Batteries and Crankinig Amps

Moot

Veteran Expediter
Owner/Operator
I talked with Turtle our resident battery expert a few hours ago and he is alive and well south of the border. Jamestown, ND to be precise. I'm sure he will weigh in on the subject tonight or tomorrow.

In the mean time I do know that most "deep cycle" batteries are marketed with an AH (amp hour) rating. This rating is somewhat subjective depending on the construction of the battery. Below is a link that may help you. Again, Turtle will probably post in the near future with more battery info than you can comprehend.

Notes on Batteries

also google amp hours battery or deep cycle battery.
 

RLENT

Veteran Expediter
Dan,

Batteries are usually measured and rated by the battery industry in several ways according to what aspect of their performance they are trying to show:

CCA Rating = the measure of a battery's ability to handle a high load for a short period of time. This rating is useful for determining whether a battery is suitable for say, running a starter motor to start a engine on a cold day - high load, short duration. Specifically, the CCA rating is the number of amps a new, fully charged battery can deliver at 0° Farenheit for 30 seconds, while maintaining a voltage of at least 7.2 volts, for a 12 volt battery.

Reserve Capacity Rating = defines a battery's ability to power a vehicle with an inoperative alternator or fan belt. The rating is the number of minutes a battery at 80 degrees F can be discharged at 25 amps and maintain a voltage of 10.5 volts for a 12 volt battery. IOW, how far you can drive before the vehicle will die.

Amp-Hour Rating = This is the measure of a battery's ability to store energy - and the one you really need to be concerned with for a house battery bank. The rating is given in a constant load (a much lower one than either of the above unless it's a way huge battery) that the battery can sustain over a stated time period - generally a 20 hour period (which is why it's called the "20 amp-hour rating") - until the battery, is for all practical purposes, fully discharged and stone dead at 10v.

So a battery with a 100 amp-hour rating could sustain a 5 amp draw for a period of 20 hours. A battery with a 200 amp-hour rating could sustain a 10 amp load for 20 hours.

And any time you draw more amps than the rating, you will get somewhat less total amps out of the battery - as an example, if you put a 10 amp load on the battery with the 100 amp-hour rating it might only last 7.5 hours - not the 10 hours you would expect. Similarly, if you drew less amps out than the rating - say 2.5 amps out of the 100 amp hour battery - you might get 45 hours out of the battery - not just 40. This is because of phenomena known as the Peukert Exponent which is based on Peukert's Equation - basically it means the higher the amp draw, the less power a storage battery will yield.

It is the last rating above - Amp-Hours - not the CCA rating - that you need to be concerned with. In practice, you will find that your Espar is a pretty efficient device (I'm running an AirTronic D2), dunno about the inverter (would depend on the model and what type of loads you are running off it)

I'm running an aux battery bank with 4 Walmart Group 29 Everstart Maxx hybrid deep cycle/starting batteries - I could probably run my Espar only, for 4 days or more, depending on the ambient temps and wind conditions - it is very efficient and has a fairly low power draw (and my Sprinter is fairly well insulated)

If I also have the inverter (2000W AIMS), refrigerator/freezer, charger for the laptop, and the florescent light running - I'd probably lucky to get 30 to 36 hours ..... with the batteries in new condition.

What type of batteries did you end up getting ?

If you want to really preserve the batteries you need to avoid discharging them below 50% and you may want to consider a battery monitor like this:

Xantrex LinkLite Battery Monitor

Turtle and I are both using the predecessor model, the Xantrex XBM Battery Monitor, which is now discontinued.
 
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RLENT

Veteran Expediter
ok you both just gave me a headace the size of texas with all the math and such.
Heheheh .... yeah ?

Just wait until the Turtle chimes in ... you better have the big bottle of Excedrin handy ..... :eek:

Seriously, read it over again - what I wrote isn't all that complicated - it just seems like it is. The only thing ya really need to understand for the question you asked is the amp-hour rating and how it would apply to your batteries and my (highly simplified) explanation of the Peukert effect. :D

BTW, those four Walmart Group 29 batteries I have in my bank are rated at 125 amp-hours each - for a total bank capacity of 500 amp-hours. But - if I don't want to run them below 50% depth of discharge, I can only pull 250 amp-hours out of them .... at most (at a rate of no more than 25 amps per hour)
 
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Turtle

Administrator
Staff member
Retired Expediter
ok i just bought 2 1100 something cca starting batterys for a house bank for my espar and qc and plan to add a 1000 watt cobra inverter...what i need to know is whats the rate of hours you get per cca or at least whats the fourmla for it. please and thank you

Moot and RLENT covered it. And to help you save on the cost of aspirin, I'll use no math here.

