A question for the Lithium battery guys

Re: A question for the Lithium battery guys

I would go for a LiFePO4 (Lithium Iron Phosphate) battery for this. These are much safer than LiMnO4 technology and should last longer. The downside of LIFePO4 over LiMnO4 batteries is that they are about 1/3 heavier and larger than LiMnO4 but still much lighter than Lead.

They will have much better cold weather performance and lower internal resistance than Lead based batteries. I would do a little research on the cold weather capabilities of LiFePO4 batteries.

All lithium battery technologies do not take very kindly to be overcharged or discharged so it is worthwhile checking that your vehicle charging system is suitable. I assume the truck electrics are 24 volt, if so make sure the charge voltage doesn't go above 28.8 volts, 28 volts would be preferable.

I would be tempted to put some sort of battery monitoring/management system on the battery to make sure it is not overcharged or discharged.

Another point is that as Lithium batteries have a very low internal resistance so they will charge very rapidly and are very hard on alternators and drive belts, you will need to check that your alternator can cope with this.

Another very important point is to make sure that there is no 12 volt power being drawn from just one of the batteries. This will unbalance the battery which is not good.

If you google "truck battery lifepo4", you will get lots of hits.

I am sure there are other things that I have missed, hopefully PNJunuction will add to the discussion as he is very knowledgeable on twelve volt batteries.

Simon

Re: A question for the Lithium battery guys

Skyko wrote: »

Yes. I agree here. I should measure the alternator output voltage at high rpm (well, high for diesel...2600) to see if it is within the range of four LiFePO4 cells. There may be a way to limit this and to limit the charging current so as not to strain the alternator.

Try doing this test when the battery is full and not taking much charge. It is more than likely that it will be OK, Japanese electrics are usually well and conservatively designed, and the truck is only eight years old, just something to be aware of. If you can find the make and model of the alternator and see if you can get the specs for it. If it has a thermal safety circuit inbuilt that would be good.

I need to measure the current needed to turn over the engine when it is cold. It is getting cooler and should dip to freezing soon. I really should get a clamp ammeter but I guess I could calculate the resistance of the existing wire between the battery and starter and then measure the voltage drop across that while cranking (I = V/R)

Yes that would give you an estimate, how are you going to get an estimate of the resistance? It might be easier if you can you find the manufacturer and model number of the starter motor, then you might be able to get the details on it. Another approach is to check out what the cold cranking current of the current batteries is and use this as a guide. I have no experience using LiFePO4 batteries as a vehicle starting battery but would think that the same guidelines apply as for EV use. I would think that the cold temperature operation is the thing you should be focusing on.

Simon

Re: A question for the Lithium battery guys

Skyko wrote: »

Going from two 55 pound batteries to one 58 pound is at least some weight saving.

You chose wisely! Awesome battery if treated right. Just make SURE that battery "sees" 14.7v" once in awhile.

Since your primary issue was one of weight, you scored, even though a lifepo4 bank of say CALB large prismatic cells would do nicely as they are about 1/2 to 1/3 the weight of lead.

For some additional fun, you may want to see this video, even though it is motorcycle sli specific and not auto - A123 Lifepo4 (inside Antigravity) vs Deka agm
https://www.youtube.com/watch?v=-nm7bl39uxk

Thanks Joel W! (one of my main battery gurus..)

Interestingly enough, the Deka is 12ah, whereas the 16-cell antigravity is only 9.5ah for "real" ah ratings, not the "PbEQ" rating. We'll leave PBeQ to the advrider forum.

What you see here is how lifepo4 maintains a higher voltage under load as compared to agm, and for much longer. The Deka agm is an excellent battery, and Joel does not trick us by using abused / neglected junk, although he does know how to abuse them when he wishes. He will often take batteries to destruction to document their performance under various conditions. See the chart about 9:44 into the video, and you can see the difference between the discharge slopes.

However, in your SLI application, the Deka is actually doing what it was designed to do very well, and an Odyssey, being even lower in internal resistance, will hold it's voltage much higher than the Deka under the same conditions. Not to mention that you will most likely not be starting your vehicle 17 times in a row!

Just don't EVER let a generic Schumacher Speed-Charger touch your Odyssey. There is only ONE of them on their approved charger list, and that was from long ago. While their own chargers seem to be built by Schumacher, the internal firmware may be different. That was demonstrated to me when testing my own large Odyssey (A Sears "platinum" - Odyssey rebadge) with a generic speedcharger, and one built specifically for Odyssey - a Sears "platinum" charger. Both were the large wedge-shaped chargers, but only the "platinum" behaved properly and did not go into an overvoltage as measured at the terminals with a Fluke. Just a warning.

Re: A question for the Lithium battery guys

The racing motorcycle and dragster crowd seems to be going to Lithium since they want the least weight possible and only have to start the engine for that run (is there some clause in dragster world that the vehicle has to self-start?). However, am quite happy with lead acid for automotive use. And am extremely happy with LFP for full time RV-ing.
Reed