Showing posts with label solar. Show all posts
Showing posts with label solar. Show all posts
Thursday, 11 April 2013
Solar Powered SLA Battery Maintenance
This circuit was designed to ‘baby-sit’ SLA (sealed lead-acid or ‘gel’) batteries using freely available solar power. SLA batteries suffer from relatively high internal energy loss which is not normally a problem until you go on holidays and disconnect them from their trickle current charger. In some cases, the absence of trickle charging current may cause SLA batteries to go completely flat within a few weeks. The circuit shown here is intended to prevent this from happening. Two 3-volt solar panels, each shunted by a diode to bypass them when no electricity is generated, power a MAX762 step-up voltage converter IC.
Solar Powered SLA Battery Maintenance Circuit Diagram
The ‘762 is the 15-volt-out version of the perhaps more familiar MAX761 (12 V out) and is used here to boost 6 V to 15 V.C1 and C2 are decoupling capacitors that suppress high and low frequency spurious components produced by the switch-mode regulator IC. Using Schottky diode D3, energy is stored in inductor L1 in the form of a magnetic field. When pin 7 of IC1 is open-circuited by the internal switching signal, the stored energy is diverted to the 15-volt output of the circuit. The V+ (sense) input of the MAX762, pin 8, is used to maintain the output voltage at 15 V. C4 and C5 serve to keep the ripple on the output voltage as small as possible. R1, LED D4 and pushbutton S1 allow you to check the presence of the 15-V output voltage.
D5 and D6 reduce the 15-volts to about 13.6 V which is a frequently quoted nominal standby trickle charging voltage for SLA batteries. This corresponds well with the IC’s maximum, internally limited, output current of about 120 mA. The value of inductor L1 is not critical — 22 µH or 47 µH will also work fine. The coil has to be rated at 1 A though in view of the peak current through it. The switching frequency is about 300 kHz. A suggestion for a practical coil is type M from the WEPD series supplied by Würth (www.we-online.com). Remarkably, Würth supply one-off inductors to individual customers. At the time of writing, it was possible, under certain conditions, to obtain samples, or order small quantities, of the MAX762 IC through the Maxim website at www.maxim-ic.com.
Sunday, 7 April 2013
XW Solar Panel wiring diagram
While the other is an 80 amp single circuit panel mount device. OutBack Power offers a two circuit 80 amp panel mount DC-GFP that also fits inside the E-Panel. The Xantrex DC-GFP’s will not fit in the E-Panel. The MidNite Solar single circuit DC-GFP’s are designed for a single PV array. Two MidNite DC-GFP’s may be used to accommodate two arrays although the dual OutBack would for dual arrays and dual controllers cost less and take up less room. DC-GFP’s are a very misunderstood device. When looking at a wiring diagram you will notice that part of the DC-GFP is a high current breaker. Connected in series with the GFP is yet another high current DC breaker. It is a common mistake to think the second breaker is unnecessary. NEC2008 requires a DC-GFP on all systems whether mounted on the roof top of a residence or not. The NEC also does not allow the DC-GFP to be the PV disconnect. When the DC-GFP is turned off, it leaves the battery negative ungrounded. The only time it is allowed that the system be ungrounded is during a fault condition. This requirement necessitates a PV disconnect in series with the DC-GFP.
Thursday, 4 April 2013
Lead Acid Battery Regulator For Solar Panel Systems
The design of solar panel systems with a (lead-acid) buffer battery is normally such that the battery is charged even when there is not much sunshine. This means, however, that when there is plenty of sunshine, a regulator is needed to prevent the battery from being overcharged. Such controls usually arrange for the superfluous energy to be dissipated in a shunt resistance or simply for the solar panels to be short-circuited. It is, of course, an unsatisfactory situation when the energy derived from a very expensive system can, after all , not be used to the full. The circuit presented diverts the energy from the solar panel when the battery is fully charged to another user, for instance, a 12V ice box with Peltier elements, a pump for drawing water from a rain butt, or a 12V ventilator.
