notions to consider choosing charger, noob

IHI everyone
did you have a good day?
I have a need for knoledge and clarity to choose a charger
I will put 48 v battery together and have to choose a bsm charger and buck converter 48 to 24v(ideally 25 26v)
I have sony vtc4 see spec at the end . i still have the choice to go for 12s or 13 s . probably 5p and and addon pack of 3more cell parallel. the wall plug is north american 110v.

I have read some stuff . I am still a noob

i will have a 48v batterie
here are some questions

1 why are sellers on alibaba asking how many AMP hour th battery have? i mean whether i have 13 s 5p or 13s 8p the charger should still work no?

2 i noticed that there are like 2 voltages on charger. like its name 48v for example and in the spec thy put higher voltage like fifty something...? what do i need to check and be aware of?

3 how to select the out put current of the current? I read on luna cycle that the have a kind of charger that charges at 3A and 5A you can chose. is this a necessity? cause they dont have 48v charger (they only have a mini). so i have to learn? what there is to learn to choose a charger. I already know that the more watt a charger gives the quicker the charge will be done . that is about it. i remember reading that charging a battery to quickly is not good.



I have sony vtc4 see spec at the end .

Tx for helping me geting better

Charge your Sony VTC4 only on 18650 chargers. Smart chargers are highly recommended.

Specifications:

Rated capacity: 2100mAh (high drain)
Minimum capacity: 2000mAh
Initial discharging current: 15A
Maximum continuous charging current: 6.5A
Maximum continuous discharging current: 30A
Voltage: 3.8V
Nominal operating voltage: 3.2V
Maximum charge voltage: 4.2V
Discharge cut-off voltage: 2.5V
Dimensions: 65.0mm (L) x 18.2mm (D)

A 48v 13S pack has a fully charged voltage of 54.6V (13x4.2V), because of this charges often quote 2 voltages, the nominal voltage of the pack the charger supports and the voltage it actually charges the pack too.

The capacity of your pack is important for a couple of reasons.
1) The smaller the capacity the lower the supported charge current. (Generally, need to know the cell spec to be sure)
2) If you have a larger pack you will want a higher current charger to avoid painfully long charge times. ( A 20Ah pack could take 10 hours+ to charge with a 2A charger...) The seller is probably working out if you are after the right charger for your application. You could have a 1P pack with cells that are rated for 2A charging current and are asking for a 5A charger...

You need to choose a charger that is going to meet all your requirements. How long are you willing to wait for it to charge? What max charge current can your pack take? What is your budget for a charger? Are you willing to shorten the packs life by charging it harder?

You need to balance all these things out. Your pack should take a very high charge current so I don't thing that is an issue. It's only going to be a 10Ah pack though. If you get a 5A charger then it will charge in around 2 hours give or take. If you get a 2A it will take more like 5-6 hours. If you get a 12A charger then it should be done in under an hour.

You can get adjustable ones as well so you can charge it slowly most of the time to limit stress on the pack but charge it harder when you don't have time to wait. They will cost more though.

why bother with a 48V battery and a converter when you can just make a 7S battery? a 7S almost perfectly matches the voltage range of 24V lead acid.

HI lion man and flippy thx for your attention, feel free to correct me if i do assumptions that are incorrect in my stategies; electronic is new somewhat for me. and by the way. my cells are not soldered yet so i am still free to choose config.


iwould really like to have a charger that has an ajustable current because sometimes i will want to charge it in around 2 hours and sometimes i will have plenty of time.Do you think there is also a charger that can have its voltage adjusted on top of adjustable current. also i would like it to stop automatically so that it does not go overcharging. If possible i would like to alsot be able to have a way to program it to someting charge to 90 % 80% 100% cause i read it is not good to always full charge for lifespan of cells. luna blue (3a and 5aoptions 80 90 100%options)are out of stocjk for 48v buy maybe there are other choices other brand...I will have to carry it in my luggage so the weight is important . if it is not to complicated, i m also open to buy 2 chargers smaller if it lowers the price or the weight. i read somewhere a guy uses 2 charger in series or parallel (not sure)

i forgot what is the mathematic to calcul the capacity. is it nb of cell in parallel x capacity of one cell?in my case will the capacity always be 2.1amp h per cel? vtc4

The tricky part is this : I will want my battery to be modulable (if it is realistic)in a way that i can use a light battery 48v for short ebike rides like 13 s 3p and when i go for longer ride i thouth of adding anderson connectors at the end of each of the 13 paralelle copper stips to add a 13s 5p in parallel so that the total battery will be 13s 8p. hence longer ebike ride. I would use a bms maybe this one from bmsbatt that gives the futur possiblility to use from 10s to 15s.is it ok to leave empty slots? Also it is written 60a on the page but i dont know if it is a constant value or just peak a 60a. i hope it is a working 60a value with peak over 60a
https://bmsbattery.com/bmspcm/833-smart-bms-10s13s-60a-with-blue-tooth-android-or-ios-app.html


