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Old 08-24-2012, 03:05 PM   #1
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Question Battery Help

I have a 300 Amp 12 volt alternator on my 6v92 Eagle Bus power plant with 3-12volt starting batteries. The 300amp keeps them fully charged, but I have 4-8D AGM batteries for house that powers a 12 volt inverter. How do I run the same 300 to keep house batteries up and floated off with same 300 amp source without messing up the starting batteries? Help!!!!

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Old 08-24-2012, 03:20 PM   #2
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You cannot do it with the inverter. You are going to have to feed the house batteries off the 300 and have a switch to transfer and then cut off when charged. Those big boys will hold charge for quite a while. Wire the batteries with a manual cutoff switch and moniter the drain. That will tell you the frequency to set the charge.

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Old 08-24-2012, 03:22 PM   #3
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You can add a large relay that powers up with ignition that then is wired to the batteries and alternator. Whenever the ignition is on and the engine running the relay allows charging of the house batteries.They can be had on line or at camping world.
There are also solid state dividers that are in effect a large diode but there is a small voltage drop across them.
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Old 08-25-2012, 07:14 AM   #4
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First I would look up the charging requirements for the AGM's. Now do the same for the starting batts. I believe you will find that the requirements are quite different, and that you run the risk of the agm's entering early death if not charged correctly, and certainly not cabled to lead acid batts without some kind of voltage limiter.

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Old 08-25-2012, 09:49 AM   #5
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Oh, I see, a bus converted into a motor home...

Visit your RV parts place and discuss a device called an ISOLATOR. Now one word of warning: If your bus uses a 24 volt system, disregard this, the bus must use a 12 volt sytem for this to work.

The isolator (There are two types and several sub types) is either a RELAY (Solenoid or contactor at the kind of current we are discussing) or a Diode box (I recommend the former)

A diode box is 2 or 3 "one way" valves for electricity, they let alternator power flow TO the batteries, but do not let power flow battery to battery. They do, however, introduce voltage loss, so the 3rd one-way valve is for the voltage regulator, Many alternators today the regulator is internal and these will nto work well with a diode box.

The solenoid is an automatic switch, IT usually has a delay, You start the engine, the timer counts down and CLUNK, the batteries are now in parallel.

Some of them have a bi-direcitonal system.. You plug into shore power, the house batteries charge and when they are near full... CLUNK, the batteries are parallelled.

This is the best kind, called a BIRD (BI Direcitonal Relay Device) as 2 weeks after you pull into the campgroudn you go to start the bus back up.. and it starts.
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Old 08-25-2012, 10:32 AM   #6
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Here's some info from Optima on the AGM batteries: Optima Battery Charging - AGM Battery Charging

'02 Winnebago Journey DL, DSDP, 36' of fun.

Visit my RV Travel & Repair Blog at : http://chaos.goblinbox.com
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