Li Ion batteries

[Roger Ford]

Yes, that's something I've often wondered as well (why a LiIon can't cope with a standard charger, but doesn't mind getting a full 14+ volts from an alternator). There seem to be a couple of possible explanations that I can think of:

1. A standard charger might decide that in order to get the battery up to (say) 13.5 volts, it should put 16v across the battery, which would be too high for LiIon.
    
2. An alternator puts out rectified AC current. So although it might be supplying (say) 14.3v or so, it's not a constant 14.3, it actually varies between 0 and 14.3, and the battery can handle this much better than a pure DC 14.3v.

I'm not totally convinced by either of these explanations, and would love someone who actually understands the issues to explain them.

[David_Long]

Alternators are in fact the perfect charging device for lithium ion type battery - they are constant voltage device i.e. they will never go above 14.4 volts. Further more, they are capable of large charging currents that are required by some lithium ion batteries in a low state of charge - they don't like trickle charging from a low states of charge.  

[700newtons]

Well I have gone for it and fitted at Varley Li5 lithium battery (1.1kg). I bought it along with a dedicated cage from Demon Tweaks (using the club 10% discount).

 

I started the car for the first time this evening and it managed to do its job ok - although I think the cold and it’s partial initial state of charge means I didn't get the full beans.

 

My understanding is that the car alternator is fixed at a steady low voltage this is fine for Lithium. Chargers for lead acid have some parts of their cycles which are serve a useful function in maintaining that type of battery. However, they temporarily exceed the voltage that is acceptable for Lithium batteries. The Halfords charger that I have bought skips these cycles when used for charging Lithium cells.

 

I'll report if there any problems further down the line. 

 

Another thing…

 

Jump starting a lithium battery looks like it needs to do done with care. It has a low internal resistance and if connected to a spinning alternator a rather large current could pour into it causing damage. One website I looked at suggested connecting the dead battery to a donor lead acid battery with the engine off. The negative lead is then pulsed on the negative terminal of the dead lithium battery to nurse it back to life for a minute or two before making a connection.
 

*** I’m not suggesting that this is correct *** However, I’d be interested about the thoughts of others.

[Jonathan Kay]

Thanks, Simon.

Varley Li5
Mass: 1.1 kg (Demon Tweeks have the wrong value)
Quoted cranking current: 335A
Price: £186 inc VAT before Club discount

Jonathan

[7 wonders of the world]

The above is to get the dead LI-on battery voltage up to a point where the charger will recognise the battery - ISTR that below 2.5v the charger thinks its dead and wont even try to charge.

 

[aerobod - near CYYC]

With the Noco Genius 10 charger I have, there is a Force Mode that can be selected before then selecting the Li-Ion battery mode, so it will charge a battery that is initially registering 0V.

[2cv7]

Basically use a Lithium battery if you want to save a bit of weight.

If you want the best battery for a car then use a lead acid.

[Benton]

My rambling thoughts 
What doesn't make sense to me concerning using Lithium batteries in cars is that in many cases there is no mention of using any form of Battery Management System (BMS) alongside them.

Having spent years dealing with Lithium batteries for RC modelling its always been stressed the specific requirements of Lithium, not overcharging, not overdischarging, charging at specific rates, maintaining  voltage balance across individual cells, using only dedicated charges, storing ar specific voltages etc.  Lithium battery chemistry is obviously far different from lead acid, individual cell voltages, internal resistance, the characteristics of charging/discharging seemingly to be completely different.

My Lotus Exige came with a factory fitted LiFeP04 battery but  the battery is "protected" by a separate dedicated BMS.

Whilst you can buy a Lithium battery without a BMS, hook it up to your car and it works, charging it using your standard alternator/voltage regulator system  (that has invariably been designed for lead acid use), you certainly can't be treating the battery in an optimum way IMHO

And yes, (not as though I'm suggesting it can happen with car batteries unless really provoked) I have experienced a few Lithium Battery fires during my RC time, so am probably over cautious. 

 

 

[Roger Ford]

Good lithium batteries have a built-in battery management system. I certainly wouldn't buy one without. I don't know how comprehensive they are, I doubt that they include cell balancing, for example. I suspect they just prevent over-discharge and possibly overcharging as well. Once you have a cut-off at a low voltage (essential to prevent full drain and (a) destruction of the battery and (b) a fire on attempting to recharge from flat), it presumably isn't too hard to disconnect the battery completely if it's at maximum charge and still has an external voltage.

