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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> Charging a Dual Battery Setup - Question
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Charging a Dual Battery Setup - Question - 2/2/2008 7:34:43 PM   
BalsaBob



Posts: 622
Joined: 2/24/2002
From: Salem, MA, USA
Status: online 		I am using a dual battery and dual switch harness setup (with a single receiver). No voltage regulators .... just one harness plugged into the reciever's battery port and the other into a spare/unused channel. I had heard, that when charging these batteries simultaneously (I'm using a charger that has dual battery capability), that one battery should be unplugged from the receiver .... even though both switch harnesses are OFF. Failure to unplug one of the batteries may generate a premature peak charge detection or some other innaccurate charge reading(s). Anyone else heard this ? ? Thanks. Bob

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RE: Charging a Dual Battery Setup - Question - 2/2/2008 7:38:46 PM   
Josey Wales



Posts: 4615
Joined: 7/27/2003
From: **, NJ, USA
Status: offline 		Yes--its called a common ground--some chargers are ok with this but most are not.

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Joe
I''''''''m a magician, every day I turn into my driveway.

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RE: Charging a Dual Battery Setup - Question - 2/2/2008 10:18:58 PM   
BalsaBob



Posts: 622
Joined: 2/24/2002
From: Salem, MA, USA
Status: online 		Thanks Joe. Is there a way to know if my charger is OK .... or should I just unplug one battery ... to make sure. thanks again. Bob

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RE: Charging a Dual Battery Setup - Question - 2/2/2008 10:21:40 PM   
Josey Wales



Posts: 4615
Joined: 7/27/2003
From: **, NJ, USA
Status: offline
quote:

ORIGINAL: BalsaBob

Thanks Joe. Is there a way to know if my charger is OK .... or should I just unplug one battery ... to make sure. thanks again. Bob


No way to tell unless you try it or check with the manufacturer--if your not sure then just unplug one to be safe.

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Joe
I''''''''m a magician, every day I turn into my driveway.

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RE: Charging a Dual Battery Setup - Question - 2/10/2008 5:26:04 PM   
Sewerdude



Posts: 634
Joined: 6/1/2002
From: LaPorte, IN, USA
Status: offline 		If both switches are in the OFF position. How can any charge or electricity get to the receiver? If the switch IS in the off position, arent the batteries isolated from the rest of the plane? So, I dont see a reason to unplug anything. I use a JR or MPI switch with a built in charge jack. If I'm wrong please correct me. I'm going with a dual battery system myself.

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RE: Charging a Dual Battery Setup - Question - 2/10/2008 6:06:22 PM   
Josey Wales



Posts: 4615
Joined: 7/27/2003
From: **, NJ, USA
Status: offline 		The switch only turns the pos lead on and off. The negative line is always connected no matter if the the switch is on or off.

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Joe
I''''''''m a magician, every day I turn into my driveway.

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RE: Charging a Dual Battery Setup - Question - 2/10/2008 6:21:37 PM   
JNorton



Posts: 3133
Joined: 1/29/2002
From: Montague, MI, USA
Status: offline 		If the dual charger has a common positive and the receiver switch harness connects both batteries negative leads together you can short the chargers outputs. Let the smoke out and you have problems.
John

EDIT-> when researching dual battery chargers look for one that has isolated outputs. These will run with the batteries connected.

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RE: Charging a Dual Battery Setup - Question - 2/10/2008 7:08:35 PM   
Sewerdude



Posts: 634
Joined: 6/1/2002
From: LaPorte, IN, USA
Status: offline 		Ok, I think I understand now. I have the Hobbico Accu-Cycle Elite. Not sure if I can use this charger to charge both at the same time. Thanks

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RE: Charging a Dual Battery Setup - Question - 2/10/2008 7:09:34 PM   
Josey Wales



Posts: 4615
Joined: 7/27/2003
From: **, NJ, USA
Status: offline
quote:

ORIGINAL: Sewerdude

Ok, I think I understand now. I have the Hobbico Accu-Cycle Elite. Not sure if I can use this charger to charge both at the same time. Thanks


No it wont--dont ask me how I know

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Joe
I''''''''m a magician, every day I turn into my driveway.

