LTO (Lithium Titanate Oxide) – The Ultimate Battery for Dash-Cam parking mode (DIY)

Funny that changes were made to the app that didn’t result in a change of version numbering. The version in the app store shows it was changed 1 month ago. Guess they have a protocol to govern what types of changes to the app trigger a version number change.

Specs that I captured from AliExpress page for the charger show fan turns on at 50-55c, so your temp was right at the threshold range for turning on the fan.

Right now, I’m running the camera in parking mode (just about 3w power draw) to see how long the battery lasts and how the Viofo regulator behaves as the battery runs down. Battery voltage depletion is non-linear. Started at 16.0v. After 12 hrs, voltage was 14.5v. After 24 hrs, voltage was 14.0v.

While I was playing around yesterday, I connected both red and yellow viofo input wires to only 4 cells, voltage was 9.15v. The camera turned on with normal drive mode. Then I removed the yellow ACC wire. The camera switched to parking mode, but never shut down. The Viofo voltage cutoff switch was set to 11.8v at the time. Given this, I’m curious to see what happens when the batteries run down. This will also give me an opportunity to see if the charger stays any cooler as a result of coupling it to the blue panel.
 
UPDATE: Do not use this schematic, the battery is not properly fused. See updated schematic three posts down.

Here is the schematic that I’m using for my 6S LTO battery pack.
IMG_4705.jpeg


The battery pack is still discharging after its first full charge: 42 hrs later and still have 45% battery left (only have about 3w draw for parking mode on single channel). I’m starting to think I shouldn’t be concerned about the BMS not shutting down by itself. The power draw seems so insignificant in comparison to the battery capacity.

I just started putting my second one together.
 
Last edited:
Second one! nice! 👍

Schematic looks good..., except the fuse placement, I think.
It is common practice to fuse the battery positive output before connecting anything to it.
Schematic shows the charger, power meter, and regulator all are directly connected to LTO positive without fuse protection.
On the other hand, based on use of XT60 for input, I assume you are going to use exclusively ACC power source, which is usually fused, hence the fuse for input is probably not necessary.
I would move that input fuse to the positive output of the LTO battery (or add another one) and then connect all components to the positive output after the fuse.
 
Last edited:
Ha, I was just about to ask about fusing the battery output to the regulator!

Yes, the use case is to power the battery pack from an ACC switched 12v utility outlet (which is already fused - so my input fuse is likely redundant, though doesn’t hurt anything). Would the better arrangement be to put the 15A fuse between the charger and battery pos terminal, then move the red input wire to the viofo regulator and the voltage meter to the pos output terminal on the charger?

This arrangement would fuse all battery connections with a single fuse.

I might also add a 1A fuse to the red input wire of the Viofo regulator. This would protect the long run to the camera in the event the wire got damaged/pinched somewhere along the way.

This first one will go into my son’s car. Second one is for my car. Total build cost looks like $255 each for 276Wh of power.
 
Here is the updated, properly fused, schematic. I added a 1A fuse for the meter (which consumes 1w) and the input side of the Viofo regulator (uses 6-7w to power two cameras and the GPS module).

As a side note, and this seems kind of out of place or ironic here, but I'm getting tired of waiting for this battery to run down😉. I'm coming up on 72 hrs and there is STILL more than 30% of battery charge left...

My son’s Mustang has 12v utility outlets that are always live. Bummer that they don’t shut down when the ignition is turned off. So, I tapped a fuse in the fusebox to have a power source that goes up and down with the ignition and used this to power a time delay relay and inserted the relay into the hot leg of the 12v utility outlet in the center console. Now it works like I want it to: it goes on and off with the ignition. This keeps my battery box more simple with just a single 12v ACC input and a single 5v output for the camera.

GPak, your work and this thread are really a winning implementation! Thank you!

