fig1 shows a grid - tied solar energy system as described in the above - incorporated &# 39 ; 822 patent . solar combiner ( 700 ) combines selected strings of solar panels from array ( 1500 ) to produce a combined photovoltaic output current in photovoltaic output conductors ( 401 , 402 ) which , according to current national electrical code requirements , shall be contained in metallic conduit ( 400 ). the combined solar current is applied to dc to ac converter ( 2200 ) to generate a pure sinewave current at the grid frequency ( e . g . 60 hz ) which is fed back to the grid through breaker ( 4040 ) to offset power consumption consumed from the grid . assuming that dc - to - ac converter is configured to disallow grid power from being synchronously rectified and fed back up the photovoltaic output conductors towards combiner ( 700 ), there is only one source of power , that is the solar array . for the purpose of de - energizing the photovoltaic output conductors ( 401 , 402 ) when emergency service personnel are attending an incident at the property , this is guaranteed by switching off converter ( 2200 ), which in turn will operate the remote dc disconnect facility of combiner ( 700 ) by means of the control cable running between converter ( 2200 ) and control port 1 of combiner ( 700 ). the above operation is described and claimed in the above - incorporated applications . fig2 shows an alternative solar installation in which solar energy is used to change a battery ( 500 ). energy stored in the battery maybe extracted later or at the same time as charging to be converted to ac power by dc to ac converter ( 1000 ). dc to ac converter ( 1000 ) has the capability to power loads directly and so can power a home not connected to the grid , or when the grid is in outage . converter ( 1000 ) also preferably acts as a battery charge controller by monitoring battery state and controlling solar combiner ( 700 ) via the control cable to connect more or fewer solar strings through to charge the battery . fig3 illustrates the principle of combiner ( 700 ). the connector ( 711 ) for control port 1 carries current to the coils of relays ( 706 ), of which there is one per string to be combined . the return path for the current is through switch ( 709 ). switch ( 709 ) may be located on the combiner and accessible for manual operation , or may be a microswitch which opens of the front panel of the combiner is opened . when switch ( 709 ) is opened , all relays ( 706 ) and ( 7070 ) are de - energized so that no string is connected through either to photovoltaic output 1 ( 722 ) or output 2 ( 721 ). the same effect may be had by interrupting the relay coil return path at the converter , or by controlling all relays to be de - energized . if the converter supplies power to the relay coils only when operating , then switching off the converter will automatically de - energize the relays and thus de - energize the associated photovoltaic output circuit ( 721 or 722 ). thus the means to prevent the photovoltaic output circuit being energized by the solar panels is provided by the remote - controlled solar combiner ( 700 ). in fig2 however , the battery can still energize the photovoltaic output circuit conductors leading from the battery ( 500 ) to the combiner ( 700 ). to disable this source of energization also , additional components may be associated with the battery according to this invention , as shown in fig4 . fig4 shows a battery ( 501 ) contained in a battery enclosure ( 500 ). the battery enclosure ( 500 ) shall be vented to the outside air to prevent build up of hydrogen and battery odors . in fig4 , the connection from the battery to the load ( dc to ac converter 1000 ) is through circuit breaker ( 551 ) as opposed to the alternative of fuses ( 550 ) shown in fig2 . either overcurrent protection method is acceptable , but the use of a circuit breaker provides a more convenient manual means to disconnect the battery from the inverter that unplugging fuses . when the dc supply to converter ( 1000 ) is bipolar or floating , breaker ( 551 ) may be two - pole breaker ( as illustrated ), or may be a single pole breaker if one side of the dc is grounded . fuses ( 550 ) are still used in fig4 as in fig2 to protect the dc conductors ( 401 , 402 ) from overcurrent . the first additional component that is evident in fig4 compared to fig2 is diode ( 553 ). this prevents reverse current flow from the battery towards combiner ( 700 ) should anything unintentionally contact conductors ( 401 , 402 ). thus in principle , operating the remote disconnect facility of combiner ( 700 ) by means of appropriate signals on control cable ( 570 ) now de - energizes conductors ( 401 , 402 ) from both power power sources , the solar array and the battery . moreover , diode ( 553 ) if properly functioning ensures that fuses ( 55 ) should never blow , as reverse current cannot flow . however , semiconductor devices are known to fail in the short circuit condition and thus cannot be totally relied upon for overcurrent protection ; hence fuses ( 550 ) are still