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Author Topic: dual battery options  (Read 8075 times)
KJ4SKP
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« on: February 23, 2012, 06:22:10 AM »

I have an 07' jeep JK that I run a yaesu ft 8900 in.   I am interested in a buying a dual battery set up to run the Yaesu and some lights.   Does anyone have a  dual battery tray/set up they could recommend?
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K0BG
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« Reply #1 on: February 23, 2012, 06:38:10 AM »

My first question is why? Running any transceiver off just a battery without any charging path, is a can of worms. The main reason is, it doesn't take long for the battery voltage to drop to a point that the radio will shut off on its own. The output power will also be somewhat less. That can be eliminated by using a battery booster, but then you reach the specter of upsetting the engine CPU when you suddenly connected a battery with a depleted SOC. In other words, not something you want to do with out weighing all of the issues.
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KJ4SKP
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« Reply #2 on: February 23, 2012, 07:03:14 AM »

I've heard some operators talk about running the dual battery route in order to prevent your radio from drawing power from your car starting  capability.  When using crossband repeat the mobile rig remains on and when I'm in the middle of nowhere I wouldn't want my car battery to run down to the point of not starting my car because the radio drained it's power.
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KD8HYN
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« Reply #3 on: February 23, 2012, 07:23:34 AM »

There is a product out there, I think Galls and/or JC Whitney have it, it goes in series with your positive battery cable and is sort of a low-voltage circuit breaker. If I remember correctly it cuts power if the battery gets too low so you'd be able to still start the engine and recharge.

Not exactly what you're looking for but it'd be an option.

I was under the impression that it was more or less running a marine battery in parallel with the starting battery and the vehicle's charging system did keep both in check.
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W8JX
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« Reply #4 on: February 23, 2012, 10:59:48 AM »

I've heard some operators talk about running the dual battery route in order to prevent your radio from drawing power from your car starting  capability.  When using crossband repeat the mobile rig remains on and when I'm in the middle of nowhere I wouldn't want my car battery to run down to the point of not starting my car because the radio drained it's power.

I think it is a excellent idea. The biggest problem with JK is figuring out where you want to mount extra battery. Get you a battery box for a big deep cycle battery and bolt it down in car somewhere. Next run wire to power radio to at and finally connect battery to car electrical system to charge it. No need to go crazy here with wire size for charging it as 10ga is more than enough. A simple safety interlock it to get a HD 12 volt relay and hook coil to ignition hot. Then wire through relay so when it is closed under power it charges battery and when car is off main battery is safe. No need for a fancy isolator. You could even place a switch in series with ignition power feed to relay coil if you want to disable it or use it to manually energize coil to strap both systems together for longer battery time for car lights in a emergency or longer radio time.
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MDNITERDER
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« Reply #5 on: February 23, 2012, 11:09:27 AM »

Get a battery isolator, it allows you to charge two batteries and and isolate there drain. JCwhitney or most autoparts stores.

 John
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WX7G
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« Reply #6 on: February 23, 2012, 01:56:20 PM »

http://www.jegs.com/InstallationInstructions/700/713//713-903.pdf

Here are the instructions for a Power Master Universal Battery Isolator sold at JEGS.

It looks to be a lot of trouble to connect. A very simply way to go is to place a sealed headlamp in series with a 10 amp switch. The switch is normally closed to charge a  radio battery. The headlamp limits the current when the discharged radio battery is reconnected to the auto battery.

An MFJ-4416B battery voltage booster is used to supply 13.8 VDC to the radio as the radio battery discharges as low as 9 volts.
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W8JX
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« Reply #7 on: February 23, 2012, 02:38:21 PM »


An MFJ-4416B battery voltage booster is used to supply 13.8 VDC to the radio as the radio battery discharges as low as 9 volts.


I question the value of this because a deep discharge will shorten life of battery and the device itself consumes power. Also radio does not need 13.8 volts all the time here. Some loose some output but most do well down to less than 12 volts and power loss is not critical.
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WX7G
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« Reply #8 on: February 23, 2012, 05:06:19 PM »

A 12 volt lead acid battery can be discharged to 10.5 volts without significantly shortening its life. It would be nice if the MFJ booster would disconnect at 10.5 volts but it doesn't.

In this case one can run the repeater directly off the battery and get short operating time or run it off the MFJ booster and get longer operating time.

One must decide what the goal of all of this is; communications or battery collecting.
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KE5PPH
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« Reply #9 on: February 23, 2012, 06:59:28 PM »

check at 4 wheel parts or Quadratech, for dual battery set-ups.  Don't go cheap on your Jeep.
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W8JX
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« Reply #10 on: February 23, 2012, 07:42:14 PM »

A 12 volt lead acid battery can be discharged to 10.5 volts without significantly shortening its life.

Really that depends on battery because pull a car battery down to that several times and it will likely be junk of have limited capacity. Also you should not go below 10.8 volts or 1.8 volts a cell. Some battery makers use 10.5 volts when determining capacity because it lets them squeak out a few more amp for rating.
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K0BG
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« Reply #11 on: February 24, 2012, 06:06:36 AM »

While battery companies often stretch the truth about their product lines—using the phrase deep discharge for example—the BCI uses 10.5 volts as the standard charge/cycle SOC limit with respect to published ratings.
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W8JX
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« Reply #12 on: February 24, 2012, 06:18:14 AM »

While battery companies often stretch the truth about their product lines—using the phrase deep discharge for example—the BCI uses 10.5 volts as the standard charge/cycle SOC limit with respect to published ratings.

And they do because it makes battery look better capacity wise. (squeezing a little more out of the sponge) I use 11 volts under load as my cut off.
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W9MMS
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« Reply #13 on: February 24, 2012, 08:53:33 AM »

I have an 07' jeep JK that I run a yaesu ft 8900 in.   I am interested in a buying a dual battery set up to run the Yaesu and some lights.   Does anyone have a  dual battery tray/set up they could recommend?

Jonathan, My suggestion would be to visit a Jeep specific Forum in seeking what other Jeepers are using out there on the trail that has been proven under adverse conditions.
Try "Rubicon Owners Forum" for where they obtain battery trays and what are they using with their 'Winch and Lights"
http://www.jeepforum.com/forum/f96/


(((73))) Milverton
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W8JX
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« Reply #14 on: February 24, 2012, 09:44:10 AM »

I have an 07' jeep JK that I run a yaesu ft 8900 in.   I am interested in a buying a dual battery set up to run the Yaesu and some lights.   Does anyone have a  dual battery tray/set up they could recommend?

Jonathan, My suggestion would be to visit a Jeep specific Forum in seeking what other Jeepers are using out there on the trail that has been proven under adverse conditions.
Try "Rubicon Owners Forum" for where they obtain battery trays and what are they using with their 'Winch and Lights"
http://www.jeepforum.com/forum/f96/


(((73))) Milverton

What works on "trail" for one does not always work for others because any battery will have to be located in passenger compartment somewhere and that needs to be where is is good for poster not where it might be good for someone else. 
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