Lead acid to lithium conversion

[Ribfeast]

Hi all,

I have a Toro Workman MDE, which we use for feeding up the horses and getting around the farm. However the 48V lead acid battery pack is nearly shagged.
The previous owner didn't have the Lister charger for it, and had fitted a Delta-Q 650W charger, which is set correctly for the 8 Trojan T105 6V batteries. The charger has a lithium mode but I'm not too sure if I'd trust it.
I believe it has a Sevcon controller, and the motor would probably top out at around 200-300A if I was going flat out up a hill.

We are on the fence about selling it to try and recoup our purchase price (approx $9k), or double down and convert to lithium.
I've replaced 4 of the 8 batteries however these aren't coping too well with the surrounding dying batteries and I'm sick of adding distilled water twice a week.

I've had quotes for around $4-5k for just a battery pack and BMS but trying to get away with this cheaper if at all possible?
Was thinking of chucking in a dozen or so CALB CA100 cells, or a few Westart NCM cells. That brings the cost to $2500 in batteries alone, is there any BMS and balancer systems out there that would be affordable to go along with this? And a suitable charger?
https://www.ev-power.com.au/product/wes ... -7v-cells/

Thanks for any help

[Richo]

For compatibility LiFePO4 is the better option
Do you actually flatten it in one day/trip?

The 12V packs have no BMS.

https://www.evworks.com.au/winston-batt ... l-12v-90ah

But the full pack would need to be about 48V 200Ah to be eqv.
So $4-5k does sound about right.

Obviously if you don't use the whole pack in a day get half...

[Ribfeast]

I was hoping to go for 48V 100Ah. So you reckon LFP instead of NMC?
Trojan T105's are 225Ah but you only get 50% capacity.

The cart only gets driven for two 15 minute stints per day and then spends 4 hours on charge (approx) after each stint. It's pretty much undriveable after 15 minutes, just cuts out if you give it more than half throttle, and individual battery voltages for some of the T105s drop below 2V. Missus wants it gone, but I reckon I'd never be able to sell it due to lack of buyers looking for this type of vehicle, hence I'm leaning towards converting it. It's nice and quiet which works well with horses.

We have a large solar array, all it needs to do is an evening feedup trip, morning feedup, and then go on charge, so peak current capability is of more interest than bulk range. Being able to charge it once a week would be a big bonus though.

[jonescg]

If you go with LFP you won't need a new charger.

[Ribfeast]

https://delta-q.com/product/ic650-indus ... y-charger/

"Optional CAN bus communication enables a link between the IC650 and other components. This can provide for safe lithium-ion battery charging, and machine diagnostics and servicing information. IC Series chargers store charge cycle data, which is accessible using their built-in USB host port. The port can also support software and charge profile updates."
https://delta-q.com/wp-content/uploads/ ... Latest.pdf

So apparently the charger can link to a BMS. How many 3.2V cells should I get? 15 to make exactly 48V, or 16 cells to make 51.2V which is closer to what the lead acid pack would be?
Is there any BMS out there with CAN bus ability I can link to this charger, that can handle 16 cells?

Was thinking this control unit:
https://evparts.com.au/ev-power-bms/bms ... n-evs.html
Would I need to connect it to the kart's existing contactor? Not sure if it can talk to the charger though (does it need to?)
Has a nice OLED display to show charge level which is perfect.

These for each battery:
https://evparts.com.au/ev-power-bms/bms ... bm180.html

These batteries:
https://www.ev-power.com.au/product/gbs ... -2v-cells/ LFMP100AH
Or 4 of these @ $641+GST ea:
BAT-LFMP12V100AH (4 cells with interconnects in a pack, with no BMS)
Or 4 of these @ $780+ GST ea:
EVP12V100AH (4 cells with BMS included, with interconnects, in a pack)

Then I'll fabricate a box with sufficient compression/structural stability to keep the pack(s) together as I bump around the farm.

Would there be anything else I need? Something to shut off charge to the battery to prevent overcharge or overdischarge? latching relay perhaps?

