I’m getting 5 brand new factory fresh Gen 4 Leaf batteries for my 2002 e824. Each module is configured as 2P4S so 14.8V and 110AHr capacity. 5 * 14.8V = 74V nominal and ~82V full charge(5 * 16.4V).
For the BMS there is a guy who makes a wireless module which mounts on each battery module and I will post more on that too.
I don’t expect this to make my cart a rocket since it’s in the same ballpark voltage wise but expect to be able to boost the controller for a sustained 25 MPH up small hills and 30 MPH on flat. Given the much higher and flatter discharge curve, it should feel as peppy as it does now right after a charge and during the first mile or two.
One thing I was thinking about was keeping one 12V battery and add a simple 12V charger and get rid of the 12V DC-DC step down. This should keep a little bit of weight in the back and allow for a bit more 12V device power. Actually, a lot more 12V device power.
Depending how much 12v power you need look into the portable jump pack/back up lithium batteries. I got one to run phone/tablet chargers and Bluetooth amp for the 4 speaker audio system to avoid ground loop noise. It has a switchable 9/12/18v dc out Port that I wired into th amp.
Works great plenty light and last more then long enough.
@Inwo I have a question about BMS systems and the charger. The BMS system I’m going to be working with uses a CAN bus to communicate with the battery charger to regulate the charge and balancing. The battery modules have 3A shunt capabilities to bleed energy off full cells but to optimize charging the control system is designed to not only provide battery module status, SoC, temp, etc but also talk to the charger too.
How are the BMS systems you’ve worked with dealing with the charger and its output voltage and power?
On my RC batteries, the charger has two outputs and does main charging via the high current cables attached across the entire battery pack and then the balance wires to each cell of the pack is used in balance mode to balance the cells and bring them all up to full state.
I don’t yet have the documentation on this system so it could be the 5 pin connector on the end of the battery module provides balance power.
The bms that i use are much simpler. They can control charger directly…
The Bluetooth bms can carry and switch 300amps. All on a single board. One wire from each cell to the bms.
3amp balance current is nice, but way over kill. A few hundred milliamps runs cooler and keeps battery balanced fine. All with small balance wires.
Can seems to overcomplicate a small 20s system.
Bms boards may be low cost, but then you need a can charger, can control relays, and can display if you want to monitor from dash.
I agree, the CAN stuff is overkill for the little GEM implementation and is designed for vehicular rapid charge systems and is made by a guy who built an electric car over 15 years ago which blew away most all contenders on the drag strip. He’s adding features to widen the market for the BMS so I’m hoping to have input which helps it more easily fit our needs.
One cool feature is how the battery module mounts on the battery cell and can report status even when on the shelf somewhere. The module can be commanded to bleed the battery down to storage levels and with wireless monitoring could provide a warning as to when recharging is needed. A no-wire BMS sounds good to me unless there’s way too much overhead dealing with CAN based charge control.
As for the remote display, I know there’s an Android app which runs on a tablet with a CAN to USB adapter. But I’m just getting started so more accurate info to come.
The BMS battery boards arrived today @Inwo, thanks. I did look high and low for signs of the boards on google but found nothing. I’m guessing they might be custom for a custom pack so never in public view.
Will see if I can figure out what they do besides start shunting at 4.9V.
If it helps, they connect across a group of 3.2v cells.
First guess was that they require more than 2.5v supply. But it makes more sense to be powered by the daisy chained communication string.
The shunting may just be power supply protection. I didn’t see shunt resistors.
My thought is active balancing between the three cells connected to each board. Seems to be a transformer for dc to dc boost.
The tripping or shunting level indicated a single cell( 1S ) per module. I don’t believe the jumpers between cell modules are for communication since they connect directly to the lower and upper battery terminals. Buy my thought was that they would have active balancing capabilities even if we didn’t know what/how the communications on the 4pin RP1 connector worked.
The Gen 4 Leaf module is 4S so my next test is to user jumper wires and connect this across all 4 cells and feed a voltage across the string and see what each cell voltage does.
So far I have validated the wireless BMS battery modules start shunting(balancing) at 4.1V and have a max current shunting spec of 3A.
