General 500 twin air need advice please

[jrkitching]

Full hybrids often have a lead/acid battery to guarantee the engine will start when the ISG won't work because the lithium battery pack is dead

Yup. Of course, the lithium battery pack isn't completely dead - the ISG monitoring system will disconnect it before that happens. Anything powered by lithium batteries should turn off automatically before the pack reaches the point of no return - you can see this happening with your mobile phone & laptop .

 

[UFI]

I fully understand the risks of Li-Polymer batteries, however there are quite a few new chemistry Lithium based non reactive batteries designed for drop in replacement of lead acid bricks. http://www.racingbatteries.com.au/information.html

 

[bgunn]

Interesting website; would be good to see how these batteries last with long-term usage (in hot/cold conditions etc). I suspect the IBS would get a bit confused with the battery though, so probably more use for cars without S&S.

 

[jrkitching]

I fully understand the risks of Li-Polymer batteries, however there are quite a few new chemistry Lithium based non reactive batteries designed for drop in replacement of lead acid bricks. EG: racingbatteries dot com dot au

Have you read the care sheet for these batteries? Note in particular

The battery should be disconnected from the vehicle when not in use (you can also disconnect one lead, or fit a battery master switch/isolator). Don't assume that your ignition switch isolates the battery - it often doesn't.

also

And don't crank the engine on a part charged battery - make sure it's charged up to operating voltage (13.4 - 14.4V) first.

These batteries are designed for a specific purpose when weight is a premium and the car is thoroughly prepped each time it's used. I'd be concerned about their suitability for use as a drop-in LA replacement in a S/S car.

With smaller batteries, the charge/discharge logic can be built into the pack - LEGO produce couple of rechargeable LiPo boxes which are designed in this way. They have the advantage that you can recharge them with practically anything - the pack will automatically stop charging when the battery is full.

 

[bgunn]

These look a bit more 'OEM':

http://www.a123systems.com/lithium-starter-battery.htm

Bottom line is, to use them, you'll need to 'interface' the engine management/S&S with them so that the battery management works with the enhanced battery chemistry. I might investigate the reverse engineering of this - basically if I find out what the IBS feeds back to the ECM and replicate that with a different battery, it will work.

The Intelligent Alternator on S&S vehicles does regeneration & fast charging, and is controlled by the body computer, so if the body computer gets a valid set of data for the battery state according to the type of battery it is, it will work. We all know lead/acid is pretty unsuitable for constant starts and stops, and the dynamic charge requirements this needs, and battery tech is improving all the time.

 

[UFI]

One way or another I'm going for a lighter battery. My car isn't a daily driver so I can deal with some minor impracticality if need be. I lost all my links from researching this a while ago.
Some others: http://www.superstart.com.au/Products/ProductList/tabid/108/mode/details/bid/15/Default.aspx
http://www.braillebattery.com.au/

 

[bgunn]

With smaller batteries, the charge/discharge logic can be built into the pack - LEGO produce couple of rechargeable LiPo boxes which are designed in this way. They have the advantage that you can recharge them with practically anything - the pack will automatically stop charging when the battery is full.

I suspect this is going to happen over time for the 'micro hybrids' that we're now driving more and more of (i.e. cars equipped with S&S). Plainly, the requirement for replacing a lead/acid battery every 2 years (which is pretty much a given if you read any of the tech about it, and the 'benefits' of S&S are usually virtually gone by as little as 12 weeks) isn't sustainable, long term. I'm sure drop in replacement, better chemistry, batteries will appear.

 

[bgunn]

At the very least, one of these: http://www.justcarbatteries.co.uk/i...o-hybrid-agm/exide-ek800-110-agm-battery.html

..will be a direct replacement and has superior design as it's an AGM (absorbed glass mat) battery. Compared to the original:

http://www.justcarbatteries.co.uk/i...o-hybrid-ecm/exide-el800-019-ecm-battery.html

You gain 80CCA, and the battery will be able to discharge to a deeper level without causing problems.

I actually want to see if there's 38mm of width available in the battery tray, as the 019 size battery in AGM is a little bit bigger, that is a 90Ah battery, with 900CCA.

 

[jrkitching]

I'm sure drop in replacement, better chemistry, batteries will appear.

I'd like to think so, but I'm thinking it will be technically challenging to provide the necessary deep discharge protection without somehow interfacing with the mechanical switchgear in the car. I don't see how you can incorporate isolation protection into the battery which will be capable of handling the cold cranking current.

Providing overcharge protection is theoretically much simpler.

 

[UFI]

I'd like to think so, but I'm thinking it will be technically challenging to provide the necessary deep discharge protection without somehow interfacing with the mechanical switchgear in the car. I don't see how you can incorporate isolation protection into the battery which will be capable of handling the cold cranking current.

Most modern cars will no longer let you leave accessories on with the ignition switched off, the whole 'lights left on' scenario should be eliminated pretty soon. If the voltage drops below 2.7v/cell (or as the case may be) with no accessories on, changes are it's reached the end of it's life anyway. Lead acid don't have any special deep discharge measures either. It's claimed Lithium batteries can sit for a year without 'loosing charge' (although it's not clear what is meant by this as obviously some charge will be dissipated) so leaving the vehicle standing for long periods should be OK too as you're only dealing with the minimal drain from clocks, alarms etc and not adding self discharge to that too. At any rate, with a 2yr money back money back guarantee on the SSB Lithiums, it can't hurt to try. The higher nominal standing voltage of these batteries means you can go to a lower CCA and still have the engine start faster. I find it a little embarrassing when I'm the first car in a queue and have to wait that 3 seconds for the engine to spool up when the light changes, you can't always anticipate it.