Jump to content


Photo
- - - - -

A practical question from confused of lithium land


  • Please log in to reply
10 replies to this topic

#1 mariner

mariner
  • Member

  • 1,976 posts
  • Joined: January 07

Posted 16 May 2021 - 14:33

I need to replace my old DMS red top 40 ( Varley ) battery. It has an advertised cold cranking (CCA ) of 500 amps and does start my big block engine OK, or did!

 

I am tempted to a Lithium battery as they are supposed  to be better and weigh a lot less.

 

However they are rated on a different system to lead acid batteries so I am confused and ,at £700 a time, do not wish to buy the wrong one.

 

The biggest Li one DMS/Varley do is only equal to a redtop30 which is rated at 450CCA.

 

Other Li suppliers talk about pulse rate discharge which is higher number.

 

DMS give two numbers for their li-16 battery,  

 

Short Circuit Peak Current 1470A Cranking Current* 670A

 

 but then say that is only equal to the redtop 30 with 450CCA

 

So, is there some magic conversion ratio which lets me define the Li measuremernt of peak/pulse current to traditional  CCA please?

 

Then I can look for the right Li battery !



Advertisement

#2 Greg Locock

Greg Locock
  • Member

  • 5,962 posts
  • Joined: March 03

Posted 16 May 2021 - 23:43

I don't know the answer other than talking to battery people, but to give you some more information get thee to ebay and buy a 400A DC clamp on ammeter, and measure the current your starter is taking.

 

CCA is is a useful measurement for PbH batteries, as it measured their biggest weakness, but the different chemistry of Lithiums means they won't be 1:1 equivalent.



#3 gruntguru

gruntguru
  • Member

  • 7,192 posts
  • Joined: January 09

Posted 17 May 2021 - 01:21

All I know is you can start most cars with a Lithium jump battery the size of your fist - so peak current is not their weakness.



#4 NRoshier

NRoshier
  • Member

  • 500 posts
  • Joined: September 06

Posted 25 May 2021 - 12:42

My only suggestion is: don't.

I changed to a Li battery for the hillclimb car - they are so much lighter, but they are unforgiving. Cranking performances was great, capacity not so much, but I made the mistake of leaving mine connected to the hillclimb car overnight - a constant drain took it too low and that was the end of the battery and $380. I replaced it with a 'Fullriver' AGM battery.



#5 Canuck

Canuck
  • Member

  • 2,209 posts
  • Joined: March 05

Posted 25 May 2021 - 16:20

Anti-Gravity batteries out of the US has a built-in circuit to protect itself from that sort of thing, specifically. And even has a "boost" feature that will allow you to (hopefully) start your vehicle despite the battery having been depleted to the point of cutting itself off.



#6 Magoo

Magoo
  • Member

  • 2,918 posts
  • Joined: October 10

Posted 25 May 2021 - 18:53

Anti-Gravity batteries out of the US has a built-in circuit to protect itself from that sort of thing, specifically. And even has a "boost" feature that will allow you to (hopefully) start your vehicle despite the battery having been depleted to the point of cutting itself off.

 

 

What he said. 



#7 Magoo

Magoo
  • Member

  • 2,918 posts
  • Joined: October 10

Posted 26 May 2021 - 00:10

These newer battery types will often have significantly less internal resistance than a traditional lead-acid battery and when a traditional automotive battery charger is connected, it won't begin charging. The workaround is to get a decent lead-acid battery and some jumper cables and wire them up in parallel with the battery you need to charge. Then it will charge just fine. 



#8 mariner

mariner
  • Member

  • 1,976 posts
  • Joined: January 07

Posted 31 May 2021 - 14:29

Thaaks fro alt eh advice.

 

In the  end I chickened out - it's  called a budget!

 

I got the Odessy lead acid one comparable to my old Red Top 40. A Li one would save 9kg but cost £850 more including the essential special charger.

 

£100 per kg is an expensive way of saving weight if you aren't in a competition class.

 

Also even the slight risk of it not working meant I could have wasted all £1050.



#9 Canuck

Canuck
  • Member

  • 2,209 posts
  • Joined: March 05

Posted 31 May 2021 - 16:42

£1050 converts to $1800 CAD. That seems...outrageous.

#10 desmo

desmo
  • Tech Forum Host

  • 22,602 posts
  • Joined: January 00

Posted 31 May 2021 - 21:05

Overpriced solution looking for a problem. 



#11 Greg Locock

Greg Locock
  • Member

  • 5,962 posts
  • Joined: March 03

Posted 31 May 2021 - 23:27

I have worked on a program where the budget was $5 per kg saved. Our manager asked why nobody was pursuing this. I pointed out (another career ending moment) that if $5 per kg was feasible we could build a weightless car for $9000 extra.