I now have to figure out if the Zivan NG1, when mod’ed for Lithium charging will be below 3A when the battery cells are at 4.0V. 20S * 4.0V = 80V or if there is a way for the BMS control module to signal the charger for balance voltage(82V) and max balance current(<3A).
Does anyone know anything about the firmware mod of the Zivan NG1 for Lithium charging?
That was the plan. But as I’ve learned from researching and owning a 2017 Nissan Leaf, we don’t want to fully charge the batteries unless we intend to use it immediately and partial charging will prolong the battery life. There didn’t seem to be much capacity above 4.0V anyways.
I don’t follow your reasoning to limit finish current. With a bms, I run full rate until a cell reaches hvc, then bms shuts down charger. Most of us charge at such a low rate,10-30a, there is no need to taper.
If battery doesn’t saturate, turn it up a 10th of a volt.
3a balance is nice if batteries are failing, but way overkill for such a small bank. Lot oh heat to dump.
My 280ma balance keeps 100ah balanced just fine.
Ideal method is active energy transfer. It can run efficiently 24-7 with no setup required. @LithiumGods is testing one now…
All IMHO
The wireless modules which sit on each battery( 4S module ) sends data to the BMS controller for each module.
What each battery module also does is the top balancing by shunting voltage on the cells which reach the 4.1V level first so that the other cells can slowly reach that level also. I don’t know what the charger( Zivan ?) will do with the charge current up at around the 4.0v/cell charge level( 80.0V ). If it is trickling current at 500mA or so then this is no big deal as the battery module shunts can handle up to 3A. I don’t need the current to be at 3A when it’s topping off but because I don’t know what a Zivan Charger will want to do, I’m looking for ways to control it.
I think you said your BMS is part of the charger or something like that in that it handles all this but the wireless system I’m working with doesn’t do that. The cool part is, you just put the batteries in series, put a wireless module on each battery module and that’s it. Could be that with the Zivan or any other dumb charger for Lithium batteries set to 82.0V( 4.1V * 20s ) will be dropping the charge current down to less than 1A up around 4.0/80V and everything is golden. I just don’t know this yet and I don’t want to burn up a battery module board nor over charge any of my cells.
Before I got into this, all the lithim charging systems I’ve seen and/or played with used wires connected across each cell in order to do balancing. Some chargers required it, some chargers would give you an option to do only the balance charging( ie low current provided individually across wires on each cell ).
This setup I’m working with now is unique in that there are no wires on each battery cell and instead, there is a wireless module for each 4S cells( battery Gen 4 Nissan module ) and in order to do balancing, the module has firmware which not only sends wireless health stats to a controller/display, it also has a settable top voltage setting(currently 4.1V) and to balance charge that module’s firmware will turn on a 3A capable shunt to keep that cell from charging any further while the other cells get to the 4.1V level.
If I have a way to know a “dumb” charger will do it’s end charge at < 1A then all I have to do is connect it across the whole battery pack and turn the charger on.
What I’m saying is that battery can still balance when charging at 20a and shunting 3 amps.
It need not do it all in one shot. Over time shunting the high cells will keep them in line. Even at high charge rates.
If shunt starts at 4.1 you will need to set bms hvc above 4.1. Else it will never balance.
By setting hvc to say, 4.15. balance will continue after hvc drops charge rate to zero.
Charger can be charging at 20a till finish.
I don’t see how it would be safe or advised to be running 20A through the series batteries while one of the batteries has reached it’s “full” charge of 4.1V and only shunt 3A. Wouldn’t 17A continue through the cell and therefore continue charging it? Remember, this is a setup where there is ONLY a battery charger POS and NEG connection to the whole battery pack and there fore, any current going through any one battery is also going through all batteries since they are all in series.
My take is that putting 20A through when a battery is full( 4.1V ) will blow up the shunt as it tries to shunt all the current around the battery to stop it from charging more than 4.1V.
Maybe I am. I assumed it to be a real bms. But no, you can shunt 3a while charging 20a.
If you are trying to limit cell voltage by shunting current, you may well be disappointed. All a shunt does is put a resistor across the cell. Cell will continue charging even at 1amp charge current.
It may be possible with an extremely smart bms to load the cell in some other manner. Pwm or such. I’ve never seen it done.
A bms will stop the charging current when any cell reaches the set point. Ideally restart charge when high cells are pulled down.
