Do I need diodes with this layout?

Batteries, Chargers, and Battery Management Systems.
MJSfoto1956   10 W

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Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 18 2018 6:37pm

So I'm getting closer to to finalizing the details of the upgrade of my 72V/2000W Chinese eMoped/eScooter.

The ultimate goal is to replace the 2000W QS 205 motor @ 72V with an 8000W QS 273 motor @ 84V. However, my first step will be to upgrade the controller, followed by the battery system, and lastly the motor. Currently I'm looking at building a 24s16p Li-ion pack made from 48 NESE 8p modules controlled by a 24s BMS. This gives me an 86.4V 54.4Ah system with a max charge of 98.6V.

While I don't "think" this particular electrical layout needs any diodes or resistors, I am putting it out there for the experts to weigh in. Any advice appreciated.

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e-beach   100 MW

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Re: Do I need diodes with this layout?

Post by e-beach » Nov 19 2018 4:31pm

Nice looking chart. I don't see any need for a diode or resistor. Why were you thinking you needed them?
Edit: Actually you might want a diode after the 30 amp fuse before the battery as insurance.

:D :bolt:
Favorite Quote: "This is L.A., sugar. There is no 'over the top." --- Chris Erskine

Current build: Liahona w/ cheap front suspension and suspension seat post. Yescomusa 36v 800w generic front hub motor. 15ah Headway triangle mounted pack. Tronsung 30 amp,

Previous Build:1992 Trek Antelope 800 - Bone Crusher (no suspension) - Yescomusa 800 watt 36 volt front wheel kit. Don't do it! Get suspension!!!

MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 19 2018 4:58pm

e-beach wrote:
Nov 19 2018 4:31pm
Edit: Actually you might want a diode after the 30 amp fuse before the battery as insurance.
What kind of diode? Schottky? Zener?

And wouldn’t that prevent the charger from doing its job? Or is the idea to protect the charger from the battery?

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Re: Do I need diodes with this layout?

Post by e-beach » Nov 19 2018 9:24pm

It would be to protect the charger. Use the kind that is used in a bridge rectifier.

:D :bolt:
Favorite Quote: "This is L.A., sugar. There is no 'over the top." --- Chris Erskine

Current build: Liahona w/ cheap front suspension and suspension seat post. Yescomusa 36v 800w generic front hub motor. 15ah Headway triangle mounted pack. Tronsung 30 amp,

Previous Build:1992 Trek Antelope 800 - Bone Crusher (no suspension) - Yescomusa 800 watt 36 volt front wheel kit. Don't do it! Get suspension!!!

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Re: Do I need diodes with this layout?

Post by amberwolf » Nov 19 2018 10:11pm

Depends on the charger.

Smart chargers like the Satiator need "access" to the battery voltage to tell what it actually is at under charge current and at rest. These also usually disconnect themselves from the battery when charge is complete, so if it's left connected all the time, it doesn't drain the battery.

Dumb chargers like Meanwell LED PSUs and most of the cheap cahrgers included with batteries don't do any checking/etc., and a diode can help prevent them from draining the battery when not charging, if the charger is left connected all the time (like on my SB Cruiser trike, where it's built into the trike).

If you think someone might stick a piece of metal in your charger port and short out the battery, a diode is a good idea, but I expect that's a rare event.

The only other reason for a diode is to prevent reverse connections, but if you have a polarized connector, and you test the wiring before hooking things up, you don't have to worry about it.

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jonescg   1 GW

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Re: Do I need diodes with this layout?

Post by jonescg » Nov 19 2018 10:45pm

I've never seen a contactor with a 100 volt rated coil...

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TommyCat   10 W

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Re: Do I need diodes with this layout?

Post by TommyCat » Nov 20 2018 8:47am

Perhaps not what you where looking for. But the first thing that came to mind was a pre-charge resistor for the controller, and a freewheel diode for the contactor coil...
Last edited by TommyCat on Nov 20 2018 8:48am, edited 1 time in total.
See my completed Magic Pie V5 rear hub E-Bike build Here!

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fechter   100 GW

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Re: Do I need diodes with this layout?

