deep cyle battery: best bang for the buck?

[mans]

went shopping today to see what I could find for a deep cycle battery.

the local advance auto parts had about 6 of them ranging from 28 AH up to 55AH, and the prices begun at $180 for the 28AH and went up to almost $300 for the 55AH.

I'm just wondering if there is a better path to take...

$300 is a little high for me, but $150-$180 could be ok, however I'm wondering if I could do better then these batteries I see in "advance auto parts", as the prices seem high to me.

$125-$150 would certainly be easier on the wallet, I'm wondering how I could make this purchase go the farthest in helping with the Alt delete that I'd like to perform

[Daox]

I'm not even sure advance carries true deep cycle batteries, but those prices are ridiculously high. I can buy a group 24 (~75Ah) for about $80, and a group 31 (~100Ah) for just over $100. These are flooded lead acid cells. This is at the local batteries plus store.

[mans]

Originally Posted by Daox

I'm not even sure advance carries true deep cycle batteries, but those prices are ridiculously high. I can buy a group 24 (~75Ah) for about $80, and a group 31 (~100Ah) for just over $100. These are flooded lead acid cells. This is at the local batteries plus store.

thanks a lot Daox,

I just researched "batteries plus" and they have got quite a selection.

the ones in the auto parts store said "deep cycle" , however they say they were meant for the guys who are running huge stereo systems and need some extra juice.

I hope the employees in the "batteries plus" stores are knowledgeable on the products as I hope to visit one and get a better idea on whats available out there.
If anyone can shed any light on what type of deep cycle battery is best suited for an alt delete I'd be very much appreciative....
thanks a lot everyone

[brucepick]

I've been working on this question for my own car and will share a few things.

You didn't say what you're trying to accomplish by using a deep cycle battery.
In my case I wanted to
1) enable longer coasts with engine off and headlights or heater fan on
and EVENTUALLY
2) enable the car to run off a deep cycle battery with the alternator disconnected, for a couple hours or more.

#1 was not so difficult. I ran a pair of cables out the back of the hood and in through the front passenger door, to a 2nd battery on the rear floor. That's a temporary location for "concept testing and proving". It worked. Even a coast of a mile or more only brings system voltage down to about 11.6, which is OK by me.

So, nearly any 12V battery that's compatible with the main one, wired in parallel, will solve that problem. And the pair cranks the starter super strong, regardless of frozen outside temperature here in New England.

#2 is more challenging. I'm concerned about venting of hydrogen gas. Supposedly it only comes from overcharging, HOWEVER I've also heard that cars with battery in trunk typically get a rusted out trunk from frequent or continual venting of sulphuric acid or some component of that noxious stuff.

So I decided to use only EITHER: an AGM (absorbed glass mat) type lead acid battery, OR a lithium LiFePO4 pack. Either type raises the cost out of the $150 category very quickly.

AGM is a type of flooded lead acid battery, aka FLA. Same chemistry as a regular flooded battery but the acid is in a paste and is absorbed into a fiberglass mat. It's practically leak proof and can be installed laying on its side. Disadvantage: for battery life of more than 300-400 cycles, you can only discharge it about 20-25% of capacity. So your 60AH battery becomes a 15-20AH battery if you want to keep it working. You can charge it with your stock alternator, or hook up an A/C charger instead.

LiFePO4 is supposedly super safe and avoids all the fire/explosion concerns of other lithium types. You can discharge it down to 20% of capacity, using 80%, and still get ~2000 charge/discharge cycles. More cycles if you discharge it less. So a 40AH battery would have 40*.8 = 32AH available capacity, not too shabby. That's double the available capacity of a 60AH lead acid unit, and about 1/4 the weight of the lead battery too.

You can't charge it off the alt as the Li based pack is 12.8V and needs higher charging voltage than a 12V battery. I haven't tested that info - maybe if you hook it up to your stock setup it would charge some. But its charging specs are definitely not the same as a lead acid battery. I plan to charge mine nightly from A/C.

Here's a link to one. Note the link on that page to the charger they offer. Custom LiFePO4 Prismatic Battery: 12.8V 40Ah (512Wh, 30A rate ) with PCM, charge & discharge terminals (48.0) I'm getting an upgraded version that has a 100A limit.

[Rick323]

Originally Posted by brucepick

#2 is more challenging. I'm concerned about venting of hydrogen gas. Supposedly it only comes from overcharging, HOWEVER I've also heard that cars with battery in trunk typically get a rusted out trunk from frequent or continual venting of sulphuric acid or some component of that noxious stuff.

