Battery Storage Problems Summer vs Winter

Solar Testing


Charging Batteries Summer Vs Winter

How long does it take to charge a battery Summer Vs Winter?

Well, it all depends on what type of battery, the battery voltage, and the battery amperage.

Let’s say for instance this is a Solar setup for a Campervan or Glamping Pod.

1 x 220ah 12v Lead Acid Battery, because this is a Lead Acid battery you have something call 50% depth of discharge or 50% DOD. This does not mean that a 12v battery is flat at 6v, it means that the power range of a 12v battery is 13.6v Full and 12v Flat, going below 12v with damage the battery which can be very annoying and expensive.

So, maths time again.

220ah divided by 50% = 110ah (So a 220ah battery is only a 110ah battery)

110ah x 12v = 1320watts of usable power before the battery is flat, but its not a good idea to fully flatten your battery just in case the weather is bad the next day and you have no power left, so you need to keep a reserve for the next day.

Now we need to work out the wattage of the panel and the time of year.

A 350w panel in the Summer Tracking the Sun all day will give you 30amps per hour for around 14 hours = 420amps of power meaning that your battery will be charged in under 4 hours.

Now lay the panel flat on your roof, the panel is not facing the Sun so you reduce its performance maybe by 50% so you will be fully charge in 8 hours.

This sounds good, we have made enough power to run our appliances, lights, TV, phone charges, DVD player etc through the night and still have power left over and by the night fall the battery is full again.

Now let’s do this in Winter, your solar panel will be producing less power because of the distance the Earth is away from the Sun, the weather, the position of the panel and the daylight hours available.

This could be as low as 21w per hour so maths again:

21w x 12v = 1.75amps per hour

This would take over 62 daylight hours to charge the battery, but don’t forget we only have 6 hours of daylight.

62 hours / 6 = 10.3 days

See the problem?

Charging from the Grid will depend on your battery charger and how long it will take:

110ah (amount of amps battery needs) / 3amp from charger = 36 hours.

110ah (amount of amps battery needs) / 10amp from charger = 11 hours.

110ah (amount of amps battery needs) / 20amp from charger = 5.5 hours.

110ah (amount of amps battery needs) / 30amp from charger = 3.7 hours.


So, the trick is not to let the battery run low, you need to ration how much power you can use during the Winter months otherwise you can get left without power for quite a while.

To solve this problem, you will need to add more Solar Panels and more batteries to store the spare power you have produced.

Generating power through the Winter months is difficult, that’s why the Winter season is cold and wet with long dark nights.


Battery Power Management:

So, let’s look at this above setup, we have 1320w of power to last us, but we need some for tomorrow too just in case the weather is bad so let’s divide by 50%. Let’s break it down.

1320w divided by 50% = 660w divided by 24hrs = 27.5w per hour

This means you will keep your battery topped up and every day you can use 27.5w of power every hour, or you can run 2 x 10w lights with 7.5w spare, or you can run a 100w TV for 2 hours with 2 lights on for 6 hours and still have 340watt of power left.

But if you’re having a period of bad dark weather, your battery will not be able to fully charge so you would need to work out how much power you can use so you are not left in the dark.

As we said before, to alleviate this problem (only if you have the space or the budget) more panels and battery storage is required.

Storing Batteries:

Batteries do not like the cold, nor do they like to be left on cold floors either as the charge can dissipate through the battery into the floor flattening your battery.

They also do not like too much heat either.

Our new maintenance free Lead Acid Sealed batteries can go down to -10 and up to 36 degrees, but keeping them somewhere in between is a lot safer, we tend to keep ours between 5 and 30 degrees.

Putting carpet down underneath the battery or using a closed cell foam like Neoprene, Celotex, Kingspan insulation is a good insulator.

Keeping a good airflow around them is also advisable, not so much with the Maintenance Free versions but with the stanard battery if you orvercharge them or charge them quickly they will give off Hydrogen Gas which is explosive and the battery could go off with a BANG…

I could go on forever with battery safety but will leave it hear.



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