Adjustable 13S Charger

flyinbrick

100 mW
Joined
Apr 4, 2015
Messages
46
Location
Fremont CA USA
I'm looking for another charger for my Izip E3 Peak. It's basically a 48V Li-ion bottle battery with BMS. Interestingly, it is the same exact plastic case charger that Paul at EM3EV sells with his bottle batteries (with a different plug) and are adjustable via a pot inside to about 53.6V min, a bit above 90% capacity which is where I want it. Anyway, instead of shelling out $70 for an Izip charger or $50 for EM3EV charger, I was wondering if this cheap power supply would work. I could get a Meanwell, but this already has nice digital displays and could double as a bench power supply. Will it work?
 
dnmun said:
if you do not charge a battery to full charge then it will not balance under the BMS and it will go rapidly outa balance and be useless.

So what's the best protocol to use the middle 90% in order to maximize battery life? Should I do a full charge, say, every 10 charges or something for balancing?
 
at least. charging to full charge does not affect cycle life. leaving the battery fully charged for long periods of time does.

it is the length of time, length of time, length of time, that the cell is held at full charge that affects cycle life. not final voltage.
 
I see. What length of time does it start to become significant? An hour, a day, a week, a month?

Back to the original post, will a cheap switching power supply like the one I linked to above charge these batteries? The only problem I can think of is that when I set it to fully charge at 54.6V, it won't cut the current at some low current cutoff like a real charger. But I figure maybe I can set the final voltage a tad lower, like 54.5V which brings up another question: at what voltage does the BMS begins to balance? A bench power supply appeals to me because I can, say, do a 90% charge for standby, then dial it up and do a full charge before a ride. My batteries may go weeks between discharges when I'm busy.

Another question that I haven't been able to find an answer for: With my 13S charger set to 54.6V, instead of turning down the trim pot for a lower set point, can I simply build an adapter to drop the voltage down - like put two diodes in series or some sort of voltage divider?? That way, I can achieve the same goal of choosing 90% or 100% charge without having to adjust the trim pot. The chargers I have are only 2A btw.
 
dnmun said:
a power supply will not function as a charger because it does not have a CC mode. it has only a CV mode.

Did you notice that I linked to a bench power supply? I think some (I have many at work) have adjustable current set points. For example, if you set 10V and 1A on a 5 ohm load, the power supply will limit itself to 5V until the load increases or the voltage set point decreases. This seems to be well documented on ES. The power supply I linked to appears to have CC mode as well: "The output current is between 0 and nominal value continuously adjustable."
 
dnmun said:
at least. charging to full charge does not affect cycle life. leaving the battery fully charged for long periods of time does.

it is the length of time, length of time, length of time, that the cell is held at full charge that affects cycle life. not final voltage.

So at what length of time does a full charge start affecting cycle life? 2 days 3 days a week?
 
dnmun said:
if you do not charge a battery to full charge then it will not balance under the BMS and it will go rapidly outa balance and be useless.

You say this a lot which must come from some particular personal experience, but really only packs made from pretty crumby cells (or packs with poorly designed BMS circuits that drain cells from their sense leads) will rapidly go out of balance and become useless. Almost all commercial ebikes are using reputed quality 18650's and properly matched can do many dozens or 100's of cycles without an appreciable variation in cell balancing. And most modern BMS chips can be set to engage in cell balancing at any voltage based on a maximum cell DeltaV, it's not like they only bleed cells that are >4.2V.

I'm not quite sure what's in the original poster's IZip pack, but you can open the enclosure case and have a look at the label on the cells. It's a modern enough bike that I don't think he'd have any issues at all with routinely charging only to 80 or 90%. Then every 6 months he could leave it on for a few days at 100% to bleed/equalize any high cells if that's how his BMS circuit operates.

but this already has nice digital displays and could double as a bench power supply. Will it work?

It will work for sure. Don't expect a bench power supply at this price point to be reliable or last very long if you use it much, but it's something cheap to get started at least. Usually after going through 2 or 3 budget china power supplies failing most people will see the value in buying proper lab grade gear, and you can sometimes find used Xantrex, Sorensen, HP etc. units on ebay for not much $/watt than the china stuff.
For new bench supplies, the programmable units from ITech are quite a few notches better on the quality spectrum, and they are precise enough that you can count on them for charging and topping up individual cells as well as full packs.
http://www.itechate.com/en/products.jsp?sortid=002
 
i have never seen a BMS that allows you to adjust the balancing voltage down from 4.20V. i did not know that was available on these ebike batteries because i have never seen one.

my experience with building batteries is almost entirely in rebuilding used ping packs into new packs. all of them now are assembled into the 87Ah 24S lifepo4 pack in my car.

i did build another pack for my car, a 21S 44Ah HK lipoy/nanotech pack that had huge balancing problems because of the 1S pouches in the nanotech packs. they could not be balanced with 350mA of balancing current by the time i took the pack apart.

he said he was gonna charge to 54.6V so that is not 90% either. but initially he said his power supply could only be adjusted to 53+V. if that battery has a regular BMS as i am used to seeing then it will not balance because the 3-4 bottom cells drained down by the BMS circuit current will continue to fall farther away from balanced and will have less stored charge than the cells that do not supply the circuit current.

i do agree that brand new cells remain well balanced but i have only had experience with used cells and they have all demanded balancing currents to remain in balance.
 
I'm going to pass on the cheap power supply (thanks Justin) and just go with another charger - I just ordered a KIngpan 48V (56.4V) 2A online from electricmotorsports. So the solution that I've worked out is that I'm going to set my home charger to 90%, but the one at work to 100% since I know I'll have to ride back and, thus, the pack will not stay at 100% very long. Thanks all for you input!
 
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