question on deep cell batteries

burnerboy33 · Post by **burnerboy33** » Thu Mar 29, 2007 7:19 pm

Is a 50 amp-hour battery a battery that will run a 1 amp device for 50 hours?

I have these gell cells that are 180 min. runtime with a 25 amp draw. so would that make these 75 amp-hour batteries?

180 min.= 3hours
is 3 hours @ 25 amp draw the same as 75 hours @ a 1 amp draw?

LeChatNoir · Post by **LeChatNoir** » Thu Mar 29, 2007 8:43 pm

One amp/hour is the ability to give one amp of current for one hour. So, yes... I believe your deep cycle battery will give you 25 amps for three hours.

Make sure it is a deep cycle battery. Anything else will be toast after a couple of complete discharges. It kills the plates. Probably not a good idea for deep cycles in the long run either.

Stargeezer could tell you better whenit comes to these things. He knows more about it than I do.

LeChatNoir · Post by **LeChatNoir** » Thu Mar 29, 2007 8:43 pm

And I believe that your voltage will be dropping over this perod also, so that might be an issue.

robotland · Post by **robotland** » Thu Mar 29, 2007 9:17 pm

Yep...It ain't the AMPS- It's the HOURS that getcha.

Post by **mdmf007** » Thu Mar 29, 2007 11:37 pm

Ive seen plenty of batteries drop from a full charge of 14 volts and enough amps to weld with - and later not have enough amps to light a flashlight and still have 10-11 volts. Funny how batteries work.

later all

gyre · Post by **gyre** » Fri Mar 30, 2007 12:54 am

Batteries actually have a power curve.
Only things like lithium are flat.
A typical rating would be short high draw (within specs) and long term which is usually many more amp hours.
What kind of batteries are you talking about?
I have used non-deep-cycle batteries for recharging.
A lot of deep cycle batteries suck.

And yes, your interpretation of amp hours is correct.
Batteries are rarely linear though.

gyre · Post by **gyre** » Fri Mar 30, 2007 12:59 am

Gel cells typically hate high draw applications.
Their strength is stability and that doesn't translate to high draw.
If they are that big, we should be able to find the curve on them.
Some nicads are specifically made for high load or low load/long hours.
Are these lead calcium gels?

MikeVDS · Post by **MikeVDS** » Fri Mar 30, 2007 2:26 am

One amp/hour

It should be AMP-HOUR (as originally stated) not AMP/HOUR.
I'm not trying to nit-pick, just make the correction in case it's confusing someone who's fairly new to these unit conversions.

When you have the format unit(x)-unit(y), it means they multiplied them together to get that x-y unit.

When you have the format unit(x)/unit(y), it means they divided x by y to get that x/y unit.

And I believe that your voltage will be dropping over this perod also, so that might be an issue.

Good batteries voltage drops off quickly. Voltage stays high (within 10% of nominal value) until it's nearly drained of charge. Cheap batteries drop constantly as the charge decreases. You can find these voltage curves for most decent batteries.

skibear · Post by **skibear** » Fri Mar 30, 2007 12:07 pm

burnerboy33 wrote:Is a 50 amp-hour battery a battery that will run a 1 amp device for 50 hours?

I have these gell cells that are 180 min. runtime with a 25 amp draw. so would that make these 75 amp-hour batteries?

180 min.= 3hours
is 3 hours @ 25 amp draw the same as 75 hours @ a 1 amp draw?

No. The Amp-Hr ratings for batteries are rated at a certain rate-usually
over a 10 hour period to a certain voltage drop from the full charge voltage.

so the bottom line is:
A 1 amp load will run for MORE than 50 hours.
A 5 amp load will run for 10 hours.
A 25 amp load will run for MUCH LESS than 2 hours since higher
discharge rates are less efficient (more heat loss etc).

Do I know anything?-I blew up a AA NiMh cell in our kitchen recently!
What a mess- I even called Lenveno to see if the vapor was toxic
(no).

hth

gyre · Post by **gyre** » Fri Mar 30, 2007 12:47 pm

One of the power graphs on some batteries is a amp-hour by power curve showing the changes in rating according to draw.
Other curves might show voltage over time at a certain load of draw.
Some batteries are tested with intermittent loads or steady showing recovery ability.

Gel cells typically need a slow charge to avoid damage.
The optima deep cycle is an encapsulated wet cell with continuous plates and has a low internal resistance so can be charged rapidly.
The deep cycle is the same as the cranking battery except for heavier plates.
Most deep cycle batteries are very simple and don't do well with high draw.