But, you said it yourself... you bought two starting batteries (cranking batteries) for a house bank (deep cycle usage).

There is no formula for converting CCA into Reserve Time (rate of hours, or amp hours). CCA is a few seconds of a big fat hairy jolt of electricity used to crank the starter motor to start the engine. Starting batteries are designed to supply a lot of amps all in one whack, but they don't work very well at all at supplying the lower amp draws for extended periods as are necessary for a house bank.

Marine batteries, like the Everstart Maxx at Wal Mart, are marketed as "deep cycle" batteries for marine use, but they aren't deep cycle at all. They're merely cranking batteries with slightly thicker plates that make them deep-er cycle than a standard cranking battery. They are a "hybrid" between starting and deep cycle. They are made for the relatively low amp draw of a trolling motor (which is the same type of draw as an Espar heater, by the way).

I've got four of the Everstart Maxx batteries in my van, and I thoroughly abuse them with a laptop with 3 external hard drives, florescent lights, Espar heater and a Microfridge (fridge, frost-free freezer and a microwave), as well as a printer/scanner/copier.


You will see batteries listed with CCA, MCA and CA.

CCA = number of amps a battery can supply for 30 seconds at zero degrees F. That's so you'll know how many amps you have in the dead of winter, 'cause the colder it is out there the less amps a battery will have.

MCA = number of amps a battery can supply for 30 seconds at 32° F. Who goes out in a bass boat when it's below freezing? That's why they use 32° to rate marine batteries.

CA = number of amps a battery can supply for 30 seconds at 80° F. Mostly used for simple comparisons with car and truck batteries, but it does have critical implications in some heavy machinery applications and in some emergency vehicle applications.

None of these cranking amps numbers have anything to do with how many amp hours a battery has or how many minutes of Reserve Time it might have. A high-end $750 solid lead plate deep cycle battery might have 1100 Cold Cranking Amps and have 220 amp hours of capacity with 390 Reserve Minutes, whereas a $75 starting battery from Auto Zone might have the same 1100 Cold Cranking Amps, but might have 40 amp hours and a Reserve Capacity of 35 minutes before the battery is drained dry.

But the real difference comes with what is known as Reduced Capacity. Every time you discharge and recharge a battery (known as a cycle), some of its original capacity is lost (that's why batteries eventually wear out). The deeper you discharge the battery, the quicker it will wear out due to lost capacity.

Let's say you only discharge them down to 50% and then fully recharge them up to at least 95%, and let's call that one cycle. With true deep cycle batteries, very little of the original capacity is lost with each cycle. With marine hybrids, a few percent is lost with each cycle. With cranking batteries, a significant amount of capacity is lost with each 50% cycle, as cranking batteries are not designed to be drawn down anywhere near 50%, but rather 10-20% and then be recharged in a matter of minutes by the alternator.

In your car, truck or van, if you leave a dome light on overnight and run the battery down, you've probably cut the lifespan of that battery in half, and the total capacity by 25% or more. That means you might still be able to get 1100 CCA out of it for starting, but only for 15 or 20 seconds, not for 30 seconds. Leave the dome light on 4 or 5 times and you'll replace that battery after a year or two instead of after 5 or 6 years.

Your starting batteries may, in fact, be marine hybrids, and if that's the case, chances are they'll be fine for the Espar and limited inverter use. If they are truly starting batteries, with the thin plates needed strictly for starting, be prepared to replace them in about 6-8 months, 12 if you're lucky and always flip the switch on the inverter to actually turn if off when you're not using it. Even if you have nothing plugged into the inverter, if it's turned on, the inverter itself will draw anywhere from half an amp to 1.5 amps all on it's own. A one-amp draw will run a car battery dead overnight, and it's that kind of draw that kills a starting battery and severely shortens its lifespan.

So, the question is, exactly what brand and model number are those batteries, and what are all of the numbers listed on the case?

OK, that's two questions. Math. My bad.
 