Thanks for all your help

[Richo]

Sorry if it is borderline why bother with BMS or CAN?
I'd keep everything the same/simple and go with a 12V block with the internal BMS.

How many 3.2V cells should I get? 15 to make exactly 48V, or 16 cells to make 51.2V which is closer to what the lead acid pack would be?

15cells x 3.2V = 48V nom
15cells x 3.65V = 54.75V chg -> or 13.6V per "12V" block.

How many cells really depends on the terminating voltage of the charger.
Presumably the delta charger is configurable.

IF the charger was set to 14.2V per battery this is 56.8V.
So 56.8V / 3.65V = 16 cells

The Delta charger seems to have quite a high maximum DC output.
So your maximum cell count will probably be limited to the controller max DC voltage.

[Richo]

I believe it has a Sevcon controller, and the motor would probably top out at around 200-300A if I was going flat out up a hill.

The Trojans don't have a CCA rating and the max output claimed is <250A.
So I'd suspect that they really were never up to the job anyway.

The 48V sevcon controllers typically have a max input of 69V.
The Deta Q Charger is 72V.
So the controller IS the limiting factor.

69V/3.65V = 18 cells MAX
Once again it will now depend on the upper(MAX) and lower(MIN) voltage settings in the controller which may be difficult to change without the interface box which I believe is not cheap.
So the actual cells you choose will best be determined by those settings so you don't have to change them.

As you say IF you were only using half the Trojan's rating 225Ah 48V = 10800Wh
then this is ~5400Wh.
BUT after 15min it cuts out presumably due to voltage loss under load ?!?
This is an average 5400/15min = 21600W = 21.6kW or 450A continuous at 48V!
So I think there are issues with how much you really actually use if the battery system was in perfect condition.

In any case I'd still think the 90-100Ah would be fine.
AND I'd still think the 12V 90Ah would be good without adding BMS or CAN.

[Ribfeast]

I put the current clamp meter on the lead acid battery string last night during feedup, when flooring it I get in the low 200's, maybe 220A.
I then measured voltage during feedup this morning, nominal no-load voltage when starting feedup was 52V, but this sagged as low as 33V under load towards the end of feedup and the cart would cut out. Some individual 6V batteries would measure -1.8V also which can't be good (pack is a mix of 4 new and 4 old batteries).
The main concern I have is the regenerative braking when you let off the accelerator, whether this would spike and overvoltage the Lithium pack? Or whether the pack would have enough internal resistance to stop too much voltage rise? I could see a spike to around 56V when I let off the accelerator sharply when going down a hill. A needle-type voltmeter would be the way to go to pick the spike up better though (or a scope).
Not sure of the best way to protect against this, a Zener diode would likely explode, maybe a supercap? Or am I being paranoid

I'm not too worried about going beyond 15 or 16 cells, don't want to stress the controller or blow out the project costs.
Any thoughts on the Batrium BMS? Something like this:
https://www.batrium.com/collections/sta ... tmon2-500a
It also can talk to the Delta-Q charger which is appealing.

I was keen on the EVPower BMS units however they seem to use Voltage-Based shunting which is not recommended below, hence the interest in Batrium:
http://nordkyndesign.com/protection-and ... ery-banks/

[antiscab]

What's the max amps of Regen? That would be more important. Also, how long are you likely to be doing hard Regen?

[brendon_m]

Unless you start at the top of a hill with a full charge, regen shouldn't be an issue because the pack should be down enough to be able to absorb it

[Ribfeast]

I guess if I let off the brakes slowly it should be OK, most of the driving is flat(ish) but there is one big hill at the start of the run. Worst case I do it in reverse order and polish off that hill last.
Any thoughts on the Batrium?

[Ribfeast]

I believe it has a Sevcon controller, and the motor would probably top out at around 200-300A if I was going flat out up a hill.

The Trojans don't have a CCA rating and the max output claimed is <250A.
So I'd suspect that they really were never up to the job anyway.

The 48V sevcon controllers typically have a max input of 69V.
The Deta Q Charger is 72V.
So the controller IS the limiting factor.

