$10 DIY Smart Charger Alternative / Updated_Ver 3.0 @<$30

[Gionnirocket]

Cool little circuit you’ve assembled. I totally agree that hacking is part of the fun. I hack other thing last for the same reason. I may use this for my 36v battery. Maybe I can use the same unit for a 36v battery and a 48v battery. Though, at the price, maybe I’ll make a separate one. I like to monitor my charging.

Depending on your use between the two batteries. . .
Very easy to adjust voltage and I've set it up so it's easy to swap out charger and battery input/output connectors. But if I had to change back and forth daily I'd definitely build 2 for convenience.

 

[Gionnirocket]

With a new bike and battery I had to update my charge adapter similarly to the mod' @rounds had to make.
The safety features of the Zen battery does not output voltage on the battery charge port unless it receives a handshake from the charger.
So I had to install a momentary contact switch which needs to be held for 2 seconds to initiate the charge... then it's all automatic to my desired SOC as before.


Special thanks to @Zen Support for helping with the necessary cables as their proprietary 3 pin Julet connector was impossible to source.


One question for Mr. @Ravi Kempaiah...
Is it correct to assume that Watt-hour in equals Watt-hour out?
Example...
If I charge to 50.0V
Then ride 20 miles.
Then charge to exactly 50.0V again with a total of 155Wh being input back into the battery.
Can I divide the Wh in by miles driven to have a fairly accurate Wh per mile?
(155Wh/20mi = 7.75Wh/mi)

 

[Ravi Kempaiah]

With a new bike and battery I had to update my charge adapter similarly to the mod' @rounds had to make.
The safety features of the Zen battery does not output voltage on the battery charge port unless it receives a handshake from the charger.
So I had to install a momentary contact switch which needs to be held for 2 seconds to initiate the charge... then it's all automatic to my desired SOC as before.
View attachment 173481

Special thanks to @Zen Support for helping with the necessary cables as their proprietary 3 pin Julet connector was impossible to source.
View attachment 173482

One question for Mr. @Ravi Kempaiah...
Is it correct to assume that Watt-hour in equals Watt-hour out?
Example...
If I charge to 50.0V
Then ride 20 miles.
Then charge to exactly 50.0V again with a total of 155Wh being input back into the battery.
Can I divide the Wh in by miles driven to have a fairly accurate Wh per mile?
(155Wh/20mi = 7.75Wh/mi)
View attachment 173480

Wh - in will always be > Wh - out.
There are inefficiencies with every charger, and it is safe to add 5-8 % buffer to compensate for that.

 

[Gionnirocket]

Wh - in will always be > Wh - out.
There are inefficiencies with every charger, and it is safe to add 5-8 % buffer to compensate for that

Thanks Rav'
Yes I'm aware of charger inefficiencies... but I'm measuring Wh -in post charger so the charger inefficiency are bypassed and the remaining concerns would be the wiring, the BMS and the internal resistance of the cells.
Since the generated heat in these areas is negligible (as far as I can tell)
Do you think the buffer lower (1%)... or am I assuming incorrectly?

 

[il Munduato]

Here's the $30 version.
Having the same necessity of the momentary contact switch to initiate the charge...
I opted for an Off Delay Relay which makes the process automated. This allows me to plug everything in and start a charge by a home automation timer early in the morning or by app while still lying in bed before getting up as well as saving a trip to the basement to initiate it manually.

I couldn't locate a 48v panel mount relay so I had to add a voltage step down brick.


I also changed the input to panel mount instead of the cord and connector for neatness.



It works like a charm and allows for a very granular SOC level.


Great thing is that the set up also adds multiple levels of safety as the Home Automation outlet as well as the charging relay both have adjustable maximum time settings so things shut down at a preset amount of time. Even if everything fails (2 timers + 1 SOC shut down) the worst that can happen is that you're back to the basic charger / bms shut down safety features... but having all 3 fail at the same time I find highly improbable.

 

[il Munduato]

I found myself occasionally needing to restart the Off Delay Relay if I decided to make changes to the SoC setting if my plans changed during a charge.... So instead of cycling the power on and off I decided to add a Normally Closed Momentary Contact Switch to just cycle the Relay.
Wasn't really necessary but was more fun than not doing it once I thought of it... and raising the build price to $33

 

[PCeBiker]

$10 DIY Smart Charger Alternative / Ver. 2.0



$175 Stupid Charger Alternative / Ver. 2.0
180 Watt 3A 60VDC Bench Power Supply

Built like a tank with an old-school transformer.
Weighs in at 4.5 kg

https://www.digikey.ca/en/products/detail/sra-soldering-products/kd6003d/15190003

There's a 300 Watt 5 amp version for $300 CAD
It weighs in at 8 kg

https://www.digikey.ca/en/products/detail/sra-soldering-products/kd6005d/15190006

$110 Stupid Charger Alternative / Ver. 1.0
300 Watt 5A 60VDC Bench Power Supply

Cheap Chinese piece of crap that lasted a year.

Weighed in at 1.15 kg

 

[il Munduato]

I do have a 60v/5A desktop power supply... but mostly use it for testing. I have used it a handful of times to charge but find it a bit cumbersome. Settings can drift over days so you should double check all before each charge. Since I typically start early in the morning before coffee, its back on the test bench where it belongs. I did make up a set of test leads so I can run it thru the DIY box, but they probably won't see much use.
Over time I've accumulated a pair of 2a, and then a 4a and 5a charger and I can easily swap out to run them thru the DIY box.
That said I'm almost never in a rush, so the 2a is in place 99.9% of the time.
Y CC CV MV

 

[PCeBiker]

I just realized that I have the same power meter that you've got, but I intend to mount it on my e-bike to keep track of the battery capacity as the battery is being used.


