Can a 120v/240v inverter be left on over winter unattended?

[hammick]

So I received my Battery Tender Solar, JR. charge controller. I am testing it indoors with a power supply and it seems to charge nicely and goes to float and holds a constant float voltage.

Contrary to what the manufacturer told me I don't think this think has any temperature compensation. I put it a plastic bag and buried it in ice. The float voltage did not change.

Shouldn't I expect the float voltage to go up a bit doing this (assuming it has built in temp comp)? Or do I have to put the battery on ice also?

I'll be sending these back. It would make a good cheap garage battery tender hooked to a power supply as long as your temps weren't extreme.

Updated testing: I put the charger in the freezer which is set at 0 degrees Fahrenheit. My house was at 74 degrees Fahrenheit. Using the temp comp for the BT Plus it should put out .513 more volts with a 74 degree drop in temp. Same voltage in freezer as room temp.

Ran same test on with my Battery Minder with temp lead and voltage immediately went up when I put the temp lead in the freezer.

Case closed. No temp comp.

[hammick]

I'd still look into exactly how this CC accomplishes the T-comp feature. If fully charged, your battery will not freeze until -90 but if only 40% SOC it will freeze at -16

I called Deltran and they said it uses the same T comp algorithm as the Battery Tender plus. I have asked via email so I can get something more official.

From the Deltran website:

WHAT IS TEMPERATURE COMPENSATION AND HOW IMPORTANT IS IT?
While a battery is being charged, it is important that the charger absorption and float, maintenance voltages closely match the recommendations of the battery manufacturer. The absorption voltage match is important for quick charging. The float, maintenance voltage match is important for long term, storage charging.

Batteries are sensitive to temperature. Recall the number of TV ads showing how tough a battery is when it can start a vehicle in sub-zero temperatures. Cold temperatures tend to reduce a battery’s ability to deliver current to a load. High temperatures not only increase a battery’s ability to deliver current to a load, but also increase a battery’s internal losses. Temperature compensation is a way to change a charger’s output voltage to maintain optimum compatibility with the battery’s charging requirements. The way it works is that the charger senses the ambient temperature. Then it increases the charge voltage when it is cold and decreases the charge voltage when it is hot. Typical values for temperature compensation for a lead acid battery are minus 0.0025 to minus 0.004 volts per degree Centigrade per 2-volt cell. For a 12-volt battery, that would be minus 0.015 volts to minus 0.024 volts per °C. The reference temperature requiring zero charge voltage compensation is 25 °C or 77 °F.

How important is temperature compensation? Like with most everything else about batteries, it depends on the application. For industrial, critical load, standby power applications, where the batteries may be connected to a live charger for a number of years, then temperature compensation can have a significant influence on battery life. In many consumer applications like SLI, deep cycle marine, etc., temperature compensation will increase long-term battery performance, but it is probably not essential in all applications. Where it is most beneficial is in helping to minimize the negative impact of a battery’s self-discharge characteristics in high temperature environments. Deltran Battery Tender Plus Battery Chargers Overcome the Negative Impact of High Temperature on Battery Performance.

The self-discharge rate of a battery is directly dependent upon the ambient temperature of the battery environment. At higher temperatures, the chemical reaction rates that determine self-discharge will also increase.

When a battery sits idle, its self-discharge characteristics will reduce its ability to deliver power on its next use. If the battery either sits long enough, or if the ambient temperature rises high enough, then the battery may become fully discharged. In fact, it is possible for the battery to be over-discharged to the point where it cannot be recovered.
The Deltran Battery Tender Plus battery chargers overcome the negative impact of higher ambient temperature and battery self-discharge in two ways. First, the Deltran Battery Tender Plus battery charger applies a safe, float, maintenance voltage level to the battery to overcome its internal losses and counteract the self-discharge phenomena. Second, the Battery Tender Plus battery charger automatically compensates the amplitude of its charge voltages for changes in ambient temperature. It reduces the amplitude of the float, maintenance voltage as the ambient temperature increases and it increases the amplitude of the charge voltages in colder temperatures. In mathematical terms, this type of compensation scheme is called a "Negative Temperature Coefficient".

The temperature compensation ratio employed by the Deltran Battery Tender Plus battery chargers is approximately minus 3.67 millivolts per battery cell per degree Centigrade of temperature rise above 25 °C. Stated another way, the output voltage of the Deltran Battery Tender Plus battery charger will drop 0.022 volts, or 22 millivolts, for every degree Centigrade temperature rise, when it is connected to a 12-volt battery.
In the event that the temperature would rise enough so that the Deltran Battery Tender Plus battery charger voltage output drops below the what would be considered a normal operating voltage for a 12 volt battery, then the Deltran Battery Tender Plus battery charger automatically disconnects itself from the battery via an internal solid state mechanism, affording an extra measure of safety in a very high temperature environment.