(Cranking rating is usually for a very short term. It should be expressed as a time based measurement though.)

phil · Post by **phil** » Fri Mar 30, 2007 1:29 pm

skibear wrote:>SNIP<
so the bottom line is:
A 1 amp load will run for MORE than 50 hours.
A 5 amp load will run for 10 hours.
A 25 amp load will run for MUCH LESS than 2 hours since higher
discharge rates are less efficient (more heat loss etc).
>SNIP<

I suggest reading any manuals that come with rechargeable batteries. Mine say not to discharge below 50%, so I'm less concerned with how long I can actually run a device on batteries than how long the batteries hold over 50% of their charge.

Over discharging batteries leads to some damage that over time wrecks the batteries.

MikeVDS · Post by **MikeVDS** » Fri Mar 30, 2007 2:13 pm

No. The Amp-Hr ratings for batteries are rated at a certain rate-usually
over a 10 hour period to a certain voltage drop from the full charge voltage.

It really depends on the company you're dealing with and the format they give it in. AMP-HR is a unit. It's poor engineering practice to try to define it the way you're describing it. Really the batteries have an AMP-HR rating and have some efficiency vs. AMP curve that will modify the useful AMP-HOURS you get. The chart you describe is just a list of durations using data from a few points off that curve as a simplified version for non engineering types.

EspressoDude · Post by **EspressoDude** » Fri Mar 30, 2007 2:35 pm

A lot of the non linearity of battery amp hour draws is due to internal resistance in the battery. This is a small amount, like 0.005 ohms or less. Current thru this resistance in the battery causes a voltage drop at the terminals and is wasted energy. Most battery manufacturers have discharge curves available for their batteries, that show the loss of amp hour rating at higher current draws.

I have some Hawker (think orange case) gell cell batteries that were used as capacitors in X-ray machines. I used them to power my battle bot, and am now using them to power utility electrics, fans, and lights in our tent at BM. They work great, have incredibly low internal resistance, and have been deep discharged many times. At BM two are connected in parallel and are maintained with a 50watt solar panel.

If you can't get curves, life expectancy data, from the mfg., look elsewhere.

If what you want is to deep cycle without high current loads like startermotors (200 - 1000 amps) you might consider marine deep cycle batteries for sailboats......many many cycles.

Look at the website for West Marine for info......their prices are high......but the info is good.

skibear · Post by **skibear** » Fri Mar 30, 2007 7:09 pm

phil wrote: I suggest reading any manuals that come with rechargeable batteries. Mine say not to discharge below 50%, so I'm less concerned with how long I can actually run a device on batteries than how long the batteries hold over 50% of their charge.

Over discharging batteries leads to some damage that over time wrecks the batteries.

Absolutely true. One reason the NiMh battery packs in Hybrid cars (Prius
etc) seem to last indefinately is that in normal use they are not allowed
to discharge more than about 20 %.

skibear · Post by **skibear** » Fri Mar 30, 2007 7:17 pm

MikeVDS wrote: The chart you describe is just a list of durations using data from a few points off that curve as a simplified version for non engineering types.

True. Just trying to keep it simple- KISS- for non-engineering types!

Curves,mon. Check out the curves.

burnerboy33 · Post by **burnerboy33** » Sat Mar 31, 2007 7:25 am

I found a web site for the batteries and they are 94 amp-hour

Mushroom · Post by **Mushroom** » Sun Apr 01, 2007 12:14 am

I thought amps were measured in seconds? this is all so confusing.

gyre · Post by **gyre** » Sun Apr 01, 2007 12:21 am

Amperage is a measurement of amount of current.
Amp-hours are a time based measurement.

There are graphs of amp-hours over the life of a battery as well, if I didn't say.

Wattage is volts time amps=total power.

100 watts at 12 volts=a lot of amps.
100 watts at 120 vac= low amperage=smaller wire=same power total.

Post by **mdmf007** » Sun Apr 01, 2007 8:49 am

Mushroom - only electrical measurement I can think of measured in seconds is Hertz. Hertz is the cycles per second in reference to Alternating Current.

MikeVDS · Post by **MikeVDS** » Sun Apr 01, 2007 12:43 pm

Just trying to keep it simple- KISS-

So are you calling me stupid or trying to get fresh with me? Hmmm?!

Sync · Post by **Sync** » Mon Apr 02, 2007 8:44 pm

Ok, so lets get really low-brow about this. I got one of burnerboys 70lb deep cycle batteries and want to make it run a 100 watt electric palm tree.

Assuming the battery is in good shape and I'm using a 300 watt car cnverter, how many hours do you think it can keep it going?

gyre · Post by **gyre** » Mon Apr 02, 2007 9:06 pm

I would think 8-10 hours.
You would look for the amp-hour capacity at a 10 amp draw, take into consideration age of the battery.
What is the loss through the inverter at a 10 amp rate?
They are not always linear.
Add that loss to the consumption.
Then what is the voltage sensitivity of the inverter and the load you are powering?
Some things shut down at a high voltage, like ge fluorescent flashlights.
Other things operate until they are very very dim.
Cheap inverters tend to be very power hungry.
Medium price units are very power hungry at low draws and good at high draws.
It is always better to run on 12 volts when possible.
If it is a dc load or can be, you might use a set of batteries to reach 120 volts in dc.

