Author Topic: Is it ok to link 2 12v chargers in series to charge 24v bank?  (Read 9213 times)

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acapulco

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Is it ok to link 2 12v chargers in series to charge 24v bank?
« on: August 08, 2008, 06:39:47 AM »
hey there,


 I have recently changed over from 12volt system to 24volt.


 I have a charger that can run 12 or 24 volt as well as a better(more amps) charger that only runs at 12volt.


  Q:


    Is it feasible(safe) to hook both 12 volt chargers in series to charge a 24volt

    bank?  

    One is 20amp@12v/10amp@24v  other is 30amp@12v.


    currently when I do need to top up my battery bank withg genset and charger I

    am reconfigureing the bank to 12 volt so I can use the better charger.


    I generally charge with genset/charger once or twice a week depending on use.

    (i know i need more panels)


  tia,

  Ian.A

« Last Edit: August 08, 2008, 06:39:47 AM by (unknown) »

Flux

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Re: Is it ok to link 2 12v chargers in series to c
« Reply #1 on: August 08, 2008, 04:06:24 AM »
Not likely to work with 2 chargers in series across the 24v. It may or may not damage them but it will not give satisfactory results.


You could connect each 12v charger to one half of the battery string (12v). That would be ok as far as the chargers are concerned but you may have to keep swapping them around to keep the 12v strings in step.


Flux

« Last Edit: August 08, 2008, 04:06:24 AM by Flux »

electronbaby

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Re: Is it ok to link 2 12v chargers in series to c
« Reply #2 on: August 08, 2008, 05:32:44 PM »
Are you sure about the "Amps".


A charge controller that charges at 20A @ 12v is the same as a charge controller that charges 10A @ 24v.


I agree with Flux, usually connecting two chargers in series does not work as you usually have to isolate the grounds for them to work properly. This is the case with most PWM  and especially MPPT controllers (switch mode).


It might work if you have a very antiquated device, in which case its probably inefficient anyway.

« Last Edit: August 08, 2008, 05:32:44 PM by electronbaby »
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acapulco

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Re: Is it ok to link 2 12v chargers in series to c
« Reply #3 on: August 08, 2008, 07:42:04 PM »
Ok,


just a thought. sounds like it's probably best to continue as I am:


configure the battery bank to 12volt and charge at 12volt using the more powerful charger and run the other charger on my second smaller bank at 24v.


I only need to run genset/chargers once a week usually, which is also a good time to run other power hungry things like washing machine etc.


it's just a little annoying having to re configure the bank back and forth from 24 to 12v. I was only really considering the idea for convenience so that the system could be operated easily by Mrs. if I'm away.


cheers,


Ian A.

« Last Edit: August 08, 2008, 07:42:04 PM by acapulco »

boB

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Re: Is it ok to link 2 12v chargers in series to c
« Reply #4 on: August 09, 2008, 01:58:25 AM »


It would probably be simpler just to get a charger that will work with a 24V battery.

You'd still need more PV modules anyway, right ?


That being said, two MX60s have been used with two 60 V batteries in series for

one 120 VDC battery bank.  Eeach MX had its own 72 Volt array.  There are several systems that have been done this way.


If you do split up two chargers, be careful about tying grounds and commons together etc.


boB

« Last Edit: August 09, 2008, 01:58:25 AM by boB »

FuddyDuddy

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Re: Is it ok to link 2 12v chargers in series to c
« Reply #5 on: August 11, 2008, 11:05:18 PM »
Depending on how much current draw you have from the batteries, you could use a two pole double throw switch, wired like this (if I can draw it)


        12v                      12v

(+) -+-]']']'------+  +---------]']']'--+-- (-)

     |             |  |                 |

     |      +--+  +  +--+              |

     |      |            |              |

     +----- | -+  +  +--+              |

            |                           |

            +---------------------------+


Hope that is fairly clear ??

I did look on eBay, and there are several manual transfer switches, but one in the range of 200Amp runs around 350USD. With time you might get a 100 Amp switch for around 100USD. Also might use a pair of two pole disconnect switches.


Just a thought.

« Last Edit: August 11, 2008, 11:05:18 PM by FuddyDuddy »

acapulco

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Re: Is it ok to link 2 12v chargers in series to c
« Reply #6 on: August 14, 2008, 01:29:57 AM »
thanks for input,


prolly a bit beyond my knowledge/ability atm. maybe best 4 me to sell both chargers 2ndhand and put that toward a better 24v charger with multi stage etc(current chargers have no equalization mode or even different voltage settings only 1 voltage and whatever battery will take in amps. one has low.medium. high but voltage is same only amperage changes....


!

« Last Edit: August 14, 2008, 01:29:57 AM by acapulco »