Fused Schematic1.webp
 
Last edited:
It's interesting to see how accurately the app shows the remaining power. Usually the capacity drops faster at the end.
Have you checked if the discharge current in the app matches the actual current the DVR is drawing?
I think the displayed current in the app can be calibrated, but if you calibrate it for discharge (preferred), it will most likely be inaccurate for charging.

Also it is interesting to see a real battery efficiency.
With the DVR's low power draw and long run time, the BMS's small self consumption will impact the efficiency.
 
@EricSan: first of all, kudos for your work and sharing your build experience. 👍 Nice to see all the hard work @GPak has put in got a spin off.
My apologies if I missed it in a previous post, but how long does it take to fully charge the battery pack?

I ask as I initially wanted a battery pack that lasted as long as possible, after we'd had multiple times that our cars got damaged while parking the last couple of years. I hadn't realized enough that, for a battery pack with sufficient capacity to last multiple days, it will take some time to charge it. I've purchased two PowerCore LFP batteries, which provide 250Wh, but take 3 hours to get fully charged. I had hoped I could charge them while my car's main battery was charging, we own a Toyota PHEV, but that unfortunately doesn't provide 12V 5-10A while charging and my commute is measured in minutes, not in hours. Long story short, just curious 🙂.
 
After 75hrs, the BMS finally shut down the camera after reaching its shut down voltage. After another 11hrs, the BMS itself turned off. The BMS showed a discharge current of -0.1A while the camera was running, which looks low to me as this translates to only 1.2w to 1.5w (depending on voltage). The camera itself (1 channel, no GPS) consumes just shy of 3w (measured with external ammeter) and the power meter consumes just shy of 1w (also measured with external meter), plus the power draw of the BMS itself (have not measured this, but it keeps a steady 3c over ambient, so it's not insignificant), so total power draw is in the neighborhood of about 5-6w. I'm not sure that I'm interested in adjusting the accuracy of the power draw meter. But, now that I've run a full charge/discharge cycle, I'm hoping that the capacity meter in the BMS will have calibrated itself. If the app can report an accurate battery percent left, that would be useful.

@TheSpanishInq I am just now starting the first full charge cycle. I'm curious how long this will take as well, I'll keep track and see how it goes. Just thinking about your desire for parking mode and relatively short commutes (fits my situation as well), it seems that your solution might be in having multiple batteries that are easy to swap in and out with one another. That way, you could charge one in the house while the other is running down.

Here is a screencap of the BMS app after it had turned off the camera:
Dashcam Shutdown.webp
 
I’m rather impressed with 75 hrs! The meter was showing 12.17v at 10p last night and the camera turned off just over 2 hrs later. I’m guessing the battery hit 11.8v at that point and the Viofo regulator shut things down. The BMS shut itself down 11 hours later at around 10.8v. At this point, the camera won’t turn on.

Once voltage gets down to about 12v, it seems to fall off a pretty steep cliff. The first and last 25% of battery life seems to go by quickly. That middle 50% lasts a pretty long time.

I added an extra fuse between the charger and the battery and another fuse between battery and the camera. I will charge it tonight after dinner and see how long it takes to hit 100%. I will double check charging current at that point. I want to limit current out of the car utility port to no more than 10A. Current into the battery will be at a higher voltage, so correspondingly fewer amps for charging.
 
Some charging data:

I set the battery charge rate (from charger to battery) to 9.0A, as measured with a clamp meter. I adjusted the "Calibrating Current" in the Setting page to match. You can only enter a calibration current with integers, no decimal places. 9.0 amps battery charge rate drew about 9.65A of current out of my external PSU. I have a Meanwell switched mode power supply with variable output that I used to provide power. Its output voltage is adjusted to 13.47v to match the output of my car's alternator. This keeps the current draw from the 12v utility port in the car below 10A, which was my design goal. I used 15A fuses at the input of the battery box and between the charger board and the battery itself. Most car utility outlets are also fused at 15A. This provides a reasonable margin of safety for charging the battery.

