Making the products we want, intelligent bulk charger.

[Teh Stork]

Hello, I've got a lot of projects going - and lately I've been looking closer into battery management and charging.

I want the charger to be intelligent in the sense that it will charge it up to the full 4,2V prior to riding. Storing the battery at 4,2V is not optimal, so storing it at a lower potential will squeeze out some extra cycles. Examples of 4 to 4,1V is normally used to prolong battery life. The capacity gain of charging to 4,2 isn't much, but it varies too much from chemistries to put a number on this. What I'd like to make: I come home at 1600, put the charger in - program the charger to charge it to 4,2V - at 0800 the next day. I want it to immediately bring the pack to the setpoint for short time storage, then I want it to fully charge up before my preset time is met. Features like preparations before long time storage and similar stuff could also be implementated easily.

I have some experience with c++, microcontrollers, java and (interfacing towards) phones - but little experience with chargers. I need more experience with making buck chargers/regulators. This thread (I hope) could be the place to share ideas around this, so we can make something specifically built for ebike use

 

[motomech]

It exists, Hyperion 1420i
Although I don't leave it on overnite, no need to. It's soooo fast and my pack is small :lol: .

 

[chilledoutuk]

So your saying the hyperion has the ability to specify when you want a battery charged by and it will charge it before that set time?

 

[amberwolf]

Since what you really seem to want is a timed start-of-charge, and a charger that can monitor individual cell voltages, it sounds like it would be much easier to simply create a timer and wire that into the start button on an existing RC charger.

A slightly better way would be to take a bunch of separate single-cell chargers that have the cutoff limit you want, and wire them all to a power strip, and use an existing wall-outlet lighting timer to turn the whole bunch on at once. This way there is no wait for balancing to occur, which on smaller RC chargers or other bulk chargers could take hours. Every cell (or group) will be individually charged to the proper voltage, independently of the others.

If the chargers tend to leak current back into them when off, then you could do the more complex method of adding relays or solid-state switches between the chargers and the cells, and power them off a separate wall wart also plugged into the same strip. Then they will turn on and connect only when the whole charger setup is turned on by the wall-outlet timer.

Either of these methods will accomplish the main part of your goal, to charge them only just in time for the ride.


To do the other part--storage-level charge, you could add a simple voltage sense to each cell, basically just like Methods' HVC/LVC units, so that they are triggered by the storage-level voltage you want to stop temporarily at. Then run that to a relay unit that turns off one of two ac adapters that power the main relay units that cut the cells off from the chargers.

Then, you'd not use the wall-timer on the entire set of chargers, but instead only on the other ac adapter for the relay power supply. Thus, once the timer kicks in, it turns the relays back on and they finish charging up to the charger max voltage.


Much easier than all that programming and power supply design stuff. :lol:

 

[docnjoj]

So your saying the hyperion has the ability to specify when you want a battery charged by and it will charge it before that set time?

Not that I can see in the instructions. However I have not used mine yet, I am still trying to figure out all the flow-charts. May be a long time user can comment.
otherDoc

 

[ZOMGVTEK]

It exists, Hyperion 1420i
Although I don't leave it on overnite, no need to. It's soooo fast and my pack is small :lol: .

The Hyperion 1420i only charges 14S at 550W max. A real mans bulk charger starts at a breaker tripping 2kW and does at least 24S.

At 550W, it will take HOURS to charge a big bike pack. That's quite a lot of waiting.

OP: You can have a bulk charger out of current limited power supplies on a timer... Plug the bike in when you get back, set the timer to kick on long enough to charge a pack at 10% SOC, even have it auto-off 10 minutes before you need it to let the cells settle. Might want some sort of overvoltage protection and a fire-proof garage area, but it sounds like a fairly safe thing when done right with cell-level protection that can disable the charger. The lite BMS Methods sells will do the trick.

 

[chilledoutuk]

It exists, Hyperion 1420i
Although I don't leave it on overnite, no need to. It's soooo fast and my pack is small :lol: .

