BMS suggestions

[CONSIDERABLE SHOUTING]

Never saw any stickied threads on BMS'es or specifically, beloved BMSes that have been tested by the community.

Right now I'm getting ready to make my first pack- I might stick around 48 volts, but there's a chance I'll slap together a smaller pack instead to both use up poor quality cells and to learn. Thing is tho, i'd like to have more than just a reliable BMS- i'd like one to have options for charging to 4.05 / 4.1 volts instead. What brands have ya'll been using that have worked out well?

 

[gobi]

I am on bms hunt too for my juiced batt rebuild.

I think JBD or ANT are good and used widely.

JBD on ebay sold by Srikobatterries are good value ad FAST shipping.
ebay has 8% cash back or whatever they call it.

Can't believe I can get a smart JBD bms for less than $50 (40A)

 

[john61ct]

JBD = LLT

Resold as Overkill BMS

The key is documentation, help if you need it

Apparently a good supplier
https://store.currentconnected.com/product/jbd

Or go direct

https://www.aliexpress.com

https://s.click.aliexpress.com/e/OstYsoYY

https://s.click.aliexpress.com/e/qUAMAkA8/item/32794186005.html

https://www.lithiumbatterypcb.com/product-instructionev-battery-pcb-boardev-battery-pcb-board/ev-battery-pcb-board/smart-bms-of-power-battery

Same?

RJXZS Ali shop https://m.aliexpress.com/item/32669831187.html

 

[velias]

Speedict .com makes a well documented one.
I dont think it works via apple phones though.

 

[john61ct]

Don't let the tail wag the dog

 

[999zip999]

What what cells are you using and what are you going to use this battery for how many amp controller we've been riding hills or is this for flatland what motor would you be using. 12s, 13s or 16s ,? All 48v.
So what cell not just name but model number. All important.

 

[JackFlorey]

Never saw any stickied threads on BMS'es or specifically, beloved BMSes that have been tested by the community.

Right now I'm getting ready to make my first pack- I might stick around 48 volts, but there's a chance I'll slap together a smaller pack instead to both use up poor quality cells and to learn. Thing is tho, i'd like to have more than just a reliable BMS- i'd like one to have options for charging to 4.05 / 4.1 volts instead. What brands have ya'll been using that have worked out well?

As you probably know the BMS doesn't set the charge voltage for your cells. The only time the BMS gets involved is when you top balance, because generally the cells have to hit 4.2 volts to top balance.

You can certainly get a programmable BMS like the Orion but that's overkill. Alternative - use a standard (4.2 volts per cell) BMS and then just charge to 4.1 volts per cell when you charge. Occasionally (once a month or something) charge to 4.2 volts per cell for an hour then ride immediately. That will balance the pack but greatly extend its lifetime, since it spends very little time at 4.2 volts.

 

[CONSIDERABLE SHOUTING]

As you probably know the BMS doesn't set the charge voltage for your cells. The only time the BMS gets involved is when you top balance, because generally the cells have to hit 4.2 volts to top balance.

You can certainly get a programmable BMS like the Orion but that's overkill. Alternative - use a standard (4.2 volts per cell) BMS and then just charge to 4.1 volts per cell when you charge. Occasionally (once a month or something) charge to 4.2 volts per cell for an hour then ride immediately. That will balance the pack but greatly extend its lifetime, since it spends very little time at 4.2 volts.

Thanks, I knew I had missed something.
You guys have threads that mention most of these cheap chargers have potentiometers that can be tuned down in them right? I've been snagging these "EVA Plus" wall chargers for literally $0.50 so I think I can sacrifice a few to see if they're easily modded.

 

[amberwolf]

what is an "eva plus wall charger"? google didn't find anything apparently relevant, just stuff for big ev charging stations.

 

[JackFlorey]

You guys have threads that mention most of these cheap chargers have potentiometers that can be tuned down in them right? I've been snagging these "EVA Plus" wall chargers for literally $0.50 so I think I can sacrifice a few to see if they're easily modded.

The "cheap chargers" that are actually AC to DC switcher power supplies almost always have a potentiometer on them to adjust the output voltage. Meanwell makes a lot of these.

Small dedicated chargers often do NOT have potentiometers because potentiometers cost $$, and it's cheaper to put fixed resistors in to permanently set the voltage - even if it's off a bit. You can add a potentiometer to these but it takes some electrical engineering know-how. The EVAPLUS would fall into this category and it looks like it's the sort that would not have a pot - and it looks like the case would be a bear to get open. It looks glued or ultrasonically welded.

Larger/more expensive chargers often have a pot so the voltage can be set more accurately.

 

[CONSIDERABLE SHOUTING]

what is an "eva plus wall charger"? google didn't find anything apparently relevant, just stuff for big ev charging stations.

When I get home I'll post pics- basically, there's this reseller store where I can buy laptop batteries for fiddy cents and that's where they largely come from out of bins full of junk. I've pulled a couple of things similar to the Meanwells, but mostly I have what Jack is describing- no big loss if they are, might have 10 of them for $5 bucks :lol:

 

[john61ct]

Just a nit pick on terminology

Distinguishing between a proper "charger" and a PSU that can be used for charging.

Current limiting is a given for chargers, and usually found on decent PSUs. Ideally user adjustable, and not to be confused with "current protection" latching or hiccup style.

More definitive is automatic charge termination, based on some logic that says the battery is now full.

