Thoughts on LiFePO Batteries

[Scriz]

I recently received a free LiFePo 12v battery that is advertised for motorcycles and Jet Skis. Specs: 12V, 8Ah, 480A with a smart battery management system (meaning it can charge off of the host electrical system, no need for special charger). The battery weights less than two pounds and looks like it can do all the things I would need it to. I have read some literature on this battery composition and it seems like it could have some potential downsides if not maintained correctly, but they use it in aircraft and all kinds of rescue devices, so would you use it in your Sea Doo? It would probably be used in my 2008 Wake 215 if I was going to use it as buying another ECU for my 2004 would ruin my summer. The only thing that worries me is the safety manual says not to expose to seawater, but I think they mean dunking it. The risk of this is pretty low as we use out skis for touring, not extreme sports.

Thanks for your thoughts.

 

[skiasylum]

One plus feature of LiFePo batteries is their ability to accept higher charge (C) rates than lead acid batteries. So usually when an alternator or magneto charging system designed for lead acid is put in the picture even with a BMS, a DC/DC charger is used to limit that charge rate. Seadoos have a fragile electrical system and would be damaged by higher C rates. Now if the smart BMS you referred limits the C rate to around .2C you should be good, but essentially what you now have is a very expensive lightweight lead acid battery. My suggestion would be to use a high quality AGM and wait for the manufacturers to start using LiFe OEM.

 

[Scriz]

One plus feature of LiFePo batteries is their ability to accept higher charge (C) rates than lead acid batteries. So usually when an alternator or magneto charging system designed for lead acid is put in the picture even with a BMS, a DC/DC charger is used to limit that charge rate. Seadoos have a fragile electrical system and would be damaged by higher C rates. Now if the smart BMS you referred limits the C rate to around .2C you should be good, but essentially what you now have is a very expensive lightweight lead acid battery. My suggestion would be to use a high quality AGM and wait for the manufacturers to start using LiFe OEM.

I was afraid this was going to be the outcome. What I will probably do is take this along when I go out as a backup. It is light enough to carry and if I am stranded, I can either use to jump the regular battery or hook it up for a short period to get back to the dock. I may dig in and see if I can find a charge rate because this thing is crazy light and has all kinds of cranking power. Thank you for the insight.

 

[skiasylum]

Engine Charging Systems With Lithium Batteries | Fact Sheets

Good article, if you scroll down it talks about the Rotax charging system and Lithium batteries

 

[Scriz]

If I am reading it right, the Rotax 503 has many similarities to the 1503 in their electrical setup, which I think is the big takeaway. Lithium does not like the highs and lows of RPM induced charging even with the regulator and it will degrade the battery through too little input or too much input. I guess that explains why LiFePo is being used more widely in cars and trucks where alternators can provide a more constant voltage for charging. Either way, I guess I will have to find another primary use for this battery as it is too nice to not use on something.

 

[200mph]

In reading the referenced linked article, it seems to imply direct charging to the battery, but how relevant is this info when a battery management system sits between the charging device and the battery cells themselves? Many of these small batteries are geared towards lawn mower and other equipment with somewhat crude charging systems. I’m just asking/questioning as I’m interested in using this style battery also and trying to understand the risk.

Do remember a company selling lithium mosfet regulators. Perhaps they would help in reducing risk.

 

[skiasylum]

A small battery BMS is designed to protect the battery it is managing, not the vehicles electrical system/charging system the battery is storing power for. By protection I am referring to a system to help prevent the battery from catching fire and burning up the vehicle its storing power for so the manufacturer doesn't get sued. Also keep in mind all of these smaller Lithium cells and BMS's are all made in China and shipped to the US for sale or assembly. The automotive industry has started using Lithium batteries to store power in their 12v systems with sophisticated BMS systems designed by very smart people to protect both the battery and the electrical system. As far as risks go, if I had a 2022 Ducati Superlegga that needed a new battery I am going with a new OEM battery, whatever kind it is, if I had 2008 Toro electric start lawn mower I would try a properly sized lithium battery all day long. As far as a "smart" BMS that inhibits lithium battery charging to lead acid C rates for small equipment, I am not aware of that yet. I did try to check some specs on a couple of Amazon smaller lithiums and there was no mention of limiting C rates for charging.