Best Charger for Lead Acid AGM 12v 100ah battery

Guys hi, help me choose the correct charger to prolong battery life.

We are using 2 12v 100ah parallel connected batteries in our e-billboard bikes.
At the the moment brand new set of batteries lasts for about 4 month, after we have to replace it.
The batteries are charged every day after e-billboard shift is over (new batteries last for 5-6 hours, older ones for 1-2, and than we replace)
(we use Sigmas Tek batteries)

I hope to prolong battery life.
And the first thing i am looking into is chargers.

Thinking about trying this multistep charger.
Would we see improvement in battery life/health?

There is a guy in the UK who strips down his off the shelf motorized wheelchairs and rebuilds them himself. For wheelchairs he no longer recommends using lead acid batteries but he builds his own Lithium Iron (LiFePO4) batteries from off the shelf cells and parts. This is beyond my wife and my ability to do this but if this is something you are interested in you can start at these URLs http://www.wheelchairdriver.com/BM-MK3-lithium-battery-powerchair.htm and http://www.wheelchairdriver.com/lithium-convert-powerchair.htm and http://www.wheelchairdriver.com/converting-to-lithium.htm

If that doesn't sound like something you're interested in he previously recommended a Hyperion 1420i charger but recently discourages using them because Hyperion seems to be getting out of the charger business. I can't vouch for that. I've been thinking of getting a Revolectrix Powerlab 8 when we can afford it. In his forums he now recommends it. It is very versatile and can charge and discharge about any type of battery.

If you have to use lead acid he recommends Odyssey 68Ah PC1500 AGM, Sonnenschein GF12051Y1 Gel or MK Gel. He's run many different batteries hard in his wheelchairs and all the others are bad according to his testing.

Have a look around his site and decide whether he can help you or not.

I would have to agree that in an application such as this, you will get better value (lower cost per cycle) out of a lithium battery. If you're not up to the task of building your own packs, then check out some of the pre-built ones available on the market. There's an 80Ah 12V that would probably suit your needs over at smartbattery dot com. Lithionics is another that I am familiar with. I have heard positive reviews about the latter first-hand from installers and end users. I am in no way affiliated with either of them, nor do I sell their products.

The math on "cost per cycle"...
Lead acid (gel or agm):
30 days x 4 months = 120 cycles
$162 / 120 cycles = $1.35 per cycle, per battery

Lithium:
2000 cycles @ 90% depth of discharge (a conservative estimate - on their site they say 3000 to 5000 cycles)
$1049 / 2000 cycles = $0.52 per cycle, per battery - that's roughly a 61% discount off of those Sigmas Teks.

It's a larger investment in batteries, but long term it's a sound one.

poloman said:

The batteries are charged every day after e-billboard shift is over (new batteries last for 5-6 hours, older ones for 1-2, and than we replace)

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There's your problem. Your problem isn't charging, it's discharging. If you drain lead-acid batteries (even "deep cycle" batteries), you're going to send them to an early grave.

Don't discharge lead-acid batteries any more than 50%, unless it's an emergency. Ideally, discharge even less than that for normal use. Then top up the battery after use (which you're already doing). If you do this, your battery should last a long time.

So you either need a far bigger battery (to last your whole shift), or change batteries during your shift (before they discharge more than 50%), or go to a lithium-ion based chemistry as others have suggested.

poloman said:

.........We are using 2 12v 100ah parallel connected batteries in our e-billboard bikes..............

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Your chargers look to be 24v chargers. I'm assuming you have them connected in series rather than parallel?

Chargers are OK as long as they are smart chargers which can do bulk, absorption, float. I use a 10 amp charger for my 50ah AGM battery.

I agree with WalkIntoTheLight's comments on extending battery life by not deep discharging as much as possible. Maybe what you need is a 2 more batteries to prevent that from happening.

The first thing to do is ignore advice from people who have relatively little clue about what they are talking about and spew often read things like "don't discharge" less than 50% for lead-acid, etc. ... which is akin to don't go swimming right after you eat. Some truth in it, but certainly not the whole story.

Discharging a lead-acid battery below 50% is not going to do any instant damage. What kills a lead-acid battery is not charging it right away when it is discharged.

Now that said, discharging below 20% state of charge "can" get a bit troublesome and below 10% state of charge is starting to push your luck. You will hit a state where initial charge acceptance is low, and it will take time before the batteries even accept charge. charge time will be extended, etc.

