Electric Bikes - combining batteries - can it be done??

I read somewhere that batteries for ebike's could be combined????

not sure about this, i know batteries in car's (4wd) can be combined and still only output 12V..

can this be done for ebikes?? any complications??

for example a 48v system with two 48v 15ah batteries

yes you can combine them first you have to choose if you want series(96V15ah) or parallel (48V30ah)
You should use two of the same batteries and put a diode in the circuitry to prevent current from running "backwards".

What are you trying to accomplish?

trying to accomplish, nothing - just wondering if it could be done..... I knew it works with cars, just wondered if you could do it with these bikes...

Are you trying to get more voltage or my ah's

no to voltage, yes to ah (or battery doesn't run out as quick)

the idea was for future and location..

future - in case i need longer battery life (i don't want to throw the old one away - and i can get a smaller one now, that i think will accomplish my needs)

location - lets face it, the battery being high up is not the best location (on the rear rack) and saddle bags (so to speak) seem to be an option - how easy would it be to put your stand down and watch your bike topple over (presumably damaging your batteries)..

just a thought, does anyone know better stands to use - or do we lean it against a tree trunk :-)

hi sangesf - tried to private message you, but i need 50 posts first :-)

thanks for all your help - you are incredibly knowledgeable - do you sell these electric bikes??

What electric bikes?

No problem with this idea. In fact it is a good idea, as each battery hooked up in parallel can use a lower C rate to give the overall output, than it normally does, unless you need twice the normal output of amperage (don't usually). I run two Ping 48V 15Ahr batteries in parallel on my recumbent, for double the normal range, using a Schottkey diode battery combiner which used to be available at ebikes.ca (not anymore). I also got another equivalent battery joiner consisting of two potted "ideal" diodes, from forum member "Tiberius" on the Endless Sphere forms, shipped to Victoria British Columbia from England. It was about 60Cdn. It makes life easier on the batteries as the depth of discharge of each one is typically less than normal. The diodes are needed, as one battery can charge the other one, if they are out of whack voltage-wise. The ideal diodes are nicer than the Schottkey as they have only a very small voltage drop across the diodes.

thanks chvid - that fully answers that question

just one further question - when you charge 2 batteries on this system, do they have to be charged seperately - or one plug in will charge both of them??

You still need to charge both batteries separately, as the diode will block current going toward both the batteries. I don't think it is a good idea to parallel the packs without a diode, but I'm not an expert at charging. I take two chargers on my longer trips.

thanks