Lipo battery for running an NUBM37

[additude]

My plan is to run a single driver to an NUBM37 and configure the NUBM37 as 2 parallel strings of 12 diodes each. So, the driver needs to be capable of 55v at 4.5a.
I have these drivers in mind:
Drivers
Driver
Driver

The batteries I'm thinking of using are two Lipo 14.8v in series.
Batteries
Batteries

I "Think" I am on the right path.
Comments?

 

[RedCowboy]

Just remember watts is watts.
54V @ 4.5A is 243 watts so if you bridge in a 2nd string of diodes you split the watts ( in theory, if balanced ) you would only get 2.25A to each diode.
You would need 9A at about 54V for both parallel strings of 12 diodes to get 4.5A........ however if one string has slightly different resistance due to manufacturing inconsistencies or if a diode fails, then one string will get more than half and the other less.

This is why they run them in series and in the projectors they have a driver for each string that's in series, so you are better off adding a 2nd driver for the 2nd string of 12, otherwise you need 9A for both parallel strings to get about 4.5A in theory if they are balanced.

 

[additude]

I understand.
I think if I just lower my expectations and keep to the spec of 98V @ 3A concept instead of 4.5A, split into two strings of 12 each, I can be at 49V @ 6A @ 294W and that may be an easier pill to swallow.
Then the consideration becomes the input to the driver. I am trying to make this portable, so space is an issue. One driver, feeding two strings might be a smaller footprint than 2 drivers. For a driver to work properly, the input wattage needs to include the driver inefficiency and be greater than the load output total wattage. So, two 14.8V Lipo's in series is 29.6V, would be supplying 325W (294W + driver loss) to the input, which is about an 11A requirement.
By what I can calculate for this circuit is that two, in series, 14.4V(29.6V) - 1600mAh batteries would provide power up to 80% discharged for about 7 minutes. A 2200mAh battery would give me about 9.6 minutes.

 

[RedCowboy]

You can look at what others have built such as Smackitup's repurposing a cordless drill body or do something unique and you can use just 1 graphene battery and work it hard with a shorter runtime.

I like the old linear lm338 regulators configured as current limiters that Drake/Styro used and he used one for each string so the voltage wouldn't need to be as high, yes they are linear, but they are small and in series the losses are lessened.

I explained in this thread how I use the lm338 and how to figure how much battery you need, the main concern is voltage sag under load..... graphene can put out a lot of current with low sag so maybe you want to use lm338's to keep the package smaller ?

edit: You could learn to build your own switching/boost driver to take up minimal space, I plan to build some in the future, but I'm not well practiced enough to teach anyone else how to ATM.

The more we learn the stronger we become, for knowledge is power.

 

[additude]

Thanks for all your help.
I thought about using the LM338 in the TO-220 package, then decided to opt for the simple premade and less time-consuming option. I am trying to model Styro's hand-held. I picked up a radar gun and gutted it. I'm waiting on other components. Heatsink is here on Monday, batteries here on Wednesday(?), Voltage and Temp displays are on the way. I was interested in the Graphene square.... but thought I'd have more fitting options with the rectangle. I'm really interested in getting the '37 array in hand, getting it heat-sunk and testing it out. It should arrive end of month.

 

[405nanoMatt]

You can look at what others have built such as Smackitup's repurposing a cordless drill body or do something unique and you can use just 1 graphene battery and work it hard with a shorter runtime.

I like the old linear lm338 regulators configured as current limiters that Drake/Styro used and he used one for each string so the voltage wouldn't need to be as high, yes they are linear, but they are small and in series the losses are lessened.

I explained in this thread how I use the lm338 and how to figure how much battery you need, the main concern is voltage sag under load..... graphene can put out a lot of current with low sag so maybe you want to use lm338's to keep the package smaller ?

edit: You could learn to build your own switching/boost driver to take up minimal space, I plan to build some in the future, but I'm not well practiced enough to teach anyone else how to ATM.

The more we learn the stronger we become, for knowledge is power.

