60A dc to dc liion charge controller - Page 1
Forum section: electronics / general

author: Ian 2
author_rank: Newbie
timestamp: June 22, 2020, 08:09:58 pm
content: HiI need to charge a li-ion 3s (12.6V) pack with my car alternator (14.4V). Because the batteries should be charged with a certain charge curve (as explained in eevblog #176) I need a circuit or chip that regulates the voltage and current to the battery. (cell balancing is handled through separate bms) Because the alternator could overheat I want to be able to manually set the maximum current.The problem is my charge current should go up to 60A, I can't find these kind of chips for these currents, unless i spend +$200 on a victron controller. Does anybody know a budget solution/ circuit/ chip i could use/make for this?Thanks!

author: bin_liu
author_rank: Contributor
timestamp: June 23, 2020, 01:54:18 am
content: I think you may have misunderstood the role of BMS. BMS does not have the function of controlling the current. Charging the battery through any device must use a constant current. Such a large charging current does not have a dedicated chip. My suggestion It is to use PWM controller + half-bridge driver + high-power MOS to design a constant current switching power supply.

author: james_s
author_rank: Super Contributor
timestamp: June 23, 2020, 05:51:49 am
content: Use a Li-Ion charger powered by the alternator. These batteries are notorious for catching fire if abused, you don't want to screw around with trying to charge one directly.

author: Ice-Tea
author_rank: Super Contributor
timestamp: June 23, 2020, 06:09:46 am
content: Depending on your level of expertise, either get an off the shelf charger or browse around here:https://www.ti.com/power-management/battery-management/charger-ics/overview.html

author: Ian 2
author_rank: Newbie
timestamp: June 23, 2020, 09:47:40 am
content: I'm sorry, I think you misunderstood my question. I know the function of a bms and i'm planning to use the bms for cell balancing/ load protection only. This means I can use a regular charger instead of a 3s balance charger. I know i need a charger cirquit to charge the batteries safely. From my experience in the RC world i know the way to handle lithium batteries.Maybe I should have asked this instead: I'm looking to make a liion dc to dc charger rated up to 60A with an external control (eg a potentiometer) to set the max charge current. This way i can limit the charge current when the car engine is at idle to prevent the alternator from overheating.The problem with off the shelf chargers is the price, I can't seem to find dc to dc chargers rated for this high of a current that are within my budget.I can solder and have basic programming skills, but my knowledge about electronics is not great, this is why I'm asking for help disigning a circuit and choosing the components I would need.

author: David Hess
author_rank: Super Contributor
timestamp: June 23, 2020, 01:51:31 pm
content: Quote from: Ian 2 on June 22, 2020, 08:09:58 pmThe budget way is to operate the alternator in the way it was intended where the output current is controlled by the field current. So the alternator is connected directly to the batteries and the charge controller drives the field winding of the alternator.But this amounts to a fully custom solution so it will likely be better to buy an already existing charge controller which will operate off of your existing alternator output unless you are intended to replace a lead-acid battery with a lithium rechargeable battery.

author: Ian 2
author_rank: Newbie
timestamp: June 23, 2020, 02:07:02 pm
content: Quote from: David Hess on June 23, 2020, 01:51:31 pmI thought about controlling the alternator itself, the problem is the regular lead starter battery will also stay connected. I don't think charging a lead acid and lithium battery in parallel would be the best idea in terms of safety and controlability.

author: David Hess
author_rank: Super Contributor
timestamp: June 23, 2020, 02:42:27 pm
content: Quote from: Ian 2 on June 23, 2020, 02:07:02 pmSo what you really want is a 60 amp 3 cell lithium-ion charge controller which will run off of an existing unmodified automotive 12 volt supply. Finding one will be tricky.

author: Ian 2
author_rank: Newbie
timestamp: June 23, 2020, 02:55:14 pm
content: Quote from: David Hess on June 23, 2020, 02:42:27 pmI noticed, thats why I'm asking here if someone has another option or can help me designing my own charger circuit.

author: David Hess
author_rank: Super Contributor
timestamp: June 23, 2020, 03:05:01 pm
content: Quote from: Ian 2 on June 23, 2020, 02:55:14 pmThe easiest way will be to power an existing 120 volt charger with a 1000+ watt inverter. It will not be pretty but it will work.

author: ocset
author_rank: Super Contributor
timestamp: June 26, 2020, 12:17:39 pm
content: Why not just charge it off the mains?Buy a ACDC power supply from meanwell say. (say 48V, 1kW or 24V, 1kW)Shove a load of paralleled current sources off the output of it into your battery.Like you say, you wont find a single 60A current source for 3S Li so just shove a load of lower current ones in parallel......current sources are fine in parallel.

author: Ian 2
author_rank: Newbie
timestamp: June 27, 2020, 01:28:53 pm
content: Quote from: treez on June 26, 2020, 12:17:39 pmthe application is a camper van for off grid use, so there won't be a mains connection available. Sources in parallel sounds like a good idea though, thanks!

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 27, 2020, 01:58:49 pm
content: A buck converter with current limit sounds like the way to go. Or if it's truly a large pack, might be worth adding an auxiliary generator to the engine.If I were designing it, I would convert the van into a hybrid using commonly available EV parts. It would be able to operate the engine at much closer to its peak efficiency point. EV batteries are cheap for the capacity and can handle very large peak currents.