battery circuit

[Electron_Sam78]

Hey guys, I have a battery circuit in which I have 2 6VDC batteries in series supplying a 12VDC load. However, I need to separate the battereis for charging - they stay in place and are plugged in to 2 separate 6V chargers. I have drawn up an idea to do this using regular 3 and 4-way switches. Look it over and gave any suggestions or improvements such as easier and cheaper :roll:

Charging

normal operation

 

[boboelectric]

Upgrade to a 12 volt system.

 

[Electron_Sam78]

Upgrade to a 12 volt system.

Not an option...well not a cheap one anyway

 

[Security101]

Upgrade to a 12 volt system.

I agree with bobo...

But first, what kind of current needs are you looking for - how many amp hour? Are these an automotive type battery or a sealed lead acid smaller type batery. What are they used for?

I can show you 12vdc battery's for 20 bucks each and a charging circuit/transformer setup for 40 bucks...

What are you doing?

Jim

 

[Rick Christopherson]

It is more complicated than it needs to be. Get rid of the 4-way switch and simply break the circuit and engage the chargers with the two 3-way switches. The bridge between the chargers and batteries can be left closed.

If I was going to do it, I would use a 4-pole, double-throw relay and a single light switch. This would avoid operator error with forgetting to hit multiple switches.

 

[ohm]

Hey guys, I have a battery circuit in which I have 2 6VDC batteries in series supplying a 12VDC load. However, I need to separate the battereis for charging - they stay in place and are plugged in to 2 separate 6V chargers. I have drawn up an idea to do this using regular 3 and 4-way switches. Look it over and gave any suggestions or improvements such as easier and cheaper :roll:

Charging

normal operation

Why not buy two 6V automatic chargers and leave them on all the time. Not only will you eliminate the labor & material for the switches you will not have to worry about charging & testing.

 

[djohns6]

Why do you have to seperate the two batteries ? Can't you just connect a 12v charger across the circuit and rock on ?

 

[Cold Fusion]

Following on post 5 and post 7, with the 4way in Normal and both 3ways in Charge, you have the two batteries in series connected to the two chargers in series. Polarity is okay, no issue there.

Are the charger outputs isolated from ground? If not, that could be a problem.

If they are isolated, then, as already mentioned, the ckt can be simplified significantly.

cf

 

[Rick Christopherson]

Why do you have to seperate the two batteries ? Can't you just connect a 12v charger across the circuit and rock on ?

Because you could overcharge one of the batteries, which is the quickest way to kill a battery.

Are the charger outputs isolated from ground? If not, that could be a problem.

Good call. This was in the back of my mind, but didn't click right away.

 

[GizmoBreaker]

one switch

one switch

How about this? You buy a single two pole switch. One pole interrupts the connection between the batteries. The other pole interrupts the positive wire that goes to the load. Now when you charge the batteries, the load is disconnected from the chargers and the batteries are no longer in series.

Your drawing implies that the chargers are connected all the time, so there would be some back-feeding of the chargers by the batteries - the batteries are trying to power the chargers. However, this current is tiny and the chargers are probably protected. You don't mention the charge rate, but if it is reasonably low, you could install diodes to protect the chargers. Even Radio Shack carries 6amp diodes. They also have 25 amp diode bridges which are essentially 4 diodes in a single package - you can use 2 of them without any cross-connect.

 

[Cold Fusion]

Because you could overcharge one of the batteries, which is the quickest way to kill a battery. ---

I would think one could use a 12V charger across two 6V batteries. Not much difference between that and a 12V battery across a 12V charger. In either case it's just 6 cells in series.

Sam doesn't want to buy a new charger.

cf

 

[Electron_Sam78]

I agree with bobo...

But first, what kind of current needs are you looking for - how many amp hour? Are these an automotive type battery or a sealed lead acid smaller type batery. What are they used for?

...What are you doing?

Jim

Why not buy two 6V automatic chargers and leave them on all the time. Not only will you eliminate the labor & material for the switches you will not have to worry about charging & testing.

I'm wiring a lighting system (plus a horn) for a 4 wheeled bicycle. The chargers are stationary in the garage and will be plugged into the batteries (not shown by the wiring diagram)

These are sealed lead acid 12AH batteries.

Upgrade to a 12 volt system.

Why do you have to seperate the two batteries ? Can't you just connect a 12v charger across the circuit and rock on ?

I already had the 6V chargers so they were freebies. That's why I went with two 6Vs instead of one 12V.