Based on your stated power draw, i.e. dead in 5-6 hours, it sounds like AGM is pretty much your only option with lead acid technology. I am not aware of the Sigmas Tek brand, but the off-the-shelf price leads me to believe it falls into the cheap piece of crap category or at least one not designed for truly long life deep cycle operation.

Really good Deep Cycle AGM batteries, i.e. Concorde SunXtender, FullRiver DC series, can do 400-500 cycles, 80% depth of discharge, with 80% of capacity still remaining. They will do 250+ cycles to 100 depth of discharge.

You will need to invest in a good charger. Deep cycle AGM batteries like being charged fairly hard. You need to be charging at 0.2C and a bit higher is not going to hurt. Hence you need a 20A charger, and 25A would not be a bad thing (since you can get bigger batteries in the same physical size).

I can't say I am up on who makes the best chargers today. From the CTEK family, you are into: MXTS 40 ---- The end end of charge methodology of the CTEK may allow you to drop to the 14A version without much in the way of ill effects. I am a bit concerned with some of the reconditioning effects of the CTEK w.r.t. AGM batteries. Flooded batteries take a lot of abuse which can even be beneficial. AGM not so much. For your application, properly applied AGM Boost/Absorption/Float will likely serve you fine, just ensure you have that 20A charge and that you are not taking them off the charger too early. Let the cycle complete or the batteries are toast.

LiFeP04 could certainly be the way to go and in some volume, you may be able to pick up a 100AH LiFePO4 for $600 or so. Will you get 2000 chargers to 90% discharge ... unlikely. You are more likely to get 1000+. That is nothing to sneeze at and they are much less finicky. No worrying about charging right away, no worries about fully charging them, they weigh a lot less (which is really useful on a bicycle with an ad-board), etc. Those 3000-5000 are what highly managed, very high quality automotive are getting. Dig deep into the 90% discharge graphs on what you are likely to buy and you are more into 1000-2000 at 90%-1000% discharge.

A good AGM battery, likely 115AH in your size could run you $250 (may be able to get for less), versus $600ish for the LiFeP04. Treated well the cycle cost could be similar. Treated poorly, the LiFeP04 will last a lot longer.

Now what you have not told us is where you live.

If you live and use these in fairly cool temps, i.e. they may see 0C, then the AGM may be a better choice. If they are regularly seeing 30C+, then go for the LiFeP04. Lead acid hates being hot.

Semiman


Just a quick cursory at those chargers suggest they could be part of the issue. The NBC-24-6 is underpowered and I can see no selection for battery type ... and can't seem to find any information on it at all. The other one looks a bit better. Neither is temperature compensated which could matter depending on how cold it is when/where you are charging.

FYI - at 50% discharge you could hit 1000 cycles with good batteries to 80% remaining life, but that would mean frequent changes ... may not be what you want to do.

SemiMan said:

The first thing to do is ignore advice from people who have relatively little clue about what they are talking about and spew often read things like "don't discharge" less than 50% for lead-acid, etc.

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Followed by...

FYI - at 50% discharge you could hit 1000 cycles with good batteries to 80% remaining life, but that would mean frequent changes ... may not be what you want to do.

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Sounds like you agree that minimizing discharges below 50% is a good idea. Not sure why your initial hostile reaction to such advice, though.

As to shorting the life of a lead acid battery ONE of the major causes is deep cycling them. The deeper the depth of discharge (DOD) the shorter the life. The website I recommended (run by Burgerman) advises keeping the DOD as low as possible by performing opportunity charging throughout the day when practical. It should be noted that that is not sufficient though to prolong their life since lead acid batteries need to be fully saturated charged once a day over night. You should never discharge below 50% if you want them to last. That's one of the fastest ways to send them to the junk yard. Burgerman has years of practical experience with them and has helped design a proper lead acid battery charger. His life literally depends on them. If you want additional advice here's a direct quote from a deep cycle lead acid battery manufacturer "The relationship between DOD and cycle life for ODYSSEY batteries is shown in Figure 1. The lower the DOD the higher the number of cycles the battery will deliver before reaching end of life." They go on to state "Proper charging and DOD are the two key factors that determine how many cycles a battery will deliver before itreaches end of life." This information is on page 11 of Odyssey's technical manual (http://www.odysseybattery.com/documents/US-ODY-TM-001_0411_000.pdf).

