Connecting batteries in parallel

NRG

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Oct 6, 2009
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Fordulike

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Feb 26, 2010
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If they are of the same chemistry(voltage) and in the same condition/health then you should be OK. If they differ in chemistry and or condition then you can still do it but will need to use something like the 'Ideal Diode':

See this post: http://www.pedelecs.co.uk/forum/electric-bicycles/4807-ping-batteries-ezee-possible-alternative-2.html#post61084
So two brand new bottle batteries above should be ok?

If they both fit inside the frame, then I reckon this would be a good solution for balancing the bike.
 

NRG

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Dont see why not, as long as they don't go 'out-of-kilter' then is should be OK but you'll need to keep an eye on them as they age.
 

Fordulike

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After reading more about this on other forums, it appears to be quite a grey area.

There seems to be a lot of factors that can affect performance and safety of a set-up like this.

Probably not worth taking the risk. Just a shame they don't make the bottle type batteries in larger capacities :(
 

NRG

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Oct 6, 2009
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If you are worried about any risk then fit some of the ideal diodes...job done.
 

Mussels

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Jun 17, 2008
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After reading more about this on other forums, it appears to be quite a grey area.

There seems to be a lot of factors that can affect performance and safety of a set-up like this.

Probably not worth taking the risk. Just a shame they don't make the bottle type batteries in larger capacities :(
That's the problem when vanity matters more than practicality. ;)
 

Scottyf

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Feb 2, 2011
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It can definetly be done. Look at other ebikes on the market that have additional 8ah batteries added to the 10ah batteries. As long as they have the same voltage it will work.

However becasue most ebike batteries come with a BMS attached it limits the flexibility to just wire in additional capacity. Ie if you forget to chage one battery and the other is fully charged. The fully charged battery will try to equalise the other. Therefore causing damage while one supplies the other.

As stated above best to use a diode inline to stop this from happening.
 

wurly

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Aug 2, 2008
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Yeovil, Somerset
Ideal diodes are best, but another alternative if you don't mind losing a bit of power through heat is these 'low forward voltage' schottky diodes.
30a schottky barrier rectifiers : Maplin Electronics
I connect two ping batteries in parallel using these mounted on a heatsink, i have also made provision to connect up to four if necessary. No problems so far considering each battery has it's own BMS.
 
D

Deleted member 4366

Guest
Just to be boring and come back to the topic: Steve (Saneagle) has done it on his bike. One battery has cylindrical cells and the other has pouch cells and probably different chemistry too. he did it about 6 months ago by simply joining the two power leads in parallel. He was going to join the two two charging leads as well, but the first time he charged one, it took twice as long, and he found that the other battery was also charged. It's run without problems since with no blocking diodes.

I keep thinking about whether this is potentially harmful to the batteries, and I can't make up my mind. All I can say is that it works in this case. To be absolutely sure, you can fit blocking diodes like the others suggest.
 

Scottyf

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Feb 2, 2011
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I don't think it would be a problem as the packs would try to equalise.
Same when add or removing lipo bricks. As long as the voltages are similar it will be ok. It's when you start changing the voltages that it then starts to short out.

The Bms would naturally keep all the cells in each pack balanced.