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  #1  
Old 02-02-2007
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Battery Monitoring/Chargers

Scenario:

I'm looking at a DC-wired boat that has a two bank system - four AGM batteries on the house bank, and one AGM crank on the starter bank. The electrical panel features a volt meter and an amp meter. The battery charger consists of a single 110 volt automatic, 40 amp with temperature sensor. Not sure of the brand.

Questions: (If anyone has the time and inclination)

1. Wouldn't it be much better to have dedicated amp and volt meters for EACH of the four batteries, for a total of eight meters? Or can one have too many wires connected to each battery? (I would prefer to see the condition of each battery at a glance.)

2. Wouldn't it be better to have 1 dedicated smart charger for each battery? Or is there a smart charger available that can deliver the right flow to 4 batteries that are not identical?

3. If I introduce a wind generator, would I have to buy a seperate smart charger just for that? Then another if I add solar? In other words, what about inputs to the charger/chargers? Is there a charger available that can accept simultaneous connections from all my preferred DC charging options - diesel alternator, Honda generator, wind, and solar?

4. What about AC shore power? Would I require anything other than a combination inverter/charger? How do I monitor that? Would I need to install an AC electrical panel? (I run my power tools and other AC appliances off a portable generator.)

5. Does it make any sense to purchase a single 200pd AGM battery? Do the benefits of fewer wires/less complexity outweigh the difficulty of getting the damn thing on and off the boat? (Apparently not, since I've never seen this on a 42 ft boat. Isn't it true that every AGM battery consists of smaller batteries, or 'cells' anyway?)

Perhaps someone can direct me to a URL offering boat electrical schematics so that I may better understand the options. I haven't been able to find much doing keyword searches. (Calder's book is on its way.)
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Old 02-02-2007
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I'm certainly no expert, and all I can really offer is what I've done, and why. Perhaps that will help, perhaps not.

I have 3 AGM's as house, one as start. I use a 110 volt 20 Amp smart charger set for AGM's. I don't have the temp sensor, but will probably add one eventually. Battery banks are connected to a 4 position switch (off, 1, both, 2). 110 volt charger is connected to the common (both) lead at a fuse block, as is the alternator. My wind generator is wired directly to the house bank, and it is internally regulated. Solar panels would requre a charge controller. I use a Link 20 battery monitor.

My thinking is that individual meters for each battery is a bit of overkill. As to AC power, you should have at least a main, though the charger should have it's own breaker as well. If you aren't running any AC equipment from your batteries, you don't need an inverter. I took out a large inverter/charger and replaced it with just a charger. For AC power away from the dock, I use a small inverter for my laptop.

Personally, I like the idea of having multiple batteries for my house bank. In the event that one goes bad, it can be taken out of the loop and I still have 2/3 of my capacity. Whereas with single large battery, if it dies, then I have nothing.

There is a good article in the Spring '06 issue of Boat Works, complete with a schematic on setting up a DC electrical system.
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Old 02-02-2007
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Calders book tells it all.

I changed a single 220 Ah house battery for four 110 Ah batteries, in the same box. Firstly because I wanted more Ah and I could fit taller batteries, secondly so I could get the beasts out one at a time from their akward corner and thirdly for PBzeer's reason- when a battery dies, it's usually one cell but it pulls the rest down with it taking all the charge. So taking 1 of 4 out leaves me with 330 Ah nominally.

I have my one small solar panel directly coupled to the house batteries, a regulator is not needed, as the panel cannot overcharge 440Ah. My shore power battery charger (Vectron) only trickle charges the cranking battery and does its speed charging on the house battery. I don't have a temperature sensor on it.

If you want to add more voltmeters, get calibrated digital ones, the usual cheap analogue meters are nowhere near accurate enough. So it may be easier to run round with a good calibrated multimeter occasionally and stick with one analogue meter per bank.

I think you would have isolation problems wiring multiple chargers, but certainly that would be ideal. With aging, even identical batteries drift apart in their needs with the weakest one dragging the others down.

