Question about scooter/hoverboard batteries and charging when there is only discharge connections

[Bonzo Banana]

I've noticed some people have used these lower capacity battery packs for ebikes but curious how charging works on them when there is only discharge connections and no separate charging cable as far as I can tell. Does this mean they automatically have some sort of charging protection on these discharge connections? On standard ebikes with regen you are warned not to operate regen when the battery is fully charged as you could over-charge the battery as there is no over-charge protection on the discharge connections but how does it work with these smaller battery packs? Is the charging protection on the main PCB of the hoverboard/scooter separate to the battery's own BMS? I've seen quite a few people use such battery packs for ebikes and maybe I'm overly cautious but I assume they are just connecting them to standard chargers or are they?

These sort of battery packs are maybe 36V 5.2Ah, 20 18650 cells in series of 10. So in theory should be capable of running standard geared hub motors for a reasonable distance and in fact many new ebikes at the budget end come with similar capacity battery packs perhaps configured as internal tube battery packs etc.

Would it be easy to add a separate charge cable to the BMS and re-tape them up?

A 36V 5.2Ah battery is 187Wh which is exactly the same as a standard Swytch kit although I think there is a newer Swytch kit coming out with even less capacity. In theory 200Wh should give about 20Km range or 13 miles and for a small low torque geared hub motor like Swytch seems to give good results.

 

[Nealh]

They will use a common port BMS which as it says uses the same port for both charge and discharge, one can buy them for ebike batteries as well. Common port charging allow for higher amperage charging as well (if the cells can take it). The incoming current will use a seperate path for charging and mosfets to control the charge, balancing occurs as normal.

If the bms is a fairly decent one it will have over charge,over current,over discharge, heat and short circuit protection.

 

[soundwave]

it is a multi pin connection and has 6 cells in it and a bms

 

[Bonzo Banana]

They will use a common port BMS which as it says uses the same port for both charge and discharge, one can buy them for ebike batteries as well. Common port charging allow for higher amperage charging as well (if the cells can take it). The incoming current will use a seperate path for charging and mosfets to control the charge, balancing occurs as normal.

If the bms is a fairly decent one it will have over charge,over current,over discharge, heat and short circuit protection.

Thats very useful info thanks. So if charging directly with a charger do you simply make a little conversion cable to go to the correct connector plus to plus, negative to negative or is there any significant components on the main PCB of the device that enables this function. Maybe diodes or capacitors or something to smooth the connection. I've never actually seen a charger that comes with the right connector to just plug into one of these battery packs, they always seem to come with a connector that plugs into the device itself i.e. hoverboard or scooter.

 

[Nealh]

With diy batteries one would use the same connector type.
A multi pin battery may be different and a generic charger may not work.

 

[Bonzo Banana]

With diy batteries one would use the same connector type.
A multi pin battery may be different and a generic charger may not work.

As far as I can tell these battery packs typically come with an XT60 connector on their cable so purely plus and minus voltage. Any reason if you have a standard 42V 2A charger not to just cut the cable leading to the current connector and fit on a matching XT60 male and female so the charger can be paired to it without losing the original connector on the charger or is there some circuitry in the charger that needs to be present for charging with a common port BMS? I've never seen a charger labelled as suitable for common port BMS battery packs so dare I assume its the BMS that does all the magic and senses when there is a charger connection. I'm planning to get such parts for a little project and don't want to miss anything important. It's not like you can return stuff to aliexpress.

This is the battery pack I've gone for in the 5.2Ah size it seems to tick all the right boxes for the budget build I'm intending, a poor man's swytch kit;

Liitokala 36V 4.4Ah 5.2Ah 6Ah 6.8Ah 2 wheel electric scooter self balancing 18650 lithium battery pack for Self-balancing Fits - AliExpress 44

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[Nealh]

A two wire generic common port charge/discharge lead won't need a special charger so using a generic 2a one is fine. I would make up/solder a very short charge lead with xt60 male and a connector on the other end to suit the charger, 5.5 x2.1 are one of the most common types used. I don't see the point of compromising an existing charger when a simple interconnecting lead can be made.

One can even buy the correct interconnection lead on any of the major auction sites.

Page Not Found - Aliexpress.com

 

[Nealh]

The only thing wrong with those liitokala's are the cells they can't be genuine or new ones, the price just doesn't add up.
For instance the LG hg2 pack though the specs are correct 20 cells for 6000mah for 10s 2p, £36 quid isn't a price I would jump up esp as the price of a BMS is included.
One simply doesn't pay £1.80 or less for a HG2 cell, something very fishy so must be a rewrap fakes. To buy genuine HG2 cells in the UK ,one cell is £8 if buying 20. If one buys a min of 26 one can get them for a bit over £3 wholesale.

The 5200mah will use a 2600mah cell but the specs don't say which cell or brand is used, from what I can see is this pack is max 10a discharge only and assume it uses a medicre 5a reated cell, probably something like a Sam 26F or china brand cell.
Again one has to consider what one is really paying for, for a tad under £25 but by the time one adds on the vat and possibly other costs they aren't worth buying.

