Warning, rant...
For the second time is a week I have had to explain to a customer that their $1000.00 + bank of AGM batteries is dead in under four years. I have asked Lifeline to publish their tome on how to properly care for them on their web site so people will at least have a skating chance if their boats are cruised or left on a mooring.. Hopefully they will...
The boat today has a very knowledgeable owner, decent charging system, battery voltage meter and at the beginning of the season his batteries tested well (for cranking ability) with a Midtronics EXP-1000. When I see AGM batteries fail sometimes they fail, suddenly and without warning.Why? I don't have a good answer for that. AGM batteries are great batteries but if abused, as they often are, they are no better than any other lead acid battery, just more expensive.
Dual Circuit Plus Battery Switch Rant:
This is also a rant or vent about the Blue Seas Dual Circuit Plus battery switch. This owner installed one, and when his house bank failed internally last week, he had no way to switch to only his starting bank, in an isolated manner. They key here is; "in an isolated manner".
to get any sort of VHF, instruments etc. without combining a good battery with a completely failed, internally shorted battery/bank.
The start battery still likely had a little life in it, about 110 cranking amps (Midtronics) before I tried to start the motor, vs. the 1000+ it should have, but due to the Blue Seas DCP switch he was unable to take any advantage of his second bank, in an isolated manner, as a safety back up because the failure in the house bank bled it down to the point where he could not start his motor at all after using the "COMBINE" position of the DCP switch.
The owner did not realize the house bank had failed internally so when he got to his destination, and could not make a VHF call or turn on any of his electronics, he did what he thought he should do, he turned the battery switch to COMBINE.....
When he did combine the start battery with the house bank it was apparently into an internally shorted house bank. He left it in combine/parallel long enough, while using the VHF radio & trying to figure stuff out, that it sucked the remaining useful life out of his starting battery and he was left dead in the water and needed a tow to get home.
This is what Lifeline suggests for expected life, based on care.
How many of us fall into scenario #4?
Bottom Line:
Dual Circuit Plus Switch Options:
If you want to use a DCP switch the wiring diagram below makes it much more flexible and provides both isolation and redundancy.
With the Blue Sea 5511e Dual Circuit switch your only choice in an emergency is to combine a perfectly good bank with a potentially bad one. Not really the best practice. The switch offers no way to fully isolate a bad bank.
You would also need to wire the SI feature of a Blue Sea ACR to get the benefit of "isolated" banks for starting, this is something most boaters with a DCP switch almost never do. Without the SI (start isolation) feature you may not be "isolating" start from house loads like you think you are.
When I "modify" DCP switch wiring on customers boats, who finally relaize they do want the ability to isolate a bad bank, while using the good one to power everything, I add two mSeries ON/OFF switches which are are out of plain sight, usually in the battery compartment.
All the guests and owner see is the single DCP ON/OFF switch. The DCP label already has a yellow WARNING placard with an ! for "combine batteries". This should be enough to prevent guests from messing with it. The general wiring would usually look like the diagram below.. The hidden emergency ON/OFF switches are usually within about 7-10" of each bank after the fuse and their normal position is ON. This switching gives you the best of all worlds plus 100% bank isolation in the event of a failure. In the form of redundancy now either bank can be used for powering the entire vessel without having to be combined with a potentially bad battery.
If your alternator is direct wired to the house bank, for optimal charging performance, you'd already want an alternator service disconnect switch for service techs anyway.
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For the second time is a week I have had to explain to a customer that their $1000.00 + bank of AGM batteries is dead in under four years. I have asked Lifeline to publish their tome on how to properly care for them on their web site so people will at least have a skating chance if their boats are cruised or left on a mooring.. Hopefully they will...
The boat today has a very knowledgeable owner, decent charging system, battery voltage meter and at the beginning of the season his batteries tested well (for cranking ability) with a Midtronics EXP-1000. When I see AGM batteries fail sometimes they fail, suddenly and without warning.Why? I don't have a good answer for that. AGM batteries are great batteries but if abused, as they often are, they are no better than any other lead acid battery, just more expensive.
Dual Circuit Plus Battery Switch Rant:
This is also a rant or vent about the Blue Seas Dual Circuit Plus battery switch. This owner installed one, and when his house bank failed internally last week, he had no way to switch to only his starting bank, in an isolated manner. They key here is; "in an isolated manner".
to get any sort of VHF, instruments etc. without combining a good battery with a completely failed, internally shorted battery/bank.
The start battery still likely had a little life in it, about 110 cranking amps (Midtronics) before I tried to start the motor, vs. the 1000+ it should have, but due to the Blue Seas DCP switch he was unable to take any advantage of his second bank, in an isolated manner, as a safety back up because the failure in the house bank bled it down to the point where he could not start his motor at all after using the "COMBINE" position of the DCP switch.
The owner did not realize the house bank had failed internally so when he got to his destination, and could not make a VHF call or turn on any of his electronics, he did what he thought he should do, he turned the battery switch to COMBINE.....
When he did combine the start battery with the house bank it was apparently into an internally shorted house bank. He left it in combine/parallel long enough, while using the VHF radio & trying to figure stuff out, that it sucked the remaining useful life out of his starting battery and he was left dead in the water and needed a tow to get home.
- If buying AGM's, please charge & care for them correctly..
- If buying a Blue Seas Dual Circuit Plus Switch please do your home work and make sure it is the right fit for you.
This is what Lifeline suggests for expected life, based on care.
- #1 Fully charge after each discharge. Estimated life: 6-9 Years
- #2 Fully Recharge at least once a week and equalize once a month. Estimated life: 4-6 Years..
- #3 Only recharge to 85% and equalize once a month. Estimated life: 2-4 years.
- #4 Only charge to 85% and never equalize. Estimated life: 1 year.
How many of us fall into scenario #4?
Bottom Line:
- He never equalized his Lifeline batteries
- Mooring sailed the boat with no solar
- Only used an alternator for charging (except in the off season)
- Used the COMBINE feature of the DCP switch, with a bank failure, and it left him dead in the water
Dual Circuit Plus Switch Options:
If you want to use a DCP switch the wiring diagram below makes it much more flexible and provides both isolation and redundancy.
With the Blue Sea 5511e Dual Circuit switch your only choice in an emergency is to combine a perfectly good bank with a potentially bad one. Not really the best practice. The switch offers no way to fully isolate a bad bank.
You would also need to wire the SI feature of a Blue Sea ACR to get the benefit of "isolated" banks for starting, this is something most boaters with a DCP switch almost never do. Without the SI (start isolation) feature you may not be "isolating" start from house loads like you think you are.
When I "modify" DCP switch wiring on customers boats, who finally relaize they do want the ability to isolate a bad bank, while using the good one to power everything, I add two mSeries ON/OFF switches which are are out of plain sight, usually in the battery compartment.
All the guests and owner see is the single DCP ON/OFF switch. The DCP label already has a yellow WARNING placard with an ! for "combine batteries". This should be enough to prevent guests from messing with it. The general wiring would usually look like the diagram below.. The hidden emergency ON/OFF switches are usually within about 7-10" of each bank after the fuse and their normal position is ON. This switching gives you the best of all worlds plus 100% bank isolation in the event of a failure. In the form of redundancy now either bank can be used for powering the entire vessel without having to be combined with a potentially bad battery.
If your alternator is direct wired to the house bank, for optimal charging performance, you'd already want an alternator service disconnect switch for service techs anyway.
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