15 or so US. Analog is nice for troubleshooting because you can see the meter move without looking directly at it. Digital meters are nice for precision comparison and can be used to troubleshoot I just prefer an old fashioned meter with a needle.

You can add other equipment as you go but a volt ohmeter will do for almost everything we do in this field. If you need to measure current [amps] you will need an ammeter. The ammeters in the volt-ohm meters usually measure less than 10 amps and you can kill them with excess current. For use in AE systems you can use automotive ammeters up to 60 Amps you can parallel a couple of identical meters to read higher current by taking the reading times 2. For high current feeding from batteries to an inverter or other large load you will need a current shunt with matching meter these can be had for reasonable prices on Ebay and from electronics supply houses and can read into the 1000's of amps and the meter can be located some distance from the point at which you read the current in the circuit. I have been using a 150 amp shunt with a matching meter I got off Ebay for about $25 delivered. You could home brew a shunt and add a meter but thats beyond the scope of this document.

Some basic facts about electricity:

E= Voltage [volts]

I = Amperes or amps [current]

R= ohms [resistance]

Regardless of the form electricity has [AC or DC] the 3 components we use to describe electricity have a mathematical relationship that can be expressed by the formula [E=I*R] or in English "Voltage equals Amps times Ohms". With a bit of high school algebra we can obtain the missing value once we know the other two. Another handy mathematical relationship for finding power either consumed or produced is Watts [P or Power] equals Volts times Amps. [P=I*E]. I have deliberately not included VA or Alternating current power relationships here its beyond the scope of this document. I will note that in an alternating current [A.C.] circuit the voltage and current are slightly out of phase with the amount of phase shift determined by the inductive and or capacitive characteristics of the circuit.

Well that was just some basic info to get you up to speed on that. Lets look at some common questions I have seen on the board with some solutions and how you can answer them yourself.

I have voltage at my mill but when I connect it to my diode or bridge rectifier I don't get any voltage to my batteries?

First. Be absolutely positive your connections are right to the bridge or diode. With a diode a reversed connection will block charging voltage/current and is not likely to damage the diode. With a bridge rectifier you can kill it by misconnecting it if your AC source [generator] has enough voltage and current available.

Assuming your connections are correct [because you meticulously checked] we can now start bugging out what may be wrong. I would start by disconnecting the batteries from the bridge or diodes and leaving the rest of the circuit intact.

With your meter set to DC range greater than your source [genny] voltage check the leads that feed the batteries. You should see DC voltage somewhere close to the source AC voltage but lower. Check for proper polarity on these leads by confirming that the + lead is indeed the + lead. If your meter tries to move backwards then polarity is reversed and no charging can occur. Reverse the leads to the battery leads if this is the case.

IF there is no voltage at the DC leads from the diode or bridge then you need to check the AC feeding into the bridge or diode to see if it is there. If the AC is on the input to the bridge or diode and you have low voltage or nothing on the output then it is likely your bridge or diode is bad. If so you need to replace it with a good one. But first see if the AC is present when not connected to the AC leads of the bridge to be certain it is not getting loaded down to zero by the bridge for some reason.

Testing diodes:

A diode is simply a one way valve for electricity. At least for our purposes. Most diodes will drop [use] about .7 volts across its leads when passing current. The most common failure modes of diodes is either shorted [passes the AC like a wire] or open [nothing gets through]. Occasionally a diode will test OK but fail under load so just because it tests OK does not mean it works under load.

Testing a diode is simple. You need an ohmeter. You simply set your ohmeter to its highest range and place one ohmeter lead on each lead of the diode. You should get a high reading in one direction and a low reading in the other direction. Please note that an ohmeter reads "backwards" and a low reading will deflect the meter more than a high reading. The actual numbers don't matter as long as one is significantly higher than the other. If the meter pegs both ways it is shorted. If the meter does not move either way it is open. To test the ohmeter short the leads together and the meter should peg to the right showing 0 ohms.

Testing bridge rectifiers:

Testing a bridge is a bit more difficult so I usually just give them a function test. Simply disconnect the + and - connections to the batteries and check for DC on those leads. If there is no DC on those leads then check the AC leads to see if the source voltage is present. As always be certain your meter is set to the proper function and range. If no AC is present try disconnecting the AC leads and check for voltage. If AC is present with the bridge disconnected the bridge may be shorted and loading the voltage down to zero. Before you replace the bridge try connecting a load to the AC lines a light bulb is a good choice but be certain it can handle the raw AC voltage level. If the AC source can light a bulb then your source is likely OK so replacing the bridge may cure the fault.

If the AC is present but no DC is available on the output it is a fair assumption that the diode or bridge is bad.

If everything is OK with the batteries disconnected but you get nothing when you connect the batteries you may have a bad battery bank or a diode / bridge that fails under load. Check to see that your batteries are capable of taking a charge and that they show at least some voltage at their terminals when disconnected from the charging source.

Series and Parallel circuit basics.

I have seen some confusion about how series and parallel circuits function. I'll try to clarify some of the main points. For simplicity I will not address reactive circuits [containing capacitors and inductors] but only talk about Direct Current resistive circuits.

A series circuit is comprised of components connected + to - to + to - in a string much like people holding hands around a circle. You end up with two ending leads one + and one -.

In a series circuit the total voltage will be the sum of the voltages connected. Total current will be equal to the lowest current rated source. This is because current in a series circuit is the same in all components.

In a parallel circuit we have components connected with all the + leads together and all the - leads together. Much like two people facing one another holding hands. with 12 Volt sources in parallel we would have 12 Volts output. The current [Amps] available would be the sum of all the sources.

Without special equipment or an elaborate switching arrangement you cannot charge a higher voltage battery bank with a lower voltage source. IE: you can't charge a 24 volt [or larger] bank with a 12 volt source. In order to achieve charging you must have a greater voltage from your source than the voltage of your storage batteries.