# Can Batteries charge up Too FAST ?



## Rick (May 10, 2002)

Can Batteries charge up Too FAST ? Is it harmful to the batteries NOT to discharge to 80 percent each week or more? If it is OK , would the equalization process still be needed each 30 days or should we spread those occasions out to every 2 months, or until the specific gravity readings are below 1.265 - 100 per-cent according the specs from Trojan.

We have 4 Trojan L16 Batteries Powered by 4, 125 Watt Mitsubishi Panels. They are dedicated to our Truckers 12 volt refrigerator at present. 

Our Xantrex 35 Amp Controller has charged them back up to 13.5 volts 7 out of 10 days. )

The bank has never been below 85 percent of capacity - 12.47 volts and 1.239 specific gravity. 

Our experiment with the fridge is working out well so far. It has been Sunny most days - about 7 of 10 days. We only had 3 of 4 panels until we liberated the 9 non-functioning cells in panel 4 yesterday. 

Rick


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## mrpink (Jun 29, 2008)

lead acid batteries do not develop a memory. there is no need in deeply discharging them doing so will shorten there useful life. I do believe they can be charged to fast if I remember correctly.

greg


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## PyroDon (Jul 30, 2006)

in answer to the question of "can a battery be charged too fast " 
the answer is yes and can be an explosive venture . 
charging too fast or over charging will boil the battery out. 
Be sure to keep a close eye on the fluid levels


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## 12vman (Feb 17, 2004)

What's the specs on the fridge?


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## artificer (Feb 26, 2007)

Take a look at this FAQ. Its a good start to learn about batteries.

This is what they have on charging:
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Most flooded batteries should be charged at no more than the "C/8" rate for any sustained period. "C/8" is the battery capacity at the 20-hour rate divided by 8. For a 220 AH battery, this would equal 26 Amps. Gelled cells should be charged at no more than the C/20 rate, or 5% of their amp-hour capacity. The Concorde AGM batteries are a special case - the can be charged at up the the Cx4 rate, or 400% of the capacity for the bulk charge cycle. However, since very few battery cables can take that much current, we don't recommend you try this at home. To avoid cable overheating, you should stick to C/4 or less.

************************************************

Lead Acid batteries will last longest if they are trickle charged, and not used. (0% DOD) The closer you get to this, the longer your batteries last. Intentionally discharging the battery only shortens the life of the batteries.

Michael


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## Rick (May 10, 2002)

Thanks all.

Greg and Michael - You gave me the answer I was looking for, even though I failed to ask my question clearly. I wanted to make sure I did not need to more deeply discharge my batts to insure their longevity. 

Michael provided me with this link recently. Our fridge is similar to the one at the top of this link. I can't get to the back of mine right now but I recall it does not rate amps or watts.

http://www.truckfridge.com/cr49.html

I think 13 watts avg/hr is about right. I will hook up a triametric meter before Summer ends, and know more.

Rick


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## 12vman (Feb 17, 2004)

What's the distance between the controller and your panels? What gauge wire do you have installed between the two? Is the fridge the only thing that you have connected to this system? How often does the fridge kick on/off? What voltage levels do you have the controller set for bulk/float charge?

Could you explain this a little more..
"We only had 3 of 4 panels until we liberated the 9 non-functioning cells in panel 4 yesterday."

You're not going to charge your battery too fast if your controller is set up properly. You can over voltage them and make them boil big time if the bulk charge level is set too high and lose the benefit of the float charge if the level is too low.

Equalization wouldn't be necessary being you are cycling them daily as you are. I would just shut that function off if you could.


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## Rick (May 10, 2002)

12vman said:


> What's the distance between the controller and your panels? What gauge wire do you have installed between the two? Is the fridge the only thing that you have connected to this system? How often does the fridge kick on/off? What voltage levels do you have the controller set for bulk/float charge?
> 
> Could you explain this a little more..
> "We only had 3 of 4 panels until we liberated the 9 non-functioning cells in panel 4 yesterday."
> ...


First, regarding the 9 bad cells - it was 18 of 36...We had a panel "repaired" as 18 cells and their diode were not working. The panel was only pulling in half of the rated open circuit voltage, until I had a computer repair technician scrape off the epoxy film, test the good and bad diode, and disconnect the bad one.

There are 15 feet of 10 gauge wire from each panel to the combiner box and then 6 gauge wire 3 feet to the controller, then 6 feet of 6 gauge wire (through a 40 Amp fuse) to the Batts. Currently the Fridge is the only thing on the system, while we decide if we want to pay the grand for a Sundanzer. Do you think it would be worth it in terms of further extending the life of these Batts - can one squeeze 10 or 12 years from L16's with such limited use?

As far as I can guess, the fidge cycles on every 30 minutes or so for 10 or 15 minutes. It has not been above 90 outside nor 82 inside during this time, but there is plenty of excess daytime voltage not being used.

The bulk setting is 14.8 volts and Float is 13.5 volts. I went ahead and equalized yesterday ( controller is set for manual) and I noticed the equalization of the xantrex 35 set the volts to 15.8 volts which is .4 volts higher than the Iota battery charger is set for. Is the extra .4 volts OK? One cell leaked a little - but the cells are filled up pretty high from the factory.