It is, of course, also possible to arrange for a second battery to be charged by the super-fluous energy. In this case, however, care must be taken to ensure that when the second battery is also fully charged , there is also a control to divert the superfluous energy. The shunt resistance needed to dissipate the superfluous energy must be capable of absorbing the total power of the panel, that is, in case of a 100W panel, its rating must be also 100 W. This means a current of some 6–8 A when the operating voltage is 12 V. When the voltage drops below the maximum charging voltage of 14.4V growing to reduced sunshine, the shunt resistance is disconnected by an n-channel power field effect transistor (FET), T1.
Circuit diagram:
The disconnect point is not affected by large temperature fluctuations because of a reference voltage provided by IC1. The necessary comparator is IC2, which owing to R9 has a small hysteresis voltage of 0.5V. Capacitor C5 ensures a relatively slow switching process, although the FET is already reacting slowly owing to C4. The gradual switching prevents spurious radiation caused by steep edges of the switched voltage and also limits the starting current of a motor (of a possible ventilator). Finally, it prevents switching losses in the FET that might reach 25W, which would m a ke a heat sink unavoidable. Setting up of the circuit is fairly simple. Start by turning P1 so that its wiper is connected to R5.
When the battery reaches the voltage at which it will be switched off, that is, 13.8 – 14.4V, adjust P1 slowly until the output of comparator I C2 changes from low to high, which causes the load across T1 to be switched in. Potentiometer P1 is best a 10-turn model. When the control is switched on for the first time, it takes about 2 seconds for the electrolytic capacitors to be charged. During this time, the output of the comparator is high, so that the load across T1 is briefly switched in. In case T1 has to switch in low-resistance loads, the BUZ11 may be replaced by an IRF44, which can handle twice as much power (150 W) and has an on-resistance of only 24 mR. Because of the very high currents if the battery were short-circuited, it is advisable to insert a suitable fuse in the line to the regulator. The circuit draws a current of only 2 mA in the quiescent state and not more than 10 mA when T1 is on.
Read More..
It is, of course, also possible to arrange for a second battery to be charged by the super-fluous energy. In this case, however, care must be taken to ensure that when the second battery is also fully charged , there is also a control to divert the superfluous energy. The shunt resistance needed to dissipate the superfluous energy must be capable of absorbing the total power of the panel, that is, in case of a 100W panel, its rating must be also 100 W. This means a current of some 6–8 A when the operating voltage is 12 V. When the voltage drops below the maximum charging voltage of 14.4V growing to reduced sunshine, the shunt resistance is disconnected by an n-channel power field effect transistor (FET), T1.
Circuit diagram:
Lead-Acid-Battery Regulator Circuit Diagram For Solar Panel Systems
The disconnect point is not affected by large temperature fluctuations because of a reference voltage provided by IC1. The necessary comparator is IC2, which owing to R9 has a small hysteresis voltage of 0.5V. Capacitor C5 ensures a relatively slow switching process, although the FET is already reacting slowly owing to C4. The gradual switching prevents spurious radiation caused by steep edges of the switched voltage and also limits the starting current of a motor (of a possible ventilator). Finally, it prevents switching losses in the FET that might reach 25W, which would m a ke a heat sink unavoidable. Setting up of the circuit is fairly simple. Start by turning P1 so that its wiper is connected to R5.
When the battery reaches the voltage at which it will be switched off, that is, 13.8 – 14.4V, adjust P1 slowly until the output of comparator I C2 changes from low to high, which causes the load across T1 to be switched in. Potentiometer P1 is best a 10-turn model. When the control is switched on for the first time, it takes about 2 seconds for the electrolytic capacitors to be charged. During this time, the output of the comparator is high, so that the load across T1 is briefly switched in. In case T1 has to switch in low-resistance loads, the BUZ11 may be replaced by an IRF44, which can handle twice as much power (150 W) and has an on-resistance of only 24 mR. Because of the very high currents if the battery were short-circuited, it is advisable to insert a suitable fuse in the line to the regulator. The circuit draws a current of only 2 mA in the quiescent state and not more than 10 mA when T1 is on.
Subscribe to:
Posts (Atom)
