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Yes its possible, often forklift chargers contains big transformer several KW, with big and heavy cores. This system is indestructible compared with SMPS. Switcher charger will be smaller and lighter, but design and construction will be more expensive to produce.
Recently I saw few used big transformers from forklift for 40-50eur (EI core and copper wires).
Yes its possible, often forklift chargers contains big transformer several KW, with big and heavy cores. This system is indestructible compared with SMPS. Switcher charger will be smaller and lighter, but design and construction will be more expensive to produce.
I would say that SMPS would be cheaper to produce. The mains transformers are quite expensive and could cost more than the entire SMPS itself, without the cost of rectifiers, etc. taken into consideration.
However, the SMPS ones will be be more complicated to design and won't be as long-lasting and heavy-duty as the mains transformer-based ones.
This depends from size of forklift and his battery bank size, but can be from 24V, 48V, 72V (what I saw).
I didnt saw any SMPS charger for forklift in usage. SMPS cant be reliable as real transformer. Transformer is multi generation device, almost indestructible, unlike SMPS which will be in problems often. I know that power SMPS exist as forklift chargers, but transformer is transformer. :wink:
Forklift is industrial venhicle and size of SMPS dont have some role compared with transformer charging station. Industrial devices should be reliable.
In this case to charge 12v 800AH.At charging rate of 80AH,transformer output votage will be 16-0-16v. With battery monitor.Or the transformer design will be two set of 14-0-14. Without battery monitor the cells is save
In this case to charge 12v 800AH.At charging rate of 80AH,transformer output votage will be 16-0-16v. With battery monitor.Or the transformer design will be two set of 14-0-14. Without battery monitor the cells is save
Whatever the transformer output voltage, it must be rectified, filtered and regulated to give between 13.5V to 14.5V output. Adjust charging voltage to adjust charging current. If you charge the battery at 13.5V, no current monitor is required, as the battery is "float" charged. However, charging will be slow. For higher charging voltages, a monitor is required to reduce charging voltage (and current) when battery is near fully charged. A charging current monitor should also be used to prevent charging with excessive voltage. In some chargers, charging is terminated when the battery reaches a certain voltage.
Thanks Tpetar/Tahmid.To charge the 800Ah,we need centre taps transformer,16-0-16v (reason-to reduce charging voltage) .After the .rectifier/filter than parallel the output =80A(16-0=40A,0-16 =40A).Yes using 13.5v no battery monitor because once the charging voltage is equall to battery voltage the charging current is equall to zero at that time the battery will stop charging. 13v at rate of 10A,13.5v at rate of 15A,14v at rate of 20A,15v at rate of 30A,16v at rate of 40A 17v at rate of 50A,18v at rate of 60A.I design this charger after one week the charger get burnt .I use 5kva auto transformer lamination E type .Transformer data:swg 12 and swg18.5.emf per turn 1v,E2=16V,E1=(16-0-16) 220v.I'm going try it with 3pcs of 5kva laminations and increase the size of conductor,3 set of (13.5-0-13.5v) .Pls help with conductor. selection calculation.
You must limit current, because battery bank will drain more current and transformer will be burned. Internal resistance of discharged battery is very low, and you will have in circuit on start very high current, you must limit current.
Use transformer with primar and secundar not auto transformer. Autotransformer can be used, but look to use complete transformer always when this is possible. Regulation of voltage and current with autotransformer is also easy.
For current limit of such higher currents, we can use method similar in transformer welding devices, to use primar with multi-tap. Better to regulate current on primar because there si lower current. Some circuit will switch between transformer taps, according to needed voltage and current.
You can use center taped transformer only because usage of two diodes for rectification, and secundar should be winded bifilar. Also you can use standard transformer secundar without center tap, but in this case you need bridge rectifier (Graetz).
For higher current also consider usage of three phase system transformer.
No no, the 5kva I'm talking about is not the auto transformer itself it is the iron core(laminations).I will combine three of it and design a former that will size the three .
Yes, it should be iron core (laminated). Look quality of transformer! Each laminat should be isolated with thin layer of laquier. Look wires isolation, it should be very good (multi-layer laquier + special insulating fabrics on wires). Copper wires not aluminium. Good made transformers when assembled at full load, should not have noise caused by magnetostricion.
Use some thermal protection for windings to protect windings wires. At high temp this will turn off transformer.
For copper wires calc use max 2,5A/mm².
Some raw calc for EI core (inner core section 75mm x 100mm) around 5,6KW, primary windings should have (220V) 150 turns of 2,15mm diameter wire, and secundar winding should have 12 turns of 7mm diameter wire, for 100A of current. The iron core will be saturated with around 40% at full load, which is good, you will get lower temperature. Also because you use bigger EI core, you have more space for wire isolations.
You need only one secundar 18V-0-18V, and you dont need three secundars. Current and voltage are regulated on primary side.
Also use strong rectification diodes, always more stronger then is needed. Mount diodes on good heatsink, and ensure good ventilation of device internal parts, maybe additional FAN as support.
It does not hurt to add voltage and current meter of secundar section, with temperature of transformer windings, all on separated 7-seg LED displays on device case. Current can be measured with CT (Current transformer) or Hall sensor.
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