40v to 12v

[Strawman]

I'm off grid. I have a couple of panels on 12v leisure batteries.  I've been given a new 40v panel so thought I'll need to reduce voltage.  But do I? What happens if I put 40v into 12v battery? Cheers 

[SteamyTea]

It will bubble a lot, get hot, then not last very long.

 

You can get cheap charge controllers.

 

Just one example.

 

https://www.sunstore.co.uk/product/ep-solar-landstar-10a-12v-solar-charge-controller/

[RobLe]

You def need some sort of charge controller, or the batt will die  - the cheap ones tend to be PWM only - I think they're fine if the panel is about the right voltage for the battery.  MPPT will perhaps double the current (hence power) output from the panel - eg this one:

https://uk.renogy.com/renogy-rover-20-amp-mppt-solar-charge-controller/?Rng_ads=03b67fab5b39c2aa&kw=&ad=&gr=&ca=20759790391&pl=ga&gclid=Cj0KCQiA6vaqBhCbARIsACF9M6n-o8GFD95rBOJdUawQzalez1l8EGmQBSzacZ-BLyoECsXhTQDmfC0aAr2iEALw_wcB&gad_source=1

 

Only you can decide if it's worth the extra money!