Battery Charger Next Generation: request for comments

What kind of battery charger would YOU like?

Since battery chargers have always been a popular subject among our readers and followers, we were having a discussion in our lab about the kind of battery charger we should design now.

"Should we make a charger for lead-acid batteries?", asked one designer.
"No, no, no!", said another, "that is so old skool, let's make a charger for 20 NiMH cells."
"Nah", said a third, "let's make a charger for 3S or 4S LiPo's!"
Then a fourth designer entered the discussion and it went on and on and on!

Lead acid?
NiCad?
NiMH?
LiPo?
Other?
Packs or separate cells?
Monitoring or not?
Balancing or not?

So, to end the discussion, it is now up to you to enter the discussion and come up with a decisive answer...

What do you want?

Discussion (21 comments)

Stefan Weilhartner 6 years ago

the new unsiveral charger should have two different display options. a cheap small display and the option for a bigger high-res display with a lot of interesting software features to add.
timers, nice visualisation of charging process, etc.
an option for bluetooth communication would be nice, so that a mobile phone can read out the voltage every x seconds and show a nice curve over time etc.
or also with the possibility to be controlled by some other device.
so someone could implement new features for multiple discharge and charge cycles on the mobile phone or some other device.

0 Comment(s)

Stefan Weilhartner 6 years ago

sometimes i don't use my car for many weeks. then the 12v lead battery in my car runs low and i can't start my car. well, i have of course a lab-power-supply that i could use as a charger but i don't have a 240v wall socket near the car.
so i want to transport energy in form of a battery to my car.
so an interesting charger for me would also be one, that can be supplied with other batteries.
i have some li-ion batteries in my appartment connected to gether in series to deliver about 14v. but that is not enough to get a lot of current directly into the 12v battery.
so a dc/dc step up converter with a current limiter would do the trick.
so a charger that could be (optionally) supplied with energy from a battery pack with a dc-dc charger would be nice.
not everyone would need that option so it would be interesting to build an extra pcb to add to the charger or leave out an area on the original pcb where everyone could decide to add the parts or not.

RICH OBERMEYER 6 years ago

You need a solar solution.
A small solar panel inside the car with a cheap 50mA LA charger will keep your battery from going flat. This requires no AC. Some companies connect the solar panel directly to the lighter plug with just a simple diode. Solar by design is current limited so a trivial design task.
You can buy one on Amazon for $20.

1 Comment(s)

Rene van Amerongen 6 years ago

Mijn hoop/idee is een Li-Ion instelbaar per cell en per pack met een BMS, tot 1-5kWh systeem. Er zullen genoeg mensen zijn die graag hun PV systeem willen opwaarderen met een opslag systeem.

0 Comment(s)

magicChristian 6 years ago

The main goal for a new charger should be a universal charger for all common battery chemistry (Lipo, NiMH but also NiCd and Lead acid). To be usable as a power supply woul be a nice feature.
To control current and to monitor voltage it is necessary to have a multichannel ADC and a microcontroller. Because of low speed requirement a raspi is not necessary; an ARM M3 would be a good choice. The maximum voltage should be 18 V to cover 4S LiPo and 6 cell Lead Acid.
The maximum current maybe 1 Amp and at least 4 places for AA or AAA cells.
The voltage resolution should be better then 50mV which is easily done by 10 bit ADC.
One problem is charging LiPo cells in a serial configuration - the only correct way needs contact to all nodes between cells (there are special IC´s for that purpoe available).
I am looking forward to this project and would like to be a meber of the team.

RICH OBERMEYER 6 years ago

A simple ARM M0 should work to control the supply and ADC. Don’t need an M3 for this simple task.

solar 6 years ago

For my applications the specs might be a little bit wider e.g. 40 - 50V and 3 - 5 A. Special for a function as lab-supply this is more comfortable. When cost becomes an issue the unot could be made modular. Units in parallel for higher current and stepwise higher voltage mains front end. Units in series seems not a good idea to me. Also additional functions like balancer for Lipo could be an add on. The basic control (and measurements) should be identical. Another useful add on could be a discharging unit to make it a battery tester. (supplying the enrgy back into the grid will bring the function close to the home storage and UPS function)

2 Comment(s)

Richard Cooke 7 years ago

Programable Switch Mode powersupply, with I2C DAC to set voltage, I2C DAC to set current limit. I2C ADC to measure battery terminal voltage, I2C ADC to measure battery terminal current. Then I2C ADC to set discharge current. (ADC and DAC should require a bandwidth of about 1Hz). Use Raspberry PI, to set up and monitor the battery, and then report battery status. No surface mount please. Maybe a cheap graphic touch screen too, maybe audio user feedback. But I don't know how to program tones and MP3/WAV playback in 'C', on a Raspberry Pi. Program for reverse polarity protection of the battery.

