Victron battery bank dead after just three seasons, any bright ideas?

[GEM43]

I'd be grateful for any views on the below as I have a problem with our recently installed battery bank. The story is that in January 2022 I installed a new battery bank complete with new Victron Multi 3kw/120A and a Balmar 70A alternator etc. The battery bank comprises 6 x Victron Super Cycle AGM 125ah batteries.

Earlier this summer we had a couple of low voltage alarms, didn't worry too much about it initially as the fridge had been running for four hours overnight. However recently we were out sailing and had further low voltage alarms, something is up. I've extracted from VRM the graph below which covers a 26hr period during which we departed the marina berth (batteries fully charged, shorepower on), then anchored overnight then returned to the marina the next day. Here follows a description of what happened:

06.00 1st October - on marina berth, Multi in Storage mode 13.3v, 0.2A
08.54 - departing berth, engine running, shorepower off, 14.5v, 6.0A
09.15 - engine off, sailing, 13.34v, -4.5A Nav kit drawing power
12.00 - anchoring, engine on 14.4v, 23A Alternator charging
12.30 - anchored, engine off, 13.3v, -0.5A
20.45 - fridge on, 12.66v, -6.0A
21.30 - fridge off, 12.75v, -0.5A
02.00 2nd October - fridge on 12.65v, -6.3A
04.30 - fridge off, 12.66v, -0.5A
08.10 - departing anchorage, engine on, 14.4v, 27.7A
08.32 - Sailing, engine off - 12.88v, -5.5A
10.16 - Sailing, Voltage alarm 12.2v, -6A
11.05 - arrived close to marina, 11.12v, -5.5A
11.33 - arrived marina, engine on 14.3v, 31A
11.54 - on berth, engine off 12.9v, -5A
13.20 - on berth, fridge on 12.0v, -3A
13.30 - on berth, fridge off 12.5v, -0.5A
15.30 - fridge on, 12.3v, -6.6A
15.50 - shorepower reconnected

The above is a bit long-winded (!) but it explains the profile below.



Conclusion? Batteries are knackered. But how can that be? Here is the Victron shunt history which has not been reset since installation:



So the deepest discharge has been 131ah (17.5% of battery bank capacity). Min battery voltage at 10.71v - I don't know when this was, it could have been recently. The max voltage of 15.16v happened very soon after installation when the Balmar regulator was pushing very high voltages immediately after engine start then reducing to 14.8v after a few minutes. I subsequently changed the charge profile so that the max charge voltage was 14.9v.

Today I've had a look at the batteries. They look absolutely fine, no evidence of heating or case distortion. The batteries are temperature monitored to the Balmar and the Victron Multi. In the past 180 days the battery temperature has not exceeded 19deg C.

I have done further tests today. I won't bore you with all the details but in essence I turned the charger off, applied a 28A then a 50A load for a short period then left the batteries with a 5A load, you'll see below that the voltage began to plummet two hours later down to 11.5v.



I disconnected the batteries today to test the voltage of each individual battery, they all seemed pretty much the same, no variation between them.

So, I'd be grateful if anyone has any bright ideas. The future options seem to be new AGMs (Rolls or Lifeline not Victron) or maybe think about LifePo4.

 

[lustyd]

Get a single Fogstar Drift 560Ah or two 300Ah. 10 year warranty and you'll have more usable capacity in less space. LiFePo4 doesn't drop the volts like AGMs do so battery warnings will all but disapear.

That Victron Multi is a big one for your bank both in and out if you drive it hard.

 

[PaulRainbow]

Get a single Fogstar Drift 560Ah or two 300Ah. 10 year warranty and you'll have more usable capacity in less space. LiFePo4 doesn't drop the volts like AGMs do so battery warnings will all but disapear.

That Victron Multi is a big one for your bank both in and out if you drive it hard.

He's got 750ah ! He could run it flat out for an hour and have a bit to spare (not that you would) !

 

[KompetentKrew]

The batteries are knackeed because you've run them absolutely flat - down to 11.12V on 2nd October and 10.71V according to the shunt's history.

That is the obvious answer to your question.

The batteries are not dead because Victron make naff batteries - any lead-acid or AGM battery would be killed by this kind of abuse.

The real question is why you allowed them to run so flat - if it's because the SmartShunt was showing the wrong percentage of discharge then that can be caused by a couple of things. You could have set the battery capacity incorrectly, for example - telling it you have 7500Ah of batteries when in fact you have 750Ah (which is still a lot, by the standards of most people here).

It was particularly easy to miscalibrate the SmartShunt until a firmware update which was released about a year ago - previously there was a setting which would reset the Shunt's reading to 100% if the battery was disconnected. So discharge the battery to 50%, disconnect the battery cable, reconnect and the SmartShunt shows 100% even though the batteries only have 50% charge.

Or the SmartShunt could be incorrectly installed, and is not monitoring the discharge of some of your load.

But this is a very large battery bank - I can run my small fridge for days on my 330Ah battery bank without getting below 50% (although I have a small amount of solar too). It could be that you damaged or knackered your batteries ages ago, and have been running with a much reduced battery capacity for a long time.

Maybe it was the 15V pumped out by the alternator that damaged them? I don't know how much overcharging / overvoltage would cause damage. But I guess you ran them like that for some hours, so it seems possible?

 

[Boater Sam]

Insufficient charging. Allowed to go too low and not fully recharged straight away.
Never fully charged due to insufficient charging time.

Result, sulphated batteries.

 

[GEM43]

The batteries are knackeed because you've run them absolutely flat - down to 11.12V on 2nd October and 10.71V according to the shunt's history.

