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Discussion Starter · #1 ·
I just rewired my boat (for the second time). I'm using a 1/2/BOTH switch in the configuration recommended by Maine Sail here:
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com

My normal bank is a pair of group 24 AGM batteries. They are charged by a Xantrex Truecharge 20+, a small solar panel with a Genasun MPPT controller, and a 55 amp alternator that has a Mark Grasser multi-stage regulator (it is like a Sterling Pro-Reg-D, both are made by the same people). Everything is set to AGM charging profiles.

My emergency bank is a small higher-CCA U1 sized AGM battery. Since it is not used for any loads in it's normal life I want to give it the best easy charging life possible to make sure that I don't abuse it. This battery is small because my boat doesn't really have good space for 3 group 24 batteries. To make sure that it is healthy I plan on starting the boat with it once a month or so.

Currently I use a Xantrex Echo Charger to charge the U1. It is not hooked up to any other charger. Since the Echo Charger is a following charger with a 0.4v voltage drop I am worried that it will potentially overcharge the battery and shorten it's life. Lifeline wants this battery to be floated at 13.1 to 13.4 V. When my shore power charger is in absorption mode it will provide 14V, which will cause 13.6V at the U1.

I considered hooking up the U1 battery to my shore power charger using the second battery output. However it looks like the Truecharge 20+ (despite having multiple battery outputs) is really a single bank charger and can't float the emergency bank while providing absorption charge to the primary bank.

Any suggestions on the best strategy? Will the Echo Charge hurt my new little battery? Should I consider getting a low current but smart second shore power charger for the U1?
 

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Alex-
"Lifeline wants this battery to be floated at 13.1 to 13.4 V. ...my shore power charger...will cause 13.6V at the U1."

OK, so the crux of this is that your shore charger would provide 13.6 and you want less than 13.4, possibly more like 13.2-13.3?

That should actually be a simple fix. Putting a common power diode in the charging line from the shore charger to the U1 battery, would cause a voltage drop of about 0.3V all the time. Neatly knocking down the excess voltage you have.

The exact drop will depend on the diode type and power, and if that same charging source is used all the time, then the diode could be manually switched in when you leave the dock tied up, so it didn't interfere with bulk charging.

Anyone see why this wouldn't be the simplest cheapest solution?
 

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Discussion Starter · #5 ·
Echo Charger is not like the ACR, so that article doesn't apply to my setup. The banks are never combined with the Echo Charger. The shore charger doesn't really combine either, it uses a diode on each bank to isolate them. This means that if my emergency battery is full and the house batteries are going at absorption voltage that the emergency battery will also see that voltage.

I could switch to a ACR (I couldn't use one before because I was mixing battery chemistries, but I'm not longer doing that), but a new ACR costs about as much as a second low amperage shore power charger.

Hello Sailor: A power diode to drop 0.3V would put me on float or lower all of the time, which might be an okay solution. Thanks for the idea. 0.3V is a very small drop for most power diodes though, I'll have to see if Digikey or Mouser have something that will work.

I don't use shore power much in the summer (since we have good solar), but I use it in the winter to keep a dehumidifer going. In the summer it is only hooked up if I need to use an AC powered tool on the boat.
 

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Woah you people are cruel you are going to make me think out all the details of a multi-source charging system before I even have a boat. Alex your system sounds fine but I will be brainstorming, sorry my mind works slowly, it may take several weeks or more.
 

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Echo Charger is not like the ACR, so that article doesn't apply to my setup. The banks are never combined with the Echo Charger. The shore charger doesn't really combine either, it uses a diode on each bank to isolate them. This means that if my emergency battery is full and the house batteries are going at absorption voltage that the emergency battery will also see that voltage.

I could switch to a ACR (I couldn't use one before because I was mixing battery chemistries, but I'm not longer doing that), but a new ACR costs about as much as a second low amperage shore power charger.

Hello Sailor: A power diode to drop 0.3V would put me on float or lower all of the time, which might be an okay solution. Thanks for the idea. 0.3V is a very small drop for most power diodes though, I'll have to see if Digikey or Mouser have something that will work.

