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

[GEM43]

If you don't do something you're not going to get anywhere. How have you jumped to the "duff battery" ? What charger settings are you using ? How are you setting the Multi settings ?

Yes, I appreciate the need to delve deeper. Slightly put off by the Victron dire warnings if their configuration tool is used by a layman "trained professional only" it says. The duff battery conclusion is consequent of an engineer applying a battery tester this morning which identified one of the six as being well below the specification of the other five.

 

[Bobc]

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.

View attachment 183901

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

View attachment 183899

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.

View attachment 183900

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.

I've just had exactly the same happen with 3 x Victron gel 110ah batteries, which are only 3 years old.

My conclusion is that they are over-priced rubbish.

 

[vas]

I've just had exactly the same happen with 3 x Victron gel 110ah batteries, which are only 3 years old.

My conclusion is that they are over-priced rubbish.

I'd generalise that into "something in the whole charge/discharge/configure path is rubbish"
Don't disagree with overpriced, but don't think their batteries are rubbish.

[\hides]

 

[PaulRainbow]

Yes, I appreciate the need to delve deeper. Slightly put off by the Victron dire warnings if their configuration tool is used by a layman "trained professional only" it says.

Victron Connect with a MK3 interfase is safe enough to use, unless you're careless. First thing to do is save current settings, then you can always revert to them if you do get in a muddle. You really do need to see what the Multi is doing.

The duff battery conclusion is consequent of an engineer applying a battery tester this morning which identified one of the six as being well below the specification of the other five.

Ah, didn't see mention of that.

 

[dje67]

3 years ago I fitted 5 Leoch LDC 115 lead carbon batteries to my yacht. After a year and a half that bank completely failed on me - after a few nights at anchor using no more than about 150Ah, any significant load on the bank resulted in voltage collapsing towards 11V. The batteries spent nearly all their life on shore power using a multistage charger configured very close to the (at that time) data sheet and never had more than 200Ah pulled from them and I reckon they had no more than 100 cycles of around 100Ah. Leoch suspected over-charging - alternator was at 14.7V, Sterling charger was 14.7V Abs, 13.5V float.

A new bank was fitted a year ago and has failed in exactly the same way. They have had no more than a couple of cycles of 200Ah plus around 80-100 cycles of <100Ah, and are kept permanently on shorepower fed from a new EasySolar 12/1600/70 Which, once it has completed its 14.4V AGM charge cycle (bulk/absorption/float) holds its output at 13.2V, with a refresh absorption top-up every week (the standard Victron AGM profile). Alternator was changed to a 14.4V, 100A unit. So, I've no charge source giving more than 14.4V, so the 2nd bank failing was unlikely to be over-charging.

I did a bit of playing around with the bank. Separated the bank into the 5 individual batteries and ran each one on a 60A load via the inverter (fairly brutal...). Data sheet for the battery says there should around an hour and a half reserve time at that load on a single battery. One battery managed 22Ah before crashing, the other four were around 10Ah...! So, all knackered equally badly. Once the load was off each battery, within around 15 mins they had all recovered to nearly 12.8 - 12.9V across their terminals.

When I'm motoring, the Starter battery is always also in-circuit to the alternator and seeing up to 14.4V, so I did a capacity test on that to see how it has faired on the same use-profile. That single Leoch XR1750 AGM has outlasted both the LDC banks and some (nearly 4 years old, but obviously never really deep-cycled). On a 60-65A load it was still holding up at 11.0V after an hour. The voltage profile compared to the datasheet for that battery matched perfectly against how it should perform when new - in fact the time to reach 11V exceeded that quoted for a 50A load profile. So, it looks like that battery is in perfect condition, especially given its age. When on shorepower, longer term, the starter battery is completely disconnected from the house bank and Victron - it really only ever sees charge from the alternator. So, I'm going to discount my alternator as being the issue on my boat as the starter battery has seen as many hours as the house bank when motoring.

