24V System Wiring Type/Size/Connectors Questions ...

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MB-1-E
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24V System Wiring Type/Size/Connectors Questions ...

Hi,

I'm getting closer to wiring up my 24V system.
For juice I'll have 8ea 12V-9Ah batteries.
These will power a 24V Scott 560W (3/4hp) motor.

I'm wondering what would be the best wire to use to series/ parallel my batteries?

Would I use the same size to go from the controller to the motor?

The batteries have 1/4" connections. What is the best way to make the interconnections, what type of connectors would last?

What about connecting my Watts Up meter, best connections for end to end connections?

Will soldered connections work, what about silver solder, pre-made sets?

Sorry, it's a lot of questions, I'm just trying to get a feel for what you are using to group smaller SLA's together.

Thanks for your time and answers.

Dave

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Re: 24V System Wiring Type/Size/Connectors Questions ...

`I'll let the experts answer this one.
Why are you using 8 12 volt 9 ah SLA batteries, that's a lot of weight almost 70 lbs, to ship and carry around?
You might want to also see pages 8 - 17 of the Crystalyte Home Assembly Guide for a suggestion on how to connect your batteries.
I'm about to purchase 4 B&B EB12-12 if I can get them locally and with a discount.

Peace Out,
Gman

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Re: 24V System Wiring Type/Size/Connectors Questions ...

Hi Gman,

"Why ... 8 12 volt 9 ah SLA batteries".
Actually they weigh in at 6 lb ea for a grand total of 48 lbs, (still a lot of weight though).

The short answer is range/ cost. 36Ah@24V
The longer answer is (or should be) detailed in my Electric Mountain Bike blog.
Frame size constraints, limited width for pedaling abilty and keeping as low a CG as possible is the reason for this particular size and quantity.

I'm shooting for an 11:1 reduction ratio for back road dirt, gravel mountainous terrain.
We'll see if it works out as planned, I will always have the ability to use half or even one fourth of these for shorter flat trips nearby. A reserve set would always be ready in that case.

Dave

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Dave B

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Re: 24V System Wiring Type/Size/Connectors Questions ...

`
:(
Sorry MB-1-E, I thought the post was from Liamo0o.
Did you recently change your Avatar?

Peace Out,
Gman

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Re: 24V System Wiring Type/Size/Connectors Questions ...

Hi again,

Yes, I saw this lightning "V" and thought it might be appropriate for the site. Sorry to throw you off, I may change again from time to time at least until I find something that sticks. Probably a pic of my completed MB-1-E (when I get 'er done).

Dave

MB-1-E
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Icon Photo of lighning striking Eiffel Tower Jun 3, 1902, taken by MG Loppe'

Dave B

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Gman
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Re: 24V System Wiring Type/Size/Connectors Questions ...

`K
You can also get a V is for voltage Avatar free with MB-1-E, Dave or what ever you prefer, contact Max at avatar [at] VISFORVOLTAGE-MODERATOR.NET.

Peace Out,
Gman

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mf70
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Re: 24V System Wiring Type/Size/Connectors Questions ...

When you say 1/4" terminals, do you mean 1/4" spade clips? If so, I'd recommend drilling a small hole in each spade and bolting to a ring terminal. Spring clips to spade lugs can develop resistance, which causes them to heat up, corrode, lose temper, and develop sill more resistance. Bad scene.

For wire size, you're putting about 24A through the wire. The site

http://www.powerstream.com/Wire_Size.htm

... has opinions about sizing.

For pack wiring, I'd recommend:

Pack - | | ------------- - - - - |1 |2 |3 |4 + + + + -------------- | (A) ------------- - - - - |5 |6 |7 |8 + + + + -------------- | | Pack +

(Ignore the tags, please)
You could then set up a series-parallel switch at "A" and use a single 12V charger for a fully balanced pack.

mark

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Re: 24V System Wiring Type/Size/Connectors Questions ...

Thank you for the reply Mark!
That setup looks good.
I'm not familiar with a series/ parallel switch, is there something specific made for this purpose or is it just a standard double pole, double throw type switch that re-routes the wiring?

Sorry, I'm lacking on the electrical/ electronics end of the spectrum.

What you describe is EXACTLY what I need in order to charge these with my existing 12V Iota 15A charger w/QD4. It's a three stage charger and works well with the two 6V-220Ah AGM's (in Series) that I have for household emergency backup and RV use.

Thanks,

Dave

MB-1-E
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Dave B

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Re: 24V System Wiring Type/Size/Connectors Questions ...

SeriesParallelSwitch.jpg

Hi Mf70,

Is this what you mean?
Will this work to supply 24V but charge at 12V?

