What voltage to charge my AGM lead-acid battery? - Page 1
Forum section: electronics / beginners

author: skyler
author_rank: Regular Contributor
timestamp: February 26, 2016, 03:40:56 am
content: I have a 10 Amp-hour AGM 12V lead-acid battery. I am using an old security system charger to charge this battery, and I have noticed that I can set the output voltage with one of the trimpots on board.The battery is a Werker battery (Sticker fell off, so I don't know the part number) and I don't think this charger is smart (ex. charge 14 volts until it is full, and trickle it at 13).So what would a safe output voltage level be for this charger? I was getting 3 amps out of it, but I brought that down to 1 amp with some small value series power resistors.

author: tautech
author_rank: Super Contributor
timestamp: February 26, 2016, 04:01:45 am
content: Typically charging specs for AGM batteries are printed on the case but what is omitted and normally only in the datasheet is the charging rate and max initial charge which is typically 0.3 of the battery capacity.2 charging voltages are listed; Standby 13.5 -13.8 and Cyclic 14.4 -14.7 ....although 1 AGM battery I have here has a listed Cyclic charge voltage of 14.4 - 15 V that IMO is too high.Hope that helps.

author: Lightages
author_rank: Unknown
timestamp: February 26, 2016, 04:06:05 am
content: It depends on the manufacturer. I run my AGM batteries at 14.7V for the bulk voltage and absorption voltage, and then down to 13.6V for float. Do not let the battery set at absorption for more than an hour or two. It also depends on the temperature. Lead acid batteries also have a temperature coefficient usually stated in -mV/°C from 21°C. So if your batteries are sitting all the time at other temperatures you can calculate the difference if you have the spec. Generally you can use -100mV/°C.

author: mtdoc
author_rank: Super Contributor
timestamp: February 26, 2016, 05:54:33 am
content: As Lightages says, it depends on the battery. Any good battery manufacturer will provide specs.As a general rule, AGMs use a higher bulk charging voltage than flooded LA batteries (FLAs).The key thing with AGMs is that if you use too high a voltage (like those used to equalized FLAs) you can cause outgassing which will pop the valves and ruin the batteries.But - if you chronically undercharge them with too low a voltage, (or too short and abosorb stage) they will sulfate, and unlike FLAs, since you cannot do periodic equalization charging, you will not be able to reverse any of that sulfation.Overall, AGMs are much less forgiving than FLAs.

author: skyler
author_rank: Regular Contributor
timestamp: February 26, 2016, 03:32:33 pm
content: I am pretty sure the battery is a Werker wka-12, but I can not find any specs anywhere.If I don't have the two stage charge and then float, just a single power supply, is there a recommended voltage (ex. keep it at 13.5)?Here is the charger I have,Alarm-Saf Power Supply / Charger 12vdc outputAS/PS5-BFS-12http://www.alarmsaf.com/pdf/installation_instructions/52-130w.pdfhttp://www.alarmsaf.com/pdf/data_sheets/52-104.pdf

author: tautech
author_rank: Super Contributor
timestamp: February 26, 2016, 03:40:09 pm
content: Quote from: skyler on February 26, 2016, 03:32:33 pmFloat = Standby