69V/3.65V = 18 cells MAX
Once again it will now depend on the upper(MAX) and lower(MIN) voltage settings in the controller which may be difficult to change without the interface box which I believe is not cheap.
So the actual cells you choose will best be determined by those settings so you don't have to change them.

As you say IF you were only using half the Trojan's rating 225Ah 48V = 10800Wh
then this is ~5400Wh.
BUT after 15min it cuts out presumably due to voltage loss under load ?!?
This is an average 5400/15min = 21600W = 21.6kW or 450A continuous at 48V!
So I think there are issues with how much you really actually use if the battery system was in perfect condition.

In any case I'd still think the 90-100Ah would be fine.
AND I'd still think the 12V 90Ah would be good without adding BMS or CAN.

Yeah I'd say there is an inherent issue with the current batteries, as I'm pulling nowhere near that current. Most of the time during feedup it is stopped as I pull out hay and buckets of feed.
Where can I get 4 of those 12V 100Ah batteries affordably? How good is the internal BMS? And is it smart enough to shut off if the voltage gets too high or low? And would they put out 200A or more?

Would 4 of these suit? https://www.amptron.com.au/12v-100ah-li ... ttery.html

[antiscab]

Generally 12v lithium batteries with internal bms can't be put in series, unless rated to do so. The issue is they tend to use semiconductor based switching devices, which don't have much voltage headroom.

[Ribfeast]

Ahh I see, might contact the Amptron people to confirm whether theirs can be connected that way safely. So many things to consider!

[brendon_m]

You could get a pre built 48v lithium pack, like what's used on the electric pushbikes, and put a couple in parallel to get the current/capacity required.
There maybe other

[Richo]

Actually the ev works 12V90Ah doesn't have internal BMS.
They are matched cells.
I don't see why these can't be serialised...
How about a simple Zener+resistor overvoltage shunt?
The controller should do the low voltage shutdown.
A simple voltage gauge on each cell just to proove they are not out of whack.
And if they were you could put the car charger on that one.
All of which is still cheaper than a BMS.

They are rated for 3C = 270A continuous.
20min run time @ 270A.

[Richo]

Generally 12v lithium batteries with internal bms can't be put in series, unless rated to do so. The issue is they tend to use semiconductor based switching devices, which don't have much voltage headroom.

True.
But they would be referenced to the pack it's on.
The issue will be when the BMS detects a fault and goes open which would then see the more than its voltage rating across it.
Probably not such a great thing after all.
However a phat diode (300A) could be used as a bypass which would work for running.
Charging would be a different story

[Richo]

$8,500 for one with new batteries.
https://www.truckworld.com.au/search/a~ ... =v~1-z~15-

The specs say it had a 500A controller.
Do you know what model of controller it has now?

[Ribfeast]

Yeah $8500 with new batteries and we paid $9k for one with stuffed batteries, and a lot of these have been sale for some time. Rather get some value out of what we have purchased as I'll never be able to make the $9k back.

They come with a fuse that is rated for 355A continuous from the factory. Workshop manual says it is a Millipak Sevcon controller, so I am guessing it is this one or similar:
https://www.electricmotorsport.com/sevc ... -500a.html

Another concern is whether a bank of CALB CA100 cells would experience too much voltage sag under load and trip the undervoltage cutout on the BMS.
Is there any kind of graphs out there that show pack voltage under various current draws, or am I dreaming? I've heard some brands have sag issues. Trying to avoid having to go to the CA180 cells.

I have a few dozen spare 12V 9Ah SLA batteries I can run a BMS or cutout relay from if required, that way it is not run from the pack it is trying to protect.

The Batrium doesn't have a phone app and is expensive, so what about this BMS with 500A shunt: https://www.evworks.com.au/12-16-cell-i ... ent-system
With this screen https://www.evworks.com.au/bms-monitor
That way I can see cell voltages from the dashboard of the kart.

Priced a bit better than the Batrium and no apps or fiddling around?

[Ribfeast]

Looks like I need not worry about sag:
http://evtv.me/2012/09/battery-joy-and-the-car-guy/

[Richo]

The CA100 has an internal resistance of <0.6mR.
So at 200A the loss/sag will be 0.12V.
or less than 2V for the whole pack.