So, I've no idea whether I've undercharged or overcharged my 1st and 2nd banks, but I put this info out there in case others, including the OP have been equally stung by AGMs (lead carbons in my case) being trashed by my style of boat usage and means of charging them.

The next bank is LiFePO4 hybrid - not touching AGMs again...! The price difference is now relatively small between the technologies.

 

[Bobc]

I think a lot of modern batteries are just rubbish, no matter how much you pay.

 

[Plum]

I think a lot of modern batteries are just rubbish, no matter how much you pay.

Not in my experience. Usually get 8 years from lead-acid batteries which I regard as very good. Are you expecting a longer life?

 

[GEM43]

3 years ago I fitted 5 Leoch LDC 115 lead carbon batteries to my yacht. After a year and a half that bank completely failed on me - after a few nights at anchor using no more than about 150Ah, any significant load on the bank resulted in voltage collapsing towards 11V. The batteries spent nearly all their life on shore power using a multistage charger configured very close to the (at that time) data sheet and never had more than 200Ah pulled from them and I reckon they had no more than 100 cycles of around 100Ah. Leoch suspected over-charging - alternator was at 14.7V, Sterling charger was 14.7V Abs, 13.5V float.

A new bank was fitted a year ago and has failed in exactly the same way. They have had no more than a couple of cycles of 200Ah plus around 80-100 cycles of <100Ah, and are kept permanently on shorepower fed from a new EasySolar 12/1600/70 Which, once it has completed its 14.4V AGM charge cycle (bulk/absorption/float) holds its output at 13.2V, with a refresh absorption top-up every week (the standard Victron AGM profile). Alternator was changed to a 14.4V, 100A unit. So, I've no charge source giving more than 14.4V, so the 2nd bank failing was unlikely to be over-charging.

I did a bit of playing around with the bank. Separated the bank into the 5 individual batteries and ran each one on a 60A load via the inverter (fairly brutal...). Data sheet for the battery says there should around an hour and a half reserve time at that load on a single battery. One battery managed 22Ah before crashing, the other four were around 10Ah...! So, all knackered equally badly. Once the load was off each battery, within around 15 mins they had all recovered to nearly 12.8 - 12.9V across their terminals.

When I'm motoring, the Starter battery is always also in-circuit to the alternator and seeing up to 14.4V, so I did a capacity test on that to see how it has faired on the same use-profile. That single Leoch XR1750 AGM has outlasted both the LDC banks and some (nearly 4 years old, but obviously never really deep-cycled). On a 60-65A load it was still holding up at 11.0V after an hour. The voltage profile compared to the datasheet for that battery matched perfectly against how it should perform when new - in fact the time to reach 11V exceeded that quoted for a 50A load profile. So, it looks like that battery is in perfect condition, especially given its age. When on shorepower, longer term, the starter battery is completely disconnected from the house bank and Victron - it really only ever sees charge from the alternator. So, I'm going to discount my alternator as being the issue on my boat as the starter battery has seen as many hours as the house bank when motoring.

So, I've no idea whether I've undercharged or overcharged my 1st and 2nd banks, but I put this info out there in case others, including the OP have been equally stung by AGMs (lead carbons in my case) being trashed by my style of boat usage and means of charging them.

The next bank is LiFePO4 hybrid - not touching AGMs again...! The price difference is now relatively small between the technologies.

Well that is very interesting indeed with close parallels to my experience. I’ll respond in more detail tomorrow but I’ll just mention that I’m a supporter of AGM technology as I had sixteen years of excellent service from Lifeline AGMs in my previous boat, they were still going strong when I sold the boat. Thanks for your detailed reply.

