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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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Old 08-24-2009
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I think it is relevant to the op so I would add this -
think of what happens to resting voltage when you pull 50% out of a battery vs 25%. The only reason both (in his bank) remain at the same voltage is because they are interconnected - the small one is actually competing with the larger.
No matter how you slice it, when you pull amps out of a bank, each battery loses half the amount. When one is smaller than the other, it suffers disproportionately.
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Old 08-24-2009
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k1vsk - I respectfully disagree with your logic. You don't pull half the amps from each battery. More current flows from the larger battery than the small one. This is regulated by the voltage from each. If the voltage starts to drop in one battery (because it is smaller) it will just supply less current until the voltages are equal again. When charging, if one battery received more current, the voltage would rise in that battery and current going into it would decrease. It's a completely self regulating system.

This is a very important point -> It is true that you should not mix and old battery with a new one, but this is more like mixing types (AGM, wet, or gel) than anything to do with size. As a battery ages the chemistry changes.

There is no difference in a system with one large and one small battery than a system with many batteries. For example with a 6 battery setup, from the prospective of any single battery there is no way to tell that it is connected to 5 others or one that's 5 times larger than it. The entire system acts as one large battery.
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Old 08-25-2009
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Here's what I've got.

The alternator is a 110A Balmar with a Balmar MC-612 Regulator

There are a total of three batteries:
Two are Lifeline 4D – 210AH, and one Lifeline Group 27 – 100AH. All three are gel batteries.
The battery configuration switch configuration is:
Position “1” – 4D & Group 27 in parallel
Position “2” – 4D

The monitor is a Xantrex Link 20

I don't have the info on the AC charger at this time. But I don't think that is important since I'm experiencing the same conditions.

Next time at the boat I am going to check the Link 20 configuration to be sure it was set properly in the first place.

Thanks for everyone's comments. Of course there are many opinions. I'll sort them out and see what happens.

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Old 08-25-2009
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The first thing you should check is the regulator output setting to see if measured voltage is consistent and do so when the batteries are NOT fully charged.
Additionally, make sure the Link20 rate is properly set and calibrated.

Regardless of the varying opinions with respect to battery configuration between Steve and me, no one can contest the over-riding benefit to combine the two larger batteries as a large house bank. Having a separate 200 amp start battery is overkill when compared with your present 300 amp "Position 1" house bank .

The larger the house bank, the smaller the discharge rate resulting in prolonging the life of the batteries.
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Old 08-25-2009
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The manual for your motor should give you the specs for the required starting battery. The group 27 battery is probably sufficient. I agree that rewiring the system so the group 27 is your starting battery and the the two 4Ds are your house battery makes sense. You don't want two house banks, just one large one with an simple on/off switch. Use your 1,2,all, off switch as an interconnect so you can start from the house bank if needed. There are many ways to set up your batteries, but this is a common, modern approach.

Following the steps in the Link 20 manual for battery capacity testing should give you an idea of the health of your batteries. If the actual capacity is was off from the advertised capacity you batteries are on their way out.
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Old 08-25-2009
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I'll bet those batteries are AGM (absorbed glass mat [sometimes material]). Very good batteries btw.

I don't think Lifeline makes gells.

Other than the odd grouping of house batteries - I'll bet there is nothing wrong with your system. I agree with your salesman!

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Old 08-25-2009
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OK, now we're getting somewhere.

First, I agree that it's very likely your Lifeline batteries are AGMs, not gelled cell batteries.

I also agree that the grouping is rather strange, and it would be beneficial at some point to connect the two 4Ds together and run them as a single 420AH house battery bank, and to use the 100AH battery for starting.

You didn't mention a battery combiner or echo charge device. How is the alternator connected?

Since you already have a 1-2-Both-Off switch, an easy way to improve the setup would be:

1. Wire both 4Ds together in parallel, and connect this bank to position #1 on the battery switch.

2. Wire the 100AH battery to it's own ON-OFF switch and to the start solenoid.

3. Run a cable from the the new ON-OFF switch to position #2 on the battery switch.

4. Install an EchoCharge or DuoCharge device, connected between the house bank and the start battery. This device is completely automatic, and bleeds some of the charge off the house batteries to keep the start battery charged.

5. Connect the output of the Balmar 110A alternator -- and all other onboard charging sources (battery charger, generator, wind, solar, etc.) to the house battery bank.

6. Leave the switch in the #1 position. The "BOTH" position would be only for those very rare times when the start battery is depleted and you want to start from the house batteries.

Now, about the original question re: charging amperage.

There may or may not be something amiss. AGMs can absorb A LOT of amperage...all your 110A alternator can throw at them...and more. The MC612 controls how much amperage is going to the batteries, based on its internal charging algorithm ("program") and upon external factors such as battery voltage, battery temperature, and alternator temperature (assuming these sensors are fitted).

It's really a quite sophisticated system, and works beautifully once set up correctly. There are some potential bug-a-boos, though.

In order for things to work correctly, you need:

1. the correct program chosen in the MC-612 (i.e., PO4 AGL);
2. all sensors correctly connected and working properly;
3. adequate size wiring;
4. clean, tight connections; and
5. alternator belt tensioned properly and not slipping.

The best way to easily check re: output is probably to take the boat out, drain the house batteries to about 50% charged state (about 12.3VDC with NO LOAD and NO CHARGE after sitting for several measured with a reliable multimeter AT THE BATTERY TERMINALS).

Then, when you start the engine, after 40 seconds or so you should see the amperage ramp up to somewhere over 80. If you see this, then the system would seem to be basically OK. However, if you only see 10A or so, something is definitely wrong.

Note that temperature sensors can give improper readings. If you suspect a bad temp sensor, just pull it's connector off the MC-612 and see what happens.

Finally, don't worry about the readings you get from the battery monitor -- at least not until you know it's been properly calibrated and you've lived with it awhile. These things can be good, but they can also give very misleading information.

Sorry to be so long-winded. Hope this helps a bit.


Last edited by btrayfors; 08-25-2009 at 02:45 PM.
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