Battery Equaliser

[BG bicycle]

A while ago I built 10s 13p pack using LG MH1 cells. The battery was built in several stages from 8p upwards. The BMS, an all in one type couldn’t balance such a huge battery and my want to fast charge eventual the pack went out of balance.

Then upgraded the BMS, fitting a smart BMS allows’ monitoring of all the cells. That couldn’t resolve the issue either. No surprise the charge were frequent at 7.5 amps.

Present use a battery equaliser that moves the voltage between cells up to 3 amp. It’s an effective balancer that is completely regulated at the charger and from a chargers’ voltage.

I now charge at 8.10 amps and the pack balances perfect and in super fast real time. As quick voltage rises the equaliser pulls down and brings up those lower cells.

Soon I’ll no longer ride with a standard BMS. These are unnecessary and eventual I’ll only ride with cell loggers and a circuit breaker plugging the equaliser in during a charging session.

Anyone else using this system?

 

[KirstinS]

I don’t totally understand to be honest

Do I understand the system doesn’t prevent any cell strings dropping below acertain voltage eg 3.1v for most lithium ?

Also , charging a such a rate empirically will shorten the life of the cells.

Neither method , if I understand , appears better than BMS. Or at least I don’t get why !


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[BG bicycle]

At the moment I ride with a smart BMS, connected during discharge this allows monitoring of the cell voltages in real time. Since it’s useless during the charge cycle as it cannot balance the battery unless want to wait several days. Again, this be just another reason to remove BMS, once cell loggers are attached.

The Low Voltage Cut-off: I intend to utilise the controller, shuts down at 3.1 volts.

Long term the smart BMS, become redundant with LVC alarm cell loggers to warn when within a set voltage limit. At 70kms the battery can remain above 36volt, lowest level seen were just below 36v on a 50km ride mostly up hill. Digress, on that occasion I stopped at a Shell petrol station and accessed an exterior socket (with permission). Why duplicate via a standard BMS, given the risks associated with those to a battery. Less components, less risk, etc.

Shortening the life of the cells. The starting voltage is 8.10Ah and this decreases as the battery holds more charge. I don’t figure how the cells degrade faster it’s a 41.6Ah battery with 8Ah isn’t that big a current comparison that size of battery. Also I never charge to 42 volts, always 80% of voltage capacity.

I find the system at present far superior. The future version with less components, present time produces a better charge, more even charge and the equaliser is available to expand (even use 5s) and swap between bikes.

Why have a BMS, system that’s fixed to one bike and one that cannot handle a large battery. There arises at certain Ah, these standard BMS systems are a waste of funds and serious risk damaging a battery.

 

[KirstinS]

It appears to me that, for you, mega fast charging is the most crucial factor

And I agree that few (if any ) bms will cope with your requirement

However , I don’t understand your logic about why this won’t kill your cells fast . It will

On discharge , cell loggers or lipo alarms work just fine. I’ve used them myself plenty in the past

Personally , I’d never rely on the lvc of a controller as that is pack view not a cell string view. Sure fire way to kill your pack

So again, it appears to me that your desire for fast charging is at the expense of cell longevity at best

I understand your position but the solution has flaws . But if time and money are endless , or th reduced life expectancy is worthwhile for you....then all power to you. But I wouldn’t expect many , if any , to follow your approach.

It is fast charge upside with expensive downside at very very best

It certainly isn't for the 90 something % !


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[BG bicycle]

Is it really a fast charge? From reading appear to define time rather than capacity in Ah and volts and the actual charge current, as its all combined that defines fast and the degradation issues associated.

To limit, or prevent fast degradation one has reduced voltage capacity proven to reduce degradation, extend battery life.

Another factor is each cell holds a total capacity of amp hours to be 41.6Ah, ten cells equals 36volt nominal, this equates to a distributed charge per cell of less 1Ah. Where be the stress upon a LG MH1 group cell in that current? Isn’t any, mere fig of imagination that a large cell with quality cells ever become stressed.

The equaliser could add voltage and current to a low voltage cell. Maximum 3amp, this remains well within the cell group charge rating.

The controller LVC, isn’t their to be utilised, the cell loggers with audible alarm would sound at 3.5volts. I explained: I’ve never ran the battery that low.

Flaws? All BMS, systems have risks, hazards. When at a certain battery Ah, this is a superior way. Then 90% are riding on low capacity batteries and very obvious a cheaper route, and a shorter one. Cost shouldn’t overide pleasure. Perhaps you agree?

 

[awol]

Smart BMS with Max charge 20amp with balancing
Max discharge 59amp all with realtime bluetooth app connectivity.
https://www.speedict.com/

 

[BG bicycle]

Come on be serious, what is the balance capacity of that small box?

Charge capacity is only its ability to pass current rather than balance.

I had a waterproof BMS, that could it claimed handle 60amps. Again on,y it’s ability to pass current rather than balancing current of only burns power rather than shifts power from the highest to lowest cell.

Lots of failure points also on that BMS, too many hazards attached although I’m sure fine for a small 10Ah battery. Read of far too many stories where the BMS, responsible destruction of entire pack. Will keep to the better option as described.