Flattened auxiliary battery - any consequences?

[NightPHEVer]

I recently managed to completely flatten my auxiliary battery (inadvertently left too much switched on while I was changing a flat tyre in 'challenging' circumstances, hey though at least I had a spare wheel and tyre! - see 'unequal tread depths' post). Even the hazards wouldn't work, just curiously the rear wiper, very slowly, even though it wasn't actually switched on at the time. Nice Mitsubishi breakdown man Adam jump started it, everything ok and auxiliary battery showing 100% condition on his measuring device. So are there likely to be any consequences of this battery flattening faux pas? DId this about three weeks ago and all seems ok - do these auxiliary batteries really cost £600? What type of battery is this? It's actually a bit bigger than it looks when you take the cover off. How long is one likely to last.

 

[Tipper]

Considering that these batteries take no heavy starting duty and their load is mainly lights and auxiliaries, plus the control systems of course, they actually seem a little under sized for their duty. I would have thought a higher Amphr capacity would have been needed but not one capable of providing high starting current. I've heard of several that have died but usually from leaving the auxiliaries on without the car being in 'ready' state which is when the battery is charged.

Quite why they are 'specified' so as to be so expensive seems odd considering their light duty. As it has no starting current needed I would think a 'leisure' battery would do the job nicely. I have seen a Yuasa battery being suggested as a replacement and even one from Halfords so I would tend to go with the correct Amphr size of whatever make I fancy and let the car deal with the charging needs.

 

[HHL]

Somewhere in the manual it states that the BMU will lose data (maybe reset), but that won't happen until it is disconnected for longer.
My friend did that for a few hours while installing a wiring for a transceiver and it seemed to have no ill effects.
As for pricing, after all it is supplied by the same people that can charge many hundreds for a key replacement without blushing.....

 

[Steeeeve]

'Somewhere in the manual it states that the BMU will lose data (maybe reset)' , little off topic but I wonder if this does reset the Bmu, I assumed the data was non-volatile. Question is, would there be any Ill effect from disconnecting the aux battery overnight and isolating the traction battery overnight to test.. Quite an intriguing idea

 

[HHL]

'Somewhere in the manual it states that the BMU will lose data (maybe reset)' , little off topic but I wonder if this does reset the Bmu, I assumed the data was non-volatile. Question is, would there be any Ill effect from disconnecting the aux battery overnight and isolating the traction battery overnight to test.. Quite an intriguing idea

Well, I believe the BMU does have a backup battery in it, but I don't know whether that just holds enough charge to enable the aux battery replacement without resetting it.
I did notice that my friend's SOH was quite a bit higher than mine last time we checked (about 6 months ago). That was some time after he had installed the radio and had the aux disconnected for nearly a day (incidentally, it seems impossible to find a place in the firewall to route another cable into the cabin).
At the time, his showed 96% and mine 90, from memory, and I was surprised as the cars were very close in built date and his had about twice as many km on it than mine.

 

[greendwarf]

'Somewhere in the manual it states that the BMU will lose data (maybe reset)' , little off topic but I wonder if this does reset the Bmu, I assumed the data was non-volatile. Question is, would there be any Ill effect from disconnecting the aux battery overnight and isolating the traction battery overnight to test.. Quite an intriguing idea

Well, I believe the BMU does have a backup battery in it, but I don't know whether that just holds enough charge to enable the aux battery replacement without resetting it.
I did notice that my friend's SOH was quite a bit higher than mine last time we checked (about 6 months ago). That was some time after he had installed the radio and had the aux disconnected for nearly a day (incidentally, it seems impossible to find a place in the firewall to route another cable into the cabin).
At the time, his showed 96% and mine 90, from memory, and I was surprised as the cars were very close in built date and his had about twice as many km on it than mine.

Perhaps that's all the dealer does in these semi-mythical BMU resets that result in apparent increased SoH - disconnect the aux battery overnight. :lol:

 

[MikkB]

INice Mitsubishi breakdown man Adam jump started it,

I wanted to ask if it was possible to jump start the PHEV, obviously it is. I have a little mobile jump start battery - out of interest, how should I go about jump starting the PHEV if I needed to? As I recall when the battery cover in the boot is opened only one terminal is exposed.

