Hi Bruce and All, It doesn't actually double the power, just the voltage as the amps are cut by 50% so the same total watts. The extra diodes eat another volt but that is made up by 2x's the voltage. A bigger heat sink, a piece of alum angle, etc works fine, for the bridge diodes is a good idea with heatsink compound between them. I've been doing a bunch of scooter chairs and switch 12vdc chargers just like you say to 24vdc nom. Most al the ferro- resonant ones, the kind with no circuit board and a big can capacitor keep their regulation when doubling voltage which is nice. Some RV Ac-DC 'converters use transformers with 2-4 output windings you can put in series to raise output voltage plus the diode switch trick. Though each time you go up in voltage, the amps go down. The circuit board ones mostly can be too removing the board and bypassing it but they will be higher voltage somewhat output causing them to charge harder, faster which is great if you have a fan on it, always a good idea on any charger, controller and make sure it shuts down by timer or voltage limit relay, etc so not to overcharge and remember fuses or circuit breakers are not an option. Be careful of Chinese, etc low quality imported chargers have these as many extension, other power cords . So make sure yours are high temp by testing with a lighter. If melts and burns fast, get another cord. Jerry Dycus.
________________________________ From: Bruce EVangel Parmenter <[email protected]> To: [email protected] Sent: Sunday, August 4, 2013 2:46 AM Subject: Re: [EVDL] Low cost EV parts, Re: Looking for some parts On Sat, Aug 3, 2013, at 08:03 PM, jerry freedomev wrote: ... > For low cost chargers older Golf > cart ones without circuit boards can be switched to 72vdc nom just by going > to a full wave bridge rectifier instead of the full wave. > ... - I have done this before. I took a 12V automotive charger (an old fashion, transformer-type with a center tapped secondary using two diodes for full wave rectification), and changed it to a 24V full wave bridge rectified output (I was charging two 12V group 24 deep-cycle wet-cell batteries on an e-minibike). I changed how much power I was demanding from the transformer, so it got hot. I threw a couple cheap 120VAC box fans on it to cool it, and it worked out. Jerry's idea is effectively doubling the power demanded from the original design. You would need to see if you are also overheating the transformer. And if so, you could stick a fan on it to keep it cool. But the problem with a old fashion transformer type (dumb) charger is that it is fast charging at the beginning, but tapers to a crawl toward the end of the charge. You end up paying a 'charging time' cost for going cheap. {brucedp.150m.com} -- http://www.fastmail.fm/- Accessible with your email software or over the web _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130804/860265d8/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