Thanks,

Dave

MB-1-E
Electric - Bridgestone MB-1 Mountain Bike
Icon Photo of lighning striking Eiffel Tower Jun 3, 1902, taken by MG Loppe'

Dave B

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mf70
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Re: 24V System Wiring Type/Size/Connectors Questions ...

Yup.

Before I hooked the full thing up, I'd draw versions with both switch states to be sure of the routing.

You can also use a four-contact plug to do the same thing. The plug from the charger puts 12V to both banks, while a dummy plug re-routes the connections to get 24V output. The only catch is that the plug needs to carry full discharge voltage (of course, so does the relay).

-Batt Bank1 + - Batt Bank2 + Pack Neg ---| | | |-------Pack + ------------------------------------------- | | | | | |------ | -----------| | | | |-------------------| | | | - Charger + And an alternate "dummy" plug wired: ------------------------------------------- | | | | |-------|

Mark

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Re: 24V System Wiring Type/Size/Connectors Questions ...

I did some searching for a DPDT switch (or relay as you noted) that would handle high Amperage ... they don't come cheap, do they?

I like the two plug idea!
I get the feeling that it would be easier and less expensive to go this route. I'll go look for a four connection plug.

How much amperage do you think it needs to be rated for?

The motor is rated at 24V 30A.
I would assume that it could conceivably draw up to 100+A for short time periods.
My charger is rated at 15A.

I'm guessing 100+ Amp plug rating.

Thank You for your input, it's very helpful and appreciated!

Dave

MB-1-E
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Icon Photo of lighning striking Eiffel Tower Jun 3, 1902, taken by MG Loppe'

Dave B

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chas_stevenson
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Re: 24V System Wiring Type/Size/Connectors Questions ...

I would like to present the facts about switches.

1. The rating of a switch is the amount of current which can be safely control, turned on or off, by the switch. This is known as the contact rating. A switch in the closed position can carry much more current than the switch's contact rating.

2. A household switch is typically rated at 15 to 20 Amps @ 120 volts. You can purchase toggle switches, which are easier to mount, with the same ratings. Remember the switches rating is for the contacts NOT how much it can carry in the closed position.

My Trike has 2 battery packs, 36 volts each, and I use a DPDT 10-Amp switch from radio shack to select between them. I only switch when the throttle is off. I placed the switch in a location where you can only reach it with your throttle hand. My controller is rated @ 40 amps and I know I draw that much through the switch on a daily basis. It is over a year old and gives me 0 problems. MY Merida uses the same switch and switches the 36-volt battery pack with no problems. I know I draw at least 25 amps through the switch on this bike and it doesn't even phase it.

3. If you take 2 wires, with the ends stripped, and touch them together with power applied you may see a spark. In a switch when the contacts make or break connection the same kind of spark occurs. The larger the spark, for a give voltage, the more current flow. Once the wires are in contact with each other the current flows normally. The same thing happens in a switch.

4. When you connect you batteries there should not be a large spark because you do not have the throttle on and only the controller is being powered, which pulls very little current in the on state. If the throttle were at full power every time you connected you batteries, the battery connectors would not last long because they could NOT handle turning on and off that much current. The connector can carry much more current once it is connected. This is the same in a switch. Once the connection in the switch is made the current may increase many times the rating of the switch with no ill effects. The spark in the switch is what causes the damage. Yes, you can put enough current through a switch to damage it, but the same can be said for a piece of wire and it would be about the same current for each.

So any good quality toggle switch will do the job!!!!!!!

One other note - I don't think your motor will pull more than 35-Amps because the controller will keep the current flow in check.
35-Amps @ 24-volts is 840-watts. My Merida hits 25-Amps @ 36-volts or 900-watts.

Switch on,
Chas S.
My Bicycle Pages

MB-1-E
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Re: 24V System Wiring Type/Size/Connectors Questions ...

Very helpful information Chas!

I'm releaved to know that I don't need to go buy some $250, 13#, heavy duty relay, Whew!

I'll just get a nice toggle and, of course, won't switch it under load.

Good news indeed!
Thanks for your explanation, I'll incorporate the controller disconnect that we discussed in the other thread.

Thanks to all for your help on this, it's appreciated!

Dave

MB-1-E
Electric - Bridgestone MB-1 Mountain Bike
Icon Photo of lighning striking Eiffel Tower Jun 3, 1902, taken by MG Loppe'

Dave B

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<a href="http://visforvoltage.org/book-page/996-mountain-bike-conversion-24v-3-4h... - Bridgestone MB-1 Mountain Bike</a>

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