Need an AC/DC Charger - ISDT BattGo T8?

[Larry619]

Building my first 24V LiFe battery is thrusting me into the world of power supplies, pack chargers, balancers, switching supplies, benchtop supplies....my head is spinning.

So far my searches have turned up a limited selection of 24V LiFe specific chargers. The hard part is that they’re all topped at varying voltages - 28.8v, 29.2V, 29.6V, etc. If I am trying to achieve a specific state of charge, it sounds like I’m looking for a customizable voltage. Add the criteria for something above 20A and the choices are even more limited and expensive. Then there’s the cell monitoring, protection...it’s becoming too complicated to keep track of the parts list.

I’m looking for that one device that can help me bottom and top balance, and monitor individual cells. My sights were at first on the CellPro Powerlab 8, which is out of stock everywhere.

In comes the IDST T8.

Is this good? What are your thoughts? Do I still need a power source? What else do I need to get this 24V charged and balanced (top and bottom)?

Much thanks in advance.

ISDT T8 1000W DC Charger, ICC1020 https://www.amazon.com/dp/B0776PW3NW/ref=cm_sw_r_cp_api_i_h36TEb6BEBCQ8

 

[Larry619]

I am not sure what your use case is for charging 12v from 24v battery, but I just started using this BattGO T8 to charge cells and batteries. Very flexible in regards to input voltage, charge current and charge voltage. So far I am pretty impressed. 30A charging is quite nice. Being able to charge individual cells or cells in parallel is great for top/bottom balancing.

Amazon.com: ISDT T8 Battgo Lipo Battery Charger/Discharger, Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb: Electronics

Amazon.com: ISDT T8 Battgo Lipo Battery Charger/Discharger, Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb: Electronics

www.amazon.com

The only inconvenience might be that it requires XT-60 connectors for input and output power.

@MisterSandals i’m interested in your input since you seem to be the only one actually using it currently. What do I need to get this unit going? I saw that it says “1000w” up to 30A ....but I’m assuming you still need a power source to feed through this device? Sorry...I’m so new to this.

 

[MisterSandals]

@MisterSandals i’m What do I need to get this unit going?

I have several LiFePO4 batteries and charge one battery from solar. This battery becomes my power supply for the T8 to charge the other battery or cells when top balancing.

The XT-60 connectors need to be soldered which takes a little effort but end up very nice in use. Shrink wrap greatly aids sturdiness. I put male and female pigtails on each battery, female for charging and male for providing power.

Each battery needs a loom to be balance charged which is surprisingly even across cells without a BMS.

Maybe this pic helps. Not very tidy as everything in motion.

 

[MisterSandals]

Let me know if you want a parts list and links of wires and connectors and stuff for this. Its almost all on amazon.

 

[Larry619]

I have several LiFePO4 batteries and charge one battery from solar. This battery becomes my power supply for the T8 to charge the other battery or cells when top balancing.

The XT-60 connectors need to be soldered which takes a little effort but end up very nice in use. Shrink wrap greatly aids sturdiness. I put male and female pigtails on each battery, female for charging and male for providing power.

Each battery needs a loom to be balance charged which is surprisingly even across cells without a BMS.

Maybe this pic helps. Not very tidy as everything in motion.

View attachment 12965

This is fantastic. Since you already have a rotating charged bank, you’ve eliminated the need for a DC power supply.

Could you recommend a good DC supply that can charge my 24v 65ah battery build? If I did your method I believe I would need a battery of at least equivalent voltage and larger capacity. I’m trying to achieve at least 20A of charging.

I still like the idea of the T8 since it has individual cell monitoring. Do you think i can use a regular lifepo4 Charger or would I need a straight DC power supply? I Know that dedicated charges have different “stages” so I don’t know how that would work as a psu for the T8.

 

[Ampster]

Could you recommend a good DC supply that can charge my 24v 65ah battery build?

For an inexpensive option I used Meanwell power supplies of the voltage range and Amps I needed. They usually have a small voltage adjustment screw that became my CV (Constant Voltage or Absorb) point, but I usually used a voltage controlled relay for redundancy. Long term a charger that has programmable set points is a better solution because your can adjust the CV stage based on either time or finishing Amps. You pay money for that flexibility.