That is the obvious answer to your question.

The batteries are not dead because Victron make naff batteries - any lead-acid or AGM battery would be killed by this kind of abuse.

The real question is why you allowed them to run so flat - if it's because the SmartShunt was showing the wrong percentage of discharge then that can be caused by a couple of things. You could have set the battery capacity incorrectly, for example - telling it you have 7500Ah of batteries when in fact you have 750Ah (which is still a lot, by the standards of most people here).

It was particularly easy to miscalibrate the SmartShunt until a firmware update which was released about a year ago - previously there was a setting which would reset the Shunt's reading to 100% if the battery was disconnected. So discharge the battery to 50% disconnect the battery cable, reconnect and the SmartShunt shows 100% even though the batteries only have 50% charge.

Or the SmartShunt could be incorrectly installed, and is not monitoring the discharge of some of your load.

But this is a very large battery bank - I can run my small fridge for days on my 330Ah battery bank without getting below 50% (although I have a small amount of solar too). It could be that you damaged or knackered your batteries ages ago, and have been running with a much reduced battery capacity for a long time.

Maybe it was the 15V pumped out by the alternator that damaged them? I don't know how much overcharging / overvoltage would cause damage. But I guess you ran them like that for some hours, so it seems possible?

Yes maybe the overcharging was the cause of the problem, likewise I don't know how quickly a battery would be damaged by 15.16v.

 

[GEM43]

Insufficient charging. Allowed to go too low and not fully recharged straight away.
Never fully charged due to insufficient charging time.

Result, sulphated batteries.

Batteries constantly charged by the Multi when on marina berth. Only not charging when away from the berth when solar is deployed. Voltage constantly monitored via the shunt and a battery Voltage monitor. Normally in storage mode at 13.2v.

 

[Sandy]

At 1100 what is drawing 55 amps?

 

[GEM43]

At 1100 what is drawing 55 amps?

Inverter supplying a 240v device.

 

[GEM43]

He's got 750ah ! He could run it flat out for an hour and have a bit to spare (not that you would) !

And separate bank for Thruster/Windlass. Engine start is independent of course and then another battery for 4kw generator start.

 

[B27]

The batteries are knackeed because you've run them absolutely flat - down to 11.12V on 2nd October and 10.71V according to the shunt's history.
......

They must have been knackered before then to get to that low a voltage from 'fully charged' a day before, with a mixed day of sailing motoring and light domestic loads.
Egg, Chicken.

Even completely discharging a battery should not kill it instantly, typically batteries might survive ~100 cycles of deep discharge but 1000 cycles of 50% discharge or something roughly like that.

The 10.7V lowest low might be while running the inverter, so it may not actually indicate a particularly low SOC.

I wonder if there is some conflict between the Balmar and Victron stuff, resulting in one or other over or under charging?
One or other could be faulty?
Possibly the batteries are not actually fully charged?
Could it be worth forcing a long period at 14.4V and monitoring the current?

 

[GEM43]

Could it be worth forcing a long period at 14.4V and monitoring the current?

Interesting thought; I had wondered about running an equalisation routine. The Victron Super Cycle batteries are designed to cope with multiple discharges below 50% SOC without damage though I doubt they've been below 80% SOC since they've been fitted.

I hear those that say the batteries are dead flat because of the voltages shown, but therein lies the mystery as these very low voltages have only occurred very suddenly and recently when immediately prior the shunt (SOC) and separate voltage monitoring suggest full batteries in storage mode.

 

[vas]

I'd go with B27 suggestion, force charge them for a day and see what happens.
the fact that charging goes to store mode doesn't mean they are full. I'd also do a equalisation routine (or three!)
if they are buggered, they are not going to get any worse, they just may not been fully charged for months and system thinks they are...

 

[noelex]

On the four right hand charging events the absorption time is too short, as evidenced by high current acceptance when the absorption phase ends. This may have been limited by the available charge current, but it is something you should check before installing new batteries.

 

[lustyd]

He's got 750ah ! He could run it flat out for an hour and have a bit to spare (not that you would) !

He has 750Ah nominal capacity at 12V accross 6 batteries, but realistically that's 375Ah if he's feeling lucky and maybe 300Ah if he wants his batteries to last more than a couple of years. With standard discharge that should be about 31 Amps for the bank over 24h for lead.
The multi installed can suck 41.6A per battery and push 20A per battery. For a few minutes that's fine, but if using the full capacity regularly I'd expect the batteries to suffer a bit.

 

[GEM43]

Commenced an equalisation charge:

 

[noelex]

He has 750Ah nominal capacity at 12V accross 6 batteries, but realistically that's 375Ah if he's feeling lucky and maybe 300Ah if he wants his batteries to last more than a couple of years. With standard discharge that should be about 31 Amps for the bank over 24h for lead.
The multi installed can suck 41.6A per battery and push 20A per battery. For a few minutes that's fine, but if using the full capacity regularly I'd expect the batteries to suffer a bit.

At full output the inverter is only drawing a little over 0.3C. That should not be taxing for an AGM battery bank.

 

[lustyd]

At full output the inverter is only drawing a little over 0.3C. That should not be taxing for an AGM battery bank.

and yet, here we are My point was that you'd want to be careful not to run it at full chat too long.

 

[GEM43]

Maybe it was the 15V pumped out by the alternator that damaged them? I don't know how much overcharging / overvoltage would cause damage. But I guess you ran them like that for some hours, so it seems possible?

If that was the case an Equalisation charge would kill the batteries too?

 

[lustyd]

Commenced an equalisation charge:

View attachment 183924

on an AGM?