It is more complicated than it needs to be. Get rid of the 4-way switch and simply break the circuit and engage the chargers with the two 3-way switches. The bridge between the chargers and batteries can be left closed...

Following on post 5 and post 7, with the 4way in Normal and both 3ways in Charge, you have the two batteries in series connected to the two chargers in series. Polarity is okay, no issue there.

Are the charger outputs isolated from ground? If not, that could be a problem.

If they are isolated, then, as already mentioned, the ckt can be simplified significantly.

cf

Would putting the chargers in series damage the circuits of the chargers? They're freebies so I don't want to have to buy a couple of new ones.

Yes they are isolated from ground.

 

[Electron_Sam78]

If I was going to do it, I would use a 4-pole, double-throw relay and a single light switch. This would avoid operator error with forgetting to hit multiple switches.

I could just put all the switches in a three gang box and tie the handles together so that all have to be thrown at the same time.

 

[Cold Fusion]

I'm wiring a lighting system (plus a horn) for a 4 wheeled bicycle. The chargers are stationary in the garage and will be plugged into the batteries (not shown by the wiring diagram) ---.

I can't remember where I saw the article on the guy developing the four person, human powered vehicle. He talked about getting stopped by a cop.

Is that what this is for? If this one or similar, I'm inpressed.

--- Would putting the chargers in series damage the circuits of the chargers? ---
---Yes they are isolated from ground.

The outputs really need to be isolated from the 120V charger input - as in isolation transformer, no case connection.

I wouldn't connect the plus cable on one to the minus on the other. If you are wrong, it will kill the one with the connected plus cable.

Look at a wiring diagram if available. Measure each cable to the charger case (assuming a 3Wire cord). Measure between the plus cable on one to the minus on the other. This should tell you if the output is truly isolated from the input.

Good luck - great project.

cf

 

[Brian Oshman]

The switches are not necessary. You can connect both chargers to both batteries and they will just charge them. When they are not powered on the 120v pri. side the batteries will not backfeed the chargers due to the diode rectifier built into the chargers. They will only allow the chargers to charge the batteries but not allow backfeeding to discharge the batteries when the chargers are not powered.

I take it that you want to permanently install the chargers on the bike or are you just going to connect them when charging is necessary? You can just directly connect them as when the load is off the batteries are both sitting idle and will charge independently of one another.

Less is more.

 

[Electron_Sam78]

I can't remember where I saw the article on the guy developing the four person, human powered vehicle. He talked about getting stopped by a cop.

Is that what this is for? If this one or similar, I'm inpressed.


The outputs really need to be isolated from the 120V charger input - as in isolation transformer, no case connection.

I wouldn't connect the plus cable on one to the minus on the other. If you are wrong, it will kill the one with the connected plus cable.

Look at a wiring diagram if available. Measure each cable to the charger case (assuming a 3Wire cord). Measure between the plus cable on one to the minus on the other. This should tell you if the output is truly isolated from the input.

Good luck - great project.

cf

It's actually a 4 wheeled cycle made out of PVC. Check it out: http://www.americanspeedster.com/side-kick.htm

 

[ohm]

The switches are not necessary. You can connect both chargers to both batteries and they will just charge them. When they are not powered on the 120v pri. side the batteries will not backfeed the chargers due to the diode rectifier built into the chargers. They will only allow the chargers to charge the batteries but not allow backfeeding to discharge the batteries when the chargers are not powered.

I take it that you want to permanently install the chargers on the bike or are you just going to connect them when charging is necessary? You can just directly connect them as when the load is off the batteries are both sitting idle and will charge independently of one another.

Less is more.

Right on Brian. All but the cheapest chargers have isolation transformers and if they are automatic won't overcharge.

 

[Electron_Sam78]

These chargers are taken out of an emergency light fixture. They charge a 6 volt sealed lead acid battery (it should have no problems with a 12AH right?). I was originally planning on having the chargers sit in the garage while the bike was out and plug it in when it came back but I guess I could wire them into the bike circuit.

 

[ohm]

These chargers are taken out of an emergency light fixture. They charge a 6 volt sealed lead acid battery (it should have no problems with a 12AH right?). I was originally planning on having the chargers sit in the garage while the bike was out and plug it in when it came back but I guess I could wire them into the bike circuit.

Yea, they're trickle chargers and should be Ok left on all the time. The only drawback is the time to re-charge will probably be 24 hrs or so.

 

[Brian Oshman]

Just put them in a project box or something. They probably won't tolerate road vibration and you really can't plug them in on the road so just leave them at home and plug it in when necessary.