400H 12 Volt Charging

[phil m]

After reading various members experiences of flat 12 volt batteries I'm opting to regularly garage charge the one on my recently acquired 400h, question is can I leave it connected under charge ?

[Duncan Roberts]

After reading various members experiences of flat 12 volt batteries I'm opting to regularly garage charge the one on my recently acquired 400h, question is can I leave it connected under charge ?

Why - does it stand most of the time?

Subject to the instructions for the charger it should be OK but it is probably not the best practice.

[malibu]

I've just acquired a RX400h and I'm fully aware of the Battery issue and was wondering whether it would be okay to attach the Battery to a charger to get the vehicle to start should it fail one morning outside my house.

Of course should this happen a couple of times it would be a sign of a failing Battery and probably wise to replace as opposed to continually charging a failing Battery.

In addition to this I can only assume that one doesn't get any prior warning that this Battery will fail or is starting to fail. Am I correct in thinking that a garage could do a 'health check' on the Battery so, at best, I'd have an indication that the Battery is nearing the end of it's life?

Finally, if I were to replace my 12v with a brand new Battery, then leave the vehicle at the airport for a month, does anyone know whether this new Battery would fail to start the car, or should I conduct my own experiment on behalf of LOC?

[ColinBarber]

I've just acquired a RX400h and I'm fully aware of the battery issue and was wondering whether it would be okay to attach the battery to a charger to get the vehicle to start should it fail one morning outside my house.

Of course should this happen a couple of times it would be a sign of a failing battery and probably wise to replace as opposed to continually charging a failing battery.

In addition to this I can only assume that one doesn't get any prior warning that this battery will fail or is starting to fail. Am I correct in thinking that a garage could do a 'health check' on the battery so, at best, I'd have an indication that the battery is nearing the end of it's life?

Finally, if I were to replace my 12v with a brand new battery, then leave the vehicle at the airport for a month, does anyone know whether this new battery would fail to start the car, or should I conduct my own experiment on behalf of LOC?

Hi Paul

After a week away earlier in the year my Battery failed to start the vehicle, it wasn't completely dead as it disarmed the alarm and opened the doors etc, and I did exactly that - connected up a Battery charger, waiting 60 seconds and then started the engine.

The 12v Battery isn't actually used to turn over then engine so the amount of current required from the Battery is quite low. The voltage however needs to be high enough for the main systems to work and to go 'Ready', then the hybrid Battery takes over and starts the engine.

My Battery is 7 or 8 years old now so it only lasts a week, a new one would be fine for two+ weeks. I will replace it before the next winter with the Bosch replacement which has a slightly larger capacity than the OEM one. With that one 3 weeks is fine, may be 4 but I wouldn't guarantee it.

In terms of a health check, I think the Battery would check out fine unless it really is faulty. The main issue is just the size of the Battery - it really is too small a capacity to keep the alarm etc. running for weeks and once the Battery is a few years old some of that precious capacity goes so you are in a worse state.

Why is the Battery so small? I can see if from the designers point of view, the Battery isn't needed to start the engine so it can be much smaller than for a normal vehicle but I think they went a bit too far. Whether that was to save space, weight (economy) or cost I'm not sure. All the Toyota hybrids seem to be the same, the Battery in the second generation Prius is very small and they are prone to expire after just a few year (probably because they are being deep cycled too often by almost becoming flat when people go on holiday).

[Tyrosman]

There should not be a problem to leave a lead acid Battery connected to a charger, provided it is a voltage/current regulated (intelligent) device, most modern Battery charges are. What you are effectively achieving is a 'float charged Battery system' whereby the current requirements of your onboard electronics are provided by the mains powered charger with the vehicle Battery just sitting there, maintained in a fully charged state.

This is common practice in industrial/commercial situations to provide emergency power when required. Where I used to work they had a large lead acid Battery float charging system to provide power if the mains supply failed. When the system was decommissioned, after 30 years, the batteries where still in perfect condition. NEVER leave a lead acid Battery in a discharged

state, the plates will suffer from sulfation.

See link http://batteryuniversity.com/learn/article/sulfation_and_how_to_prevent_it

I may be missing something here, but it does seem that most problems appearing in posts on this forum concern the RX Hybrid models. I think I will stay with my RX300.

[Tyrosman]

For some unknown reason the link I posted on my previous post became distorted. I will now try again, if it does not work the I apologise.

http://batteryuniversity.com/learn/article/sulfation_and_how_to_prevent_it/

Nope, still didn't work. Ok when I typed it but corrupted when posted, any ideas why?