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RE: Charging a Dual Battery Setup - Question - 2/10/2008 7:13:28 PM   
Sewerdude



Posts: 634
Joined: 6/1/2002
From: LaPorte, IN, USA
Status: offline 		Ok, I think I have a feeling what happened Josey. Glad I found this thread or I could of had some trouble I believe.

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RE: Charging a Dual Battery Setup - Question - 2/11/2008 4:23:34 AM   
Flying Geezer



Posts: 1004
Joined: 4/12/2003
From: Bowling Green, KY, USA
Status: offline 		Actually John, dual chargers do not have a common positive. They have the negative of the battery above ground with the current sensing resistor between the battery negative and true ground.

When the current sensing resistor is on the battery negative this called "negative side current sensing". Chargers with "positive side current sensing" have the current sensing resistor between the postive charging voltage and the battery positive.

Keeping in mind that the current flows from the negative to the positive, more current will tend to take the path of least resistance through one of the current sensing resistors and that particular battery.

Think of it this way, when you plug in batteries with a common ground, you have effective wired the sensing resistors in parallel, between the two batteries common connection and the ground side of the charger.

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Flying Geezer
Hughes RC

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RE: Charging a Dual Battery Setup - Question - 2/11/2008 11:56:44 AM   
JNorton



Posts: 3133
Joined: 1/29/2002
From: Montague, MI, USA
Status: offline
quote:

ORIGINAL: Flying Geezer

Actually John, dual chargers do not have a common positive. They have the negative of the battery above ground with the current sensing resistor between the battery negative and true ground.

When the current sensing resistor is on the battery negative this called "negative side current sensing". Chargers with "positive side current sensing" have the current sensing resistor between the postive charging voltage and the battery positive.

Keeping in mind that the current flows from the negative to the positive, more current will tend to take the path of least resistance through one of the current sensing resistors and that particular battery.

Think of it this way, when you plug in batteries with a common ground, you have effective wired the sensing resistors in parallel, between the two batteries common connection and the ground side of the charger.

I realise that but I've seen so many configuation of chargers that it is mind boggling, as no doubt you have too. I've been an electrical engineer for the last 30 years. It is much simplier to explain. When I used to post on this forum frequently I had the habit of trying to explain exactly what was happening and confused more people than I helped. I understand exactly what you are talking about but how many other people do? Try explaining a switching regulator sometime to someone with no electronic background. Then throw in the differences between a buck and a boost configuation. Enough said. Sorry if I took too many liberties I just thought the concept was easier to grasp.
John

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RE: Charging a Dual Battery Setup - Question - 2/12/2008 4:53:45 PM   
Tony Gag Jr.



Posts: 572
Joined: 1/21/2002
From: Terryville, CT, USA
Status: offline 		Bob,
You can use this product from ElectroDynamics. If you read under the tech note is says you can use any multi charger to charge two batteries. Not sure if it works but it sounds good to me.

http://electrodynam.com/rc/EDR-108/index.shtml#108T


Tony

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RE: Charging a Dual Battery Setup - Question - 2/12/2008 10:43:16 PM   
BalsaBob



Posts: 622
Joined: 2/24/2002
From: Salem, MA, USA
Status: online 		Thanks Tony, and all, I made the connections between the batteries and the switch harnesses easily accessable .... they are real quick-easy to unplug. Bob

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RE: Charging a Dual Battery Setup - Question - 4/7/2008 10:00:42 AM   
bodywerks



Posts: 3090
Joined: 12/10/2004
From: Tucson, AZ, USA
Status: offline 		So has anyone discovered a charger capable of charging two receiver packs in a common ground system without the need for any special switches or unplugging one battery in the system??
I have the AR9100 with dual A123's plugged directly into the receiver, no switches. Each battery has its own seperate charge lead plugged int an Earnst charge recepticle. I want to be able to charge them both at the same time, at the field, without having to pull the hatch and unplug a battery every time.
I am really sup