The other tricky part is that i will use those cells to power an electric wheelchair .(this electric wheel chair(quantum 6000z from Pride) normally uses 2 x 12v gel battery in serie. i contacted the manifacturer and he told me the electric wheel chair usually asks for 25 to 26 v . he also said that24 is ok but under 23.75 v it would not work and over 26.5v it will not work. As for the amps it think it is not a probleme because he says it usually draws a 30 amp on normal conditions and has a fuse at 70 amp so will never go ver 70 amps.

so i thought of using a down step buck converter 48 to 24volt to only have a battery in 2 parts (13s 3p and 13s 5p) and still be able to use the wheel chair at 24v. Thi idea of flippy is one interesting. Im inclined to choose it cause im on a budjet and i can desolder easily i could separate the battery in four .7s 3p, 6s 3p, 7s5p , 6s 3p mudulable with anderson connectors. concreatly when i have to use the wheelchair i would unplug the anderson connector and only use the 7s 5p or both 7s module in paralle for 7s 8p leaving the two 6s modules out. i see two obstacles though(maybe more im not aware of) .
alpha :;would i be able to use the same bms (link above) or have to purchase more bms? since in the link they say from 10s to 15s i dont know if the bms would do for 7s.
beta:; how complicated would it be to charge those 7s battery (when using wheelchair) and the complete 13s for ebike? would that require multiple chargers? if so i need to compare if it is less costly to just buy a buck converter or and additional bms and additionnal charger. so far i found a buck 48 to 24v 63amp at 200usd shipped or 138usd for a 50A(second link ebay. info at bottom.

so i guess I have the questions is the text above and to choose if i go with a buck converter or not and what charger would suits me in those situation. I think 150usd is possible for my budjet maybe more cause i would really like and adjustable one . would this bms work for 7s ?it is written lincm means lion nickel cadmium? ... isit goog for vtc4 ?
https://www.aliexpress.com/item/7S-25A-35A-45A-60A-PCM-PCB-BMS-for-24V-lithium-18650-battery-pack-for-electric/32845863107.html?spm=2114.search0604.3.26.41942af938GFg1&ws_ab_test=searchweb0_0,searchweb201602_1_10152_10151_10065_10344_10068_10130_10342_10547_10343_5722611_10340_10548_10341_10696_5722911_5722811_10084_5722711_10083_10618_10139_10307_10059_306_100031_10103_10624_10623_10622_10621_10620_5722511,searchweb201603_12,ppcSwitch_5&algo_expid=e18ac1c8-61b7-48b2-acca-8e603667ef97-4&algo_pvid=e18ac1c8-61b7-48b2-acca-8e603667ef97&transAbTest=ae803_2&priceBeautifyAB=0
--------
or
---
https://www.aliexpress.com/item/7S-60A-Li-ion-24v-Diy-circuit-board-with-balance-bms-pcm-for-electric-bike-vehicles/32856208162.html?spm=2114.search0604.3.39.20a73454HZlW7z&ws_ab_test=searchweb0_0,searchweb201602_1_10152_10151_10065_10344_10068_10130_10342_10547_10343_5722611_10340_10548_10341_10696_5722911_5722811_10084_5722711_10083_10618_10139_10307_10059_306_100031_10103_10624_10623_10622_10621_10620_5722511,searchweb201603_12,ppcSwitch_5&algo_expid=a10f3386-6d69-4a9b-9379-5486357e80ae-6&algo_pvid=a10f3386-6d69-4a9b-9379-5486357e80ae&transAbTest=ae803_2&priceBeautifyAB=0
thx for sharing your thougths

If i can choose the amps adjustable charger i beleive it solves the expansion pack . i i get ans adjustable amps 24 volt i couls charge the 7s whell chair battery and if i can put another 24 volt adjustable in serie(or paralele not sure) i could use both charger to charge the battery in ebaike mode 48v. is this realistic? can you have 2 adjstable charger in series to charge one big 48volt battery?

200 usd 1 unit 48V-24V 63A DC DC Converter
-DD48S2463) 48VDC TO 24VDC 63A DC DC Converter

1. Input Rated Voltage: 48vdc

2. Input Voltage Range: 35-60vdc

3. Output Voltage: 24vdc+/-1%

4. Output Current: 63A

5. Output power: 1500W

6. Size: 220*127*63mm

7. Weight: 2.5kg

Qty: 1 unit

Unit Price: 138.0USD/PCS EXW

Shipping cost: 59.00USD from China to Canada via DHL

Shipping cost: 55.00USD from China to Canada via FedEx

Lead time: 3-7 working days after confirm order and payment
-----------------------
one 50A 48 to 24v 138usd
https://www.ebay.com/itm/DC48V-To-DC24V-50A-1200W-Step-Down-Power-Supply-Converter-Regulator-Module-New/192499600409?hash=item2cd1decc19:m:mqCxkGRtA11hY77PfnAUzSw

My take on your specific needs.

