Have 120w panel and 2x110AH batteries. Only run Cpap machine at night and have just started having problems with batteries running down and cutting out during night despite having freecamped easily over the past 9 weeks. Could our batteries be dying or some other cause?
The definition of "fully charged" might be the problem here. If a 100Ah 12v lead acid battery (flooded cell, AGM, Gel, Lead crystal) has a 60w bulb attached across the terminals, the true state of the battery charge will be clear after a few mins. 12.8v fully charged in as new condition, 12.6, 80% charged or the battery has lost 20% of its capacity, 12.4v around 70% charged or 30% of the capacity has been lost, 12.2v and the battery isn't much more than a door stop unless it can be recharged till it holds better than 12.4v under a 60w load for 5 mins. It might still run the lights for a few hrs, but it won't power much of a load over night.
To get a 12v lead acid battery even close to 95% charged requires the terminal voltage to reach 14.4v and be held there for at least 5 hrs. To get it to 100% SOC requires sitting on a float voltage of at least 24 hrs after the 5 hrs at 14.4v, that will get the last 5% into the plates. Keep in mind that 100% charged is only the remaining capacity, not the brand new capacity, if the battery has lost 30% of its original capacity a full charge will still only get it up to a state where it can hold 12.4v for 5 mins with a 60w bulb attached.
Forget the nonsense about unloaded rested voltage testing, this is only surface charge voltage and meaningless, you want to know the voltage under load because that is what is required to run an appliance.
T1 Terry
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I think like the others your batteries are not being fully charged. Terry's answer might be a bit hard to follow but the drift of it is you might be ruining the battery because of this undercharging.
Basically you need more charging and another panel probably. You said you only have the Cpap on at night ! but if you are using any power during the day to charge your phone or computer or fridge etc then the full output from that one panel would not be going in to the batteries. Also the days are getting shorter now and depending where you are with hills trees etc you might be getting shorter charging days too.
The batteries should ideally be up to voltage by soon after lunch so can then absorb for a few hours and get properly fully charged most days. If they only get to voltage by late afternoon then they never get fully charged and start to loose their capacity. Then an overcast day will bring them down. It is down hill for them from there.
IMHO Get them fully charged NOW before it is too late and they die. A couple of days in a caravan park perhaps. Then fit another panel or some other means of charging them also.
Jaahn
-- Edited by Jaahn on Monday 30th of April 2018 09:15:36 AM
Are you seeing your solar regulator switching to float during the day? If not then you are not fully charging your batteries. For a well designed system this will happen between 11AM and mid-day on a good day. If your system does that then you have enough panels to provide reasonable recharging on lousy days. If you are not achieving that sort op performance then you need to add more panels. 120 W of panels seems very light on for 220 Ah of batteries.
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PeterD Nissan Navara D23 diesel auto, Spaceland pop-top Retired radio and electronics technician. NSW Central Coast.
Have 120w panel and 2x110AH batteries. Only run Cpap machine at night and have just started having problems with batteries running down and cutting out during night despite having freecamped easily over the past 9 weeks. Could our batteries be dying or some other cause?
I am not an Electrician, so can only give a simple layman answer
Could our batteries be dying or some other cause?
Your batteries could be dying, (you do not say how old they are, or type, or brand), some batteries seem to be better made than others. Any reputable battery shop, should be able to test them for you, (after they have been fully charged)
Some other cause could be As others have already said, not enough solar, so that your batteries have slowly run down over time
As others have already said, you should get your batteries fully charged, because running batteries until they are flat, is the quickest way to destroy them
I would suggest having someone check your system, as you say, everythig has been OK for the previoius nine weeks
but the drift of it is you might be ruining the battery because of this undercharging.
