Svenska RSS

No part of charging is so fast that there would be any advantage to HF technology, with its >100 kHz switch frequency, over 50 Hz. The fastest charging process that has been requested from Micropower is in charging batteries for automatically guided vehicles (AGV’s). We have made chargers that are only connected to the battery 5 seconds at a time. That requires a 0.2-0.5 second start and stop processes, and we have handled this fine with 50 Hz technology.

This resembles the argument some charger manufacturers use. Micropower has tested pulse charging and compared it to low-current charging.
In our tests, we have not seen that pulse charging would be better than low-current charging. What we have found are definite advantages in dissolving lead sulphate using low current.

“Pulse charging” can be done with both 50 Hz and HF technology. When Micropower talks about “pulse charging”, we mean “pulses” of 1-2 minutes, while for example some charger manufacturers speak of milliseconds. Micropower has tested charging with different types of pulsing and the only type we consider good is when you can stir the acid at even intervals with extra high current for 1-2 minutes in order to shorten charging time without risk of battery stratification. Micropower’s MTM and MTM-HF charger types are equipped with real-time clocks, and with these, entirely customised charging can be done on a weekly basis. You can, for example, charge using a charging factor of 1.05 on weekdays and charge once during the weekend at 1.25 and low current for 10 hours to dissolve any sulphating. This way you can charge as quickly as with mechanical acid circulation and avoid the disadvantages of hoses and couplings that have to work.

This is a very serious generalisation when comparing chargers. Micropower has some 50 Hz chargers that have an average efficiency coefficient of over 93% (e.g. the BTM 80/150). We also have HF chargers with an efficiency coefficient of 86% (the SMC 12/30). We have focused on optimising the total cost for the battery and charger system. A charger is often connected to a battery over 6000 hours a year, so efficiency is important even in trickle charging. If you are looking to keep energy costs down, it is important that charger shutdown is performed correctly. If overcharging necessary to acid stirring etc. is 20 % instead of 15 %, energy cost is immediately 5 % too high, which corresponds to 5 % charger efficiency.

Some HF chargers have sinus boosters, a circuit on the primary side that controls the primary current so that it becomes sinus-shaped and is in phase with mains voltage. These can be sometimes be protected with a lower fuse than 50 Hz chargers, which have a phase shift between current and voltage and thus also use reactive power. Depending on how great the reactive power is, sometimes a larger mains fuse must be chosen.
The energy required by the charger depends only on the active power component.
HF chargers without sinus boosters sometimes need a larger fuse than corresponding 50 Hz chargers because they top charge an intermediate capacitor.

This is an argument that is almost always correct. Micropower has always used toroid core transformers in their 50 Hz chargers thus been able to build comparatively compact, light devices. But with proper HF technology, equivalent HF chargers are much smaller and lighter. Micropower has used the latest technology to build the HF’s and has smallest and lightest design in the market.

Our recommendation is to charge the battery every day it is used. All chargers that Micropower has manufactured since the start 20 years ago take into consideration the battery’s degree of discharge and make sure gassing takes place for as short a time as possible, yet long enough time for sufficient acid stirring (gassing) in the battery. For valve-regulated batteries there are special chargers that in the final phase of charging lower the current so much that the overpressure in the battery does not open the valves releasing gas, which would make the battery dry out. These types of batteries must never be charged with simple unregulated chargers, since the battery could be ruined in a couple of weeks.

Yes, if the battery cannot handle a full day’s work, it is better to charge intermittently once or twice than to deep-charge the battery. For the longest battery life, no more than 80% of its capacity should be used.

If interference elimination has not been carried out properly, both HF and 50 Hz batteries can interfere with their surroundings and themselves be interfered with. Since there is a great amount of electronic equipment in every workplace, there are nowadays quite strict rules on what kind of interference an electronic device can generate and what it must withstand. Micropower has calculated that the cost of interference elimination represents over 20% of the price of the charger in the case of HF technology. For 50 Hz it is considerably lower and much easier to do. There still exist certain less scrupulous charger suppliers who do not comply with applicable legislation and regulations, so our recommendation is that the charger be tested at its most sensitive spot before a larger HF charger is bought.
The smaller chargers have long been able to be integrated into trucks, so as a rule they are well protected from interference.