Post by fechter » Nov 20 2018 8:48am

jonescg wrote:
Nov 19 2018 10:45pm
I've never seen a contactor with a 100 volt rated coil...
It would be possible to use a contactor with a 12v coil and run it off the DC-DC converter.

It might be good to put a diode across the contactor coil (reverse biased) if it doesn't have one built-in. The diode catches the voltage spike when you turn the coil off.

The controller Vcc doesn't need much current, nor does a 84v relay coil, so the 30A fuse should probably be much smaller, like 3A.
"One test is worth a thousand opinions"

MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 20 2018 1:44pm

fechter wrote:
Nov 20 2018 8:48am
The controller Vcc doesn't need much current, nor does a 84v relay coil, so the 30A fuse should probably be much smaller, like 3A.
Yeah perhaps I should add a third power circuit (3A) -- the 30A is primarily for the charger circuit. I was just "piggybacking" the contactor's coil off of that.

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MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 20 2018 1:46pm

jonescg wrote:
Nov 19 2018 10:45pm
I've never seen a contactor with a 100 volt rated coil...
here you go: https://www.ametekswitch.com/products/d ... -contactor

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MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 20 2018 3:33pm

TommyCat wrote:
Nov 20 2018 8:47am
...the first thing that came to mind was a pre-charge resistor for the controller, and a freewheel diode for the contactor coil...
Thanks! This page seems to describe my needs perfectly: http://zeva.com.au/Tech/ContactorJewelry/

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TommyCat   10 W

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Re: Do I need diodes with this layout?

Post by TommyCat » Nov 20 2018 4:26pm

Nice link. A keeper!

Speaking of your contactor coil... you'd better fix your wiring diagram. :shock:
See my completed Magic Pie V5 rear hub E-Bike build Here!

MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 20 2018 6:07pm

TommyCat wrote:
Nov 20 2018 4:26pm
Speaking of your contactor coil... you'd better fix your wiring diagram.
You mean like this?

Image

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24s16p, 84V 54Ah NESE modules + BMS wiring diagram

MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 20 2018 9:26pm

One thing though -- with the pre-charge resistors in place as shown in the updated diagram, won't that send a small amount of power to the DC-DC converter? Seems wasteful. I'm thinking the pre-charge resistors should be on a momentary switch which I would engage just prior to turning the key (not unlike a diesel motor). Thoughts?

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Re: Do I need diodes with this layout?

Post by e-beach » Nov 20 2018 10:57pm

Until the day you forget to use it. A switch for the dc to dc converter?

:D :bolt:
Favorite Quote: "This is L.A., sugar. There is no 'over the top." --- Chris Erskine

Current build: Liahona w/ cheap front suspension and suspension seat post. Yescomusa 36v 800w generic front hub motor. 15ah Headway triangle mounted pack. Tronsung 30 amp,

Previous Build:1992 Trek Antelope 800 - Bone Crusher (no suspension) - Yescomusa 800 watt 36 volt front wheel kit. Don't do it! Get suspension!!!

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fechter   100 GW

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Re: Do I need diodes with this layout?

Post by fechter » Nov 21 2018 9:20am

MJSfoto1956 wrote:
Nov 20 2018 9:26pm
One thing though -- with the pre-charge resistors in place as shown in the updated diagram, won't that send a small amount of power to the DC-DC converter? Seems wasteful. I'm thinking the pre-charge resistors should be on a momentary switch which I would engage just prior to turning the key (not unlike a diesel motor). Thoughts?

M
Yes, the current from the precharge resistor going to the DC-DC would be a problem.

One solution would be to have a separate smaller contactor for the DC-DC converter with no resistor across it.

Another solution would be to find a 3 position switch that goes off-precharge-on, so you are forced to have the right sequence.
"One test is worth a thousand opinions"

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Re: Do I need diodes with this layout?

Post by amberwolf » Nov 21 2018 11:02am

A number of keyswitches have an Off, Accessory, and On (or Ignition) set of positions. The Accessory position could be used for precharge, and On for turning on the contactor.

Some of them keep the Accessory position on while Ignition is on, most of them don't.

One of the ones I had a long time ago had a springloaded Ignition position, like a car's, that returned to the Run position--those aren't suitable for your purpose, unless they *also* have an Accessory position before the Run, to use for precharge.

MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 21 2018 3:13pm

Based on reviewing many previous threads here on ES on this very subject, I have come to the conclusion that the minor amount of current used to maintain the caps in the controller is not worth the bother and all the complexity needed to achieve it. Instead I am now planning on simply adding a circuit breaker before the controller and leave it on all the time -- except when I put the bike to bed in the winter. Additionally, there will be a precharge circuit added after the key switch. Upon the arrival of spring one needs to simply turn the key on for a minute or so to fill the caps, then flip the circuit breaker on for the rest of the season. The result is a much simpler, much less costly solution. As always, comments welcomed.

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24s16p, 84V 54Ah NESE modules + BMS wiring diagram

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fechter   100 GW

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Re: Do I need diodes with this layout?

Post by fechter » Nov 21 2018 3:39pm

Simple is good.

I've seen many setups that just use a big solar circuit breaker and no precharge resistor. The big breakers can apparently handle the inrush current without being damaged. Precharging won't hurt, but nice if the breaker can handle it if you forget.
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TommyCat   10 W

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Re: Do I need diodes with this layout?

Post by TommyCat » Nov 21 2018 4:51pm

I've been thinking about something like this...


Image



Delay make timer is a MARS PTD102. 6 sec. to 8 min. delay on make rated at 1.5 amps. Input 18 to 240 v AC/DC.

https://www.amazon.com/dp/B00SXB5YMW/?c ... RMTQ&psc=0

You'd have to get an auxiliary contact or double pole. And tie the switch power into the incoming power to the top contact using an inline fuse for the switch circuit.
See my completed Magic Pie V5 rear hub E-Bike build Here!

MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 21 2018 6:26pm

TommyCat wrote:
Nov 21 2018 4:51pm
I've been thinking about something like this...
Clever!

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TommyCat   10 W

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Re: Do I need diodes with this layout?

Post by TommyCat » Nov 21 2018 7:37pm

Version 2.0

Save the contactor... added switch fuse.


Image
See my completed Magic Pie V5 rear hub E-Bike build Here!

MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 23 2018 4:39pm

Pretty close to final layout, now including the controller and accessories:

Image

M

PowerVelocity 20kW Controller + QS273 + 20s BMS + eighty 5p N.E.S.E. Modules: 20s20p pack (72V 72Ah)
Last edited by MJSfoto1956 on Nov 27 2018 10:16pm, edited 5 times in total.

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TommyCat   10 W

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Re: Do I need diodes with this layout?

Post by TommyCat » Nov 24 2018 10:06am

MJSfoto1956 wrote:
Nov 23 2018 4:39pm
Pretty close to final layout...

If you don't mind me saying, I'd double check the converter's circuit breaker size. (Seems way too big.) And the use of a Zener diode in the pre-charge circuit?
See my completed Magic Pie V5 rear hub E-Bike build Here!

MJSfoto1956   10 W

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Re: Do I need diodes with this layout?

Post by MJSfoto1956 » Nov 24 2018 7:54pm

BOM (Bill of Materials) for my proposed 20s20p system:

(80) N.E.S.E. 5p Modules
(80) N.E.S.E. Serial bus bars
(80) N.E.S.E. double caps
(400) 18650 3400mAh Li-ion batteries
(1) VLDL DANL 72V max 20A charger
(1) Daly 20s BMS
(1) 72Vdc/12Vdc Waterproof 25A converter
(1) PowerVelocity 20kW controller + Bluetooth app
(4) 6AWG 2-hole lugs
(3) 6AWG 1-hole lugs
(3) 6AWG non-insulated flag terminals
(3) 8AWG 1-hole lugs
(4) 10AWG 1-hole lugs
(4) 6AWG Silicone Wire
(1) XT90 spark resistant adapter
(1) C-13 panel mount 110V adapter
(1) US 110V --> C-13 extension cord
(1) J1772 --> C-13 adapter cable
(1) 75A circuit breaker
(1) 25A circuit breaker
(1) 20A circuit breaker
(2) recharge resistors
(1) zener diode
Last edited by MJSfoto1956 on Nov 26 2018 7:42pm, edited 1 time in total.

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