Burgerman's advice is that all lead acid batteries are crap (his words). There are no good ones but the best of the worst is the ones that I posted above. The rest aren't even worth bringing home. I can't personally vouch for any battery but his reasoning is credible.

LiFePO4 batteries are the way to go if you can afford the initial cost. Indeed if you mistreat them (or any battery) you can significantly shorten their life but if you use a good quality charger and charge them correctly then you should have no problems. According to Burgerman's calculation the lifetime costs are much lower with LiFePO4 batteries and unlike lead acid batteries you can use all of the energy in the batteries (100% if I understand him correctly). So a 100 Ah lead acid at 50% discharge, which is very deep and shortens the life considerably, gives less than half the usable energy (due to Peukert law) of LiFePO4 batteries during a recharge cycle. LiFePO4 batteries have inherent qualities that allow them to be discharged to that level without damaging them unlike lead acids. The down side is that when LiFePO4 battery energy is used up they don't give any warning like lead acids.

Another good source of battery information is battery university (http://batteryuniversity.com).

SemiMan said:

The first thing to do is ignore advice from people who have relatively little clue about what they are talking about and spew often read things like "don't discharge" less than 50% for lead-acid, etc. ... which is akin to don't go swimming right after you eat. Some truth in it, but certainly not the whole story......

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OK not the whole story, I agree, you want to keep the battery topped up as often as possible. However I have to respectfully disagree with your harshness.

I got the following information from a technical bulletin from East Penn....the manufacturer of the AGM battery I use.



Edit: I refuse to comment further in this thread!

Guys first of all thank you for all the replies,
very helpful! Learning a lot!

hiuintahs said:

Your chargers look to be 24v chargers. I'm assuming you have them connected in series rather than parallel?

Chargers are OK as long as they are smart chargers which can do bulk, absorption, float. I use a 10 amp charger for my 50ah AGM battery.

I agree with WalkIntoTheLight's comments on extending battery life by not deep discharging as much as possible. Maybe what you need is a 2 more batteries to prevent that from happening.

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hiuintahs you are totally right, they are connected in series(made mistake in OP). Making it 24v 100ah.
and 24vdc / 49 amps motor.
So basically i was looking for 24v charger, not 12v.

Installing more than 2 Lead Acid batteries will make load on bike frame too big
(we are already 'feeling 2 batteries = 136 lbs' in increased maintenance cost)

SemiMan said:

Based on your stated power draw, i.e. dead in 5-6 hours, it sounds like AGM is pretty much your only option with lead acid technology. I am not aware of the Sigmas Tek brand, but the off-the-shelf price leads me to believe it falls into the cheap piece of crap category or at least one not designed for truly long life deep cycle operation.
Really good Deep Cycle AGM batteries, i.e. Concorde SunXtender, FullRiver DC series, can do 400-500 cycles, 80% depth of discharge, with 80% of capacity still remaining. They will do 250+ cycles to 100 depth of discharge.

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SemiMan thank you for your long post. Learned a lot!
Just checked those, twice as expensive for 12v 100ah model. Will call company directly and try negotiate on volume.

SemiMan said:

LiFeP04 could certainly be the way to go and in some volume, you may be able to pick up a 100AH LiFePO4 for $600 or so. Will you get 2000 chargers to 90% discharge ... unlikely. You are more likely to get 1000+. That is nothing to sneeze at and they are much less finicky. No worrying about charging right away, no worries about fully charging them, they weigh a lot less (which is really useful on a bicycle with an ad-board), etc. Those 3000-5000 are what highly managed, very high quality automotive are getting. Dig deep into the 90% discharge graphs on what you are likely to buy and you are more into 1000-2000 at 90%-1000% discharge.

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Yes, Lithium sounds like ideal option. And yes, they are much easier on frame. But was not able to find anything reasonably priced for 24 v 100ah battery. Any good/trusted sources?

SemiMan said:

If you live and use these in fairly cool temps, i.e. they may see 0C, then the AGM may be a better choice. If they are regularly seeing 30C+, then go for the LiFeP04. Lead acid hates being hot.

