Electrokinetica The Electro-mechanical Museum

NO SMOKING! Battery test and charging area

Testing lead-acid batteries

One of the best ways to determine the condition of a lead acid battery is to monitor the change in density of the sulphuric acid electrolyte as the cell charges using a hydrometer. This gives an accurate indication of the mass of lead participating in the chemical reaction on which the energy storage depends. Another useful test when time is limited is the heavy-discharge test, which simulates operating conditions.

The heavy-discharge test

Heavy-discharge tester

Heavy-discharge tester

Otherwise known as a ‘drop test’, this imposes a load on the battery equivalent to the most severe it is likely to encounter in use. The voltage is shown on a meter, allowing the technician to watch the change in cell performance over the course of a few seconds. Most common cell faults will be revealed in one way or another, either by failing to deliver a satisfactory on-load voltage, or by gassing excessively. Care is required to avoid allowing the sparks which occur at the tester prods to ignite possible accumulations of hydrogen gas. Some testers are designed to test a 6-volt or 12-volt battery as a complete unit. Others, such as the tester shown here, are designed to test one 2-volt cell at a time, by which means batteries of any voltage can be tested so long as the inter-cell links are accessible to the test prods. On older designs of battery such as this, the individual cells are bonded into the outer case and then interconnected by sweating links onto the posts. Newer types and those for non-industrial applications tend to have concealed links.

Lift truck batteries being assessed

Here in the workshop are some 6-volt semi-traction batteries removed from one of our electric lift trucks. They were brought in because the machine was running low on power prematurely and one battery was found to have a crack in its case. We wanted to determine whether it, or any of the others, was still usable. They are 180 amp-hour semi-traction types designed for repeated deep discharge, of which three are shown here. The cell under test is performing fairly well, maintaining a constant 1.8 volts for as long as the tester is connected. During this time it is discharging at a rate of 180 amps, more than twice the current it is normally called upon to deliver in service. The tester in use is a Crypton product of the 1960s. Crypton, a major supplier of vehicle test equipment, was formerly known as Lancashire Dynamo & Crypto, a business that for many decades supplied a wide variety of battery charging and maintenance apparatus.

6-volt batteries

6-volt batteries

Tester dial

Tester dial

Reading voltage during test

Reading voltage during test

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