Need some lead acid wet cell opinions - Page 1
Forum section: electronics / projects

author: CaptDon
author_rank: Super Contributor
timestamp: April 27, 2021, 04:08:56 pm
content: The majority of my ham station is all 12vdc and so 13.8vdc to 14.4vdc is entirely acceptable. The problem I am having is short life span of the batteries. I first tried GelCells of the 12vdc 12ah and 12vdc 25ah variety and kept them float charged at around 14.2vdc and 72f room temperature. After about a year they simply seemed to be open circuit. They would only push small amounts of current until the voltage drop was unacceptable and they wouldn't accept a sensible charge even at 16vdc applied. They simply drew very little charge current. Then I went to wet lead acid and bought a 'garden tractor' style 340CCA battery. I held its charge at a steady 13.6vdc and within a year it fell off severely in capacity and looking into the cells I could clearly see the purplish/pink signs of sulphation on the plates. Ramping up the charge immediately gave the stench of sulphur and the appearance of at least one cell doing nothing. Any ideas about the short battery life? My charge current is limited at around 5 amps peak and I am certainly putting way more watthours into the battery than I am ever drawing from it. I am using constant float voltage regulation. Peak current draw may be 25amps on voice peaks with my 100 watt lowband SSB transceiver.

author: jmelson
author_rank: Super Contributor
timestamp: April 27, 2021, 04:44:40 pm
content: 14.2 V indefinite float charge is too high for Gel-Cells. 13.6 is better. Also, sulfation occurs with batteries when they never have to deliver power to a load. You have to actually USE the battery. So, once in a while, shut off the charger and run off the batteries for a short time. You don't need to deplete the battery by more than 5-10% to break down the sulphate. If the battery voltage plunges under light load (receivers, but no transmitters on) then you may need to fully cycle the battery to recover them.Jon

author: trobbins
author_rank: Frequent Contributor
timestamp: April 27, 2021, 11:26:58 pm
content: In addition to Jon's comments, if your wet battery is really wet then it is preferable to use a periodic boost charge to allow gassing to mix the electrolyte volume to alleviate density stratification.Were the batteries initially new ? Were they of sufficient 'quality' to have a manufacturer specification and advise sheet on installation and operation (including charge voltage and max recharge current)?Does your station load ever exceed the 5A charger current limit (ie. do the batteries ever see a discharge condition)?Do you have a low voltage disconnect protection (to avoid battery damage by deep discharge) ? If so then that could be integrated in to a periodic discharge maintenance action.

author: wizard69
author_rank: Super Contributor
timestamp: April 28, 2021, 12:52:00 am
content: lead acid batteries do not last even in automobiles. At least here in the frozen north it is a good idea to install a new battery every 4 years in your car (even 4 years is a stretch). This is something I learned the hard way.As for other applications that may be similar, the large UPS's at work are on a 3 year cycle for replacement. Most of these are still some form of lead acid.As for charging, I'm not expert but I do know that you need to actually use the batteries. As for alternatives, well some of the lithium technologies look to be very interesting. There are a number of lithium solutions on the market that are designed to be easily swapped out with a lead acid. I haven't worked with those either so can't say much however they seem to be becoming popular in the RV world. You may want to look into these RV lithium batteries.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 28, 2021, 02:05:57 am
content: Switch to 4S LiFePO4 with a BMS, it's practically a drop in replacement for 12V lead acid. Or maybe use supercaps if you're just looking to supply peak current rather than use the batteries for backup or portable power.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: April 28, 2021, 02:35:53 am
content: There's an old wives' tale about lead acid batteries stored on concrete don't last very long. Then I remember reading there's actually some thermal gradient issue that can happen, but I don't know if it's true or not. Worth investigating, or just make sure they have free air circulation all around. I get more than 4 years out of all my car batteries in the winters of upstate NY. A car battery is neither continuously floated, nor ever drained very much. They aren't designed for it. I did use some Gates gell-cells for a voltage reference project that were continuously floated at the recommended voltage (which is temperature dependent) and they didn't last nearly as long as I would have expected. Maybe you need an Edison nickel-iron battery!

author: CaptDon
author_rank: Super Contributor
timestamp: April 28, 2021, 02:03:31 pm
content: I do suspect then that the batteries I have used were never really discharged more than a few percent and certainly never dropped below around 13.0vdc even on long weekends of being 'on the air'. I think that an occasional heavy boost charge to help move the electrolyte around as well as the gas bubbling helping to strip small sulphate particles off of the plates sounds like a winner. Also having a deeper discharge on occasion may help. These sound like great ideas. I remember some years ago when a local telephone company sold of their standby batteries that were several decades old and the hams snatched them up. They had huge spacings between the plates and the plates were at least 2 inches above the bottom of the clear cases so that particle buildup would not short the plates. I imagine 20 years later most of the hams still have those telco batteries in use!! The local railroad scrapped a bunch of their huge NiCad wet batteries but they were not of interest to me. They were far to big and needed about 100watts of constant charge current.

