Lipo vs lifepo4

[newhaul]

Originally Posted by john61ct

Buying units made by one of the half-dozen manufacturers in the world recommended by people you trust.

Buying them from a known trustworthy vendor.

Paying the going market rate, maybe 5-10% variation can be explained, but beyond that if it is too good to be true. . .

Especially since below container quantities (or at least less than a pallet), shipping costs are such a high proportion of the total.

I had a few dozen small CALBs (under 100AH) shipped 1/2 way across the US and best rate was $240.

So coming from Asia, the seller is subsidising your freight, has to come from somewhere.

someone had to be the gennie pig for them so I guess I'm that guy for these ones

[john61ct]

And we genuinely appreciate it.

How can you tell the Pioneers?

They're the ones with all the arrows in their back!

[newhaul]

Well not as good as I hoped but not as bad as I feared.
Final tally on the counter was 68ah from full to a dead stop of 10.3 volts. So actually just about 12 or so ah below expected . ( figure the 10.3 to bms shutoff of 9.8 would be approx 20 ah. )
( reason for the low test stop voltage is that's .3 volts above the auto shutoff voltage off the refrigeration system I will most likely be installing. Now it will not be below 11.5 volts again in the foreseeable future. Now to save up for another one.

[newhaul]

Almost forgot the real math
248 USD delivered ÷ 68ah usable = 3.65 per ah delivered ( drop in)

[john61ct]

The LVD on load consumers is usually there to protect their electronics, set too low to protect the bank.

[newhaul]

Originally Posted by john61ct

The LVD on load consumers is usually there to protect their electronics, set too low to protect the bank.

I realize that but I needed to know how long I could maintain the refer system in the worst case scenario . Other than that system all other normal loads are about 10ah underway and 5ah or so anchored. ( all led lighting except the spreader lights )

[witzgall]

Roadtrek Sprinter conversions come with a LIFEpo4 system, second alternator and a Balmar MC-614 regulator, both dedicated to charging that LIFEPO4 bank. It is there as the house bank, and to power the AC at night. The engine will start automatically to recharge if needed. It really is a slick system.

Chris

Originally Posted by DeepFrz

Certainly I've only been researching Class B motor homes that are, usually, much better insulated than most boats. However, with solar and 400 Ah LFP battery bank and a generator/engine automatic start system one can have a very comfortable system even in very high ambient temps. Some Class B motor homes are now being sold with 800 Ah LFP installations. That system would not require an automatic start mechanism on the motor and wouldn't even need a generator in most cases.

One of the big caveats here is insulation. A well insulated aluminum boat, for instance, could get by with a quite small aircon unit. I mention aluminum because well built aluminum boats are very well insulated out of the box while very few plastic boats are.

[Maine Sail]

Originally Posted by newhaul

Almost forgot the real math
248 USD delivered ÷ 68ah usable = 3.65 per ah delivered ( drop in)

I am still perplexed as to how you took -68Ah's out of a stated 5.75 kg / 12.68 pound LFP battery that is using 18650 cylindrical cells?

I just weighed two of the best quality 18650 LFP cells made one a K2 Energy at 1.40 oz and one an A123 cell at 1.41 ounces. Each cell is rated at 1.1 Ah.

To deliver 68Ah each 3.2V cell would need to have 62 18650's and we need four cells of 62 each to make a 12V bank. We'd need 248 18650 cells to get 68Ah's of capacity @ 12V.

248 cells X 1.4oz = 347.2 oz / 16 = 21.7 pounds of bare cells

Your total pack weight, including all the components, is specified at just 12.68 pounds?

Something is not adding up correctly? Can you explain the math they used in more detail? Any way I run the numbers, for 18650 cylindrical LFP cells, does not get me to 68Ah's in a 12.68 pound package?

Also regularly taking LFP cells to lower than 2.9V per cell, is not good for them. Your cut off is a hail Mary/ejector seat level protection not something to use regularly, not even in capacity testing. Your usable Ah capacity is at a cut off of about 2.9VPC or 11.6V. Most owners who want decent life use 3.0VPC or 12V as 0% SOC. Every quality LFP cell I have ever tested can meet or exceed its rating by the time it hits 2.9V.