With a 9.0A charge rate, the battery was fully charged in 2.5hrs. Not bad! The maximum charge rate for the JiKong BMS is indicated as 25A. At the maximum charge rate, you need to use pretty significant wires, think 6ga to 8ga wire. I was using a crappy "solar charge" wire that I purchased on EBay to connect the battery pack to my Meanwell power supply. The vendor from China advertised the cable as a 12g cable, but it's not. It is a 16ga wire (I measured it). They argued with me when I requested a refund, but they are wrong. 9.65A of current draw on a 16g wire heats the wire to over body temp. Still plenty safe (most wire insulation is rated to about 60c), but I tend to start getting wary when wire temps rise above body temp (when the wire insulator feels warm to the touch). for a 9-10A charge rate, you really need to use 14ga wire at a minimum. 12ga is a bit of overkill, as GPak pointed out earlier. With a 20-25A charge rate, the 6ga wire should go DIRECTLY to the car battery or DIRECTLY to the alternator. DO NOT attempt to draw this level of current from a fuse box OR ANYWHERE ELSE. This will cause electrical problems for your car that won't be easy to correct. Many newer cars have "smart" fuse boxes, where additional circuitry monitors the total current draw and shuts things down if the current draw gets higher than expected. If you charge directly from your battery/alternator at 20A draw, this battery should be fully recharged in about 1.1hr. Impressive!

At 9A charging current, the blue panel from the box that I mounted the charger circuit to was measuring about 32c (11c over ambient). I pushed charge current to 10A and the temp jumped to 37c (16c over ambient). The powder coated thin blue sheet metal doesn't do a very good job at spreading/dissipating heat at all, it's just too thin and flimsy. On the "charger end" of the blue panel, the temp was 32c and just a few inches away on the "BMS end" of the same panel, the temp was 24c. Not very uniform at all. I'm contemplating replacing the thin blue panel with a 1/8" aluminum panel (much better at spreading heat) that is painted black (better for radiating heat) and see what temps and temp uniformity from side to side are like then. If necessary, I could even mount a small heat sink on the outside of the aluminum panel to better radiate some heat. GPak indicated in car temps reached 53c earlier this week. Add an 11c temp rise and now were at ~65c, which is approaching the early cut-off temp of the BMS. If you attempt 20A charging, consider adding a heatsink directly to the back of the charger circuit (with thermal paste) and arranging a fan to draw air directly across the fins of the sink while the charger is activated. This will prevent overheating issues for high-current charging.

While the battery was charing, I was able to stop the battery from charging by using the "Charge" toggle switch in the "Control" panel of the app. Strangely, I had trouble getting the BMS to start charing the battery again by turning the "Charge" toggle switch back on again... I had to power cycle the BMS in order to get it to start charging again. I had similar issues with the "Discharge" toggle in the "Control" panel of the app. I was unable to turn off the output while the battery was charging (expected). Once battery charging had stopped, I could turn off the dashcam by toggling the "Discharge" setting in the "Control" panel on the app (also expected). But, like the "Charge" control, I was unable to restore power to the daschcam by toggling the "Discharge" setting back on again. I needed to completely power cycle the BMS to get the dashcam up and running again. This seems like a bug in the software to me...

As the battery neared 100% of charge, the BMS started acting up. It initially stopped charging the battery at 15.5v, despite being set 16.0v (2.65v * 6 cells). At this point, the orange warning light on the charger board lit up, indicating something wasn't happy. At this point, the BMS indicated a current draw of 8.9A, but the clamp meter was showing me a draw of 11.65A from my Meanwell PSU. Thus, efficiency of the charger took a hit and tripped an alarm. I'm not sure what to make of this yet. It would be nicer if both the BMS and the Charger board were accompanied by more robust documentation.

Anyhow, I still have some playing around to do, but it seems to be working reasonably well right now.
 
