Solo Multi-Charger

[Pedals2Paddles]

Nice. What do you have the LEDs connected to?

You can get a computer case fan grill on amazon dirt cheap. Cut out one big hole for the fan and use the grill to cover it. You'll get more airflow and prevent something from getting stuck in the fan.

 

[STMPNGRND]

LEDs are not hooked up. I had those extra laying around and originally thought about each booster having it's own on/off switch. The LEDs would have been just a power on indicator but couldn't find any flush push button switches I liked for a reasonable price. I'm into this about $75 and didn't want to cross $100 at the time. So having removable battery leads was plan B..boosters still powered but short risk is removed. I would prefer though to find switches so not all boosters run all the time if not needed.

 

[Deleted member 5038]

Here's my solution to charging multiple batteries at once:

I am using 5 DC-DC 250W boost converters to which I have attached heat sinks. Each one is set to 95W - which means batteries are charged at just over 1C. It is faster than the 3DR wall plug and, most important, I can hook it up to the car battery and use it on the move.
The battery connectors are a mix of 3d printing and cutting copper blades. Quite a lot of work went into making them.
I might add some metal mesh on the sides to protect the electronics, but for now I am just careful with where I place it.

I hope someone will find this useful.
Cheers!

Hi Peter,

Thanks for your great contribution.
I have one/two questions:
- This Power Supply 60A 1200W is no longer available on market (France), been apparently replaced by 50A, 1200W. As I wish to charge 6 batteries (6 boost converters), will it be enough ? (I guess yes, but...).
- When you say hook on car battery, you mean to the cigar lighter (limited, no ?), or direct to the battery ?
Regards
Michel

 

[Maddog]

Hi Peter,

Thanks for your great contribution.
I have one/two questions:
- This Power Supply 60A 1200W is no longer available on market (France), been apparently replaced by 50A, 1200W. As I wish to charge 6 batteries (6 boost converters), will it be enough ? (I guess yes, but...).
- When you say hook on car battery, you mean to the cigar lighter (limited, no ?), or direct to the battery ?
Regards
Michel

The 50 A will work. Peter said he is hooking up direct to battery as cigar lighter can only handle 120W, or 1 charger.

 

[peppys]

@thePeter are you still not selling these?
Please take my money!

 

[Deleted member 5038]

The 50 A will work. Peter said he is hooking up direct to battery as cigar lighter can only handle 120W, or 1 charger.

I calculated that charging at 14,8V will deliver max : 14,8V x 50A = 740W ; spread over 6 batteries, it will deliver max 123W per battery; as efficiency is 94%, it will remain : 94% of 123W= 115,6W.
It is enough to provide the 95W needed to each battery.
If using the same unit for charging (at same time) other batteries (controller, GoPro, iPad, ...), it leaves 170W which looks to be fairly enough.
Am I right in these assumptions ?
Thanks for help.

 

[PdxSteve]

You're a little off. It uses 16.8V to charge, not 14.8V. Just like a 12V car battery charges slightly higher than 14V depending on how many cells, etc.

16.8V x 6A = 100.8W x 6 batteries = 604.8W (at 16.8V)
then divide by 12V to get A for the 12V power supply
604.8W / 12V = 50.4A@12V

Then throw in the inefficiencies of the converters.

50A (at 12V) is barely enough to do 6 batteries, but that TOTALLY depends on how discharged your batteries are and how many you are charging at once. If a battery is about 10% full, it will draw ~6A (assuming you are not using the stock charger) and then slowly trickles down to 2mA as it charges. So there is a big load up front that drops off quite rapidly. After charging for about 30 minutes that same battery is now drawing about 3A. If you threw 6 batteries on that were all at 10% at the same time, that would be quite a load on the PS up front. But again, it immediately starts dropping off as the batteries charge.

Here are some graphs I did of the stock charger vs a CC/CV converter set at 6A using the SMBus to sample the data as they were charging. As time increases, the Voltage increases (charging) and the Amps drop as it fills up. Follow the link in the first post here for the graphs and then look in the lower right of the screen (you might need to scroll a bit): Battery Charging Graphs

 

[jerryn]

My solution was to buy a charger for each battery I have. 4 batteries and 4 chargers. I got the OEM chargers for $20.00 each. I just needed to buy 3