 

[B27]

3 years ago I fitted 5 Leoch LDC 115 lead carbon batteries to my yacht. After a year and a half that bank completely failed on me - after a few nights at anchor using no more than about 150Ah, any significant load on the bank resulted in voltage collapsing towards 11V. The batteries spent nearly all their life on shore power using a multistage charger configured very close to the (at that time) data sheet and never had more than 200Ah pulled from them and I reckon they had no more than 100 cycles of around 100Ah. Leoch suspected over-charging - alternator was at 14.7V, Sterling charger was 14.7V Abs, 13.5V float.
....

14.7 is quite high for an absorption charge.
It also matters how often your batteries are subjected to this charge, and how the charger decides to go to float.

Many yachts seem to have chargers which whack up the volts because a load is drawn, which the charger is powering.
So it's easy for a fully charged battery to see many hours of completely unwanted absorption charging.

I have a Leoch battery on a small electric start motorbike.
It's 9 years old and has survived abuse and neglect .
I probably bought it because I didn't expect to keep the bike and it was cheaper than Yuasa.

 

[B27]

I think a lot of modern batteries are just rubbish, no matter how much you pay.

A lot of modern batteries seem to have very long lives in cars.
When I were a lad, car batteries often had pretty short lives.

 

[PaulRainbow]

14.7 is quite high for an absorption charge.

Not for AGM batteries.

It also matters how often your batteries are subjected to this charge, and how the charger decides to go to float.

Many yachts seem to have chargers which whack up the volts because a load is drawn, which the charger is powering.
So it's easy for a fully charged battery to see many hours of completely unwanted absorption charging.

Really ? Which chargers are those ?

 

[dje67]

14.7 is quite high for an absorption charge.
It also matters how often your batteries are subjected to this charge, and how the charger decides to go to float.

Many yachts seem to have chargers which whack up the volts because a load is drawn, which the charger is powering.
So it's easy for a fully charged battery to see many hours of completely unwanted absorption charging.

I have a Leoch battery on a small electric start motorbike.
It's 9 years old and has survived abuse and neglect .
I probably bought it because I didn't expect to keep the bike and it was cheaper than Yuasa.

The data sheet available (attached)when I bought the first bank had a useless charge profile that was based on many hours of charging over a rediculous length of time with some very high voltage figures - it used a current controlled charge regime, which many boat charges, including mine, couldn’t provide. When I bought the second bank, a new data sheet was available using a more-conventional voltage/time profile with much lower voltages through the stages. The Victron I fitted at the same time as the second bank always looked, on the BMV-712, to match that ‘shape’ of profile very well.

The most-likely over-charge scenario I probably inflicted on the batteries was after a complete shore-power-based charge cycle followed by a prolonged period of motoring. The ‘dumb’ alternator I have would happily sit at 14.4V, potentially for many hours. Such scenarios are probably no different to what many simple boat systems do, so I’m not sure that I was doing anything different to what thousands of other boat owners do to their batteries…

One daft thought I had about what might have killed by banks (which I can’t believe is any different to most boats on shorepower, is when in a marina with the fridge on it cycles on/off about 5-6 times an hour pulling 6 amps. When it starts the BMV shows that most of that current comes from the batteries. After a couple of minutes the Victron gradually ramps-up its output to provide the full fridge current. Then when the fridge stops, the cycle reverses and batteries charge for a few minutes at a few Amps until the Victron backs-off and net battery current ramps-down to 0A charge. Over many weeks with this behaviour (usually on the 13.2V Storage charge mode) the banks has probably seen thousands of theses mini-cycles. I just wonder if, over time, the bank is gradually being discharged even although the Victron is holding the Voltage at 13.2V. Or, if all those mini-cycles are accumulating to kill the bank?

BTW, the batteries themselves had a sticker on them saying:-
Float application: 13.7V - 13.9V
Cyclic application 14.7V - 14.9V

On shorepower, I met the ‘float’ levels (on both chargers I’ve had) and at sea I’ve not quite met the cyclic range on the second bank, but did on the first.

