Two 12V trickle charge panels for 24V (two 12V in series) starter batteries

[Mr Creosote]

I've been given a couple of small, low wattage (I think they're 10W) trickle charge panels, which I would like to find a use for. They're the kind that don't need a charge controller, and are meant to be connected straight to a starter battery. They're meant for trickle charging 12V batteries, but the truck's starter batteries are connected in series, so they're 24V.
Can I just wire the two panels in series and trickle charge at 24V?
Would I better off having each panel trickle charging each battery, would this lead to uneven charging, or would it charge evenly enough if the panels were mounted right next to each other and getting much the same amount of sun?

 

[Supervstech]

Most trickle panels cannot be wired in series without damage... depends on the model...

 

[Mr Creosote]

Thanks, the part number is STP010, I've attached a photo of the label which has the specs on it. I'm a bit confused as to how these specs can possibly be suitable for trickle charging a 12V battery without a charge controller, the voltages seem far too high?