3p will be discharging your pack at too high a rate in any case, too small a battery for a bike. To make your battery last all rides need to be as low a discharge rate as possible. And shallower discharges are good too, so you want to run the full size 48v pack all the time, till it gets so big and heavy that becomes a problem. Up to 1000 watt hours total, is still light enough to carry on most bikes. 8 p might be too big to carry all the time, but 5p would work, and adding on 3p sometimes.

It might work for you to make two 7s packs, and then run 7s on the chair, but connect both in series to run the bike. This would allow you to use one, or even two 8s RC chargers instead of a 48v charger. These chargers can adjust voltage and rate of charge, so you can easily do 4v per cell charge or a 4.2v charge, and choose to balance charge or not, as needed, on each level of charge. The 7s packs will need a jst balance plug to use the balancing functions of the charger.

In short, though a bit more complicated to use daily, the RC charger method will allow you a maximum flexibility when you want that.

While discharging such a pack, you don't really need a bms, since you do get balancing functions from the charger. You will however, need to watch depth of discharge. Easy on the short rides of course, since you will never reach the end on the short rides. On longer rides, just watching the total voltage will be good enough for knowing when to start monitoring each cell. Only on the last part of the ride is this needed, and you can do it with two inexpensive low voltage alarms. They simply plug into those jst balance plugs. Use the alarms only when you know you are low, otherwise leave them off the packs so they don't overdischarge a cell, or unbalance the pack overnight.


FWIW, your bike will run fine on 14s, but a bit faster than on 13s, so no problems there.

dogman dan said:

It might work for you to make two 7s packs, and then run 7s on the chair, but connect both in series to run the bike. This would allow you to use one, or even two 8s RC chargers instead of a 48v charger. These chargers can adjust voltage and rate of charge, so you can easily do 4v per cell charge or a 4.2v charge, and choose to balance charge or not, as needed, on each level of charge. The 7s packs will need a jst balance plug to use the balancing functions of the charger.

Click to expand...

Hi

for ebike, i feel i d like to have a bms on battery even if i have to solder anderson connector to remove it easiily because sometimes my head is busy and i would on ebike forget to get the alarm off. On the wheelchair, i would be ok to use the alarm without bms if the alarm is reliable.

in ebike mode, could i use 2 rc charger to charge the battery with the 14 BMS? two rc charger one for each 7s ? to rc charger in series for 14s?

for the wheel chair, i have plenty of time to charge. but on bike , in less than 3 hours would be good. would it be faster to charge 2 x (25.9v) 7s 8p with rc charger of to charge only one battery 51.8V with one charger? So far i found this two charger for 14s

https://www.aliexpress.com/store/product/58-8V-4-5A-5A-5-5A-6A-6-5A-7A-7-5A-Lithium-Battery-Charger/2217102_32792292319.html?spm=2114.12010610.8148356.3.42083f85AzkibA
https://www.aliexpress.com/store/product/Intelligent-58-8V-4A-Lithium-Battery-Charger-for-Electric-Tool-Robot-Electric-Car-Li-on-Battery/2217102_32814642478.html?spm=2114.12010610.8148356.1.42083f85mPf2Wd


I took a look on aliexpress ebay and hobbyking but it seems 7s is rarely stated and the price seems high. Could you put a couple of choices in links so that i can read the spec of the kind of rc charger you are thinking about?


also is it a misfrap to have written 8s charger? did you mean 7srccharger?

one charger is faster and cheaper.

also: you can put 2 low power chargers parralel in order to get fast charging. so you can still use the mean well HLS/ELG route. just be REALLY careful with the voltages you set.

I would be hesitant to build a 'modular' pack. It's better to keep cells that are being used in series permanently grouped so they continue to to maintain similar capacity and internal resistances aver their life span. This will lead to the best performance and safest operation of the pack.

I would build 2 packs. One for the bike and one for the chair, eached specced appropriately for the application. You could also build one 48v pack and use a buck converter to bring it down to the voltage the chair needs. You'll lose about 10% capacity most likely in the conversion.

If you want the bees knees of variable chargers then look at the satiator. It's expensive but super high quality. The only other options are the Luna charger, a ghetto charger made from a PSU and a CCCV DC converter or maybe a meanwell LED driver with variable CC and CV.

lionman said:

I would be hesitant to build a 'modular' pack. It's better to keep cells that are being used in series permanently grouped so they continue to to maintain similar capacity and internal resistances aver their life span. This will lead to the best performance and safest operation of the pack.

if i use 2 x 7s in wheel chair,wouldn t the battery evolve the same ? like 2 x 24 v in parallele would put the same amount of cycle throug their life?