 

[Nealh]

Out of the 4 packs available only one cell is rated for the 20a discharge and that is the so called HG2 pack, the other three are only a max 10a discharge and all will use a 5a cell. Panny ncr18650b are only 5a rated, the risk in useing them is far greater due to the cheap price nature and one can't expect a very good bms inside for the price.
Cheap china packs are known for fake cells.

 

[Bonzo Banana]

A two wire generic common port charge/discharge lead won't need a special charger so using a generic 2a one is fine. I would make up/solder a very short charge lead with xt60 male and a connector on the other end to suit the charger, 5.5 x2.1 are one of the most common types used. I don't see the point of compromising an existing charger when a simple interconnecting lead can be made.

One can even buy the correct interconnection lead on any of the major auction sites.

Page Not Found - Aliexpress.com

I don't consider it compromising the existing charger myself and not keen on inline DC sockets and as I already have XT60 male and female connectors and shrink wrap and this would now be the main use of this charger it seems logical to configure it as default for this use so the adapter takes it back to the way it was which I might need at a later date. Anyway thanks for the info again.

 

[Bonzo Banana]

Out of the 4 packs available only one cell is rated for the 20a discharge and that is the so called HG2 pack, the other three are only a max 10a discharge and all will use a 5a cell. Panny ncr18650b are only 5a rated, the risk in useing them is far greater due to the cheap price nature and one can't expect a very good bms inside for the price.
Cheap china packs are known for fake cells.

Yes it's a bit of a gamble but we shall see.

Out of the 4 packs available only one cell is rated for the 20a discharge and that is the so called HG2 pack, the other three are only a max 10a discharge and all will use a 5a cell. Panny ncr18650b are only 5a rated, the risk in useing them is far greater due to the cheap price nature and one can't expect a very good bms inside for the price.
Cheap china packs are known for fake cells.

Not for one second did I think it was 20A discharge. I knew I was getting 20 2.6Ah cells to get the 5.2Ah capacity battery pack and the pack has a maximum discharge of 10.4A based on the maximum discharge of 5.2A per cell. Gives me a maximum wattage of 10.4x42V or 70% time of its peak discharging capacity at 10.4x37V so 437W to about 385W. Nothing amazing but a nice little project. I'm not expecting miracles its costing me less than £30 delivered including VAT. I don't believe these are fake cells though I think they will give true capacity but I could be wrong. I'm curious about how good these packs are.

 

[Nealh]

5.2a then is very much likely as I suspected will be a Sam 26F type cell or a J cell.

 

[Bonzo Banana]

5.2a then is very much likely as I suspected will be a Sam 26F type cell or a J cell.

Yes you are probably right. They mention the cells used for the 6000mAh and 6800mAh packs but for the 4400mAh and 5200mAh packs they just state ;

The new 4400mAh / 5200mAh Chinese-made battery assembly.
Product features: 10A discharge current, real capacity, long use time and long life!

You could easily read that as 10A continuous output but when I went on the Littokala site I could only see the spec of 5.2A max current per cell for the 2600mAh battery listed there. We shall see how it performs.

I see postage is now almost £10 but when I ordered it was free. It has been despatched now so hopefully receive it in a week or so.

 

[Nealh]

My oxygen kit batteries were 11 & 13a respectively using Sam 22F & Sam 26F, they were 5p arrangement but after 18 months of regular use both decreased capacity wise by some 20%. A 17a contoroller and up to 24mph usage saw them off.

 

[Bonzo Banana]

My oxygen kit batteries were 11 & 13a respectively using Sam 22F & Sam 26F, they were 5p arrangement but after 18 months of regular use both decreased capacity wise by some 20%. A 17a contoroller and up to 24mph usage saw them off.

Yes I my plan may not go as well as intended but I'm planning to current restrict the controller which is a lowish current controller anyway which is what many cheaper commercial ebikes do using fairly generic low end Chinese batteries. The ebike below is 115Wh getting on half the capacity of my battery and with peak current output of about half of my battery pack too.

 

[Bonzo Banana]

Another question about these sameport type batteries if they are charged through the discharge connections and have over-charge protection are these actually fully safe with regen? I.e. if you have regen enabled the batteries will prevent regen immediately. You don't have to sort of ride 5 miles using the conventional brake before then using the regen enabled brake lever. You can pretty much use regen from the outset of the journey?

 

[Bonzo Banana]

It turned up today, all seems fine, the charger turned up a couple of days ago so will need to fit the connectors. Above I wrote XT60 but its actually a XT30 connector it has and that is actually what I have already, I bought a multipack of them male and female from aliexpress sometime ago.

One thing I noticed is the label they use doesn't have 5.2Ah capacity as an option that they can tick it has 4.4Ah and 6Ah and nothing inbetween so they had to handwrite 5.2Ah on the label. Makes it look a little less professional but thats really the only obvious criticism I can make generally it seems very nicely constructed.