Are deep-cycle batteries for off-grid power tolerant of temperature changes? [closed]

Question

I have a small shed that is off-grid and needs occasional lighting. During the day I can open up the doors and have sufficient light, but during the winter when I am out there more in the evening, I need occasional light.

Ideally I would like to have 4x 4ft LED shop lights hung from the ceiling. In my experience these use 40-50 watts. I don't think I would have a need to plug in anything else, maybe a phone charger, drill charger, etc., but nothing with a high power draw.

I can drive up to the shop so it's not a huge deal to bring a battery back and forth. Solar is not an option due to tree cover.

Options:

• Deep cycle marine battery + power inverter + battery charger back home. Should work, hauling back and forth the battery is inconvinient but not a deal breaker. I am skeptical of the off-brand inverters on Amazon.
• Dedicated rechargable lights - they make plenty of handheld rechargable lights that would not be as convinient as a shop light but would be easier to move back and forth and recharge. I did see there are some rechargable shop lights on the market but it is unclear how these charge, if you have to pull down the entire light assembly to charge, that seems inconvenient.

Questions:

• Are deep cycle marine batteries sensitive to temperature fluctuations; can I leave them out in the cold? Do I need to keep the battery "topped off", or can I use 5-10% of it's capacity 1x a week for a couple months?
• How big of an inverter should I get? Is 250W sufficient? Is there a downside to going bigger, like 500W?

Answer 1

Here is a solution that I think is CHEAP, easy and versatile.

You don't need to light up the whole shop at work-level lighting. Install 12V LED ceiling lights that are enough to walk around safely, carry things in and out etc, but not enough for painting or other tasks where you want to see well. Power them from a 12V outlet in your vehicle. If you have an EV or a hybrid or even auto-start-stop this is a no-brainer. If you have a regular old vehicle battery you may need to run the engine for half an hour periodically. Do that.

An easy way to buy 12V lighting is to look for landscape lights. They are really easy to work with. Not the super-cheap all-plastic ones but the next level up, with metal frames. Throw out the spikes, screw the frames to the structure, and use landscape wire to connect them. It's so easy, you don't need junction boxes or tools. With slightly more effort and money you can use more efficient strip lights to reduce battery draw. See comments (and hopefully answer) from @dandavis about that.

For everything else: Your phone, power tools, and work lighting: Buy and use ones that have their own charging solutions. A portable charger for your phone. Even the cheapest one will run you all night. Work lights that are hand-held or floor-standing or head-mounted ... all of these things use standard interchangeable PD chargers that you probably already have. And your tools obviously you can come with enough charged up batteries to do what you need. All these things are useful at home and during the day too, you don't need to buy special anything for your shop.

$100 --- all in. Unless you need a ton of batteries for a table saw or something like that but your question says you do not.

Answer 2

Ready made battery "power stations" are now widely available. They contain a pack of LiFePO lithium cells, a charger and an inverter. Most will output 5V, 12V and either 120V or 230V depending on where you buy them. They are available in a wide variety of different sizes, so you can pick one with as much capacity as you need.

They can usually charge off the grid at your house, solar panels if you can leave them somewhere sunny, or using 12V in your car.

For convenience, they can't really be beaten. They are lighter than lead acid batteries, and come as one ready-assembled unit. With a handle or two on top. The down-side is the price.

It would be more efficient to run your lighting off 12V, provided that isn't going to exceed the unit's maximum output. Running the built-in inverter drains the battery, on top of the load you plug in.

Answer 3

Seriously consider lighting that runs on the battery voltage directly, not through an inverter. Inverters have losses, and will chew up some of the battery power making heat. A small inverter for the phone & drill chargers can be much less loss than a huge inverter running the whole lighting system. There may also be battery-powered chargers that can run directly off the battery instead of having to go through an inverter. Battery-powered LED lighting also does not need the 120VAC-to-DC conversion either, which also results in some loss and inefficiency.

The larger the inverter, the more "quiescent" current it draws: how much electricity it takes from the battery when running nothing. Pure-Sine-Wave inverters have more quiescent current, but produce more utility-like power.

You may also do better using Lithium batteries. They'll be lighter for the power produced. And you should be able to get a battery or two and charger from a reputable solar panel website.

If you do decide to go with the old-school marine battery and big inverter for utility-power-level lighting, the inverter should be at a decent guess twice the size of the normal load it will be feeding, so the inverter won't be running at full power all the time, which is bad for electronics.