My parents 2004 Pontiac Bonneville battery is located under the passenger's side rear seat from the factory. Last I looked (a couple months ago) there was no rust/corrosion anywhere. I never looked for a vent but it's not in an air tight compartment, lift the seat up and there it is.

[Daox]

As far as different types of lead acid deep cycles there are kind of two. They make true deep cycle batteries and starting deep cycle batteries which is kind of a hybrid between a starting battery and deep cycle. You would want a true deep cycle as it'll last longer when deep cycled.

You can use an alternator to charge the lifepo4 pack, it just won't be charged fully. This isn't a big deal like it is with lead because lithium batteries are actually quite happy only partially charged where lead acid batteries will sulfate and that will kill them eventually. If you simply wanted a pack that lasted longer for engine off coasting but still charged via the alternator you should be fine going to lifepo4.

However, IMO a lead acid deep cycle, even flooded cell which is the most typical and cheapest, is just fine. It'll still last at least a couple years. I think I'm on year 2 or 3 with mine. Its a group 24 flooded lead acid. When I got it I had a 42 mile total daily commute and it held up just fine (less than 50% discharge each day). The past year it is back to normal duty of being charged via the alternator due to my wife driving the car. It definitely won't have the life of a lifepo4 cell, but the cost is significantly less too. In the long run a lifepo4 might be cheaper, but the payback will be quite long.

[3dplane]

Originally Posted by Rick323

My parents 2004 Pontiac Bonneville battery is located under the passenger's side rear seat from the factory. Last I looked (a couple months ago) there was no rust/corrosion anywhere. I never looked for a vent but it's not in an air tight compartment, lift the seat up and there it is.

There is a vent system on those with two hoses hooking up to the rectangle shaped vent holes at either end on the top of the battery,then the two hoses merge into one and they exit the vehicle through a grommet on the floor near the battery....supposed to anyway. Some Buicks have the same setup.


@mans: It really does not have to be expensive. All depends on your personal electrical usage.
Get a voltmeter,hook it up to your car and monitor it/learn what the voltage looks like on your "normal" drive.
On my car I learned the interesting fact that it did not charge at all until the coolant temp was up! Day or night (electrical load)did not matter.

At one point I had three voltmeters hooked up because I did not believe what I'm seeing.

Later with the alt. disconnected I added a 14A/h sealed lead acid and the system voltage sagged into the 11.x volts toward the end of my commute and I did not like that. So I added a regular 55-ish A/h car battery in the trunk. That made it a lot better but since I carry a homemade jump box ( I'm a mechanic) in my trunk that is made out of a 63A/h truck battery I keep it clipped onto the other battery mounted in the trunk. Now I can finish my 58 mile drive at night with the headlights on and the voltage does not sag below 12V which means I am not torturing any of the batteries. (total of 194A/h with the car's original batt.)

The key is to monitor the voltage so you know your needs and not to let them over discharge causing permanent damage to the batteries!

You could go to Interstate and by a blim battery for $30-40 (have not checked their prices lately) They are either refurbished or just had some cosmetic damage so they can't sell it as a new battery at full price.
If your needs require more you can always add more later.

Many ways to do it! This is how it works for me!

Barna

[jrscteg]

^So your carrying 3 batteries total? That's 60-70 lbs more you have to haul around everyday. Does it pay off? You could maybe look into an 8d battery, they are a little heavy but you could probably go 100 miles at night with the lights on.

Trojan Battery Company

[mans]

I called the local dealer for trojan golf cart batteries

Trojan 30 xhs12v deep cycle rated at 105 ah /5 hr discharge rate is $239
Ultrapower ev31 105 ah /5hr discharge rate $170

these golf cart batteries are lead acid (no gel, no "glass mat"(whatever) and are quite pricy.

I called the local "batteries plus" and sure enough a group 31 battery was

---> $99 <---- with a 100 Ah rating.

batteries plus just did not tell me over how many hours the 100ah rating has been taken over

is there any advantage of having the trojan or ultrapower battery over the $99 "batteries plus" model?
I don't see any as they are both standard lead acid.

please correct me if I'm wrong here

[cfg83]

mans -

In the very very old daze (1930's) my grandpa sold batteries door-to-door. The "longer lived" batteries were the exact same battery with longer warranties and accompanying higher price. Therefore the difference was a "peace of mind for the consumer" thing.

I am not saying that's true today, but just FYI.

CarloSW2