power supplies as battery charger - Page 1
Forum section: electronics / general

author: Raj
author_rank: Frequent Contributor
timestamp: March 31, 2018, 04:42:07 pm
content: What's stopping people to upload custom firmware into high ampere power supplies with decent voltage to get a "dedicated battery charging" mode?Even the people making power supplies form scratch and implementing big screens with sufficient enough input controls,aren't doing it.

author: Jeroen3
author_rank: Super Contributor
timestamp: March 31, 2018, 04:56:41 pm
content: Because a very limited number of people use their high ampere power supplies as battery chargers.In case you aren't aware, but there are things called "multi chemistry battery chargers". They are much smaller, cheaper and also feature Ah measurement, discharging and balancing!Not to mention, various other protection features.

author: bitseeker
author_rank: Super Contributor
timestamp: March 31, 2018, 05:12:57 pm
content: Nothing's stopping people from doing it, per se. Companies consider product lines, market needs, profit margins, the competition, and a bunch of other things when determining what to put into a product or series of products. So, it's more a question of should it be done (how, when, etc.), rather than can it be done.There are power supplies that can behave like batteries and/or battery chargers (e.g., Keithley 2306).

author: rdl
author_rank: Super Contributor
timestamp: March 31, 2018, 07:35:13 pm
content: I charge my Black&Decker drill with my E3610A. It works way better than the little 300 mA wall charger it came with that burnt out the third time it was used.

author: station240
author_rank: Unknown
timestamp: March 31, 2018, 10:56:49 pm
content: You'd need settings for the different battery types, lead acid, NiMH, Li-Po, LiFePO4 etc.Lets say with aim for making one that does Li-Po cells, as most complex option.1) We need some way to detect when the current drops low enough to be end of charge (60mA per cell?)So current measurement circuit needs to be accurate enough.2) Needs to do CC then switch to CV at 4.2V3) Option for cell monitoring/balancing for 2s or greater strings.4) Has various settings, eg only charge cells to 80% to increase lifespan.It's all doable, it just software, problem is the software is going to be more complex than a normal PSU, requires extra time/effort to do.Perhaps they need to upgrade the hardware, more ROM/RAM, add an EEPROM for storing settings, etc.I've got a big PSU here where the chip at heart of it all is a PIC18F2321, yes I could reprogram it I suppose, but first I have to get the software and schematic, or reverse engineer it all.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 01, 2018, 04:27:07 am
content: It actually takes additional hardware to do current limiting as opposed to just overcurrent protection. I have modified a server PSU into a high current 4S charger. Unlike many ATX PSUs, the server PSU actually has an active droop circuit (decreasing the voltage slightly under load) in order to allow for load sharing. It was fairly easy to modify that into a current limit loop.

author: raptor1956
author_rank: Frequent Contributor
timestamp: April 02, 2018, 09:56:05 pm
content: There's power supplies and there's power supplies -- if we're talking bench power supplies then you're probably going to waste a lot of power and energy owing to the linear nature of such supplies. OTH, if you use a switch-mode PS that would not be a problem, but you don't typically see switch mode PS's with adjustable current and voltage limits.There are many off-the-shelf battery chargers and cell balancers that do a far better job of charging and balancing a battery (as apposed to a cell).Interestingly, some batteries have a good deal of smarts built into the battery itself. For example ... my DJI Phantom 4 Pro drone uses a 4S battery with built in micro-controller that actually manages the charge and balancing. It prevents over charging and over discharging and communicates to the drone such info as: battery voltage, voltage of each cell, temperature, and current level. Periodically, when new firmware for the drone is pushed out, they also push out new firmware for the batteries as well.Brian