EricSan said:
With a 9.0A charge rate, the battery was fully charged in 2.5hrs
Click to expand...
Not bad, I somehow had hoped LTO would be a bit faster.
I agree with your reasoning regarding the charge rate, higher than 10A doesn't feel right. >20A is looking for trouble imo.

A shame the BMS started to act up. Does the app have a diagnostic option of some sort?
 
Battery charging is all about current flow and this is one of life's "there's no free lunch" situations. If you want the bucket to fill faster, you either use a smaller bucket (less battery capacity) or you fill it with a bigger hose (more current). There is no way around this, except to rotate batteries and always have one charging (use two buckets). Each battery chemistry has it's own limits of charge and discharge rates that are appropriate. I'm thinking that LTOs, since they are intended for electric vehicles, will feature the fastest charge and discharge rates right now. Faster charging (up to 20A) is something that I could implement as the main battery in my Volvo is in the trunk where my parking battery will live, so access is easy and close by, but my situation doesn't call for this need.

I fiddled with the charger again this morning and adjusted the output voltage up from 16.5v to 17v. This seems to have eliminated the orange warning light on the charger from coming on, though I need to play around and observe its behavior a little more. I'm thinking that 16.5v volts from the charger didn't provide enough voltage headroom for the BMS to charge the batteries when they were close to full capacity (starting around 15.5v). It seems that there is a "sweet spot" in terms of voltage output level (not too low, not too high) where the charger operates without tripping the alarm. I need to run the battery down a bit and see how it behaves as I charge it up.

From what little the web page where I bought it indicates (because it doesn't come with any paperwork at all), the orange light indicates a voltage/current starvation issue or a short circuit. It is called a "CC Indicator" (for constant current?) and the explanation says: "The light will be lit and automatically recovery will be enabled when the output current limit voltage drops, output is short-circuited, or with output over-temperature protection." Since it is not a short-circuit or over-temp situation, it's got something to do with voltage and current settings. I'm using a Meanwell LRS-200-12 switching power supply that has variable voltage output (set to 13.4v) and can provide up to 200w, which is about 14.5A at 13.5v. So, it seems plenty capable of providing enough current and avoiding a "current starvation" situation for the charger/BMS. Here's the charger I purchased: https://www.aliexpress.us/item/3256805949511895.html#nav-specification

Bumping up the voltage output for the charger predictably increased the current draw from the 12v utility outlet. 17v at 9A = 153w of total draw. Divide 153 by 13.4v results in a current draw from the car's electrical system of 11.4A. Most utility outlets are capable of delivering 15A (180w), I might end up backing the charge current down to 7A or 8A to have a little more headroom in the power supply. I have to see what the long term "steady state" battery usage is once I install it in the car.

After calibrating the charging current, the discharge current as shown in the app seems pretty realistic. I saw -0.2A draw at 15.91v, which works out to about 3.2w for the single camera by itself, which matches my earlier measurements.

Need to play around and measure its behavior some more.
 
Last edited:
TheSpanishInq said:
Not bad, I somehow had hoped LTO would be a bit faster.
Click to expand...
The charger we use for these batteries is rated for 20A max.
The BMS is rated for 20-25A max for charging.
However it is wise to not to push the limits and maintain some margin.

I believe we can charge these battery say at 16A (20% below the rated limit) at average 12.8V, which is about 205W charging rate.
This is about twice as fast as existing dedicated batteries on the market which are charging at about 110W max.

If even faster charge rate is needed then:
The 20Ah LTO cells can be safely charged at 60A (3C) rate.
We can pair it with 100A or about 50A for charging rated BMS and using external 50A Victron charger we can charge at over 700W rate or 7x faster than any dedicated battery!!
Car’s alternator and $$$ could be the limiting factor.

