Andrew A few issues with your design You need to have longitudinal flex in the battery pack for deck curvature - each 2x3 6 cell pack needs to have flexibility to an adjacent 2x3 6 cell pack- To achieve this you need either a plastic spacer ( as per Nick's solution) or some rubber foam ( approx. 5-10mm thick) . This spacer or foam also provides insulation between the cell packs and hence has no individual cell in direct contact with another cell at a different voltage. The flexible braid then crosses the spacer or foam to provide flexibility in the series connection. You do not want hard connected nickel strip along the inter-cell series connections as it could come loose a result of the whole pack under flex mechanical forces from the deck. Your row off-set pack design has 16 points of failure - cell to cell short due to the cell insulation bareing from movement and causing a dead short. Some people add heat shrink to outside cells - but even this could cause problems in time. {} Far better to accept that the cell packs will be directly in-line and then provide foam between packs for flexibility and to ensure that no outside cell is in direct physical connection with an adjacent pack outside cell. {}
Ah I should have mentioned the deck I have has zero flex in it (a downhill board, super stiff). So no flex in the pack. Otherwise would definitely be going the spacers design.
no worries - flex or no flex you still need extra good insulation from adjacent cells with a voltage difference between the cell outer metal sheaths. Vibration is the other factor to consider! Cheers
You can power up vescs and have a play with them from any power supply greater than 10V . the racestar motors draw about 1A no load . or if you want - you can borrow my bench setup with a 10S 1P pack and the racestar 140kv motors fixed to some plywood!
Hi mate, I think I'll take you up on that test rig, looks like good fun. Hey on the '2' rows of cells... this is what I'm thinking - had a look at yours but couldn't see how you'd joined the power cables.. http://www.alternative-4.com/DIY/spud_freeboard_79.jpg <- you'd have '2' of these.. could be joined by this HXT 5.5MM Bullet Parallel LiPo Connector with 10AWG Cable | eBay ? (page w/ all images from endless sphere for reference) Endless-sphere.com • View topic - Carbon Jet Spud / Freebord Bindings / 10S3P
Andrew - the +ve and -ve power cables are just soldered onto the nickel strips ( with multiple connection points)
Ignoring the fuzzy photo and the iron in the background (!)... Correct size deck screws and motor mount screws arrived. Will orientate the motors with cable to the trucks, didn't want to bend the cables over unnecessarily but have since seen a few evolve's where they're jammed right on the mount. {}
Found this a few weeks too late Roger VESC Sensor Wires Basically that wire you passed on today but with the female connection for the motors? Also wondering if this fuel gauge would need to be stepped down in voltage, or could be soldered straight into the anti-spark 'in' connectors? LY6 8-63V Lithium Battery Capacity Tester 12V/24v/36v/48v Lead-acid Indicator | eBay
Loop Key, sort of an 'immobiliser' for the board? This schematic shows using the BMS for discharge but I like what you were talking about by bypassing it and using the vescs instead. Post-Script: if you only used the vesc to monitor output, would that be total pack? (ie: BMS would monitor individual cell discharge/be safer?) {}
Andrew - looking good- VESCs arrived yet? A) Need to investigate how your BMS handles current flowing back through P- terminal (could be up to 30-40A during heavy braking) to see if no ill effects. Under braking - you don't want the BMS tripping out and hence causing VESCs to trip out on input overvoltage and then you loose all brakes just when you need them the most. ( This is the prime safety reason why I am not using a BMS in the board) B) Have you gone back to 4P for battery? C) The 6 pin JST plugs came with 6 pin headers which can be used for Hall effect 5 pin plugs ( I can give you a few pin headers next ride) D) Your comment re BMS monitoring each cell pack during discharge is valid - but I don't see this as a reason to change my plans. Not having BMS inside enclosure would be a good thing and I have not seen any discharge cell voltage drift with my battery. E) being a two wire device - the fuel gauge indicator can be wired as per your diagram - directly across the 36V . Your voltmeter looks like a 3 wire device with a 12V power supply . F) I don't think you need all the bullet connectors and XT90s on the dc circuits. They are quite large and could be a future source of trouble from vibration. Better to solder everything where possible. I will be using Deans polarised plug/sockets (same as Evolve main battery plugs) on the VESC DC cables and the MD30 on motor leads. The deans plugs are quite small and can handle the current OK. G) where is your horn and dog siren?- I can give you my remote control relay board after I have changed over to VESCs and smart remote . as the smart remote will have light and horn switch inbuilt. H) Need to watch the max input rating of 42V to 12V converter. I tried one with 40V rated input and thought it would be OK on 42V - but blew it up after about 5 minutes on 42V ( with flames and smoke) - Get one with a least 50V rated input to be sure. I) Are you making the XT90 loop key or buying it. I will probably incorporate one as well as a backup to anti-spark switch. J) When your cells arrive - suggest you do an individual cell charge/discharge test prior to making cell packs. Cheers
{} Andrew Bluetooth UART module from ebay details on photo but any HM10 module will be fine I will make up a wiring diagram for you Cheers
Sorted, thanks Roger have snapped one up. Turns out isopropyl alcohol gets rid of hot glue, so have managed to dismantle the 3x1 packs and can fully charge each individually. Will then discharge test. Thanks again for the help. Watched a video on soldering onto deans connectors too, after tinning the wire you can whallop them flat for a better contact on the solder.
Just make sure you monitor the volts/current and dont discharge below 3V or you could permanently damage the cell chemistry. If you use the 1 ohm resistor (2x2 in parellell) current will be about 4A so individual cell discharge test should take approx 40 minutes from 4.2V to 3.0V Cheers
So far so good on charge voltage and mAh, will discharge a few of them at random once they're all charged up. Got an alarm at midnight to swap the cells in the charger! One box to go...
