CCCV lead-acid battery charger - Page 1
Forum section: electronics / projects

author: Siddhat
author_rank: Regular Contributor
timestamp: June 22, 2020, 07:46:18 am
content: Hey guys!I am working on a project that includes battery charging. I need to charge a lead acid battery using Constant Current Constant Voltage (CC-CV) algorithm. I've already designed a buck boost converter in order to implement the CC-CV algorithm. But after many days of research I did not find proper circuit diagram to implement the algorithm. How is such an algorithm implemented in the buck boost converter? Are there circuits to implement this algorithm or am I missing something?Kindly appreciate your help!!

author: bin_liu
author_rank: Contributor
timestamp: June 22, 2020, 08:10:14 am
content: Too few conditions.The secondary of the flyback topology only needs one circuit composed of LM358 to charge the lead-acid battery(3 paragraphs).

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 22, 2020, 09:18:01 am
content: Google for a schematics of popular CC-CV converters. For example, for such wide-popular on ebay.

author: Siddhat
author_rank: Regular Contributor
timestamp: June 22, 2020, 03:58:35 pm
content: After days of searching and researching, google too seems like a small place!! I got the concept of CCCV but not the circuit.

author: Siddhat
author_rank: Regular Contributor
timestamp: June 22, 2020, 04:01:45 pm
content: Quote from: bin_liu on June 22, 2020, 08:10:14 amI know about feedback and PI control but do not know how to implement it since there are too many design considerations. So, looking for a even better solution to design the circuit. How can op-amps be used?

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 22, 2020, 04:06:06 pm
content: https://circuitdigest.com/electronic-circuits/float-charger-circuit-for-12v-sla-batteryand many more circuits in google (keyword "sla charging circuit")

author: Benta
author_rank: Super Contributor
timestamp: June 22, 2020, 09:34:52 pm
content: For lead-acid, you only need a CV charger with current limiting. If it has to be fancy, include ambient temperature measurement for the CV part.

author: bin_liu
author_rank: Contributor
timestamp: June 23, 2020, 12:53:58 am
content: This is a previous project, and the accessory is a small power product, you can refer to it.The attachment is a circuit diagram of an RCC topology, which is also applicable to the flyback topology.

author: Siddhat
author_rank: Regular Contributor
timestamp: June 23, 2020, 04:30:12 am
content: Quote from: Benta on June 22, 2020, 09:34:52 pmThe voltage at the output of the buck-boost converter is set by the voltage of the battery. So,the current has to be controlled. For that, in the Constant Current stage, limiting the current output of the buck-boost to the initial current of the battery is a good idea but once the battery voltage rises and reaches the Constant Voltage stage, does the exponential current drop happen automatically? or, has the current be controlled in such a way that it drops exponentially when it reaches in the CV stage?

author: Siddhat
author_rank: Regular Contributor
timestamp: June 23, 2020, 05:09:54 am
content: Quote from: Mechatrommer on June 22, 2020, 04:06:06 pmThe circuit is explained well. When the battery is charged the relay cuts off the charging voltage, but, when the battery again discharges the relay again turns ON the charging voltage. This causes tripping of relay. Now, can a hysteresis be added to the op-amp, to overcome this?

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 23, 2020, 05:41:55 am
content: Quote from: Siddhat on June 23, 2020, 05:09:54 amadd resistor (maybe 10-100K ohm) from relay pin 4 to LM358 inverting input (pin 2)Quote from: Siddhat on June 23, 2020, 04:30:12 amthe simplest current limit/control "programming" is using power resistor (maybe 1-10 ohm) on buck-boost output to battery.

author: Benta
author_rank: Super Contributor
timestamp: June 23, 2020, 10:13:18 am
content: Quote from: Siddhat on June 23, 2020, 04:30:12 amThis is correct, but "current control" is overkill. Current limiting is enough. The current will drop by itself when the charge voltage has been reached.

author: Siddhat
author_rank: Regular Contributor
timestamp: June 23, 2020, 03:20:13 pm
content: Quote from: bin_liu on June 23, 2020, 12:53:58 amThe jpg file doesnot open. Will you upload once more?