I don't use shore power much in the summer (since we have good solar), but I use it in the winter to keep a dehumidifer going. In the summer it is only hooked up if I need to use an AC powered tool on the boat.
I am not fully understanding your set up but the point of the article is that although the voltage is full there is no amperage so no problem could result.
 

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I just rewired my boat (for the second time). I'm using a 1/2/BOTH switch in the configuration recommended by Maine Sail here:
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com

My normal bank is a pair of group 24 AGM batteries. They are charged by a Xantrex Truecharge 20+, a small solar panel with a Genasun MPPT controller, and a 55 amp alternator that has a Mark Grasser multi-stage regulator (it is like a Sterling Pro-Reg-D, both are made by the same people). Everything is set to AGM charging profiles.

My emergency bank is a small higher-CCA U1 sized AGM battery. Since it is not used for any loads in it's normal life I want to give it the best easy charging life possible to make sure that I don't abuse it. This battery is small because my boat doesn't really have good space for 3 group 24 batteries. To make sure that it is healthy I plan on starting the boat with it once a month or so.

Currently I use a Xantrex Echo Charger to charge the U1. It is not hooked up to any other charger. Since the Echo Charger is a following charger with a 0.4v voltage drop I am worried that it will potentially overcharge the battery and shorten it's life. Lifeline wants this battery to be floated at 13.1 to 13.4 V. When my shore power charger is in absorption mode it will provide 14V, which will cause 13.6V at the U1.

I considered hooking up the U1 battery to my shore power charger using the second battery output. However it looks like the Truecharge 20+ (despite having multiple battery outputs) is really a single bank charger and can't float the emergency bank while providing absorption charge to the primary bank.

Any suggestions on the best strategy? Will the Echo Charge hurt my new little battery? Should I consider getting a low current but smart second shore power charger for the U1?
Alex,

You are really asking for a refund of your Popcorn due to a few unpopped kernels in the bottom.;)

If the battery is not used much why even use the Echo? They can sit for at least two months and longer if the bilge temps are cooler. Put an ON/OFF in the neg lead to the Echo and simply disable it.....

While in storage, batteries should be boost charged every 90 days or when the open circuit voltage (OCV) drops to 12.5 volts for a 12 volt battery (6.25 volts for a 6 volt battery). This OCV corresponds to approximately 75% state of charge. Boost charge batteries using a constant voltage charger set at 14.4 to 15.0 volts for a 12 volt battery (7.2 to 7.5 volts for a 6 volt battery).The boost charge should be applied until the charging current falls below 0.5 percent of the battery's 20 hour rated capacity (0.5 amps for a 100 Ah battery).

FACT: I have piles of AGM banks out there where the start battery is charged via an Echo or Duo Charger off solar, wind, alt and shore charger.. I have NEVER seen a start battery fail before the house bank. Not once, and none of these Echo's are switched off, ever.. The main banks however are temp compensated.

You may be ignoring:

Temp compensation: This is important for the cycle life of Lifeline batteries. Your alt reg has it but does your Xantrex? Your Genasun is "local ambient" compensation so unless in the same space as the batteries this can potentially pose issues.

At 50F battery temp absorption voltage should be 14.72V and float should be 13.7V. Yet at 90F absorption should be just 14.15V and float 13.13V....

Minimum Charge Rate:

Lifeline wants to see a minimum charge rate of 20% of "C" which means at least 32A of steady current.. You alt may be able to hit this number when hot, but your shore charger can not. I would recommned using the alt as often as possible.

For repetitive deep cycling, chargers should have an output
current of at least 0.2C (20 Amps for a 100 Ah battery). If the output current is less than this value, the cycle life of the battery may be negatively affected.


Again your worries are not an issue. Heck nearly every battery charger ever made has ONE CHARGE PROFILE and all banks get the SAME CHARGE PROFILE and start batteries almost always, like 99.8% of the time, outlast house banks.......... If you are still concerned then put an On/Off in the Echo neg lead and charge the U1 bi-monthly.......

