Test/review of VBatty 32700 3.2V 7000mAh (Grey)

Okay, thanks Barkuti. :beer:

Hmmmā€¦ Iā€™m still not sure, saw some discouraging reviews there, but these big cells are not popular here, so iā€™ll probably have to try my luckā€¦

But if anyone else has a good suggestion for where to buy 4 of these, let us know.

And what is the value of a review written by someone who doesn't knows where his/her arse is? You know what this means, doesn't it?

The cells are good. Their consistency could be better, I know. But with LiFePO4 this is less important, at least with regards to battery pack assembly as I've already discovered the chemistry is self-balancing.

If you do care much about using them in series, buy twice or thrice the number of cells you need and, with the help of some battery capacity measuring device, sort/bin them low to high and make balanced packs. I recently bought this inexpensive EBD-M05 constant current capacity tester, discharges at up to 5A with 4-wire independent voltage monitoring and does discharge graphs. User HenrysCat has one, check:

It just occurred to me that 3S configuration of these cells can run perfectly on a 2S Li-Ion driver, because low voltage protection will kick in at 6 Volts. :slight_smile:

Since the consistency of those 32700 LiFePO4 cells is not the best at least one could drop a bit below 2 V. I see no reason for this to be a problem, though.

Mmm, just noticed I already pinpointed you to the EBD-M05 device.

Yeah, you did. :slight_smile:
Itā€™s on my wishlist. :wink:

The grey VBatty 32700 LiFePo4 cells i use in a solar powered outdoor light are 2 years old now, time for a new capacitytest.
Now i have a much better capacity tester (Hidance DL24/P).
Two years ago i built a 2S battery pack with these cells to replace the original 12V 4Ah lead-acid battery that was dead after only one year.
These cells + the protection board were about the same price as a new 12V 4Ah lead-acid battery, but these LiFePo4 cells have a higher capacity (at least 50% more real capacity).

I tested the 2S battery pack at 2A with a 5,0V cutoff voltage, and these are the results:

5985mAh or 37,2Wh (=18,6Wh/cell) after 2 years of ā€œoutdoor temperaturesā€ (cold in the winter, and 2 hot summers) is a very good result.
These cells will last many years, much longer than a lead-acid battery.

I will try to remember testing these cells every year, i hope they will last for many more years.
The next test will be at the end of 2021 :wink: .

Thanks for the update Hobbyfotograaf. Those are some impressive results.

I know itā€™s an older thread but itā€™s very usefulā€¦ Iā€™m quite interested in combining 4 of these in series for a project. Are these too big to fit into commercial hobby chargers that would be used for 18650s ? Iā€™d quite like to get a 4 cell holder if possible but will consider connecting them together permanently (solder?) and finding a suitable chargerā€¦

You wouldnā€™t want to use an 18650 charger for LFP cells since the voltage is different. There is another type of hobby charger with wire leads, that can often be configured for different voltages. But, you want to have some kind of cell balancing when charging. You really should know what you are doing before attempting something like a series battery pack (parallel is simpler). If you just want a 6 volt LFP pack, Bioenno is a popular brand among ham radio types. They arenā€™t the cheapest but they are well made. They have 6 volt packs in 3ah and 12ah and come with optional plug-in chargers:

The ones Iā€™ve seen people using were 12 volt, which is more popular.

Wire them in series with a 4S Lifepo4 BMS, preferably with active balancing function, and then charge it with a hobby charger or inexpensive dedicated 12V chargers.

Lifepo4 are quite robust and will go a long way even without ever balancing them in low drain applications.

Thanks for the replies, it is for ham radio use although Iā€™m sure it will have many usesā€¦

Iā€™ll do some reading on BMSs and balanced charging before going ahead. One concern is wiring the batteries together but Iā€™ll see what I can find out.

They do generally not fit into cradle chargers, but there are exceptions.
You can check my list here: https://lygte-info.dk/info/roundCellChargerIndex%20UK.html

A hobby charger can charge one cell or four in series with the correct wiring, but you will have to make your own connections/wiring.

If you are in doubt about what a hobby charger is, check here: https://lygte-info.dk/info/HobbyChargers%20UK.html

Despite not supported by specifications, if you are willing to file down the positive pole bulge to some extent I can recommend the very affordable Lii-100 charger to charge these cells. It can easily be opened (uses standard small Phillips screws) and modified. The fit ends up being tight, but works.

I know this from experience, used it to help with charging some of these big cells for testing purposes:

A Lii-202 should also work (filing down its positive pole bulges, too), however being dual slot its measured lack of width will result in the cells lying somewhat off-center with both slots filled, although I'm fairly sure it will also work.

Many thanks for the useful info, much appreciated

One year later, a new test of these cells in my outdoor solar light (the LiFePo4 cells are 3 years old now).
The cells lost 61mAh, that is about 1% in one year:

There is a bms in the battery pack, but there is no balancing, the difference between the cells was only 0,001V

As impressive as it looks now, iā€™d like to see those results again after several years or several hundred cycles,

These seem very much like the Liitokala Lii 70Aā€™s that I bought last yearā€¦ Iā€™ve been dying to make a 4S pack but donā€™t have a spot welderā€¦ Iā€™m sure Iā€™ll find a way

Scimmy, you can also solder the cells. I've used stainless steel flux and low temperature solder to do this sort of job and it works like a charm, and at last I cover the solder jobs and their surroundings with homemade rosin flux to protect from oxidation; this last step is not strictly necessary, but without it the acidic flux treatment will cause some oxidation on the surface of the cells (step recommended if you aim for a long lifespan battery pack with upkeep).

Or you can buy the cells with pre-welded nickel tabs, this way you can solder them with standard solder and soldering iron.

A hair off-topic but related, both Liitokala and Vbatty are just rewrapping cells they buy from a chinese OEM or original equipment manufacturer, pretty sure. The actual original manufacturer rating very likely is 6 Ah per cell, so you can get this if your cells are top bin; and while I do not discard the possibility of higher capacities and energy densities, the 7 Ah rating in these rewraps is definitively a lie.

In fact, even the very own top OEM manufacturers lie with their capacity ratings, even if only a tiny tiny bit, and it's a shame. I cannot agree with this. An ā€œeveryone liesā€ is no excuse or argument to keep on lieing. Manufacturers could both believe in being trustworthy, showing trustworthy product ratings, and successful at the same time. And offering a trustworthy product rating is as easy as ensuring that your rating is a guaranteed minimum that all cells or batteries match or meet.

Thatā€™s very useful info, thank you so much