Author Topic: 24/48 volts in one system?  (Read 853 times)

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force9BOAT

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24/48 volts in one system?
« on: April 27, 2006, 07:13:26 PM »
I presume this idea is not workable but here it is.


I have a set of four 12V batteries wired for 24V (two sets of two in series and parallel).  My solar panels and charge controller are configured for 24V charging.  I also have a wind turbine whose stator is optimized for 48V.  What would happen if I connected the two pairs of batteries giving me four in series at 48V but left the solar charge controller connected to each pair for 24V charging?  Then the wind turbine could also charge the whole set at 48V.  


I'm thinking that since individual batteries in a series can be measured it may also be possible to charge/discharge individual batteries in a series.  Of course the 24V charging and discharging would be done in parallel (each set of two) to keep voltages equal.


Is this a bad idea?


Rob

« Last Edit: April 27, 2006, 07:13:26 PM by (unknown) »

Ungrounded Lightning Rod

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Re: 24/48 volts in one system?
« Reply #1 on: April 27, 2006, 04:05:32 PM »
You'll need two charge controllers for the two fractions of the panels.


Separately charging or loading voltage-wise fractions of a battery risks getting the upper and lower parts to different states of charge.  Then when your load exceeds your charging you can drain the lesser-charged section and drive it to reverse polarity (with major damage to it) because of current driven through it by the still-charged fraction.  On a per-cell basis this is what doing an equalizing charge is intended to prevent.  You'd be creating the situation deliberately.


There are three-terminal devices - essentially switching regulator/voltage converters - to pull power from the more charged part and drive it into the less charged part (with some loss).  You'd be way ahead to reconfigure the panels for 48 and get a new controller.


But you said your load was at 24.  That's not good.  (Your balancer would have to handle the whole charging current of the 48V stack - half the total power.)  Can you reconfigure the load for 48?

« Last Edit: April 27, 2006, 04:05:32 PM by Ungrounded Lightning Rod »

RP

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Re: 24/48 volts in one system?
« Reply #2 on: April 27, 2006, 06:48:14 PM »
Can you modify the coil connections in the stator to work at 24volts?  Can you obtain some transformers to lower the AC voltage of the stator to 24V before the rectifiers?
« Last Edit: April 27, 2006, 06:48:14 PM by RP »

commanda

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Re: 24/48 volts in one system?
« Reply #3 on: April 27, 2006, 07:15:14 PM »
I assume it's a 3 phase alternator. Can you connect it in delta rather than star. It'll get you pretty close to matching a 24 volt battery if it was previously in star for a 48 volt battery.


Amanda

« Last Edit: April 27, 2006, 07:15:14 PM by commanda »

force9BOAT

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Re: 24/48 volts in one system?
« Reply #4 on: April 28, 2006, 06:12:52 PM »
Thanks all for your replies.


This was just an idea I thought I'd put out for comment.  I plan to change the stator to Delta and stay at 24V.


I'd like to move to 48V in the future but that would mean purchasing a another solar panel and 48V inverter.  Don't have the budget for that just now.


Rob

« Last Edit: April 28, 2006, 06:12:52 PM by force9BOAT »