Also lets not forget that cars, trucks and busses which use the same lead acid battery chemistry charge at a steady 14.2V+ continuously...
 

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Alex-
Since that battery is "just" a backup, I don't think a lower bulk charge will be any issue. It would be getting the float charge almost or all the time anyway, yes? And of course, a manual switch (to bypass the diode) would solve that anyway.
Hazy memory that a Schottky or epitaxial diode is one of several types that have a low voltage drop. But the tech support guys at Digikey can tell you for sure, and tell you what's in stock with a sufficient current rating.

The ideal solution is probably a small dedicated solar panel, small PWM charge controller, to keep the budget down for a light duty isolated charge system. Still, that's probably $120 more than a diode would be. Which may be breakfast money or rent...depending.(G)
 

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Discussion Starter · #10 ·
I do have temp sensors for the Xantrex shore power charger and the Mark Grasser alternator regulator. The Genasun MPPT is one compartment over from the house batteries, but close (about 6") with only plywood separating them.

The secondary/emergency battery is not a starting battery, it is wired as shown in your post that I linked to. It is only a reserve battery and the engine is started from the house bank.

I'm glad to hear that the Echo Charger won't cook my secondary battery.

I don't use shore power for 6 months of the year, so my house batteries are primarily charged through the alternator and floated by the solar. My house batteries aren't Lifeline, they are Chinese-made Cabela-branded AGM batteries that are almost certainly lower quality (I believe they are really Universal Battery UB12750). I try to take good care of them and I'm curious to see what kind of lifespan I get. When they die I'll probably go back to wet cells for the house batteries. I bought AGMs because I was considering storing batteries on their side, but I found locations where I could leave them upright.

Power loads on my boat are very light, a typical cruising day uses 10-12AH that is recovered by the solar panel. Everything is LED, electronics are modern and lower power draw, and the laptops and tablets that get occasional use onboard are also power efficient models.
 

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I do have temp sensors for the Xantrex shore power charger and the Mark Grasser alternator regulator. The Genasun MPPT is one compartment over from the house batteries, but close (about 6") with only plywood separating them.

The secondary/emergency battery is not a starting battery, it is wired as shown in your post that I linked to. It is only a reserve battery and the engine is started from the house bank.

I'm glad to hear that the Echo Charger won't cook my secondary battery.

I don't use shore power for 6 months of the year, so my house batteries are primarily charged through the alternator and floated by the solar. My house batteries aren't Lifeline, they are Chinese-made Cabela-branded AGM batteries that are almost certainly lower quality (I believe they are really Universal Battery UB12750). I try to take good care of them and I'm curious to see what kind of lifespan I get. When they die I'll probably go back to wet cells for the house batteries. I bought AGMs because I was considering storing batteries on their side, but I found locations where I could leave them upright.

Power loads on my boat are very light, a typical cruising day uses 10-12AH that is recovered by the solar panel. Everything is LED, electronics are modern and lower power draw, and the laptops and tablets that get occasional use onboard are also power efficient models.
Reserve or otherwise charge it, let sit for a few months, charge it again.... I do this on my own boat because I have an LFP bank as house (max charge 13.8V) and an AGM bank as "reserve".. I top it up about once ever two months to 14.6V.... I did however "break in" my AGM before putting it into service with about 10 cycles to 80% DOD..

No real need for the Echo to be on all the time, but I have never once seen it shorten a reserve or starting banks life... The Cabella's batteries seem to be UPS type batteries from China. The best value in an AGM currently is the Sears Die Hard Platinum 31M which is really an Odyssey PCM2150 TPPL for about $100.00 - $150.00 less.... These are a steal of an AGM, especially when Sears runs a sale..
 

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Finally a reason for me to actually post, given that I am more competent on EE stuff then on sailing (and out of a boat :()

Alex-
Since that battery is "just" a backup, I don't think a lower bulk charge will be any issue. It would be getting the float charge almost or all the time anyway, yes? And of course, a manual switch (to bypass the diode) would solve that anyway.
Hazy memory that a Schottky or epitaxial diode is one of several types that have a low voltage drop. But the tech support guys at Digikey can tell you for sure, and tell you what's in stock with a sufficient current rating.
Schottky diodes have the lowest forward voltage drop, of around 0.3V, do get one with a appropriate current rating and optionally stick a little heatsink on, so it doesn't fail. Given that when they fail, they have about an equal chance of failing open or failing shortcircuit (which means your entire bank isolation is gone).

