BMS question! Noob alert

With one, you plug in one barrel plug and forget it s-l300%20(17865)

With the other, you take your board apart every time you need to charge it and you can only charge half your board at a time and you’re more likely to run the battery all the way down because it’s a pain in the neck to charge it, which increases the chances of early battery failure and getting stranded and reduces the amount of time you spend riding the board. Plus your board can die if you hit one puddle of water.

That‘s relative. For sure it’s more easy to just plug a laptop brick charger and good. But for my mtb for example, i have a easy to open case. I have a dual balance charger, so I can charge two lipos in one. It’s not a pain in the ass to plug the one more charging plug plus two balance plugs inside of my charger though :sweat_smile: and I even can take the lipos out and charge them in a safe lipo charging box. I think it all just depends on how the lipos integrated into the board. That’s why I didn’t understood that you said my suggestion with the balance charger is stupid and than suggest to use a bms for charge only.

I guess it’s the difference between making a “toy” or a “tool”.

You can’t really use it as a tool if it doesn’t have a BMS

If you just want a big boy toy, that will work fine

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To answer @Andy87 question about which charger is better, I think that for most people, the bms is better, but the imax charger is more fool proof

This was my logic.

The current setup is 9s which we all seem to confirm on. This setup is LiPo batteries and as you mentioned in another post - I want to get a BMS to avoid having to remove the enclosure all the time to charge them. I think that’s pretty fair.

When I get a BMS I’ll be getting a e-switch aswell which, to my knowledge, will mean I can get rid of the antispark key altogether. Is this correct?

My theory is to get a 10s (or even a 12s?) BMS and wire it so that the BMS thinks there’s 10 (or 12) batteries to charge. If I can do that buy simply leaving wires unplugged (closest to positive) then that’s fine, otherwise joining the wires together will surely bring the same effect.

Regardless, it is possible to use a 10s BMS for 9s LiPos. But why would I need to get a second one when I change my battery setup altogether? Could I not remove the connections and join them back up?

I didn’t realise this would be so difficult to understand :laughing:. Can you recommend a BMS for me please (10s and 12s)?

Cheers, Daniel

You probably right. For me it’s also just a hobby :stuck_out_tongue_winking_eye: So I guess I see some things from a other point of view than you

Yes the e switch would get rid of your anti spark. I like the Bestech bms, they are reliable for charging and discharging

Perfect. There seems to be so many BMS options on the bestech website. Which one should I go with?

Check out Build Kit Boards, they have a good selection for bestech bms

By the way, you need to discharge through the bms to use the e-switch

I just want to have a switch on the outside that I turn on to use the board and then a laptop style plug to out my charger in. I presumed the charge and discharge works through the BMS anyway?

Yes, it will replace the loopkey. You can still bypass a BMS and use the BMS for charging only. Or, you can use a full high-current BMS like that one you linked and discharge through it. There are pros and cons to that, I would not.

I’d use: a BMS for charge only and a loopkey OR a BMS for charge only and an antispark switch

Yes. Don’t join the wires, leave the extra ones unhooked on the most-positive end

Perfect. So I can get a 12s BMS and still be able to use it with 9s, 10s or anything up to 12s for that matter.

Why do you suggest not using a BMS for charge and discharge? Surely that’s the purpose of them?

Uhh, I would go with the 10s Lipo bms

Yes

Yes, it is. But you have a balance to make. If you go down a big hill with a full battery, and you hit the brakes, in an emergency situation would you rather slightly damage your battery by a tiny overcharge, or cut off the charge to keep the battery perfectly healthy, but leave you with no brakes? In the choice between battery and face, face wins every time

Also the VESC ESCs have the ability to cut off throttle on a fully-discharged battery but keep brakes and controls working. The BMS isn’t designed to do that, and while it might work under some circumstances, it’s not as good and creates a lot of heat in it.

Essentially, the VESC has software to handle those situations better than a generic BMS that cares only about battery health first and foremost whereas the VESC is designed to care about human health first and foremost.

Not using a BMS for discharge has cons too, though. If you get a short-circuit between the VESC and battery, the BMS will not help prevent a fire…

Also heavy vibration makes things fail in the most unusual ways

Okay now I’m majorly confused. Of course I would rather have brakes as apposed to none.

My understanding is that charge is coming from the wall to charge the battery pack and discharge is to power the FOCBOX which in turn moves the motor.

I’m getting confused here. My understanding is that I would connect the cells in a 10/12s 4p fashion, connect the BMS to the cells to allow for me to charge via a wall plug. It would then have a FOCBOX connected to it with an e-switch inbetween which acts as the on off switch. The FOCBOX is connected to the motor.

I think I’m starting to misunderstand things. Sorry to appear stupid. Can you explain in a different way?

Charge comes from the wall and the braking system. When you brake, it dumps the energy into the battery.

So, this is hard to explain to someone who is just learning all of this stuff, but read this all the way through, Here we go…

The VESC has a setting that when enables regenerative breaking. This means that everytime you brake, the vesc somewhat turns the motor into a generator, and puts small amounts of energy back into the battery. The bms’s purpose is to balance all the cells, but also to protect the battery from over charging. What @b264 is saying about the no brakes is true, but highly unlikley. So if you charge your battery to 100%, and then immedietly go down a hill with your brakes on, the vesc is trying to recharge your batteries, and the bms is protecting your cells from over charging, so it disables the regenerative brakes. This mean that you have no brakes (duh).

Also, you can use your bms in two ways, bypassed and non-bypassed. Bypassed means that you connect the bms only for charging, and that the energy goes straight from the batteries to the vesc when driving. Non-bypassed is the same connection for charging as bypassed, but the energy goes from the batteries through the bms to the vesc when driving. The brakes being disabled would only happen during non-byassed, but like I said, that is very unlikely. What you said above was all correct. If I were you, I would go with the 12s LiPo Bestech BMS from BKB. Hope this wasn’t confusing.

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@b264 @Jake2k17

I understand now. I programmed my FOCBOX for regen braking so that’s what it’s doing already. It seems like something that shouldn’t be worried about too much because the likelihood of something going wrong would be slim. If it was high, no one would have these boards.

Okay so I’m going to get a 12s BMS and then do the no connect thing with the wires. I could even buy another zippy battery to bring my LiPo pack up to 12s.

Thanks for all the help, Daniel

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