Just to throw open the usual debate; I use ordinary cheap lead acid batteries, check the specific gravity regularly and use a discharge tester to check performance. If you want to spend money on expensive semi-traction, gel, AGM, etc. go ahead. To me, over capacity is the only answer for longevity with lead. (If only the NiMH, or better Li-Ion, battery prices would drop...)

P.S. follow the links at the bottom of this page for more advice....

Last edited by Idiens; 02-02-2007 at 03:21 AM.
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Old 02-02-2007
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Quote:
Originally Posted by capecodphyllis
Scenario:

I'm looking at a DC-wired boat that has a two bank system - four AGM batteries on the house bank, and one AGM crank on the starter bank. The electrical panel features a volt meter and an amp meter. The battery charger consists of a single 110 volt automatic, 40 amp with temperature sensor. Not sure of the brand.
Does the charger have two outputs, or just one? My guess would be that it already has two outputs, as most chargers above 30Amps generally do.

Quote:
1. Wouldn't it be much better to have dedicated amp and volt meters for EACH of the four batteries, for a total of eight meters? Or can one have too many wires connected to each battery? (I would prefer to see the condition of each battery at a glance.)
Doing that is both overkill and gives you a lot more points of failure. A single monitor will tell you how each bank is doing... if the monitor indicates that you may have a problem, then you can always pull out the handheld volt-ohm-meter, and check each individually...

Quote:
Wouldn't it be better to have 1 dedicated smart charger for each battery? Or is there a smart charger available that can deliver the right flow to 4 batteries that are not identical?
Again way overkill, and introduces multiple points of failure as well as serious problems in isolating the batteries, so that the multiple chargers don't interfere with each other. Also, this is a very expensive proposition.

Generally, a smart battery charger will sense voltage levels and taper off the charge rate based on the voltage level sensed. If you have multiple chargers, they would sense the voltage of each other, since they're all hooked in parallel on the house bank, and the bank wouldn't charge properly...as each charger came on—it'd sense the voltage of the other chargers and promptly drop the charging output it would give. You can't really isolate the batteries from one another and still have the act as a single battery bank realistically.

This is also one reason it is recommended that the batteries in a single bank be of all the same brand and age if at all possible. As batteries age, their charging characteristics change slightly, as does their ability to hold a charge and maximum voltage.

Quote:
If I introduce a wind generator, would I have to buy a seperate smart charger just for that? Then another if I add solar? In other words, what about inputs to the charger/chargers? Is there a charger available that can accept simultaneous connections from all my preferred DC charging options - diesel alternator, Honda generator, wind, and solar?
This gets a bit more complicated. Solar panels have some specific issues, as do wind generators. Wind generators generally require the charge controller to have a line that will trigger the braking feature of the generator when the output rises too high. Solar panels don't shut off, and some of the solar panel chargers essentially short the inputs to stop the incoming charge. Two generators is kind of overkill... and why do you need so much electrical generation capacity on your boat??? You really should size your generation capability to your usage plus some percentage for future expansion...

Quote:
What about AC shore power? Would I require anything other than a combination inverter/charger? How do I monitor that? Would I need to install an AC electrical panel? (I run my power tools and other AC appliances off a portable generator.)
Most inverter/chargers have battery monitoring capabilities, either built-in or as an accessory. If you're going to have shore power, you really do need to have an AC-dedicated panel. BTW, if you're putting in such a system, you could run your power tools off the AC-side of the boat fairly easily, especially given the size of the battery bank. It really wouldn't be an issue if you had a diesel genset... and I don't really see a point in having the portable generator.

Quote:
5. Does it make any sense to purchase a single 200pd AGM battery? Do the benefits of fewer wires/less complexity outweigh the difficulty of getting the damn thing on and off the boat? (Apparently not, since I've never seen this on a 42 ft boat. Isn't it true that every AGM battery consists of smaller batteries, or 'cells' anyway?)
The advantages of smaller batteries, hooked in parallel to present as a single larger bank are: 1) The individual batteries are lighter and easier to handle; 2) if any one battery fails, you lose a smaller percentage of your actual battery capacity; 3) you can often use the same batteries for the house and start side, and if the start batttery fails, you can swap one out temporarily to keep the redundancy in the system; 4) battery placement is a bit more flexible with the smaller batteries.

