Battery Replacement - - Best Practices?

[RCW]

Just to be clear, this is probably a foolish question and not a tutorial.

Probably derived from recent cold snap.

Recent years several folks have fried one or more electronic control modules (ECM) in their tractors just by replacing batteries. Some tractors have 3 or 4 ECM?

Heard similar horror stories for passenger vehicles/small trucks.

Some have had to pay many $1,000's to fix.

My BX has no electronics to fry.

I recall a post a couple years ago where I was gun shy about replacing a battery on one of my vehicles because of the same risk.

Without concern, I've replaced many vehicle batteries over time with ECM without issue. Maybe I was lucky.....

Is there a Best Practice to replace a battery?

1. When removing, I disconnect negative/ground first, then positive.
2. Reverse order when replacing/reconnecting. Positive post first, then ground.
3. Does that method work for modern ECM tractors?
4. Does it depend on make/model?
5. Does that replacement order typically apply to cars/trucks?
6. I recall someone saying they actually hook up a temporary 12v source (e.g., temporary battery or jump pack) to ensure the system remains energized during the process.
7. Is #6 a common requirement to avoid ECM damage?

 

[je1279]

Your first two steps are what I have always used and I have never had an issue replacing batteries. #6 is only necessary to maintain settings like radio presets which are lost if power is removed for a period of time.

 

[RCW]

Your first two is what I have always used. #6 is only needed to maintain settings like radio presets that are lost if power is removed for a period of time.

Thanks much.

I've replaced a lot of batteries over 50+ years. Most of those there were no electronics to sweat over.

The ECM issue spooked me.

Not for my tractor, but more for my trucks/cars.

 

[je1279]

Thanks much.

I've replaced a lot of batteries over 50+ years. Most of those there were no electronics to sweat over.

The ECM issue spooked me.

Not for my tractor, but more for my trucks/cars.

I'm not too far behind you in age and I have worked on all sorts of vehicles my entire life. Was definitely easier when cars/trucks didn't have a mini-computer for every component that is ultimately controlled by a larger computer. I miss the days where you only needed to confirm that it had air, fuel, spark and compression (no spark necessary for diesels ).

 

[GreensvilleJay]

I was taught to always remove the ground cable/strap first, then the power cable.
The reason is, with the 'ground' cable removed from battery, when ( not if..) you swing the wrench around to remove the 'power' cable, hitting the frame or any metal nearby will NOT cause sparks, scare you and needing several bandaids.

In most but not ALL vehicles, 'ground' will be the negative of the battery, 'power' will be the positive of the battery.

I've had several 6 volt, positive ground tractors, my combine was 12 volt positive ground and one had a 12 volt, positive ground with alternator but I'm betting 99.44% of all Kubotas on this forum are 12 volt, negative ground, but don't 'assume', check and confirm.

#6 small 'keep alive' battery is a neat trick BUT keep in mind, depending on how the tractor is wired, the +12 battery cable could be 'hot' so don't let it touch 'ground' ! The 'keep alive' battery is also great at keeping time and radio info valid. Some BMW, you change battery, kill radio power, have to go to dealer to 'enable' it again !! A 'security' feature....

 

[Russell King]

I understand that in many new cars there are two separate batteries already installed, one for the starter and another for the accessories. I assume they are both charged by the same alternator but no idea how they are actually installed and wired.

 

[lugbolt]

we were told in training that on all of the new stuff (2013 at the time), that when replacing a battery, you should make good practice to let the tractor SIT for at least an hour after trying to start it, key removed and all accessories turned off, before disconnecting the dead battery. Theory was that some of the ECU's will hold power for a while and disconnecting them while they're "working" can damage them.

Never weld on a tractor without disconnecting the battery either, in fact it's probably good practice to disconnect the ECU's before doing any welding, be it an implement or attachment. Most of the ECU's are made by Bosch and while mostly reliable, they can be damaged due to high current, such as welding.

There was no specifics other than disconnecting ecu(s) when welding and letting it sit a while after turning the key to off before trying to disconnect the battery. Standard removal practices apply, disconnect neg first, then reconnect pos first.

On older equipment or any equipment that is in service for that matter, I almost always do a voltage drop test on both sides (pos and neg) before finishing up. A faulty negative or ground can cause all kinds of issues, particularly when a high current is requested (starting, glow). On the Grand L 10 and 30 series, possibly 40 series as well, the pos cable has a connection build onto it that feeds the entire tractor except the starter; and that connection often fails. It's a black "box" near the positive battery terminal, you can kinda see where the cable splits off at that "box" looking thing. A very common failure point for sure.

also on the cables (while on the subject), those temporary battery cable repair things that all auto parts store have. The clamp style, you push the cable into the strap and tighten the two 11mm/7/16 bolts. They have caused numerous electrical system problems over the years, and I'm dealing with one in front of me as we speak that has electrical system troubles, I suspect due to this cable repair deal. People are too cheap to buy a new battery cable, and too ignorant to repair it properly so these end up staying on the equipment until "it won't start", and the connection fails and takes out the ECU--which I suspect is what happened on the one I'm looking at.

 

[North Idaho Wolfman]

I understand that in many new cars there are two separate batteries already installed, one for the starter and another for the accessories. I assume they are both charged by the same alternator but no idea how they are actually installed and wired.

There are quite a few that use either a fixed lithium battery or super caps to hold a charge for quite a long time.
I'm being told that more likely than not it's not changing out of a dead battery that causes issues but trying to start it with a dead battery.
Electronics don't like the low voltage or the high voltage spike from jumping it or boosting them.

 

[6869704x4]

Never weld on a tractor without disconnecting the battery either, in fact it's probably good practice to disconnect the ECU's before doing any welding, be it an implement or attachment. Most of the ECU's are made by Bosch and while mostly reliable, they can be damaged due to high current, such as welding.

That's why Joe uses a torch

 

[GreensvilleJay]

It's usually voltage spikes that fry silicon not low voltage. I've got computers running off 1.5 volt batteries for years.
Spikes though can be 50-300 volts, short in time ,high in voltage.Sadly the 'ECU' can be protected for pennies but some bean counter somewhere says 'no', so it's not done.
Instead of waiting an hour you can put a 'dummy load' as the 'battery'. It'll slowly drain away any residual energy in primary power supply section,something leftover from vacuum tube days.

 

[lugbolt]

It's usually voltage spikes that fry silicon not low voltage. I've got computers running off 1.5 volt batteries for years.
Spikes though can be 50-300 volts, short in time ,high in voltage.Sadly the 'ECU' can be protected for pennies but some bean counter somewhere says 'no', so it's not done.
Instead of waiting an hour you can put a 'dummy load' as the 'battery'. It'll slowly drain away any residual energy in primary power supply section,something leftover from vacuum tube days.

low/dead batteries are often the root of a spike, when the owner/user hooks up their diesel pickup to jump it off, then "let the alternator charge it". The spike from the truck can be significant.