Lead-Acid Battery Charger/Analyzer - Page 1
Forum section: electronics / testgear

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 02:08:37 am
content: The reason why this is in the test equipment section should become apparent...I use quite a few lead acid batteries of various types in my R&D work, ranging from flooded "car size" deep discharge cells to small AGM "security batteries". For most charging, I have several chargers floating around, mostly of the trickle/maintenance type since I rarely cycle the batteries- they're more used for compatibility testing.Occasionally I feel that I need to get a better picture of the health of a battery. For instance I have a slightly older 7Ah 12V AGM battery on my bench right now that I accidentally left connected to a circuit over a few days. This of course drew far more out of it than I would normally like to see happen. In other words: it's been abused by over discharging it. In this case, I'd really like to be able to charge it with a really good quality charger, and then test it to verify it's still behaving like an AGM battery should.My current method is to trickle some voltage into the battery to bring up the voltage to where it can be charged, then I use a B6AC 'hobby charger' in lead-acid mode to charge it. If I'm concerned about the health, I may also use the B6AC to discharge it back down to the appropriate discharge cutoff voltage. If the mAH drained is reasonable for the battery capacity, I then call the battery 'good' and charge it back up.Although this works, I really don't feel that these are the 'right tools' for the job. The operation of the B6AC is a lot more manual than I'd like, and there really isn't a good load tester. I also am not convinced it does anything other than a voltage+current limited charge (i.e. no 3 stage charging). I have other more sophisticated chargers, but they're primary designed for automotive batteries, so charging a small 7ah AGM battery seems risky (even if the charger has apparently compatible settings).... And, none of them have what I consider a decent load and/or battery condition tester.I'm hoping someone here is familiar with a decent, reasonably priced tool for doing this type of battery work... That is, hook a smallish AGM battery to it, select voltage, capacity and type of battery - and have the unit both do a correct charge and ideally do some sort of battery health testing. In my dreams, when it was done, I'd end up with a fully charged battery and a report on the battery condition. Don't know if this is reasonable or not. I also guess I could live with two separate units - a good charger, and a good AGM analyzer.Anyone familiar with a unit like this? Because this is a long-term-use tool spending a fair bit of money on this isn't out of the question...-forrest

author: uncle_bob
author_rank: Unknown
timestamp: February 06, 2016, 02:26:19 am
content: HiThere aren't a lot of people trying to look carefully at small cells. For most of the population, they are a "stopped working, throw away" sort of thing. I suspect it would be easier to build a tester than to find one for sale.Bob

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: February 06, 2016, 02:47:51 am
content: I have the NOCO Genius G3500 for topping off new batteries before I hook them into my test gear. The latest version has a repair option, but mine doesn't have it so I can't say how well it works. I am considering getting a second to test and charge the banks of my Fluke 732A's.I also have a DC electronic load that I can connect to the batteries and determine if they meet the advertised Ah rating.

author: KE5FX
author_rank: Super Contributor
timestamp: February 06, 2016, 03:51:58 am
content: Quote from: uncle_bob on February 06, 2016, 02:26:19 amIt doesn't sound like he's looking at individual cells, but at 6V or 12V sealed LA batteries. I'm sort of in the same boat, with a whole shelf of 7AH and 12AH batteries whose condition I'm never entirely sure of. It would be neat to have a turnkey gadget that would test and document their behavior under load.For instance, every once in a while, a UPS dies and I'm tempted to salvage the battery. I usually don't bother, on the grounds that I don't know how much remaining life to expect.

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 04:12:28 am
content: Quote from: KE5FX on February 06, 2016, 03:51:58 amThat's pretty much exactly what I'm talking about. There are tools which are designed for the 80Ah+ batteries, but most of them don't seem to do a good job of supporting the lower end batteries - the 'trickle' charge on many of them are higher than what the bulk charge should be on a typical SLA. I understand that these are low-cost batteries, but you'd think with as many of them are manufactured and used every year, that there would be enough interest in reuse of these that someone would make a decent tester.-forrest

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 05:07:56 am
content: The simplest way to check a la battery is to charge it to 2.5v per cell than put a load on it to remove the surface charge than check the voltage if it is not 2.2v per cell it is bad. (6 volt have 3 cells 12v have 6 cells)Best way is to check each cell but that is not possible with most modern batteries. Flooded la batteries can be tested with a hydrometer should be 1.265 spg. and all cells should be within 5-10% if not it is bad.more infohttp://batteryuniversity.com/learn/article/testing_deep_cycle_lead_acid_batteries

author: amirm
author_rank: Regular Contributor
timestamp: February 06, 2016, 05:28:51 am
content: Recommend getting one of these smart chargers:http://www.batteryminders.com/They work excellently on small or big batteries. They also desulfate using high frequency pulses. You can get them with temperature compensation and their self-diagnostic is pretty good too. It will occasionally stop charging and test the cell and will alarm if it finds the cell not holding charge.