If your emergency battery is for starting or running a few efficient (LED) nav lights, then the slightly lower voltage shouldn't matter on the bulk of a lead acid battery.

Only "annoyance" can be if you don't put a diode between the charge and housebank aswell, then if the housebank has a higher charge (voltage) remaining and you do use your emergency bank, you will get balancing effects, which may exceed the charge rate of the cells, but in real life, if they are emergency they should never be used in this case (you could add a disconnect for this situation, so the housebank is entirely isolated from both charger and load when using the emergency battery), also lead acid batteries are robust as hell, so outside of some life reduction, it shouldn't be a significant issue.

The ideal solution is probably a small dedicated solar panel, small PWM charge controller, to keep the budget down for a light duty isolated charge system. Still, that's probably $120 more than a diode would be. Which may be breakfast money or rent...depending.(G)
Probably overkill, unless you go ocean sailing or the like, in which case doing this means you'd have an entirely spare electric system, which could at least keep your navlights on when you have problems.

This is actually why I've been tempted to build some navlights with builtin li-ion battery and perhaps even solar cells, so even if I have battery or even wiring failure, the lights stay on (and this is perfectly legal here, as long as they meet the regs, they meet the regs, no need to pay for testing).
 

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Ikarus-
I'd only use the diode as a dropping diode, not an isolation diode between banks, so a diode failure wouldn't have the same consequences. "Obviously" heat sinking and mounting would be considerations for any device.

Alex-

What folks tend to forget about LifeLine batteries is that they are NOT normal batteries. They are specifically made for the military aviation market, and aviation batteries routinely may need to go up to 40,000 feet where the ambient air pressure is damned thin. A conventional battery would probably bulge, blow out through the overpressure vents, and rapidly ruin itself with repeated use.

Which explains why Lifeline batteries are built with much stronger cases than "sea level" batteries or automobile batteries, which in turn allows them to take the pressure of an equalizing charge while at sea level.

Regardless of what kind of goo and plates are in them--they're a different battery, compared to any other non-aviation one.

I suspect that Cabela keeps an eye on their suppliers, so whatever you've got should be a standard "commodity" grade. Typically those are useless after 4 years in UPSes and alarm systems but I've seen pampered ones last longer.
 

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Discussion Starter · #14 ·
If I get 4 years out of the battery I'll be happy with that (I'm a little over a year into using them). I bought them when Cabelas was clearing them out, and paid about $100 each. It was an experiment with AGM to see if the ability to mount them sideways opened up any additional storage locations in my smaller boat. In the end I kept them upright and will be going back to wet cells when these batteries die. This is the spec sheet for the battery that I'm using:
http://www.1000bulbs.com/pdf/ub45821-spec.pdf

The system is working pretty well so far. One downside to joining my house and starting batteries back together (previously they were on their own circuits) is that the voltage drop when starting the engine usually causes my plotter to reboot.

My emergency battery is the Lifeline U1. The small size enabled me to fit it in a very tight spot on the boat. I was originally going to get a Odyssey 925, but found the Lifeline U1 locally for about the same price. Both have roughly 325 CCA and are probably borderline for this use.
 

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You may be able to fix that plotter problem by just putting a supercapacitor on the plotter's power lines, right behind the plotter. They're fairly inexpensive and available from car audio shops as well as online. Basically install it and forget it, and it provides a couple of seconds of power to run the plotter, even when something else pulls down the batteries for a moment.

But there's also something to be said for shutting down all the electronics when starting or stopping the engine. Starting and stopping both throw spikes, sometimes spikes over 1000 volts, from the starter and alternator. And those spikes fry electronics. If you add spike protection devices, the same spikes eventually fry them instead, so shutting down (or isolating) the electronics during start/stops is still the KISS solution.
 
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