LiFePO4 Supplier

[Greg Clement]

Will be starting work on the Options pack on the Chieftain shortly.

Can anyone recommend a supplier for 24v LiFePO4 batteries?

Thanks

[Stephen White]

Some of us have been using this very successfully:

https://www.tracerpower.com/24v-20ah-battery-slab.html

For Chieftain, you might well need 20ah but with my Cent, I've never run below about 90% capacity or below 23.5v after several long runs. I can do a couple of days of TankFest without recharging with this battery module. There are cheaper options out there but you have to be careful about the specs, particularly max momentary current. See the Knowledge Base Topic on the subject.

[John Clarke]

I run the Centurion in the garden, total running time around 30 minutes probably and it's parked (not running) for the rest of the time. I take it easy not wanting to churn up the garden grass.(moss and broad leaf weeds)
No problems.
I recently brought two new 12 volt 22 amp AGM batteries (£70 Inc p+p)
for Centurion, allowing me to use the older (still ok) batteries for sizing in Cheiftain. They'll have to lay down longitudinally and they take up a lot of floor space.

Stephen is quite right, the 24volt LifePo4 batteries is the obvious choice for the model, smaller, lighter and more running time capacity.

The stumbling point is the price. Unless your vat registered, the batteries suggested will cost a little under £1000 including charger and p&p.
There's also this problem of peak current tripping (30amp + continuous on this particular item) rare, but could leave you with a reset problem. This of course could happen with any imbedded BMS battery.

Life expectancy of LifePo4 batteries doesn't concern me as these particular batteries cost 10x as much as AGM's.

At the end of the day you'll have to weigh up how you expect to run the model and how much wish to invest.

[Gerhard Michel]

Hi John,

sorry, but I don't think this comparision includes all aspects. To use an AGM battery for many charging cycles it must be discharged only to 50 % DoD. This will say that a 20 Ah AGM battery can only supply 10 Ahs (and you have to use a big and heavy 40 Ah battery to receive 20 Ahs). A LiFe battery can be discharged up to nearly 100 % DoD without shortening of life cycles having a suitable discharge control.

For each of my models I need 8 single Life cells, costing 35 € each, adding to about 300 € with connectors per model. Then I need ONE LiFe-charger servicing up to 8 cells (price depending on charging capacity) and a RC equipment with telemetry to control the discharging of the cells. This avoids a BMS with its disadvantages like high costsand risk of reset needs.

Having in mind that LiFe cells last 5 times longer than AGM cells you will see that equipping a fleet of models with LiFe cells will be less expensive than using AGMs.

[John Clarke]

Gerhardt,
Your absolutely right, your experience and knowledge of these types of batteries is renowned on the forum. I know from your posts your a very active operator with the models needing long discharge times.
I think what I was trying to say if like myself I take the model out maybe 10x a year or less and run the model for short runs. The investment in lifepo4 does not seem worth while.
Space and the weight is definitely the reason I'd buy the LifePo4 batteries and would purchase if had to. But I can work with AGMs size and weight. Sacrificing a little more weight and space in the model against the high cost of the premium LifePo4 batteries is ok for myself.
Looking at your posts you build your own battery power packs which will naturally spook some people, worries that may seem trivial to yourself but scares the bejesus out of a lot of us should something go wrong. Scary fire risk is all to apparent as the batteries cannot be removed easily from most models. True with all types of batteries, which is why a quality charging system is required.
Most modellers want to buy off the shelf from a reputable supplier, feeling secure they've made right choice and that's where the high cost comes in.
My fear of buying cheaper brought LifePo4 batteries could cause disappointment if I was hoping to see a substantial better product than the usual AGM batteries.
So I go back to the original statement, if you know what your usage of the model is going to be, buy the batteries that suit it.
(If that changes it's easier change up to LifePo4).

[Gerhard Michel]

Hi John,

well, I understand the fear from unknown, perhaps even dangerous technologies. But let me say that I use only well reputable manufacturers of LiFe cells, like CALB (China aircraft lithium batteries), Winston, Headway and so on. On the other hand the LiFePO4 Technology is far less dangerous than LiPo (lithium polymere) cells well known in the aircraft modeller scene. In Youtube you can see the movie of a well charged LiFe cell pierced by an iron nail. You can see smoke but no flames, and the cell is far away from explosion. I suppose that an AGM battery would react similar. However the same try with a LiPo cell would be dangerous to life!

