I'm already apologising...

[velo27]

Hey, apologies for the noob questions incoming

System is 24v 2x360w panels, 2x12v 270ah agm batteries with a 30a proflex charge controller and 1700w trojan inverter.
> >
> > I went from in summer the batteries being 100% charged by 10am, running deep freeze 24/7, washing machine a couple of times a day and the water pump when required, and barely made a dent in the SOC...

Question 1, is it normal for the batteries to lose charge over a few hours even without any load and the inverter switched off?

We've come into autumn and the charge controller has started giving me really odd numbers, like -/+ 40% SOC within an hour etc... Can no longer run the deep freeze alone for more than a couple of hours without the batteries running to low from 100%

[chrisski]

I’m surprised you got so much out of that. What you described would have wiped my 12 volt 458 ah batteries and 1350 watts of panels out, especially overnight. The only thing I can think that would hav kept your system running so much is if it was built this winter and these lower numbers are because the weather is just starting to get warm and the freezer is just now starting to work.

With healthy batteries, unloaded batteries and disappearing charge is not normal. My only guess is with the inverter turned off there’s a load on the system, perhaps on a DC leg. You can measure the load with a good DC clamp on meter.

Perhaps the SCC is not charging anymore because its shot or bad connections from the panels. Measuring output to the batteries during charging with a lamp on meter would help.

[organic farmer]

Hey, apologies for the noob questions incoming

System is 24v 2x360w panels, 2x12v 270ah agm batteries with a 30a proflex charge controller and 1700w trojan inverter.
> >
> > I went from in summer the batteries being 100% charged by 10am, running deep freeze 24/7, washing machine a couple of times a day and the water pump when required, and barely made a dent in the SOC...

Question 1, is it normal for the batteries to lose charge over a few hours even without any load and the inverter switched off?

We've come into autumn and the charge controller has started giving me really odd numbers, like -/+ 40% SOC within an hour etc... Can no longer run the deep freeze alone for more than a couple of hours without the batteries running to low from 100%

When was the last time that you did an equalize charge?

It sounds to me like your batteries are dying. If any one cell dies it will pull all of the other cells down with it. The only way to avoid that is to be doing regular equalize charges.

I have three chest freezers. they are all on timed power strips, so they can only run during daylight hours and never from the batteries.

[SunEagle]

That's the problem with solar/battery systems. They work fine until they don't. Usually because the battery has been over discharged and weakened or there isn't enough panel wattage to get the charging amps up to what keeps the batteries happy.

Summer charging is a different animal to Winter charging.

[velo27]

Thx for the responses... Sounds like I'm experiencing normal reduction in performance for the time of year, just didn't expect it to drop so quickly... I'm going to need to add a wind turbine by the sounds of it, cause we have an abundance of wind here.

Never done an equalize charge, so will try that...

Both batteries are measuring 12.8v output, so I guess that's positive..

[chrisski]

Before you equalize, you have AGM batteries. As far as I know, equalizing on AGM batteries is a big no-no. Flooded lead acid is fine, but not AGM.

[velo27]

Before you equalize, you have AGM batteries. As far as I know, equalizing on AGM batteries is a big no-no. Flooded lead acid is fine, but not AGM.

Yes, a quick Google has me getting conflicting information regarding equalisation of AGM, seems to be specific to manufacturers requirements....

I've also just discovered a device, I'm thinking of purchasing called a 'battery equaliser' that ensures equal charging to both batteries, seems like a good idea?

[chrisski]

To me equalization never seems like a good idea with other than FLA batteries.

The one time I equalized my batteries, they were bubbling so much it sounded like a small river. This is the water breaking down. With FLA, you can always add more. AGM you can’t.

The electrolyte in an AGM battery is like a gel. That’s why they can be turned on their side. AGMs shouldn’t vent except at the end of their lifecycle and then it’s time to change them. The gel like electrolyte is also why you just can’t add water to replace it.

If the owners manual says different, follow that.

[velo27]

The whole system is only 3mths old, I really hope things aren't nearing the end of their life cycle, these batteries cost loads

[chrisski]

All you can do is measure them with a multimeter. Other than that, depending on the battery, a local parts store may be able to load test it. If they do, take the results with a grin of salt. The tester is after all built for car batteries.

What’s the lowest you read SOC and how often?

Also could be something else like a bad SCC, but that’s where troubleshooting happens.

[velo27]

All you can do is measure them with a multimeter. Other than that, depending on the battery, a local parts store may be able to load test it. If they do, take the results with a grin of salt. The tester is after all built for car batteries.

What’s the lowest you read SOC and how often?

Also could be something else like a bad SCC, but that’s where troubleshooting happens.

We were awoken about 2am a couple of weeks ago to the inverter alerting us to low battery charge, it was 17%, I assumed the charge controllers job was to protect batteries from these situations... I haven't touched any settings on the controller as I was informed by my supplier (who has zero after sales service) that it came preset...?

[chrisski]

We were awoken about 2am a couple of weeks ago to the inverter alerting us to low battery charge, it was 17%, I assumed the charge controllers job was to protect batteries from these situations... I haven't touched any settings on the controller as I was informed by my supplier (who has zero after sales service) that it came preset...?

I'm pretty sure 17% is too low for AGM. With FLA, the limit is 50%. Lithium you could be fine.

The charge controller normally will not protect the battery. My Victron does have an option to control a relay which I guess you could put in line somewhere to trip a certain voltage, or at least shut off the inverter. Honestly though, my watt hour sucking loads are on the DC side.

The inverters I am familiar with have a low-voltage cut off. Mine is 10.5. Too me, that is much too low for battery health. No inverter I looked at had an adjustable low voltage cutoff.

All I have is a battery monitor which has an audible alarm that will go off at a state of charge I set it to. Has an option for a relay, but I don't use that. I am on my bluetooth many times throughout the day.

My guess is those batteries are toast. With AGMs, the only thing you can do is put test them with a multimeter, put them on a charger, or perhaps a load test at a parts store.

[velo27]

17% is low? OK, but they are deep cycle AGMs... I got no idea... I hope they aren't toast

[velo27]

I've just got a multi meter and tested the batteries, they read at 13.33v & 13.44v @99% charge, being a sunny day...

Going to retest at 50%

[chrisski]

17% is low? OK, but they are deep cycle AGMs... I got no idea... I hope they aren't toast

So I thought AGMs could only go down to 60%.DoD. Google tells me, its 80% DoD. There's a Trojan white paper that says Discharging below 80% DoD could damage internal components. How much at 17%, only 3% below, I don't know.Trojan_QSG_AGM.pdf (trojanbattery.com)

Here is a Trojan AGM Depth of Discharge vs Cylce Chart:

AGM DOD vs Cycles.jpg