 

[Larry619]

For an inexpensive option I used Meanwell power supplies of the voltage range and Amps I needed. They usually have a small voltage adjustment screw that became my CV (Constant Voltage or Absorb) point, but I usually used a voltage controlled relay for redundancy. Long term a charger that has programmable set points is a better solution because your can adjust the CV stage based on either time or finishing Amps. You pay money for that flexibility.

Did you use it as a direct charger for your pack? Set the upper limit voltage where you want it? I’m assuming once the desired voltage is set, the power supply pushes 0 amps at the end?

Sorry I’m still trying to wrap my brain around absorption voltage vs float voltage.

My use case for an AC Charger is for intermittent charging. Once the pack reaches full charge it gets unplugged. But I’m also looking for something I can use for the initial Controlled balance.

 

[Craig]

This is fantastic. Since you already have a rotating charged bank, you’ve eliminated the need for a DC power supply.

Could you recommend a good DC supply that can charge my 24v 65ah battery build? If I did your method I believe I would need a battery of at least equivalent voltage and larger capacity. I’m trying to achieve at least 20A of charging.

I still like the idea of the T8 since it has individual cell monitoring. Do you think i can use a regular lifepo4 Charger or would I need a straight DC power supply? I Know that dedicated charges have different “stages” so I don’t know how that would work as a psu for the T8.

I like these for DC-DC charging they have a 12 Amp max at up to 65Volts https://www.amazon.com/Converter-DR...rds=drok+buck+converter&qid=1589139634&sr=8-3

 

[Ampster]

Did you use it as a direct charger for your pack? Set the upper limit voltage where you want it? I’m assuming once the desired voltage is set, the power supply pushes 0 amps at the end?

Yes, but they are not a long term great solution. I have lost several over the years including variable power supplies. I suspect the surges from the batteries may have blown an internal fuse or diode and I don't have the technical skills to diagnose those failures. I don't think they disconnect like a charger does so they sometimes create a Vampire drain. You are partially correct that once the desired voltage is set, but it is the battery that pulls the Amps and it Kirckoffs law that results in the Amps tapering to zero.

Sorry I’m still trying to wrap my brain around absorption voltage vs float voltage.

No worries. I only recently learned this from reading forums like these and sharing knowledge is rewarding. Absorb is a term that is commonly used in chargers and apparently comes from the Lead Acid battery culture. I think sometimes it may be called Boost. The easiest way to think of it is a Constant Voltage source. That compares to Bulk which is a Constant Current source and CC is where most of the work is done in charging a battery. Those two are the only stages needed to charge a Lithium battery.
Float is a term that is sometimes called trickle charging. It is a low current CV mode most often used for Lead Acid batteries because they self discharge and a float or trickle charge can maintain them. I do not use Float on my packs because even a prolonged voltage source can hurt a Lithium battery over time. In a stationary application like an inverter powering a home some people turn on Float at some point below the CV voltage setting of Absorb to compensate for the load of the home and in order to use the available solar energy to charge the batteries. If charging a Lithium battery in an RV, a car or other device that might not be used right away I would definitely disable float.

My use case for an AC Charger is for intermittent charging. Once the pack reaches full charge it gets unplugged. But I’m also looking for something I can use for the initial Controlled balance.

I am not sure what you mean by initial controlled balance. If you mean when you put all your cells in parallel and charge them, then that is one of the applications in which I have used power supplies. I have one 10 Amp 3-4 volt Meanwell that I use to do the initial pack balancing in parallel. I have another higher voltage and higher Amperage one that I use with my capacity tester. A single variable Power supply would serve those purpose but I blew up my last one trying to charge a golf cart pack. There are downsides.

 

[Larry619]

Yes, but they are not a long term great solution. I have lost several over the years including variable power supplies. I suspect the surges from the batteries may have blown an internal fuse or diode and I don't have the technical skills to diagnose those failures. I don't think they disconnect like a charger does so they sometimes create a Vampire drain. You are partially correct that once the desired voltage is set, but it is the battery that pulls the Amps and it Kirckoffs law that results in the Amps tapering to zero.

