Hello,

I am looking for lightweight battery recommendations. My car will only be used for autocross and the most "daily" driving it will see is the ride to and from the events which is a combined 60 miles to and from the location. Otherwise, it will sit in the garage with a battery tender.

Please let me know. thanks in advance.

 

I'm no expert on the subject by any means, but I recently purchased a 5.5lb lithium ion battery for my car. The retailer seriously cautioned me against installing it before installing a kill switch. Reason being lithium ion batteries will not recover if the power drops below 8v. Because I only drive it once a month or so, simply leaving the keys in the ignition could be a costly mistake.
By the same token, these batteries should not be overcharged either, and the manufacturer listed very specific chargers that were tested and accepted not to overcharge the battery. There were no Battery Tender products on that list.
I'm not trying to talk you out of lithium ion - just saying if you are considering that route, you need to thoroughly research it first.

 

I am using a Deka, they are light and super cheap. I figured if it failed then for what I paid it wasn't a big deal, I can buy 5 for the price of a Shorai. I am going on 2yrs now and it works great! I only drove 2k miles last year and toss it on a tender over the winter. I will just buy another if it fails

 

I just bought an Odyssey PC680, had one in my turbo Miata and it was great. I usually keep it on a tender during the cold months when the car doesn't get driven much. It's only been a week with the S but all good so far. Plus they are only about $120 on Amazon with terminals.

 

Which Deka did you go with?

 

how did you mount it? Do you have pictures?

Which deka? Xt14? How did you mount it?

 

Sounds like the retailer isn't an expert on the subject either.

I, on the other hand, happen to know a thing or two about Li-Ion batteries... A battery of Li-Ion cells absolutely will have a logic board monitoring cell voltages. It will have undervoltage protection which I've seen set as low as 2.5V for a 3.7V nominal cell. 3 such cells in series create the 12V we need. Obviously additional cells are used in parallel to gain amperage. So yeah, undervoltage protection threshold could be in the 7V to 8V range but that doesn't mean the cells themselves are unrecoverable.

This logic board also controls the charging circuit. You will not be able to overcharge the cells. You may overheat the thermal fuse and trip it though if you happen to use a lead-acid battery charger that isn't smart enough to go into 'trickle' mode after some time of charging. This is because once the cells are done drawing current, all the excess gets converted into heat as the voltage regulator for the logic board saturates. The cells themselves however, will be fine.

Remember that when you connect a traditional car battery charger to an off-the-shelf Lithium-Ion battery you are not directly charging the cells. You are only providing power to the logic board that has at least 3 individual charging circuits which in turn will charge the array of cells.

 

For the automotive li-ion batteries we talk about here I don't think it's to common with a BMS or logic board as you called it.
A recent example that came to my mind Shorai battery melted! - S2KI Honda S2000 Forums

 

yes x14. I just used a smaller tray and a cheap anodized eBay tie down and it has been perfect!

 

I'm at about 3.5 years on my Shorai Li-ion battery. It has been on a charger when not in use; about half that time is a traditional charger and the other half on a li-ion aware charger. I had to resuscitate it once after an alignment but otherwise it has lead a healthy life. At this point it is slowing down, though. It is a bit slow to crank in the 50s; kept overnight in the upper 30s it has a single crank before it has no more (thankfully my car fired right up).

Prior to the Shorai I had a PC680. It probably lasted 6-7 years but it is 2-3x heavier