PSUs do not do this, just keep going until the user or BMS disconnects the battery.

Neither approach is recommended unsafe and not good for pack longevity.

Adding a HVC circuit to cut off the source gives a CC-only charge, and works for both PSUs in effect turning it into a charger, and chargers that do not allow AHT Absorb (CV) Hold Time to be set short enough, in effect bypassing the logic of the regulator as to when the charge is judged complete

Ideally AHT is adjustable, and also ideally so is the CV setpoint.

 

[JackFlorey]

Distinguishing between a proper "charger" and a PSU that can be used for charging.

Current limiting is a given for chargers, and usually found on decent PSUs. Ideally user adjustable, and not to be confused with "current protection" latching or hiccup style.

More definitive is automatic charge termination, based on some logic that says the battery is now full.

PSUs do not do this, just keep going until the user or BMS disconnects the battery.

Agreed. And to add to that:

There are two kinds of power supplies out there - ones with that hiccup or shut down on overcurrent (not really usable for charger) and ones with current limiting (usable for charging.) Small high power PSU's that do current limiting are useful for on-the-go charging because you can get VERY high powers for not a lot of money. For example, the Huawei R4850G2 will do 48 volts at 56 amps - and can be had (used) for $100-$150. The various Meanwell supplies are even cheaper than that. Their LED ballast series (HLG) will often allow you to adjust both charge voltage and current limit - which is very nice to tweak the max charge rate of smaller packs.

Such power supplies MUST be adjusted to give you the right charging voltage. A 48 volt power supply feeding a 36 volt pack will indeed charge it - but towards the end of the charge will rapidly take it overvoltage (max charge voltage for a 36 volt pack is 42 volts.) Adjusting voltage down rather than up is a lot safer since you are reducing the power that the power supply has to supply by going below the "standard" voltage, and thus you are less likely to overheat or overload the supply.

But all power supply type chargers should only be used for on-the-road quick charging, because as you mentioned they don't terminate charge. Not a big deal at all if you are charging for an hour while you stop for lunch, but a big problem if you plug it into your garage overnight. Primarily because sitting at 4.2 volts per cell is bad for longevity of the cells, but also because if the battery does have a defect, or is severely unbalanced - that can lead to battery pack damage and even fires.

Fortunately for overnight charging you don't need a fast charge rate, and thus lower rate chargers (that terminate) work well.

 

[john61ct]

Such power supplies MUST be adjusted to give you the right charging voltage. A 48 volt power supply feeding a 36 volt pack will indeed charge it - but towards the end of the charge will rapidly take it overvoltage

The adjustable HVC circuit idea can also do that if a PSU does not adjust V (enough)

Cut off PSU input when battery hits the setpoint.

With a BMS as safety backup for when the primary HVC fails.

 

[JackFlorey]

The adjustable HVC circuit idea can also do that if a PSU does not adjust V (enough)

Agreed, although you leave some capacity "on the table" by eliminating the CV part of the charge. Amount of charging capacity lost will be somewhat proportional to power - the higher the power, the more capacity lost.

 

[john61ct]

Yes, and that is intentional.

SoC% - really capacity utilisation - pushing anywhere near the "do not approach" datasheet specs at both the top and bottom of the curve (DoD%)

is murderous of cycle lifespan.

Just sacrificing 4% cap utilisation at each end can triple cell lifespan. Also greatly reduce balancing issues.

People talk about voltages but as you point out that is not really the key variable, means nothing without a C-rate spec.

So CC-only stopping at 4.15V, can be exactly the same SoC point as holding 4.10 CV until trailing amps hit 0.01C

At the bottom, analogous advice is using rested isolated voltage measurement to calibrate your LVC while in use.

If you really need that extra range, increasing your pack size to allow for that lower capacity utilisation results in much better value for money on an annualised basis.

Of course there are competitive use cases counting every gram where packs are retired after a few dozen runs...

Relevant:
https://www.rcgroups.com/forums/showthread.php?4039797-What-are-signs-of-bad-battery#post48416387

 

[CONSIDERABLE SHOUTING]

Relevant:
https://www.rcgroups.com/forums/showthread.php?4039797-What-are-signs-of-bad-battery#post48416387

Thank you john, I really appreciate that- unfortunately, I'm nowhere near high enough level to understand what you just said :lol: I'll go through that thread you linked tomorrow.

I finally got around to looking at the power supplies I've found, and like you said- only two were NOT switched mode supplies. Most of them have the single hard plastic 3-prong charge port seen here, and most of them charge at 42 volts or so. I think they go to a common pack manufacturer, but I cannot say which one and I haven't seen any female ports to take advantage of them.

I did however, get these two actual chargers, and I think I got both of them for 50 cents- hell of a steal, though the UY600 clearly shorted on it's cables and I'll need to rip it open and see if it's salvageable. I Think it's this one here:

https://www.alibaba [DOT] com/product-detail/48v-10a-lithium-ion-battery-charger_60617105984.html

 

[john61ct]

As you come across phrases you don't yet grok

google the jargon at some point it gels

If not ask specific questions and someone will help explain

maybe even me [emoji39]

 

[ttshaw1]

Have you guys ever considered diyBMS (v4)? https://github.com/stuartpittaway/diyBMSv4 I stumbled across this today. It looks like it's designed with power banks in mind, but I'm not sure if that matters. It's got a lot of nice features and I respect that it's open source. I'd consider using one if I built my next battery myself.