Best lithium battery chemistry for a DPV?

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AJMcc

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Posted this question in another thread but thought I would ask the question on its own.
I am NOT interested in any pontification on the dangers, or to re ignite a simmering feud between DPV/battery manufacturers.
I am interested in comments and information from like minded divers, that have researched these options.


"Please excuse the ignorance,
I am just beginning the process of sourcing a lithium battery replacement for my UV26/18 scooters and really don't know much about the different types of lithium batteries at the moment. Can you comment on your reasoning for choosing one lithium type over another, what makes one chemistry preferable to another?
In general terms taking energy, safety and longevity into account, what would you believe to be the most suitable type for these DPV applications?

* I do not plan to build a battery, I am sourcing manufactured batteries (drop in).
** I do know about SS and the OEM battery they offer, I am not looking to buy one, hence my questions above."




Any positive comments from anyone would be greatly appreciated. ( I see enough "your gonna die !" posts to last me a while)
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Thanks,
 
copied from the other thread

SLA and LiFe have comparable power, that is determined by the voltage. The LiPo packs have a higher voltage and less voltage drop so they do in fact have more "power" because the motor is revving a bit faster, but LiFe and SLA are running around the same voltages so there is no power gain, just burn time due to increased density.

For the UV18 you really only have the LiFe option from Rodney and that is an expensive battery pack due to the size. He is not making packs for the 26 and likely won't be. There are some guys that are, and if you hop over to the Cave Diving Forum there tends to be a bit more DPV discussion there.

Also cost, LiPo is much more expensive per cell than LiFe so unless you need the power boost, or need the super long burn times, highly unlikely you need either in the ocean, then LiFe is the way to go, especially if you aren't using it at least 2x/month since LiPo's don't like to sit
 
Just a point of order from an electrical engineer's perspective - the power (rate of doing work) would be determined by the voltage each battery is able to maintain while under load. SLA batteries develop a higher internal impedance as they are used, and will deliver less power to the motor. LiFe batteries by virtue of their greater cycle life will have a lower internal impedance, and deliver more power to the motor over their lifespan.


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Thanks Aquavelvet. I was just about to post something similar. Pound for pound, SLA have less burn time than LiFE have less burn time than LiPO. So, you can jam more LiFE in an area that used to have SLA, but you can jam more LiPO in more area than both. LiPO cost more, burn longer and a bit hotter (which will kill some boards). LiFE have greater cycles. 2000 instead of 500.

I've done many LiFE conversions. I have a Minnus with a LiPO battery. I'll be fitting a UV18 with LiFE batteries soon.
 
my apologies for terminology, power as far as area under the curve is not what I was referring to, the power output of the scooter is determined by input voltage, so the 24V nominal of SLA's vs the 29V nominal of the Lithium chemistries means huge bump in speed and thrust from the motor, significant bump actually. There really needs to be a formal comparison done between the Viper LiFe and LiPo because the LiPo is faster and pulls harder than the LiFe contrary to what the spec sheets say.
 
If you put a 29v LiPO battery in a UV18, you'll need a new circuit board at the very least, and possibly a new motor. We've fried Salvo Mojo's by putting LiFE batteries in them, because they run at higher voltage longer than an SLA would run.
 
no you wouldn't, Rodney does it all the time with the UV40's and the Vipers. They're the same motor. The original motors pre 2007 couldn't handle it so they turned them back, but the current Submerge motors can handle it no problem.
 
Yeah, what do I know. LOL
Trust me....

Granted the new UV18 and 26's are built better, wound better, have better circuit boards, but people aren't buying new UV18's and 26's and then fitting them with LiPO. Rodney's boards are setup for the scooter/motor/battery that is installed in them. Rodney also ins't putting LiPo in any UV's. Why's he putting LiFE in them? Oh, that's right, because LiFE batteries are running at 24v not 29.

Like I said, trust me. This isn't guess work at this point. We've been doing this for a couple of years. We've frankensteined our way into many different configurations for fun and for burn time. Take an older UV18 or 26 and try to put LiPO in it and you're going to fry something. How do I know this? Because we've done it.

I'll call Rodney on Monday. While I'm certain that the LiPO Viper and LiFe Viper are using the same motor, I'd guess the board is limiting the voltage going to that motor. I can't tell the difference in speed at all between the two of them. At any rate, it really doesn't matter, as I'm certain we're comparing apples to oranges with the UV series that people are fitting with LiFE.
 
I believe you, I do, but Rodney told me a few weeks ago that all post 2007 motors are the same across the board and they can handle the higher voltage of lithium packs. The manuals state the lithium packs are full at 28.5V which is why the specs are the same for thrust and speed and why the UV40 gets a thrust and speed bump. If the UV40 was running at 24V there would be no bump in either, which means LiFe and LiPo are running at 26V nominal. Call Rodney and verify, but that's what he told me a few weeks ago when I was asking him about them. The manual does not differentiate between the two packs which leads me to believe the pack is 25.9V for LiPo and 25.6V for LiFe. Increase performance would be the lack of voltage drop under full load from SLA to the Lithium Chemistries but there is a noticeable difference between the LiFe and LiPo's from what i've seen in the water.

Post 2007 motors are worth holding out for.... The pre-2007 motors are throttled back to 24V to protect the motors but the new ones aren't
 
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