Has anyone converted a 12 volt AGM trunk battery in a hybrid to lithium iron phosphate? If so, does a DC to DC converter need to be added to avoid too high of a voltage difference between the hybrid drive battery and the 12 volt trunk battery? Would a lithium iron phosphate 12 bolt battery also need some type of current limiter to prevent it from taking too much current since it has a much lower internal resistance than a standard AGM lead acid battery?
Why do you want to do this?
There are lithium based starter batteries; is that what you want to use?
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I would not do this. The 12v battery is part of the car’s complex electronics. Why mess with that?
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I am going to give the same answer that you got on the Toyota Nation forum . Just check with your local dealer because this idea might void any warranty you might have plus cause some very expensive repairs if it does not work.
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Haven’t tried, but it seems like this could indeed bring on some problems. Even if the voltage is the same, the battery charging circuitry and algorithms are almost certainly different between the two chemistries. If you decide to try this anyway, some potential risks to consider
- Damage to car’s charging circuitry or power source
- Incomplete or overcharging
- Fires
There are LiFePO4 drop in replacements for 12V lead-acid (AGM is lead-acid BTW) batteries.
They contain a battery management system that protects against under/over charge and over current.
Good ones out perform lead-acid, but they are pricey.
Here’s an example, but I can’t vouch for its quality:
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I wouldn’t consider it for a hybrid.
What would be the purpose? We keep our vehicles a long long time. And we replace battery when needed. I’ve yet to replace a battery more than once during the period we’ve owned it. If wife doesn’t buy a new car this year, then I may have to get a new battery for her 07 Lexus. Current battery is getting old.
It looks it is the same size as those 12 Volt 18 AH/20 sealed lead acid batteries found in jump starters. Most of those go bad after 4 years due to over charging or neglect. Then they seem go bad no matter how they are taken care of in 6 to 10 years.
Lithium would be a good choice for this since it wouldn’t need maintenance charging.
How long do these last in the EV? Does the EV use the AGM or sealed lead acid type?
Not an EV, Hybrid, says right in the title. The starter battery is lead-acid, whether flooded or AGM, I’d guess AGM. They last as long as any starter battery does in the area the car lives…
The hybrid battery is a different battery altogether. Li-ion, I believe, warranted for 10 years or 150K miles.
The 20 Ahr battery shown in circuitsmith’s link is a motorcycle starter battery. Too small for a car.
That is similar in size to jump pack batteries. The lead-acid type lasts about as long as lead-acid batteries do when typically neglected. There are li-ion jump packs but they cost a bit more. I own one, and it is terrific.
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