Quote:
Perhaps someone can direct me to a URL offering boat electrical schematics so that I may better understand the options. I haven't been able to find much doing keyword searches. (Calder's book is on its way.)
If you call up any of the big marine electrical panel suppliers or charger suppliers and ask for their catalog, most catalogs have some pretty decent basic battery/charger diagrams in them. They will be company part specific, but it is relatively easy to generalize them.
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Old 02-02-2007
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Phyllis: Here's a few links that may prove helpful as you think your system through:
Everything you want to know about batteries and how they work/charge etc.
http://www.vonwentzel.net/Battery/00...ary/index.html

Form for calculating charging system needs including solar/wind input:
http://www.westmarine.com/pdf/Elecbugt.pdf

A lot of info on battery system integration and monitoring INCLUDING some excellent diagrams under the design links. Note this is a commercial site so they recommend their own products...but the designs and info are pretty generic.
http://www.amplepower.com/primer/index.html

Hope you find this useful. You should be done reading by springtime!

Oh yeah...the only other thing I would add is that no matter what your eventual system design, get yourself an appropriate model "Link" battery monitor so you can see your charging amps/charging volts/ amp hour use and manage your system once it is in. Great product!
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Old 02-02-2007
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The most important thing to remember is how the bank(s) will be used. That by default will answer the question you are asking.

Deep Cycle batteries in general like to live with discharge rates <50% of capacity. When cruising sailors typically discharge to 50% then charge back to 85% [most efficient part of the cycle] because roughly if it takes 1X to charge from 50 to 85% then it will take 3X to get to 100% with X being an increment of time.

That means if you start separating the batteries into individual banks [cause if they are in parallel you can't measure them individually] then you have very little capacity for each 'bank' and will be charging all the time. i.e. if each battery is 100 Ahrs than you can only discharge one by 50Ahrs before you start charging. While if all 4 are one bank and they are 100Ahr batteries then you have a 400 Ahr bank. Discharge can be 200 Ahrs before you have to charge. Also charge rates are determined by bank size as well. Typically 25% of bank capacity so our 100 Ahr bank can only handle a 25 amp charger while the 400 Ahr bank can handle a 100 amp charger.

As mentioned above having a good Ahr meter is the real key to managing you bank.
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Old 02-02-2007
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Basically, I'm trying to design a DC-only, 'KISS' system to meet my "somewhat" minimal power requirements - no refrigeration, autopilot, watermaker, radar, chart plotter, windlass, or water heater; and all LED/CF exterior/interior lighting.

I will have no major AC appliances - microwave oven, blender, toaster, etc. Just self-powered, battery operated stuff. So I'm sure I can do just fine without an AC panel/plugs.

On the other hand, I will have laptop computers and a car DVD player with a 20" LCD monitor and speaker system. All of it running at the same time for hours on end.

I hope to spend 90 percent of my time sailing/on the hook, and 10 percent hauled or at the dock for repairs/maintenance/fueling. So I want to be able to use both European and U.S. shore power to charge all batteries and operate AC power tools. If possible, I would like to accomplish this using extension cords, a voltage converter of some kind, and a power strip.

I didn't mean to give the impression that I have huge power requirments. No, I don't have two gensets. I plan to charge batteries by running the engine (obviously), and by using an AirX wind generator. I will have a Honda 2000 portable generator for backup. I will add solar panels for the South Pacific at a later date.

The thing that confuses me the most are the multi-stage "smart chargers" that can handle "three banks." If I use just three batteries instead of four: two house and one crank, there would be no need to connect the two house batteries in parallel, right? The charger could handle/monitor all three as if they were seperate "banks"? But then I would have to add a battery selection switch to choose between the two house batteries, and remember to use it. Wouldn't this be 'bulletproof' and best for the batteries?

Then, I could add a digital multifunction battery monitor, built right into the custom electrical panel, that could switch between the three batteries. While I'm at it, I could incorporate the AirX wind generator's custom control panel and 'stop switch' directly into the main electrical panel.