I’ll no-doubt wonder for ever how I managed to write-off nearly £2k of batteries over the time I had them. Boats, who’d have them…. My overall impression of Lead Carbons so far is that they seem too fragile for use in a marine charging system where there are dozens of different usage scenarios depending on shore power availability/charging, alternator charging, amount of sailing time, background load (fridges, phones, heating, inverters etc), solar input etc. etc. Mine never met the advertising claims!

 

[B27]

The data sheet available (attached)when I bought the first bank had a useless charge profile that was based on many hours of charging over a rediculous length of time with some very high voltage figures - it used a current controlled charge regime, which many boat charges, including mine, couldn’t provide. When I bought the second bank, a new data sheet was available using a more-conventional voltage/time profile with much lower voltages through the stages. The Victron I fitted at the same time as the second bank always looked, on the BMV-712, to match that ‘shape’ of profile very well.

The most-likely over-charge scenario I probably inflicted on the batteries was after a complete shore-power-based charge cycle followed by a prolonged period of motoring. The ‘dumb’ alternator I have would happily sit at 14.4V, potentially for many hours. Such scenarios are probably no different to what many simple boat systems do, so I’m not sure that I was doing anything different to what thousands of other boat owners do to their batteries…

One daft thought I had about what might have killed by banks (which I can’t believe is any different to most boats on shorepower, is when in a marina with the fridge on it cycles on/off about 5-6 times an hour pulling 6 amps. When it starts the BMV shows that most of that current comes from the batteries. After a couple of minutes the Victron gradually ramps-up its output to provide the full fridge current. Then when the fridge stops, the cycle reverses and batteries charge for a few minutes at a few Amps until the Victron backs-off and net battery current ramps-down to 0A charge. Over many weeks with this behaviour (usually on the 13.2V Storage charge mode) the banks has probably seen thousands of theses mini-cycles. I just wonder if, over time, the bank is gradually being discharged even although the Victron is holding the Voltage at 13.2V. Or, if all those mini-cycles are accumulating to kill the bank?

BTW, the batteries themselves had a sticker on them saying:-
Float application: 13.7V - 13.9V
Cyclic application 14.7V - 14.9V

On shorepower, I met the ‘float’ levels (on both chargers I’ve had) and at sea I’ve not quite met the cyclic range on the second bank, but did on the first.

I’ll no-doubt wonder for ever how I managed to write-off nearly £2k of batteries over the time I had them. Boats, who’d have them…. My overall impression of Lead Carbons so far is that they seem too fragile for use in a marine charging system where there are dozens of different usage scenarios depending on shore power availability/charging, alternator charging, amount of sailing time, background load (fridges, phones, heating, inverters etc), solar input etc. etc. Mine never met the advertising claims!

Both those charge profiles have a key point of bulk charging at 0.15 C, to 2.4V per cell.
That's a decision point which 'tells the charger' the battery is something like 85% charged.

If you don't charge at 0.15C, then the battery will be at a different SOC when the voltage hits 2.4Vpc.
So the rest of the charge profile will be wrong.

The data sheet bangs on about cycle life for cycles of 30% discharge or more. Those are the scenarios the engineers were considering when writing the data sheet. If you operate the battery at very shallow cycles, the data sheet is basically void.

Battery makers sell millions of deep cycle batteries to industrial users who cycle them deeply. That is what they are for and that is what they do. You go and use them in a different way, you need to do more than cherry-pick the care instructions.


It seems to me that lithium batteries may actually be easier to 'feed and care for' in this kind of use profile, the alternator is arguably a bit of a sticking point though.

 

[geem]

Both those charge profiles have a key point of bulk charging at 0.15 C, to 2.4V per cell.
That's a decision point which 'tells the charger' the battery is something like 85% charged.

If you don't charge at 0.15C, then the battery will be at a different SOC when the voltage hits 2.4Vpc.
So the rest of the charge profile will be wrong.

The data sheet bangs on about cycle life for cycles of 30% discharge or more. Those are the scenarios the engineers were considering when writing the data sheet. If you operate the battery at very shallow cycles, the data sheet is basically void.