 

[Regulo]

There's a designated terminal in the engine bay fuse box for the purpose. See section 9 of the manual.

 

[MikkB]

Ah I see, thank you. That might be tricky with the very short cables that come with the compact jump starter I have, I guess I would need some sort of extender cable for at least one side. At least I now know which end of the car I should be at.. :lol: Cheers.

 

[Regulo]

You don't have to use the earthing point in the diagram. If you can find a nearer good earth, use that. It's probably recommended to use that one, to alleviate the risks of short circuits. I'd go out and have a look, but it's P'ing down here!

 

[ThudnBlundr]

Anything metal bolted to the engine or bodywork would do as an earth

 

[MikkB]

Anything metal bolted to the engine or bodywork would do as an earth

That could be tricky.. the Bodywork seems mostly plastic to me..

 

[elm70]

Perhaps that's all the dealer does in these semi-mythical BMU resets that result in apparent increased SoH - disconnect the aux battery overnight. :lol:

It would be nice ... but I think it is not enough

I do disconnect the 12v battery for 5/10min every 3 months for avoid ICE to kick in for burn "old" fuel

Unfortunately my SOH never jump back to 100%

But, on the very next trip .. my EV guessed range jump to the magic 52km .. but it does drop very fist while driving

I guess it lose the last average consumption on the previous trip and it set the average consumption to match the 52km range with the known SOH

Only thing I lose on removing the battery .. is the previously cabin temperature (it does goes back to 22deg) .. and the trip history, and charging history in the MMCS

 

[FleetOfFoot]

Hi all,

I'm new here, so please go gently with me.

My wife's Outlander PHEV recently wasn't used for a few days, and wouldn't start owing to a flat 12V battery. Breakdown man called out, and jump started it from his booster battery, took it for a drive, all good.

Roll on a few more days, and the same thing has happened again. Definitely no lights left on etc.

Not ideal, but I thought I'd get myself a Jump Starter booster battery, just in case this might become a regular occurrence. I tried to jump start exactly per all the instructions, and absolutely nothing doing. My sense is that the 12V battery is more flat this time. There are absolutely zero signs of life on pushing the start/stop button.

Does anyone have any suggestions for me please? I should also add that I have quite a swanky trickle charger too, capable of a charging cycle specific to an AGM battery etc. I hooked this up to the +ve in the fuse box and the recommended earthing point, but it appears not to even recognise the battery, backing up my notion that it is completely flat.

Is there a way to directly hook up to the 12V battery in the boot? (which I can't open unless there is a mechanical way of doing so somewhere). Apologies for all the newbie questions. Thanks in advance for any advice.

 

[michael8554]

Remove the carpeted floor, and then only a handful of bolts secure the moulded plastic section under that.

I would buy a basic Digital Voltmeter for a fiver and measure the battery voltage, which gives a good indication of whether it's Charged/Discharged/Doorstop.

https://haynes.com/en-gb/tips-tutorials/how-test-car-battery

 

[AndyInOz]

Common wisdom is that a lead acid battery is not much use after it has been run down to zero.

Probably time for a new one.

 

[ThudnBlundr]

It should start with a booster battery connected whatever the state of the 12V battery, even if it's flat. All it has to do is fire up the computers and connect the drive battery so there's not a huge current draw like a regular ICE. It doesn't care where the power is coming from as long as there's enough connected into the circuit via the jump-lead connections.

 

[FleetOfFoot]

Thanks very much for the quick responses.

I’m not sure why it won’t jump start then. I’ll try again. Out of interest there’s a similar metal bracket to the earthing point recommended in the manual on the same side of the engine compartment as the fuse box (where the +ve connection is); should this suffice? The Jump Starter battery leads aren’t particularly long.

Putting a meter across the 12V battery sounds like a good idea. Any suggestions as to how I open the boot with no electrics at all?

Thanks again everyone. I’ll report back.

 

[michael8554]

I would imagine that PHEVs with electric tailgate will have a manual opening handle on the inside.

Instead of removing the floor, buy the DVM and measure the volts across the jump point and earth with the 12V charger attached.

If the battery is taking a very large charge current the charger volts may be dropping too much.

Try jump starting with the battery neg disconnected in the boot, get the ICE running, then reconnect the earth.

 

[FleetOfFoot]

Thanks Michael. I’ll give it a go and report back.