If this makes sense, I'm still left with a thousand questions about how to hook it up. Back to reading!

Thanks for the advice and links.
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Old 02-02-2007
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A smart charger is simply one designed to charge deep cycle batteries in the most effiecent manner. As you expect to be rarely connected to shore power, I think you're over designing things a bit. More important is how you're engine will charge the batteries. The best setup, IMHO, is a high output alternator with an external 3 stage regulator. Also, if you have the room and engine capacity, you can run a second alternator for just the start battery.

Remember KISS means to keep it simple, not overly complicate it. Also, running a laptop and dvd for hours on end, will not be a minimal drain on your batteries. If you have room for a 3-4 battery house bank, I would install it.

As to your Wind X stop switch at the control panel, you'll be running at minimum 8 gauge cables to and from it, and quite probably 6 for that length of a run. Below is how I installed my switch. That way it is easy to get to to turn on when I shut down the engine, and vice-a-versa.
Attached Thumbnails
Battery Monitoring/Chargers-windgeneratorswitch2.jpg  
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Old 02-02-2007
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Quote:
Originally Posted by svsirius
That means if you start separating the batteries into individual banks [cause if they are in parallel you can't measure them individually] then you have very little capacity for each 'bank' and will be charging all the time.
Now I get it. I was thrown off by marine electricians who warned me against hooking up batteries in parallel. I now see that there is no better option.

I'm gonna figure my daily Amp Hour consumption at a liberal 150.

According to what I've read, this would necessitate a battery bank with at least a 375 Ah rated capacity, minimum. An even larger bank will allow longer times between charges, providing added charging flexibility, and a higher rate of charge, which in turn will reduce charging times and engine hours?

If correct, that would be a house battery bank of around 400 Ah.
Now I'm looking at 4 Lifeline batteries at 100Ah each. Hooked-up in parallel with their own smart charger. And a 100 amp engine alternator to provide maximum-rate charging in the minimum possible time.
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Phyllis...bad idea to break up house into multiple banks. One big parallel bank of 4x your daily amp needs will work best AND prolong your battery life. Your second bank should be of the same TYPE battery (flooded,AGM etc.) and used for starting only. Use a 1/2/both/off switch and monitor the whole thing with a link20 or 2000. Batteries RARELY fail and when they do it is usually because they are treated poorly because of complex systems and improper and innefficient charging systems. KISS works for battery bank design too!

OK so that is the 12V system...now how to charge it PROPERLY given your plans:
From the engine:
1. Get an oversized engine alternator and keep the existing one for a spare. Especially if you get AGM batteries...this will allow you to charge them quickly and minimize damaging engine running time without a load.
2. Get a smart 3 stage regulator that can be set for the proper charge cycle for your bank.
From the charger:
1. Not clear to my why you need a 110/220V smart charger. But in any event get one that can deliver 1/2 your daily amp usage in an hour AND which can also deliver an EQUALIZING charge to your banks...as well as bulk,acceptance and float charging for your type batteries.
2. Suggest you put a marine AC plug in your hull and wire directly to your charger (with an appropriate breaker) since that will allow you to securely charge with an appropriately grounded system. Once you've gone that far it is a pretty simply thing to wire in a standard outlet or two as well, but that is your choice.
3. If you need the 220v for the caribe..know that the 220V countries marinas all have transformers that will let you charge from a standard us 110v marine plug. (It is 50hz but chargers don't seem to mind!...other stuff does but you won't be carrying any of it!!)
4. If you need the 220V for Europe...suggest you read Jack Tyler's Europe prep paper as it is more complex!
http://www.svsarah.com/Whoosh/Whoosh%20Main%20Page.htm

Charging from the Honda:
1. If you add the input plug suggested above, you just need an adapter cable to plug it in and treat it like dockside power.

Charging from wind/solar...
1. Get a voltage regulator that will handle both solar and wind and then wire it into your battery switch to give you flexibility in charging.
2. Have you already bought the Air-x? Reputation is rugged but very noisey.
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