barrie w Posted October 5, 2009 Share Posted October 5, 2009 Good evening, I have read, in MMM & other mags, technical advice from Clive M.concerning additional batteries. His comments have been to the effect that 2 x 6volt batteries would be better than 2x 12 volt. As I'm thinking of adding more power into my Hymer I wondered if he would care to enlarge on that further for me. Thankyou . Link to comment Share on other sites More sharing options...
Guest peter Posted October 5, 2009 Share Posted October 5, 2009 I think you will find that is 2 6volt is better than one 12volt because of the higher capacity. Link to comment Share on other sites More sharing options...
Clive Posted October 5, 2009 Share Posted October 5, 2009 When you have batteries connected in parallel there are a couple of considerations. 1 A duff cell in one battery will pull down the other battery. 2 you can never be sure that the charging and discharging current is perfectly shared. When batteries are connected in series neither of these problems exist. Does that help? C. Link to comment Share on other sites More sharing options...
lennyhb Posted October 6, 2009 Share Posted October 6, 2009 Surely if using 2 x 6 volt batteries in series if you have a duff cell in one battery you have lost all 12 v power. Link to comment Share on other sites More sharing options...
Clive Posted October 6, 2009 Share Posted October 6, 2009 If you have a short circuit cell when 2 X 6 volt batteries are connected in series you end up with a 10 volt battery! If you have a short circuit cell when two 12 volt batteries are connected in parallel you have a high local current flowing when the 10 volt battery draws lots of amps from the 12 volt battery. This is one reason why its advisable to fit one fuse for each battery. Short circuit cells are normally caused by lead paste build up at the bottom of the cell boxes - or buckled plates caused by rapid charging. (Beware of your big sterling B2B if your batteries are smallish!) Open circuit cells would result in the "zero volt" situation if you have two 6 volt batteries connected in series. If you have two 12 volt batteries connetcted in parallel and one cell goes open circuit then you are unlikely to know you only have half capacity until you try and use it!. Open circuit failures are normally caused by external mechanical forces - like using Stilsons to do up the battery clamps! Does that help? C. Link to comment Share on other sites More sharing options...
lennyhb Posted October 6, 2009 Share Posted October 6, 2009 I agree if a cell goes short circuit but the last couple of batteries I had fail in vehicles have had cells go high resistance effectively open circuit. Link to comment Share on other sites More sharing options...
AliB Posted October 6, 2009 Share Posted October 6, 2009 Are high capacity 6 volt batteries available at a reasonable price? If so where can they be purchased? Link to comment Share on other sites More sharing options...
Clive Posted October 6, 2009 Share Posted October 6, 2009 Search under "golf buggy batteries" and you should find loads. C. Link to comment Share on other sites More sharing options...
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