I used Smackitup’s idea with a few additions/changes in hardware and it has worked great in this ugly ducktaped proof of concept condition for nearly 2 years now and haven’t paid a dime for batteries!The ones I use are the rechargeable ones that came with the drill and I have had it for nearly 20 years so I consider it a freebie now also since it has long since earned it’s cost back .So I would say that makes Smackitups design /concept a GENIUS level idea!Oh yeah this is a 74 watt nubm 34 I believe .I get the numbers mixed up a lot .Anyway it’s the 14 diode mdp chip from nichia

 

[additude]

I used Smackitup’s idea with a few additions/changes in hardware and it has worked great in this ugly ducktaped proof of concept condition for nearly 2 years now and haven’t paid a dime for batteries!The ones I use are the rechargeable ones that came with the drill and I have had it for nearly 20 years so I consider it a freebie now also since it has long since earned it’s cost back .So I would say that makes Smackitups design /concept a GENIUS level idea!Oh yeah this is a 74 watt nubm 34 I believe .I get the numbers mixed up a lot .Anyway it’s the 14 diode mdp chip from nichia

405nanoMatt ----
Thanks for posting your rig.
Secondly..... No reason to ever call Duck Tape UGLY!!! Duck Tape is one of the "Male Essentials". Anything incorporating Duck Tape has a inherent beauty and usefulness all of its own. Some of the greatest creations have been created with Duck Tape and even NASA was saved by the use Duck Tape...and to think that the NASA engineers even thought to put it in the astronaut's tool kit...is recognition enough
So what diode array did you use for your rig?
What kind of driver did you go for and what battery voltage is the drill?
Is it an 18V?
What is the run time on the battery?
I've seen that heatsink online, does that work well? or good enough?

 

[additude]

I just gave this 600W driver a load test and it handled it quite well. I put 32V @ 10A on the input and with 8.6 ohms (Static Resistance) on the output I was able to set it up for 49V @ 5.7A. So, I am confident that I can get 49V @ 6.0A thru 2 parallel strings of 12 diodes. I understand the use of two drivers as pointed out by RedCowboy, but I think the minimal space issue is reasonable to keep it to one driver.

DRIVER

 

[RedCowboy]

I have not used THIS DRIVER yet, but I have just ordered one to try out, supposed to be good for up to 120VDC output so all 4 strings could be run in series.

There may be similar with a smaller footprint, just need to search them out.

 

[additude]

That looks cool. 4.5" x 4.2" x 2.5".
By the description, it seems to suggest that it retains its output settings on power down, but it doesn't really make it factual.
Hopefully it is set once and forget...

 

[RedCowboy]

It says it has 10 storage groups..... like you can have 10 preset voltage and current limits set and I expect whichever one you are using when shut down is what you will have when powering back up, same as programmable LED flashlight drivers, but I will figure it out when it arrives in a few weeks from China.

 

[additude]

I think you are right.... I didn't read over well enough.... I ordered 2 as well...
Getting anything capable of 120VDC at 15A is a must have....
I'll probably never use all the 15A but having some DC at 120V can be useful...

 

[additude]

My NUBM34 has arrived and I am in the process of mounting it to a 3" x 3" round aluminum stock with 6-32 pan head machine screws. My setup is going to be two twelve diodes in series (2x6 series diodes) in parallel. 2S2P, power 50V by 6A.
What is going to be a best mechanical way to attach connections to the 8 leads on the array? Is soldering the best option? Is crimping an option?
I am going to twist two 20ga stranded silicone wires as power feed and interconnections.

 

[additude]

I am going to usi two 1.6 mAh RC batteries that have balancing connectors to drive my CC driver for the NUBM34. I am waiting for them to arrive. Can I connect the power output of the batteries as input to my CC driver without needing to connect the balancing connector? If I need to use the balancing connector, what do I need to make it work?

 

[RedCowboy]

It's best to solder and I would not use any crimp connectors on the arrays pins.

The balance connectors are used for charging each cell inside the pack independently or if you want to parallel the cells between two packs, so you couldn't use balance connectors between 2 packs and then put the packs in series as well, that would make smoke and fire.

Now if you plan to parallel the 2 battery packs, then you can connect balance wires between them.

 

[RedCowboy]

Something I do with my 18650's and 26650's is wright the date on them when I 1st get them unless I buy a couple dozen in bulk.

Then when I am using say 4 cells in a high drain device I 1st fully charge the 4 cells and then I will regularly check each cells voltage after some run time and see if they are all discharging evenly or if any 1 cell is a lot hotter than the rest, if they discharge evenly I mark them as a set and if one cell is falling short each time I replace it.

Note: A poor connection can cause heat.