Depth of Discharge for Gel batteries

[davethedog]

Morning all,

A query regarding depth of disharge for my 12V trojan gel battery bank.

5 x 102Ah = 510Ah total.

Am I being too paranoid by getting overly concerned if the Amp Hr used by the morning is 150 (as we have a fridge, freezer and now Starlink running)? As I read that these gel batteries can go to 80% DOD (400 Ahr) and not 50% (255 AHr) like FLA batteries.

We have 620W of solar and could normally get to float by the end the day, but not if it is raining biblically like today here in Prickly Bay, grenada!

Is it essential to get to float each day, I know that it is ideal, but what if the battery bank was drawn down to day 250Ahr used over 2 days and then charged?

Just asking as think I am being overly cautious with the batteries and have a generator can run if required but prefer not to!

Thanks in advance and yes, this may seem a stupid question!

DTD

[Kettlewell]

Personally, I would follow the manufacturer's recommendation, whatever that may be. My experience with gel Prevailer batteries is that they were absolutely the most durable of any I have used. They were totally abused on a cat we owned with only solar and wind charging. Flattened those batteries many times and they always came back. I would watch the voltage too and not just the Amp Hrs measured.

[rslifkin]

The usage you're describing in the first post should be absolutely fine. You want to get them fully charged as often as you can, but if you go 2 or 3 days without getting them topped off, the world isn't going to end.

[davethedog]

Thanks as that is what I am thinking as now we are running the Starlink sometimes (if not a very bright day) the batteries may not get to float by the end of the day.

[Hobiehobie]

Not an answer for you, but will be interested to follow. I use a different measure: I don’t let the battery voltage go below 12.0v. If it does so we charge with generator or make the sun shine more! Not sure if monitoring the voltage is the best way, but that is what I have been doing.

When I look at the cycles and other data deep in the MasterVolt controller, all batteries seem to be very healthy considering they are 5 years old.

[rslifkin]

Originally Posted by Hobiehobie

Not an answer for you, but will be interested to follow. I use a different measure: I don’t let the battery voltage go below 12.0v. If it does so we charge with generator or make the sun shine more! Not sure if monitoring the voltage is the best way, but that is what I have been doing.

When I look at the cycles and other data deep in the MasterVolt controller, all batteries seem to be very healthy considering they are 5 years old.

If your loads are always very light relative to the size of the battery bank, voltage monitoring can give some indication of charge level. But if you have heavier loads at times, it's hard to tell due to voltage sag under load. I've seen fully charged batteries pulled under 12v temporarily by a heavy enough load.

[davethedog]

Forgot to add, we monitor the battery bank with a Mastervolt shunt and an Easyview 5.

[noelex 77]

As others have indicated, good deep cycle gel batteries are the best of the lead acid options.

There is no hard limit on depth of discharge for any lead acid battery, but you need to be aware that the greater the DOD, the shorter the cycle life. Occasionally discharging the battery down to a low SOC (for example 20%) is not unusual, especially on boats relying predominantly on solar. While not ideal, you will still achieve good battery life, especially if the majority of discharges are shallow, as is common on solar equipped boats.

Gel batteries are also reasonably tolerant of PSOC cycles. Achieving 100% SOC after every cycle is ideal, but there little difference if this is only done once a week or less. Even occasional stretches of months where 100% SOC is not reached seems to have little practical effect on their life in my experience.

Try and keep the SOC as high as possible, but don’t fret. Batteries are meant to be used.

[davethedog]

Thanks and that is what I was thinking, as got to get out of the mindset of worrying when I use more than 20% of the capacity.

As I am typing this the Easyview is showing:
Battery 83% SOC
118AH consumed (which does not seem to make sense as 17% used of 510AH should be 87AH).
Battery volts at 12.22V
Amps out at -12.4A