WattFlyer RC Electric Flight Forums - Discuss radio control eflight - View Single Post - Replace 90A/hr Lead Acid starter battery ?
Old 01-02-2020, 03:55 PM
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Join Date: Jun 2013
Posts: 1,222

First as long as you use 4S LFP (LiFeP04), is completely compatible with Pb chargers and utilization equipment. LFP can be charged anywhere from 13.8 to 14.4 volts. One bit of advice Nigel is never ever fully charge any Lithium battery as that only shortens cycle life. Lithium does not require ever being fully charged like Pb. They work best in a Partial State of Charge. !3.8 to 14.2 is more than enough.

I build racing golf carts and use a lot of lithium batteries. Use to use a lot of Ch-Com LFP batteries like CALB or Synopoly not so much anymore because of they just do not last long and do not have the punch, or very high discharge rates of say a Nissan Leaf batteries most DIY EV builders like to use today. As for size it sounds like you have 180 AH today right with Pb? Equivalent size from Pb to LFP really depends on Discharge Rates and how deeply you need to discharge. Assuming just starting, lighting, and ignition you can easily get away with just 100 AH with 10C burst gives you 1000 MCA and sufficient capacity for some engine down time and running on battery. If on the other hand you turn off the motor and want to operate a day or two without the engine running, you will need to be at least 80% of the original Pb battery. So if you have 180 AH now will require 145 AH.

Since you are not in the USA or UK, finding quality LFP prismatic cells is going to be a challenge and you may have to buy Chi-Com POS LFP cells. Of the brands in China, CALB is the best junk they country sells (Chinese Aviation). In prismatic form factor you can get 40 to 200 AH cells. Just DO NOT USE any battery made from 18650 cells.. To get say a 100 AH battery in 18650 cells requires 200 cells to make a 4S25P battery. With Prismatic or coffee bag cells all it takes is 4 cells in series.

But Nigel remember this. A good Pb battery like those made by Rolls and Trojan are not only a lot less expensive, but will outlast any lithium. Rolls and Trojan offer models with 7 and 10 year warranties. Most you can get with Lithium is 1 year from China which you cannot file a claim for.

Good luck.

Your friend in the USA

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