Some additional info here, post #21, and post #36 :
https://dashcamtalk.com/forum/threads/ecoflow-and-viofo.51429/
 
EricSan said:
Battery charging is all about current flow and this is one of life's "there's no free lunch" situations. If you want the bucket to fill faster, you either use a smaller bucket (less battery capacity) or you fill it with a bigger hose (more current). There is no way around this, except to rotate batteries and always have one charging (use two buckets). Each battery chemistry has it's own limits of charge and discharge rates that are appropriate. I'm thinking that LTOs, since they are intended for electric vehicles, will feature the fastest charge and discharge rates right now. Faster charging (up to 20A) is something that I could implement as the main battery in my Volvo is in the trunk where my parking battery will live, so access is easy and close by, but my situation doesn't call for this need.

I fiddled with the charger again this morning and adjusted the output voltage up from 16.5v to 17v. This seems to have eliminated the orange warning light on the charger from coming on, though I need to play around and observe its behavior a little more. I'm thinking that 16.5v volts from the charger didn't provide enough voltage headroom for the BMS to charge the batteries when they were close to full capacity (starting around 15.5v). It seems that there is a "sweet spot" in terms of voltage output level (not too low, not too high) where the charger operates without tripping the alarm. I need to run the battery down a bit and see how it behaves as I charge it up.

From what little the web page where I bought it indicates (because it doesn't come with any paperwork at all), the orange light indicates a voltage/current starvation issue or a short circuit. It is called a "CC Indicator" (for constant current?) and the explanation says: "The light will be lit and automatically recovery will be enabled when the output current limit voltage drops, output is short-circuited, or with output over-temperature protection." Since it is not a short-circuit or over-temp situation, it's got something to do with voltage and current settings. I'm using a Meanwell LRS-200-12 switching power supply that has variable voltage output (set to 13.4v) and can provide up to 200w, which is about 14.5A at 13.5v. So, it seems plenty capable of providing enough current and avoiding a "current starvation" situation for the charger/BMS. Here's the charger I purchased: https://www.aliexpress.us/item/3256805949511895.html#nav-specification

Bumping up the voltage output for the charger predictably increased the current draw from the 12v utility outlet. 17v at 9A = 153w of total draw. Divide 153 by 13.4v results in a current draw from the car's electrical system of 11.4A. Most utility outlets are capable of delivering 15A (180w), I might end up backing the charge current down to 7A or 8A to have a little more headroom in the power supply. I have to see what the long term "steady state" battery usage is once I install it in the car.

After calibrating the charging current, the discharge current as shown in the app seems pretty realistic. I saw -0.2A draw at 15.91v, which works out to about 3.2w for the single camera by itself, which matches my earlier measurements.

Need to play around and measure its behavior some more.
Click to expand...
The BMS can stop charging either because the battery pack voltage has reached the protection limit, or because the individual cell has reached the protection limit. The latter is more likely, especially at extreme voltage levels where the imbalance increases rapidly.
My cell limit is 2.65V, which results in a total voltage of 10.6V (for 4S), the battery always stops charging because of the cell limit, just below 10.6V.

The CC indicator lights up when the input power/voltage/current is not enough for the output power, as a protection the charger will reduce the output voltage or current. I think the problem might be your power supply, although it is rated for 200W, I would check it to make sure it really maintains 13.4V and required amperage to match output power adjusted up for efficiency losses.

About calibration: the difference between the DVR discharge of 0.2A and the charging current of about 10A is significant (x50), so it is impossible to calibrate the BMS current for the two extremes. I think I calibrated it closer to the discharge level, but I can't check now because I took apart the battery to upgrade it to the 5S configuration.
 
Alternator definitely becomes the limiting factor when you start talking about 50A or higher charge rates. A typical car alternator is probably around 150A, for a bigger car/suv/truck or car with more electronics, alternators likely go over 200A. I would not attempt to draw an extra 50A out of the alternator in my car - that would surely cause problems.

As for the CC light on the charger board, it hasn’t come on since I bumped the charge voltage from 16.5 to 17.0v. My cell cutoff voltage is also set to 2,65v, but the cells weren’t getting there. The charger stopped charging closer to 2.5v each and then the orange LED came on. My guess is that it was a voltage/power starvation issue. Everything seems very well behaved now. With a 7A charge rate, the charger board is a bit cooler at only 6-7c above ambient.

