LFP Start Battery??? Are we there yet?

A recent Will Prowse battery review made an oblique mention to Noco start batteries - he was unfamiliar with them which surprised him. Last year, I installed a Antigravity LFP battery for my Tohatsu 20hp and it's worked fine.

Prowse mentions LFP does not suffer the same heat degradation that FLA/AGM do. Since I recently replaced fairly new G31 AGMs that were toast presumably due to heat of engine room in a hot climate, really got me thinking. Also, voltage sag is much less with LFP.

Is it time to consider LFP for start batteries, at least for smaller engines such as a generator or my 75hp Perkins?

This Noco advertises this 700A start battery for $200 which is less than I paid to replace the battery in Weebles in Mexico. Granted capacity is low at 8Ah, but my Perkins starts in half a crank. If needed, I could use my house bank of 700Ah LFP for extended cranking.


Thoughts? Light, small, heat tolerant, high cranking, and now cheap. What's the catch? Wish Weebles weren't so far away - is give it a try and see how it goes. $200 is worth a science project.

Peter.

Two in parallel might be a better choice.

mvweebles said:

A recent Will Prowse battery review made an oblique mention to Noco start batteries - he was unfamiliar with them which surprised him. Last year, I installed a Antigravity LFP battery for my Tohatsu 20hp and it's worked fine.

Prowse mentions LFP does not suffer the same heat degradation that FLA/AGM do. Since I recently replaced fairly new G31 AGMs that were toast presumably due to heat of engine room in a hot climate, really got me thinking. Also, voltage sag is much less with LFP.

Is it time to consider LFP for start batteries, at least for smaller engines such as a generator or my 75hp Perkins?

This Noco advertises this 700A start battery for $200 which is less than I paid to replace the battery in Weebles in Mexico. Granted capacity is low at 8Ah, but my Perkins starts in half a crank. If needed, I could use my house bank of 700Ah LFP for extended cranking.

NOCO - 700A Lithium Powersport Battery - NLP30

The NLP30 is a lithium powersport battery that delivers 700-amps of starting power for motorcycles, ATVs, UTVs, PWCs, and more.

no.co

Thoughts? Light, small, heat tolerant, high cranking, and now cheap. What's the catch? Wish Weebles weren't so far away - is give it a try and see how it goes. $200 is worth a science project.

Peter.

Click to expand...

I'm confused by the heat-tolerant comment. My understanding of LFP is that it is LESS heat tolerant than lead, not more so. I just skipped through the video and missed that comment. I'll need to rewatch it, but I find his speech rhythm and intonation really grating to listen to so I generally don't watch the videos.

Bmarler said:

Two in parallel might be a better choice.

Click to expand...

Certainly redundancy has its advantages, but are two needed, or just desired? A starting battery's only job is to deliver enough instantaneous power to fully energize the starter. High-draw/short-duration means it doesn't need a deep capacity, just ability to deliver the required CCA (Cold Cranking Amps - the legacy terminology). Also need to factor in voltage sag which is substantial and can seriously erode ability of a battery to deliver rated CCA.

Not only is Weebles a couple thousand miles away from me, but I don't have an ammeter to measure inrush current. So I wonder what the CCA is really needed. She starts easily with a single G27 battery rated around 900A but I just don't know for sure. Since she routinely starts within a half-crank or so - maybe a 1-second of cranking, I doubt she consumes more than 1Ah, maybe 2Ah of battery capacity. A LFP can be discharged to zero, so 8Ah capacity theoretically is plenty. Voltage sag is much lower; affect of heat also low; longevity much higher. So is over-capacity really needed?

Related question - why did/do larger old-school diesels have dual 8D start batteries? Do they really pull 2000CCA? Or did it take that to mitigate voltage sag?

Peter

twistedtree said:

I'm confused by the heat-tolerant comment. My understanding of LFP is that it is LESS heat tolerant than lead, not more so. I just skipped through the video and missed that comment. I'll need to rewatch it, but I find his speech rhythm and intonation really grating to listen to so I generally don't watch the videos.

Click to expand...

