automobile battery series-parallel question

[geesq]

I'm new to this forum, so apologies if question is in wrong arena or format.

I am designing a 6 volt dc battery system that would deliver current to a 6 volt system, and would like to tap it for occasional or light service for 12v dc. I would like to use 2 parallel-connected 6v batteries for their current capacity during normal 6 volt use, and use diode protected connections (or some such device) to attach a series circuit that provides 12 volts from the same two 6v batteries for light or limited use.
Charging would be 6 volts to the batteries during use. I'm not a sparky, so would appreciate advice as to feasability of this, and if commercial units are available.

Thanks for all advice,
geesqd

 

[GregLocock]

Simultaneously?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[rmw]

12/24 V systems were very common to the trucking industry ~30 years ago. They used 24 V for starting and 12 V for normal running/charging. Do some googling and see if you can find anything there that would give you any ideas. Those systems still provided 12 volts to the normal electrical system while the starting circuit was engaged. What you want to do is the inverse of that, though.

rmw

 

[evelrod]

I realize your new so I'll be gentle.....

Try a Google search. It takes time, true. All that you need is there cause I've BTDT.
A few years ago I installed a 12v battery (actually TWO 6v in the same case) that had a solenoid to put both sides of the batt together to shoot 12v to the starter yet still maintain the stock 1937 Buick charging system and all the 6v lights and ancillaries. Was not cheap, but it did the job for many years. I sold that car so I no longer have any documents....Sorry, it's your turn,

Rod

 

[waross]

Connect one battery permanently to the 6 volt load and to the charging circuit. Locate a 6 volt double pole double throw relay of suitable ratings and current capacity. Use the normally closed contacts to connect the batteries in series. When the relay is energized, one normally open contact may be used to connect the batteries in series for 12 volts and the other normally open contacts may be used to connect the 12 volt load.
Beware of flash-over between the relay contacts during switching if the ratings are not adequate.
This is more or less what the series parallel switch on the 12/24 volt truck engines did. It was optimized for starting current on one contact and charging on the other contact.
I would normally echo the Google comments, but I have found older technology is not always well represented on the WWW.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[GregLocock]

Easiest way to do it simultaneously is to leave the two 6V in parallel and build a 6->12 upconverter for the 12V, if it is a fairly low power requirement. That's more expensive than a relay, it depends on what you are trying to do.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[JayMaechtlen]

It used to be semi-common to have 6>12 converters for car stereos for older cars. I still have one I used in my 6v VW Beetle. (why the @@&# did I bring that converter home from Germany?)

DC-DC converters are pretty common in electronics nowadays, don't know if you can find one in convenient size/ratings.

But, that would allow a single 6v battery, much simpler and lighter. Actually, savings of only one battery might pay for the DC converter.

regards
Jay


Jay Maechtlen

http://www.laserpubs.com/techcomm