included . it is also desired to ensure that conductors ( 401 , 402 ) are able to be de - energized to a safe level even if diode ( 553 ) has failed short circuit or become leaky . thus the second new component in fig4 as compared to fig2 is controlled crowbar switch ( 552 ). switch ( 552 ) can for example comprise a pair of normally closed relay contacts that apply a short circuit between conductors ( 401 , 402 ) unless the relay is energized to open the contacts . the same control signal that energizes the relays in combiner ( 700 ) to apply power to conductors ( 401 , 402 ) can be used to energize switch ( 552 ) to open its contacts . in the absence of that control signal , combiner 700 will not supply array power to conductors ( 401 , 402 ) and control switch ( 552 ) will remain closed . if diode ( 553 ) has failed short circuit , one or both of fuses ( 550 ) will blow when switch ( 552 ) is closed . since this only happens when diode ( 553 ) is faulty , and that is expected to be a rare event , it is not expected that a high incidence of fuses ( 550 ) blowing will be encountered in service . moreover , since diode ( 553 ) failing and fuses ( 550 ) blowing will always occur together , they can be packaged together as a replaceable sub - assembly . in fig4 , controlled crowbar switch ( 552 ) is shown located at the battery . however , it could alternatively be located in solar combiner ( 700 ), or in both places . diode ( 553 ) passes all the of the solar array power , perhaps 40 amps at 125 volts in the case of a 5 kw system . the voltage drop of the diode lies in the 0 . 6 to 1 volt range , which represents a fractional power loss of 0 . 5 % to 0 . 8 %, but more significantly , involves heat dissipation of between 24 and 40 watts . to reduce the power loss and heat dissipation , an alternative to using diode ( 553 ) alone is to use a mosfet transistor having an intrinsic drain - source diode , the transistor being turned on to short out the diode drop under normal circumstances . such a circuit is shown in fig5 as second implementation . p - type mosfet 553 intrinsically comprises the diode 553 of fig4 . however , switch 552 is now a spdt relay that applies the negative of the battery through potential divided r 1 , r 2 to the gate of mosfet 553 when switch 552 is activated to remove the short from between conductors ( 401 , 402 ). this turns mosfet 553 on , thereby passing current from the solar array to the battery with a voltage drop less than that of the diode alone . for example , 10 p - type mosfet chips type fdms86263p in parallel will provide an on resistance of about 5 milliohms , giving 200 mv drop at 40 amps , and 8 watts of heat to be dissipated . since p - type mosfets do not have characteristics as good as n - type mosfets , fig6 shows a version of the invention using an n - type mosfet as the series switch . to derive fig6 from fig5 , it was merely necessary to interchange the polarity of the battery terminals and associated connections to the array and the inverter , and to select an n - type mosfet for series switch 553 , the intrinsic diode of which is now facing the other way . three n - type mosfets type fdp075n15a in parallel now provide an on resistance of about 2 . 5 milliohms and thus about 100 mv voltage drop at 40 amps , reducing the heat loss to 4 watts . of course if it is considered necessary to isolate both poles of the battery , a p - type series mosfet switch can be placed in the positive lead as per fig5 , while an n - type series mosfet switch is used in the negative lead , as per fig6 . the lowest voltage drop of all would likely be achieved by using a high current relay as a series switch in place of diode or diode / mosfet combination 553 . this is shown in fig7 . in fig7 , the high - current relay ( 554 ) can be of a lower cost type providing it is not required to open with current flowing through it . this may be ensured by timing the solar disconnect within solar combiner ( 700 ) to occur before relay ( 554 ) is commanded to open . another timing requirement is that switch ( 552 ) should not close before relay ( 554 ) is open , and it must open before relay ( 554 ) closes . a control circuit is therefore required to ensure these relative timings . an advantage of the simple diode circuit of fig5 is that no such timing constraints are required . in fig6 , the timing constraints are likewise simple , as mosfet series switch ( 553 ) is synchronized to switch ( 552 ) by the normally open contact of switch ( 552 ). however , for fig7 , more discussion of how to arrange for proper timing is required , which is explained with the aid of fig8 . in fig8 , crowbar switch 552 is a high current mosfet ( q 1 ). the requirements on q 1 dot not include very low loss resistance , unlike if it was used as a series switch . the requirement is merely that it should pass enough current to blow one of fuses ( 550 ) should it inadvertently be placed into conduction with switch 554 closed . the latter condition however is to be avoided by ensuring proper timing of the opening of switch ( 554 ) before switch ( 