Battery discharge question

[Surfer]

We are off grid at the moment and cannot understand why our battery is draining so quick. The battery charged through the solar panel and was reading as full charged. Last night we had on one led light for about 5 hours, another for about an hour. The ALDE heating was running for about 4 hours before being turned down so maybe it ran intermittently during the night as temp set to 18. Water pump switched off.
Only draw overnight should be fridge and heat pump yet when we woke up voltage had dropped down to just over 11v. We now suspect that there may be an issue causing the batery to lose so much in such a short time. The battery is about two years old and is Numax 110ah leisure battery. Thanks.

 

[MichaelE]

You would be surprised how much current the Aldi heating draws as its constant ? I would fit a little ammeter between the battery and the output just to get an idea what and if is drawing the power?
The battery could be faulty or to have a faulty blocking diode in the solar panel which is causing the current draw?

 

[Surfer]

You would be surprised how much current the Aldi heating draws as its constant ? I would fit a little ammeter between the battery and the output just to get an idea what and if is drawing the power?
The battery could be faulty or to have a faulty blocking diode in the solar panel which is causing the current draw?

According to ALDE the pump draws about .2amps when it is running so very little plus it is switching on and off during the night. Not sure about blocking diode issue as no idea what that is or where it would be located. I will be changing over the battery later today to check if it is the battery.

 

[MichaelE]

I think in the real world its pulls more than that, the blocking diode is usually located across the + and - terminal in the junction box on the back of the panel. Although i believe some regulators do the same job?

 

[MichaelE]

I have one of these fitted Nasa BM Compact Battery Monitor,at rest my van pulls around 1/2 amp ,which is just the fridge and nothing else on, my radio has an isolating switch. I can see the ampage of every thing that i put on and my alde heating running pulls over 1/2 amp.

 

[Surfer]

I have swapped over batteries as had a "spare" new 110ah Numax battery and problem resolved. Seems the battery has gone faulty. It charges up to read 12.7v but using only a 25w TV on it, the battery is flat in less than an hour. The same Tv worked for about 15 hours off the other battery.
Any recommendations for a genuine deep cycle leisure battery? Traction maybe?

 

[Surfer]

I have charged up the "faulty" battery using the charger art home and the reading seems to be remaining constant at 13.02v. If you have a solar panel surely that should be able to keep the battery topped up to 13+v? I will give it a day or three and see if it drops the voltage. As it is a sealed battery is there any way that one could do a load test?

 

[JTQ]

Even a fully charged and in excellent condition lead acid battery will when rested decay to 12.7 to 12.9 volts; the actual value depending on the alloying in the lead. All volts above this rested value are what is known as "surface charge"; this dissipates, but still leaves the battery fully charged.
Even duff batteries can exhibit this 12.7 to 12.9 volts, but this only means it is as full as it can be. Think of the analogy of a bucket being filled with water. If an empty bucket filled to the brim [12.7 volts] then say it holds 3 gallons [Ah], but if pre loaded with bricks it can still be brimming with water, but the amount of water [Ah] could be only 1 gallon. That is the sort of issue we have with tiring batteries, we can still "fill" them, but the capacity is shot, they hold little of what they once did.

 

[Surfer]

Even a fully charged and in excellent condition lead acid battery will when rested decay to 12.7 to 12.9 volts; the actual value depending on the alloying in the lead. All volts above this rested value are what is known as "surface charge"; this dissipates, but still leaves the battery fully charged.
Even duff batteries can exhibit this 12.7 to 12.9 volts, but this only means it is as full as it can be. Think of the analogy of a bucket being filled with water. If an empty bucket filled to the brim [12.7 volts] then say it holds 3 gallons [Ah], but if pre loaded with bricks it can still be brimming with water, but the amount of water [Ah] could be only 1 gallon. That is the sort of issue we have with tiring batteries, we can still "fill" them, but the capacity is shot, they hold little of what they once did.

Good explanation thanks. I am guessing that this is what has happened with our 20 month old Numax battery and why it discharges so quick after being topped up. I wil get the 12v TV from the caravan later today and plug it in to see how quick the battery discharges as it has now been on a mains charger at home since Monday afternoon.