Gel or Flooded charge setting best for AGM deepcycle batts?

Thanks a lot peter. Some of the stuff I dont know as I dont actually pick up the batteries till tomorrow.

-New Batts are Powersonic (brand) 3 x 120Ah AGM deep cycle

-Im unsure if my charger has temperature compensation. I do know it has a place to plug in a temp sensor so possibly so, however i dont have the sensor to plug in at this time.

-Im unsure what you mean by the battery charging regime.

-Batteries would be recharged once to twice a day depending on amount of use they recieve on the day. Generally they would be used only about 60 days a year max. generally. (only when camping) I do plan to give them at least a monthly top up charge when not in use.

-Loads have been cut down significantly as the old ones have been on the way out for quite a while. They would have to run a 30w 12V engel fridge 24\7 while away along with 11-22watts of lighting during evenings. They would also part time power an 80w tv, 50w tv small dvd player 50w pc speakers. and two notebooks at around 120W each. Generally only one combo of the above would be running but occasionally two as there is kids involved as well. Generally the entertainment gear would only run about 3 hrs a day except for the stereo which is a very modest 11W.
My caravan hasnt got a 3way fridge unfortunately, the previous owner ripped it out and put in a 240V normal household one :( So the electric engel is a necessary evil at this time. An inverter is required to run all of the above except the fridge which is 12 volts and runs straight off the battery. We do turn our inverter off when not in use.

-Batteries are left in the caravan at all times

-12volt setup

- Old batteries (3x 100Ah) were second hand from a UPS back up system. (at $80 each) I believe they were (allegedly) 3YO when i bought them which would be about 2yrs ago, so theyre now around 5YO at least. I was originally using them to power the 240 volt fridge, so that would have been quite a substantial 24\7 drain. (I only got the engel 30w fridge about a year ago.)

Originally I was charging them on the "Gel" setting but I accidentally charged them on the "Flooded" setting after we ran the car battery flat running our power shower. I switched it to flooded for the car battery and then forgot to return it to the gel setting when i put them back on the caravan batteries. They charged for about 90 mins before i noticed and then switched them back to gel setting. The following day I noticed a drop in capacity and also a drastic drop in the time they would spend on bulk charge. Im unsure if it is a coincidence that it happened on this particular day or not.

From this day on they have gradually lost capacity untill today when I took them off the charger (on charge for 24hrs prior) and they only showed 5Volts on the multimeter... LOL... So now they are not even good enough to power my 30watt fridge.

-As stated above they kind of dropped a whole lot of capacity at once but would still hang together for smaller loads. This capacity seems to have further diminished over the last 12 months untill they have become basically useless.

-Yes they are wired in parralel i believe. Currently 3x 12 volt ,100Ah wired for 12volt 300 Ah. New ones would also be wired in the same way to make up 12volt 360Ah. My inverter is a 12 volt 1000 watt PSW inverter so I am kind of liocked into that format unless I fork out for a new inverter.

Thanks again for giving me your opinion, it is most appreciated. If I havent clarified anything adeqautely then let me know and I will try to cover it :)

Sorry missed the last question lol.
No only the gel and flooded settings no fleece setting on my durst charger.

That pic actually looks quite a bit like my inverter but doesnt really look much like my charger at all, apart from the colour. My charger was a 2007 model i believe and has had to be repaired twice.

I just trekked out to chech if i could give you more info. All i was able to glean was that it is marked with BC-012-50A which would seem to indicate more that it is a battery charger 12volt and 50 amp and seems to be too generic to be a model numvber. It is labelled "smart charge" and has a durst industries sticker and contact number on it. It does have over temp. protection definitely, but I guess as i dont have a sensor plugged in that im not using it.. lol... It is also a 3 stage charger.

Thanks again :D

The side fins look similar to my charger too. However it doesnt have those big meaty slots for the charge cable. They are a thinner arrangement with alligator clips on them. This is a guess because it hard to guess the relative size in a photo but they look like the much chunkier cables that i have running into the 1000watt inverter. The top of it looks nothing like mine.Mine has the gel\flooded switch on the top as well as the float voltage switch and the three indicator lights to indicate which stage of charging it is currently in.

>>>>>>>>>>>>>>>>>>>>
they would be used only about 60 days a year max. generally. (only when camping) I do plan to give them at least a monthly top up charge when not in use.
>>>>>>>>>>>>>>>>>>>>

That's good planning. And while they're just sitting there, try to keep them in a place as cool as possible for longer life.

24 hour load budget from your list: fridge 40Ah, lights 8Ah, telly 25Ah, small telly 15Ah, DVD/amp 10Ah, notebooks 40Ah, stereo 10Ah, a total of 148Ah per day. You indicated that only one of these combos will run at any one time, so you've got plenty of leeway with this figure.

Your new 3x120Ah AGM batteries will only see a DOD of around 30 to 40% if you recharge them once per day, less if you recharge twice per day.
This is slight overkill for AGM deep cycle batteries, because the sweet spot (capacity versus longevity versus DOD) can be anywhere between 50 to 90% DOD.
Because you use them only for a fraction of the time, the limiting factor will be their shelf life, not the cycle life - meaning you could increase the daily DOD without shortening their life.

Your second hand ones probably had a residual capacity less than 60% of new. At this stage, batteries not only offer lower capacity, they rapidly become more fragile and prone to grid breakage and other things in a self amplifying loop.
Your little mishap with the charger only pushed them over the cliff. It wouldn't have done much damage to healthy batteries, and none at all if your charger had had the battery temperature sensor connected...

Your initial question about the charging voltage setting still remains unanswered, sorry, you'll have to find out from the charger supplier/manufacturer what the voltages are when selecting flooded or gel.
You'll also want to find out from your battery supplier, what the recommended charging voltages are.
These voltages are valid for a 25 degree battery temperature and generally are to be reduced at the rate of 0.25V per 10 degree increase.

Oops, just saw your charger code...
Yes, it's a Durst, look it up in their pdf.
It says 14.2V boost for Gel, 14.6V for flooded, and float between 13.2 and 13.8V, temperature sensor? n/a?
Yes, you could use it on the 'flooded' setting (presuming your AGMs are specced 14.7V boost), but I'm not sure what the float voltage will actually be. You'd have to measure it yourself - you want to see around 13.6V for an AGM.
Now, we're talking serious 50 amps boost charge current and no temperature compensation...
Thus, be careful when using the charger on warm days and/or warm batteries. Your batteries will lose electrolyte under these conditions which may be ok if it doesn't happen too often. But keep an eye/hand on them during charging and discontinue charging if you feel it's uncomfortably high.
A high battery temperature might prevent the charger from reverting back to float voltage, and things are getting worse quickly from then on....
It's best to select 'gel' on warm days, which gives you a reduced 14.2V boost - slower charging rate but much safer for your new AGM batteries.
When you come home from your trip, on a cool day/night, give them a top off charge on the 'flooded' setting to ensure they won't sit there, partially discharged.

Also, when set to 'flooded' some chargers add an equalisation stage - this is something you have to make absolutely certain it can't happen to your batteries because the equalisation voltage can be anywhere between 15.5 and 16.5V, way too high for VRLA batteries.

If all this turns out to be too hard, you can always look into buying a highly configurable top notch 25A charger with multiple battery protection features.
We stock these for you.
Feel free to ask away by using our notification form in the link provided, or post in this forum.

Best regards, Peter