Battery makers sell millions of deep cycle batteries to industrial users who cycle them deeply. That is what they are for and that is what they do. You go and use them in a different way, you need to do more than cherry-pick the care instructions.


It seems to me that lithium batteries may actually be easier to 'feed and care for' in this kind of use profile, the alternator is arguably a bit of a sticking point though.

The beauty of lithium is it is much happier being at a partial state of charge then lead. You can go months without ever reaching 100% SOC and they will be fine. Do this with lead and they will have a short life. Lithium is best kept at 50% charge for long life. Lithium is only stressed in the 0- 20% SOC and 80-100% SOC. Everything else in between is the sweet spot

 

[rotrax]

3 years ago I fitted 5 Leoch LDC 115 lead carbon batteries to my yacht. After a year and a half that bank completely failed on me - after a few nights at anchor using no more than about 150Ah, any significant load on the bank resulted in voltage collapsing towards 11V. The batteries spent nearly all their life on shore power using a multistage charger configured very close to the (at that time) data sheet and never had more than 200Ah pulled from them and I reckon they had no more than 100 cycles of around 100Ah. Leoch suspected over-charging - alternator was at 14.7V, Sterling charger was 14.7V Abs, 13.5V float.

A new bank was fitted a year ago and has failed in exactly the same way. They have had no more than a couple of cycles of 200Ah plus around 80-100 cycles of <100Ah, and are kept permanently on shorepower fed from a new EasySolar 12/1600/70 Which, once it has completed its 14.4V AGM charge cycle (bulk/absorption/float) holds its output at 13.2V, with a refresh absorption top-up every week (the standard Victron AGM profile). Alternator was changed to a 14.4V, 100A unit. So, I've no charge source giving more than 14.4V, so the 2nd bank failing was unlikely to be over-charging.

I did a bit of playing around with the bank. Separated the bank into the 5 individual batteries and ran each one on a 60A load via the inverter (fairly brutal...). Data sheet for the battery says there should around an hour and a half reserve time at that load on a single battery. One battery managed 22Ah before crashing, the other four were around 10Ah...! So, all knackered equally badly. Once the load was off each battery, within around 15 mins they had all recovered to nearly 12.8 - 12.9V across their terminals.

When I'm motoring, the Starter battery is always also in-circuit to the alternator and seeing up to 14.4V, so I did a capacity test on that to see how it has faired on the same use-profile. That single Leoch XR1750 AGM has outlasted both the LDC banks and some (nearly 4 years old, but obviously never really deep-cycled). On a 60-65A load it was still holding up at 11.0V after an hour. The voltage profile compared to the datasheet for that battery matched perfectly against how it should perform when new - in fact the time to reach 11V exceeded that quoted for a 50A load profile. So, it looks like that battery is in perfect condition, especially given its age. When on shorepower, longer term, the starter battery is completely disconnected from the house bank and Victron - it really only ever sees charge from the alternator. So, I'm going to discount my alternator as being the issue on my boat as the starter battery has seen as many hours as the house bank when motoring.

So, I've no idea whether I've undercharged or overcharged my 1st and 2nd banks, but I put this info out there in case others, including the OP have been equally stung by AGMs (lead carbons in my case) being trashed by my style of boat usage and means of charging them.

The next bank is LiFePO4 hybrid - not touching AGMs again...! The price difference is now relatively small between the technologies.

We have 6 AGM's, 5 Lifelines, I Chinese, but with spiral wound technology. 4 Lifelines were fitted together and are now 9 seasons old.
1 Lifeline, the engine start battery, is 5 seasons old. The Chinese battery is the Genset start battery.
They are NEVER left on the Charles 60 amp battery charger unless we are aboard. For the last 3 seasons, since I installed 400w of Solar, their only charge has been Solar or main engine alternator. This is a Balmar 110amp with a matching Balmar smart charger.
Even on dull/rainy days using two fridges and our dometic 40 litre as a freezer the Solar balances.
Some Island Packet owners have had 15 plus years from Lifelines.

