I have four, old 12V marine-type 100 AH batteries I bought from Walmart 10 years ago that amazingly seem to still be serviceable. They've been stored in the heated garage for the past four years, and I periodically recharge them 2-3 x/ year. I even used them to power my solar setup for a few weeks about 12-16 months ago, until my LFP batteries arrived, and they performed well. I'd now like to put them in a small, enclosed trailer at a remote property we own, to power a weather station and mobile hotspot (that will allow the weather station to report). The big worry is that the trailer will have no heat, and outdoor temps can get to about -15F for a night or two each year, with temps in the single digits common. Will be charging via solar (still need to calculate that, but not worried about that aspect). Total power consumption will be very low, with a continuous draw of only about 20-50W, depending on whether or not I also add a camera. My big question is, do I need to worry about these batteries freezing, or can I just put 'em out there and let 'em do their thing? I've never used marine batteries in such a cold environment. I really just need to get about 6-10 months of use out of them, until a building we're putting out there next year is ready.
Do I need to freeze-protect marine batteries?
- Thread starter Madcodger
- Start date
Solarcabin Channel
Solar Addict
Are those AGM sealed deep cycle?
If they still hold capacity they are fine in freezing temps but I would put them close together in an insulated box to hold in the heat. Batteries produce heat when charging and discharging which helps keep them warm.
Put in some small vent holes for any off gassing.
How are you charging them?
If they still hold capacity they are fine in freezing temps but I would put them close together in an insulated box to hold in the heat. Batteries produce heat when charging and discharging which helps keep them warm.
Put in some small vent holes for any off gassing.
How are you charging them?
Not sealed or AGM. Lead acid with filler caps (will top up with distilled water). Will be charging them with a Victron MPPT SCC, but haven't ordered it yet. Plan to do so soon, especially with their price drop.
Solarcabin Channel
Solar Addict
Ok, well you are going to lose some capacity in the cold and where those are old batteries it could be enough to damage them.
Your load is small so probably be OK but at 10 years a marine battery which is not a true deep cycle like a trojan or Vmax has probably depleted the lead plates and is past it's lifetime.
I would still try it and then you will know!
Last edited:
Vigo
Solar Addict
^ Exactly. The main thing would be limiting the depth of discharge with an adjustable low voltage cutoff. With loads that small, you can power them through the load port of a charge controller and then set it so that it never drains the batteries to an SOC that would allow them to freeze. I would definitely build some margin for error into that setting since your four batteries may or may not stay that well balanced to each other and an outlier might freeze if you set the voltage point 'too close'.
I think the big question is will you have enough solar to keep up with that 20-50w continuous load, with lots to spare to account for poor solar conditions?
I think the big question is will you have enough solar to keep up with that 20-50w continuous load, with lots to spare to account for poor solar conditions?
Thanks, all. Very helpful. These batteries obviously "owe me nothing" given their age, so if I completely destroy them it will simply accelerate their journey to the recycler. I probably need to buy a low voltage cutoff device to be used somewhere else in the future, so this might be the time. I'm basically just moving a small trailer (think 5x7 "tiny house" on a utility trailer, that I built to serve as my office when we moved during Covid) out to this property in preparation for building out there next year (place we can look at plans, etc) and to get it off another property we own. Since I want some idea about the winds at this property, I figured, what the heck... Put a weather station in it. I just don't want to heat the thing. Now I just need to find the time to get all this done before the snow falls. There's the real challenge!
Solarcabin Channel
Solar Addict
Batteries can surprise you. I have had Trojans die prematurely and the Vmax tank AGMs way outlast their life and still working.
There seems to be a sweet spot where batteries like to stay and as long as you keep them in that sweet spot they will just keep working.
Vigo
Solar Addict
As far as a low voltage cutoff device, they do sell little standalone PCB devices which are just a little relay and voltage sensing circuit on a board.. but no housing no screen etc for the cheapest ones. Meanwhile, for as little at $9 you can get a cheap PWM solar charge controller that is effectively an adjustable low voltage cutoff switching device with a screen AND is also a solar charge controller which you may find useful at some point. So i generally recommend using a pwm charge controller as a cheap low voltage cutoff device vs buying a standalone device. There are a couple of caveats but they are mostly only applicable to vehicles where your system is using a common chassis grounding system.
Similar threads
