Relay in Solar Panel

Hello. Am currently trying to build a gokart ( school project ) which would run on solar power when its sunny and automatically switch to battery power when its cloudy. I figured a relay would be my best. The problem is taht the solar panel and battery, both are 24V while the DPDT relay im looking at is 12V. How do I goet around this problem? Would connecting them in series solve the problem? Although when the power passes through the first relay coil, its gonna be at 24V, more than what the coil can handle so not sure if series helps a whole lot. Any ideas? Thanks much.

get a 24vDC relay and connect ter#30 to cart 87 to batt.  87a and85 to the solar panel and 86 to ground

so your using an electric motor? why dont you wire the solar panel in parallel with the battery so that it can supply power and charge the battery when the sun is out and the battery can supply the motor power when its cloudy.

Am currently already overbudget and hence, is there a cheaper way of going about this other than buying a 24V relay? Also, does the voltage supplied by the solar panel and the battery need to be constant? If not, why ?

with regards to connecting in parallel, I was thinking of doing that but someone told me that would lead to a fair share of probs. I think i'd still need a relay though to switch between the battery or solar panel..

The solar panel is to be the primary source of power for the cart when sunny. In addition to powering the cart, it must also charge the battery. When its cloudy, the solar panel will not provide power and hence, the battery will take over and power the cart. Why will it disconnect power from the cart? since the power would now come from the solar panel? Thanks

Oh I see.. its because they are both connectd to relay and hence, the relay does not have anything else to switch to since these two power sources are connected in parallel? What if I removed the relay, then when the solar panel does not provide enough power, then the battery will do the job and vice versa? this way, I can get double the amperage Also, I searched for 24V relays and found the following: http:///.com/DPDT-Relays-12-VDC-10-A-Fujitsu-FRL-264_W0QQitemZ5874849687QQcategoryZ4671QQrdZ1QQcmdZViewItem http://heatcoolparts.com/relayscontacpage.html They seem to have different amp rating. My solar panel provides approx 7 amps and same goes for battery.

ok   30 to cart  87a to batt . 87 and 85 to solar 86 to ground.  but this will now add batt power when no sun ....when sun is present will only run on solar.   but this set up will not charge batt.you will need a diode and run it between 87 and 87a with the silver line facing 87a .

How does the diode enable it to charge? It redirects flow of current also to the battery in addition to the coil thus allowing both the battery to be charged and motor to run? Also, I found the following 24V relay which I think will work. Can you please confirm? http:///.com/R8222D1014-Honeywell-Relay-DPDT-24V_W0QQitemZ6031553885QQcategoryZ20598QQssPageNameZWDVWQQrdZ1QQcmdZViewItem Thanks much and sorry for asking so many questions. Am just confused with regards to how the 30,87a,85,86 connections work even though I read the basics article on them.