Is my Renogy battery cooked?

[tvd1]

I have a sealed AGM Renogy 100ah battery thats been in service for a year in an outdoor shed. Its not in terrible shape but I have accidentally let the charge level dip as low as 30%. So today when hooked up to solar, it will charge up to 100%, but as soon as the light source disappears it immediately goes down to 60% with no load on it. Now that the days are so short even with a very light load it rarely goes above 55% at night. I assumed this battery may be trash but I read a few things how batterys can be renewed by people that know what they are doing (not me, lol). I reached out to a local battery provider to see what they say but wondering what others have done. Thanks

Deep Cycle AGM Battery 12 Volt 100Ah

Renogy’s 12V Deep Cycle AGM Battery is an excellent choice for standby or daily power needs. Limited time sale, 10% off: Renogy10off. Free shipping

www.renogy.com

 

[tvd1]

To follow up, i do have a tender and charger i've used.. will this fix it?

https://www.harborfreight.com/21050-amp-12v-manual-charger-with-engine-start-59424.html?ccdenc=eyJjb2RlIjoiNzI1NzczMDgiLCJza3UiOiI1OTQyNCIsImlzIjoiMzkuOTkifQ%3D%3D

Battery Tender® Plus 12V, 1.25 AMP Battery Charger

www.batterytender.com

also, i know the percentages based on my Solar controller - A Renogy Rover 30A

 

[tvd1]

bumping this back to see if anyone has any ideas...

 

[Tomthumb62]

also, i know the percentages based on my Solar controller - A Renogy Rover 30A

You will want to COMPLETELY ignore those percentages. They are useless. You need a real battery monitor like the Victron Smartshunt to measure actual state of charge.

Edit: you can measure state of charge via battery voltage for AGM, but you can’t rely upon the Renogy Rover built in voltage readings. They’re either 0.2v too high or low, I can’t remember. And besides, if your battery is in a system, it’s not going to show you resting voltage anyways. Resting voltage is what you want.

 

[MisterSandals]

but I have accidentally let the charge level dip as low as 30%

What voltage was this?

 

[Benjamin Yang]

For batteries that have not been deep-charged for a long time, attempt to deep-charge them. Using a suitable charger, charge the battery to 100% and hold it for a period of time to help restore its capacity.

 

[Crowz]

As mentioned the voltage readings are the key to knowing what is going on.

When its showing full you need to disconnect the battery and read the voltage after it has been disconnected for say 5 minutes. Let us know what it shows for volts.

The other real handy data would be to catch it at 55% or so and disconnect it and wait 5 min and get a reading.

Those two readings will allow us to tell you what the batteries actual state of charge is.

Also as mentioned short of getting something like a victron smart shunt and using that for your readings your out of luck for actual state of charge on the fly so to speak. I use one of those on one setup and a renogy display/shunt on another. The victron seems more accurate than the renogy but the renogy is "close enough for government work" as my stepdad would say.

 

[tvd1]

Okay, great info.. I'll disconnect at 100% and at 55% (it regularly dips to 55 as soon as the sun goes down). I have a multimeter but dont think i have the budget for a $130 bluetooth battery reader, unless someone has any more reasonable alternatives.

 

[Tomthumb62]

Okay, great info.. I'll disconnect at 100% and at 55% (it regularly dips to 55 as soon as the sun goes down). I have a multimeter but dont think i have the budget for a $130 bluetooth battery reader, unless someone has any more reasonable alternatives.

The % readings are COMPLETELY USELESS on your Rover. You don’t need a battery monitor per se, but you must ignore the Rover. Ignore it’s voltage readings too, those aren’t accurate either.

Once it says 100%, disconnect the battery from the system and wait 30 minutes to 24 hours. Longer is more accurate. Then measure the voltage at the battery terminals with your multimeter. What does it say?

Then we can help you find out what voltage 55% is.

Source: I used to have AGM batteries and the Renogy Rover 30A MPPT.

