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Lithium Battery install

Jim B

Active Member
I just put in a Group 20, small Lithium battery that is rated for 600cca. It only weighs about 3 pounds and fits perfectly under the seat. Anyone know what do I have to do to protect my alternator? I have looked on line and found mostly boat stuff.
 
Having a good alternator capable of better than average current would be helpful.

I did alot of research on this subject about a year ago when I thought about building my own lithium LiFePO4 battery. This type of Lithium battery is 3.2v per cell where some Lithium cells are 3.7v per cell which is too high when you put 4 of them together.
4 x 3.2 = 12.8v
4 x 3.7 = 14.8v

These batteries use a M6 screw so you can attach metal buss bars, creating a battery pack of 12.8v using 8 cells.
upload_2023-2-25_11-26-34.png

The problem with Lithium is the internal resistance is so low that the alternator charges at such a high rate that it over heats and burns up. The only way I possibly found to get around this was to put a resistor between the alternator and battery, thus limiting the amount of current.

This is not your normal resistor, it has a very small resistance and high power capability, 5 mOhms ±0.5% 100W. Just one resistor cost $55.

What is really needed is a regulator that has temperature feedback, so that it can limit the current as the alternator heats up.

https://www.digikey.ca/en/products/detail/ohmite/TGHGCR0050DE/8568982

upload_2023-2-25_11-17-37.png upload_2023-2-25_11-18-17.png

You might find this video interesting, especially starting at 4:32 in the video.

 
I'm late to the party, so humor me. That is a 5 milliohm resistor? Can't imagine that would do much limiting. 12volts/.005 ohms is 2400 amps! What is the internal resistance of the battery? Does it matter? The battery appears to have some internal circuitry to limit overcharging and other bad things.
 
Exactly.
New fangled stuff isn't always better.
Smaller gel or flooded batteries have worked for over a century.
Anything electronic will give problems and hard to find nowadays locally.
KISS is a good rule of thumb.
I'm late to the party, so humor me. That is a 5 milliohm resistor? Can't imagine that would do much limiting. 12volts/.005 ohms is 2400 amps! What is the internal resistance of the battery? Does it matter? The battery appears to have some internal circuitry to limit overcharging and other bad things.
 
@Jim B
That is a pretty strong alternator for a 10si and that certainly will not hurt things. If you do have a problem I suspect it would be when the battery is in a state of discharge. Then you are asking the alternator to charge the battery up from a much lower value than just a single starting of the engine. Jim, this is not a black and white situation so I can't tell you if you will have a problem or not. The resistor is something I've seen mentioned as a possible solution at an affordable price. The other solutions are several hundred dollars, are much more complicated and take up considerably more room that we don't have in a TBucket.

Looking at the battery you chose does seem to have a really nice battery management system (BMS), where in the video above shows that many don't have any BMS, just load balancing circuity.


I just put in a Group 20, small Lithium battery that is rated for 600cca.
BTW, your battery is not rated at 600 cca, it's rated at 600 peak amps. Nowhere on their website will you find CCA in the ratings for your battery.

CCA has a specific meaning.
Cold Cranking Amps (CCA) | How to Choose Your Battery
The rating refers to the number of amps a 12-volt battery can deliver at 0°F for 30 seconds while maintaining a voltage of at least 7.2 volts. The higher the CCA rating, the greater the starting power of the battery.

NOCO - 600A Lithium Powersport Battery - NLP20
upload_2023-3-12_15-8-36.png
 
I'm late to the party, so humor me. That is a 5 milliohm resistor? Can't imagine that would do much limiting. 12volts/.005 ohms is 2400 amps! What is the internal resistance of the battery? Does it matter? The battery appears to have some internal circuitry to limit overcharging and other bad things.

Hard to remember all the details from a year ago, but I imagine it was about the difference in the internal resistance between standard car battery resistance and the Lithium Ion battery. I do remember seeing videos of alternators getting so hot you could see the smoke coming out of them while trying to charge the Lithium battery. "Does it matter", I suppose the lower the resistance the higher the current .... or does the alternator limit it's self???

If you watch the video from post #2, many of these Lithium batteries advertised for automotive use do not have a BMS, just load balancing. The particular battery that JimB picked does seem to have a nice BMS, it will be interesting to see how it works out in the long run.

My understanding is you are not suppose to charge a Lithium battery below freezing or damage to the battery occurs, so I have to wonder how they are handling that aspect.
 

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