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Discussion Starter · #1 ·
Hello,

I am looking to charge 4 to 6 AGM batteries in series as fast as possible (Decreasing life cycle is not of huge concern).

Does anyone know of a AGM lead acid fast charger that has a variable voltage input (up to 72V) and variable current input (up to ~50A), that can fast charge? Preferably one that also has some preprogrammed charging algorithm.

Budget would be for under $1000.

Thanks.
 

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not a great idea to charge AGMs 'fast'.... venting is not something you want to be near.
I have the same warning. I had a bad agm 12v battery in a pack of 5 on charge at 30A. It started venting like a volcano and luckily I was right there to turn off the charger and run for cover. Being around a renegade lead battery and a spark is almost the same as throwing a match into an "empty" gas tank.

francis
 

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Discussion Starter · #4 ·
I didn't realize venting was still an issue with a "smart" charger that had a preprogrammed algorithm and that was able to measure voltage.

I will be using a series string of 4 Odyssey Extreme Racing 30 batteries. I would like to charge these as fast as possible. What would be the highest amperage I could safely put into these? I would like to charge these in around an hour to an hour and a half. (80% DOD to ~5% DOD)

Obviously safety is a big issue but battery life is not.
 

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Actually, unlike floodies, you can charge AGM's at a much higher rate. Their internal resistance is lowest of all pb. There are different plate chemistries also...but in general as long as you don't let the battery boil (over 13 volts) you'll be fine. Emphasis should be on upper voltage not amperage.
 

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Obviously safety is a big issue but battery life is not.

You really need to check with the battery maker, but DIYGuy is correct - you can typically charge AGMs at a much faster rate than the typical flooded battery. 4C is usually the maximum rate, however, and, yeah they can be, uh... "exciting" if they are abused too much. YMMV.
 

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oh yes, was going to mention...if you do charge at high rates... a temp probe is a good idea...particularly if your charger is designed for it's input.
 

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I've run Hawker Genesis 13ah and 16ah in competitive motorsports applications. They can take a lot. If you haven't, check out
http://www.odysseyfactory.com/documents/US-ODY-ER-OM-001_1008_rev.pdf
for some information. They do warn of going over 15volts. I normally charge with a 'bad boy' charger. Crank the voltage to deliver 30 amps (all the charger would do, plus the generator would grunt). Then keep turning the transformer up at the current drops and voltage rises. But if you turn your back, the voltage can rise up above 15 pretty quickly.
Check out odyssey's chargers at
http://www.odysseyfactory.com/documents/US-ODY-ULT-007_0610_low.pdf
The charging algorithm there is what you want. You can find or build a charger that does that algorithm. Notice that the MINIMUM charging current is .4C. So 12A min for your 30ah battery.
More is often better. Faster charging will heat up the batteries, which you may want, as it will cause the battery to deliver more power when discharged.
Guess you didn't say what your application, but I'm thinking high output and fast recharge, then repeat.
I seem to recall a white zombie store about dump charging hawkers genesis batteries at about 100amps?

Good luck.

Darin Gilbert
Bad Fish Racing
 

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You really need to check with the battery maker,
Agree 100%, but the max amount varies quite a bit between manufactures C/8 to C/4

but DIYGuy is correct - you can typically charge AGMs at a much faster rate than the typical flooded battery. 4C is usually the maximum rate
I assume this is a typo and you meant C/4. I do not know of any battery that can be charged at a 15 minute rate.
 

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I assume this is a typo and you meant C/4. I do not know of any battery that can be charged at a 15 minute rate.
Not a typo. Concorde is at least one manufacturer that says you can charge during the bulk phase at 4C (even 5C for certain sizes).

I just double checked this because you had me worried that I might have misremembered this but it seems that, yes, many of the Concorde batteries can accept very high rates of charge ranging from 1C to 5C.

A cursory search of teh interwebz reveals that it is almost standard practice now to charge AGMs at as high a rate as is practical. As long as gas recombination can still occur why not?
 

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I've charged my old 120v pack of odyssey pc2150 agms at over 250amps. Damn things just sat there looking at me saying "Is that all ya got?":D
 

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Not a typo. Concorde is at least one manufacturer that says you can charge during the bulk phase at 4C (even 5C for certain sizes).

I just double checked.....
Have you got a link?

I am familiar with Concorde Sun Extender product line and they reccomend C/5 and can tolerate inrush as high as 5C. But inrush is not constant current.