You can also hook the sucker up and run a test.
See what voltage becomes too weak to be usable.
If it is LEDs, remember that they are never 120 volts, they max at 7-8 volts.
Other approaches work best there.
How about a converter from 12 volts to 7 volts?
That is how some truck lights work and they will run down to 6 volts or lower.

phil · Post by **phil** » Mon Apr 02, 2007 10:12 pm

Sync wrote:Ok, so lets get really low-brow about this. I got one of burnerboys 70lb deep cycle batteries and want to make it run a 100 watt electric palm tree.

Assuming the battery is in good shape and I'm using a 300 watt car cnverter, how many hours do you think it can keep it going?

You need to know how many amp-hours the battery is rated for. I may have missed that in an earlier post. Your lights are AC, which is measured in watts, and the battery puts out DC, which is measured in amps, so we convert.

Amps = Watts/Volts

Your battery is 12VDC, the lights are 100 watts, so the amps to drive the lights is 8.33... . If you battery is rated at, say, 60 amp-hours, then you have 60/8.33 = 7.2 hours of power - that's the theoretical number of hours. You have to consider some loss from your inverter - the device you plug the lights into and then connect to the battery so that the DC battery delivers AC to the lights. Some estimate the loss at 5%, so factor that in; in this case it adds about 5 watts to your lights.

You also need to read the manual and see what the maximum drain is. There's a maximum discharge current - exceeding it heats the battery up and boils off the water (if it's a wet cell); and there's a maximum depth of discharge - some recommend no more than 30% of capacity, some 80%, so you have to read your battery's manual. If the maximum depth of discharge is 50%, then you've cut your 7 hours in half.

See Brad Templeton's page at
http://www.templetons.com/brad/burn/burn-power.html
for lots of information on how to determine your oomph. Er, amps.

As gyre says, you're better off running 12VDC devices off your batteries, but it's sometimes difficult to justify the added expense of having 110VAC stuff for regular use and 12VDC stuff for Burning Man. The issue then is the quality of your inverter and how often you want to replace it, the battery, and the lamps and other stuff you run off the inverter.

Inverters draw power even when the lights are turned off, by the way, just like wallwarts at home. So fully disconnect everything from the battery when you're not powering anything.

phil · Post by **phil** » Thu Apr 05, 2007 2:11 pm

Our radio club had a presentation from a salesman from PowerSonic last night, and here are my notes from his talk about lead acid batteries:
http://www.cieux.com/bm/batteryWreck.html

I recommend downloading their .pdf Technical Manual at
http://www.power-sonic.com/index.php?doc_id=116
which will trigger the download of a 16KB file.

Page 6 of that file has a chart that lets you determine what amp-hour capacity you need for known discharge currents and known times to run the device. (Example, you want to run a device that draws 2 amps for 3 hours, they recommend 7 amp-hour battery - or you can do the math. :->)

The problem remains estimating how many amps your gear is going to draw. We already know it can't be done (:->) for a week, but still it's nice to know how short we'll fall so we still have some batterylife left on the night of the burn.

phil · Post by **phil** » Wed Apr 11, 2007 2:37 pm

> Our radio club had a presentation from a salesman from
> PowerSonic last night, and here are my notes from his talk
> about lead acid batteries:

One of the guys at the meeting who knows more than I do reviewed my notes and suggested corrections:
http://www.cieux.com/bm/batteryWreck.html
which I think make it more nearly correct and I know make it more readable.

gyre · Post by **gyre** » Wed Apr 11, 2007 2:57 pm

If the agm is the same as an encapsulated wet cell, I would have thought the uses were reversed.
Gels tend to output high power less easily.
Wet cell recharge more rapidly.
An optima has a very low internal resistance and recharges very rapidly.
Gel cells main advantage is storage stability and portability, as it tends to resist leaking in all positions.

They make vent caps for non-sealed batteries.
Sort of an option.

phil · Post by **phil** » Wed Apr 11, 2007 4:53 pm

gyre wrote:If the agm is the same as an encapsulated wet cell, I would have thought the uses were reversed.

I have no idea. google relates encapsulated wet cell only to Optima, so I assume its a service mark they own.

I won't pretend to be an expert - I'm repeating what the guy said. On this page:
http://www.batterystuff.com/tutorial_battery.html#3
the guys says, "Gel Batteries are best used in VERY DEEP cycle application ... ." (He left off the s, not me. :->)

He says this about AGM: "The AGM batteries we sell are typically good deep cycle batteries and they deliver best life performance if recharged before the battery drops below the 50 percent discharge rate. If these AGM batteries are discharged to a rate of 100 percent the cycle life will be 300 plus cycles and this is true of most AGM batteries rated as deep cycle batteries."