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nightcreacher

Veteran Expediter
Myself ,I know absolutly nothing about batteries,and I hope to stay that way.Every 3 years,one of my 4 batteries in the trucks starting system will go bad,so I repalce all 4 batteries,by doing so,the older weeker batteries arent drawing the life out of the newer one that was just replaced.I dont buy the highest cranking amp ones either,the higher the cranking amps,the shorter the life,but i do go with at least 1000 cca.While you are talking starting in cold weather,make sure your grounds are good on your vehicles,you could find yourself not starting some cold mornning,thinking its a bad battery when electric starter is just not getting the amps it needs because of a loose ground cable.
Ok thats my 2 sence,I really have to be bored to get in on this one.
 

Turtle

Administrator
Staff member
Retired Expediter
ok it only say "commerical" on it no cca or anything like that and it's made by crown batterys of fremont,ohio

No model number, nothing other than "Commercial" and "Crown Battery, Fremont, OH"?

You should be able to pick up the phone and call Crown in Fremont and they should be able to tell you everything there is to know about that battery, tho.


the higher the cranking amps,the shorter the life...
Not true. One has nothing to do with the other.
 

danthewolf00

Veteran Expediter
i wound up going to the crown factory today went and bought 2 deep cycle 31dc36 is the model number spec. 20ah/140 5ah/110 rc 200@ 25amps
was told i should get like 16 hours out of each battery or close to it

total price $194 for 2 deep cycle batterys
their whats called seconds batterys that have blemshes on the cases and they can't sell at full price.
 
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Turtle

Administrator
Staff member
Retired Expediter
"spec. 20ah/140 5ah/110 rc 200@ 25amps"

Well, it's 140 AH at the 20 hour rate, 110 AH at the 5 hour rate. And with a sustained 25 amp draw, you'll have 200 minutes of Reserve Capacity before the battery is dead. But when you refer to these you can just call them 140 AH batteries.

Again, you don't want to discharge them down more than 50%, so you've got two batteries for a total of 280 amp hours, but to keep it at 50% just continue to think of them as one battery at 140 amp hours. 16 hours, I dunno, as that depends on how many amps you draw and at what rate. That's where the Peukert Effect comes into play.

A couple of things about those batteries. They are true wet cell deep cycle batteries and are well made. But being wet cells they will spill, so keep them upright. They will outgas if overcharged, so be aware of that. They should charge fine with the vehicle's alternator, as they have the same charging requirements as the vehicle's cranking battery.

That battery is the equivalent of a Trojan SCS225, BTW.

You will draw more amps out of the battery than you think. Everybody always does. You get an inverter and as time goes on you discover new uses for it. You use the inverter longer than you think you will (lights, computer, the QC is an amp hog actually) and are drawing more amps per hour than you think you are. So keep in mind that it takes a lot, lot, lot longer to fully recharge the battery than you think. If you draw down 80 amp hours out of those 280, it might take 6-10 hours of running to get them fully recharged again. The first 80-90% happens very quickly, but it's that last 10% that can take several hours. If you're running a lot it's not a problem, but if you crank it up to idle in order to recharge, plan on idling for several hours. A battery monitor eliminates the guessing, of course.

Crown makes very good batteries. They make them in plants both in the US and in Canada. A year ago, maybe two, they did the unusual and closed down their Mexican plants and moved operations back to the Fremont plant, opening it back up to full or near-full production. I like that.
 

danthewolf00

Veteran Expediter
thing is there was no price on the battery minder at the web site so i plan to do a web search next... thanks for all the help guys



went and found a place selling that xantrex battery moniter for $199
www.blueheronmarine.com

www.westmarine.com found a even cheaper place after buying mine xantrex moniter for $152.99 + s&h
 
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RLENT

Veteran Expediter
Dan,

That's a pretty good price on the monitor - about what I paid for my XBM monitor if I recall correctly.

One might question the wisdom of spending that kind of money to monitor two batteries that cost slightly less than the cost of the monitor. Here's the thing though - it is really easy to kill off batteries with the type of use you'll doing - run them down too low a few times and you'll see significantly reduced battery capacity and life .... don't ask me how I know - well you didn't ask, but I'm gonna tell ya anyways:

After I installed my batteries I took great care not to run them down - once they got down close to 50% I would fire up the truck and start recharging them. There was only one time I ran them below 50% depth of discharge (48.9%) ..... until .....

This past Thanksgiving I managed to get a load that picked up the day before Thanksgiving and delivered the following Monday - but it took me by the house on the way ... so I got to spend a few days at home.

