A more suitable battery?

[Wooster]

It has been said before that the auxiliary Battery fitted by Toyota to hybrids are not the best option.  Being 'standard' car batteries, their main objective is to be able to keep a starter motor happy by being able to supply 200+ amps.  This is never going to be needed in a Toyota hybrid.  The maximum I've seen is 20 amps for up to 10 seconds.  (More complete details below)

This 'high current /short duration' criteria needs lots of plates - and to squeeze them into a casing, they are fairly thin.  These are easily damaged if they suffer deep discharge.  A deep cycle leisure Battery (think golf buggy or mobility scooter) have fewer but thicker plates.  This means they are not capable of sustaining requests for 200+ amps, but do allow a much deeper (and longer) discharge without any damage.  In my mind, this sort of Battery would be more suitable to a hybrid.  Most leisure batteries are AGM.  So, I wonder:

1) Do any of you think the same?

2) Has anyone tried to find and successfully fit a deep cycle leisure battery to a hybrid?

 

 

 

Start up details:  I would imagine my old (2010) Prius sucked the same power from the aux battery as my current (2018) Auris.  Open the driver's door and 8 to 20 amps is consumed for 7 to 10 seconds. When the ignition button is pushed, 8 amps is drawn for up to 5 seconds. After that, the duties of the auxiliary battery are finished.

 

 

 

[flash22]

Is the Battery in the boot ? If so it will be an AGM type, what are designed as a deep cycle Battery - low current, higher voltage, and slow charge

Typically, you will get 7-10 years from the stock AGM Battery

 

If it's the lead acid type under the bonnet, you could go to an EFB or AGM, but you will not get the best from it, charging - you will be capped by what the HSD DC-DC can put out no matter what battery you put on it

8-10 amps is about right to pull in the HV contactor(s) in + other Aux systems

[Mooly]

My understanding having followed all the many threads concerning Hybrid owners having problems with discharged batteries is that the basic issue is that the background quiescent current draw is to high. This means the Battery exhibits a slow and progressive fall in its state of charge for vehicles that are used anything less than 'frequently'. The last 12 to 18 months has highlighted this even more with many using their cars less.

A current as low as 50 milliamps or so will over time reduce the overall state of charge unless the car is used frequently.

The above is the opinion I have formed from reading all the many threads on this subject. I wouldn't be surprised if this is addressed in future with manufacturers taking a more serious interest in low power design of the electronics systems.

[Wooster]

2 minutes ago, Mooly said:

... the background quiescent current draw is to high....

There was an early problem with the Auris drawing too much current when the ignition was off.  However, this was sorted with (I think) updated software.  It isn't a particular problem - I can leave my car for days and it starts perfectly.  I was posing a more theoretical question - is there a more suitable auxiliary Battery for a hybrid rather than one that is optimised to deliver 200+ amps for a few seconds. 

[Cyker]

Just be aware that AGM doesn't necessarily equal Deep Cycle - There are AGM starter batteries and flooded deep-cycle batteries too; As the OP mentions, it's all down to lead-plate thickness.

Usually deep-cycle batteries have much lower CCA ratings than starter batteries.

I think Toyota learned their lesson and started fitting deep-cycle batteries as standard in their hybrids, but the batteries are still relatively small, and the electrics power draw fairly high.

There are people selling lithium ion replacement packs, but they are quite expensive...!

To be fair tho', this problem is not limited to hybrids - A lot of modern cars will eat their 12v Battery if they aren't used for too long - The infotainment computers need a lot of power and if the car is always connected to the internet there is not way to avoid the high usage. Just be glad you don't have to code replacement 12v batteries to your car to make it work, unlike a lot of german cars!

 

[flash22]

The hybrid doesn't need a high current Battery nor CCA - as it doesn't crank, the Battery is just for auxiliary use the biggest draws at start or the brake servo pump and the contactors what's less than 20 amps total

https://www.yuasa.co.uk/info/technical/agm-efb-explained/