2006 RX 400h 12v battery - upgrade for winter discharge

[Lozsta]

Hopefully someone can help me.

My old rx400h is great most of the year round. Unfortunately due to my not daily use the Battery discharges very quickly in cold weather. I have to buy a new Battery yearly and then the next year it will discharge within 48 hours of a temp drop.

I read a while back about this causing issues with the car not wanting to start properly and giving the ACS (cant remember the details exactly) error when starting, it keeps asking you to put it in park when it it.

I am hoping someone has the knowledge required to help me, I did read that some were using leisure batteries or similar with higher mAH ratings to help with slowing the rapid cold weather discharge. There were others who mentioned issues with this but I am really hoping I can make it through one following winter without the cost of a new Battery.

Thanks in advance for any help :)

[Herbie]

Every time a Battery goes into a deep discharge (deep enough to need jump starting) it suffers a bit of damage that lowers its capacity, which means that on its next charge it can't take as much as it did before.

If you don't use the car often enough to keep it charged then ideally you need to connect the Battery to a trickle charger. A 'standard' charger will quickly squirt about 5A in if needed but a trickle charger does exactly what it says on the tin - it trickles a small charge in all the time, keeping the Battery charged and ready to go when you need it.

[Russell Wheeler]

Yep, it's a pain, mine is exactly the same. I use a solar panel in summer and a Battery disconnect in winter. I also carry a jump pack in the glove box, so have never been let down.

[Lozsta]

A jump pack? I wasn't aware that you can jump the rx400h due to the big Battery. I have a solar panel and the OBD port but it doesn't seem to help.

I am looking more for a higher MAh Battery like a leisure Battery that will hold charge longer.

[Russell Wheeler]

You can jump the 12v starter Battery from a 12v source. Just don't jump anyone elses car from yours. And like you I have looked for a larger capacity one, there isn't space under the bonnet - hence all the problems. I believe they fixed it in 2009 with the next generation by putting a normal sized Battery in - which is no help to anyone with an earlier 400h

 

[Russell Wheeler]

I use one of these in the winter. It's not a very elegant solution but does work.   https://www.amazon.co.uk/Battery-Isolator-Switch-Power-Leakage/dp/B07J34S5DH/ref=asc_df_B07J34S5DH/?tag=googshopuk-21&linkCode=df0&hvadid=224431698442&hvpos=&hvnetw=g&hvrand=16332938530141334352&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1007098&hvtargid=pla-757317365237&psc=1&mcid=3f6a06c2dbf432e1a17c232a91df02e9

[Lozsta]

Hi Russell thanks for the advice but this review unfortunately counters the use quite well

 

"Don't waste your time and money on this junk. It might be fine for a leisure Battery or something that does not move about but it is not sturdy enough for a car. The thing is poorly made, does not clamp over Battery terminals securely without a shim. I removed mine after a couple of months as it was causing electrical issues with the car. Connection was not secure enough and components were not getting sufficient power."

[Lozsta]

Really I am looking for a different Battery to put in that doesn't require a trickle charge/bnattery tender/odb connected solar panel/screw top disconnector. There has to be a Battery out there which will not discharge overnight or within 24 hours.

[NemesisUK]

17 minutes ago, Lozsta said:

There has to be a battery out there which will not discharge overnight or within 24 hours.

The standard OEM Battery won't discharge overnight, unless you have a parasitic drain. You need to find out why it's discharging so quickly or you will simply drain the 'bigger' Battery..

[Russell Wheeler]

15 hours ago, Lozsta said:

Hi Russell thanks for the advice but this review unfortunately counters the use quite well

 

"Don't waste your time and money on this junk. It might be fine for a leisure battery or something that does not move about but it is not sturdy enough for a car. The thing is poorly made, does not clamp over battery terminals securely without a shim. I removed mine after a couple of months as it was causing electrical issues with the car. Connection was not secure enough and components were not getting sufficient power."

I purchased an blank OBD port, and soldered the connections from the solar panel to the positive and negative points in the OBD, so the solar panel connects directly into this. Your Battery should not discharge overnight. Mine takes about a week - which is not ok for me - as sometimes the car does not get used from Month to Month. I have heard of a solution where a larger Battery is located in the boot  - however this requires significant changes to the wiring as you need to get the power from the boot to under the bonnet.

[Lydiamight]

There must be some parasitic drain on your Battery for it to discharge so much. 

I have a 2007 Rx400h and it was still using the original factory fitted 12 volt Battery until earlier this year when I had to replace it after 15 years of usage.

Even before replacement I could quite happily leave it for four weeks whilst we were on holiday and it would start just fine upon our return.