power supply?
 

Hello,
looking for a good power supply for my charger as my old one finally gave out. what are some of the choices people are using at the track

I use the Motive Power Brick.It’s only 60 amps so might not meet your charging requirements.The Fantom units are good and are at 75 amps.

Find a used HP server supply on eBay ($20ish). Need to solder in a resistor, some connectors and you are good to go.

I have instructions here on how to convert an HP supply which is fairly easy to do in minutes with basic soldering skills:
https://www.rcgroups.com/forums/show...0#post43199655

The questions I have are:
What charger is being used?
What are your charging practices (what charge rates/how fast do you charge)?
What are your largest LiPo packs (cell count/capacity)?

I was sort of in same situation, but I needed a 24V power supply to get better use out of a charger's potential power. A charger needing input of ≥24V to get its maximum power... you may run into underwhelming performance with a 12V power supply.

A toolkit rc m8d. Indoors 10a max 2s. Outdoor 5th 2x6s 7600 mah packs @ 8A

According to the manual, the charger is rated for 10V min -49V max input and doesn't specify any variance for power output depending on voltage input:

https://images.amainhobbies.com/imag...ger_Manual.pdf


That said I would go with a 12V supply to keep costs and space/weight to a minimum ;)

I also did read the manual and you did forget a very important specification.
The input current is limited to 60A, with a 12v PSU you are limited to a 700w charge but that is still within the mentioned needs.

I was able to find (2) used Mean Well RSP-1000-24 for $65/set. Not the easiest to carry, but has the power when you need it.

much appreciated for including that important spec!


using watts law


W = V x A


700W - 10% charger inefficiency = 630W usable load

6S = 6 x 4.2V = 25.2V


630W / 25.2V = 25A


So you can charge 1 pack at 25A max or 2 packs at 12.5A each port without stressing a 12V PS where the supply I linked above is rated for 750W.

We did this for a slot car drag strip a few years ago. Worked like a champ.

Thank you all for the great info. But now that I have a power supply for indoor, New outdoor track has no power and was looking into a lifepo4 battery as a power bank. What are the opinions on a 250 ah lifepo4 to charge two 7600 6s or two 9000 2s for a race day. Never both classes on the same day

For outdoor with no power, I use a 100Ah LiFePO4. Myself and another racer share the same battery, running mod TC. We get a lot out of it, lol. At least 10 cycles a piece plus running tire warmers and other accessories. I did the math last year and figured we would need approximately 50Ah, which is about right. Generally I have to put in about 40% back into the battery when charging it.

So 250 might be overkill

That is going to depend. How many times do you need to charge the 6S batteries? How many mAh do you generally put back into them?

250Ah LiFePO4 - 12.8V - 3200W

7600mAh 6S - 25.2V - 191.52W <-- Full charge, not likely using all the capacity, so figure maybe 50%? Let's error on the side of caution and say 100W per charge.
Not dropping below 20% charge on the LiFePO4 gives you approximately 25 charges.
With a 100A battery you would get about 10.

There will most likely be some inefficiency needed to be accounted for, plus whatever else you want to power. I would feel comfortable saying you can get 8 charges of 50% or less and power whatever else you need (small things) with a 100Ah battery.

You need to do the math, add some overhead and try to stay above 20% charge on the LiFePO4.