 

[Crowz]

The % readings are COMPLETELY USELESS on your Rover. You don’t need a battery monitor per se, but you must ignore the Rover. Ignore it’s voltage readings too, those aren’t accurate either.

Once it says 100%, disconnect the battery from the system and wait 30 minutes to 24 hours. Longer is more accurate. Then measure the voltage at the battery terminals with your multimeter. What does it say?

Then we can help you find out what voltage 55% is.

Source: I used to have AGM batteries and the Renogy Rover 30A MPPT.

5 minutes should be close enough for him to have an idea what he is dealing with. He is going have to get a real shunt and meter to know his soc anyways but this will show him how bad off the rover really is

 

[MisterSandals]

but dont think i have the budget for a $130 bluetooth battery reader, unless someone has any more reasonable alternatives.

I think estimating SoC with AGM batteries based on voltage is pretty straightforward.
I recommend keeping track of resting battery voltage and seeing if it corresponds to this chart to where you can estimate SoC reliably.

After a few days, you'll likely know the SoC at a glance. If not, then consider a meter of some sort.

 

[tvd1]

Okay, Renogy MPPT read 100%, i disconnected. Let sit for 30 mins.. and read 12.49. I hooked up a battery charger to it and it went to green right away (full).

 

[MisterSandals]

I hooked up a battery charger to it and it went to green right away (full).

Is the needle dial on the charger pegged to 100%? I cannot tell how far it can go for 100%.

How are you connecting the charger to the battery posts? Cheesy alligator clips? A bad connection might be fooling your charger into thinking the battery is not accepting the 10A charge thinking its near full.
I wonder if good ring terminals would produce different results.

The chart (and my gut) says your battery is about 80% full. What happens if you try a gentle 2A charge?
If your charger is single stage 10A, a gentle finish charge might put in a better charge (closer to 13.0V as seen on the chart).

 

[Crowz]

Now put the charger on 2 amps and leave it for a few hours and then do a 5 or 10 minute rest off the charger and see what it reads volts wise.

If it climbs its still not fully charged. I'm not a fan of most of todays "smart chargers" when it comes to lead acid batteries.

I use a charger from a company called pulsetech for my lead acid stuff. Does amazingly well at reviving lead acid batteries. The oldest ones I still have in use are around 17 years old now and have been maintained by the pulsetech chargers. The military uses the same chargers on their tanks and stuff.

 

[tvd1]

Is the needle dial on the charger pegged to 100%? I cannot tell how far it can go for 100%.

How are you connecting the charger to the battery posts? Cheesy alligator clips? A bad connection might be fooling your charger into thinking the battery is not accepting the 10A charge thinking its near full.
I wonder if good ring terminals would produce different results.

The chart (and my gut) says your battery is about 80% full. What happens if you try a gentle 2A charge?
If your charger is single stage 10A, a gentle finish charge might put in a better charge (closer to 13.0V as seen on the chart).

Yea its as far over as it goes and the green light is on. I'm not sure what would happen if i left it on for a long time, because i would assume the charger would auto-turn off (smart charger)? Its just a Harbor Freight one, so i'm not sure how advanced it is. I'll have to look at those pulsetech ones.

 

[Tomthumb62]

Now put the charger on 2 amps and leave it for a few hours and then do a 5 or 10 minute rest off the charger and see what it reads volts wise.

If it climbs its still not fully charged. I'm not a fan of most of todays "smart chargers" when it comes to lead acid batteries.

I use a charger from a company called pulsetech for my lead acid stuff. Does amazingly well at reviving lead acid batteries. The oldest ones I still have in use are around 17 years old now and have been maintained by the pulsetech chargers. The military uses the same chargers on their tanks and stuff.

I looked up PulseTech chargers. Their 4A model is $100. The next model up is their 16A model for over $700!! That’s an expensive charger!