I may have mis-stated, but pretty sure that's what he said. If that's not true, than it knocks out a major reason for me to even consider. I don't have a good place to move my start battery except up into a galley cabinet which ain't happening. EDIT - I did a quick Google Search and could not find credible information on working temp range of FLA vs LFP (info came from biased LFP interests - generally stated FLA <50C (122F) and LFP <65C (150F)).

I grew up an Italian Cahtolic kid in Utah which I loved - skied, rode horses, backpacked, all sorts of stuff that wouldn't have happened had I been raised in New Jersey like my cousins. Prowse sounds like many of the kids I went to high school with. I think he lives in Arizona but if pressed, I'd guess he grew up in an area with Mormon influence. Mitt Romney has an adult version of a similar accent.

Peter

mvweebles said:

Related question - why did/do larger old-school diesels have dual 8D start batteries? Do they really pull 2000CCA? Or did it take that to mitigate voltage sag?

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They were likely sized for worst-case, not best case. It may normally start in under a second of cranking, but what about the day you end up fighting with air in the fuel system after a filter change where something didn't bleed right? Or when you get a cold snap and it cranks longer before it fires? Some of the big, old school diesels did take a lot of power to crank, but in cold weather also might need to crank for a while before they actually fire.

Personally I'd want enough power to handle a good 30 seconds of cranking (with a break to let the starter cool somewhere in there). And even then there should be a second source of starting power available (generator start battery, house bank, etc.) in case you need more cranking time or the start battery has a failure.

mvweebles said:

Certainly redundancy has its advantages, but are two needed, or just desired? A starting battery's only job is to deliver enough instantaneous power to fully energize the starter. High-draw/short-duration means it doesn't need a deep capacity, just ability to deliver the required CCA (Cold Cranking Amps - the legacy terminology). Also need to factor in voltage sag which is substantial and can seriously erode ability of a battery to deliver rated CCA.

Not only is Weebles a couple thousand miles away from me, but I don't have an ammeter to measure inrush current. So I wonder what the CCA is really needed. She starts easily with a single G27 battery rated around 900A but I just don't know for sure. Since she routinely starts within a half-crank or so - maybe a 1-second of cranking, I doubt she consumes more than 1Ah, maybe 2Ah of battery capacity. A LFP can be discharged to zero, so 8Ah capacity theoretically is plenty. Voltage sag is much lower; affect of heat also low; longevity much higher. So is over-capacity really needed?

Related question - why did/do larger old-school diesels have dual 8D start batteries? Do they really pull 2000CCA? Or did it take that to mitigate voltage sag?

Peter

Click to expand...

Can't speak for others, but I use 2 12v 8Ds to start because the starter is 24v. I also have no hesitation starting off the LFP house bank, but that's because the internal wiring of the battery and BMS will handle the current required. Methinks that wiring is the limiting factor on using LFP for starting, not the current.

On the heat issue, I simply installed a pancake fan directing a cool air source through 2" PVC to blow on top of the LFP Bank.

mvweebles said:

Related question - why did/do larger old-school diesels have dual 8D start batteries? Do they really pull 2000CCA? Or did it take that to mitigate voltage sag?

Click to expand...

I'm not well-versed on old, big diesels, but it wouldn't surprise me -- if the engines want ~1200-1400 CCA to start -- that getting there with some reserve often took a couple of 8Ds.

Our most recent PO at sometime in the past replaced two of the battery banks, one for a main engine (which wants 1400 CCA at 24V to start) and one for the 24V thruster bank (needs high current). He chose 2x 1150CCA flooded batteries and they kinda worked for a while, but starting wasn't optimal.

Another thought is that it's quite common for boats to have been built with mixed-purpose battery architecture, where a battery bank for a main engine also services house functions. In a case like that, maybe bank size (CCA and capacity) could have been skewed to better deal with house loads too.

-Chris

LFP start batteries would require me to rethink my alternator set up. That is assuming they are compatible with non start LFP.


For now I do not need to replace my start batteries so I will just watch the development of these LFP start batteries.

I was a bit worried about putting my LifePo4 battery in the engine room due to the heat. I didn't see my battery temp get over 81 degrees (reading off the battery bluetooth connection), 85 degree air temp and 76 degree water temp. No blowers in the engine room, just one naturally aspirated Ford Lehman.