Frankly, it makes no difference to me. I'll abuse the battery mercilessly, not charging it regularly, deep discharging it, taking it to the playa, and so on. I have a wet cell marine battery and an AGM battery, and I don't take professional care of them, so both will have their little lives shortened drastically.

gyre · Post by **gyre** » Wed Apr 11, 2007 6:01 pm

Optima uses a matrix that holds the fluid in place and supposedly can hold enough fluid to keep the battery working with a hole in it.
Exide makes a knockoff of it for more money.
They claim it is better.
The extremely low charging resistance on the optima is more due to the continuous wound plates that have an extremely robust connection at the ends.
It looks like a perforated lead sheet.
It acts like a wet cell otherwise.
It has an unusual side benefit.
The matrix between the plates, which also acts to hold the plates in place, holds material that comes off the plates in place.
A common mode of failure is pieces falling between the plates and shorting them out.
The gel typically has a higher resistance (because it's a gel) ad is damaged by high rates of discharge.
They are commonly used for alarms due to their stability.
There are different forms, of course.
There are some pretty exotic batteries in use on cars and bikes now to reduce weight.
There are some cheap deals on rechargables.
I imagine most of these are legit but rejects from matched sets.
I find very good deals on the marine optimas in deep cycle.
I have had great luck floating a semi battery which is not a deep cycle.
They are built tough and in quantity.
So cheap for what they are. 1200 amps cranking.
The optima does seem to be able to charge very fast .
This might be an advantage with a generator.

spirited · Post by **spirited** » Thu Apr 12, 2007 2:29 am

[quote="burnerboy33"]Is a 50 amp-hour battery a battery that will run a 1 amp device for 50 hours?

I have these gell cells that are 180 min. runtime with a 25 amp draw. so would that make these 75 amp-hour batteries?

180 min.= 3hours
is 3 hours @ 25 amp draw the same as 75 hours @ a 1 amp draw?[/quote]

A gel cell is recombinant the oxygen produced on the+plate recombines with the hydrogen from - plate = (H2O) witch replaces lost water.
On Deep cycle GEL batteries depth of discharge can affect cycle life.
100%=500 life cycles (75%discharged=750 life cycles ) 50% discharged=1100 life cycles .
Charging time ratio. run time vs charge time. 60-55%=2hr charging=1hr run time, 45-30%=3hr charging=1hr run time.
New GEL batteries brake in procedure . Full recharging (regardless of use) for the first 20 days and/or 30 charging cycles " Power at 2 charging cycles= 60% at 10 cycles =90% 20 cycles =100% thy peak near (120%) then down hill. KEEP/STORE GELs FULLY CHARGED . Discharge/short charging sets up crystalline/sulfate structures and will not turn to acid when recharging.
CHARGING LEVEL GEL/SEALED
100%=static 12.8 VDC on charger 14.4 VDC (MAX)
75%=static 12.5 VDC on charger 14.1 VDC
50%=static 12.3 VDC on charger 13.9 VDC
25%=static 12.2 VDC on charger 13.7 VDC
00%=static 12.1 VDC on charger 13.5 VDC
--%=statis 11.9 VDC=(crystalline/sulfate structures)
Severe discharge can take 10-16hr to charge at 3-5 AMP and (recharged at 12.5 VDC 75%=static ). NEVER BOOST CHARGE sets up crystalline/sulfate structures #1 KILLER of GELs.
For best life charge 33SLDG at 10-12 AMPS 27SLDG at 8-10 AMPS 24SLDG at 6-8 AMPS 22SLDG at 5-6 AMPS U1SLDG at3-4 AMPS.
Lester makes dual mode chargers GEL or wet lead acid .
You can set the cut off VOLTS on some chargers.
Remember volts not time time=(crystalline/sulfate structures).

Here at Hot Wheelz Camp, we offer the gift of mobility to fellow Burners who might have difficulty traveling to the far reaches of Black Rock City. It is our goal to expand and enhance the opportunities for our Themecamp guests to PARTICIPATE!
PS good luck.

munney · Post by **munney** » Mon Aug 20, 2007 5:07 pm

I liked what Gyre says, and he's smart. He told me to build my shade structure out of Unobtanium, and he's right, Now I have no shade, It's perfect.

For battery usage, I fugure, Amps, hours, hertz, Ohms, Megadildos, schmegmadoodles, Parsmips, and electromold, all comes from Gyre. He knows best..... Or one could just get on and ride till they run out, then switch to the next set.

question on deep cell batteries

question on deep cell batteries

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