UPS wireing diags

Hello I have a coming data c-600va ups that we are pelacing that battery in. Having taken 2 month for the new batterys to show up I have forgoten which wire is + and -. The simple red =+ and black = - dose not work as the wires are yellow and brown. the logical conclusion is that yellow = + but the unis becomes an arc wleder no mater what I do! (scary) Perhaps a dead shor on teh units board???

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