If you paid for a 100Ah LFP battery you should have had that capacity or more by the time the cells hit 2.9VPC.

[newhaul]

Originally Posted by Maine Sail

I am still perplexed as to how you took -68Ah's out of a stated 5.75 kg / 12.68 pound LFP battery that is using 18650 cylindrical cells?

I just weighed two of the best quality 18650 LFP cells made one a K2 Energy at 1.40 oz and one an A123 cell at 1.41 ounces. Each cell is rated at 1.1 Ah.

To deliver 68Ah each 3.2V cell would need to have 62 18650's and we need four cells of 62 each to make a 12V bank. We'd need 248 18650 cells to get 68Ah's of capacity @ 12V.

248 cells X 1.4oz = 347.2 oz / 16 = 21.7 pounds of bare cells

Your total pack weight, including all the components, is specified at just 12.68 pounds?

Something is not adding up correctly? Can you explain the math they used in more detail? Any way I run the numbers, for 18650 cylindrical LFP cells, does not get me to 68Ah's in a 12.68 pound package?

Also regularly taking LFP cells to lower than 2.9V per cell, is not good for them. Your cut off is a hail Mary/ejector seat level protection not something to use regularly, not even in capacity testing. Your usable Ah capacity is at a cut off of about 2.9VPC or 11.6V. Most owners who want decent life use 3.0VPC or 12V as 0% SOC. Every quality LFP cell I have ever tested can meet or exceed its rating by the time it hits 2.9V.

If you paid for a 100Ah LFP battery you should have had that capacity or more by the time the cells hit 2.9VPC.

the weight specs listed are way off the pack actually weighed out at 20.5 pounds +/- ( used salmon fishing scale)
next I don't intend on ever taking the bank even near 11.6v now that I have conducted the testing .
Also by the numbers I'm sure it is short a bit on cells but the price and capacity are within acceptable limits for my testing purposes. ( and learning curve before spending real money)

[Maine Sail]

Originally Posted by newhaul

the weight specs listed are way off the pack actually weighed out at 20.5 pounds +/- ( used salmon fishing scale)
next I don't intend on ever taking the bank even near 11.6v now that I have conducted the testing .
Also by the numbers I'm sure it is short a bit on cells but the price and capacity are within acceptable limits for my testing purposes. ( and learning curve before spending real money)

That makes a bit more sense... Amazing that some of these Alixxxx vendors can't even weigh their stuff properly even when you pestered them for specifics. This on top of selling you a 100Ah battery that delivers only 68% of that rating, supports the a buyer beware approach on Alixxxxx.....

[newhaul]

Originally Posted by Maine Sail

That makes a bit more sense... Amazing that some of these Alixxxx vendors can't even weigh their stuff properly even when you pestered them for specifics. This on top of selling you a 100Ah battery that delivers only 68% of that rating, supports the a buyer beware approach on Alixxxxx.....

I bet some of the mis weighting is intentional. To reduce the shipping costs.
Now I could challenge their numbers via PayPal but at the price I am satisfied ( for it being a test bed) just won't get another one of these units from them.

[john61ct]

Where did we get the info that these are 18650 cells internally?

And I don't see any verification yet of the vendor's claim that these are even LFP chemistry.

[newhaul]

Originally Posted by john61ct

Where did we get the info that these are 18650 cells internally?

And I don't see any verification yet of the vendor's claim that these are even LFP chemistry.

perhaps you should do what I did and actually talk with factory reps.

[newhaul]

Originally Posted by john61ct

Where did we get the info that these are 18650 cells internally?

And I don't see any verification yet of the vendor's claim that these are even LFP chemistry.

here is screeners of Alibaba page for the battery pack

[john61ct]

Originally Posted by newhaul

perhaps you should do what I did and actually talk with factory reps.

Obviously when I say verification of the maker's claims, that would mean independent of their employees representatives or vendors, who would have an incentive to support those claims.