The Hyperion 1420i only charges 14S at 550W max. A real mans bulk charger starts at a breaker tripping 2kW and does at least 24S.

At 550W, it will take HOURS to charge a big bike pack. That's quite a lot of waiting.

OP: You can have a bulk charger out of current limited power supplies on a timer... Plug the bike in when you get back, set the timer to kick on long enough to charge a pack at 10% SOC, even have it auto-off 10 minutes before you need it to let the cells settle. Might want some sort of overvoltage protection and a fire-proof garage area, but it sounds like a fairly safe thing when done right with cell-level protection that can disable the charger. The lite BMS Methods sells will do the trick.

Erm your comparing a bulk charger to a extremely high quality balance charger with regard to charging power sorry but that is just stupid.

Without a bms you wont be able to take your eye off such a bulk charger (unless you want a fire) and not many BMS's let you charge at 2kw anyway.

At least with a charger like the hyperion you could plug in your pack and leave it knowing that it will be charged properly and be much less likely to blow up on you.

lets think an hour watching a battery or 4 hours doing something else whilst a better charger does the job for you?

 

[NeezyDeezy]

Yeah, +1 on what Amberwolf said

 

[amberwolf]

Without a bms you wont be able to take your eye off such a bulk charger (unless you want a fire) and not many BMS's let you charge at 2kw anyway.

FWIW, the "BMS" by Methods he is referring to does not have a power limit in and of itself, as the basic units are just LVC and HVC units to prevent cell damage/fire in case the charger doesn't stop when it should, or things are badly out of balance.

There *is* an HVC charger cutoff unit that has a power limitation, but there's no specific need to use it, if the bulk charger used has a "shutoff" pin/signal input, or if you want to build a circuit that cuts off AC input power to the charger instead of output power. Or if you want to mod the charger cutoff unit to handle higher power, with more parallel FETs and really good heatsinking/fans.

This "BMS" doesn't balance anything, so you'd still want to be checking that manually and using a single-cell charger to top off low cells, or resistively draining high ones (or better yet replacing those cells).

 

[ZOMGVTEK]

Erm your comparing a bulk charger to a extremely high quality balance charger with regard to charging power sorry but that is just stupid.

Without a bms you wont be able to take your eye off such a bulk charger (unless you want a fire) and not many BMS's let you charge at 2kw anyway.

At least with a charger like the hyperion you could plug in your pack and leave it knowing that it will be charged properly and be much less likely to blow up on you.

lets think an hour watching a battery or 4 hours doing something else whilst a better charger does the job for you?

With good HVC/LVC protection, a fairly high capacity well balanced pack, and a timer in place, things can't really get out of control.

You can get balancers that plug into the balance taps, and auto-balance once connected and cell voltages reaches a preset threshold. Hook your cells balance wires up to a single plug, like a DB25 for 24S configs, and you have two connections to make for high power bulk charging, with protection and balancing. Plug the DB25 in to the balance taps, plug the bulk charger into the pack, and walk away. It would be exceedingly difficult for things to get out of hand, unless a pack has a cell that wants to flame up under 1C charging within normal voltages. In that type of case, the cell will probably burn even on a Hyperion.

The Methods 'lite' BMS will allow you to trip the power to the charger if any cell goes too high, and it can kill controller power if any cell goes too low. The only issue would be if you had an overdischarged pack to begin with, that you just dropped onto the bulk charger blindly. You can add something like the BM-6 units onto your DB25 balance rig that will beep at you if any cell is too low, protecting you from bulk charging an overdischarged pack. That would be exceedingly safe, robust, and reliable, and even more than the OP wants. It's not even that expensive as well.

Both do the same job, one just does it many times faster. I find it to be an extreme limitation to have to wait longer than 30 minutes or so to charge the bike up before use. Some people might be fine with not being able to use the bike for hours, but faster tends to be better. You can get roughly 30 minute charge times if you have the pack sitting at 3.85V/cell, and bulk charge at 1C. 1C is not very hard on most every modern Lithium battery.