Perhaps their aircraft or military line can handle a constant 4C, but I do not see that as a reality for say a 144 volt 100 AH pack as that would require a 60 kw charger. No standard residential 200 amp service is capable of doing that. You would blow the transformers off the POCO poles :D
 

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Have you got a link?

I am familiar with Concorde Sun Extender product line and they reccomend C/5 and can tolerate inrush as high as 5C. But inrush is not constant current.

Perhaps their aircraft or military line can handle a constant 4C, but I do not see that as a reality for say a 144 volt 100 AH pack as that would require a 60 kw charger. No standard residential 200 amp service is capable of doing that. You would blow the transformers off the POCO poles :D
It was discussed here... check my post #15... there is also a link there...
Tesseract is right... it is more and more common with AGM's. The racing guys have been doing this for years (higher than small fractional that is). They have very low resistance, this is the main point. There are also some plate alloys that are said to do better with higher current charges.... I can probably find that one too ... if I have to.... lol...
http://www.diyelectriccar.com/forums/showthread.php?p=151095&highlight=Concorde+AGM#post151095

Hey Sunking... u actually read that post back in Nov of 09.... :) Jeff has a better memory than you... lol
 

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They have very low resistance, this is the main point.
I thoroughly understand the the low resistance nature of AGM. It is more beneficial on the discharge side of the equation because it can deliver higher amounts of current without as much voltage sag compared to FLA... On the charge side it is more efficient than FLA

The real problem I see with high charge rates is unrealistic charger sizes, heat, and pre-mature triggering of the Bulk and Absorption cycles in a 3-stage charging algorithm.
 

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The real problem I see with high charge rates is unrealistic charger sizes, heat, and pre-mature triggering of the Bulk and Absorption cycles in a 3-stage charging algorithm.
Ya, I can understand the unrealistic sizes, particularly with conductors... not sure about the other but no matter... I think the important message here for users is not that they can charge at 4C...but that they are not mislead to think AGM must be charged at the same rates as floodies and if they want to capture high regen amps or charge with 50 to 100 amps, it will not be a problem. Cheers.
 

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Have you got a link?
P. 241 of the book Valve-Regulated Lead Acid Batteries by David Rand.

I am familiar with Concorde Sun Extender product line and they reccomend C/5 and can tolerate inrush as high as 5C. But inrush is not constant current.
Caveat: I am not familiar with ANY lead-acid batteries. I use them, I loathe them, but I do know this: old style gel and new style AGM designs are just worlds apart. The Sun Extender line seems singularly unsuited to EVs so not really applicable here, however.


Perhaps their aircraft or military line can handle a constant 4C, but I do not see that as a reality for say a 144 volt 100 AH pack as that would require a 60 kw charger. No standard residential 200 amp service is capable of doing that. You would blow the transformers off the POCO poles :D
I think I saw this spec in their Lifeline series... Anyway, I agree that it isn't really practical to charge a 14.4kWh pack at 4C, but you CAN, apparently. You just need to keep a sharp eye on the voltage is all and limit the high rate charging to the bulk phase.
 

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they want to capture high regen amps or charge with 50 to 100 amps, it will not be a problem. Cheers.
Point taken, I overlooked the REGEN aspect. Now with that said can AGM handle REGEN adequately? I have always been under the impression the best tool for REGEN is SuperCaps to absorb the high impulse (Buffer) and slowly release it back into either the drive train or battery.
 

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Caveat: I am not familiar with ANY lead-acid batteries. I use them, I loathe them, but I do know this: old style gel and new style AGM designs are just worlds apart. The Sun Extender line seems singularly unsuited to EVs so not really applicable here, however.
You are correct the Sun Extender are not suitable for EV as they are not designed for high discharge rates. They are designed with thicker heavier plates to extend cycle life at lower discharge rates.

That is the crux for any lead acid battery technology. If you want cycle life you have to have fewer but thicker more massive plates. To have high discharge currents you need more thinner plates to increase surface area, but have to sacrifice cycle life. You cannot have your cake and eat it too.
 

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Point taken, I overlooked the REGEN aspect. Now with that said can AGM handle REGEN adequately? I have always been under the impression the best tool for REGEN is SuperCaps to absorb the high impulse (Buffer) and slowly release it back into either the drive train or battery.
Well, I can't speak from experience on regen.... and I know what you mean about caps...but I think there are lots of guys who can attest to fairly high current capturing with regular floodies even. I think the short time frame of regen helps. I think that this would only be better with AGM's (vs floodies)
 
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