Maximum safe charger a/h output for lithium-ion batteries ?

[eHomer]

Sorry, yet another question !

When buying a charger for a lithium-ion battery, what needs to be considered about the ampere hours output current ?

The charger supplied with my 36volt 10ah Li-ion battery was an MCR0236L, marked as 42v 2a.

I've now obtained a second, identical battery, and I would like to buy another charger, as a spare, and also to enable me to charge both batteries at the same time, if need be.

It would seem to be best to go for one of the higher a/h rate chargers, to enable faster charging.

Am I wrong there though ? Does the BMS built into the battery control things anyway ? Would a 4ah charger do it twice as fast as a 2ah, and would that be detrimental to the battery. I know these things are important with SLA batteries, but lithium are still a mystery to me.

I'd like to get the fastest charger possible that will not be detrimental to the life of the battery.

 

[morphix]

Someone will correct me if I'm wrong, but I always thought the BMS controlled the charging of the cells and it doesn't really matter what rated charger you use (providing it can supply sufficient current of course and the right voltage)..the BMS will always regulate how much juice the batteries get and so charging will take the same amount of time? I think the key thing is to make sure the battery charger is compatible with your battery/BMS.

e-Bike batteries are far more "intelligent" with the BMS than dumb Lead Acid, Ni-MH, Ni-Cad etc where adding more power from the charger speeds up charging time.

 

[Deleted member 4366]

There's lots of different types of cells in different lithium batteries. Some types can be charged quickly, but most like to be charged slowly. A safe charging rate is 0.2C, which means 0.2 x your battery aH rating, i.e 2 amps for a 10aH battery, 4 amps for a 20aH battery. You can go a bit higher without too much damage, but you need to know exactly what cells are on your battery if you wanted to double it.

If it were me, I'd get another 2A charger, which will allow you to charge both at the same time, and if one packs up, you still have another.

It's not a good idea to charge two batteries from one charger at a higher rate because one battery could be charged before the other, so its BMS switches off and then you get the full charge rate going in to the other.

 

[eHomer]

Many thanks....

I'll take the advice and just get another 2ah charger then.

This looks about the cheapest £17.39, including p&p, hopefully below the threshold for tax and customs ?
It looks like it even has the correct size dv coax power plug...

24V/2A ,36V/2A ,48V/2A E - Bike E - Lithium Battery Charger | eBay

 

[Deleted member 4366]

The BMSBattery ones are quite good. You have to go all the way to checkout to see what the postage is. It works out cheaper if you buy other things at the same time. These chargers are adjustable for voltage and current, so, although they're set when you get them, you can change them later if you get a new/different battery.
Alloy Shell 120W LiFePo4/Li-Ion/Lead Acid Battery EBike Charger - BMSBATTERY

 

[eHomer]

I agree the BMS ones look a much better spec, metal cased and with reset-able output voltage, but when
I took the order process trough to the carriage cost, the cheapest option was £24 via EUEXP, taking the total price up to £35. Maybe that would also e more likely to attract customs and vat as well.

The ebay option, item number 110978619242 is £17.39, inclusive of shipping. Maybe safer with customs and taxes ?

 

[morphix]

I agree the BMS ones look a much better spec, metal cased and with reset-able output voltage, but when
I took the order process trough to the carriage cost, the cheapest option was £24 via EUEXP, taking the total price up to £35. Maybe that would also e more likely to attract customs and vat as well.

The ebay option, item number 110978619242 is £17.39, inclusive of shipping. Maybe safer with customs and taxes ?

eHomer..BMS Battery... *cough* big time undervalued customs on my latest order of 10 parts, including motor.. Got my FedEx "you owe us" letter...VAT+Duty (just £7!!).. they just put "wheelchair parts..qty 10*$6 = $60" .. you might get lucky if you buy a battery and they do the same for you...would knock that cost right down from the figures I did for you. Maybe ask them?

 

[eHomer]

eHomer..BMS Battery... *cough* big time undervalued customs on my latest order of 10 parts, including motor.. Got my FedEx "you owe us" letter...VAT+Duty (just £7!!).. they just put "wheelchair parts..qty 10*$6 = $60" .. you might get lucky if you buy a battery and they do the same for you...would knock that cost right down from the figures I did for you. Maybe ask them?

? The £24 postage was what BMS calculated for me on their website when I took the charger right through to the ordering stage. So any customs or tax hits would be on top of that.

£11 for the item and then £24 for the net postage makes the ebay item 110978619242 at £17.39 half the price at least.

 

[Old_Dave]

BMS's postage charges spoils it for smaller value orders, even the rates for china post are excessive ..


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[piotrmacheta]

I have the ezee kit and the original charger was a 2A (for 10Ah battery) and the new one is 4A. It charges the battery twice as fast so it's not governed by the BMS of the battery. Not sure if it shortens the life of the battery though but I've been using it for nearly a year and so far so good. I'd say it's very useful to charge batteries quicker so I'd get the more powerful one.

 

[Deleted member 4366]

I have the ezee kit and the original charger was a 2A (for 10Ah battery) and the new one is 4A. It charges the battery twice as fast so it's not governed by the BMS of the battery. Not sure if it shortens the life of the battery though but I've been using it for nearly a year and so far so good. I'd say it's very useful to charge batteries quicker so I'd get the more powerful one.

How big is your battery?

If I've understood it right, the newer Ezee batteries have higher charge/discharge rate cells in them, so they can use a higher rate charger (4 amps for 10aH). I'm not sure of the charge rate for the older batteries. You may be still OK. Perhaps Cyclezee can confirm, but I wouldn't recommend charging your average 8aH to 10aH ebike battery at 4 amps - just in case anybody else gets the idea that it's OK.

 

[Gens Ace battery]

yes. d8veh's response is correct... 0.2C current charging is recommend. It will be good for the battery.If you want the fast charging. you can choose the high current charger, such as 4A,5A, even 10A for it.
4A is OK, but 5A and 10A charger is not recommended. it is not good for the battery, it will affect battery's cycle life. and it can not get fully charged by big current charger. maybe 90%-95% more or less...just like the water faucet for a cup of water...

Benson
Gens Ace battery

 

[jackhandy]

I like the illustration of a water tap on full bore .....

Where does the electrickery that spills over the sides of the nearly full battery go?

 

[Old_Dave]

Where does the electrickery that spills over the sides of the nearly full battery go?

Through the return path and back to the power station to be sold again to someone else

 

[piotrmacheta]

My ezee battery is a 10Ah one from 2009 I think. And there's me thinking the BMS ensures that the max voltage doesn't exceed 4.2V and ballances the cells.

 

[Synthman]

I use a 4a HP charger to charge my 10ah batteries. My old Phylion would take over 4 hours and 40 minutes to charge with a 1.8a charger (from empty), but around 3 hours with the 4a charger. It didn't reduce the charge time by 50%, more like 33%. My newer battery is more interesting, it takes the same time to charge on the 4a charger as the Phylion did with the 1.8a one!

I have a power monitor on the socket the charger plugs in, and it seems to me that the higher amperage is only utilised earlier on during the charging process when the battery is near empty. The power consumption gradually falls, from 200w to 110w, then as the battery reaches 41v, it drops down to 42w and stays there until near the end of the charge, where it reduces to 15w and the green light comes on.

The BMS from my old battery balanced the cells, the one in the new battery doesn't. I think they control the charge current though.