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 05:59:19 am
content: more info. maybe more than you need.I owned and worked for custom battery shop for 15 years although this was in the late 1960's to 1980. We built batteries from20-700 amp hr. I think I have some experience.https://www.usbr.gov/power/data/fist/fist3_6/3-6.PDbill

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 06:01:04 am
content: another link.http://docslide.us/documents/13th-bci-battery-service-manual.html

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 06:03:14 am
content: Quote from: amirm on February 06, 2016, 05:28:51 amI've been using various battery minders as part of my arsenal for a while, although it looks like they've released a couple of newer, fancier models since I looked last. My set of 80Ah flooded cells are actually maintained by a set of 4 of these - one per battery. When I last looked, they were basically all float chargers - now it looks like they may have some more sophisticated ones.

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 06:18:27 am
content: A Desulfator is not necessary if you do not discharge the battery beyond 2.0v per cell, A Desulfator will cause the positive plates to shed material and shorten the life of the battery.Ok please ignore my comments because I don't know what I am talking about

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 06:30:15 am
content: Quote from: bills on February 06, 2016, 05:07:56 amI've been following this basic procedure for quite some time... i.e. charge fully, either apply load or let it rest (to let the chemistry stabilize), then check the open circuit voltage. That will generally tell you if you have a bad cell. But, that doesn't necessarily give you a real picture of what condition the battery is in.So far, the best thing I've been able to do is to float the battery at the recommended float voltage for an extended period (to ensure a full charge). Then, discharge at the 20hr rate and see how many amp hours I get out of the battery. Then re-charge.

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 06:35:17 am
content: When you discharge at the 20 hr rate what amp do you use ?100 AH / 20HR =5 Amps

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 06:40:12 am
content: Quote from: forrestc on February 06, 2016, 06:03:14 amOk, I need to revise my response to this... After I couldn't find the model I was looking for I went out and actually looked at the chargers on the deep discharge batteries and they are Battery Tender brand.www.amazon.com/gp/product/B000CITKCEThey've been running with no issues for at least 5 years, and I know for a fact those batteries are still in great shape.

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 06:47:34 am
content: Quote from: bills on February 06, 2016, 06:35:17 amNo 7Ah/20Hr=~350mA.Most recently I've been using the skycharger B6AC's discharge function which counts mAh, but I've also been known to hook one up the DC electronic load on the bench and time it manually. The DC load could definitely do the 5A for 20 hours though...http://www.circuitspecialists.com/dc-electronic-load-csi3711a.html

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 06:49:13 am
content: And they will for many years as long as you don't go below 1.9-2.0 v per cell the float charge should not exceed 13.8-14.0 v for a 12 volt battery.you will not have full capacity but you will have a long life.

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 06:52:36 am
content: Quote from: forrestc on February 06, 2016, 06:47:34 amMy example was for a 100 ah battery.A 7 ah battery discharge rate would be 350 ma. as you have said.

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 06:55:33 am
content: With a 7 ah battery it should be 1.9-2.0 per cell after 20 hr's @ 350 mah.

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 06:59:42 am
content: If you go below 1.9 v per cell you are damaging the battery.

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 07:01:59 am
content: Quote from: bills on February 06, 2016, 06:18:27 amI don't have the background to talk about the long-term effects of a desulphator, but I will say that I am skeptical about the usefulness of it to restore much of the use of the battery.I do have a desulphating charger for those times when I think it might be useful, but so far I can't say I feel that it has helped (or hurt) much. I've sort of reached the conclusion that the best option is to keep batteries full, and promptly recharge them when discharged is the best policy. But, it seems that even though I try hard to follow this advice, sometimes it just doesn't work, and then I feel like I need a good charger and tester is needed. A perfect example is the 7AH battery I'm dealing with today - I thought I had removed the load, but I hadn't. Several days of a <1W load later, and I had a battery with a voltage just over 4V instead of 12V. (And no, it doesn't look like it survived).-forrest

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 07:10:59 am
content: Quote from: bills onTodayat 05:55:33 PMActually, per the PS-1270 datasheet, the termination voltage should be 10.5V total. (http://www.power-sonic.com/images/powersonic/sla_batteries/ps_psg_series/12volt/PS-1270_11_Feb_21.pdf)The procedure I go through when I do this is:1) Ensure a 20*C room and battery.2) Allow to fully charge. Generally this means float at around 13.5-13.8 for an extended period, after the battery is full.3) Discharge at 0.35mA until battery voltage under load reaches 10.5V. Compare time to reach this threshold to the expected 20 Hours.-forrest

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 07:14:02 am
content: As i have been saying if you discharge a la battery below 1.9 v per cell you are damaging it.BTW the 1.9 v is open circuit after load is removed and the battery is allowed to stabilized.Honest been there done that.

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 07:24:58 am
content: Sorry guy but a full charge is 2.5v per cell @ 350 MH not the float charge.the float charge is to keep the battery from losing material from the positive plates .the capacity of the battery is determined by the sq in of the positive plate when the positive plates lose material the battery loses capacity IE: ah.

