Increasing the charge rate.

[Cisco-man]

Hi. I’ve gained a number of swytch 2A chargers which are of good quality. 2A is great for my 5Ahr swytch packs as I can top them up to full in less than two hours if the weather looks good and I get the urge to go riding.
On my 16Ahr Yose pack, I’m now thinking of charging it occasionally using two, 2A swytch chargers in parallel - giving around a 4A charge. The swych packs are probably 10S 2P, and the Yose pack 10S 4P or better, so the batteries themselves should be happy. The chargers should be likewise.

Do you feel that the BMS and any associated wiring would be ok doing this? Anything else that could be an issue?

 

[Bikes4two]

As far as I understand it, lithium battery chargers have two distinct charging phases: Constant Current and Constant Voltage (CC/CV) with CC first then CV.

Exactly what determines the changeover from one to the other is not something I've looked into but I'm thinking that with two such chargers in parallel, might the system get 'confused' and might one charger end up trying to charge the other?

A 4A charger is not expensive so why faff around?

 

[Ghost1951]

How quick a turnaround do you actually need?

I think charging faster has some impact on useful battery life. If that is true, it would be a shame to shorten battery life, unless there was a good reason to do it.

 

[saneagle]

Hi. I’ve gained a number of swytch 2A chargers which are of good quality. 2A is great for my 5Ahr swytch packs as I can top them up to full in less than two hours if the weather looks good and I get the urge to go riding.
On my 16Ahr Yose pack, I’m now thinking of charging it occasionally using two, 2A swytch chargers in parallel - giving around a 4A charge. The swych packs are probably 10S 2P, and the Yose pack 10S 4P or better, so the batteries themselves should be happy. The chargers should be likewise.

Do you feel that the BMS and any associated wiring would be ok doing this? Anything else that could be an issue?

Most BMSs can charge up to 5A. It's the cells that get damaged by fast charging. Personally, I'd be investing in 1A chargers for those Swytch packs.

 

[Cisco-man]

Most BMSs can charge up to 5A. It's the cells that get damaged by fast charging. Personally, I'd be investing in 1A chargers for those Swytch packs.

I respect your wisdom on such matters. My reasoning that the packs should be happy with 2A - 4A charge rates, is that we discharge them (when we are riding) at this sort of rate.

 

[saneagle]

I respect your wisdom on such matters. My reasoning that the packs should be happy with 2A - 4A charge rates, is that we discharge them (when we are riding) at this sort of rate.

Charging and discharging is different. Look at the specification for your cells. Most are recommended for charging at 0.2C, so 2 x 2.5ah in parallel should be charged at 0.2 x 5 = 1A.

 

[matthewslack]

The CC-CV is likely automatic for generic, two wire chargers:

The first part, CC, constant current, charges at the charger's current output until voltage reaches maximum.

The second part, CV, constant voltage, relies on the charger output voltage being properly regulated to 42V in the case of a 36V system. It can't go higher, and the current will naturally reduce as voltage rises.

Four wire power plus comms chargers may manage the charge more actively.

 

[Nealh]

What charge current any batteyr can take is dependant on the cell spec.
The Sam 25r for instance is a 2500mah cell rated for 25a and a 8a charge rating, Sam 25r is a top cell.
Most generic common battery cells may suffer at 4a , find out the cell specs first.