Winter Weather and Lead Acid Batteries

[Josh M.]

I am using Super Start 31 DCMJ Standard Lead-Acid batteries for my solar setup and I have them setup under cover of the nose of my 5th wheel RV. Yes, they are somewhat exposed to the weather but only in terms of the outside temps, they do not get wet. And I am well aware this is not optimal for any season, but that is why I am asking. Also, they aren't sitting directly on the ground. I have them sitting on a few 4x4 pieces of wood so they are 4" off the ground. I have read enough to know I need to get them enclosed and insulated somehow before winter, so I am looking for best suggestions based on what I have available. I am currently living in a 5th wheel RV on my property until my house is built and enclosed spaces are extremely limited. The manufacturer says these batteries are maintenance free BUT that you CAN add distilled water if absolutely necessary (doesn't sound very maintenance free if you ask me). So, I can only assume that based on this, they are not sealed and need a ventilated space to keep them in. Temps here are supposed to get as low as the 20's (F) during the winter months. Would it be sufficient to build a wood box and use foam board to insulate the box, while still keeping it outside under the cover of the nose of my 5th wheel? I also thought about the possibility of using a cooler like an Igloo or something cheap that I wouldn't feel terrible for drilling holes in it.

Any suggestions are appreciated! Thanks!

 

[Substrate]

Those "maintenance free" starter batteries are primarily designed to relieve the average consumer from topping them off for 4 years. Additional electrolyte is added (as compared to the normal wets) to help compensate for lack of maintenance.

But feel free to maintain them properly.

Note that aside from mere warmth, to get that level of anti-freeze protection, means that you need to keep them charged! When batteries are discharged, the acid in the electrolyte turns into water. Now THAT - (an undercharged wet-cell battery with mostly a watery electrolyte) can freeze and crack cases.

So while the igloo or whatever you come up with to keep them warm, running them into a highly discharged condition is perilous in cold weather.

If your solar setup has an SCC controller with a remote-temperature probe, so much the better! Without one, the proper-temp comp is not applied, and contributes to under-charging. An upgrade to an SCC with a remote temp probe would be highly desirable. Place the probe on your positive terminal.

 

[Josh M.]

Thanks for the insight on the battery maintenance! Very helpful!

In regard to charging, so far that has not been an issue. I have 4 of these batteries (12V 105Ah) set up for 24V and have them set 2S4P so I still get the 24V but have 210Ah. I have 8 100W panels and have not had issues yet getting full charge. They run at an average of 27V to 28.5V all day while I am under load then I don't let them drop below 23V after sun down. I currently get approx. 7.5 hours of sunlight per day, though that is obviously getting shorter as we draw into winter.

I currently have an Eco-Worthy 60A PWM Charge controller and one of the screens does display a temp reading, but it is only displaying the temp inside the charge controller (seems like a worthless bit of info to me, but what do I know, lol!) so I don't believe that is doing me any good in this area.

 

[Substrate]

I currently have an Eco-Worthy 60A PWM Charge controller and one of the screens does display a temp reading, but it is only displaying the temp inside the charge controller (seems like a worthless bit of info to me, but what do I know, lol!) so I don't believe that is doing me any good in this area.

So your setup sounds fun. Cool.

Just know that an ambient temperature compensation is only relatively useful when the batteries are in the same environment. But here, there could be a wide disparity with your SCC being warmer than the batteries, and not applying the right temp comp, cutting back, undercharging the batts.

You see this a lot in say RV installations where the batteries are in a bay under the rig, but the SCC is in the nice and toasty cabin. The SCC with only an ambient temp sensor is in the wrong place.

 

[Josh M.]

So your setup sounds fun. Cool.

Just know that an ambient temperature compensation is only relatively useful when the batteries are in the same environment. But here, there could be a wide disparity with your SCC being warmer than the batteries, and not applying the right temp comp, cutting back, undercharging the batts.

You see this a lot in say RV installations where the batteries are in a bay under the rig, but the SCC is in the nice and toasty cabin. The SCC with only an ambient temp sensor is in the wrong place.

Well, currently everything is outside, under the cover of the nose of my 5th wheel RV (batteries, charge controller, inverter, combiner box). So, perhaps the temp showing on the controller may be similar to the temp of my batteries?

 

[Substrate]

Right on - that's close. Us hard-core types use a remote temperature probe anyway because lead doesn't acclimate to temperature changes very fast.

So the possibility exists that during periods of fast temperature change (say during the morning or late afternoon hours), you could be charging at the wrong automatic compensation rate based on ambient, rather than what the actual lead temperature is at.

 

[Josh M.]

So, I was able to finally buy the materials to build an insulated box for my battery bank. I used 7/16 plywood and insulated it with 1" foam board insulation. For the first few days, I thought it had done the trick. My batteries were at 28.7v to 29.1v during the late afternoon where they were normally around 27v to 27.6v. However, for some reason, all of a sudden, my solar isn't lasting through the night any more where previously we were only dropping about 1v to 1.5v overnight. The trmos have been below 30 deg f and as low as 20 deg f but but thats why I built the insulated battery box. The other major change besides the night time temps is that our RV furnace kicks in about every 45 minutes during the night. It typically runs for about 15 minutes at a time. It runs off of the 12v RV battery (105Ah deep cycle RV battery), but I also know that when the RV is plugged into the solar, the solar is also charging the RV battery. Could this be the culprit that is draining my solar overnight?? Besides the charging of the RV battery, the only things plugged in at night are our phone chargers and a white noise machine.

Any insight to this would be greatly appreciated!

 

[Vigo]

Have you measured the electrical consumption of the furnace? If you ever ran it overnight off only the starter battery and it didn’t drain that, it likely also isnt draining that battery PLUS four other batteries.

How is the 24v system charging the 12v? if that charging is continuously ‘on’ its possible that a starter battery suddenly taking a dump at the first real cold snap (which they OFTEN do) could mean you are draining the 24v into the 12v and when you disconnect that charging you may find the 12v immediately dropping to a much lower voltage, or self-discharging rapidly.