720 John Deere

[Anonymous-0]

John Deere 720 Gas is hard starting. Stalls some what on compression stoke. What is the best combination of batteries or battery to use to get it to turn over better?

 

[cole in mo.]

Are you sure its not timed too fast?

 

[teddy52food]

Bad & undersized cables? Dirty connections? What is the battery voltage when cranking? Is it near the same at the starter? Do the batteries check out good with a load test?

 

[Tim14167]

Being that it is a 12 volt system, you should use two six volt batteries tied in series to create the 12 volts that required. When buying batteries get the biggist batteries that will fit in the battery box, and don't be afraid to spend a few extra dollars on better the batteries.

Example: If you tie two 6 volt batteries in series, each having 650cca, you will not get 1300caa. What you will get is more battery storage. This will give you more power to crank the engine longer than one 12 volt battery with equal or about he same cca can. You should always change the batteries in sets, do not change one battery at a time becuase the new battery will be pulled down and do most of the work. I know it is expensive, but you wont regret it. Buy the biggist and best batterys that will fit in the battery box!

 

[jddriver]

wrong answer amps are only as much as the weakest battery.Get two 12 volt batteries and wire them pos to pos and neg to neg and the volts stay the same and the amps add up.You wont be happy with two six's

 

[Mike M]

What shape is the starter in ? Many get negelected and need bushings and brushes. A dragging starter can cause this.

 

[BushogPapa]

Sounded like it was kicking back from a stuck advance mechanism or improper timing..

Ron.

 

[Tim14167]

Batteries are storage devices. Amps do not add up. Volts only add up if they are hooked up in series. The bigger the batteries are or the more batteries you have will give you more storage of electricty. This will aide in cranking the engine and it will also maintaine the cranking speed for a longer period of time. You can either hook two 6 volt batteries up in series or two 12 volt batteries up in parralle to achive the propper voltage and amount of electrical storage that is needed.
If you think about the 80, 820, and 830 series. These tractors were built with four six volt batteries NOT two 12 volt batteries. Wheter you deciede to use four 6 volt batteries or two 12 volt batteries, they were hooked up in series to create the 24 volts that is required. The problem with using two 12 volt batteries is that they did not have enough storage of electricty to maintain the crank. Batteries are storage devices.

Question: If you have two air compressors hooked up in parralle or even in series as you stated with the batteries. Each air compressor set at 90 psi. Do you have 180 psi at the blow gun or do you still only have 90 psi? Think about that...
Batteries are like air compressors, they are stoarage device. The bigger the tank is on the compressors or the bigger the batteries are will give you more volume of air or electriclty over an extended period of time. Whether its 90psi or 1200 cca it is a storage device. Physically the bigger the battery means more cca. The battery is only capable of putting out what it is rated for. In other terms, if a battery is rated for 1200cca it is imposible for it to put out any more than the 1200cca. This holds true even if there is another battery tied in series or parrelle. It can not create cold crank amps (cca)in which it does not have.
As stated in other replies, having a good starter with bearings and brushes that are not worn will help in starting. The battery cables are another thing to look for. Do not use any thing less than a 2/0 copper cable for both the positve and negative leds. A welding cable is perfered over other copper cable. The smaller the wire strands are in the cable will equals less resistance in the transfer of electrical current from the batteries to the starter.

 

[J.ReinkeFarms]

Wow Tim, hate to tell ya this after your long rant, but you’re wrong.

The amp rating on a battery is not a measure of its reserve, it's a measure of how much current you can push through that battery to make a circuit. If the cables can handle it when you put batteries in parallel you effectively double the amperage capacity of the circuit while keeping the voltage the same. If you have batteries in series like to 6v you can only push through the amount of amps the lesser battery is rated for.

Batteries act like resistors, look it up, understand it, learn from it.

 

[GlenT]

Another thing to consider is that the higher amperage batteries have more fragile seperators and plates than the "farm rated" or lower amperage batteries. I have found out the hard way buying the expensive high cca batteries only to find out that they don't last. Tractors are hard on the batteries since there is no suspension and the engine is hard mounted to the frame which causes lots of vibration to the battery(ies).

 

[CLW]