Lithium technologies have conquerred our daily life, look at tool batteries, electric car batteries and so on. There is no modern battery shaver without a lithium battery! Okay, the handling is new and requires a certain attention, but it is not rocket science I mean.

One important aspect for us hobbyists are the expences. For only one model in the home fleet of vehicles a LiFe cell battery set is an expensive acquirement due to the balancing charger for 8 cells. A completed battery with build-in BMS may be a solution when space, weight and endurance are important aspects. In all other cases an AGM battery set will be the right choice I think.

[John Clarke]

Well put Gerhard.
Maybe the BMS is the stumbling point, many like me would love have a plug & play high capacity power supply fitted to the model.

Greg asked if the forum knew of a good supplier lifePo4 batteries, he got a good suggestion from Stephen.

Because it's a Chieftain, a heavy model like Jagd Tiger I'd liked to have a LifePo4 battery with a BMS of at least 40amp continuous ability off the shelf.

But so far haven't seen one. Cost and useage are factors, but if there's is one out there I wouldn't mind looking at it.

[AlastairCooke]

Hi John,
What about this....

PowerBrick+24V-50Ah-Pro2-1-400.png (178.93 KiB) Viewed 2659 times

available from Intellitec (www.intellitecmv.com) for £993.23 ex VAT?

Alastair

[Adrian Harris]

One of those works out at about the same weight as a pair of 22Ah SLA batteries, but it takes up twice the volume and, being one lump, you don't have many options on where to place it.

One of my concerns is that a lot of these batteries use a large number of smaller cells in parallel to give the voltage and series to give the current, as shown in the video on that page:

Untitled.jpg (37.49 KiB) Viewed 2609 times

It states that the BMS monitors the cells, but actually it will only monitor a block of cells, so you are still limited by the weakest cell in a block.

I've just dismantled a dud 12v LiFePO4 battery and there were 28 cells inside, roughly the size of a C alkaline battery, with strips of nickel spot-welded onto them to make up four blocks of seven. These four blocks were what the BMS monitored. This was a nominal 20Ah battery but under test only gave less than half that before collapsing. I did toy with the idea of dismantling it, testing all the cells and replacing any dud ones, but the price of complete batteries has fallen faster than the cells from which they are made, so it worked out cheaper to bin it and buy a new one.

Adrian.

[John Clarke]

Greg
I think you may struggle with a "large power" brick height on Chieftain with main gun elevation and possible interference, the hull is no where as deep as Centurion, especially if you put in a flat false floor like I have.
Alastair
I notice there's a power brick from intellite rated at 32 amp, still an eye watering price. Doesn't come with a charger either.
Adrian
Dud??? Thought these things were bullet proof with a BMS. Hope it was in warranty.
Oh well as with life, pays your money and takes your chance.
Looking forward to seeing the installation Greg and the choices made.

[John Clarke]

Just out of interest has anyone had any telemetry readings from a JT under different running conditions?
(A bit lighter than Chieftain? )

[Adrian Harris]

I did a whole load of testing with JT as it wasn't running right initially.

Once I got it going well, the max current drawn doing neutral turns on grass was around 80A. This was with no smokers or audio fitted, so you can probably add 10A to that if you're running with all the trimmings.

It was fitted with a brand new pair of 32Ah Yuasa SLA batteries.

I seem to recall that driving normally was 10A-20A, depending on the sharpness of the turns.

I've now set up my Taranis so that it in normal mode it can only do gentle turns. This will hopefully limit the current draw and make the driving experience a little less rally cross.

Adrian.

[Greg Clement]

Thanks to everyone who has responded to my request for help.

Has anyone had experience with this company? https://ecotreelithium.co.uk/product/12v-24ah/

I know you would have to wire batteries 2 in series and lose the weight and volume savings but it would have the other advantages associated with LiFePO4.

Not too expensive and peaks at 60Amps

[Jerry Carducci]

Just out of interest has anyone had any telemetry readings from a JT under different running conditions?
(A bit lighter than Chieftain? )

I was going to ask that. I have a LiPo sensor that can send back individual cell voltages which isn't very useful for my LiFePo4
bricks. I was curious which sensors you guys were using and which receiver/transmitters you're using them with. My FrySky ( OpenTx and ETHOS)
systems supports many different types mostly of no use to me..at least for most of my models.

Jerry

[Adrian Harris]

I use the FrSky FAS100 ADV for current consumption, battery voltage and Ah used (via a LUA script).

You can also use the FLVS ADV to monitor up to 8 cells in a LiFePO4 battery, if you have access to the BMS balance entry point.

Adrian.