[Duncan Roberts]

For some unknown reason the link I posted on my previous post became distorted. I will now try again, if it does not work the I apologise.

http://batteryuniversity.com/learn/article/sulfation_and_how_to_prevent_it/

Nope, still didn't work. Ok when I typed it but corrupted when posted, any ideas why?

L

Link works for me.

[ColinBarber]

I may be missing something here, but it does seem that most problems appearing in posts on this forum concern the RX Hybrid models. I think I will stay with my RX300.

It is because the 12v Battery on the hybrid model is very low capacity and therefore drains quickly from the alarm and other live electronic systems.

The Battery on the non-hybrid models is much bigger, because it has to start the engine.

p.s. both you links work for me.

[malibu]

Interesting link, it works fine, however I still wouldn't swap for a RX300; horses for courses, I suppose.

The new sensation I'm experiencing of gliding silently around the country lanes of Cornwall, windows down, (sun) moon roof open, traversing on Battery power only, whilst the air is filled with birdsong is most pleasurable.

[Tyrosman]

Fine for you Paul but traversing the M3/M4/M5 with windows etc., tightly closed, ear defenders on (only kidding). Not only that but navigating urban roads could be a danger to pedestrians as they may not hear me approaching. Alright let me be honest, I am just envious of you being in Corwall! Just a word of warning, keep a lookout for those pesky seagulls if you happen to walk around Padstow (or is it Padstein?) with a bag of chips in your hand.

[Surfbum]

Phil,

I have a 2007 400H and had the same Battery dying problem right from brand new.Each time it happened I called Lexus and they changed the Battery.Its a manufacturing fault and Lexus knew about it but had no 'fix' for it.I work away and my car was left for many days with-out being used and I would always find the Battery dead on return to the uk.

I finally got round the problem by getting my Plymouth lexus dealer to permantley live wire the power socket on the floor and plugging a solar power charger(Solar cells layed on top of dash) into it when the car was not being used.It continually trickle charges the Battery.

I have not had a dead Battery since doing this.

Its a poor excuse for a car with all the extras I ordered that cost over 50K at the time to keep the Battery running but it works.

I understand that on the new 450H they put a larger Battery in thus getting round this problem.

I hope they do the same with the new baby RX due out next year,,,lessons learned I hope.

Derek

[ColinBarber]

as I've previously said, if you are replacing the Battery don't get it from Lexus otherwise you still have the same problem. Get the Bosch replacement which is the same physical size but has a slightly larger capacity which gives you a few more days.

This isn't a manufacturing fault, it is a design fault. The Battery capacity is just too small, there isn't something that isn't working as it should which is drawing too much power - everything is working correctly however that normal power draw is too much for the Battery that was chosen.

I do believe the 450h has a larger Battery but not by much, owners still run into this issue.

[malibu]

So Derek, was that your black 400h I spotted at Lexus Plymouth the weekend before last, parked up with the solar charger on the dashboard, plugged in and trickling?

[Tyrosman]

Maybe Lexus could, in future, convert the hybrid's sun roof into a solar panel?

[malibu]

Probably it would only be necessary to incorporate a solar panel into the top of the black boot spoiler.

Blimey, I think I've just invented an after market idea. Remember, you heard it first here folks; now where can I find me a Chinese manufacturer? Patent applied for :)

[CJHYBRID]

Phil,

I have a 2007 400H and had the same battery dying problem right from brand new.Each time it happened I called Lexus and they changed the battery.Its a manufacturing fault and Lexus knew about it but had no 'fix' for it.I work away and my car was left for many days with-out being used and I would always find the battery dead on return to the uk.

I finally got round the problem by getting my Plymouth lexus dealer to permantley live wire the power socket on the floor and plugging a solar power charger(Solar cells layed on top of dash) into it when the car was not being used.It continually trickle charges the battery.

I have not had a dead battery since doing this.

Its a poor excuse for a car with all the extras I ordered that cost over 50K at the time to keep the battery running but it works.

I understand that on the new 450H they put a larger battery in thus getting round this problem.

I hope they do the same with the new baby RX due out next year,,,lessons learned I hope.

Derek

Have been reading the aux Battery problems re the 400h with interest and it is my biggest worry about owning the car which incidently I only pick up today.Read about solar chargers in the posts and then saw that the ignition turns the power off and thought oh no that wont work either. Permanent power to the socket is a great idea (just like at home) and is hopfully the real solution tomthis problem for owners.Must say this is a major issue that Lexus should not have missed. Most people need to leave their cars forma week or two when they go on holiday and should not have this worry.Buying mine second hand from non Lexus dealer.They have agreed to fit a new aux Battery as part lf the deal. (exide) .Will eventually replace with best Bosch substitute I can find as have good experience with them.

Thanks for your post Derek as I think it is the solution to the problem.

Chris