Power supply, battery and charger

Even the best radio station won′t work without power. That′s why you′ll find power supplies for stationary use on this page, as well as rechargeable batteries and suitable chargers.

Main power supply
 
For the power supply on the station table, I bought back in 1998 the Voltcraft FPS 4A, a commercial device from Conrad Electronic www.conrad.de. It dispenses 2 A at 13.8 V, for a short time 4 A are possible. When opening the case, the output voltage of 12 to 14 V can be adjusted via a setting resistance on the vertical circuit board. Since its purchase more than 20 years ago, this power supply has worked without failure.

Conrad Electronic www.conrad.de also had the follower model Voltcraft FPS-1132 (Order no. 1195956). Compared to the Voltcraft FPS 4A, it provides a measuring device for displaying the output current. In addition, the fine-tuning of the output voltage (11 to 14 V) is possible via a small adjustment resistance from the front panel. This device can also dispense 2 A and 4 A for 2 minutes.

The laboratory power supply Statron 2225.2 by Statron is also available from Conrad Electronic (order no. 1400037). It has 2 galvanically isolated outputs, whose output voltages can be set independently from 0 to 24 V. Each output has a current limit that can be set from 0 to 6 A. The device works as a linear regulator. It is short-circuit proof and has a fan. The output currents and output voltages of each output are shown on an LC display. The outputs can be connected in parallel or in series, so that up to 48 V or up to 12 A are available.

Sealed lead-acid technology
 
At the latest if one wants to become active away from the commercial power supply, the search for an alternative power supply begins. Although there are various battery types and high performance one-way solutions, I use mainly Sealed lead-acid batteries. If one calculate the necessary capacity, astonishing small types can be used. They are usable over years if still suitable charge methods and fundamental usage hints are used.

I was in search of a small and lightweight charger for my sealed lead-acid batteries. It′s should work at 110 and 230 V and have a current limiting. Unfortunately I do not found an usable one so I modified the output voltage of an available power supplies by Egston Mainy. A description of the conversion is available.

NiMH technology
 
During the preparations for a portable operation I make up my mind not to use my sealed lead-acid batteries. For a long time I ogle with Varta NiMH batteries. They are ligther and smaller than comparable sealed lead-acid batteries. But the offer is enormous. The batteries are available both as single cells and as acumulator packs.
Finally I opt for single Mignon cells (AA) by Varta, which are usuable for high-current applications (not the normal ones). They possess a capacity of 2.7 Ah with 1,2 V for each cell. For a transceiver operated with 12 V are ten cells to be used. You can unload the cells with up to 4.8 A (4.8 A) and down to 0.8 V. Thus a transceiver can be operated down to 8 V.
The used cells (four-pack, order no. 250484) and suitable holder (Order no. 615617) are available by Conrad Electronic. For charging I use a ready-made charger for NiMH batteries (Mignon, AA). The also as four-pack available cells (Order no. 250992) have only 2.6 Ah, but they can also be discharged with 5.2 A down to 0.8 V.
Two tips: Buy as much cells as you need for two battery packs. While a package of ten cells is loading, you can use the second package. Also replace the thin wires of the related clips with thicker wires. How to do this, I′ll show here.

There I stood now with my 10 NiMH batteries. I own a suitable charger, but it can charge only 2 cells at the same time. Devices, which charge 4 cells one finds many, such for 8 cells already less. I found only one charger, which can charge at least 10 cells at the same time. It is the Basetech BTL-12, which is for example available from Conrad Electronic (Order no. 200112).
The newer version Basetech BTL-14 with display is also available from Conrad Electronic (Order no. 1541355). I selected consciously a device, that don′t uses high-speed charging. It charges the cells with 250 mA (trickle charging current 25 mA). The charge process takes longer (approximately 15 hours in relation to 3 or 4 hours with fast charging), but the cells are take care in such a way. To emphasize is, that the Basetech BTL-12 and the Basetech BTL-14 supervises each cell separately and the device uses the so called -ΔV disconnection. The chargers can be runs as well with the power adaptor from 100 to 240 V, the BTL-12 additional with an adaptor cable from the 12 V car.
BTL-12: 22,3 × 3,4 × 9,8 cm; 217 g
BTL-14: 22,3 × 3 × 10,6 cm; 140 g
Addendum of 10.5.2020: After the BTL-12 has been replaced by the BTL-14, also the BTL-14 is no longer available from Conrad Electronic.

LiFePo4 technology
 
After almost 15 years of service, the sealed lead-acid batteries I used did not replace fancy specimens with new ones, but looked for a lighter alternative.
I′ve been using LiFePo4 batteries for a few years now. They are available now reasonably priced as battery packs with 13.2 V rated voltage. If you do not want to use balancers when charging, you should make sure that a so-called Battery Management System (BMS) is already integrated in the battery. This control takes over the balance of the 4 cells contained therein.
In addition, care must be taken to ensure that the maximum permissible discharge current is lower than the current of the transceiver when sending. Otherwise, the BMS can be damaged if the current is too high.
If you calculate the necessary minimum capacity before buying one, surprisingly small batteries can be used.
The 3 LiFoPo4 batteries I use are:
- JuBaTec JB-LFP12-3C; 13,2 V/3 Ah, 440 g; 80 × 70 × 38 mm
- Vision V-LFP-12-4.5; 13,2 V/4,5 Ah; 660 g; 114 × 80 × 40 mm
- BMZ Lithium Powerbloc LPB-S 2,5Ah; 13,2 V/2,5 Ah; 530 g; 90 × 101 × 70 mm
I built a charger that can be used for these LiFePo4 batteries from a plug-in power supply Egston N2EFSW3-12 and another from a Voltcraft SPS24-24W-A. There is also a suitable charger at JuBaTec.

I needed a charger for a LiFePo4 battery whose output voltage is exactly 14.4 V and whose has a current limit. A balancer was not required because it is already included in the batteries. I used a switching power supply Egston N2EFSW3-12W here again, as I had already used it years ago with the charger for sealead lead gel batteries. The output voltage and the current limit are relatively easy to adjust. There are only two resistances to be changed. Which resistors are to be changed where can be found in this conversion manual.

Since the maximum charging current of the Egston N2EFSW3-12W power supply converted into a charger for LiFePo4 batteries is limited, I was looking for a more powerful model that is as easy to convert as possible. And I found a suitable plug-in power supply, namely the Voltcraft SPS24-24W-A. Its output voltage can be changed by a resistor in a jumper, so that no further modifications are required. Which resistors are to be changed, to reach an output voltage of exatly 14.4 V, where can be found in this conversion manual.