My first harness

[cwah]

I just did my first harness to put my 4 lipo 18.5V8AH in series:

Here with the wattmeter:

I'm doing it for the first time, and before I blow anything I just want to check with you expert!!! :lol:

- My batteries have probably different voltage and are not balanced. Can I insert now the harness without balancing?
- Can I use the wattmeter the way it's shown on the picture? Would that blow?

If everything is all right, I'm going to plug it

 

[chroot]

Whats the plan setup for your ebike. If I am in your shoe, First of thing I want put in parallel for the more Ah and I would recommend minimum 15Ah or higher first before series. The reason one of the LiPo goes dead (during the series between 4 packs) and it will lead fireworks.

So more packs together in parallel and one of weak cell would cover by other cell to keep up without damage LiPo. I mean for your safety sake. 10Ah is fine as long as you don't push them harder as limit ampere without make them bad puff (over-discharge).

Oh you might want the LVC boards from Methods or Geoff. It WOULD prevent your LiPo dip into dead zone = fireworks.

 

[cwah]

The plan setup is the following:
- 90% of the time I travel less than 10 miles. I don't need high capacity. So 74V8AH is enough. It's my standard "fun" setting
- From time to time I'd need to travel for longer distance at 20-30 miles. I'd then plug the batteries in parallel to have 37V16AH. Because I use 16" wheel, I'd have a max speed at around 15mph and would be able to achieve this distance.

15AH is huuuge for me. I have for now around 4.5kg batteries. At 15AH I'd end up with 10kg and it's way too heavy.

My batteries are rated 30C, so for 8AH batteries I can push up to 30*8=240amps. But I don't think I'll push more than 30-50 amps, which is around 4-6C with my 12 AWG cables.


ps: I've considered the LVC board from methek but it's way too expensive with 4 pack in series (200$). I prefer to use lipo alarm for now :lol:

 

[999zip999]

Yes all batteries need to be of same voltage before you plug them together.

 

[dogman dan]

You plug that in yet? Looks to me like at least the pack on the right will have black to red connected on the same pack.

Am I seeing this right?

Same voltage to paralell, series don't care.

When we say same voltage, we mean pretty close. For example, 20v can plug into 20.5v no problem.

 

[dogman dan]

Seriously, DONT PLUG THAT IN. IT LOOKS LIKE A SHORT TO ME.

 

[bjosta]

Yupp, the top right connector definitely shorts the battery to the right in the first photo.

 

[bjosta]

I don't know that multimeter but you have nothing connected to the COM port, that seems odd...

 

[cwah]

Can't spot the short. I don't see where my cables are connected to the same pack? Is it the latest on the right on the first picture?

Bjosta, what should I put on the COM port?

 

[mark5]

Can't spot the short. I don't see where my cables are connected to the same pack? Is it the latest on the right on the first picture?
...

On the battery side of the harness, if the wires are numbered
1234
5678

it looks like you'll short 3 and 4 when you plug the other side of your harness in.

Edit: on second thought it could just be the angle the picture was taken. Just make sure 3 and 4 don't go to the same rightmost battery.

 

[amigafan2003]

I think it's the photo causing confusion CWAH but I agree with you, I can't see a short there.

If you look 2nd photo and at the pack in the top of the photo, it looks like the black wire goes into the harness immediately below it's partner red wire, when in fact it goes besides (poor light). The first photo shows the route of the black wire a bit better - it "tucks" under the red wire. Looks ok to me.

 

[bjosta]

Can't spot the short. I don't see where my cables are connected to the same pack? Is it the latest on the right on the first picture?

Bjosta, what should I put on the COM port?

Hmm yeah, it might be the photo, at first it did look like mark5 said.
Usually you plug the black probe to COM and then move the red depending on if you are going to measure volts or amps. But like I said, I don't know your MM, if it's measuring voltage now it obviously works

 

[cwah]

I prefer not to have any explosion in my house, I took more pictures :lol:

Is it all right?

 

[cwah]

Can't spot the short. I don't see where my cables are connected to the same pack? Is it the latest on the right on the first picture?

Bjosta, what should I put on the COM port?

Hmm yeah, it might be the photo, at first it did look like mark5 said.
Usually you plug the black probe to COM and then move the red depending on if you are going to measure volts or amps. But like I said, I don't know your MM, if it's measuring voltage now it obviously works

Ok, black on COM then. Should I plug the red on T+ or T- to measure voltage?

 

[bjosta]

Wiring looks correct. You put the black one on COM and red on T+ (also says V)

*edit*
And if you have a CA you don't need to mess with different wiring harness for parallel/series connection for added rage, just set you max amps and max speed with the CA, simple and effective

 

[cwah]

Thanks for the wattmeter advice

I'll have a CA shortly, but I think it's better to have the correct voltage in order to maximize motor efficiency!!

 

[chroot]

Okay, I understand about Methods LVC is expensive (agreed) but dont push 8Ah harder or you will get them dipping death zone easily due voltage sag would be very awful bad. :lol:

Anyways, It looks fine 4 packs in series 8Ah and The lipo buzzers can work as long as you keep the voltage sag at 3.65v minimum.

 

[cwah]

But with 30C lipo shouldn't I be able to use them at 10-15C without problem? I mean 10C is 80amps which is already more than enough :lol:

By the way, what is voltage sag? how to keep it at 3.65V?

 

[chroot]

Voltage Sags are momentary (typically a few milliseconds to a few seconds duration) under-voltage conditions and can be caused by a large load starting up (such as a hub motor).

http://en.wikipedia.org/wiki/Voltage_drop

Do you have Cyclist Analyst? I am not sure if your LiPo is a 6S anyways if it is... 6S's LVC is 21.6v per pack so you series 4 pack together at 100v and the LVC at 3.65 x 24 = 87.6v.

By the way, what is voltage sag? how to keep it at 3.65V?

 

[cwah]

Thanks for the explaination.

I have 5s batteries, so I should not go under 73V with 20s. Thanks

 

[chroot]

No problem, You got it and set lvc buzzers at 3.65v. This will give you time to react and prevent dipping into dead-zone.

 

[cwah]

will do. Ordered lipo buzzer from ebay since 4 week and haven't received them yet. Waiting for them to arrive

 

[icecube57]

Good job! I thought about doing plugs that way with glue for a hot second but since I use much larger wire the plugs tend to have great suction when pulling apart and also the super glue bond will break after a few cycles. Short term its awesome... long term a plug rebuild is in your future. Maybe try hot glue since it will be easily repairable.....

If you are trying to make this permenant try pp75 expensive but modular design is what they were designed to do... i would have even consider xt150s because they slide lock together but its a thin piece of plastic holding them together. I suppose you could use some clear setting epoxy to reinforce for a stronger bond. http://selleys.com.au/adhesives/household-adhesive/araldite/ulra-clear Its a thought.

Im personally going to revisit this as a more robust solution for my 1 plug pp45 anderson harnesses.

 

[cwah]

Thanks Icecube. The suction is indeed very strong. Not sure if it will last. :lol:

Going to add some epoxy to reinforce and maybe get some powerpole 75 in the future as you suggested.

 

[dogman dan]

Sorry if that caused you to freak out. I just was sure I was seeing red to black getting connected on the far right pack.