[Richo]

So are you ditching the 12V LiFePO4 idea?

Given we know now that your charger is adjustable.
and the controller is adjustable (with programmer).
and a BMS is likely...

There is no need even to stay with LiFePO4.
The only reason I suggested it was because this would have been a drop in replacement with minimal effort.

The 633T45303 controller claims to have:
Low voltage cutout 16.0V
Over voltage cutout 57.0V

57V/4.1V is 13 cells of NCM
SuziAuto's listing has NCM of 100Ah at $180ea. (total 4680Wh)
I had asked before - these have a 3C rating which is a bit better than the calib 2C.

Otherwise there are the LiFePO4 120Ah for $195.
15 cells would be the maximum. (total 5760Wh)

What concerns me is the low voltage cut-out of 16V in the controller.
This would be a terminating voltage of 4V per 12V battery in a 48V system.
That is way too low.
I really hope someone adjusted that otherwise it would kill the batteries...

[francisco.shi]

Would you consider one of these ones?
viewtopic.php?f=17&t=5883&sid=960bbdb21 ... 32c#p71556
I am not ready yet but in the next month or two I want to order the rest of my cells and I would like to order as many as possible to try to get a better price.
I can arrange them to make 48v.

[Ribfeast]

I wasn't planning to mess with the Sevcon, plan was to pop in 15 or 16 LiFePO4 cells, Zeva BMS, Zeva screen, load new charge profile in Delta-Q and call it a day.

The 12V pre-built LiFePO4 packs had limitations, I'd prefer to monitor individual cell voltages rather than having them in a sealed mystery box, plus it is cheaper to buy individual cells + BMS rather than the pre-built 12V packs.
Glad you pointed out the 57V controller limit, 16 cells would take the pack to 58V which would be unsuitable. I'd have to find out what voltage the Delta-Q is putting out on its lithium profile though. It has one for Samsung NCM and one for LiFePO4 but no indication of cell count.

Where is SuziAuto's listing? 13x $180 would work out $200 cheaper overall.

The BMS would cut power to the pack long before it dropped to 16V (I'd hope!). Plan would be to pop in an externally-powered contactor to disconnect the pack in event of any individual cell dropping to 2.5V. Or for NCM, whatever low voltage/20% SoC level that would be.

I've seen the kart shut down in the low 30's, so not sure if it has been programmed to 16V.

This is a list of the charge profiles available for the Delta-Q, no mention of how many cells in a pack. I've e-mailed them for clarification. Doesn't look like you can make your own profiles.
https://support.delta-q.com/hc/en-us/ar ... rithms.pdf

[Richo]

I wasn't planning to mess with the Sevcon, plan was to pop in 15 or 16 LiFePO4 cells, Zeva BMS, Zeva screen, load new charge profile in Delta-Q and call it a day.

Sounds like a fairly reasonable plan given all the options.

Glad you pointed out the 57V controller limit,

Don't forget these are user adjustable so unless you interface with it you can't guarantee it unless you test it.

Where is SuziAuto's listing? 13x $180 would work out $200 cheaper overall.

Follow this link and click the green box at the bottom of the page
https://www.ozdiyelectricvehicles.com/kits-parts
Weather or not he has them in stock I don't know.
Try not to bug him with too many questions as for most ev suppliers its only their side business.

Plan would be to pop in an externally-powered contactor to disconnect the pack in event of any individual cell dropping...

Good plan

I've seen the kart shut down in the low 30's, so not sure if it has been programmed to 16V.

Thank F for that
You definitely don't want to do the same thing to BIG $$ of lithium.

This is a list of the charge profiles available for the Delta-Q...
https://support.delta-q.com/hc/en-us/ar ... rithms.pdf

Interesting.

Valence is 3.3V/cell
Samsung is 3.7V/cell
Both are CC/CV profiles so is really beside the point.
This charger doesn't have the power to cause an issue in the CC mode for large format lithium batteries.
So the difference will be the end terminating voltage.