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Details about  Lead acid battery capacity tester DC load 40V 40A wind power generator

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Lead acid battery capacity tester DC load 40V 40A wind power generator
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Item condition:
27 Feb, 2012 19:21:25 GMT
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Item location:
Grantham, Lincolnshire, United Kingdom


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Item specifics

Used: An item that has been previously used. The item may have some signs of cosmetic wear, but is fully ... Read moreabout the condition
This is a Richmond Electronics Battery Capacity Tester chassis only, no 19" case supplied.

Designed to load test a battery to determine its real amp hour, Ah, capacity. Typically as used in any wind power type of alternative energy. The inverters are run from the batteries with the wind turbine charging as and when it can.

A lead acid battery has its capacity rated at so many Ah at, usually, an 8 hour rate. So 100Ah will supply 12.5A for 8 hours with the end point voltage per cell being 1.8V. This type of capacity rest is really the only way to test a battery. As a battery ages its capacity slowly drops and whilst it will still provide a very high current for short periods the battery is still not 100%.

This is a flexible battery capacity tester with three voltage ranges, 2V, 20V and 40V, and a stepless variable load current. The ammeter is marked to 50A but the internal fuse is set to 42A.

The 2V battery voltage is specifically for the NiFe cells used in various low ohm testers and is, in this application, of no real use. The additional circuits have been removed to save on shipping weight.

The 20V setting is convenient for 12V batteries and the 40V setting for 24V batteries.

The voltage set control is a 10 turn potentiometer and spans the whole 0-40V range, so there is no real constraint on the battery voltage, 6V can be tested as easily as 12V.

Similarly the current set control is also a 10 turn potentiometer giving a smooth adjustment of the load current up to 40A.

The battery capacity is recorded on a five digit counter. This counts at the rate of 1000 counts per hour. So, with a good battery and correct load current this should indicate 8000 when the low voltage detect trips. This counter is marked as 'Capacity %' which puzzles me, measures time, not percentages provided you are loading the battery at its 8 hour rating.

In operation the voltage control is set to the battery end point voltage, the battery connected, start pressed and the load current adjusted to the 8 hour rating value. You then leave it to load the battery until the voltage trip stops the test and read the time of the test on the counter.

This particular version of the capacity tester has potentiometer setting of the end point voltage. This needs to be calibrated before the tests are meaningful. The easiest way to do this is using a variable DC power supply set to the end point voltage connected to the battery terminals. The variable voltage end point control is set higher than the end voltage, start is pressed so the counter counts and then the end voltage slowly reduced until the tester trips out. The current drawn from the power supply can be very small, I have used a simple 1A bench power supply. Normally a battery bank consists of just one voltage of batteries, either 6V or 12V, so once set can be locked and left.

A test should take about 8 hours to run, quite slow. If you have detailed specification on your batteries then you might be able to run the test at a higher current and so shorten the test time. For example loading the battery at at 8 times the 8 hour rate will result in a test time of about 30 minutes. At these very high discharge rates the effective capacity of the battery will drop, ususlly to half, or less, of the 8 hour rate. This is why you need the manufacturers details so you will know what to expect. Alternatively, if you have lots of the same battery then just a comparison between them might do. If at a one hour rate the battery lasts 20 minutes then all should last 20 minutes, one battery lasting 5 minutes is obviously dying.

This battery tester is nothing more than a large collection of transistors acting as a variable resistance. As such it has many other loading type applications than testing batteries, power supplies is the obvious alternative, but also voltage drops in low voltage high current power distribution in electronics cabinets etc. The actual load consists of 24 2N3442 transistors. So at 40V and 48A each transistor is dissipating 80W, this might be rather more than it can cope with. To prevent the voltage trip working it is simply adjusted to maximum.

There seems some confusion about this tester and the many others available that are rated at 100A or even more. This tester is continually rated, the tiny little 100A types are basically a flash tester, more than a few seconds and it will catch fire.

This load tester in its case is heavy, 34kg, and very large making it very expensive to get delivered. The supplied 19" chassis weighs about 14kg, the 2V NiFe test has been removied making delivery much easier. In the cabinet bottom are a pair of fans to cool the heatsink, these would probably need to be added, depends on what load currents you want to use.

In summary this is either a pretty essential piece of battery bank test gear, or a useful low voltage variable DC load tester. Whilst these are nothing more than a pile of power transistors, here all the work is done for you. Could use as is, or modify to meet your requirements.

Unpacked weight is 14kg so can be sent by parcel post, this would cost £24 including packing. Collection is an option.



I have several of these testers, so if you want more than one let me know. This auction is for just one tester. Due to their size, a 19" rack cabinet, they are in storage so would need s few days to get them home. If you want one of the complete testers in cabinet and with the 2V setting then let me know, but collection is the only economic way.

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BW Electronics

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