Situation: I have a 12s2p battery made from LG HB6 cells, which I thought would be perfect for my needs, because then I could safely draw 60A continuously from them. (The cells are low-capacity high power draw ) However, the cells are rated for a maximum charge rate of 4A each, meaning my pack can safely only support 8A regenerative breaking. Now, unfortunately I don’t have a bluetooth module, so am not fully certain this is the limit I’m reaching, but it sure feels like it! Actually stopping at stop signs is nearly impossible, and the breaking distance is way too long for me to feel safe cruising in traffic.
So: Have I messed up with my battery choice? Is this charge rate limit just a guideline? How does breaking work for people that don’t have an integrated BMS with charging support? Perhaps there’s large enough capacitor or something that I should add in series to the battery to take this charge? (And that could reduce voltage sag, but my battery is powerful as is tbh )
I have dual DIYelectric 6355 190KV sensored motors running in FOC mode
Motor min is -49A, motor max is 49A (They’re 2500W, so I divided that with 50.4V)
you should get a good breaking with your actual settings
already.
You can set up your bat min to about -16 (so -8, -8)
it´s not a problem as long as you don´t go down a 3km hill while breaking all the time.
As in: it doesn’t matter if the motor minimum is set to -49A, if the battery minimum is set to -4A, then it will only break so much that 4A get generated from the motor and put back into the battery.
no that´s not right.
only 4A will go back to your battery as reg. breaking and charge up the battery.
but your motor produce heat and magnatic fields which result in the breakforce
Ah, so the heat gets directly dissipated in the motor! Interesting! I guess my throttle curve might not be strong enough in that case… (Unless someone can come up with a better explanation)
You can increase your gear ratio for more braking power without adding more amps to your battery!! With a slight hit to your top speed being the only downside.
While your max battery charge rate on the data sheet is 4amps, that is for a full charge from empty not a very quick bust of power you get stopping at a traffic light. Most of the users here would prefer to shorten there battery life then have a serious crash so will run more than the data sheet suggests. So long as the batteries do not get hot during charge there should not be much of an issue. Except for slightly shorter life span, but I have never seen any data on this.
Was thinking the same about life-span, thanks! I am running 14:36 already on 80mm wheels, so I don’t think I’d want to sacrifice my top speed any more than it already is (A bit off topic:) I have Orangutang wheels unfortunately, so upgrading to something bigger means buying new pulleys as well (they really need to release larger wheels)
Hold on, but if I understand correctly that all the energy that cannot be used to charge up the battery gets dissipated into heat anyway, then why even raise the charging limit? Just for more juice on the go? (I also read here on the forums that anything more than 0.1 seconds already counts as "continuous charge/discharge, so is it really safe?)
If your motors can make 20amps under braking, and your vesc setting is -20a, then the vesc will try to put all of that into the battery. The vesc does not bleed of excess energy as heat intentionally. Although your battery might get annoyed and hot if you charge it too high for too long. But for 4 seconds your slowing down, double the data sheet of 8 amps should be fine.
Yeah, its pretty much low as you can go with 80mm wheels. How many mm between the ground and your belts on the wheel pulley? Also normally I don’t recommend below 15t motor pulley, which motor mounts you using?
Battery minus is basically your braking power, motor minus is basically maximum braking current so if you going full speed you will not have motor max as voltage will be the same as input so applying power formula you will have max braking power your battery minus. Everything else will go into heat as you shortening mosfets which means they connect phases and work as resistors so they also will produce some heat from their resistance, wires will heat up and motor coils too as you basically shortening you phase wires but that will not be as much braking force as you would drain that energy into battery.
EDIT: If you have -20 At battery and -50A at motor it will be like if at half speed your motor voltage is 25V so (20A * 50V = 1000W your maximum power capacity) so at half speed you will be able to brake with (1000W/25V = 40A)
Yeah, clearance with 85mm is not great at all I usually step off and lift my board when going down / up a ledge. Although these wheels (Orangutang Caguamas) are amazing for a non-electric board (really great for going up/down ledges), at 40+ kmph the bump you feel with these 80A wheels is very unpleasant and worrying. Will try upgrading to the softer versions as they become available.
I’m using TB mounts, and TB motor pulleys. Belt hasn’t slipped so far, and I don’t use any idlers, so I think it’s good.
Very interesting; I guess that explains why the breaks get stronger the slower I’m going, i.e. the breaking curve is very smooth, despite not having tinkered with it at all yet.
) However, the cells are rated for a maximum charge rate of 4A each, meaning my pack can safely only support 8A regenerative breaking. Now, unfortunately I don’t have a bluetooth module, so am not fully certain this is the limit I’m reaching, but it sure feels like it! Actually stopping at stop signs is nearly impossible, and the breaking distance is way too long for me to feel safe cruising in traffic.
)
(they really need to release larger wheels)