[TheSGC]

How fast of a charge can flooded batteries take? For example, a US 8VGC-XC? I know they recommend C/10 or 17 AMPs, but right now I can only give them 13 AMPs. I have read a few hints here and there about some people pumping 30 AMPs into their 8VGCs using a Manzinita charger, but no real docs and it that is good or not.

The reason why I am asking is that I am developing a fast charging station to pump in at least 17 AMPs into my pack, but more like 20-21 AMPs would be nice. I am trying to find ways to shorten my charging time at school, but I don't have access to anything better than a 120v 20 AMP plug. So I building a battery bank station that gets charged during the night, then dump power into my EV during the day, hopefully taking my charging time from 6.5 hours down to 3 or so.

I am trying to make a list on what charging currents different batteries can take, and I would hate to murder my pack with too much current. And yes, I am designing a micro controller based charging unit to control everything.

 

[dtbaker]

How fast of a charge can flooded batteries take? For example, a US 8VGC-XC? I know they recommend C/10 or 17 AMPs,

First... you have access to a 220v/20amp panel?

Second, have you contacted the tech guys at US Battery? I have several times when I was attempting to repair a split battery casing which got dropped on delivery, and they were GREAT. They can probably give you a solid answer on how much you can dump in without damaging anything.

 

[TheSGC]

First... you have access to a 220v/20amp panel?

Second, have you contacted the tech guys at US Battery? I have several times when I was attempting to repair a split battery casing which got dropped on delivery, and they were GREAT. They can probably give you a solid answer on how much you can dump in without damaging anything.

No, I don't have access to a 220v/20A panel. If I did, a nice massive Elcon would work nicely. My plan is to build a high voltage "dump pack" that get's charged at night via individual chargers, then when I arrive in the morning I can dump in the juice. The station I am building will be capable of 100+ AMP charging current, but 17A to 30A is my target range. I have some crazy plans for this, but before I get too far I need to make sure I don't blow up my batteries.

I have sent them an e-mail, but it's Sunday so I don't expect anything for a while.

 

[jackbauer]

The main issue with fast charging a flooded cell is plate area. When a cell is charged the acid is basically being forced out of the plates and into solution. This is why the specific gravity increases during the charging process. Its not a linear process and some areas of the plates will expel acid quicker than others and start generating heat and gassing. Also some cells will charge quicker than others even in the same battery.

I have charged my pack of odyssey agms at over 180 amps which results in a 15 minute charge. Sort of like "splash and dash" at a filling station. This requires a 415v 3 phase 60amp supply.

 

[rmay635703]

C/5 is the upper limit on most batteries, that said it may promote longer life (aka if you overdischarge a lot) or it may reduce life (if you never have low SOC and dump charge)

Generally dump charging (beyond c/5) is safe if the source is another set of batteries of the same voltage because the voltage and current taper almost ideally.

Basically you can technically dump in tremendous current levels to start with but those levels need to ramp down rapidly as voltage increases and the batteries SOC increases.

In otherwords 200amps for a second or two likely won't hurt anything and may serve to desulphate and mix electrolite but battery temperature must be low enough or it will age and warp the battery rapidly.

Thing is for longer than a seconds your current must rapidly approach the C/5 because the battery voltage skyrockets and because temperature will skyrocket and the cells will start to gas very rapidly instead of charge.

So all I am saying is, don't charge too fast in hot situations (either battery or environment) and remember that your current level must be voltage limited like an alternator.

So in other words, It is normally safe, although not ideal (less efficient) to charge like an alternator in a dump charge situation.

I personally have used dump charges when I overdischarge a battery or reverse it and I believe I have saved some batteries by doing that but as a day to day charge method your batteries might be clean inside but will likely crumble more rapidly. (AKA you are trading sulphation failure for deterioration failure, not sure which is really better)

Oh and on a side note my Greensaver 250ahr gel batteries can be charged at up to 60amps (initially at least)

Cheers
Ryan

 

[TheSGC]

This is good info. I will have both current and voltage limits, basically a dc to dc charger with extras. My plan is to build a test unit that will give me 17 to 30 AMPs via a 132v pack, and later a 216 v pack. My hope is to build a trailer based setup that can be placed in strategic locations to act as a charge station, for "research", aka my shopping needs.

 

[DIYguy]

This is good info. I will have both current and voltage limits, basically a dc to dc charger with extras. My plan is to build a test unit that will give me 17 to 30 AMPs via a 132v pack, and later a 216 v pack. My hope is to build a trailer based setup that can be placed in strategic locations to act as a charge station, for "research", aka my shopping needs.

you might want to think about AGM's if you wanna dump high currents.. floodies can't take it too high for too long. AGM's have much lower internal resistance.

 

[TheSGC]

you might want to think about AGM's if you wanna dump high currents.. floodies can't take it too high for too long. AGM's have much lower internal resistance.

Yeah, AGMs would be nice but Lithium's be better.

Even if I get just the 17 AMPs, that means a full charge in less than 4 hours for me. I am designing this to allow for 100+ AMPs because I like over kill. If I make this big and powerful, for more than my EV, I might be able to get research credit through our Electric Vehicle Center at school. I figure if I can design it to be compatible for my EV and the Solectria's at school, things should work in my favor.

 

[TheSGC]

I heard back from US Battery and I can charge all I want as long I the voltage is slightly lowered and the temp remains below 120F. US Battery recommends a standard charge at 2.58 v/cells but I like 2.4 v/cell so my plan should work.

I don't plan on taking a day to charge the pack, it would be charged by a normal 110v 15A plug. My goal is to give me a dump station so I can quickly dump in 30 or 40 AH into my pack to extend my daily trips.

For instance, this Wednesday I have some work to do that is an extra 12 miles round trip from school that is the opposite direction from home. So instead of coming back to school and charging for 4 hours, I could come back for just 1 hour, dump in the 34 AH, eat dinner then be on my way. I actually have to drop my EV off at my dad's work, plug it in to charge and take my other car (dad drives it now) to work for the afternoon, then swap on my way home.