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NYC

The batteries you post say no more than 30 amps, Most Asian Constructed AGM's have this bulk current limitation of 0.3c, whereas top tog AGM like Lifeline AGM say no less than 0.2c, and Odyssey saying no less than 0.4c.

Smart chargers are all Dumb. I've given up on them, no matter how well they are marketed.

i use an adjustable voltage power Supply. RSP-500-15 which will start at 41 amps at any voltage I choose when the battery is still depleted. I use it as a manual charger and change the maximum allowed voltage depending on which battery I happen to be charging at the time and the battery temperature.

Look into a Spring would timer controlling the Meanwell RSP-750-24. This will feed your batteries at their maximum rate, and will take them to the absorption voltage they desire which you set yourself. When amps required to hold ~14.7v drop below ~1 amp terminate the charge cycle, or lower voltage manually to the recommended float voltage.

Any bell and whistle charger marketed these days, despite their marketing department's claims, going to stop short of actually fully charging the batteries. The Lawyers and Bean counters won.

When not returned to a true 100% as often as possible, the battery capacity begins to walk downward, and accelerate.

Feel free to disagree with the harshness, but if one parrots what they read on the internet as fact without understanding the meaning .... then so be it

Great, you posted a cycle life versus DOD from East-Penn/Deka -- Let's see, 0.8 * 200 / 0.5 * 370 = 86.5% ... or you get 86.5% of the cycle energy at 80% DOD as you do at 50% DOD. Considering the posters goal is to have his carts on the road, not returning and charging all the time, then I think the 13.5% loss in total life will be quite acceptable. Now if the poster planned to keep the batteries in an extended state of discharge (which he does not appear to), that would be different, but it's not, so the 50% DOD is really rather meaningless.

By the way Poloman, the Eastpenn Deka AGM Deep Cycles are not that great of a battery. Lifeline (Concorde -- same as SunXtender) is a very good battery. Odyssey are very well rated, but often quite expensive and can actually be more finicky w.r.t. charging. Make sure you get the right one for purely deep cycle operation.

By that logic, you should never run LiFeP04 under 50% either, because it has much higher cycle life at lower DOD too.

WRCSixEight, I can't agree with your statement (or method either necessarily). There are good chargers out there. The higher end CTEK's run a proper and full charge cycle with a proper bulk and absorption charge and a proper current based end of charge. They also, and this is very important, have temperature compensation, which is needed if you are charging in a non-temperature controlled environment, especially if charging in cool temperatures.

In terms of Burgerman, the fact he charges at <0.2C in many of his "tests" shows his lack of understanding of proper cycling charging of an AGM battery. At least he uses a 7A CTEK, but if he was serious, he would not have waited so long to get a 20A Universal hobby charger ... which still does not do temp compensation, essentially if your "vehicle" is left outside. It can take 3+ hours for the internal temp to reach ambient temperature if not longer .... and I have actually designed\built multi-stage microprocessor controlled lead-acid charge controllers with temperature compensation, temp ramp compensation, data logging, etc.

New York City .... are these used year round or only "nicer" weather. LiFeP04, the affordable ones, don't like <0C very much under heavy discharge. You can lose a ton of capacity, more than AGM. The rest of the year, you will appreciate the lower weight. 24V, 100AH you will not find, but you can find Group27 (same as AGM), 12V, 100AH. TopBand (China) makes a tolerable one. I know in China, they are about $550 USD in low (i.e. 10) quantity. You of course need to get them to your place. I am not sure who stocks in the U.S. There are other form factors for 12V, 100AH that may be suitable but likely more money. BYD F12100 is about $850 .... good battery though.


Semiman

SemiMan said:

You will need to invest in a good charger. Deep cycle AGM batteries like being charged fairly hard. You need to be charging at 0.2C and a bit higher is not going to hurt. Hence you need a 20A charger, and 25A would not be a bad thing (since you can get bigger batteries in the same physical size).

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You claim to hate people claiming things without backing it up, so where's your evidence of that? My charger is fairly small, and I have had no problems charging at much slower rates. Anecdotal, yes, but I have a couple of deep-cycle batteries over 10 years old that are still working well and haven't ever been charged at rates higher than 0.1C.

IMO, depleting them lower than 50% charge does more damage than any kind of slow charge rate. Yes, I'm a parrot that likes to state that common belief.

