[sunworksco]

Not true.Regen can be working to maximum levels with ev traveling downhill with battery levels already near full charge and the balancer will keep batteries going to higher than recommended voltage levels.If you talk to RC hobbyists about lipo battery balancers,they will tell you it is mandatory or batteries will self-destruct.Go to www.rcgroups.com and read all you can about lipo batteries and balancers and misuse of batteries/chargers.This is the small world of evs and mirrors the full scale evs.Look at Novak brushless motors/ESC controllers.these are dc but on the power graph are really miniature ac motors with sensored controllers and brake regeneration.

[dimitri]

Originally Posted by sunworksco

Not true.Regen can be working to maximum levels with ev traveling downhill with battery levels already near full charge and the balancer will keep batteries going to higher than recommended voltage levels.If you talk to RC hobbyists about lipo battery balancers,they will tell you it is mandatory or batteries will self-destruct.Go to www.rcgroups.com and read all you can about lipo batteries and balancers and misuse of batteries/chargers.This is the small world of evs and mirrors the full scale evs.Look at Novak brushless motors/ESC controllers.these are dc but on the power graph are really miniature ac motors with sensored controllers and brake regeneration.

Dude, we weren't talking about regen, we were talking about gas powered genset. And enough with RC advertisment already, it has similar technologies but specific applications and power levels involved in real EV is way too different compared to RC world. Sure the knowledge helps, but there aren't any EV controllers or chargers or BMS that have standard connectors and signals like in RC world, so it doesn't really apply here. Maybe one day in a distant future EV market will standardize on connections like RC market, but those days aren't here yet. It doesn't help to tell people not to get their shorts in a bunch when they spent 10K on battery and naturally want to protect it.

And even with regen as you said, overcharge is virtually impossible. Only if you charge to full at the top of the mountain and then start rolling down, then you maybe able to overcharge, but in any other situation you will always spend more energy to get up to speed than you will ever hope to recover during regen.

[sunworksco]

Originally Posted by dimitri

Dude, we weren't talking about regen, we were talking about gas powered genset. And enough with RC advertisment already, it has similar technologies but specific applications and power levels involved in real EV is way too different compared to RC world. Sure the knowledge helps, but there aren't any EV controllers or chargers or BMS that have standard connectors and signals like in RC world, so it doesn't really apply here. Maybe one day in a distant future EV market will standardize on connections like RC market, but those days aren't here yet. It doesn't help to tell people not to get their shorts in a bunch when they spent 10K on battery and naturally want to protect it.

And even with regen as you said, overcharge is virtually impossible. Only if you charge to full at the top of the mountain and then start rolling down, then you maybe able to overcharge, but in any other situation you will always spend more energy to get up to speed than you will ever hope to recover during regen.

I am merely providing the link to offer to forum members here to do some research.Go visit an rc forum and there is more science there about motors and lipo batteries than here.I have been nothing except helpful in every way of design and building evs. How dare you say that I am advertising. I am in a completely different business. I have never directed anyone here to my solar industry business? I have never done business with any forum member here and find it very irritating how closed minded this forum can be at times.I take your comment as disrespectful and your comments sounding as if this is your own personal membership club and can be sensored at will by you!

[sunworksco]

P.S.
I see you do have weblinks on your forum comment page!

[sunworksco]

"Shorts in a bunch" was intended as a light-hearted joke and pun but I can see that I was laboring on a misapprehension the this forum membership possesed any humorous attributes.

[sunworksco]

Originally Posted by sunworksco

I am merely providing the link to offer to forum members here to do some research.Go visit an rc forum and there is more science there about motors and lipo batteries than here.I have been nothing except helpful in every way of design and building evs. How dare you say that I am advertising. I am in a completely different business. I have never directed anyone here to my solar industry business? I have never done business with any forum member here and find it very irritating how closed minded this forum can be at times.I take your comment as disrespectful and your comments sounding as if this is your own personal membership club and can be sensored at will by you!