I wasn’t considering the resolution differences with calibrating the BMS ammeter, good point! It seems reasonably close, though. My clamp meter also has some consistency issues, I presume they all do. The reading varies depending on where in the clamp the wire sits. The best way to measure current accurately is across a power resistor, but that’s not super convenient in situations like this…
 
Continuing to play with discharging and recharging the battery and I'm noticing some strange behavior with the orange CC LED on the charger board. I've verified the Meanwell power has a pretty accurate 200w limit. Charger voltage is set to 17v and current set to 7A for a 6S battery pack. Here is what I'm seeing:

I ran the camera for another 12hrs overnight. Battery voltage was down to 14.67v, individual cells were down to 2.44v. I initially started to charge the battery at 7A and after a few seconds, the orange LED illuminated. I unplugged the external PSU, turned off the BMS and the dashcam and then restarted everything. Orange LED was back on again within a few seconds. I power cycled the whole setup again and reduced charging current to 4.0A (I'm starting the dial in the charge rate to match parking needs and daily drive time for my son). Orange LED was back on again within a few seconds. I let the charger run like this for a while. The charger board temp was about 8c over ambient. After about 40mins or so, the orange LED went out. At this point, the overall battery voltage was 15.41 and the individual cells were at about 2.57v. The battery pack continued to charge up to 16.0v with only the charger's green LED illuminated. The temp of the charger board dropped to about 5c over ambient without the orange LED on. When the battery was fully charged, the BMS/charger board began to cycle on and off as the camera was drawing power. The orange LED stayed dark during this time.

I need to run a few more discharge/charge cycles and play with things, but at this point, I'm wondering if "too much" of a voltage difference between the battery pack state of charge and the output voltage setting of the charger is what is causing the orange LED to illuminate. The "System Log" in the App doesn't have any messages that seem relevant to the LED status.

Any ideas what is going on here? I'm wondering if the orange LED signals something like "low efficiency operation" of the charger due to the voltage difference between the battery pack and the charger's voltage setting of 17.0v. Have to play around some more. I need to connect a 12v lightbulb with the Drok regulator or something else to run the battery pack voltage down faster than the dashcam does so I don't have to wait so long to experiment...
 
I am not sure why, your orange LED is turning on.
Did you verify the voltage and amperage at charger's input and output with multimeter? So we can compere power in and out of charger and efficiency?

I can’t replicate this issue with two different chargers.

First, I removed the upper cover from my LFP battery which is currently testing in my jeep to see if orange LED ever turns On – and the answer is never. (I charged it with engine running and with just ignition with engine off, the charging voltage is set to 14.4V and charging current is set to 7A for LFP).

Second, I reconfigure my 4S LTO into 5S configuration.
I set my power supply to 12.8V out and I set the second charger to about 13.5V out and 8A charging current.
I fully charged the battery, until BMS turned the charger off due to my cell limit of 2.7V or about 13.4V for the battery pack.
During the charging, I played with power supply's output voltage from about 11.4V and to about 14.5V (full range of my power supply) and it basically did not affect charger's output voltage/amperage, and I never saw orange light.
 
EricSan said:
... When the battery was fully charged, the BMS/charger board began to cycle on and off as the camera was drawing power ...
Click to expand...

To limit cycling frequency you can set Over-Voltage Protection Recovery (OVPR) more lower relative to Over-Voltage Protection (OVP).
For now, I set my OVP to 2.7V and OVPR to 2.6V.

Edited: OVP and OVPR abbreviation.
 
Last edited:
Thanks for the tip on OVP and OVPR. I was going to ask what these meant .

I think I’ll start connecting the parts for my second battery and compare to the first one. Guess there is an advantage to having to build a second battery beyond just having it cost twice as much.
 
You must log in or register to reply here.
Back
Top