WalkIntoTheLight said:

You claim to hate people claiming things without backing it up, so where's your evidence of that? My charger is fairly small, and I have had no problems charging at much slower rates. Anecdotal, yes, but I have a couple of deep-cycle batteries over 10 years old that are still working well and haven't ever been charged at rates higher than 0.1C.

IMO, depleting them lower than 50% charge does more damage than any kind of slow charge rate. Yes, I'm a parrot that likes to state that common belief.

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For one, we are talking AGM deep cycle, not flooded deep cycle ....which brings me back to my parrot comment. We are also talking regular cycling ... near daily, not 10 years old which means you have likely cycled them rarely and not deeply.

YOO --- is just that, an opinion.


However, if you would like to do some ACTUAL RESEARCH .... you will find that pretty much every deep cycle AGM vendor recommends fairly high charge rates. Take your pick, Concorde, Odyssey, Full River. It helps to maintain cycle life in high cycling applications.

Flooded batteries on the other hand usually do not like high charge rates, though some of the Rolls and Trogan don't mind as much.

Depleting under 50% does not do damage unless you do it repeatedly. Not worse than anything else. By that same logic, I could say discharging to under 10% does worse damage. Where do you pick the point? You could pick 75% ... you tend not to get much sulfation above 75% but you get some.

The worst damage to a lead acid battery is being left in a state of discharge and the lower the state of discharge it is left in the worst it is. However, in this case we are not leaving it in a state of discharge, we are charging it every night. After that, the worst thing you can do is not charge it completely and properly which you are advocating ...

Semiman

SemiMan said:

For one, we are talking AGM deep cycle, not flooded deep cycle

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Yes, AGM is the batteries I use. I don't have a charger to charge them at 0.2C. I can only charge at about 0.1C. Granted, you're right that I don't cycle them regularly.

However, if you would like to do some ACTUAL RESEARCH .... you will find that pretty much every deep cycle AGM vendor recommends fairly high charge rates.

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I'm not the one making the claim. That's why I asked you to post a reference. I'm not stating you're wrong, but I have no evidence to believe your right, either.

Depleting under 50% does not do damage unless you do it repeatedly. Not worse than anything else.

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Of course it does damage, even if you do it once. It just doesn't do a lot of damage. But add that damage up from doing it many times, and it's killing your battery. I pick 50% as the number, because that's what off-the-grid systems suggest. (Actually, many suggest don't deplete below 70% during normal use, but that's getting useless for the OP's use.)

The worst damage to a lead acid battery is being left in a state of discharge and the lower the state of discharge it is left in the worst it is.

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Yup.

WalkIntoTheLight said:

Of course it does damage, even if you do it once. It just doesn't do a lot of damage. But add that damage up from doing it many times, and it's killing your battery. I pick 50% as the number, because that's what off-the-grid systems suggest. (Actually, many suggest don't deplete below 70% during normal use, but that's getting useless for the OP's use.)
.

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Discharging them at any level does damage, period. However, rather pointless not to discharge them since that is what you bought them for. In a heavy cycling application, 80% DOD discharge reduced total energy life of the battery by only 13.5% over 50% DOD ...... which when you need as much life as possible is rather meaningless.

50% is recommended for solar as often batteries will sit for a long period of time in a partially discharged state. That and most sites are written based on what people have read, not from actual testing and research or knowledge, because for most solar installations it is a much more complex analysis and "rules of thumb" are a great way to kill very expensive batteries or leave yourself in the dark ....literally.

I have taken AGM batteries regularly below 50% and even left them there for periods of time, but they always get charged completely when charged, and they also get a conditioning charge if I know they have been in an "abusive" discharge situation. Doing that, 5+ years is still possible ... quality battery of course.

Wow... I had no idea that lead-acid charging was such a contentious topic.

mellowhead said:

Wow... I had no idea that lead-acid charging was such a contentious topic.

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Like any other topic, conjecture and reality

mellowhead said:

Wow... I had no idea that lead-acid charging was such a contentious topic.

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The topic isn't contentious, just some people. LOL

SemiMan said:

Like any other topic, conjecture and reality

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For sure. Experience goes a looooong way with lead-acid batteries. Book-learnin' just isn't the same.

poloman, if you'd like to chat one-on-one about lead-acid batteries and charging, PM me. It's what I do for work. All day, every day - batteries batteries batteries