+1
Assuming you need at least 1000W to keep flying, you’ll get 20 min if you’re lucky
I’d also watch the battery temperature. I have a temperature sensor in my BMS and when pushing it for too long it was triggered ( my batt is also 350Wh)
@ okp @pablo_foil
makes sense guys - can I ask you for what purpose you are using your systems for in your sessions and what average durations you get out of your setups? TX
G’day all,
First time poster long time lurker. I’m interested in building a spare battery for my FD assist. Does anyone know what BMS they use? Im currently trying to order a Daly 6S/40A but in the mean time I would like to build a battery without a BMS.
Can I get some input on what I need to consider?
I have purchased a kweld and all the associated build materials including 40 Samsung 30Q 18650s.
I own a iCharger X8 and I’m hoping to be able to balance charge with it.
Other things I would like your help with,
- Overdischarge (although there is a voltage readout in the battery box)
- Over current protection
- Could I damage the ESC etc without the BMS
- What are the potential consequences of making it 7S?
Thanks
Jared
I have a DIY 6S4P with 18650 with no BMS. I could not get it to fit in the FD case. You might need to go for a 6S3P using 21700. The XT90 connection will spark on plugging in without a BMS. This is solved with the anti-spark version of the XT90 plug. I balance charge with a digital RC charger. Easy to check on cell voltage status, Much nicer than guessing using a BMS. The standard FD ESC will only handle 6S. The ESC should have a low voltage cut off, but you’d need to know how to access the programme mode it to see what is it set at. This can be done with your remote.
Currently, have a new battery getting built by a third party, works out cheaper than DIY!
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Thanks mate.
Yeh I think for me, DIY was not a cheaper option but I am hoping down the track it will work out because I am interested in building bikes and skateboards etc.
I think I’ve already spent triple the amount a spare foil drive battery would cost me.
Cheers
Mine is intended for downwind foiling, but havent tested it for this purpose so far (when its windy im taking the wing).
For the moment i just brought it when the sea was flat, to confirm everything works fine. I guess i can foil for 15 minutes or so with it.
@ pablo
Thanks for feedback Pablo, that’s helpful. I wonder how much time folks get out of the FD+ at the end of the day - it will be interesting to talk to people once they start using them!
Yes, wit ha 6S3P 40T cells, it’s limited run time. Probably 15 minutes full speed. That’s one of the reasons, that it’s always good to have 2/3 packs so you can ride a bit more… especially if like me you carry the board for 300m to go to the ocean. I need to find a way to carry my deck, on the shoulder even it’s not heavy, it’s painful !
Hey did anyone try this so far? Maybe 2 of those electric-fins could lift you up with a big wing? Or maybe it can work as kind of a Foil Drive assist?
it will not work, it’s totally integrated and you loose all the benefits from a foil which is to remove as much drag as possible.
that’s the space left for the ESC & Receiver. I will cut a squared hole on the bottom of the case and epoxy/microballon + sikaflex the ESC to enable passive cooling.
enough space to fit a 40T 6S4P or 8S3P. I was hesitating between both, but I’m going with 6S4P because I could also fit my 6S8AH Graphene lipos… and get more batteries with me
!
What ESC do you plan to use? I have had good luck with 3m 5200 for watertight pass-throughs. Its crazy strong + tough and always has some flex left after fully cured so you dont need to worry about the seal becoming cracked/compromised if the joint were to take a hard hit. Only issue is that the stuff is crazy permanent so difficult to undo if you ever want to remove the esc.
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Hobbyking Turnigy 150A. I got already a fly color 150A on my existing build and it works fine.
Cool im using the same. I actually have both hobbyking and flycolor versions. They hit their thermal limit pretty quickly if you use it for much more than like 15 or 20 seconds at full throttle. Having some additional cooling would be great.
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yes, I agree with the thermal limit. I had a thermometer measuring and it seems around 65/70°C
likewise, can only do little bursts. Not that big a concern using it in surf, as you are only using it to get into wave. But we have been trying for flat water pump training: a buddy is better than me and get do a 5 second burst, up onto foil, flat water pump for 40-50 seconds. I was doing too long a burst to get up, it’ll overheat. My buddy is going to experiment with the heat sink that others have commented on above.
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moving on my second build. I’ve reduced the size of the heat dissipator knowing that I have no other choice than to put it up. I’ve also dig two holes, one for the ESC bottom (it’s plastic but still this will cool the ESC because of the water going below).
I will secure it with 3M 5200.
So far, so good.
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I was tempted to install the esc that way but the plastic on the bottom side discouraged me.
Keep us updated on how it works when its ready ( how long you can keep it running before hitting thermal throttling)
yes, I also hesitated but that’s the only way to fit it. I believe that having a good part of the ESC outside will help a lot. When riding, I often put some water on my board and with the ESC below it will help to cool down faster. My plan is to get around 2 to 4mm depth outside/below the box as I will not be able to put 3M velcro tape in that area.
One of the big win with that box is that I will be able to use my 6S 8AH Graphene lipos (got 4 of them) and also a 6S4P 40T pack. So ultimately, that’s plenty of joy in the water!
@okp lol I have a lot of experience with walks of shames up and down the beach with a heavy board/foil :). Maybe this helps - I eventually I bought myself one of these air-plane shoulder pillows (with nice filling that fits the purpose - I think it’s some grain or pellets in it not just foam). No prob to surf with them and when carrying the board on your shoulder it’s a whole new world! 
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