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 07:30:15 am
content: Please read or at least skim over the links I have posted.I have no problem discussing this with you and I am happy to continue even if you don't read them.regardsbill

author: forrestc
author_rank: Unknown
timestamp: February 06, 2016, 08:45:30 am
content: Quote from: bills on February 06, 2016, 07:24:58 amUm... please carefully read this phrase from a prior post:"Generally this means float at around 13.5-13.8 for an extended period, after the battery is full."What I mean by this:Step 1: Charge battery. Generally this means charge at a suitable charging voltage (I typically use 14.5V for a 12V cell) with an appropriate current limit (aka 0.3C or less - I prefer something around 0.2C) until the current drops to pretty much nothing (<0.01C is pretty common). I usually use a 'normal' charger to do this, although I'm not sure I really have one that I can trust (which is part one of my request here).Step 2: Switch to a float charge for an extended period, to permit the battery chemistry to settle, and also to maintain a full state of the battery. These small AGM's tend to have a fairly bad self-discharge rate, dropping to 80% of capacity in only 6 months at 20*C. I'm also never quite comfortable with the actual state of charge of a battery after a 3 stage charge so the float helps give the battery time to distribute the charge throughout the chemistry. Generally, once the current drops to 0.001C at float voltages the battery is actually full.My original question is 100% based on the fact that I understand fully the complexity of dealing with battery charging and testing. I can do it myself and get it right, if I have time to pay attention to the details. In the end we're talking about a $20-30 battery here, and my time is worth something. If I can buy a charger which gets things done right (meaning bulk and saturation charges correctly, followed by a float) for these smaller AGM batteries, and hopefully with an appropriate load tester which does a good job of some sort of testing the state of health of the battery, then I can feel good about just hooking a questionable AGM battery up to it and let it alone (in a suitably safe location) for the couple of days it takes to do this properly. Ideally it would all be automatic - but even if I have to switch from charge to load that would be better than continuously monitoring it..If you want to get into the details, I can talk state of charge methods, including my preference which is Coulomb counting, the effects of temperature on battery charging, how stupid people believe they need to equalize batteries at nearly 3.0V per cell (true customer story - what do you mean you're equalizing the 48V array at 72V? And you're doing this how often?), the esoterics of which lead acid plate material is better for cyclic vs standby operation, and on and on and on. There's a reason why I refer to a battery datasheet (where available) - I understand quite deeply that the specific design of the battery can greatly affect how you have to charge it and it's performance under load. I also understand the games that battery manufactures sometime deploy to make their battery look better such as playing games with temperature (for instance, specifying the shelf life at 5*C and the capacity at 30*C). But, please don't assume I don't know what I'm talking about.All I was hoping for was to find a charger that I can trust to do the right thing and which understands how to deal with a standby-service small-capacity AGM battery (and even better if it is more universal) in various states of discharge (all the way from way overdischarged to almost full). I can pretty much guarantee this skycharger doesn't do the right thing, but it has the benefit of being better than anything else I've found, mainly because I can usually manipulate it into doing the right thing if I hover over it.I would *LOVE* to be able to find something which I could say "12V, 7ah, AGM", verify the numbers for charge voltages match the datasheet, and hit start. 30 hours later, I have a battery which is as charged as it's going to get, and an indication of state of health. I realize this is probably unrealistic, but there has to be something better than what I've found. Just simple things like counting coulombs into the battery and making sure that the current is dropping as (within some range) is expected for the battery capacity would be greatly appreciated.So do you have a recommendation for a charger and a state of health (not State of Charge) analyzer?

author: uncle_bob
author_rank: Unknown
timestamp: February 06, 2016, 04:16:05 pm
content: Quote from: forrestc on February 06, 2016, 08:45:30 amHiSo back to the top. No, they don't make those for small cells. The only way to do it is labor intensive. The reason is simple ... there is no market for them. Why there is no market, that's a very different question.Bob

author: bills
author_rank: Frequent Contributor
timestamp: February 06, 2016, 10:04:05 pm
content: Ok, how about one of thesehttp://www.ebay.com/itm/NEW-CTEK-MUS-4-3-12-volt-Smart-Battery-Charger-Recommended-for-all-Odyssey-AGM-/231817205465?hash=item35f961d6d9:m:mjCwLbfMFRMYtbxVdxFDbnA&item=231817205465&vxp=mtror check herehttp://picclick.com/?q=agm+battery+charger

author: Zeecue
author_rank: Contributor
timestamp: February 06, 2016, 10:26:20 pm
content: Quote from: bills on February 06, 2016, 10:04:05 pmThe ctek Chargers only tell you what charge its using not any battery performance related info.You can hook up a dead 12v battery with multiple cells dead, and the ctek will happily charge it thru the different modes, and then show that the battery is "charged".

author: forrestc
author_rank: Unknown
timestamp: February 07, 2016, 03:18:30 am
content: Quote from: uncle_bob on February 06, 2016, 04:16:05 pmWhich is sort of where I was before I asked the question. I was just hoping that there was a little manufacturer somewhere which did this type of thing. Oh well....