Search for ebike charger

[Martin Rogers]

Hello All,
This is my first post on the Forum, hope someone can help to point me in the right direction.
I have built a 36volt 10s 15Ah battery using 18650 cells.
I am after sourcing a charger that has the following features
1) auto shut off once charged
2) selectable max voltage so to charge to switchable 80 / 90 / 100% capacity ( to increase battery life )
3) about a 2 to 4 amp charge rate
4)reasonable quality at a sensible price!
Sounds a bit geeky but I am an electrician
Can't seem to find such a thing apart from Luna Cycles in California, carriage and import costs to the UK aside it is only suitable up to 220 v not the 240volt UK supply .
Anyone know of a item ... or should I get a standard item from eBay and get on with my life
Martin

 

[Woosh]

Sounds a bit geeky but I am an electrician

you can use a volt meter to set a timer.
your charger is probably run of the mill 2A charger. Your battery is a 10AH, your charger will take 5 hours to charge it from flat to full, 30 minutes per volt.
The voltage of a flat battery is 31.5V, a full battery is 41.5V.
Measure your battery's voltage at the output and work out the time it takes to reach the desired voltage.
eg:
your battery shows currently 36.5V (50% full).
you want 80% full = 39.5V
You need 3V = 3 * 30 minutes.

BTW, you should not use a 4A fast charger on ordinary 10AH battery.

 

[awol]

This one is 3a and you can lower the max volts, but if your using a bms then it won't balance properly. There is also 5a 11a 17a versions.
https://www.ebay.co.uk/itm/Precision-Compact-DC-60V-3A-Adjustable-Digital-Switching-Power-Supply-110-220V/141389291960?epid=680554117&hash=item20eb7561b8:g:wWIAAOSwd4tT~V3p

 

[Martin Rogers]

Hi Whoosh and Awol,
Thank you for replies
Whoosh
Had considered the monitoring of voltage then stop charging at a chosen voltage.... but hadn't considered the maths approach ... brilliant.
Good info that 4amps would be to high a charge rate, I have no need for a fast charge anyway.

The battery is 15 ah with BMS

Awol
That power supply looks great ! with the adjustable voltage and current facility I can use it for applications like drill battery charging and other projects.

Why would the battery not balance correctly with BMS?
Is that only if max charger voltage is set to lower than the 42volts ?

 

[Woosh]

Why would the battery not balance correctly with BMS?

during charging, the same current goes through all the 10 blocks of cells, balancing cannot be done.
At the end of charging (when the LED goes green), the BMS switches off the charging current and balances your battery by topping weak blocks with a small current.

If you have 15AH and 2A charger, each Volt takes 45 minutes.

 

[awol]

Sounds a bit geeky but I am an electrician

If you like geeky, then replace your bms with this one, it's amazing. It lets you set the max voltage where you want the balancing done (maybe a bit lower), set the cutoff where you want (maybe a bit higher) etc to get maximum life out of your cells, live bluetooth connection to the phone app to monitor every cell and use the power supply from above with it.
https://www.speedict.com/

 

[Martin Rogers]

Good Morning,

That BMS is brill ... a real big move on!

I'm think I'll go for a " standard" charging method to get me rolling .. and move into the geeky stuff in the future

I will send for that PSU as it will have multi uses for me.

Thank you both for for such interesting and helpful info.

Hi Whoosh
I'm guessing that Whoosh sell chargers separately?
If so please send the reference for a suitable 2amp intellegent charger for 36volt 15ah battery with BMS
( 50 cell INR18650-30 10s) with 3 pin XLR connection.
Thanks

 

[Woosh]

Hi Whoosh
I'm guessing that Whoosh sell chargers separately?
If so please send the reference for a suitable 2amp intellegent charger for 36volt 15ah battery with BMS
( 50 cell INR18650-30 10s) with 3 pin XLR connection.

that's our charger for the Gale. Made by SANS.
£29 inc. post and packing.

 

[mike killay]

during charging, the same current goes through all the 10 blocks of cells, balancing cannot be done.
At the end of charging (when the LED goes green), the BMS switches off the charging current and balances your battery by topping weak blocks with a small current.

If you have 15AH and 2A charger, each Volt takes 45 minutes.

Do you mean each Amp?

 

[Woosh]

Do you mean each Amp?

No, each Volt that you see when measuring the voltage of the battery.
Between flat (31.5V) and full (41.5V), you see 10V difference. Each Volt is 10% of the battery capacity (near enough anyway).
That's how the battery meters work, if it has 5 segments, each segment is set to 2V. If it has 4 segments/LEDs, each segment/LED is 2.5V drop.
Your typical charger gives 2A output, the output voltage rises as the battery gets fuller, but the current remains steady at 2A until the battery is practically full. So the charger puts 2AH into your battery. If you have 10AH, it will take 5 hours, if you have 15AH, it will take 7.5 hours to charge from flat to full. So for 10% charge, that will be 5 hours/10 for a 10AH battery, 30 minutes, for a 15AH, that will be 7.5 hours/10, 45 minutes.
You'll get used to know how full your battery is by checking the output voltage, it'll make sense in no time. For wintering the battery, charge it to 75%.

 

[Deleted member 4366]

If you want to charge to anything less than 100% (42.0v), you need a special BMS, like the Speedict one. Without that, you can do occasional lower charges, but your battery won't balance if you do it regularly. Nearly all standard BMSs balance by draining down the high cells via bleed resistors that only open when the cell is above around 4.15v/4.17v.

 

[mike killay]

No, each Volt that you see when measuring the voltage of the battery.
Between flat (31.5V) and full (41.5V), you see 10V difference. Each Volt is 10% of the battery capacity (near enough anyway).
That's how the battery meters work, if it has 5 segments, each segment is set to 2V. If it has 4 segments/LEDs, each segment/LED is 2.5V drop.
Your typical charger gives 2A output, the output voltage rises as the battery gets fuller, but the current remains steady at 2A until the battery is practically full. So the charger puts 2AH into your battery. If you have 10AH, it will take 5 hours, if you have 15AH, it will take 7.5 hours to charge from flat to full. So for 10% charge, that will be 5 hours/10 for a 10AH battery, 30 minutes, for a 15AH, that will be 7.5 hours/10, 45 minutes.
You'll get used to know how full your battery is by checking the output voltage, it'll make sense in no time. For wintering the battery, charge it to 75%.

Thanks.
I was multiplying 45 minutes by 36 volts!