Leave battery cables hooked up while on tender?

RedMF40 · Nov 12, 2018

I have a car that will be on a battery tender all winter. Won't be driven at all. Is it better to unhook the battery cables or just leave them attached? Normally not an issue on most cars, but this battery is buried in the trunk and I'd just as soon leave it alone if I can. Thanks for any help. (car is 1995 Miata in case you were thinking it was some Italian supercar LOL)

David G · Nov 12, 2018

I leave mine hooked up, keeps computer running.

Steve@Advance · Nov 12, 2018

If the car has a good reputation for not draining the battery, you can leave it connected.

But if it has extra electronic accessories, alarm system, after market sound, etc, wouldn't hurt to disconnect it.

Another concern would be rodent chewing.

ss55 · Nov 12, 2018

If it won't be driven for several months, I disconnect one of the battery cables to reduce the drain on the battery. That way I can get by with only charge the battery once every two months with no problems.

rustyfarmall · Nov 12, 2018

I leave the cables hooked up.

MarkB_MI · Nov 12, 2018

I'm not sure about your car, but most newer cars store radio settings, PCM data, etc. and will lose all that information if power is disconnected for very long. It's better to leave the battery hooked up; the trickle charger can easily handle the slight battery drain of the electronics.

guido · Nov 12, 2018

Hello RedMF40,

Leave the cables on. One thing you may one to consider is a timer for the
charger-maintainer. 6 to 12 hours a day will keep the battery ready for use. You can monitor the voltage and adjust the time as needed.

Guido.

Bruce(OR) · Nov 12, 2018

'95 Miata. . . I just sold one of those with the ABS, power everything, no hard top, 1.8 4 cyl engine I believe.
Leaving the battery connected keep the computer alive. The parasitic drain should be about .25 amp. You can check it yourself with a DVOM.
Dicsconnect the pos batt cable and then hook up the meter between the pos batt cable and post. You might find an initial surge of amperage
for about 30 seconds as the computers wake up and then go back to sleep. That reading after 30 seconds or so, will be your parasitic drain
and as I said, should be around .25 amp with your 'basic' car as you have.
I have a few vehicles parked around here, most on tenders and all hooked up. I do not desire to play with cables when I desire to start them
and do not desire having to go through driveability problems as the computer has to relearn idle strategies, fuel trim and what not.

RedMF40 · Nov 12, 2018

Thanks, all. Battery cables stay on. Just replaced battery and parts guy told me it's same as a riding mower battery. About 375 CCA and same size. The thinking is prob that no one will be driving this car in winter anyway so just put a little battery in it.

Thanks to the Miata owner for the tips--this car is the special edition with all the bells and whistles, which really isn't that much. Power windows and air cond and ABS come to mind. I'll check what the draw is with car turned off and just sitting. Seems I only get 2-3 yrs out of these small batteries.

TGP · Nov 12, 2018

That's a small battery.
I doubt you will ever get any life out of it.
The Tender Will Help.

The Alt. on that car isn't much better.
It might be high amp rated but won't do it very long either.
Tom

BarnyardEngineering · Nov 12, 2018

If you have a true battery maintainer it will stop charging when the battery is full, and only top when the battery voltage drops.

I have several, I put them on the batteries in the fall and take them off in the spring.

Hobo,NC · Nov 12, 2018

If your maintainer has auto float control hook'er up and walk away.
You can take a battery cable off it won't hurt nuttin your call... When I put them on my tractors it took a day before they went into float mode for the ell of it I unplugged them the maintainer went into charge mode. I got the instructions out read them I don't think its a good I.D. to cycle them leave'em alone and let them do there thang...

RedMF40 · Nov 13, 2018

(quoted from post at 16:00:26 11/12/18) If you have a true battery maintainer it will stop charging when the battery is full, and only top when the battery voltage drops.

I have several, I put them on the batteries in the fall and take them off in the spring.

Yes, understood--charger/maintainer will stay hooked up all winter. What I was wondering is if anyone disconnects the vehicle's battery cables as an extra precaution. Don't want to find that I have a fully-charged battery in spring, but the car's electronics are fried. Appears not to be an issue.

Russ from MN · Nov 13, 2018

Our truck (15 Silverado) sits for 3 months, I disconnect 1 cable and leave it, no tender. I have heard horror
stories about them starting fires, and it's not necessary.

Leave battery cables hooked up while on tender?

RedMF40

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David G

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Steve@Advance

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ss55

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rustyfarmall

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MarkB_MI

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guido

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Bruce(OR)

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RedMF40

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TGP

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BarnyardEngineering

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Hobo,NC

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RedMF40

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Russ from MN

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