Homemade low temperature cutoff

[mikefitz]

I'd like to believe I don't need heating, but don't want to trash $600 worth of batteries.

Renogy is a brand label on a 200Ah battery sold by many vendors. Its perhaps this battery,

[Hot Item] Guangzhou 12V 200ah Gel Battery Price

Type: Lead-Acid Batteries Usage: Car, Bus, UPS, Electric Power, Lighting, Electric Bicycle, Boat, Solar Nominal Voltage: 12V Discharge Rate: High Discharge Rate Shape: Square Battery Electrolyte: Acid

yangtze-power.en.made-in-china.com

An internet search will pull up many venders for this or very similar battery.
example,

NPG12-200Ah Gel 12V 200Ah Battery For Solar Power UPS Marine Boat RV | eBay

1. BATTERY TYPE - 12 Volt 200 Amp （10 hour-rate/77F） Deep Cycle AGM Battery With Button Style Terminals(Bolts And Nuts Are Include As Well), warranty time: one years. 2. The High Impact Resistant Battery Case Is Made Up Of A Non-Conductive ABS Plastic. This Material Has a Strong Resistance To...

www.ebay.com

I am in the UK , this seller offers a similar battery , this is the data sheet,

https://www.alpha-batteries.co.uk/wp-content/uploads/k087-exp12-200_1_.pdf

Is is almost the same as the Renogy specification and gives the same conflicting information. It may be a 'lost in translation' issue from the original Chinese specification sheet.

Mike