1.7V on AGM - replace?

[SY_Maria]

An undocumented load killed 2x165AH victron AGMs while the the boat was unattended for 2 weeks with main power kill switch off.
The batteries charged back from 1.7V to 13.3V overnight by Victron centaur 50A charger connected to shore power.
I'm going to disconnect the batteries and check for dead cells in either of them by monitoring voltage drop while they are disconnected.
2 questions - how to check if the batteries are still good and hold the charge? And - up from such a dead low drain, is there any hope or I'd better change the batteries to be on a safe side?

[double u]

maybe try such a loadtester
http://images.autoserviceprofessiona...ristie-CT3.jpg

[smac999]

charge them up good then do a c20 test on them. that is the best and only real way to test battery capiticy.

[Sternwake]

Use the batteries as you would away from shore power, monitor voltage during discharge.

It will be obvious if they have usable capacity left or not. Either the voltage will tank under regular loads, or it will be acceptable.

Give them another 50 amp Victron recharge after the overnight load test and see if they perform any better during the next load test.

They did lose some amount of usable capacity, with such treatment, drained to 1.7v.

I'd not expect them to do well, but they might be OK for some lighter cycling, or just starting duty.

[SY_Maria]

Thank you everybody for your replies!
I fully charged the batteries using Victron AGM (up to 14.7V) charger and the put them to load - fridge, navigation and 2 chart plotters, and lights (LED) in the cabin. They lasted only 6 hours and by the end of the 6th hour they had less then 25% left in them, with 12.3V.
That's way to little compared to normal I saw before I fried them.
So replacing them with new AGMs is my number 1 option now.
Oh, well. Easy come, easy go...

[Paul L]

Where do you get less than 25% left at 12.3v? 12.3v should be considerably higher than that. Victron has that at about 1/3 discharged, ie 2/3rds charged.

[a64pilot]

Can you equalize these batteries?


Sent from my iPad Pro using Cruisers Sailing Forum

[SY_Maria]

PaulL, that's what my Solara controller is showing and it is in agreement with Wurst panel. This voltage is under load so not accurate free-standing measurement. I did notice that they drained noticeably faster than before this mishap so I'll change them. I'll be doing some autonomous sailing this winter in the Med so I want to be confident in my systems for peace of mind.

[DeepFrz]

What was the current from the battery charger at the time you shut it off and began the "load test"?

[Paul L]

Originally Posted by SY_Maria

PaulL, that's what my Solara controller is showing and it is in agreement with Wurst panel. This voltage is under load so not accurate free-standing measurement. I did notice that they drained noticeably faster than before this mishap so I'll change them. I'll be doing some autonomous sailing this winter in the Med so I want to be confident in my systems for peace of mind.

If there were no charging sources, such as solar on, then your 12.3v is not 75% discharged as you say your controllers say.

[SY_Maria]

It was none, DeepFrz. Victron charger topped these batteries to 14.7V overnight and disconnected.

[svlamorocha]

Originally Posted by SY_Maria

Thank you everybody for your replies!
I fully charged the batteries using Victron AGM (up to 14.7V) charger and the put them to load - fridge, navigation and 2 chart plotters, and lights (LED) in the cabin. They lasted only 6 hours and by the end of the 6th hour they had less then 25% left in them, with 12.3V.
That's way to little compared to normal I saw before I fried them.
So replacing them with new AGMs is my number 1 option now.
Oh, well. Easy come, easy go...

How do you onow that you "fully"charged the batteries?

Only way to be 100% sure is to keep them at the absorption voltage that ios recommended by the battery manufacturer (say 14.5V plus/minus temp comp) not until the charger decides to switch to float (which 99% of the time is too soon) but until the current going into the batteries (in amps) is equal to teh battery capacity in Ah divide by 200. This may require you to reboot teh charger to restart the absorption timer.

Cheers
C

[SY_Maria]

How do I restart Victron? Switching it on and then off once it switched to float and then back on doesn't make it go into charge mode again

[Sternwake]

Trick charger by loading batteries until voltage falls below 12.6v then restart charger and remove loads.

If charger sees more than 12.8v or so it assumes batteries are full and chooses float voltage, instead of seeking 14.x volts at maximum output.

[a64pilot]

I know nothing of this charger, but on a programmable one, you can also trick it by making float and absorption voltage the same.
Full charge is indicated by acceptance rate in amps, on my Lifelines it .5% of AH capacity, so for my 660 AH bank it's not fully charged until at absorption voltage the amperage is 3.3 amps.
That is Lifelines, your batteries I'm sure may be different but the manual for them ought to tell you what defines a full charge, go with your batteries manual whatever it says.

I asked if these batteries and be equalized, cause if I drew my lifelines down that low, after a full charge and allowing them to cool I believe I'd equalize them to try to recover lost capacity.
Course not all AGMs can be equalized


Sent from my iPad Pro using Cruisers Sailing Forum