Problem was I got lazy ....... didn't shutoff the inverter and unload the refrig/freezer when I got home on Thursday .... I figured it was fairly chilly at that point and I wouldn't be drawing that much juice ...... I left things set until I went out Sunday to get ready to leave. When I got in the Sprinter the battery monitor was showing less than 11v under load ...... I shutoff the inverter and the voltage bounced back up a bit (over 11v) ..... but the damage was done at that point ..... currently the usable capacity of my battery bank is probably 50% or less of what it had been prior to this incident.

What that means is I now have to deal with the starting the truck up more often to recharge the batteries ....... and not being able to run my appliances as long ...... running the refrig/freezer, Espar, florescent light and charger for the laptop ..... I can maybe go 10 to 12 hours before the alarm on the inverter starts chirpping .... the batteries will likely have to be replaced before summer.

Most likely I'll be able to get them replaced under warranty at Walmart ...... but until I can do that I'll have to live with the some degree of hassle due to the reduced capacity and run time - both of which are only going to get less as time goes on.
 

danthewolf00

Veteran Expediter
at $90 a pop a battery i see moniter as a long term investment. i also plan to get a 200amp battery isolator to protect the starter battery.
2 deep cycle $195
1 battery isolater $102
1 battery moniter $207
total $504

after having my starter battery replaced ($325)i think this will be cheap in the long run!
 

Turtle

Administrator
Staff member
Retired Expediter
Don't forget to add in the cost of some thick, high quality flex cable and cable lugs.

And whatever you do, don't forget to fuse the house bank at the terminal from the isolator, as well as all DC loads and the inverter.



 

layoutshooter

Veteran Expediter
Retired Expediter
I have installed marine battery chagers on my truck. When I get home I just plug them in. I bought two from Dual Pro. One is a 2 bank charger for the deep cycles and the other is a 4 bank for the starters. Each battery charges and reconditons seperately as needed. Each bank has up to a 10amp charging capacity. My APU is set on battery monitor and will come on by itself if the batteries get too low. That really helps when I am not by shore power to plug in the chargers. As stating in here many times, proper charging is very important to battery life. Layoutshooter
 

Jack_Berry

Moderator Emeritus
Dan,

That's a pretty good price on the monitor - about what I paid for my XBM monitor if I recall correctly.

One might question the wisdom of spending that kind of money to monitor two batteries that cost slightly less than the cost of the monitor. Here's the thing though - it is really easy to kill off batteries with the type of use you'll doing - run them down too low a few times and you'll see significantly reduced battery capacity and life .... don't ask me how I know - well you didn't ask, but I'm gonna tell ya anyways:

After I installed my batteries I took great care not to run them down - once they got down close to 50% I would fire up the truck and start recharging them. There was only one time I ran them below 50% depth of discharge (48.9%) ..... until .....

This past Thanksgiving I managed to get a load that picked up the day before Thanksgiving and delivered the following Monday - but it took me by the house on the way ... so I got to spend a few days at home.

Problem was I got lazy ....... didn't shutoff the inverter and unload the refrig/freezer when I got home on Thursday .... I figured it was fairly chilly at that point and I wouldn't be drawing that much juice ...... I left things set until I went out Sunday to get ready to leave. When I got in the Sprinter the battery monitor was showing less than 11v under load ...... I shutoff the inverter and the voltage bounced back up a bit (over 11v) ..... but the damage was done at that point ..... currently the usable capacity of my battery bank is probably 50% or less of what it had been prior to this incident.

What that means is I now have to deal with the starting the truck up more often to recharge the batteries ....... and not being able to run my appliances as long ...... running the refrig/freezer, Espar, florescent light and charger for the laptop ..... I can maybe go 10 to 12 hours before the alarm on the inverter starts chirpping .... the batteries will likely have to be replaced before summer.

Most likely I'll be able to get them replaced under warranty at Walmart ...... but until I can do that I'll have to live with the some degree of hassle due to the reduced capacity and run time - both of which are only going to get less as time goes on.


way to go brainiac:D:eek:. and you give advice about batteries here??? this must be a learn from my dumb stunts category, huh? don't call me and harass me about this post. :D time for solar power dude.
 

RLENT

Veteran Expediter
way to go brainiac .... and you give advice about batteries here???
:p

this must be a learn from my dumb stunts category, huh?
It's that old "do as I say, not as I do" thing Jack :D

don't call me and harass me about this post.
Call ..... ? ....... why call ? .... I know where ya live .....

time for solar power dude.
No room left on the roof .... (.... or in the budget) .... although I have seriously thought about it ....

(BTW, looks like the next project is gonna be a pre-luber :cool:)
 
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