2) B. Battery Charger Output Voltage vs. Temperature (Temperature Compensation): This battery charger characteristic probably has more influence on the battery than line regulation. Even if a battery is kept at its ideal float voltage, and if that ideal voltage is compensated properly for temperature, an increase of only 7 °C to10 °C can still cut the battery life in half, assuming that the higher temperature remained for the entire observation period. Short-term fluctuations in temperature have little impact on battery life, unless the temperatures are extreme. In general, cold is good, hot is bad, very cold is better (but too cold can be worse), and very hot is worse. At the extreme cold end, bad things can happen as well, but those bad things are just dramatic reductions in the battery performance. At the extreme hot end, while the battery is charging, it can emit dangerous gasses. The ideal temperature compensation range for lead acid batteries is typically in the range of 2.5 to 4.0 millivolts per 2-volt cell, per degree Centigrade. The temperature compensation coefficient is also negative, meaning that the change in charging voltage is in the opposite sense as the change in temperature. If the temperature goes up, the charging voltage comes down and vice-versa.

[SunEagle]

I'm nestled up against the East face of the mountains so not a ton of snow. What snow we do get is dry and usually blows right off. My closest neighbor has a substantial solar system and he has only had to clear them of snow once in six years. Plus mine will be mounted almost vertical. Leaves are not an issue.

Sub zero temps can be an issue in the dead of winter with the occasional -20F to -30F

Everything I have read is that a fully charged battery does better in freezing temps than it does in really hot climates.

Since my plan is to have them fully charged and desulphated before floating them over the winter, in theory sulphation shouldn't be an issue. Right?

In theory yes. The batteries should not sulphate but other issues may crop up with the lack of any cycling and just a trickle charge during extended cold times.

I would still take whatever precaution I could to keep them from getting below freezing for as long as possible.

[thastinger]

The reason I don't want to take them home is because I am likely to motorcycle to the property, stay a couple nights before motorcycling elsewhere. That way I can sleep in the travel trailer and have power. My house is 1,100 miles away.

I'd still look into exactly how this CC accomplishes the T-comp feature. If fully charged, your battery will not freeze until -90 but if only 40% SOC it will freeze at -16

[hammick]

-20 is pretty extreme as off-grid solar goes and one of the high end CC would be trying to drive the voltage through the roof if you didn't "clip" the T-comp setting in the menu.

-20F is an extreme temp for my area. I'm at 5,000 feet. Keep in mind that it's only a 15w panel so it can only put out so much voltage.

[hammick]

I've never used one of those, it has one 5 star review and one 1 star review...so who knows. It says it has a temp compensating function but I couldn't find any specs on how this CC accomplishes that feature. I think that feature will be important to you if the batteries are stored at -20 but the value doesn't seem to be settable by the operator. -20 is pretty extreme as off-grid solar goes and one of the high end CC would be trying to drive the voltage through the roof if you didn't "clip" the T-comp setting in the menu.
I think it'll be better than nothing though. I still don't see why you don't just take them home and store them in less severe conditions, you're talking about 120lbs of battery to lug home.

The reason I don't want to take them home is because I am likely to motorcycle to the property, stay a couple nights before motorcycling elsewhere. That way I can sleep in the travel trailer and have power. My house is 1,100 miles away.

Also my 48v eight battery bank of identical batteries will also be there (although they will have a pretty expensive CC on them though).

[hammick]

It might work if the panels don't get covered with snow or leaves. I did not see your answer on how cold it will get where the batteries are being housed.

Trickle chargers can put some amount of current into a battery system but they will eventually sulphate and will need to be checked on a periodic basis to make sure the they are accepting the charge. It won't take long for a battery to discharge and die in the cold, dark, winter.

I'm nestled up against the East face of the mountains so not a ton of snow. What snow we do get is dry and usually blows right off. My closest neighbor has a substantial solar system and he has only had to clear them of snow once in six years. Plus mine will be mounted almost vertical. Leaves are not an issue.

Sub zero temps can be an issue in the dead of winter with the occasional -20F to -30F

Everything I have read is that a fully charged battery does better in freezing temps than it does in really hot climates.

Since my plan is to have them fully charged and desulphated before floating them over the winter, in theory sulphation shouldn't be an issue. Right?

[thastinger]

I've never used one of those, it has one 5 star review and one 1 star review...so who knows. It says it has a temp compensating function but I couldn't find any specs on how this CC accomplishes that feature. I think that feature will be important to you if the batteries are stored at -20 but the value doesn't seem to be settable by the operator. -20 is pretty extreme as off-grid solar goes and one of the high end CC would be trying to drive the voltage through the roof if you didn't "clip" the T-comp setting in the menu.
I think it'll be better than nothing though. I still don't see why you don't just take them home and store them in less severe conditions, you're talking about 120lbs of battery to lug home.

[SunEagle]

Ok back on topic. My goal is to maintain two 6v 208ah GC2 batteries wired in series. They will have no loads on them over the winter and will be fully charged and desulphated before being put on the charger.

My plan is to use one of these: http://www.amazon.com/Battery-Tender...y+tender+solar

It will be connected to a 15w solar panel that will be mounted due South and almost vertical. Probably 75-80 degrees.

The BT solar float charges at 13.2 volts just like their standard chargers. In good sun I should have about 1.25 amps of charge.