author: BradC
author_rank: Super Contributor
timestamp: April 28, 2021, 04:17:12 pm
content: The issue (as already previously mentioned) is you are cooking the batteries. Check the manufacturers data sheet and look at the relevant temperature compensated float voltages. Yes, a periodic bit of use will also help, but the excessive voltage you've used will just cause plate corrosion and kill them dead.I have SLAs here with a 10 year design life that are into their 17th year and still > 80% capacity. The trick is to properly float them (and here that means ~13.5V). What was the float voltage on the label of the SLAs you killed? I'll bet my backside it didn't say "Float voltage 14.2VDC".

author: TheMG
author_rank: Frequent Contributor
timestamp: April 28, 2021, 06:59:05 pm
content: The charging voltages and scheme is a HUGE factor in the longevity of AGM lead acid batteries!As already said, 14.2V is much too high for float charge and will quickly kill the batteries.Ideally the float voltage should be temperature compensated. As well, giving the batteries a bit of a "rest" period (off charge) and even a bit of a drain, once in a while, seems to be helpful.Using a wet cell vehicle starting battery for such applications is also not advised, they aren't designed for that type of use, they are optimized for high starting currents, not for capacity, deep cycling, or standby use.

author: Circlotron
author_rank: Super Contributor
timestamp: April 29, 2021, 01:33:14 am
content: Quote from: CaptDon on April 28, 2021, 02:03:31 pmA long time ago I worked in a local telephone exchange for three months as part of my apprenticeship and we did a load test on one of their three 500Ah 48V battery banks. These batteries were 20 years old at the time and their capacity measured 510Ah. The plates were solid lead, not paste in a lead grid like a car battery. I think that with a car battery if you discharge them to a low point this paste swells up and tears away from the lead grid so electrical connection is lost, along with much capacity.

author: David Hess
author_rank: Super Contributor
timestamp: April 29, 2021, 10:39:22 pm
content: Quote from: CaptDon on April 27, 2021, 04:08:56 pmThat float voltage is too high for sealed gel or AGM batteries.QuoteThat float voltage is too low. Flooded cells should also be periodically balanced at a higher voltage which also stirs the electrolyte preventing stratification in stationary applications.

author: aargee
author_rank: Frequent Contributor
timestamp: April 30, 2021, 12:40:31 am
content: I have a 100AH AGM and just use one of the smart CTek battery chargers to manage it. Still fine after a year, I was over manually mucking about with charge rates, etc.

author: MIS42N
author_rank: Frequent Contributor
timestamp: April 30, 2021, 07:25:25 am
content: yes - lower float charge (13.5), every 3 months balance charge (14.4). You might consider a Lead Carbon battery. More tolerant of partial discharge, longer life. Not a recommendation, just a link to an examplehttps://www.cbb-battery.com/12V-100AH-High-Quality-Deep-Cycle-Lead-Carbon-Battery-NPC100-12-pd44947016.html

author: Robert Smith Eco Warrior
author_rank: Regular Contributor
timestamp: April 30, 2021, 08:14:36 am
content: We are off grid running a flooded lead acid bank of delapidated, knackered batteries.My charge controller has dip switches to select the type of batteries connected. I think I have 'sealed AGM' selected instead of the correct 'flooded' selection. The float voltage was just too high on the correct setting and bubbled off loads of water too quickly and was doing them no good at all.I try to never discharge them deeply (less than 50% state of charge), but they do seem to need some discharging (down to maybe 80% state of sharge) so that the next day the solar panels give them a good bubble and stir things up.I don't know what it is like to use new off grid batteries.I have gone through a few tractor and car batteries and they seem to last a good while as long as they are plenty big enough to cope with cranking an engine for a while on cold mornings. If the battery is a bit minimal on cranking ability then they are soon killed by heavy cranking. They are charged at something like 14v constantly but then they don't get the days and days of constant charging the solar battery bank gets.I haven't worked out the exact recipe for keeping them alive yet, but is something I would like to figure out.

author: bsdphk
author_rank: Regular Contributor
timestamp: April 30, 2021, 02:58:47 pm
content: Quote from: Robert Smith Eco Warrior on April 30, 2021, 08:14:36 amThe BattCON conference archive has a lot of really good wisdom from professionals about lead-acid batteries, highly recommended:http://www.battcon.com/CustomerPapers/PapersList