Richard Cooke 7 years ago

How about sense wires to battery. Joined together by two 2ohm resistors on the pcb. This compensates for voltage drop along the charging cable to the battery. For each terminal a thick wire carries the current and a thin wire measures the voltage. Both wires are connected together at the battery terminal. On the pcb, the thin wire goes to voltage divider of the voltage comparitor. The thin wire carries almost zero current. The 2ohm resistor is there to stop overvoltage should the thin wire break, or the constructor cann't be bothered with sense wires.

1 Comment(s)

BJ Thomas 7 years ago

Ultra low power standby , temp compensation and monitoring , USB charging port
lead acid chargers still in use and worh a look...

0 Comment(s)

karim rihani 7 years ago

Lead Acid Battery charger

0 Comment(s)

Kargo 7 years ago

Ladung und Entladung von mehrzelligen Lithiumakkus: seriell
Für mich wäre eine Auswertung der Spannungsverläufe an den Balanceranschlüssen wichtig, um einen Rückschluss auf Funktionssicherheit des Akkupacks zu erhalten.

Quenton 7 years ago

Most folks building a charger will be happy to perform some degree of programming or ideally select from a set of software charging functions/libraries. The basic hardware must be flexible.

For RC models I use Lipo 1, 2 & 3 cell batteries with 12V lead acid for charging in the field or for starting IC engines and NiMH for on-board power.

I would like realtime feedback data during charging. Temp protection?

PeteLabs 7 years ago

Just reading the OP again: the poster ("rjv") didn't give us a complete context for the question. Are we talking about a device that would be "manufactured" and sold to Elektor readers as a useful battery charger? Or are we talking about something that would be used "in the lab" by the Elektor team? Regardless of the answer, I doubt if a charger dedicated to a specific chemistry/configuration is worth doing.

PeteLabs 7 years ago

Completely agree with the "solar" comments. Defining the requirements is more than just choosing what type of battery support. From the OP, it sounds like a "lab" environment, and NOT a commercial mass-produced product. For a commercial product, you would realistically need to identify your Marketing Requirements, which is going to be something rather specific. But for "lab" use, as "solar" has indicated, your target should be "flexibility" - don't focus on one chemistry or configuration. A charger can be considered as little more than an independently programmable voltage and current source, which can be varied over time. Sensory inputs are voltage, current, and temperature. Extra voltage inputs can be used to discover a 'balancing' problem with multiple-series packs. Consider using appropriate FET switches so that individual cells can be charged separately (to fix balance issues, etc.). Include a switchable load resistor - it can be used for two things: 1) to do a "capacity test", where you measure the total amount of energy that the battery contains; 2) to do a "load test", where you first measure the open-circuit V, then briefly turn on the load, and measure the V again, allowing you to calculate the internal resistance of a cell.

solar 7 years ago

Charging multiple serial connected Li cells is a story on it's own. With a build-in BMU you must know how much charging current this unit can handle in case one of the cells is bypassed. Better is connecting a BMS from the charger to control the equalizing current. As free byproduct all information of individual cells is known.
This level of discussion tends to go to writing specs. What will be next step?

RICH OBERMEYER 7 years ago

Charge and discharge of multicellular lithium batteries: serial
For me, an evaluation of the voltage curves at the Balanceran connections 
would be important to obtain a conclusion on the reliability of the battery pack.

5 Comment(s)

solar 7 years ago

Why choose? ....combine!

Since a battery charger is basically a voltage limited current source one universal design could be used with different software algorithms. A voltage and current sensor could be extended with more voltage sensors for balancing (also useful for NiMH). In a modular design a programmable load and logger can make it a battery tester and multiple loads can help de balancing.
By adding or omitting components the specification could be adjustable vs cost. Putting boards in parallel could also adept to a particular situation. Two or three different user interfaces from simple dumm charger, more controlability or extended display for battery testing makes low cost also possible. And don't forget the themperature option for fast charging applications.
I am availlable for helping defining the specifications.

Stefan Weilhartner 7 years ago

using a microcontroller with a little bit more ram could be used to store the whole loading curve and with an optional bluetooth module a mobile phone could be used to display nice informations.

1 Comment(s)

bertjoop 7 years ago

All charger designs are for the bigger type of batteries. It would be nice to see a design for a hand held device with a small battery (9V).

0 Comment(s)

Lys 7 years ago

During the last year I faced two charging Challances:
How to charge an NiMH Battery Pack with 20 Monocells (for one of the earlyer eBikes)
How to charge my 12V Metabo Cordless Screwdriver

In both cases the old charger had given up and I hat to improvise.

Unfortunately the iMax B6 Charger ruined one of my screw-driver battery pack, so I am in hope a new developed charger will do better.

0 Comment(s)

llagmaw 7 years ago

A charger for a LiPo battery should determine the number of batteries, always check the polarity before charging, ask for the capacity or maximal current and ends with trickle-charging.