Lead acid batteries need such specialized charging that of course there’s a market for such expensive chargers. If it really did work to extend the life of a lead acid battery 3x , it would pay for itself quickly, but since this is the first I’ve heard of them, my skeptical side will put them in the category of snake oil until I learn more about them. But my interest is piqued nonetheless!

 

[Crowz]

I looked up PulseTech chargers. Their 4A model is $100. The next model up is their 16A model for over $700!! That’s an expensive charger!

Lead acid batteries need such specialized charging that of course there’s a market for such expensive chargers. If it really did work to extend the life of a lead acid battery 3x , it would pay for itself quickly, but since this is the first I’ve heard of them, my skeptical side will put them in the category of snake oil until I learn more about them. But my interest is piqued nonetheless!

The 4 amp is all you need. Think of it as a repair tool/trickle charger. The ones I used all of these years was the 1.2 or whatever it was amp model. Its replaced by the 4 amp version now.

You wouldn't use it to rapid charge things. I have their quad link rotating module which allows you to hook each charger to 4 different batteries/vehicles and it rotates to a different connection every 20 minutes.

 

[Crowz]

I looked up PulseTech chargers. Their 4A model is $100. The next model up is their 16A model for over $700!! That’s an expensive charger!

Lead acid batteries need such specialized charging that of course there’s a market for such expensive chargers. If it really did work to extend the life of a lead acid battery 3x , it would pay for itself quickly, but since this is the first I’ve heard of them, my skeptical side will put them in the category of snake oil until I learn more about them. But my interest is piqued nonetheless!

Oh on the snake oil part I fully agree its something to worry about. These work though but its easy to see them in action to know they do what they claim if you have an old battery. All you have to do it connect it to an old battery that you can see down into to observe the cells. After 30 minutes you will normally start seeing things floating up. The worse the batteries are sulfinated the faster and more pronounced the bits floating up will be.

It works so well in fact it can actually stop a very bad battery from working at all when the chunks resettle down on the plates. Used on a regular bases and it shouldn't be a problem. The batteries in my superduty truck are over 16 years old and I think about 17 years old now and still work great. Ive used the chargers to bring back bad batteries to a useful level quite a few times for myself and others. I try not to mention to local people anymore since it got a bit out of hand with people wanting me to "fix" their batteries.

Of course no one wanted to fork out the money to get their own charger but they were more than happy to visit me to get me to use my chargers on their batteries for them

 

[Tomthumb62]

Oh on the snake oil part I fully agree its something to worry about. These work though but its easy to see them in action to know they do what they claim if you have an old battery. All you have to do it connect it to an old battery that you can see down into to observe the cells. After 30 minutes you will normally start seeing things floating up. The worse the batteries are sulfinated the faster and more pronounced the bits floating up will be.

It works so well in fact it can actually stop a very bad battery from working at all when the chunks resettle down on the plates. Used on a regular bases and it shouldn't be a problem. The batteries in my superduty truck are over 16 years old and I think about 17 years old now and still work great. Ive used the chargers to bring back bad batteries to a useful level quite a few times for myself and others. I try not to mention to local people anymore since it got a bit out of hand with people wanting me to "fix" their batteries.

Of course no one wanted to fork out the money to get their own charger but they were more than happy to visit me to get me to use my chargers on their batteries for them

Thanks for that review. I have a NOCO 3.5A maintainer but it cannot charge up a dead battery so it’s useless in that regard. Can this 4A model recharge an over discharged lead acid? Or is it simply to keep it topped off?

 

[Crowz]

Thanks for that review. I have a NOCO 3.5A maintainer but it cannot charge up a dead battery so it’s useless in that regard. Can this 4A model recharge an over discharged lead acid? Or is it simply to keep it topped off?

The 1.2amp charger would actually recharge any lead acid battery it just takes longer. The 4amp one will charge one back up fairly fast. The repair part and the charge time are not really connected since how long it takes to "fix" a battery depends on how bad off it is not how charged it is if that makes sense.

But yes the 4amp one charges a battery back up overnight easily from my experience with it.