One big or two smaller batteries?

[Ratau]

What difference does it make to use two 65 A/hour or one 130 A/hour batteries?

Is it truth to say that two batteries in parallel could work against each other? :confused:

How does the 12 / 24 volt systems work? Are the starter and alternator 24 volt and the rest 12 volt?

[Iain]

Using 2 batteries will give you longer cranking cycles each time. Technically you can start a GM diesel on a single battery if the weather is warm and the engine is in good shape. But if you have to crank for extended periods, or the ambiant temperature becomes cold, then the 2 batteries will give you that extra stamina to start the engine. I use 2 - 1000 Cold Cranking Amp batteries in my truck and have never had a problem starting it even in extreme cold weather that we sometimes get here in Canada. The colder it gets, the less amperage a battery will generate.

The way GM has the dual batteries rigged up (I believe it is in parallel - 2 positive terminals hooked together and both negative terminals hooked to the engine block) will still only create 12 volts. Just both batteries are working together to create more amps.

Hope this helps you out

[markrinker]

1) Mathmatically, your example is correct. Two small batteries of half the amperage would be of no advantage - in fact they would likely produce less 'usable' cranking amps than the single battery due to losses in the additional cables and connections.

2) Truth! Non-matched or failing batteries can 'work against each other', the bad (or old) drawing the good (or new) down. ALWAYS REPLACE IN NEW MATCHING PAIRS!!! The key is to use the two highest amp, matched batteries you can fit into the available battery locations, cabling them with high quality, heavy gauge battery cables and connectors.

3) 24 volt systems that I have seen on John Deere tractors use two 12 volt batteries and a 12 volt charging system. All accessories are also 12 volt. Only the starter is 24 volt, the batteries are used momentarily in series (12v+12v+24v) during cranking only using a starter relay. I do not know of any 24V systems on GM light duty trucks.

What are your operating conditions in South Africa? i.e. Is the truck used primary on paved roads, or under harsh offroad conditions? What are the average temps during startup? Are you currently having starting problems?

If my impression of your location is right (hot conditions, some poor roads) I would suggest a dual battery setup using gel cells for better vibration and heat resistance. If the conditions are really hot, you might try getting the batteries out from under the hood - behind the cab, for example. Keep the cable runs as short as possible, however... Having lived in both Arizona and Minnesota (hottest and coldest US states) I can tell you HEAT shortens battery life more than COLD, by far. However, COLD makes even new batteries less effective than heat.

Since you don't need lots of cold cranking amps, you might use an isolator to keep one battery 'fresh' at all times, like on marine applications. Great for never getting caught in remote locations with both batteries flat dead...

[ 03-09-2005, 05:41 AM: Message edited by: Mark Rinker ]

[Marty Lau]

If you have two batteries rotate them every year for added life.

[markrinker]

I have heard this, but don't understand what the benefit is...

Seems to me that it has the same net effect of cleaning the battery terminals.

Any thoughts?

[ace58]

I am asking, not debating, but what advantage to rotate the batteries wired in series? The load and charge rates are the same.

[Robyn]

I do believe the term rotate was meant to mean replace. One thing that is very important on the GM trucks is to keep a good eye on the battery cables, The eye end that bolts to the block on the Neg cables will many times corode in the crimp and this creates all sorts of problems.
I recently purchased a 94 Suburban that had this problem and the dealer mechanics Had been overlooking the issue and the previous owner wa at wits end and traded the rig off. I replaced the cables and a couple other small items that had been neglected and now have one sweet running truck for a very low price. I cant say enough about keeping battery cables clean and always use two of the highest cranking amp batterys that you can fit into the truck. Never can you have too much battery.
The only light duty GM rigs that used 24 volts to my knowledge were the Military Blazers,pickups and HMMWV

[markrinker]

Agreed! The negative terminals and frame/block connections seem to be the culprit 90% of the time.

The batteries are wired in parallel, not series. Parallel yields 12V and you add the amperages of each battery together, ~less some additional cable losses. Series would yield 24V and you'd get the average amperage of the two batteries.

[Ratau]

What you guy

[moondoggie]

Good Day!

16ga SxS said, [i]

[Cowracer]

First off, you cannot "over-battery" a truck. Having too much capacity and never needing it will win hands down over coming up short even once.

For ruggedness and longevity, generally the larger batteries have a slight edge, all other things being equal. Don't try to skimp on batteries. Get name brand.

I work in the lead industry, and trust me, the specifications and construction methods for manufactures vary widely. There are some true POS out there.

tim

[markrinker]

Whomever makes lead/acid batteries for Chrysler rocks.

My wife's 1999 Chrysler Concorde has 145,000 miles on it, and retains the ORIGINAL factory battery. That is 78 months and has endured seven Minnesota winters with subzero, no-block-heat starts. Sits in the driveway outdoors most of the time.

I am so amazed at this point, that I am betting it lasts another year (or two)!!!

[Cowracer]

Originally posted by Mark Rinker:
That is 78 months and has endured seven Minnesota winters with subzero, no-block-heat starts. Sits in the driveway outdoors most of the time.Mark, winter does not kill batteries, SUMMER kills batteries. Winter just buries them. That same batt would have given up by now if you lived in Arizona

Tim

[markrinker]

Agreed. I suspect the reason it has lasted so long is due to easy starting of a 3.2 FI engine, combined with all smooth highway driving (little jarring and vibration).

Interestingly, it is mounted way down low next to the passenger's side front tire. Possibly the location has something to do with it as well? I have never even seen the battery.

In the same time period, I have replaced every PAIR of diesel batteries TWICE. But, I don't plow much snow with the old Concorde...lol.

[Iain]

Winter can kill a battery just as easy as heat. If your batteries are not fully charged some of the acid of course turns back to water. Water tends to freeze and expand. Plastic battery cases do not like to expand and will tend to crack. Even if the case does not crack, a frozen battery when thawed may or may not take a charge again. If it does take a charge, reliability is greatly reduced. It may be cold in the Northern US, but trust me, -30 or colder degrees C in Canada is way colder and can wreck havoc on improperly maintained batteries.

[markrinker]

Yup. When they freeze, the plates get shoved around and make contact, shorting out that cell.

When I was young, dumb(er) and really poor, I dumped all the acid out of a failing battery and added new, purchased on the sly from a friend at the parts store. It actually gave me a month or two until I had to scrape up the $60 for a new battery. Don't ask where the acid went, but the EPA wouldn't approve. Like I said, young, poor and dumb!

[Hye]

Simple but very complete and up-to-date discussion about batteries at

http://www.uuhome.de/william.darden/carfaq1.htm.

There is an explanation for all the observations posted here.