Saving a 12-year forklift battery

Background: the pallet truck was not in operation for a long time, and when needed, it could not go anywhere. So the battery came to us.

A huge plus is that the client did not try to "restore" the battery by adding water from the tap, acid or other "wonderful" liquid there. Some of our customers do just that - and it’s most often impossible to restore the battery after such “self-treatment”.





For the time of service, we remove the auto-filling system, replace it with ordinary traffic jams.

Generally speaking, an auto-fill system is not always good. As a rule, customers who have installed it on the equipment believe that the system is sinless, works like a clock, and all their problems with topping are permanently resolved. This is not so: we tested similar systems several times, and almost every one contained a valve that did not open at normal pressure for the system - which means that the water simply did not reach the element. In the future, the absence of topping up water in one of the elements leads to its deterioration: the spread in internal resistance among the elements increases, and at some point it is completely pointless to service the entire battery - it is necessary to work with problem elements separately.

REGULARLY CHECK the autofill systems installed on your equipment, or remove them altogether and add water yourself.

We remove the jumpers, clean the terminals (in our case, we had to go through a milling cutter) and measure the characteristics of the elements:





As you can see from the histograms, the battery is unbalanced - you can immediately see the spread in voltage and resistance. Some elements have resistance values ​​that are thousands of times higher than nominal ... Add distilled water - all elements are dry.

Considering that the internal resistance is hundreds (or even thousands) times higher than the normal value, after topping up the water, we waited, then connected all the elements in series and put on a charge with a small current - if we do not see positive changes, then it’s simple to continue working on this battery pointless. Please note - the asymmetric current (discharge part of the pulse) in the first stage is turned off.



Several times, the activator automatically shuts off due to battery heating ...







... Several restarts - and the whole cycle went fine. Probably, sulfate collapsed in the process, due to which the battery was heated.



Again we measure the characteristics of the elements:



Already something, but far from ideal. The maximum variation in resistance is 19% (ideally, it should be no more than 10%).

There is definitely a point in doing battery. We are continuing the recovery.

At this stage, it is necessary to work with the elements separately, but it is permissible to include them sequentially if their characteristics are close to each other. The activator allows you to work with different voltage levels - you can service the entire battery, as well as each specific element. Or, for example, two elements connected in series.

Considering that elements 2 and 3 have similar characteristics and are nearby (it will be convenient to connect them with a standard jumper), we will serve them together. In addition to them, elements 5, 7 and 11 should also be serviced - but individually, without connecting.

We connect in series elements 2 and 3; connect element 11 to another activator:



Maintenance program for elements 2 and 3 connected in series:



Maintenance program for element 11:



Maintenance program for element 5:



Maintenance program for element 7:


Important remark: as a rule, to save time and, more importantly, not to expose already seen types of batteries to a relatively deep discharge , when working with 12 V batteries, we we discharge them up to 11.1 V, and not up to 10.5 V specified in the standards (however, if our customers need selective control of the batteries received from the supplier / manufacturer, we discharge the batteries up to 10.5 V).

When working with 2 V elements, to save time (and discharge / charge cycles), we discharge to 1.85 V instead of 1.75 V. If you see that the voltage during the discharge is SMALL (with a relatively constant slope of the curve) decreases to 1.85 In, then, guided by experience, we assume that the capacitance at discharge to a voltage of 1.75 V / cell would be 10-15% higher.

Again, we measure the characteristics:



Now the spread in resistance is only 9%.

As practice shows, if the battery is initially of good quality and the client was not self-medicating, even very old batteries can be saved.

And the client will save - servicing a battery is much cheaper than buying a new one.