No worries. I only recently learned this from reading forums like these and sharing knowledge is rewarding. Absorb is a term that is commonly used in chargers and apparently comes from the Lead Acid battery culture. I think sometimes it may be called Boost. The easiest way to think of it is a Constant Voltage source. That compares to Bulk which is a Constant Current source and CC is where most of the work is done in charging a battery. Those two are the only stages needed to charge a Lithium battery.
Float is a term that is sometimes called trickle charging. It is a low current CV mode most often used for Lead Acid batteries because they self discharge and a float or trickle charge can maintain them. I do not use Float on my packs because even a prolonged voltage source can hurt a Lithium battery over time. In a stationary application like an inverter powering a home some people turn on Float at some point below the CV voltage setting of Absorb to compensate for the load of the home and in order to use the available solar energy to charge the batteries. If charging a Lithium battery in an RV, a car or other device that might not be used right away I would definitely disable float.

I am not sure what you mean by initial controlled balance. If you mean when you put all your cells in parallel and charge them, then that is one of the applications in which I have used power supplies. I have one 10 Amp 3-4 volt Meanwell that I use to do the initial pack balancing in parallel. I have another higher voltage and higher Amperage one that I use with my capacity tester. A single variable Power supply would serve those purpose but I blew up my last one trying to charge a golf cart pack. There are downsides.

What a wealth of information here! I get what I’m after then. My build is for an emergency Solar generator where an AC Charger will only be used to top off the batteries when AC is available and then likely put into storage or ready for the next single task. It’ll likely only see continuous use in a prolonged grid down scenario. So I’m really just concerned for the absorption voltage and then it will be unplugged - no float.

I think I’ll be looking for a reliable and dedicated 24V Charger when my pack is balanced and built. The hard part are these lifepo4 chargers have varying voltage cutoffs so I guess I’m looking for something that stops at 28.8V? Some of these end at 29.2V which is a little higher than I’d like. At least 28.8V will get me to a state of charge that I’m comfortable with. The programmable Victron AC chargers are attractive if I can get past the 12A current. I was hoping for something closer to 20A.

Next is having something like your Mean Well adjustable PSU for the initial balance. Is charging the cells in parallel (3.2V) the most preferred method? I’ll likely get a cheap pack meter that’ll help me view all cell voltages at once while it’s charging to monitor runaway cells.

Just trying to minimize the gear purchases cuz Lord knows i have little self control. ?

Thanks so much!

 

[Ampster]

I think I’ll be looking for a reliable and dedicated 24V Charger when my pack is balanced and built. The hard part are these lifepo4 chargers have varying voltage cutoffs so I guess I’m looking for something that stops at 28.8V? Some of these end at 29.2V which is a little higher than I’d like. At least 28.8V will get me to a state of charge that I’m comfortable with. The programmable Victron AC chargers are attractive if I can get past the 12A current. I was hoping for something closer to 20A.

28.8 Volts is a full 3.6 volts per cell which I think is too high for LFP and would not give you much more energy and shorten the cycles you could get if you went to 3.4 volts per cell. 29.2 is the full 3.65v per cell and for the greatest number of cycles I would suggest lower. That is why the Victron might be the best. The difference between charging time of a 12A vs a 20A is insignificant in the long run. If it is for storage I would go even lower because these cells do not self discharge. I regularly set my Teslas at 70 to 80 percent as do most owners unless I am planning a trip. 80% with LFP might be 3.3 to 3.4

 

[Larry619]

28.8 Volts is a full 3.6 volts per cell which I think is too high for LFP and would not give you much more energy and shorten the cycles you could get if you went to 3.4 volts per cell. 29.2 is the full 3.65v per cell and for the greatest number of cycles I would suggest lower. That is why the Victron might be the best. The difference between charging time of a 12A vs a 20A is insignificant in the long run.

I think you just helped me make up my mind on a dedicated charger!

 

[Larry619]

Here’s another angle:

Will This Mean Well 24V 25A PSU work with the IDST T8? looks like it would fit the criteria to charge the pack near 20A (I wouldn’t max it out to 25A) while controlling individual cell voltages. The T8 would even be able to control a smaller amperage to the packs/cells I believe?

