Dead Battery advice

[rcharrette]

Hi all we are camped out and my battery is dead on my LR3. I think my 3yr old was playing around in there! Anyway, I'm trying the only option I can think of. I've got jumper cables running from my deep cycle camper battery over to my Rover battery and I've got the generator going to keep my camper batteries topped up. I've got a voltmeter and I charged the Rover battery to 12.5V. It took about 20 minutes or more. I tried to start and it barely turned over and the battery went down to 9.5V from the effort.
I'm not sure this is going to work? Do I just need to let it charge longer or should I start looking for a jump?

 

[keeper1616]

I'd make sure the battery is at or above 13.2 prior to attempting to start - "full" on a 12v battery is in the range of 14.2-14.4 or so. Some people will say 12.7v is 'fully charged' but it depends on the type of battery and how old it is. 12.5 definitely isn't 'full.'

Whenever I've had a dead primary battery, I've disconnected the generator, left the house battery connected, and cranked it over, no issues for me doing that! FWIW, I have no idea if that's 'correct' or not, it just works for me!

 

[DaveInDenver]

It went to 9.5V and stayed there after you stopped cranking? The voltage may be that low while actually cranking but it should jump back up.

How far down was the battery discharged? Perhaps /really/ dead, like around 10V? If so that sounds like you may have reversed or shorted a cell, which is typically an uncorrectable failure. Jumping it from a good battery or putting it on a very high current charger may fix it, but if you do get it started I'd personally drive directly to an auto parts store.

 

[rcharrette]

Thanks all for the replies. I finally got it charges to 13Volts and it cranked up for me! Took it for a good long cruise to get it charged back up. I guess Ill find out in the morning if I did an damage when I go to restart it!
@daveindenver: It did go down to 9.5V and stay there after trying to crank it when I made this original post. However all seems ok so far. I took it for a long drive. Ran into a store came back out and it cranked over strong. We'll see after sitting over night........

 

[DaveInDenver]

Think positively, you'll be fine and probably still have 8 lives left on the battery.

 

[eloist]

I learned my lesson camping in my LR3... always turn the interior lights off.
I killed my battery dead by not doing that on a weekend trip.

In fact, I leave them off all the time now haha!

 

[Campndad]

If you press the center button on the front curtesy lights and hold it will then blink. Killing the inside lights when the door is open. Repeat to bring it back. Great feature we have used while ⛺️


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[dwh]

There is an effect called surface charge.

It takes time for electricity to move from the liquid electrolyte to the lead plates, and vice versa. So what happens during charge or discharge is that electrons build up on the surface of the lead plates. That's called the surface charge, and it gives a deceptive voltage reading.

That's why you have to let the battery rest for a couple hours with no charging/discharging to let the surface charge dissipate in order to be able to read the "resting voltage" - which is an accurate measure of battery status.


You saw 12.5v after 20 mins charging, but you were reading the surface charge - the battery sure didn't go from dead to 80% full in 20 minutes.

And a long drive usually isn't good enough to get it back to 100%. You should put that battery on a shore charger overnight.

 

[zelatore]

There is an effect called surface charge.

It takes time for electricity to move from the liquid electrolyte to the lead plates, and vice versa. So what happens during charge or discharge is that electrons build up on the surface of the lead plates. That's called the surface charge, and it gives a deceptive voltage reading.

That's why you have to let the battery rest for a couple hours with no charging/discharging to let the surface charge dissipate in order to be able to read the "resting voltage" - which is an accurate measure of battery status.


You saw 12.5v after 20 mins charging, but you were reading the surface charge - the battery sure didn't go from dead to 80% full in 20 minutes.

And a long drive usually isn't good enough to get it back to 100%. You should put that battery on a shore charger overnight.

What he said. Most people don't understand how long it actually takes to bring a battery to 100%. Without getting techy, let's just say your alternator won't do it and you need a good overnight with a decent multistage charger.

 

[jymmiejamz]

I learned my lesson camping in my LR3... always turn the interior lights off.
I killed my battery dead by not doing that on a weekend trip.

In fact, I leave them off all the time now haha!

Somewhat unrelated to the original topic, but don't the interior lights in the LR3 time out if they are left on? I would guess you had a marginal battery to begin with if the interior lights killed the battery.

 

[eloist]

It was from opening and closing the doors every few minutes while camping in the rain.

I don't doubt that my battery was low to begin with, but you should definitely use the camping lights feature when you're in the woods

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[Mx468]

Get one of these or something similar...

I always carry one of these for those just in case moments. Cheap investment but works great! I don't have this one exactly but one similar.

 

[rcharrette]

Thanks again everyone, as I said I got it going finally and it's been starting fine ever since. I believe I solved the root cause of the problem. Keeping my 3 year old out of the truck when it's parked

 

[perkj]

The other thing to consider doing is to upgrade every single bulb on the interior of the LR3 (there are a lot of them) to LEDs. Given the number of interior lights, it'll be about a $200+ investment, but the LEDs consume significantly less power than the normal bulbs. Given that my LR3 is my primary camp vehicle, I made the switch and couldn't be happier.

The other thing you should consider doing is running a second battery under the hood with an isolator. I utilized the Traxide USI-160 LR3 kit: http://www.traxide.com.au/complete-diy-dual-battery/land-rover-dbs-kits/discovery-3-dbs-kits/ . The USI-160 has a nice feature where you can flip a switch in the cab to jump the primary battery if needed without needing to crack open the hood. In addition, I modified the area for the 2nd battery to run a Group-31 Deka AGM 100 ah battery there (typically you can only run a Group-34 54 ah ) as well as upgraded the primary battery to a Deka Group 49 AGM (@ 92 ah). Details here: http://forum.expeditionportal.com/t...tery-to-the-AUX-battery-location-in-the-LR3-) . I like having a lot of amp hours to run my fridge and given how much power these LR3s consume every time the ECUs get woken up (i.e. door or hatch open). I also carry a 100W solar panel to keep things topped off when settled into camp. Better to be safe than sorry.

 

[keeper1616]

The other thing to consider doing is to upgrade every single bulb on the interior of the LR3 (there are a lot of them) to LEDs. Given the number of interior lights, it'll be about a $200+ investment, but the LEDs consume significantly less power than the normal bulbs. Given that my LR3 is my primary camp vehicle, I made the switch and couldn't be happier.

$200? I spent $63, although I may have missed one or two - there are a lot. I know I didn't do the vanity mirrors, I think I got the rest of them, including the puddle lights. I got 16 of these: https://www.superbrightleds.com/mor...tower-miniature-wedge-retrofit-car/1127/2674/