To be very precise it should be called portable charger on the go.
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Skimmed through the whole thing. Cus I’m a lazy mfker. Did OP end up doing the 2s5p external pack?
For the 10s to 12s boost, it would only work if it’s plugged into loopkey and cell voltage difference between internal and external pack is small, and Metr to reflashing the # cell and voltage cutoff settings. Otherwise, you might risk completely destroying the internal pack when you run it dry.
I’m thinking of making a 13s1p pack with my cheap 2000mah Sanyo18650UR for my Hummie. Kited with a cheap charge discharge BMS and boost converter to plug in at the charge port. Does anybody know if the BMS will limit current draw or should I just get a boost converter than has a limited Current rating. (Will essentially step up to 54.6 voltage applying CV to the charge port all the time until discharge bms cut off the external pack)
Edit: actually I’ll be setting the boost to 52v to be safe, cus I don’t usually fully charge my batteries anyways unless I wanna be a fast boi that day. Oh and that pack will only be used as a range extender.
What happens when I plug in 52v at the charge port and international pack is higher?
Well I’m finally getting around to getting this implemented on my board. Thanks to everyone who’s lead the way on this.
The key thing for me with this add on is to have a range boost that can be added in seconds when needed and then removed in seconds leaving my board all sleek and beautiful again.
So far I’ve built a 10s3p 30q pack shaped to fit above the charge port and around the boost converter and bought the boost converter and watt meter.
Next step will be the enclosure. I’m going to cnc a Delrin top and bottom with sheet ABS between as walls. I’m going to have 2 loop keys, one for powering on the boost pack and one anti spark to enable charging power to the board. The watt meter will be incorporated into the lid.
The charge port will be connected as soon as the extender is installed…
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Looking good! I have a feeling this is going to work out well for you 
I noticed that having the boost converter charging while riding was a great buffer for the reduced efficiency riding Pneumatics, so that too!
Can’t say it enough, couldn’t get by on my 10S4P without my boost converter setup. I’m considering building a 12S8P, but even then still considering continuing to use the boost converter.
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So I finally tried to build my own range extender but encountered a problem - magic smoke.
So my setup was this:
6s3p 30Q -> Protection Module -> Step-Up Converter -> Charging port
When there was no load, it was doing what it was supposed to do. But during a load, the insulation on the wires from the 6s3p going to the protection module melted and caused a short. It is possible I might have used a thin wire (although it’s the same wire I’ve been using to charge my board at 4A). Is there a minimum AWG wire I should be using on this setup? Or is there another reason why it happened?
Keep in mind that the current on your boost battery side will be greater than that of the charge current.
So if your boost converter was converting from 12V -> 24V with a 4A output, your real current draw from the boost battery would be 8A.
It sounds like your main battery was nearly full and your boost battery was low, leading to a very high current draw.
Also, the relay for switching the protected battery on and off is rated for 14V, 20A. Exceeding that could cause additional issues (this is the manufacturers fault, since the board is designed for up to 36V)
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It was actually the opposite, my main battery was 40% and the boost battery was full. After the incident, all the components still work fine. Is it worth trying again but this time using a bigger gauge wire from the boost battery to the protection module?
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Well that’s probably your problem. Was it possible that the main battery voltage was actually higher than the range extender?
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Output voltage from the step-up converter was a constant 42v.
Oh fair enough, that makes sense… I’m really not sure what’s wrong
mines coming along nicely hehe
10s 8000mah 10s4p pack on top of my nano tech 10s2p 9000mah. so probs an extra 18-20km on top of 25km range
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You just described an unregulated charger! This is not a boost battery pack that can stay connected during a ride. The constant 42v requires considerable current from your 6s pack. Anything other than a fully charged main pack will attempt to draw serious amps from your “charger pack”. All sorts of overheating will occur, including and especially the internal wiring to the main battery. When they melt completely and short…
thats not quite true. the boost converter regulates the amps, preventing it from drawing too much. when the 42v boost is connected to a half charge pack, the volts drop to what ever the pack is. same with a regular wall charger.
@DeathByBacon did you adjust the amps during a bench test to ensure it was set appropriately? you’ll need a watt meter for this
If you read through this thread, that’s what they’ve been doing. Using a 6s pack + step up to charge 10s, even 12s packs.
But that’s another thing that came to mind right away. “Maybe it drew too much amp because my main battery was already quite drained at 40%. How have the others used it? Should have I used it on the get go and not until the main battery’s been spent?”
Is you main battery an OEM pack and connected to an OEM charge port?
I did a 10 minute ride around the block to drain the battery a bit so I could test my setup. It charged like a normal charger, but then again it didn’t have any load.
I set the step up converter to discharge at 2A, 42V. I’m not sure if I can regulate the amps I can draw from the booster battery though.
The main pack is a 10s3p 30Qs pack that I made myself. The charging port I’m using for the pack is a xt60 with 16awg wires.
I am sorry I thought this was to stay connected during the ride. If it is a charger you want, Tinnie is correct about regulating current. To melt your battery wires you need to be pulling over 10A thru thin wires. Setting the current draw to 5A out should get you close to 10A in.
I suspect your regulator is not regulating too well.
thats very conservative. im surprised that cause a melty wires. feel like we’re missing something here
@DeathByBacon can you post pictures of your full setup (except with the range extender NOT plugged into your board)