[Jonathan Kay]

From another thread.

"...  I know there's huge pros and cons, but just 1 Q? - 300 CCA is that about good enough?"

Several specs accumulated upthread. 

Jonathan

PS: Any more experiences out there?

[Mechanical Moz]

After sitting idle in an unheated detached garage for 5 months I checked the voltage on my Amazon bargain Skyrich lithium battery and it was 13.4V.  Unfortunately I hadn't taken a reading back when it was parked up to compare.  Car (1.8K) started on the first turn of the key.  Car has an isolator switch but other than that I gave it zero attention over winter, happy with that result. 

[700newtons]

I thought i'd report back about my progress with the Varley Li5 (from post 53).

So far so good - it has not let me down yet, and this includes a weekend sprinting in Angelsey and touring on Wightblat. Cranking in the current warm weather is strong. However, it was noticeably weaker on cold mornings in the early spring (but still did the job ok).

My car has an isolator switch which I use whenever I leave the car.

Simon

[David aka Blue7]

I have just fitted a JWM PS-12 LiFePO4 BATTERY to replace my Banner.

https://jackwebbmotorsport.co.uk/JWM-PS-12-LiFePO4-BATTERY-BUNDLE-p250876921?fbclid=IwAR3voQFKn1yrXGnxW528ShCjXMzbrzy5UlmSB-Bb0UgUTi4o0iBs_pefKps

Speaking to Jack he advises against trickle charger during winter lay up and just disconnecting the negative lead or if you have a cut off switch fitted turn power off (I don't have a cut off switch).  So far so good, it seems to turn the engine over faster but my Banner is now about 3 years old.

Fitting was straight forward apart from removal of the battery tray when to my astonishment it was held in place by 13 rivets in random positions.  I thought that maybe the guy that fitted the tray had just decided to use up all the rivets that remained in the box.  They took a bit of time to remove and I have covered the area with a sheet of carbon and fitted rivnuts to secure the new battery tray.  The battery leads are on the opposite side to the Banner but they still fit easily.

David

[BenF]

Hi David, do you know what the weight saving was compared to a Banner?

Regards Ben

[Jonathan Kay]

JWM PS-12: 1.5 kg
Banner 53034: 8 kg

Jonathan

[timb2117]

Cant comment on longevity but I have just done same as Blue7- even freshening up with carbon and alloy battery tray too! - Great minds think alike. 

Kicks like a mule is tiny and light and will I'll smile again in a year or so if it outlasts my AGM acid battery let down.

[BenF]

Thanks Jonathan, that's a huge weight saving!

[Jonathan Kay]

Yes.

I once did some tabulating of cost/ avoided mass...

But perhaps the better comparison would be with an AGM battery... I don't think that those Banners are suitable for Sevens in any way.

Jonathan

[StevehS3]

I used to think the same Jonathan but I have a Banner in my current 7 and the last and they have been faultless. There is little difference in weight between a PC680 AGM battery and a Banner (7.5kg vs 8kg?). 

[7 wonders of the world]

If your car has an immobiliser you need a suitable conditioner for a Li-on battery, mine gets about 2 hours every other day on a timer socket

[Bizzielizzie13]

I fitted a JWM battery 'Kit' to my R300 Duratec in the middle of last year.

All went OK, although as already said the terminals are opposite to the Banner so I had made a new earth lead & fitted an FIA Type isolator. The battery voltage dropped from 13.5 in October (when I took it off the road) down to 13.4 in the early part of April, it has not yet been on charge!

[David aka Blue7]

#71 Bizzielizzie13 did you fit the isolator switch yourself and if so how easy / difficult is it?  I don't have one fitted so I would have to just disconnect the negative lead during winter layup but this would be better / cheaper than connecting a trickle charger.

David

[Jonathan Kay]

Connecting a conditioning charger is a lot less hassle if you fit a socket in the cockpit. And the charger on the ceiling or similar.

Jonathan

[Jonathan Kay]

I don't know about lithium batteries, but for some other types the voltage without load is not a sensitive test of either the charge or the condition of the battery.

Jonathan

[StevehS3]

I pulled this from the internet but it was what I was expecting to see. Lithium batteries have a far superior discharge curve (making more of its stored charge usable) but this makes it difficult to predict the remaining charge by measuring its voltage.