0 Comment(s)

Richard Cooke 7 years ago

In the last few years, we now have microprocessors. So lets have an intelligent charger, that charges fast and charges everything. That can self determine what type of battery is connected to it, if possible. That can report on the condition of the battery. Maybe via RJ45, USB, blueTooth and/or LCD

0 Comment(s)

RICH OBERMEYER 7 years ago

Why make it so complex. Use the LinearTech LTC4015 which can charge pretty much anything.
Add a simple LCD interface and a few buttons and everybody can use it how they need.
It will be cheap and meets all requirments

0 Comment(s)

Mark Peterson 7 years ago

Expanding on the previous suggestions:

A charger that is universal AND automatically determines the battery type and battery voltage. This should be easy with the processing power, A2D, and D2A functionally of today's microcontrollers.

Just connect power to the charger and connect the charger to the battery and it will fully charge the battery whatever kind and voltage.

0 Comment(s)

Ruben 7 years ago

Lead acid batteries (also usable for other batterie types):
1. 3 functions:
  1. charge (constant current charge, topping charge, float charge)
    1. different charge programs for flooded, gel, AGM, ... batteries.
    2. different algorythms: fast, slow, recommended charge
  2. discharge, until [configurable]% discharged
  3. pulse conditioning (high voltage pulse; against sulfation)
2. Configurable scheduler. Define time slots for charging, discharging or pulse conditioning based on a year calendar (month, day, hour). Especially for batteries of motorcycles or oldtimers. Is keeping them constantly charged at 100% during an inactivity period optimal?
All batteries:
1. How to keep a battery in a good condition during a long inactivity period? What is the recommended charge % (50%? 75%? 100%? -> type dependent) to store some batteries for a long time. It should be possible to select a function "charge for use" or "charge for storage".
2. in function of ambient and battery temperature
3. Show voltage, current, temperature, internal resistance, ...
4. Ethernet interface
  1. Get information
  2. Change configuration
  3. Controlling (start, stop, ...)
  4. Log charge cycle (voltage, current, temperature, ...)
  5. Open protocol (make your own program or connect it with some intelligent system.

Good idea to request for comments.

0 Comment(s)

Markus Oliver Pfeil 7 years ago

I would fancy a charger that can be used to charge anything with a USB charge input from a single cell battery (1.2-3.6V) and charge that cell back from a variable input voltage. All in small package and configurable for NiMH, LiPo etc.

0 Comment(s)

JP10 7 years ago

All of the mentioned requirements can be considered essential. Therefore, It must be possible to create a charger that is truly Universal.

Should be a superb project.

0 Comment(s)

Michael Zigan 7 years ago

I prefer a scalable universal charger:

Charging algorithm selectable.
CAN Interface (for BMS and Display)
Output current salable with individual high power unit.

Michael

0 Comment(s)

Ulrich Dreher 7 years ago

Some digital power charger for eBike battery pack charging would be great!
Some charger (see below for more details) providing an "immediate solution", doubling as a development base for more challenging applications - would be great and might draw attention.

Basic data: AC input with PFC, 500+ W (10+ A), output up to 60 V.
Charging algorithm selectable.
Balancing not required (as there will be no accessto the individual cells).
Prepared to interface with some BMS (possible interfaces: CAN, basic UART (where a number of physical interfaces may apply).

I'd consider such an advanced charger a lighthouse project.

BTW: would give a nice power supply as well. - Digital power is capable to realize the "impossible".

0 Comment(s)

Roel Arits 7 years ago

My personal advise :

If you skip the fast charging of lead acid batteries with high currents, your power supply doesn't have to be very powerfull. Instead you could provide trickle charging to keep the battery topped-up, because that doesn't require high currents. NiMh, NiCad and Lipo can be charged fast with relative low currents.
Use of embedded software allows to control the voltage and/or current, so any voltage or current curve can be implemented. Control loops can be easily made in software to generate constant voltage and/or constant current.
A kind of guidance GUI can be used to guide the user through menu's like : Select battery type, select how many cells you want to charge, select capacity .....
The menu tree depends on the type of battery that was selected.
When people need extra features they can be provided as an upgrade of the software.
Implement as many as possible features that you can think of, because if your hardware is flexible enough, it will be only a matter of writing extra software.
It would be nice if the charger can give an indication of the capacity of the battery, using the charge current and time to charge the battery.
Showing voltage/current and monitoring time to fuily charged is always nice to have.
I guess NiCads will slowly disappear, but when you can charge NiMh and LiPo, then it is no extra effort to charge NiCads.
Maybe even provide a temperature sensor input for safety, so you can measure the temperature of a battery while charging and shut down the charger when the temperature gets too high. It could be an option in the software. But then the user has to know how to place/use a temperature sensor properly.

The best espresso still comes from a dedicated espresso machine and not from a
do-it-all coffee, espresso, cappucinno and hot chocolate-machine.

I hope i didn't start a discussion on coffee now ! ;-)
Succes !

Sedemas 7 years ago

I am on the prowl for a good charger for lithium based battery packs. The packs i use contain 3 or 4 batteries.
One can find enough battery chargers for lead-accid, NiCad, NiMh. Those batteries are relatively easy to charge even with high currents. For Lithium based batteries one need a good cell-balancing and just that part of the charger is of interest for me.

Success with the project!!