Armortek

Hello Members,

I wanted to get some feedback on an issue I have been experiencing with the new motion packs. I am building a jagtiger for a friend and I am using Dakota 25Ah lithium batteries. Dakota is known for making really good batteries in the US. I am also using a battery power switch between the 2 batteries to disconnect the circuit and to be able to charge each battery individually. And I also use a Power Meter to monitor voltage/current/power. you can see the connection on one of the images for the meter link. I use this setup on multiple tanks without issue. With the new motion pack, I first connect the connection with the meter without connecting the armortek power module. So, the only thing that should come on is the the power meter, which it does. I then proceed to connect the power module without anything connected to it. Again, I get power to the power module voltage LED and my power meter. I then connect the 2 motor ESCs and to the power module and receiver. I also get power. Please NOTE that I power down prior to each step. After the initial power ON of the ESCs, the batteries get bricked. when I try to repower ON, nothing comes on. The battery voltage drops from fully charged 13.3V to 12.8 or 12.9V without load. I can no longer charge the batteries and I have tried every trick in the book. whenever there is a load on the batteries, the voltage drops to zero. This has happened on 2 different set of batteries and Dakota is sending me a third set. I have verified my setup is corrected by powering the circuit with an external DC power supply, and with 2 lead acid batteries without issue. My guess is that after the initial power ON of the ESCs, the large caps on the terminals discharge to the batteries and must brick the BMS. Has anyone had this issue or any insight onto what may be happening would be greatly appreciated.

also, when I powered down, I powered OFF the armortek power module first and then the power switch. for powering ON, the power switch first, then the armoetek power module.

Regards

this is the link to the battery.
https://dakotalithium.com/product/dakot ... 4-battery/

the link to battery power switch
https://www.amazon.com/gp/product/B07T2 ... =UTF8&th=1

Power Meter
https://www.amazon.com/gp/product/B07T8 ... UTF8&psc=1

Wael,
I'm not familiar with term "bricking" but I have heard some Lithium battery are not intended to run in Series, which I assume you're trying to do to get 24V? Perhaps they have a BMS (battery management system) internal to the battery which prevent Series connection?

For a huge model like the JT, I would replace the 12V with one 24V (22Ahr) and not worry about the series connection. I replaced my lead/acid AGM with a 24V Lithium in my Panther and it is very good power, and much less weight than Lead/Acid. But it was expensive. So far I am very happy with the single 24V battery.
Bob

Hi Robert,

Thanks for the comment. The manufacturer says you can put up to 4 of these in series. They do have a BMS and the previous batteries of the same MFG in my other tanks work great.

Regards
Wael

Well, if he has used batteries from the same supplier (who I've not heard of) then the batteries shouldn't be the issue. In my Kt
I'm using one essentially one 24v 30Ah LiFePo4 from which I removed the BMS units. I use telemetry and alarms to monitor
battery state and a powerful smart charger to maintain it.

On my JagdTiger when I get to it I'm going to build my own pack from 8 50Ah LiFePo4 cells.

I've thought about reinstalling a BMS but I'm not sure it's always good to rely on them. I do have 30Ah straight LiPo4 with BMS units in them
and I'm going to keep them there as I basically don't trust LiPo4 batteries...

I'm very curious to know where the failure in his system implementation turns up. I've used one of those 'power' meters but only temporarily
directly inline with the battery(ies) for initial testing to determine current draw. In the control unit I made for my King Tiger I have a volt/ammeter
that provides useful information when static testing:
meter

But I'm using the previous generation of 'red' units...

Jerry

"Bricking" usually refers to IT, where you upload new firmware which fails, leaving your device useless, and hence a brick.

As the system works with lead acid and a bench power supply, which tend to be more sensitive to current pulses than batteries, there must be something in the Dakota BMS which is being affected. It states they can handle 300A current for less than 5 seconds, so that shouldn't be a factor.

I don't think there's anything you can do but move on to another manufacturer.

Adrian.

Hi Adrian,

I happen to be an EE that writes a lot of FW. And these batteries are Bricked/useless/dead/etc. In my view, “bricking” doesn’t just happen when dealing with FW, can also be a circuit state without a path out, which I think is happening in these batteries BMS. The BMS still somewhat functions as it does NOT allow the battery to accept charge or discharge current. And the approx. 1volt drop is a little suspect. Again, thank you for your feedback

I wanted to add that Dakota is sending me 2 12V 46Ah batteries instead of the 25Ah ones. I am a little concerned that the same thing will happen to these ones too. Also, The 25Ah BMS is a new one and the batteries I have in my other tanks is 23Ah. So it’s not exactly the same battery.

I don't know this brand of batteries,
and I don't know your technical capabilities,
but if it is possible to open them, in some brands the cover is screwed on,
bypass the BMS and test if the batteries work,
if they work, replace the BMS with a higher power model .
HI
Marco

LFP (Lithium Ferrous Phosphate) cells are quite tolerant to abuse. Of course, there are limits, but it is quite unlikely that you have managed to destroy the cells themselves before even starting to use them. Moderate abuse generally leads to performance degradation, rather than immediate destruction. Hence, I would guess that the BMS has locked up somehow. Is there a reset for it, or what are you supposed to do when it has triggered? Disconnecting it seems to be a common way of resetting, but if it is integrated?

My first response (which I deleted not long after posting) was skepticism as I find it difficult to believe BMS units have much or any smarts in them but who knows I'm not an EE myself and I've never written any firmware modules although I did spend quite a few years as an application dev...

My first thought was to eliminate the BMS and wire in an appropriate jst plug so a smart charger can maintain the cells.

Looking out on the web there's all manner of hits on dead batteries/BMS issues and a few even refer to them as 'bricked'.
It seems to me though most of the 'fixes' are essentially snake oil as I didn't find one, in a quick search, that actually did any diagnostics
on the BMS itself. It's worse when a battery under no load conditions shows a full charge yet under a load collapses like a cheap suit.

So either eliminate the BMS and use a external smart charger or use your EE superpowers to diagnose the BMS.

Even when it comes to batteries, the KISS principle still reigns supreme...better to offload the management of a battery to something external that
is easier to see and work with. BMS units buried in a battery just isn't the best when we have other options.

Just MHO...

Jerry

Members,

Trust me, it’s taken every fiber of my being not to open them as I was instructed by the MFG who have been extremely helpful and responsive. They want me to ship 2 of them back and they will let me know what the issue is. I am 99.99% certain the cells are good. I will eventually open one if not both of the 2 remaining ones I have left. Just want to make sure I don’t do anything that may piss them off.

Regards
Wael

I am not in favor of BMS,
especially if they are integrated,
I think I have been using LIFE Po4 batteries on my PzIII and on the Stuart M5A1 and on other rotated models for at least 15 years,
initially I tried various BMS,
in the end I removed them all,
I use a battery charger with balanced charging,
a telemetry system on the remote control and I live happily,
I am the only one in my group who has never needed to be towed either due to flat batteries or BMS that interrupt the power supply too much conservative,
The Life batteries are very robust,
they accept excessive discharges and it is possible to recover them,
often after a long time that the Tank were turned off,
with the old silver electronics,
we found the batteries completely discharged,
with a little patience we have always recovered them,
now we all use real switches that disconnect the battery.
if I don't use the wagon for a long time at least every couple of months,
I give it a storage cycle with the battery charger.
Hello Marco