Battery question- series or parallel or whatever

[df909]

He goes- I have an electric cart on the farm. It has six 6 volt batteries that are connected together to add up to 36 volts. I have a 12 volt winch that I want to connect to the batteries. Someone told me that I can hook the winch up to the first or last two batteries in the group and it will give me the 12 volts for the winch.

This doesn't make sense to me since in my mind, the whole system is 36 volts since all the batteries are connected together. So, can I hook up the 12 volt winch to the first or last batteries? And if so, how do I tell which ones are the first two? Thanks!

 

[Bondo]

Re: Battery question- series or parallel or whatever

So, can I hook up the 12 volt winch to the first or last batteries? And if so, how do I tell which ones are the first two? Thanks!

Ayuh,... It can work that way,...

If ya start at the battery bank's (+) side, the 2nd battery's (-) would be where you'd attach the (-) of the winch...

If ya start at the battery bank's (-) side, the 2nd battery's (+) would be where ya attach the winch's (+)...

 

[Don S]

Re: Battery question- series or parallel or whatever

You can hook up for 12 volts anywhere in the 36 volt battery system, as long as you have two batteries hooked + to - (in series) to make 12 volts. The diagram below shows what I mean.

 

[df909]

Re: Battery question- series or parallel or whatever

Awesome- thanks very much guys. It so doesn't make sense to me, but electricity is like magic.

 

[Don S]

Re: Battery question- series or parallel or whatever

That drawing might be a bit confusing, try this one and see if it makes more sense.

 

[KD4UPL]

Re: Battery question- series or parallel or whatever

As long as you hook across any 2 batteries in series you will get 12v. However, using your winch will draw those 2 batteries down farther than the others. This means when you recharge the vehicle those 2 will need more charging. However, they will probably not get it because all the batteries are hooked in series and will get the same amount of charge current. This will cause the 2 batteries power your winch to be chronically undercharged. This will shorten their life.
I would recommend that if you use the winch a lot you get a separate 12v battery just for it.

 

[df909]

Re: Battery question- series or parallel or whatever

Hmm...that's a good idea KD4UPL. I'll be using the winch everyday to help with farm chores and I wondered about the charging. I do have an extra marine 12v battery in the garage- I'll just that one to keep the other, more expensive ones healthy.

Thanks again everyone.

 

[Don S]

Re: Battery question- series or parallel or whatever

However, using your winch will draw those 2 batteries down farther than the others.

Not really, the winch will not just draw down those 2 batteries. The voltage will be 12 Volts to the winch, but the batteries are all hooked in series and will all draw down equally. Even if only hooked to 2 batteries.

 

[sam60]

Re: Battery question- series or parallel or whatever

I'd sure like know what Don S. uses to make those nice drawings.

 

[Don S]

Re: Battery question- series or parallel or whatever

Photoshop.

 

[Splat]

Re: Battery question- series or parallel or whatever

Hey while I'm thinking of it, I've always wondered would you be able to simultaneously wire the batteries in parallel and series at the same time to eliminate the chronic discharge problem? In theory I can't see why it wouldn't work, but something in my gut says you can't have both ways at the same time.

73's Bill

 

[bruceb58]

Re: Battery question- series or parallel or whatever

Not really, the winch will not just draw down those 2 batteries. The voltage will be 12 Volts to the winch, but the batteries are all hooked in series and will all draw down equally. Even if only hooked to 2 batteries.

Actually, this isn't true. There will be no current flowing from any of the other batteries. Would be true if they were hooked in parallel but they aren't.

 

[smokeonthewater]

Re: Battery question- series or parallel or whatever

I think I would just get some 36 volt relays, run the winch on 36v and let it ZING!

 

[Fishing Dude too]

Re: Battery question- series or parallel or whatever

One thing to make sure you do is change which two batteries you hook you winch up to, over time will kill these two batteries quicker. Would say change about every 3 months, a new set of batteries will run about $500 for cheeper ones so would make sure to do what you can to make your batteries last for longest time you can.

 

[smokeonthewater]

Re: Battery question- series or parallel or whatever

I think I would just get some 36 volt relays, run the winch on 36v and let it ZING!

OR you could build a resistor block to drop down to a safer voltage under load.

EDIT: Better yet we could get really fancy and set up relays to transfer power to the winch instead of the drive motor on the cart and use the foot pedal to "throttle" the winch thus eliminating the solenoids that normally control the winch. You would have a switch labeled drive/winch and the in/out function of the winch would be controlled by the forward reverse selector.

Electricity is almost fun

 

[Don S]

Re: Battery question- series or parallel or whatever

Actually, this isn't true. There will be no current flowing from any of the other batteries. Would be true if they were hooked in parallel but they aren't.

Maybe I used the wrong terms to explain it. The VOLTAGE will equalize between all the batteries. You aren't going to have the 2 batteries used for the winch showing 5 volts each while the other 4 batteries show 6 volts each when they are all hooked in series.

 

[bruceb58]

Re: Battery question- series or parallel or whatever

Maybe I used the wrong terms to explain it. The VOLTAGE will equalize between all the batteries. You aren't going to have the 2 batteries used for the winch showing 5 volts each while the other 4 batteries show 6 volts each when they are all hooked in series.

It is very possible for individual batteries(or cells for that matter)to have a lower voltage than others. This is one of the big problems with electric vehicles and why there are monitors on every cell so that no more load is drawn from the series of batteries once one battery goes undervoltage.

Basically, lets say you discharge one battery in the group to half its capacity. When you subsequently ask for 1A from the series of batteries, each battery is going to deliver 1A including the one you discharged by half. The others aren't going to make up for the discharged one.

 

[Don S]

Re: Battery question- series or parallel or whatever

Bruce, the OP asked if it could be done, not if every cell in every battery is the same, nor did he ask for a thesis on batteries.
Assuming all batteries are equal condition, then it will work, and battery voltage will basically equalize in all 6 batteries in his system because they are hooked in series. How do you think an ACR (automatic charge relays) works. All they do is connect two batteries together to equalize the voltage.

 

[bruceb58]

Re: Battery question- series or parallel or whatever

How do you think an ACR (automatic charge relays) works. All they do is connect two batteries together to equalize the voltage.

Yes, they hook them in parallel.

There is no problem doing what the OP wants to do. All that info is accurate. They just won't equilize. He will also want to charge those 2 batteries seperate from the others in the bank to prevent damage to the other batteries depending on how discharged these 2 get.

 

[Fishing Dude too]

Re: Battery question- series or parallel or whatever

http://www.buggiesgonewild.com/

Here ask these guys about the problems that this can cause and if it can be done.