How to add a 2ND BATTERY to your electric bike (Safely)

Most electric bikes come with a single 
battery like THE BLACKBIRD here. Now some bikes like THE LANCER have 
a single battery inside the frame. But then they have an option for a second battery 
on the outside now what if you already have an   ebike it's not designed for two batteries but you 
want to put two on well that's what this is for. A lot of you have been waiting for this dual 
battery parallel connector to get back in stock. Not only are they in stock but 
it is a new upgraded version! The internals are completely different 
and the outside has a new aluminum   case to shed heat, so this is 
going to perform much better.

The typical questions ….. How do these work? Can I use batteries of different voltage? Can I use batteries of different amp hours? I'm going to explain all of those 
things and show you how to connect one. This is a battery off of one of THE 
BLACKBIRD bikes and this is the cradle. This is the portion that's mounted to the frame. A lot of ebikes are going 
to have something like this. If your bike doesn't have this, what it probably 
will have somewhere, is a red and black wire. What sort of connectors at the end of 
this can vary a lot now I wanted this   connector to be as generic as possible 
XT90 meaning these are good for 90 amp. These are common on aftermarket batteries which 
is I assume what you're going to be using.

Normally you'd have the battery connector 
go straight to your motor controller   and there's nothing in between those two 
connections that's where this guy comes in. Let's grab two batteries and plug them 
in they each have their own connector   parallel module plug one battery in plug 
the second battery in and now the remaining   connection goes to your motor controller it 
really can be as easy as that if you have   XT90 connectors on your two batteries and on your 
controller so on something like the blackbird I   would take the battery and mount it on the rear 
rack now on something like THE LANCER if you've   got room in the triangle obviously that's another 
option and then we're just going to run this nice   long cable down to the parallel connector our 
second battery and the motor controller but if   you look closely at this production blackbird 
you'll see that uh-oh it doesn't use an XT90   it's actually using a slightly smaller XT60 
now that's sufficient for the bike because that   connector is rated for 60 amps and the bike can't 
draw that much power but that means that this guy   doesn't quite match up it's not plug and play or 
is it we also have this XT90 to XT60 adapter set.

pexels photo 8071753

It's one two three adapters that come in the set Let's say for example your blackbird battery 
has an XT60 connector well we can plug one of   these in and now that will plug directly into 
the stock blackbird battery but we bought an   aftermarket battery which uses an XT90 connector 
well no problem we can plug that one in right here   and looking at our controller oh well it also has 
an XT60 well that's not a problem we have this   adapter here and we can use an XT60 going to the 
controller so with these three separate connectors   you can use any combination of XT90 or XT60 now 
I fully understand that your bike may not have   either of those in aftermarket batteries like I 
said it's very very common but on stock batteries   you could get bullet connectors you could get 
Anderson connectors you could get some sort of a   generic plug that we don't even know what to call 
it and in those cases you will have to find some   sort of adapter or make your own now let's cover 
some of the technical specs for THE BLACKBIRD   example I have here I've got a 52 volt battery 
that is a 16 amp hour the second battery i have   sitting up here is a 52 volt 17.5 amp hour so 
the capacity of this one is a little bit bigger   than this one and that's okay you can mix two 
different batteries of different capacities   I could for example take the stock battery off 
move it to the cradle and i could mount a massive   you know 20 amp hour triangle battery in the 
middle and that's going to work perfectly   fine the voltage however does matter you cannot 
use say a stock 52 volt and a 48 volt the battery   voltage between the two batteries must be the 
same this is more than just a parallel circuit   so if you hooked two 48 volt 10 amp hour batteries 
in parallel you'd effectively have a 48 volt   20 amp hour battery you double your 
capacity the voltage would remain the same   that's not exactly how this little guy works now 
the end result is the same thing but it's a little   bit smarter than that with a standard parallel 
connector if one battery is charged up to 54 volts   and the other one had say a 50 percent charge and 
was it say 48 volts 47 volts if you connected the   two together there is a potential difference 
in voltage there that is going to equalize   it's going to happen very quickly and somewhat 
dangerously you're going to instantly drop the   voltage of one battery and raise the other until 
they are equal so it's an instant rush of current   from one battery to the other effectively 
discharging one and charging the other   at a higher rate than either of them can handle 
and potentially kill the BMS or the cells in both   batteries obviously we don't want that so this 
being a little bit smarter is also a little bit   safer you see if we have two batteries 
that are not charged evenly this will   draw from the battery with the higher voltage 
until the batteries equalize at which point it   can draw from both of them together and that's 
something that might look a little odd on your   display of your ebike if you have one battery 
that is halfway charged and one that's full   your motor controller that's plugged in is only 
going to see the battery that is fully charged   and operating you can always plug them in one at a 
time to ensure what your actual charge levels are   you can also run off of one or the other battery 
you don't have to have both of them plugged in   at all times this is good for anything from 24 
volts up to 52 volts and you also probably want to   know how much current this can handle the maximum 
recommended current for this is 30 amps so just   something to be aware of it does have a very nice 
aluminum case that should shed the heat but it is   only rated for 30 amps so if you have one of those 
35 amp controllers and you're going to use one of   these you may want to tune it down just slightly 
so it maxes out at 30 amps now that's going to   cover most stock electric bikes on the market 
usually 20 or 25 amps is as high as a stock   electric bike will go even the 1000 watt BBSHD 
equipped bikes those controllers are either 28   or 30 amps so can handle that without any changes 
these are in stock at BOLTON EBIKES DOT COM The adapter set to the XT60s are also in stock   one thing I don't have quite yet is a 
specific mount designed for it to put it on   the bike and it's pretty small and 
compact it can go in a lot of places.

But if you'd like to see a custom designed 
mount for these let me know in the comments   i'm thinking about actually making 
one and putting it into production. Just let me know if you're 
looking for a case or a mount   to put this on your bike and we'll 
try and get to work on that right away If you're considering putting two batteries 
on your ebike you should probably know how   to maintain them for nice long life i 
have a great video on that right here..

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