FS-5000 Batteries

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← FS-5000


FS-5000 Batteries

Rechargeable NiCd batteries

By default, the FS-5000 radio station is powered by two large rechargeable batteries that are both installed at the front left of the set. Although the radio station could also be powered by the PSU, battery operation was often mandatory. This is why the PSU-connector of the transmitter was often blocked by a plastic shield. The PSU was then used for charging the NiCd batteries.

The image on the right shows a typical pair of batteries as they were supplied with each FS-5000. Sometimes a spare set was supplied, so that one pair could be used to power the radio, whilst the other pair was being charged.

In order to protect against short-circuits, each battery is protected by a 10A slow-blow fuse that is located at the top. Nevertheless, a current of 10 Amps can cause serious damage to your equipment. Always be careful when connecting the batteries. A spare fuse is stored in a plastic compartment at the front side of each battery.

As part of normal battery maintenance, NiCd batteries have to be discharged and re-charged regularly in order to avoide the so-called Memory Effect (see below). Furthermore, NiCd batteries should never be fully discharged (deep discharge) as this could permanently damage them.

Once the batteries have been used and are exhausted, they should be further discharged using the supplied Slow Dischargers Marked with the letter 'S'). These are part of the Toolkit.

The slow dischargers have a green LED that shows that discharging is in progress. Once the LED is off, the battery is fully discharged. A special circuit inside the slow discharger, protects the battery against deep discharge.

Next, the batteries should be fully charged before they can be used with the FS-5000 again.

Note that NiCd batteries should always be charged when they are stored for a longer period of time. This is necessary to avoid a deep-discharge as a result of the batteries natural self-discharge. It is good practice to always discharge and charge the batteries after use.

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Recovery

Due to the nature of NiCd batteries, they might suffer from the so-called Storage Effect, also known as the Battery Effect. The effect is seen with batteries that have not been fully discharged before they are charged again, and with batteries that have been charged too long. The result is a battery that 'thinks' it is full, causing the charger to terminate before the battery is really full.

In this situation that battery gets a large internal resistance or Ri, that increases with each new charge job. Although the voltage is correct, it collapses as soon as a load is connected.

Batteries suffering from the Memory Effect can be 'repaired' by a repeated process of fast discharging and recharging, to the point where the battery is fully charged again and the Ri is decreased to a reasonable value. For this purpose, a special dummy load is supplied with each FS-5000 station. The image on the right shows the dummy load or Fast Discharger.

Once connected to a battery suffering from the efect, the green LED on top of the fast discharger is lit as long as discharging is in progress. If the battery is in a bad state, this will usually not take very long. A special circuit inside the discharger protects the battery against deep discharge. The nominal voltage of the battery is 14.4V. When the battery voltage drops below 12V, the fast discharger turns itself off and will not become active again until it has been disconnected.

Once the LED is off, leave some time for the battery to cool down (if necessary) and recharge it using the supplied battery charger (PSU). Once it is full, connect the fast discharger again and wait for the battery to be fully discharged. Repeat the above procudure a number of times until the battery shows normal behaviour again.

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Using the fast discharger to recover a NiCd battery

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Charging

There are two ways to charge the batteries. The default method is by charging them whilst they are installed as part of a complete radio station. Charging is started by pressing one of the charge buttons on the charger, which is part of the PSU-assembly. The FAST-button allows a battery to be charged in approx. 1 hour. Fast charging should only be used when in a hurry.

For normal charging, the button 10-HRS should be used. This will fully charge the batteries in approx. 10 hours. Slow charging is always better for the batteries and will extend their life.

The best way to treat the batteries is to charge them separately, away from the radio station. This can be done by using the PSU/Charger in combination with the H-bar as shown in the image on the right. If a spare set of batteries is available, one set can be used to power the FS-5000 whilst the other pair is being charged. This is the recommended mode of operation.

As the battery charger also contains a power-inverter, it is possible to charge the FS-5000 batteries from any 12V DC source, such as a car battery. The external 12V source should be connected to the black (-) and red (+) terminals of the charger.

➤ More about the charger


Alternative designs

The NiCd cells used with the FS-5000 had many disadvantages, such as memory-effect, self-discharge, bad impulse-response and short shelf-life. However, at the time the FS-5000 was developed (1985), alternatives were not available and NiCd was the only practical solution.

In later years, better battery cells and new technologies became available and alternatives were sought for the vulnerable NiCd cells.

One possible solution is the double-size battery shown on the right. It contains 2 x 6 LiMnO₂-cells by Hoppecke (model LSC 3460M), enough to produce 16.8V and a capacity of no less than 20Ah. It has a built-in self-restoring fuse, fits in the same space as the two standard NiCd batteries and can be locked in place as usual. It has only one connection to the radio. The unit shown here is probably a prototype [1].

It is uncertain whether this type of battery was actually taken into production. LiMnO₂ batteries have the disadvantage that they can not be recharged and need to be discarded after use. The solution presented here would therefore be rather expensive. Furthermore, no stocks of such batteries have been found to date. If you have one or more, please let us know (wanted item).

In 1994, the successor of the FS-5000, called the HRM-7000, was introduced with the German Bundeswehr (Army). As it was designed for field operations, it made use of the purpose-built BPU-7000 discardable LiMnO₂ battery, that is shown in the image on the right.

As this battery was produced in large quantities, it was adapted for use in combination with the FS-5000M, by means of a special cable.

➤ More information

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Technical Information

Each battery consists of 12 NiCd cells with a nominal voltage of 1.2V and a capacity of 1.1Ah. This gives a total voltage of 14.4V. As the radio is normally used with two batteries in parallel, the total capacity is 2.2Ah, which is enough for ½ hour of constant transmission. As the DSU transmits its messages as a very short burst of approx. 0.8 seconds, the batteries will last long enough for a full mission. Each battery has a special D-type connector with two large pins:

The two large pins are used for + (B) and - (A). Some of the smaller pins are used for monitoring the battery during charging. Two lines are used for a temperature-sensitive resistor (PTC) and one line is used to measure the ½ voltage. The circuit diagram is as follows:

The ½ voltage line (4) allows the battery charger to detect bad cells. With a good battery, this voltage should be half the nominal voltage. Quite often, when the quality of a battery deteriorates, a single cell dies first, causing the voltage in the middle to rise or to drop. This would then cause the LED marked 'BAD' on the battery charger to be lit.

The PTC is used to detect battery overheating whilst charging. It is enclosed in a silicone mold that fits nicely between the cells. The PTC has a nominal value of approx. 970 Ohm at ambient temperature (20°C), which rises if the temperature increases, and eventually triggers an alarm.

As most of the FS-5000 batteries were manufactured in the late 1980s, they are likely to be dead after all this time. Even when it seems possible to charge them, they may in fact already have started leaking internally.

The image on the right shows what can happen inside an old battery. The one shown here was manufactured in November 1987. Click the image for a closer look. Some of the battery's components have leaked-out, causing a chemical reaction that results in a build-up of toxic crystalline structures and dust.

The best thing to do under these circumstances, is to remove the battery cells and clean the case thoroughly. Once this is done, it should be relatively easy to replace the cells with modern alternatives. Although it seems tempting to replace the old NiCd-cells with modern Li-ION or LiPo batteries, this might not be a good idea, as such cells need a completely different power and charge management. It would probably be best to replace them with NiMh-cells, as they have the same cell-voltage (1.2V), behave similar to NiCd-cells and are less sensitive to mis-treatment.