Making a 12v charger - Page 1
Forum section: electronics / beginners

author: SailorWill
author_rank: Newbie
timestamp: December 29, 2023, 07:37:35 pm
content: Can I do this?I live on a boat and everything is 12 volts (I don’t have enough solar panels and batteries yet to run my 120 v inverter).I see my device’s (brick and lozenge) charger is 120v input and outputs 12 v at 3 Amps. I have another spare charger that has the appropriate jack and it’s brick also states 12v/3a. I was hoping to cut off the brick and lozenge portions of this spare and hook the wires directly to my gel LA batteries (no brick or lozenge, just straight from battery to jack in the device).Will my device determine the amps it wants (3) or will the battery send what it wants and potentially harm my device? Thanks, Will

author: coromonadalix
author_rank: Super Contributor
timestamp: December 30, 2023, 12:50:40 am
content: sorry but your brick, lozenge what is this, are you behind a translation service ??if all your systems is based on 12vdc, you just need battery bank and a solar to 12vdc management / charger moduleif you need 120 220vac stuff you need to accound for current conumption who will be big, very big with an dc to ac inverter120vac at 1 amp is 120 watts, to take it / convert it from 12vdc, it will consume 10 amps, do you have enough reserve220vac at 1 amp is 220 watts, to get it / convert it from 12vdc, it will need 18.8 amps .....

author: Konkedout
author_rank: Frequent Contributor
timestamp: December 30, 2023, 06:07:55 am
content: Yes I do not know what you mean by "brick" and "lozenge".Lead acid batteries are not the most difficult to charge, but it is a bit more complicated than just a 12V power supply.Typically the charger should put out 13.(something) volts and it should be able to operate for a long time in current limit when charging a discharged battery.Also, a proper charger will not be damaged by a reverse battery connection unless you make certain that cannot accidentally happen.I keep my car batteries charged by an inexpensive unit from Harbor Freight in the USA.I could design my own, but it will cost more to build than to buy, and packaging is the big ignored factor. If I build my own, that will be a pcb with wires and and connectors; it still needs an enclosure which (at least in my opinion) is much more of a pain than is the electronics on the board.BTW I don't know if many other people have collected what I have; particularly some number of 18V - 20V enclosed power supplies intended for laptop computers. Some of them were from my own obsolete computers and some were from a previous employer. In my opinion, except for the fact that they are in their own package, the 18V output is a great and relatively safe starting point for other power converters such as battery chargers or making other fixed voltages. I have designed commercial AC/DC power supplies, but for personal/hobby use I think that non SELVhttps://en.wikipedia.org/wiki/Extra-low_voltagevoltages are better avoided.

author: Ian.M
author_rank: Super Contributor
timestamp: December 30, 2023, 06:48:37 am
content: Automotive and marine nominally '12V' electrical systems are almost never 12.0V at the battery. During charging they typically reach over 14V, and can reach 15V, and at low load currents remain above 12V for most of the discharge, down to around 30% charge.Whether or not your equipment with mains to 12V power adapters will tolerate 15% to 20% overvoltage is anyone's guess, but I certainly wouldn't risk it with anything expensive. A safer solution *if* the brick is actually an ordinary 12V 3A PSU is to use a good quality and appropriately rated DC-DC converter, set to 12.0V and 3A current limit. However if the 'brick' is actually a charger with the charge control circuit in it rather than in the device, using a simple constant voltage DC-DC converter may be hazardous unless you modify it to dynamically control the output voltage and current to match the required charging profile for the device's battery type and capacity.In all cases, you'll probably also want an under-voltage cut-out (as commonly used for marine and RV fridges) so you don't damage your 12V battery bank by over-discharging it.If you are using a translation service to post here, it can help to include the original untranslated text with the translation, as general machine translation of technical terms is rarely accurate unless the algorithm has been trained for the specific science or industry., and some of our polyglot experts can usually do better.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: December 30, 2023, 02:40:07 pm
content: I just want to know what the 'Lozenge' is......Uncle Google isn't helping.

author: Andy Chee
author_rank: Super Contributor
timestamp: December 30, 2023, 03:00:27 pm
content: 'lozenge' could be referring to the plastic molded ferrite suppression core sometimes seen on some of these brick type power supplies?

author: p.larner
author_rank: Frequent Contributor
timestamp: January 01, 2024, 01:01:23 pm
content: i thought it was something that you suck on if you have a sore throat.

author: Terry Bites
author_rank: Super Contributor
timestamp: January 01, 2024, 02:15:43 pm
content: You have a mains 12V 3A supply and you want to charge a 12V Lead Acid Battery from it, yes?If you go down the linear circuit type charger you won't have enough headrom to top the battery up to 14V(ish).So where would the power for the 12V psu be coming from. If you have a mains supply just get a regular charger.$20 would get you a basic one.Don't suck on the lozenge!

author: Ian.M
author_rank: Super Contributor
timestamp: January 01, 2024, 03:03:55 pm
content: No, he apparently wants to cross-charge a 12V device from a 12V lead acid battery, without using an inverter and the original 12V PSU.

author: Tens
author_rank: Newbie
timestamp: January 01, 2024, 04:28:10 pm
content: Tablet?