author: bin_liu
author_rank: Contributor
timestamp: June 24, 2020, 12:35:51 am
content: look here,It‘s a PDF file.

author: trobbins
author_rank: Frequent Contributor
timestamp: June 24, 2020, 01:12:38 am
content: Siddhat, I suggest you do more background reading on lead acid battery charging to appreciate better what is happening in the battery and how a typical charger works. You also need to elaborate on your project, as there is no detailed information except that it is a lead acid battery. I suggest you also get your algorithm reviewed, and perhaps even set up a simple manual charger and follow your algorithm through by manual changes. Nobody knows what you are aiming to really do, and batteries can be hazardous when ill-treated.

author: boB
author_rank: Frequent Contributor
timestamp: June 24, 2020, 01:34:14 am
content: Yeah, you will need to tell us what the amp-hour rating and nominal voltage of this battery is to say how large the supply needs to be.And, is it a flooded, AGM, gell, or sealed lead-acid battery etc. ?You will usually want to voltage regulate for the absorb stage after bulk charging (current limit) is done.

author: bin_liu
author_rank: Contributor
timestamp: June 24, 2020, 03:47:44 am
content: 3 stages charging is a common practice.Before, my job was to develop chargers, i hope this would help you.

author: Siddhat
author_rank: Regular Contributor
timestamp: June 24, 2020, 06:26:01 am
content: Quote from: bin_liu on June 24, 2020, 12:35:51 amThank you..trying to understand the circuit!!

author: Siddhat
author_rank: Regular Contributor
timestamp: June 24, 2020, 06:36:52 am
content: Quote from: trobbins on June 24, 2020, 01:12:38 amOkay..I am trying to charge a 12V 7.8Ah C20 rating lead-acid battery using a buck boost converter from a solar panel that implements a MPPT algorithm. Since, I've already designed and simulated the MPPT algorithm, I now need to charge the lead-acid battery using a CCCV algorithm to ensure safe charging procedure. Yes, reading the theory on how a lead-acid battery and how a charger works is actually good to appreciate and understand what's happening acutually.

author: Siddhat
author_rank: Regular Contributor
timestamp: June 24, 2020, 06:44:50 am
content: Quote from: boB on June 24, 2020, 01:34:14 am7.8Ah, 12V sealed lead-acid battery. Yes, maintaining the voltage after the bulk stage is important to repay for the losses due to self discharge of the battery. But, what is the regulating voltage value that battery needs after the bulk charging stage?

author: Siddhat
author_rank: Regular Contributor
timestamp: June 24, 2020, 06:48:50 am
content: Quote from: bin_liu on June 24, 2020, 03:47:44 amYes, 3 stages charging is a common practice. It is great to learn from people who actually worked on developing chargers. That really helped me.

author: bin_liu
author_rank: Contributor
timestamp: June 24, 2020, 09:39:30 am
content: If you want to make an MPPT controller, this microchip document may help.“Practical Guide to Implementing Solar Panel MPPT Algorithms”http://ww1.microchip.com/downloads/en/Appnotes/00001521A.pdf

author: trobbins
author_rank: Frequent Contributor
timestamp: June 24, 2020, 12:12:23 pm
content: The charging requirements for a lead acid battery always relate to what the manufacturer of the battery states - so you need to identify the manufacturer and the model of the battery you have.The manufacturer may provide recommended charging regimes for different use applications, and some batteries are designed specifically for PV system use, but even then the charging regime that is most appropriate may not align with the particular PV use profile that the manufacturer has designed and tested the battery against.You may well be just using a low cost generic VRLA monobloc sold for the broad UPS market, where the battery is designed to sit at float voltage 24/7/365, and very infrequently get forced in to a high rate discharge followed by a current limited return to float level. That type of battery was not specifically designed for typical PV type charge and load profiles (where the load profile can encompass a wide range of uses).So I suggest you start by linking to the manufacturers recommended operating instructions for the battery model you have, even if there is no comment specifically on PV applications. Failing even a basic note from the manufacturer, the battery may have some basic charging notes printed on the casing, or the battery may have had a sales brochure.