Overkill BMS Turn On/Off Switch

[sshibly]

I am building a 4s 12v system with Eve 280AH cells,

I bought an Overkill BMS yesterday and it was shipped promptly (impressed, kudos to Overkill)

I see it has a connection for On/Off switch, can someone tell me what I need and how it works please.

Thanks,

 

[HRTKD]

From the Owner's Manual:

2.4.6 External Switch
An optional external switch can be wired to the BMS via the included 2-pin pigtail (JST-XH, red/black wires).
If the configuration option is enabled within the BMS, discharging will be disabled when the switch contact is
open. When the switch is closed (or a jumper is in the place of the 2-pin connector), the BMS will operate
normally.

 

[sshibly]

Jim, Danke!

I found a few 3 pin slide switches in my stash, I am sure I can use em. Now to figure out what i have to mount the switch.
I tried looking for a 2 pin slide switch already mounted on a little board, no dice :-(

 

[Ampster]

I tried looking for a 2 pin slide switch already mounted on a little board, no dice :-(

I find the common toggle switch easier to install because they just take a round hole. This is a low voltage low current switching function. More of a convenience to avoid draining the battery although I have not tested that assumption.

 

[Gazoo]

Doesn't the lock on the screen when the app is set to driving mode accomplish the same thing? Tap the lock on the screen and there is no discharge. I don't know what the difference of using the switch or using the app would be? I am only familiar with the android app.

 

[alvise]

I guess you can use a relay and operate the "switch" with some logic. For example, maybe you want to shut down everything after a certain hours and you can easily do it putting a timer on the switch.

 

[sshibly]

I just received my Overkill BMS today [THANKS for blazing fast shipping!]

App let's me shut everything down, does it mean there is NO idle draw after that?

Toggle switch - would something like this work?

 

[sshibly]

I guess you can use a relay and operate the "switch" with some logic. For example, maybe you want to shut down everything after a certain hours and you can easily do it putting a timer on the switch.

Relay would work, but it is a not a timer thing,
My van sits for weeks till we go out fishing again or just drive it around to charge the batteries,
My plan is to keep the LIPO (280AH) cells at 80% SOC and shut everything down with one switch which is easily accessible.

LIPO> FUSE on + > BMS > Breaker > SAMPLEX 1500W PS(with remote control)

If I drop the breaker, the BMS still has power, which is nice to monitor the voltage. But I want to able to shut ALL draw off the LIPO

The longest my van sits is about 3 months when we are blessed with nearly 180 inches of snow here in West Michigan

 

[Ampster]

does it mean there is NO idle draw after that?

My understanding is there is no draw if you unplug the balance leads. I do not know about the switch or turning off via the app. You would have to test that to be sure before leaving your batteries unattended in the cold for 3 months.

 

[sshibly]

My understanding is there is no draw if you unplug the balance leads. I do not know about the switch or turning off via the app. You would have to test that to be sure before leaving your batteries unattended in the cold for 3 months.

All of them? do I have to pull all of them?
I guess if the BMS is adding up the cells then I have to pull all of them.

oh, I can see my battery looking like the cockpit of a small aircraft with all the toggle switches,
good thing I did not go for a 16s 48 battery

 

[Ampster]

All of them? do I have to pull all of them?

It is only two plugs for a 16S BMS. Email Steve at Overkill, he probably knows. The unknown issue with some of these devices is they may only get power from one or two cells and even though the current may be small it could add up over 3 months and unbalance your pack.

 

[Gazoo]

All of them? do I have to pull all of them?
I guess if the BMS is adding up the cells then I have to pull all of them.

oh, I can see my battery looking like the cockpit of a small aircraft with all the toggle switches,
good thing I did go for a 16s 48 battery

I think it would be easiest to install a battery disconnect switch? But my guess, and it's just a guess, is the BMS could be left connected for a number of years before there would be anything to worry about providing the load is turned off, either from the app or a switch. Ask overkill to be sure. Also as far as I can tell the only time the bluetooth draws power is when the app is open.

 

[HRTKD]

I think the question about a disconnect has come up before. Here or on the Overkill Solar reddit page. I was thinking that as long as the (red?) lead to the positive terminal is pulled, it shouldn't have power. But there is a reddit post that says otherwise.

On one of the wiring diagrams it refers to the port as a discharge port switch. So it doesn't sound like it's going to turn off the BMS.

 

[sshibly]

It is only two plugs for a 16S BMS. Email Steve at Overkill, he probably knows. The unknown issue with some of these devices is they may only get power from one or two cells and even though the current may be small it could add up over 3 months and unbalance your pack.

Sorry, typo in my post,
My batt is a 4s 12v system using overkill 4s bms

Yes, I agree, pulling the main battery + is the way to go,
Shutting everything off at the root is the best option for long hibernation times.

 

[sshibly]

I wonder if pulling the main negative of the BMS shuts it down?

 

[Gazoo]

I wonder if pulling the main negative of the BMS shuts it down?

Why don't you either message Steve and ask him, or shoot him an email? I am sure he would know the best and easiest way to go about this. Whenever I have had questions I have contacted him. Or try this @OverkillSolar ?

 

[Ampster]

I wonder if pulling the main negative of the BMS shuts it down?

I agree with @Gazoo , Steve is very communicative. Even pulling the main negative will still leave the small negative from the balance connector and I think the BMS gets its power from that connector which is why I suggested pulling it. However I am not suggesting switching the small negative because that could fry the BMS like any change in balance leads can do without unplugging the connector first.

 

[Gazoo]

Also I would think Steve would know how much current the BMS draws when sitting idle. It might not have to be disconnected. Just turn off the load and maybe turn balancing off.

 

[OverkillSolar]

The idle power draw of the 4s BMS is less than 5ma

The discharge shutoff switch prevents system loads from discharging the battery.

Unplugging the balance wires will take the standby power to zero but the cells still have a self discharge rate.

 

[Ampster]

The idle power draw of the 4s BMS is less than 5ma

Do you know if it is evenly distributed across the cells? The reason for my question is that I used a some CellLog8s on a pack years ago and found out that they drew power from only the first few cells and contributed to
an imbalance. Since the purpose of a BMS is to balance a pack I suspect it is better engineered that an inexpensive monitoring device like a CellLog, but I thought I would check my assumption.