Batteries not holding Voltage

[Amaranth]

I have a bank of 5 x 170ah Victron AGM Super Cycle batteries. ie 850ah House set. I installed 18 months ago and size, charging capacity etc are all sized to work in accord with general sizing parameters. This is a replacement bank after 8 years of good service from my last AGM set.

I selected the Super cycles because they are claimed to be designed for applications where 60 to 80% discharge can be expected.

Has worked well for 18 months however, of late once the SOG drops by approx 20% the voltage begins to drop off dramatically and when any load is placed on the system from an invertor for example the voltage drops to circa 9.5 volts and all sorts of challenges arise. ie my bank claims to have 650ah available but voltage is falling off.

I have disconnected and tested each battery individually and each show a range of 12.5 to 12.9 volts - this is with no load.
My next thought is to get a load tester and load test each battery individually.
It has been recommended that possibly a super charge (16v) should be applied for a couple of hours to equalize the bank.
I am concerned by such radical intervention is needed after such a relatively short period of time and if could cause long term damage.
Does any body have any thoughts or solution suggestions?
Many Thanks

[Simi 60]

Still under warranty
Contact supplier

[s/v Jedi]

It sounds like your batteries are never fully charged.

[ranger58sb]

Originally Posted by Amaranth

I have disconnected and tested each battery individually and each show a range of 12.5 to 12.9 volts - this is with no load.

My next thought is to get a load tester and load test each battery individually.

It has been recommended that possibly a super charge (16v) should be applied for a couple of hours to equalize the bank.

I'd guess the range of 12.5 (for some batteries) to 12.9 (for others) might suggest that those showing lower voltage haven't been (or at least aren't) fully charged. Or have lost some capacity. I think I'd be looking for 12.8-12.9 for all of them.

A load test might discover correlation between lower-voltage batteries (~12.5) and load capability. If so, that might give you info that would be useful for discussing warranty issues with Victron.

I don't think I'd want to try equalizing unless that's something Victron recommends. I thought Lifeline was the only AGM maker that supports "conditioning" for their AGMs?

-Chris

[pcmm]

How are you testing the batteries? Ideally if you're trying to determine if a battery is bad, you want to fully charge them, then disconnect them from everything (including each other) and let them sit overnight and get a voltage reading in the morning.

[tkeithlu]

I still occasionally use an old-fashioned load tester, but I've got one of these now, and it gives much more sophisticated information about battery condition. You punch in the type battery and its capacity, usually CCA, and it tels you the rest. It will also test your charging circuit, and that looks like it would be wise in your situation.

https://www.amazon.com/KONNWEI-100-2...TESTING_DEVICE

[boat driver]

sounds like 1) not getting fully charged 2) possibly one is bad and therefore dragging bank down.
Assure that the capacity output of your charger time equals the capacity input the bank needs. IE, if the capacity is 600 ah batteries and the discharge is 300ah, and the charger output is rate at 100ah , a Minimum of 3 hours charge is needed to begin to fully charge.
Mentioning discharging beyond the old parameters- is the charging also extended as well?

[SV__Grace]

Originally Posted by Amaranth

I have a bank of 5 x 170ah Victron AGM Super Cycle batteries. ie 850ah House set. I installed 18 months ago and size, charging capacity etc are all sized to work in accord with general sizing parameters. This is a replacement bank after 8 years of good service from my last AGM set. I selected the Super cycles because they are claimed to be designed for applications where 60 to 80% discharge can be expected.

I wouldn't expect AGMs to handle more than 50% discharge, what does your manual say about that?

We had a 1200ah bank of new Mastervolt AGMs and like you, after less than 2 years our voltage kept dropping below 12v after 70% or so. I disconnected the batteries, tested their voltage, did a load test, let them sit and tested again, to find that one battery was bad while the others did fine, so disconnected that battery and babied the battery bank until our recent upgrade to Lithium.

I'm pretty sure that I created the problem by not charging the batteries to 100% often enough. It just pained me to run the generator for 2 hours in bulk (@80 charging amps), 2 hours in absorption (@20 charging amps) and 4-6 hours in float (@8-10 charging amps) to get them to 100% but after I started doing so the batteries lasted another 2 years until I swapped them out.

AGMs seemed like a good idea for cruising, but in reality they seem best if you have frequent access to shore power to get them to 100%.

[SaltyMetals]

Amaranth,
There are many more guys on CF who can give you good advice on batteries than me. I note you have Victron batteries. If you have a Victron MPPT it will have an equalisation mode and i think this runs as a default once a month but you can trigger it manually if you wish. But as the others say, you should check each individual battery when disconnected first to see if you have one that has failed. Might have become quite hot and most probably is sucking out the charge from the others. My point being that i think you can safely run the equalisation since this is foreseen by Victron. Maybe the others can correct me if i am wrong.
Andrew

[Emouchet]

Originally Posted by SV__Grace

AGMs seemed like a good idea for cruising, but in reality they seem best if you have frequent access to shore power to get them to 100%.

I second that. If your AGM batteries has not been fully charged via shore power every 10/15 cycles, they are most probably cocked. This is what I hate the most about AGM. Those are really sensitive and requires regularly a good full charge from shore power. Something people do not take into consideration often, and to me, does not match with long term off grid.

I would try to isolate every battery, and charge them individually, rather than the whole bank. Same for equalization. it should be run battery by battery. End equalization when either the batterie lost energy by heat dissipation (battery becomes warner) or the eq voltage has been reached (measured at the battery post).

[more]

Originally Posted by Amaranth

I have a bank of 5 x 170ah Victron AGM Super Cycle batteries. ie 850ah House set. I installed 18 months ago and size,
Does any body have any thoughts or solution suggestions?
Many Thanks

Immediately call your dealer and claim a warranty. yes this is lot work but you invest almost 2500€ in a battery. Demand paper of capacity test or make your temporary by for example this.
https://www.aliexpress.com/item/1005...:%223339%22%7D

[SaltyMetals]

I have 4 x 110Ah Victron AGM's for the services and have 1 x 150W solar (+another 1x 150W solar in the summer on the bimni) as well as a Rutland 400 windcharger, all connected to the batteries vis MPPT controllers. I might be wrong, but even when i am away from the boat and there is only 1x 150W solar + the windgen I reckon that this is enough to run the only remaining item which is a small dehumidifier running off the inverter. My system seems to survive and regularly shows 100% SOC when i get back to the boat. I know the solar is not so good in the winter but think the windgen then makes up for that with stronger winds in the winter. So hope my batteries do get fully recharged each time there is enough sun/wind.
Andrew

[Morequestions]

Is the bank of batterys by chance hooked up to anything that can drain them? Such as a alternator or other item whose diodes gone bad without effecting charging but become a drain when not charging?

[chasfgr]

My guess is that batteries are never charged as the cut-off is occuring early.
Experience is that in 90% cases it's chrger malfunction, not all your batteries dying at once.

[Sailmonkey]

Originally Posted by chasfgr

My guess is that batteries are never charged as the cut-off is occuring early.
Experience is that in 90% cases it's chrger malfunction, not all your batteries dying at once.

I wouldn’t call it malfunction. More likely improperly programmed, or not programmable to acceptable charging durations.