A reasonable rule of thumb for inverter load is 1 amp of 12V DC for every 10 watts of 120V AC. An amp drawn from a battery for an hour is 1 amp-hour. Batteries have an amp-hour rating, but how many amp-hours you can actually use and how fast you can use them depend on the chemistry of the battery. Lead acid batteries only feel comfortable giving up 20% of their full charge (drawing down to 80% state of charge or SoC). Lead acid can handle being drawn down to 50% SoC, but they will not recharge as many times as if they were run down to 80% SoC. Keep in mind, SoC is how much charge is still left in the battery.

Additionally, as illustrated here on Electronics.SE, Lead Acid does not like to use its charge too fast. They only like to give their named amp-hours over 20 hours of time. Draw it faster than that and you'll get less of it. This means an even bigger battery. Lead acid does not like to be used. (There may be some similar limits for Lithium, but Lithium will give better performance.)

Assuming 40 watts per fixture (commensurate with a web-search I did for 4 foot LED shop lights), that's 160 watts. A 300-watt inverter should do, if the lights' inrush current isn't too bad. Maybe get 500 or 600 watts inverter to be safe. At 1 amp 12VDC per 10 Watts 120VAC, 16 amps will be drawn for the lights from a 12V battery. If you run the shop lights for 8 hours, that's 128 amp-hours, not counting the inverter's quiescent demand. Triple that for the battery size you need to run the lights (down to about 67% SoC) and be able to recharge the batteries for a reasonable number of times, and then double it again for considering the speed at which the current is being drawn: starting at 400 amp hours, maybe up to 800 amp hours of lead acid battery.

Answer 4

If you're not married to the idea of using batteries and LEDs, consider using a BBQ propane tank with an extension pole for a propane lantern. It works at any temperature, it makes as much light as a 60-100W incandescent bulb, and it's virtually maintenance-free. No reason you can't use two of them to eliminate shadows.

If course, if the work you're doing out there involves flammable liquids, this may not be the best solution, but it's worth considering otherwise.

Photo: sportsmansguide.com

Answer 5

Extreme temperatures do indeed impact the life span and performance of lead-acid batteries. They change the way the internal chemical reactions operate, and while some batteries may operate fine in extreme temperatures, they generally don't support being charged outside a limited temperature range. You could make this work, but it would be a hassle and might not last very long.

My company often finds itself doing jobs in far off-grid locations, and here's the sort of thing we use.

Many tool vendors use the same rechargeable batteries for a wide variety of tools. They often also sell work lights that use the same tool system. For example, Milwaukee has lights in a variety of shapes and sizes. Find something similar that uses the same batteries you already have. A few lantern-shaped 360-degree lights are good for general area lighting. I recommend two, placed on opposite sides of the shed (maybe 3 if it's a large shed).

When you need more light to work on something specific, head-mounted lamps (sometimes called miner's lights) work very well. The light's always pointing where you're looking, and they typically run on batteries that you can easily swap out and recharge. Also, a handheld battery-powered work light with a magnetic base is amazingly effective. Stick it to a wall, shelf, or wherever else you need it. You can even add your own light mounting points as needed by screwing a large washer to the wall. If your shed has exposed rafters, you can hang a rechargeable work light with a hook almost anywhere you want. I don't think you need anything permanently installed.

Answer 6

Maybe a small inverter generator. A few years ago, when a hurricane was looming, my local big-box got a shipment of 1000w inverter generators (about 8.3 amps). They were much cheaper than their larger counterparts (most in this size are 1600-2000w) and it's enough to run a refrigerator plus any other electronics you might want. With auto-throttle, they don't make much noise.

Another option would be a large lithium battery cell (sometimes billed as a generator alternative). These are still pricey, but are getting cheaper over time. Basically you charge this device and it can provide hours and hours of runtime.

Since you're now using standard AC power, any lights connected to an extension cord will do.

Answer 7

I am invested in the Ridgid 18v line of power tools so my answer is a bit biased towards my existing inventory.

I would get 2 or 3 pure sine-wave inverters, a few extension cords, and a few cheap-o clamp lamps with the aluminum reflectors.

Answer 8

A power tool battery is about the right size for providing 50W for an hour or two. A 20v 5Ah battery is 100Wh, or 50W for 2 hours.

Then the issue is finding a light that will run at 20v. It's probably easier to find a 12v lamp, and a small 12v step-down DC-DC converter that can accept 20v input. There seem to be lots for about $20 (24v to 12v is common in large vehicles. Read the specification for the minimum voltage).

This is not only cheaper than buying a leisure battery, but it's a lot lighter to carry back and forth.

An alternative would be a low power background light and a rechargeable head torch.