MEAN WELL SE-600-24 AC to DC Power Supply, Single Output, 24V, 25 Amp, 600W, 1.5" - 295902 https://www.amazon.com/dp/B00DEDB2U2/ref=cm_sw_r_cp_api_i_W5hUEbDB5YSWS

Edit: The T8 input voltage range is up to 40V, so something like this 36V/27A might work while providing more current?

36V 27.8A 1000W Universal Regulated Switching Power Supply Driver for CCTV camera LED Strip AC 100-240V Input to DC 36V https://www.amazon.com/dp/B07FBQJTWZ/ref=cm_sw_r_cp_api_i_xgiUEb56AH8V8


$100 for the T8 plus $90 for a 24V/25A PSU sounds really decent ...unless I’m missing something.

@MisterSandals and @Ampster, your thoughts?

 

[MisterSandals]

Could you recommend a good DC supply that can charge my 24v 65ah battery build?

I do not have any recommendations, sorry. Ampster and Craig seem like they have good info and ideas.

I do not have any idea what power supply would be best for the T8, i have only used various batteries, in different combinations. I will give it some thought and follow those links to see if i can add anything. Sorry.

 

[Ampster]

My apologies, I jumped inrto the middle of that thread without reading that you were thinking of using that T8 hobby charger as your BMS and charge regulator. In that case as long as you find a power supply that is within the voltage and current range of that you should be fine. But back to the charge percentage and voltage issues I was talking about for storage, is that T8 capable of setting different parameters? I see that it has generic settings for LFP, LiPoly, NMC and some others but unless it has user adjustable voltage settings, then everything I have said so far is useless. I have never worked on any 24 volt devices.

 

[MisterSandals]

It has quite a few charge and discharge parameters. Here is the brief spec, there is a 19 page user manual written in real english. Its quite good in my opinion. But, better yet, I'm a user-interface snob so i expect devices to be intuitive and usable with a little common sense. I think the T8 meets this criteria, i don't recall looking in the manual.

 

[Ampster]

I briefly read the manual and it has 6 fixed setting of which there is one for LFP. I did not see a customizable setting if for example you wanted to use lower settings for LFP to improve the number of cycles.

 

[Larry619]

I briefly read the manual and it has 6 fixed setting of which there is one for LFP. I did not see a customizable setting if for example you wanted to use lower settings for LFP to improve the number of cycles.

Ouch...close but no cigar. I’ve been scouring YouTube videos for the selectable voltage ranges for LiFe on the T8. It looks like the default per-cell voltage is 3.65V with a selection between 3.60V to 3.70V with 0.01V increments. I was hoping that it had an option to go as low as 3.50v at least.

Maybe @MisterSandals can confirm. Maybe there’s a firmware update?

Here’s the YT video for reference. I wish it was in English but I get the gist of what he’s trying to accomplish. See LiFe Settings at 2:42.

 

[Larry619]

Here I go going down a rabbit hole late at night in the internet.

Stumbled across Joshua Bardwell who apparently reviews the RC world. He reviewed the Hobbymate D8 Duo that looks like it operates on similar software to the ISDT line. It has a customizable lithium profile (LiXX) which can go as low as 3.50V.

EDIT: Darn...good only up to 6S. ?

What’s cool is that it has a built in AC PSU up to 200W or option to 650W on DC.

 

[MisterSandals]

It looks like the default per-cell voltage is 3.65V with a selection between 3.60V to 3.70V with 0.01V increments.

Sorry for the slow reply, today was a serious honeydew day.

Yes, i can confirm that the LiFePO4 battery has that voltage range. I checked the other cell types and there is no other type that goes in the 3.x voltage range.

With a configurable BMS, if you set your high voltage cutoff to your voltage of choice, that would probably be a good solution for unmonitored charging.
As i approach my target voltage or if i am going to be away for some time, I will set the charging amps lower to make it more likely i can stop when i choose.

Its fantastic for top balancing. I am not sure when i will do this again so there's that.
Regarding utility battery charging, i try to charge to 3.4-3.5. If i charge to 3.6v on occasion its not a big deal.