Charging a Dual Battery Setup - Question (Full Version)

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BalsaBob -> Charging a Dual Battery Setup - Question (2/2/2008 7:34:43 PM)

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



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

Yes--its called a common ground--some chargers are ok with this but most are not.



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

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



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


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.



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

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.



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

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.



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

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.



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

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



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


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[8|]



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

Ok, I think I have a feeling what happened Josey. Glad I found this thread or I could of had some trouble I believe.



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

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.



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


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



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

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



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

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



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

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 suprised this is not a hotter topic, to be honest.
So, anyone know of A123 chargers capable of this? I don't care if it a multiple output single charger, or if I have to buy two chargers.



JNorton -> RE: Charging a Dual Battery Setup - Question (4/7/2008 11:00:11 AM)

Two completely separate chargers will work fine. Do not use a common DC Power supply.
John



Josey Wales -> RE: Charging a Dual Battery Setup - Question (4/7/2008 1:44:30 PM)


quote:

ORIGINAL: bodywerks

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 suprised this is not a hotter topic, to be honest.
So, anyone know of A123 chargers capable of this? I don't care if it a multiple output single charger, or if I have to buy two chargers.


Fromeco is coming out with a 3 port A123 charger that can handle a common ground.



MR G -> RE: Charging a Dual Battery Setup - Question (4/7/2008 1:47:04 PM)

Flying Geezer,

I have been charging both of my RX, Ign batts and my TX batteries with a Charge+ charger from Hughes RC for years.

I understand the common ground situation. I have noticed the Hughes RC in your signature area.

Could you tell me if I have been mistaken all of these years?

Thanks,

MR G



bodywerks -> RE: Charging a Dual Battery Setup - Question (4/7/2008 2:58:23 PM)


quote:

ORIGINAL: JNorton

Two completely separate chargers will work fine. Do not use a common DC Power supply.
John

Funny - as if it were that simple. If you have been getting by like that with known ground-sensing chargers, charging at the same time, then it is purely by luck. I got this response from Robert Ritchey - the owner of Smart-fly. I think he is a reputable/reliable source:
quote:

You CAN charge one battery at a time even with both batteries connected. You CANNOT charge both batteries at once with a single dual-output charger or two separate chargers if they cannot handle the common ground system. These are rules.



bodywerks -> RE: Charging a Dual Battery Setup - Question (4/7/2008 3:05:02 PM)


quote:

ORIGINAL: Josey Wales


quote:

ORIGINAL: bodywerks

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 suprised this is not a hotter topic, to be honest.
So, anyone know of A123 chargers capable of this? I don't care if it a multiple output single charger, or if I have to buy two chargers.


Fromeco is coming out with a 3 port A123 charger that can handle a common ground.

I planned on calling Fromeco today about this, but they already have a 3-port A123 charger. Are you saying that their currently available charger is not common-ground compatible, but that they will have one that is?
I did get official word that their one of their chargers was common-ground safe, straight from Kurt at Fromeco. But the post was from 2006, so I think it was their older charger.
I did see that the Hughes charger will work, but it's $320! I think I'd rather just buy five more sets of A123 batteries and change them out.



Josey Wales -> RE: Charging a Dual Battery Setup - Question (4/7/2008 3:09:46 PM)

quote:

ORIGINAL: bodywerks
I planned on calling Fromeco today about this, but they already have a 3-port A123 charger. Are you saying that their currently available charger is not common-ground compatible, but that they will have one that is?
I did get official word that their one of their chargers was common-ground safe, straight from Kurt at Fromeco. But the post was from 2006, so I think it was their older charger.
I did see that the Hughes charger will work, but it's $320! I think I'd rather just buy five more sets of A123 batteries and change them out.


Their current Ion Cube charger IS able to handle a common ground--they are also coming out with another charger. It will be 3 ports..A123 capable..common ground friendly.. and charge at 10A. This is direct from Kurt about a month ago.



JNorton -> RE: Charging a Dual Battery Setup - Question (4/7/2008 3:10:59 PM)


quote:

ORIGINAL: bodywerks


quote:

ORIGINAL: JNorton

Two completely separate chargers will work fine. Do not use a common DC Power supply.
John

Funny - as if it were that simple. If you have been getting by like that with known ground-sensing chargers, charging at the same time, then it is purely by luck. I got this response from Robert Ritchey - the owner of Smart-fly. I think he is a reputable/reliable source:
quote:

You CAN charge one battery at a time even with both batteries connected. You CANNOT charge both batteries at once with a single dual-output charger or two separate chargers if they cannot handle the common ground system. These are rules.


IT is that simple. Two completely separate chargers are not effect by a common ground because there is no return path in the chargers. A dual output charger is NOT the same as two individual chargers. Individual chargers using separate DC supplies will work. SIMPLE. I've designed these things for a living. I do know what I'm talking about.



JNorton -> RE: Charging a Dual Battery Setup - Question (4/7/2008 3:17:41 PM)

If you have any reservations use an isolation transformer on one or both of the DC Power supplies.



Flying Geezer -> RE: Charging a Dual Battery Setup - Question (4/7/2008 6:53:44 PM)

You have not been mistaken Mr. G. All of our chargers are common ground compatiable. Most chargers are not designed by people who fly.

As far a s being lucky, charging two flight packs with common ground, you can do it for a while in most cases. Most people use nearly identical packs, same chemistry same number of cells. You can charge these many times with the weakest one getting a little less charge each time. Then if you cycle them seperately, that resolves the differential, until you have charged several times again. I don't think it is worth taking the chance. If the packs are substantially mismatched or has a defect, then you may be flying without true redundancy. Or you may burn one up charging them together.

Remember, when you check the voltage on Nickel base batteries it is not necessarily a good indication of capacity. Lithium is different and the acutal state of charge is a little easier to estimate with a loaded voltmeter reading.



dant-RCU -> RE: Charging a Dual Battery Setup - Question (4/7/2008 8:43:35 PM)

I have been charging my dual receiver packs using both ACE DigiPulse and ACE DVCC chargers for 3 years and have never
noticed a problem. I either plug my second receiver pack into a spare slot on the RX or "Y" it with a used slot.

As I said, I have never had a problem doing this that I am aware of.

Works for me (so far).

Dan




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