552 ) closes . moreover , switch ( 554 ) should not open before switches 706 or 707 ( as also depicted in fig3 ) have opened . fig8 shows that switches 706 or 707 ( also of fig3 ) are controlled by a relay driver ( 1100 ) which is envisaged to be part of inverter ( 1000 ), as described in the above - incorporated &# 39 ; 822 patent . there is a relay driver output for each relay ( 706 or 707 ) of remote controlled solar combiner ( 700 ), which are controlled as a means to control battery charging . fig8 is more general however than the envisaged solar application . fig8 presumes that there is a first power source on the left feeding current to a second power source on the right , and controlled switches ( 706 or 707 ) may be controlled by disabling the relevant relay driver ( 1100 to interrupt the current flow from the first power source to the second power source . it is also presumed that any steps necessary to shield switches ( 706 or 707 ) from sparking upon sudden current interruption have been taken at power source 1 end . it may be seen that switches ( 706 or 707 ) are opened by relay driver ( 1100 ) removing the ground return for power supply ( 1100 ) to switches ( 706 or 707 ) while leaving the power supply and ground connections to high current relay ( 554 ) intact . thus switches ( 706 or 707 ) may be controlled to open while leaving high - current relay ( 554 ) contacts closed , and then controlling power supply ( 1100 ) to be off removes the drive to the coil of high relay ( 554 ) so that its contacts open afterwards . it may be appreciated that high current relay ( 554 ) has little electrical stress , as it only ever opens and closes with zero current through its contacts . the only requirement is that it must be able to carry the maximum current from the first source to the second source when the contacts are closed , and it must have sufficient insulation resistance to isolate the conductors ( 401 , 402 ) form the voltage of the second source when the contacts are open . these requirements are typically met by low - cost relays designed for automotive use . in fig8 , choosing high current relay ( 554 ) to be a spdt relay allows the 235 normally closed contact to function as crowbar switch ( 552 ). since the relay cannot mechanically close the normally closed contact unless the normally open contact is opened , the probability of both contacts being closed and blowing fuses ( 550 ) is remote . in the above - incorporated &# 39 ; 882 patent , an inverter is described that uses a floating dc input of 120 volts nominal , and grounds the negative and the positive of the floating source alternately at 60 hz . when the positive is grounded , the negative conductor of source 1 and 2 will be at − 120 volts nominal . in that situation , it is not sufficient to open the positive connection between source 1 and source 2 using switch ( 554 ) to ensure de - energization of the conductors ; however , when the inverter as described in the &# 39 ; 882 patent is switched off , not only are neither the positive nor the negative of the source not grounded , but also the neutral output of the inverter is opened , as well as the live output , thus floating the inverter circuitry . thus part of the de - energization of conductors ( 401 , 402 ) in such an installation comprises switching off the inverter , which also switches off the power supply ( 1100 which is incorporated within it . with other loads of unspecified behavior however , a second high current relay similar to relay ( 554 ) can be placed in the negative lead so that both positive and negative conductors leading from the first power to the second power source are broken at both ends . it is also possible to contemplate a transistor such as a mosfet to function as crowbar switch ( 522 ) if it proves difficult to obtain spdt relays for switch ( 554 ). it is also possible to envisage a double pole relay ( 554 ) to open both the negative and positive conductors , and being also specially designed to apply a short circuit between the moving contacts when in the de - energized condition . the latter may be done internally so that no external connections are required to the normally closed contacts . if a mosfet transistor is used as crowbar switch ( 552 ), the switch must be on when everything else is off . therefore the voltage necessary to turn the gate on must come from an internal source , such as a charged capacitor . it is only necessary for the charge to be sufficient to keep the transistor operating as a crowbar switch long enough to blow fuses 550 if one of the series switches ( 554 ) has failed to open or diode ( 553 ) of fig4 has failed short circuit . it may also be mentioned that fuses ( 55 ) may be replaced by a suitable circuit breaker or any other suitable overcurrent protection device . resettable circuit breakers are most appropriate if frequent tripping is expected , but if the not the case , then fuses may be the lower cost choice . all of the above variations are deemed to fall within the scope and spirit of the invention as described by the attached claims