Although BLDC motors are practically identical to permanent magnet AC motors, the controller implementation is what makes them DC. While AC motors feed sinusoidal current simultaneously to each of the legs (with an equal phase distribution), DC controllers only approximate this by feeding full positive and negative current to two of the legs at a time. The major advantage of this is that both the logic controllers and battery power sources operate on DC, such as in computers and electric cars. In addition, the approximated sine wave leaves one leg undriven at all times, allowing for back-EMF-based sensorless feedback.
Vector drives are DC controllers that take the extra step of converting back to AC for the motor. The DC-to-AC conversion circuitry is usually expensive and less efficient, but they have the advantage of being able to run smoothly at very low speeds or completely stop in a position not directly aligned with a pole. Motors used with a vector drive are typically called AC motors

[JRP3]

I'm not sure if RC sized cells are comparable to EV sized cells. It's simply going to take a lot more to get a 100ah or larger cell to over volt, and as mentioned unless you are starting fully charged at the top of a long hill it will not be an issue. If you are routinely starting off at the top of a large hill with a full charge the smart thing to do would be to turn down the charger a little bit to allow room in the cells to take the recharge.
People have been running successfully without a BMS on the newer cells. Time will tell if there is a long term difference, but to say a sophisticated cell level BMS is a necessity seems to be a stretch. If you charge a TS type cell to 3.6 volts and never go below 2.7 volts I doubt you'll ever come close to damaging a cell. Monitor two halves of the pack to check for imbalances, if one shows up check that out. This is what Jack Rickard has been doing and he's had no cell failures yet, I think he has about 5000 miles on his pack.
As to the sense of humor on the forum, I've found plenty of funny people here

[bblocher]

From my personal experience, the monitoring the two halves of the pack idea will definately not work.

I've done some experiments by manually bypassing my BMS to see how quickly one cell could rise on a balanced pack before the charger will cutback as the other cells caught up.

There are two ways to test this, one way makes it look like it works and that's if the pack is already charged but has had been sitting for awhile. The voltages increase close to each other and the charger ramps down amps until it finishes.

If I do this test after a drive it will fail every time. As soon as a cell reaches 3.8v, it will continue to climb to >4.2v in seconds if not controlled. There simply isn't enough delay as the voltage curve ramps up too quickly towards the end of charge cycle. I've seen my charger still outputing 30amps until the first cell hits high voltage forcing it to ramp down.

I know there is a lot of talk out there about not needing a BMS, and I disagree completely. Please do some closely monitored tests on your side and you'll see what I mean (again make sure you're discharging the pack significantly between tests, 50% SOC or so).

[sunworksco]

Originally Posted by JRP3

I'm not sure if RC sized cells are comparable to EV sized cells. It's simply going to take a lot more to get a 100ah or larger cell to over volt, and as mentioned unless you are starting fully charged at the top of a long hill it will not be an issue. If you are routinely starting off at the top of a large hill with a full charge the smart thing to do would be to turn down the charger a little bit to allow room in the cells to take the recharge.
People have been running successfully without a BMS on the newer cells. Time will tell if there is a long term difference, but to say a sophisticated cell level BMS is a necessity seems to be a stretch. If you charge a TS type cell to 3.6 volts and never go below 2.7 volts I doubt you'll ever come close to damaging a cell. Monitor two halves of the pack to check for imbalances, if one shows up check that out. This is what Jack Rickard has been doing and he's had no cell failures yet, I think he has about 5000 miles on his pack.
As to the sense of humor on the forum, I've found plenty of funny people here

Lithium iron phosphate batteries are used in rc rock crawlers,submarines and other various models.It is not recommended to use these or any other lipo batteries without balancers.

[JRP3]

Originally Posted by bblocher

If I do this test after a drive it will fail every time. As soon as a cell reaches 3.8v, it will continue to climb to >4.2v in seconds if not controlled. There simply isn't enough delay as the voltage curve ramps up too quickly towards the end of charge cycle. I've seen my charger still outputing 30amps until the first cell hits high voltage forcing it to ramp down.

The difference may be how the charger works. What charger are you using? Jack is using a Brusa which as I understand it can be set up to have one charge stage up to a certain point, then stop charging for a period of time, then come back on with a low amp charge, and do this a number of times. He claims to have not overvolted a single cell. Along with not charging above 3.6 volts this may be the key to doing a pack without BMS.