Also - the specific gravity readings after equalization were good - but 6 cells were barely 100 per cent 1.264 (instead of 1.265) while 3 were 1.270 to 1.274 would this be OK or should I equalize again until they all consistent? My guess is some will be higher, but it is OK as long as they are all 1.265 or better, and that .001 low on that reading is not a problem. 

Thanks again. How far are you from P-burg WV? We are 1 hour. I sure could have used your help on this project - if you had been able!

Rick


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## Rick (May 10, 2002)

artificer said:


> Take a look at this FAQ. Its a good start to learn about batteries.
> 
> This is what they have on charging:
> ***********************************************
> ...


Hi Michael

According to the Windsun.com site : "Also, there is an upper limit - a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the the positive plates rather in an even film."

The chart indicates that using 20 percent of the voltage is better than 15 percent. This is the understanding I am after, as I might as well use the voltage if it is better for the Batts. 

We have been getting our laptop, fan and light power by charging one of our old deep cycle batts (without a charge controller) with our old Arco panels, and using up to 60 watts while charging to keep the charging voltage at reasonable levels. It works well, and we disconnect the panels when we can't keep an eye on the voltage.

Thanks for all of the thoughts...


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## 12vman (Feb 17, 2004)

Your wire gauges seem to be OK. I forgot to ask the gauge of the jumpers that you have connecting the batteries together.

Personally I believe that you have your settings a little high. On the bulk charge with a setting of 14.8 will make those batteries boil like crazy before it switches to the float level. Many controllers will hold at the bulk setting for an hour or two before switching to float. (Depending on the depth of discharge) If the battery has a deep discharge, it may never get to 14.8 volts and just boil away trying to get to that level. I would back the bulk level down to 14.2 and the float to 13.2 volts. That .6 volts will make a difference on how long the controller hangs on in the bulk mode. If the controller doesn't switch to float by 1-2pm, back it down a little more until it does but stay above 13.8 volts. 

If the float voltage is too high, it just boils the battery for no reason for the rest of the day. Mine don't boil much at 13.2 volts. Sorta like a glass of soda just setting. It can take a week to get things set right. Never assume that you have it until you check your settings several times over a period of time and don't trust the increments on the adjustments. Use your volt meter!

I'll figure the fridge at a 50% duty cycle to be fair..

60 watts, that's a 5 amp draw or 2.5 aHr. Multiply by 24.. *60 aHr./day*

I'll figure the panels at 30 amp of charge.. (Actually 28-29 per specs)

30 multiplied by 4.. *120 aHr/day*. (Prime charge time being between 10 am 'till 2 pm)

Looking at the figures, you are taking your battery well below the 25% discharge level! (More like 50+%) There's your problem..


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## Rick (May 10, 2002)

12 vMan

2/0 parallel and 2 gauge in series. 
The fridge ran in avg 70 deg F outside temp, 43 deg F internal temp., drawing from the Batts from sundown til present It is 11:30 am here. The controller is at rest with a solid green light. Granted t is bright and sunny today, but the batts aren't boiling away and spinning their wheels.

It seems to me the system is working well. I will drop the float and bulk - I was thinking they were high, but this is what BW Solar suggested. Trojan said they like a 15.5 volt equalization charge. Would you keep the bulk at 13.5 or change it any time you equalized? Do you still feel I shouldn't need to equalize much based on our current situation?

Maybe the lower bulk setting would prolong the bulk stage and be better? 

Thanks,

Rick


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## 12vman (Feb 17, 2004)

Most charge controllers don't regulate the equalization voltage. They basically direct connect the panels to the battery and boil the crap out of them for a set period of time. (2 hrs.) While equalizing, you shouldn't have anything connected to your battery. The voltage goes way too high and stuff can fry! In your situation, there's no need to equalize. You cycle your battery daily and the activity from the bulk charge will stir them up enough.

The lower bulk setting will allow the charge controller to switch from bulk to float earlier. This is judged by the amount of resistance the battery is putting on the charge controller (Current resistance) at the set voltage level during bulk charge. (max current.. regulated voltage) Once the controller "sees" that the battery is pretty much "full", (Lower internal resistance of the battery) then it flips to the float level. The voltage drops to the set level of the float charge and the current is then regulated according to the resistance of the battery. (Sometimes as low as 25% of max) Then the voltage is monitored and kept at the set level. If for some reason the voltage should drop below the float voltage setting, the controller will kick back into the bulk mode. 

The "extra" energy is either shunted internally within the controller or to an external shunt. (That's why the heat sink is on the controller) 

Bulk level at 14.2 and float at 13.2 works well for me. I have 512 watts of panel and 4 golf cart batteries configured to 12 volts.


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## mightybooboo (Feb 10, 2004)

Yep,possible to get 10 years from L-16s rarely used,4 of my 8 have reached that point,other four each have a dead cell.

I could have cared for them better,long story re: charging cycle from inverter not working months at a time.

Sounds like a nice setup Rick,congrats.


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## Rick (May 10, 2002)

Thanks BooBoo we are enjoying it.

12vman - Do you mind if I ask what you run on your system, or maybe how many average watts you draw from your batts daily?


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