 

[GEM43]

We have 6 AGM's, 5 Lifelines, I Chinese, but with spiral wound technology. 4 Lifelines were fitted together and are now 9 seasons old.
1 Lifeline, the engine start battery, is 5 seasons old. The Chinese battery is the Genset start battery.
They are NEVER left on the Charles 60 amp battery charger unless we are aboard. For the last 3 seasons, since I installed 400w of Solar, their only charge has been Solar or main engine alternator. This is a Balmar 110amp with a matching Balmar smart charger.
Even on dull/rainy days using two fridges and our dometic 40 litre as a freezer the Solar balances.
Some Island Packet owners have had 15 plus years from Lifelines.

Our Lifeline batteries were still excellent after 16 seasons. Expensive but excellent.

 

[geem]

We have 6 AGM's, 5 Lifelines, I Chinese, but with spiral wound technology. 4 Lifelines were fitted together and are now 9 seasons old.
1 Lifeline, the engine start battery, is 5 seasons old. The Chinese battery is the Genset start battery.
They are NEVER left on the Charles 60 amp battery charger unless we are aboard. For the last 3 seasons, since I installed 400w of Solar, their only charge has been Solar or main engine alternator. This is a Balmar 110amp with a matching Balmar smart charger.
Even on dull/rainy days using two fridges and our dometic 40 litre as a freezer the Solar balances.
Some Island Packet owners have had 15 plus years from Lifelines.

Yet I know of cruisers in the Caribbean who struggle to get 4 years out of Lifelines as liveaboards. Tropical heat kills leads batteries

 

[dje67]

My boat lives in Scotland, so high temperature is definitely not really an issue here...!

So, if two similarly sized battery installations have been killed by lack of charging, even although they are on shore-power pretty-much fully time with a Multiplus charger (50A in my case, just under 0.1C), then what do people think has been the root cause?

My own setup used the standard Victron AGM profile as I didn't have the Mk3 USB dongle thingy to do anything fancier than just select DIP switches to suit. I've now got one (too late!) - if I (or some other unsuspecting boat owner) was re-installing the same batteries again, what parameter(s) are the key ones in the Multiplus to ensure that the default AGM profile doesn't do more harm than good. The Multiplus seems to do do lots of clever calculations to determine the charge times etc. to be best for AGM, but I get the feeling that for some combinations of battery chemistry, bank size, cycle depth and background loading, the Multiplus is getting it significantly wrong.

Also, the claims associated with Lead Carbons (in my case) being good for low states of charge don't seem to match up with reality, if indeed under-charging is the issue.

 

[PaulRainbow]

My boat lives in Scotland, so high temperature is definitely not really an issue here...!

So, if two similarly sized battery installations have been killed by lack of charging, even although they are on shore-power pretty-much fully time with a Multiplus charger (50A in my case, just under 0.1C), then what do people think has been the root cause?

My own setup used the standard Victron AGM profile as I didn't have the Mk3 USB dongle thingy to do anything fancier than just select DIP switches to suit. I've now got one (too late!) - if I (or some other unsuspecting boat owner) was re-installing the same batteries again, what parameter(s) are the key ones in the Multiplus to ensure that the default AGM profile doesn't do more harm than good. The Multiplus seems to do do lots of clever calculations to determine the charge times etc. to be best for AGM, but I get the feeling that for some combinations of battery chemistry, bank size, cycle depth and background loading, the Multiplus is getting it significantly wrong.

Also, the claims associated with Lead Carbons (in my case) being good for low states of charge don't seem to match up with reality, if indeed under-charging is the issue.

I think the default Multiplus profile is 14.4 Abs and 13.8 float. 14.4 is too low, they want 14.7 unless manufacturers spec sheets say different.

 

[geem]

........