preventing battery drain

[david fraleigh]

I have a Terex backhoe and the battery (relatively new) drains down if it sits for a week or so. I have thought to put in one of those devices that quickly disconnects one of the cables to the battery by turning a knob.. ( I have one on a truck that I rarely use and it works well to prevent the battery draining down ). Locistically it would be easier to put this device in a position where it would disconnect the negative cable... So I am wondering ... Does it really matter whether I am using the switch on either the Negative or the Positive cable. (I am inclined to think that it doesn't matter)... But here is my more pressing question. Does the fact that both the front and back buckets of the backhoe are very much in contact with the ground mean that if I don't switch-off the positive cable will the battery still have a path to drain to the ground even if the negative cable to the battery is switched off. My theoretical question essentially is whether or not a battery would drain down if a wire is run from the positive terminal to a rod driven into the earth (and nothing is attached to the negative terminal).. Thanks

 

[Industrial Toys]

I use them all the time. Mostly for security and fire. I use them on whatever post is more convenient.

I have never had an issue with the top of post ones with the removeable knob except the cheap ones have a very cheap alloy that will bust easily.

I have had an issue with contact on the cheap remote mounted ones, with the removeable switch paddle (key). The good more expensive ones seem to be OK.

 

[snymat68]

It doesn't matter what either terminal is connected to (earth, chassis, positive connections, etc).
If the current has no path to flow from post to post on the battery, the circuit is broken and the battery will not actively drain.
(All batteries will still slowly discharge over time, even if disconnected, simply due to internal chemistry and physics.)
You can interrupt the main battery circuit wherever you want and the result will be the same, battery disconnected. :thumbsup:
As K7LN said, if there is dirt on the battery, it wouldn't hurt to wipe it off, just in case the dirt is somewhat conductive and might create a (very high resistance) short that would slowly drain the battery.
On a related note, I have a battery in my trailer tongue box for my winch. I have it on a disconnect, and have a small solar panel attached directly to the battery to keep it topped off all the time.

 

[snymat68]

If nothing is attached to the negative terminal, you will not have any current drain from the battery.
If the top of the battery is very dirty, you could have a small drain from post to post.

Not to hijack the thread, but I noticed your username is your callsign. I just got my ticket back in August (jumped straight to general). One of the projects slated for my new tractor is digging trenches for my ground system. Between that and all my other projects it's going to be a busy summer! KC3LZH

 

[Industrial Toys]

A good battery should still start a tractor after several months, even in the cold. Based on experience,

It's more likely that a bridge will form from a positive terminal post to the hold down bracket. I like to cover hold down hardware with epoxy heatshrink to prevent this. But having said that, it does present a case for disconnecting the negative, so the positive post can't form a bridge to an ungrounded bracket.

 

[snymat68]

A good battery should still start a tractor after several months, even in the cold. Based on experience,

It's more likely that a bridge will form from a positive terminal post to the hold down bracket. I like to cover hold down hardware with epoxy heatshrink to prevent this. But having said that, it does present a case for disconnecting the negative, so the positive post can't form a bridge to an ungrounded bracket.

I never thought about that. Learn something new every day!

 

[George2615]

Agree with others that it shouldn't matter which post you put the disconnect on. As mentioned you should clean the top of the battery to prevent leakage across the top from post to post. Mix up a little baking soda and water and brush it across the battery top then rinse with clean water.

 

[Oaktree]

How much of a parasitic draw should a backhoe have? Does it have some sort of ECU in it that draws power when it's not running, or could it be there's an electrical problem somewhere that's causing the battery to drain?

The battery disconnect will solve the symptom, but there may still be a problem somewhere.

 

[Fallon]

How much of a parasitic draw should a backhoe have? Does it have some sort of ECU in it that draws power when it's not running, or could it be there's an electrical problem somewhere that's causing the battery to drain?

The battery disconnect will solve the symptom, but there may still be a problem somewhere.

None. At least for an older machine. A new machine with a computer would have an microscopic draw. Any reasonable ECU should shutdown after a while. Many car remotes, especially older ones, stop after a couple weeks to prevent the battery running down.

Even in the worst case it should last many months.

If your battery is dying in a month, much less a week, you have a problem. Some short or something somewhere in the wiring harness letting power seep through.

Wiring issues like this can be a huge pain to troubleshoot. You need to get & learn to use a multimeter. Start pulling fuses & see if there is any amp draw across the terminals is generally the best way to start.

 

[Fallon]

Oh, and a battery disconnect wont fix the problem, but will take care of the discharge symptoms. It will cause computers & clocks to reset, which may or may not be an issue (probably not on an old machine).

I put a solar cell & charge controller on my beater F250 rather than troubleshoot the phantom battery drain. It would kill the battery in a month or 2.

 

[DJ54]

It may be possible, that the diode(s) is/are out in the alternator, allowing the battery to drain.

 

[Texasmark]

You have a series circuit....think water hose. Any where you squeeze the hose you will stop the water. Anywhere you disconnect the wire making the loop out of and back into the battery will stop the current.....assuming all the circuits are involved, like right at either battery terminal.

I think the one I bought with a green knob is sized to fit the negative battery terminal. I don't agree with that ideology as most of the tractor is at battery - (these days with 12v systems) making for ease of accidental short circuits allowing current to flow......seems the designers followed the thought that you disconnect the negative battery terminal first when servicing a battery since (as I stated above) if your wrench accidentally connects to part of the tractor chassis or something connected to it you won't get sparking and current flow.

But changing a battery is one thing...disconnecting your system from the power supply is something else. I tried to expand one once for my home standby power unit as the + terminal was closer to my access area but it was a cast part (copper coated pewter seemed like) and as soon as I started expanding the connection it just broke off.

 

[jaxs]

You should track down the drain even if/after installing the disconnect. Why worry about it once the battery stops discharging? Because
if the drain is through the alternator,the alternator will soon stop working (possibly at the worst time). If drain is through a short,it can suddenly become a full blown short resulting in burnt wireing harness,battery explosion and/or tractor fire involving fuel tank. Fine example of "a stitch in time saves nine".

 

[k0ua]

Not to hijack the thread, but I noticed your username is your callsign. I just got my ticket back in August (jumped straight to general). One of the projects slated for my new tractor is digging trenches for my ground system. Between that and all my other projects it's going to be a busy summer! KC3LZH

Congratulations on getting your License, 73 James K0UA