I tested my 15w panel with a good voltmeter. Even with clouds it puts out over 13v. Full sun and its about 14.7v.

This should work just fine or am I missing something?

It might work if the panels don't get covered with snow or leaves. I did not see your answer on how cold it will get where the batteries are being housed.

Trickle chargers can put some amount of current into a battery system but they will eventually sulphate and will need to be checked on a periodic basis to make sure the they are accepting the charge. It won't take long for a battery to discharge and die in the cold, dark, winter.

[hammick]

Ok back on topic. My goal is to maintain two 6v 208ah GC2 batteries wired in series. They will have no loads on them over the winter and will be fully charged and desulphated before being put on the charger.

My plan is to use one of these: http://www.amazon.com/Battery-Tender...y+tender+solar

It will be connected to a 15w solar panel that will be mounted due South and almost vertical. Probably 75-80 degrees.

The BT solar float charges at 13.2 volts just like their standard chargers. In good sun I should have about 1.25 amps of charge.

I tested my 15w panel with a good voltmeter. Even with clouds it puts out over 13v. Full sun and its about 14.7v.

This should work just fine or am I missing something?

[Living Large]

Living in the outback may have the positive side of being beautiful and serene, which IMO is very desirable but when it comes to basic lifestyle needs, not having a solid power source can be a PIA.

Agreed. I am going to discover how well this argument plays with a board of 9 people who mostly are using theirs as a second home, and not in winter. When it is -10 or -20F, and 3 feet of snow, I am thinking that a solid power source, with an emergency backup, will give me peace of mind. I will already have to worry about keeping clear the 3/4 mile road that is not plowed more often than weekly.

[thastinger]

What did you decide OP?

I'm in a similar situation as you, although I get to my remote garage about every 4-6 weeks in Winter. Here are the challenges I see with your desires. Your CC is going to cycle the batteries everyday even if there is no load on them, you're going to have to either charge them or bring them home because you can't leave a FLA sitting in -20 temps in a SOC that degrades every month. Your battery lit should have something on this matter. I don't think you'll be able to go 6 months without exposing the tops of the plates in the battery to air due to the water loss resulting from bulking the battery bank each day.

Some possible solutions.
- because I'm rarely at my site, I chose the MN 200 because it has arc fault and ground fault built in, you can remote monitor it with their software provided you have an internet connection.
- bring all batteries home and care for them there
- plan to make a trip at least every couple of months to EQ the bank and add water

[SunEagle]

It's a great opportunity to irritate the HOA in this snooty lake community, that appears to be gearing up for a fight over crossing their precious creek, which is impassible by canoe. They apparently would prefer I spend the extra cash, and mow down 3/4 mile of trees in the ROW I am entitled to use in deed restrictions, versus 1/3 the number and the 100' crossing of the creek, which is not expressly permitted. The crossing is at property lines and entirely surrounded by 100% treed private property (5+ ac lots) that general community members can't get to, and is currently undeveloped except my cabin. I go before them next month. I don't like seeing power lines - but these won't be seen unless you try to.

Oh sure, I can power an LED. Maybe draw 0.5W, until the POCO believes my phone is off hook.

It goes to 20 below 0 in winter, the insolation is poor, and my clear sky is from 9:30 to 2:30pm. I decided this is too risky for solar.

Living in the outback may have the positive side of being beautiful and serene, which IMO is very desirable but when it comes to basic lifestyle needs, not having a solid power source can be a PIA.

[Living Large]

It still sounds like a great opportunity to create something from scratch and who knows.... you might have enough power from that phone co current to run an led!

It's a great opportunity to irritate the HOA in this snooty lake community, that appears to be gearing up for a fight over crossing their precious creek, which is impassible by canoe. They apparently would prefer I spend the extra cash, and mow down 3/4 mile of trees in the ROW I am entitled to use in deed restrictions, versus 1/3 the number and the 100' crossing of the creek, which is not expressly permitted. The crossing is at property lines and entirely surrounded by 100% treed private property (5+ ac lots) that general community members can't get to, and is currently undeveloped except my cabin. I go before them next month. I don't like seeing power lines - but these won't be seen unless you try to.

Oh sure, I can power an LED. Maybe draw 0.5W, until the POCO believes my phone is off hook.

It goes to 20 below 0 in winter, the insolation is poor, and my clear sky is from 9:30 to 2:30pm. I decided this is too risky for solar.

[lkruper]

If you don't count the loop current from the phone company, I have zero power. For some reason, they laid 3/4 mile underground service many years ago, and the main box is about another 1/4 mile away. So I can enjoy DSL if I can get power for a network device.

I am not going to run POCO the same route - it would cost $133,000! I am looking at about 1600' to come in another way and over a creek and up a steep slope. A bit under half that cost, worst case. If I subdivide my property and build another house, I can put a good chunk of cash into the new house instead of giving it to the POCO - I jump from 100' free to 1000' free. Next best case. Or, last, I can find one or two others along the route to go online, to provide the free footage. It's $35 a foot.

It still sounds like a great opportunity to create something from scratch and who knows.... you might have enough power from that phone co current to run an led!