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post #11 of 20 Old 03-13-2013
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Re: cranking battery

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Originally Posted by PorFin View Post
I'm dubious. An inverter takes 12v DC from the batteries and converts it to 110v AC. If your battery charger is being run off of the inverter, you have a real problem.
Many inverters are also chargers. Magnum, Xantrex, Mastervolt and other companies produce them. It is actually hard to find a serious inverter that is not also a charger. Chargers larger than 60 amps are almost impossible to find - except for those built into inverters.

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post #12 of 20 Old 03-13-2013
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Re: cranking battery

Good point, Brian. You are likely on the money about it being an inverter/charger and not just an inverter.


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post #13 of 20 Old 03-14-2013
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Re: cranking battery

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Originally Posted by mitiempo View Post
The inverter /charger, at least any I have seen or installed, has a single DC output which is also its DC input. For it to also charge the start battery you would need to have a device like an Echo Charge, Balmar DuoCharge, or an ACR or other type of combiner. If you do not have one of these devices you would have to leave the main battery switch in both for the start battery to receive a charge.

Could this be the issue?
Even if you do have both hooked to the charger that could cause a problem if it's not properly regulated.

Your 4 6v's have a completely different need and hence voltage requirement than your start 12v.
Sending a constant trickle to the (I'm assuming these are standard 6v golf carts batts) 400 or so amp hour house AND the same trickle to the 12v would boil off water in the start.
IMHO.
That's why both banks need to be on separate chargers.

Overall though, a battery that is fully charged at the beginning of a winter season should retain enough charge to still crank a engine. It certainly should not die unless something else is wrong.

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post #14 of 20 Old 03-14-2013
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Re: cranking battery

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Originally Posted by chucklesR View Post
Even if you do have both hooked to the charger that could cause a problem if it's not properly regulated.

Your 4 6v's have a completely different need and hence voltage requirement than your start 12v.
Sending a constant trickle to the (I'm assuming these are standard 6v golf carts batts) 400 or so amp hour house AND the same trickle to the 12v would boil off water in the start.
IMHO.
That's why both banks need to be on separate chargers.

Overall though, a battery that is fully charged at the beginning of a winter season should retain enough charge to still crank a engine. It certainly should not die unless something else is wrong.
Not true at all UNLESS the absorption and float voltages are vastly different as in GEL vs. AG or Flooded. Most flooded batteries can be charged at the same voltage regardless of start or deep cycle.

Even "multiple output" two or three bank chargers send the SAME voltage to each bank.... Many people are totally unaware of this....

I suspect the OP has a parasitic leak or he is simply not charging the start battery at all. He really needs to test for this and map out his wiring.

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post #15 of 20 Old 03-14-2013
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Re: cranking battery

Thanks for straightening me out on that one MS.

I think sometimes I think to much (see, there I go again).

Now I have to figure out why my start battery died (Optima spiral, same as the 3 house).

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post #16 of 20 Old 03-14-2013
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Re: cranking battery

Chuck,

Most all "smart battery chargers" have one single voltage set point and one power supply. The power supply is often divided into two or three outputs. These outputs are diode protected so that current from one battery won't drain into another but you still only have one charge algorithm and one power supply.

So there are a couple of scenarios:

1- House bank is low and charger is in bulk. Bulk is ANYTHING below the absorption voltage limit. If the charger has not yet brought the house to absorption, and is in bulk, the start battery is seeing the same voltage because it is on the same power supply. The power supply is held at that voltage by the larger bank.

2- When the house bank reaches absorption the start battery will also be at this voltage. The charger will then run its course and hold at absorption for a predetermined or calculated time.

3- The battery decides the current it accepts at a certain SOC and voltage. All the charger does in modulate the current output so as to not over shoot the voltage set points. You can very easily have a house bank taking 99.6% of the chargers output and the start battery getting just .4% but both batteries will be at the same charger output voltage.

While there are some newer chargers that can charge a start battery independently of a house, with a different algorithm, they are spendy. Sterling Power is about to launch some DC - DC modules that can be connected to any charger to give the start bank a true "independent charge"... The new Blue Sea chargers are supposed to do this too but they've not yet shipped one.

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post #17 of 20 Old 03-16-2013 Thread Starter
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Re: cranking battery

SAGA 35 HULL # 10 Wind Song. Can any one tell me what position the emergency switch, house battery switch and start battery switch should be in during winter moorage with the boat on shore power. It appears to me that if the start battery is isolated and or if the start battery switch is off that the start battery does not charge from shore power.
I am not sure that I really understand the purpose of the emergency switch. Is it just to isolate the start battery from the house bank so it does not discharge while using the house bank?
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post #18 of 20 Old 03-16-2013
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Re: cranking battery

This is nearly impossible to answer without knowing your wiring. As a very general and unreliable answer, the house and start would be on and the emergency would be off. I expect your emergency is to allow your house bank to be used as a start battery, but I actually have no idea how yours is set up.

Whether you have a charger on both banks is also tough to say. Every boat is wired differently, even from the factory fromm year to year or boat to boat, depending on the order. Add the potential that an owner modified her along the way and no one can say without seeing how she is laid out. Sorry.


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post #19 of 20 Old 03-16-2013 Thread Starter
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Re: cranking battery

SAGA 35 HULL # 10 Wind Song. Can any one tell me what position the emergency switch, house battery switch and start battery switch should be in during winter moorage with the boat on shore power. It appears to me that if the start battery is isolated and or if the start battery switch is off that the start battery does not charge from shore power.
I am not sure that I really understand the purpose of the emergency switch. Is it just to isolate the start battery from the house bank so it does not discharge while using the house bank?
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post #20 of 20 Old 03-16-2013
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Re: cranking battery

The only way to know for sure is either to trace the wires and draw a schematic or hire an electrician to do it for you.

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