Sounds like your battery is on it's last legs. It still gives off 12 volts, and that won't change, but it cannot store enough amperage to keep appliances going - sure sign of battery failure. Take it to an auto electrical place to test if you like, but it might be easier to trade it in on a new battery. Also test to confirm the battery is being charged when driving or hooked up to power - though I doubt that's the problem.
Batteries die by becoming effectively "smaller and smaller" capacity. So that is probably why they worked OK before but now will not keep the fridge going for the time to the next solar charge. They just refuse to accept the current after the smaller capacity is reached when charging even though the voltage is up OK. Sitting unused in the shed without charging for a while is also going to age them.
They might recover a bit with charging every day but probably not. If you give them a burst at a higher voltage say 14.8 for an hour or two then that can help in some cases.
Jaahn
-- Edited by Jaahn on Monday 23rd of February 2015 09:05:08 AM
-- Edited by Jaahn on Monday 23rd of February 2015 09:06:01 AM
The only way to take the voltage reading is with a load connected.
Perhaps you should get a basic DC electric theory book from the library. Or even try Mr Google. Collyn Rivers has published several good books on the subject including both batteries & solar. These are often available at public libraries.
If you leave the batteries 'in the shed' or whatever then you should put them on 'float' using a 'Smart Charger' to maintain their condition & useful life. Batteries are dear but 5 stage smart chargers are relatively cheap these days.
A simple analogy to explain why there is not anything happening despite your battery voltage showing Ok.
Connect 8 charged AAA cells in series and theoretically you have about 13V but the current output is not enough to power ANY of your 12v appliances.
Your battery sounds like it is stuffed. Put a voltmeter across the terminals and connect it to the fridge if it is fully charged it should start at about 12.5 V and hold that voltage for a few minutes before dropping. If it drops straight away it is cactus. Don't have the battery connected to solar or a charger.
Specific Gravity
Voltage
12V
6V
100%
1.265
12.7
6.3
75%
1.225
12.4
6.2
50%
1.190
12.2
6.1
25%
1.155
12.0
6.0
Discharged
1.120
The table did not paste correctly. The heading for the first column should be State of Charge, then SG then Voltage
--
Edited by mickm on Wednesday 25th of February 2015 08:03:50 PM
-- Edited by mickm on Wednesday 25th of February 2015 08:06:07 PM
So that is probably why they worked OK before but now will not keep the fridge going for the time to the next solar charge. They just refuse to accept the current after the smaller capacity is reached when charging even though the voltage is up OK. Sitting unused in the shed without charging for a while is also going to age them.
If you give them a burst at a higher voltage say 14.8 for an hour or two then that can help in some cases.