I ended up using my bench power supply to charge my batteries and just set it to 52 volts.
It's a round number at about 80% charge and a nice round 4 volts per cell group in the battery.

I also have 3 other battery chargers (two 3 amp chargers and a 4 amp charger).

I turned down the one 3 amp charger as far as it will go, so it switches to CV at ~53 volts now.
So now I charge both batteries at the same time after a ride.

, . Settings can drift over days so you should double check all before each charge. Since I typically start early in the morning before coffee, its back on the test bench where it belongs.

I have gotten used to setting my voltage and current at every charge, and in the morning before my ride, I will top up the main battery to 54.6 V to get my maximum range.

I used to top up both batteries before my ride, but I found myself swapping batteries just to reduce the voltage in the second battery if I ended up not needing it.


I figure having the Watt Hour Meter on my e-bike is the best place to put it because I don't really care what goes into the battery, I want to know how much I get back out.

Things like temperature and how much power you're pulling from the battery can have a Huge impact on the battery's capacity and range, and I want to see that as it's happening while I'm riding.

I could put timers on my charger and bench power supply to kinda make them automatic, but I just keep an eye on them and I don't have to worry about overcharging the batteries with a maximum voltage of ~52.5 V.

I would have to have a pretty crappy, unbalanced battery, with a useless BMS to become dangerous with 52.5 V at less than 3 amps applied to it, when all three of my batteries have a 30 amp BMS.

 

[Gionnirocket]

I would have to have a pretty crappy, unbalanced battery, with a useless BMS to become dangerous with 52.5 V at less than 3 amps applied to it, when all three of my batteries have a 30 amp BMS.

?

 

[PCeBiker]

?

What I was getting at, is that if a battery is going to burst into flames while charging at 1 amp (which apparently has happened), then there is no way to use that battery safely regardless of what you do.

The only way I can see that battery going into flames is to have many cell groups out of balance, (with partial cell group voltage), so the few remaining fully charged cell groups get overcharged when the battery's total voltage reaches 54.6 volts?
And the battery wouldn't have a balancing BMS either?

I'm feeling quite safe charging my batteries to 52-53 volts knowing that I have quality brand name cells and a proper (although not a balancing) BMS inside.

 

[Gionnirocket]

What I was getting at, is that if a battery is going to burst into flames while charging at 1 amp (which apparently has happened), then there is no way to use that battery safely regardless of what you do.

The only way I can see that battery going into flames is to have many cell groups out of balance, (with partial cell group voltage), so the few remaining fully charged cell groups get overcharged when the battery's total voltage reaches 54.6 volts?
And the battery wouldn't have a balancing BMS either?

I'm feeling quite safe charging my batteries to 52-53 volts knowing that I have quality brand name cells and a proper (although not a balancing) BMS inside.

Well it's impossible to know the tech built into a BMS without a spec sheet or dissection.
And yes a bad battery is a bad battery and difficult to protect if not impossible.
That said there is more than one way a battery can fail. But even the simplest of BMS I have seen don't terminate charging at full pack voltage but when the first cell reaches 4.2v. The charger is what should shut down at full pack voltage.
That, that said... If the BMS fails to terminate charging when the first cell reaches 4.2v... Then yes

 

[Chargeride]

Its simple really, no amount of quality control can eliminate risk
Lithium ebike batteries have hundreds, sometimes KWs of energy stored chemically.
The two highly reactive compounds are seperated by al you minium foil.
The fire is self sustaining, it can burn underwater, produces noxious and highly explosive gas and the fire temperature is vastly higher than petroleum.
The Californian battery facilty caught fire again, many weeks later..by itself.

You just deal with it, but as EVs start to age and people start home fixing battery packs and buying back street ones with big dents or holes in them, then things are going to get very legal indeed.
Trusk will have to hire 100,000 battery inspectors.

 

[PCeBiker]

But even the simplest of BMS I have seen don't terminate charging at full pack voltage but when the first cell reaches 4.2v.

Ohh !!!
I didn't know that !!

I thought the BMS just shut down the battery when any cell group reaches about 3 volts.

Well it's impossible to know the tech built into a BMS without a spec sheet or dissection.

I don't know what BMS I've got inside my batteries because they're glued shut, and I'm not going to tear into my brand new $840 battery to investigate,..

You just deal with it,

That's what I want to do.
I trust that my battery is built properly and if I start getting depleted capacity, I'm just going to figure that my entire battery, and all the cells are equally aged and not out of balance.

but as EVs start to age and people start home fixing battery packs and buying back street ones with big dents or holes in them, then things are going to get very legal indeed.

I've got everything I need to balance my cell groups manually.
Hopefully I won't bother trying to get to the BMS when my battery is worn out in 5-10 years, and just replace the battery.

All my batteries have quality cells that should all wear out evenly so cell balancing wouldn't accomplish anything.

 

[Gionnirocket]

I'll add that a rudimentary test to know if your pack is out of ballance is to slow charge it to 100%.
If a 48v pack keeps shutting down before it reaches 54.6v...then most likely there's a cell reaching 4.2v before the others.
Could be a bad cell (cells) way in front or cell (cells) lagging.