Duracell AGM

[Cobb]

Thanks, Ill take a look at that. I imagine regardless of the size as long as the car is a daily driver I wont have to worry of it running down between starts.

I imagine a honda with its eld will get even better mpg than the other vehicles that have tied it so far. Of course after playing with lifepo4 batteries I want the balancer circuit too.

Originally Posted by redpoint5

This 350F kit on Ebay is $65 and would probably do well to replace a battery on a motorcycle that doesn't have a computer (carbureted most likely)..

[American Viking]

Originally Posted by Ryland

Most states have an outdated law that required a wet cell battery to run the lights in cars because at the time wet cell batteries were the only rechargeable batteries out there, because of this it might be 100 more years before we see lead acid batteries leave, this is why even EV's have a lead acid battery that is charged off the dc to dc converter.

The big manufacturers don't use Lead acid batteries in their EV's.
Nickel Metal hydride, Lithium Poly Ion and a few other chemical couples are used.

[Ryland]

Originally Posted by American Viking

The big manufacturers don't use Lead acid batteries in their EV's.
Nickel Metal hydride, Lithium Poly Ion and a few other chemical couples are used.

Look under the hood and on every single hybrid and pure electric car you will find a lead acid battery that runs the lights, that lead acid battery is kept charged via a DC to DC converter off of the main battery pack.

http://www.youtube.com/watch?v=DPUcUOd1r1w

Even the Tesla S has a lead acid battery hidden in the front.

http://www.youtube.com/watch?v=xM-Bcerzqzg

Nissan's 12v lead acid battery is under the hood.

[mechman600]

Originally Posted by redpoint5

The problem with LiFePo4 is that it becomes permanently damaged when charged in sub-freezing temperatures.

According to my research (with the possibility of a lithium powered car project this summer), this may not actually be the case. There are many threads on DIYelectriccar.com that say sub-zero charging does not wreck LiFePO4 batteries. Sure, they won't take much of a charge right away, but they quickly heat up and do just fine. It seems that when charging at C/10, temperature doesn't matter.
Real experience on cold temperature charging of lithium cells? - DIY Electric Car Forums

[Ryland]

There is a really easy way to find out if a brand of cells that you are thinking about are going to be damaged from cold.
Buy a single cell, stick it in the freezer then charge and discharge it, see how many amp hours it takes to do both, if you rune a single cell you might be out $100 or $200 instead of $5,000 to $10,000

[American Viking]

Originally Posted by Ryland

Look under the hood and on every single hybrid and pure electric car you will find a lead acid battery that runs the lights, that lead acid battery is kept charged via a DC to DC converter off of the main battery pack.

My mistake, I thought the discussion had turned to using lead acid batteries for an EV's power system. Your correct almost every vehicle manyfacturer uses a lead acid battery, for secondary systems power.
A secondary battery is required, so that if the main battery shorts out for any reason, the hazard lights, brake lights and such will continue to function.

But just because your Tesla or new Nissan comes from the factory with heavy lead acid battery doesn't mean you can't swap it out for better energy chemistry and lighter package technology.

Remember, the OEM's do not put the very best into their cars.
They put the cheapest materials that they can into their vehicles to maximize profit.
Does that mean that the main battery in a Nissan or Tesla is poorly designed? No,..
But, it means that they will pick the cheapest battery technology they can for the 12V secondary system.

Example:
my VW Jetta has a 72 month group 48/H6 battery
Ratings:
CGA - 570A
MCA - 650A
RC - 115Min
Ah - 70Ah
Weight ≈ 40 lbs.

I can connect 3 or 4 LiFePO4 batteries to get enough cranking amps AND enough Ah capacity. This battery pack will still be smaller in size and weight less than 10lbs.

[Ryland]

They use lead acid batteries because they are required by law to have a wet cell battery to power the lights, lithium batteries are dry cell batteries and there for do not qualify.
The lead battery has now become the unreliable part in running the lights, the traction battery "shorting out" is almost unheard of and if the traction battery shorts out having hazard lights that work is the least of your problems.

When I have more time I'll dig up the exact law and quote it to you if you want.

Originally Posted by American Viking

A secondary battery is required, so that if the main battery shorts out for any reason, the hazard lights, brake lights and such will continue to function.

But just because your Tesla or new Nissan comes from the factory with heavy lead acid battery doesn't mean you can't swap it out for better energy chemistry and lighter package technology.

Remember, the OEM's do not put the very best into their cars.
They put the cheapest materials that they can into their vehicles to maximize profit.
Does that mean that the main battery in a Nissan or Tesla is poorly designed? No,..
But, it means that they will pick the cheapest battery technology they can for the 12V secondary system.

[American Viking]

Originally Posted by Ryland

They use lead acid batteries because they are required by law to have a wet cell battery to power the lights, lithium batteries are dry cell batteries and there for do not qualify.
The lead battery has now become the unreliable part in running the lights, the traction battery "shorting out" is almost unheard of and if the traction battery shorts out having hazard lights that work is the least of your problems.

When I have more time I'll dig up the exact law and quote it to you if you want.

No need to dig up the law.
I already posted that my previous statement was wrong, because I thought we were discussing the primary battery pack, not the auxiliary pack.


But even with that being said, The car owner doesn't have to keep it.
Its only a 35ah battery, so it could easily be replaced with a lighter smaller footprint battery of LiPo or LiFePO4 technology. You could even replace it with a larger capacity LiFePO4 battery (or 2) so that you would reduce or avoid 12V dc battery charging issues.