If you want the bees knees of variable chargers then look at the satiator. It's expensive but super high quality. The only other options are the Luna charger, a ghetto charger made from a PSU and a CCCV DC converter or maybe a meanwell LED driver with variable CC and CV.

Click to expand...

could any one put a link of one of those rc charger dog man was refering to " These chargers can adjust voltage and rate of charge, so you can easily do 4v per cell charge or a 4.2v charge, and choose to balance charge or not, as needed, on each level of charge. The 7s packs will need a jst balance plug to use the balancing functions of the charger. "

Also if an experimented one could tell me by reading descrip of the item below if there is a way for me to use this charger and only get a 80 or 90 % charging

https://www.aliexpress.com/item/54-6V-4A-Smart-Lithium-Battery-Charger-For-48V-Electric-Scooter-Bicycle-ebike-Wheelchair-Li-ion/32708539733.html?spm=2114.10010108.1000013.3.596c464eOhZSSi&scm=1007.13339.99734.0&scm_id=1007.13339.99734.0&scm-url=1007.13339.99734.0&pvid=b6b59155-4fbd-49df-82b2-e633b0ca5062&_t=pvid:b6b59155-4fbd-49df-82b2-e633b0ca5062,scm-url:1007.13339.99734.0

want to build said:

lionman said:

I would be hesitant to build a 'modular' pack. It's better to keep cells that are being used in series permanently grouped so they continue to to maintain similar capacity and internal resistances aver their life span. This will lead to the best performance and safest operation of the pack.

if i use 2 x 7s in wheel chair,wouldn t the battery evolve the same ? like 2 x 24 v in parallele would put the same amount of cycle throug their life?


If you want the bees knees of variable chargers then look at the satiator. It's expensive but super high quality. The only other options are the Luna charger, a ghetto charger made from a PSU and a CCCV DC converter or maybe a meanwell LED driver with variable CC and CV.

Click to expand...

could any one put a link of one of those rc charger dog man was refering to " These chargers can adjust voltage and rate of charge, so you can easily do 4v per cell charge or a 4.2v charge, and choose to balance charge or not, as needed, on each level of charge. The 7s packs will need a jst balance plug to use the balancing functions of the charger. "

Also if an experimented one could tell me by reading descrip of the item below if there is a way for me to use this charger and only get a 80 or 90 % charging

https://www.aliexpress.com/item/54-6V-4A-Smart-Lithium-Battery-Charger-For-48V-Electric-Scooter-Bicycle-ebike-Wheelchair-Li-ion/32708539733.html?spm=2114.10010108.1000013.3.596c464eOhZSSi&scm=1007.13339.99734.0&scm_id=1007.13339.99734.0&scm-url=1007.13339.99734.0&pvid=b6b59155-4fbd-49df-82b2-e633b0ca5062&_t=pvid:b6b59155-4fbd-49df-82b2-e633b0ca5062,scm-url:1007.13339.99734.0

Click to expand...

7S charger with those features won't be very cheap. 6S chargers are a lot more common.

iSDT T8 is one option. Its about 100USD but you will also need a powerful PSU (40V 1000w for maximum performance) as it only supports DC input. It supports up to 8S charging and can charge 2 packs at once at 500w per pack.

SKYRC Ultimate Duo 400W is another option. It takes AC input and can charge 2 7S packs simultaneously. They are about 190USD.

The charger you linked is for charging a 13s pack to 4.2V per cell. It is not adjustable in anyway.

with a non adjustable battery charger, is it reallly bad to always have to do a full charge a t 4.2v or it is still fine . How dramatic would the liife span be shortened? i would at least use a bms to low cut off

want to build said:

with a non adjustable battery charger, is it reallly bad to always have to do a full charge a t 4.2v or it is still fine . How dramatic would the liife span be shortened? i would at least use a bms to low cut off

Click to expand...

I think generally if you charge to 90% and only discharge to 10% you can get about twice the cycles out of a pack.

By buying a pack about 20% bigger than you need you get double the value.

lionman said:

By buying a pack about 20% bigger than you need you get double the value.

Click to expand...

hum that is weel thought!

could i like use a 54.6v(13s) charger on a 14 s?
would it be safe? with 14s (normally 58.8v) if i charge with a 13 s charger it would equal 54.6 divided buy 14 =3.9v
idont mind loosing 1cell speed.

You can, but 3.9v per cell is quite a low charge. Depending on the cells being used it's only around the 70% SoC range.

Its also a good idea to charge to 4.2v periodically to balance the cells as most BMS only top balance, that is, only balance when the highest voltage parallel group reaches 4.2v