failed EVE LF280 after 150 cycle!

[Checkthisout]

I meant "self discharge rate" because 4 wire internal resistance measuring devices can't reflect real discharge rate and only show static internal resistance that can't so helpful because most of the cells have more or less similar resistance in our tests!

Would you mind sharing pics of your setup installed in the floor machine?

 

[Amitis]

Guys, I knew that single 24V , 36V or 48V packs are better choice in comparison with different 12V packs to be wired in series! from balancing point of view!
but please pay attention to different subject:
1st and most important thing is changing marketing tast is really difficult and every costumer just like to remove their 12V gel battery and simply replace 12V lithium battery without any extra wiring or modification! thats why drop in replacement invented ! ?
2nd weight of lithium battery packs will be an advantage if you can limit its single pack weight below 20kg ! otherwise if you have a single packs of lithium battery equal or heavier than 35 to 40kg conventional gel or agm SLA battery can be a merit? yes it can be decrease total weight but it is hard to explain to a customer that comper single packs with each other! thats why we are trying hard to find a way to really use LFP battery as a true drop in replacement! by hard effort in sorting and other idea might be helpful
3rd We tried lower capacity but fitted voltage of 36V also it works better from balancing point if view but there is looping current between packs! and also this idea isn't applicable for all voltage what happened if you need to reach to 72V or 96V ! is there a way to use still single packs of 72V or 96V simple low weight high capacity lithium battery! no way! but if problem of wiring standard 12V battery can be solved then development of this type of battery will be really straightforward! for different application and voltage level!
4-More and more reason can be considered that using 12V battery packs can be really helpful if we can overcome issues of balancing!

 

[Amitis]

We used our LFP battery on both ride on "T7, T16" and Walk behind "T300, T500" models of Tenant already worked fine for more than two years !

Already posted but putting in my 3rd or 4th vote just make a single 36 volt pack with a single BMS. ?

We have a Tennant walk-behind. I hate that it's 36 volts.

"At Tennant, we use this one weird voltage so we can guarantee absolutely no readily available chargers on the market will work on our stuff"

 

[Partimewages]

can you introduce me a battery bank balancer , can you share a link of such balancer model for 12V battery banks?

I don't have any experience with them. I only know they exist.
My recommendation would be to rebuild the pack into a 12S pack with a different BMS with active balancing.

 

[mikefitz]

can you share a link of such balancer model for 12V battery banks?

HA 01, or HA 02 may be suitable!,

BMS to maintain balance 12v batteries in series

Just wondering if it's possible to use a BMS to keep 12v batteries balanced with each other when connected in series such as a 4s 48v system etc?

diysolarforum.com

 

[OffGridForGood]

The OP is trying to seemlessly upgrade existing equipment from 12v Lead-Acid to LFP.
The customers will not be tech-savy enough to do more than drop in replace three existing L-A with new 12v LFP.
To overcome the BMS issue, the OP would need a sphistacted system with wireless comms between the three cells, on master BMS and two slave BMS to follow instructions. Pretty tough to see how this would be cost effective.
The other problem I see is the charging equipment each customer already has will be based on L-A and will not be suitable for the new LFP.

I see the issue with marketing this to existing consumers as an 'upgrade' and trying to keep costs to a minimum, but the only solution that seems to make sense is a factory rep visits the customer, changes the unit charging for LFP and changes the battery for the customer, using the new 12s LFP pack (or to fit the form-factor of the battery compartment it may be better to make three parallel 80Ah 12s packs each with it's own 12s BMS. For the marketing part, the upgrade is worth the cost because instead of batteries lasting a few years, the LFP will last 10-12 years.

 

[Amitis]

The OP is trying to seemlessly upgrade existing equipment from 12v Lead-Acid to LFP.
The customers will not be tech-savy enough to do more than drop in replace three existing L-A with new 12v LFP.
To overcome the BMS issue, the OP would need a sphistacted system with wireless comms between the three cells, on master BMS and two slave BMS to follow instructions. Pretty tough to see how this would be cost effective.
The other problem I see is the charging equipment each customer already has will be based on L-A and will not be suitable for the new LFP.

I see the issue with marketing this to existing consumers as an 'upgrade' and trying to keep costs to a minimum, but the only solution that seems to make sense is a factory rep visits the customer, changes the unit charging for LFP and changes the battery for the customer, using the new 12s LFP pack (or to fit the form-factor of the battery compartment it may be better to make three parallel 80Ah 12s packs each with it's own 12s BMS. For the marketing part, the upgrade is worth the cost because instead of batteries lasting a few years, the LFP will last 10-12 years.

I'm curious ? to know more about such a BMS with master/slave wireless comunication to balance all three packs cells with respect to each other! if you know such a bms or have a link about it please let me know!

 

[Zwy]

I've read thru this thread and it would be so much easier to use a single pack of 36V and install an onboard charger.

I don't understand why the batteries need to be changed out for recharging. I have a walk behind floor scrubber and installed an onboard charger. I never remove the batteries, no need to.

You will be plagued by balance issues as floor scrubbers do have a high amp draw. Not only the motor for the brushes but the vacuum will draw high amps also.

Not hard to find a 36V charger, there are plenty out there.

 

[Ampster]

I agree with all the previous posters suggesting reconfiguring these to 12S using one BMS and limit charging current to 3.45 per cell or 41.4 volts for the pack.

 

[Hedges]

How about 3x 12V chargers mounted on board. One AC cord to plug in, and all three "12V" batteries get fully charged each time. That maintains balance between them.

 

[Ampster]

That maintains balance between them.

That will charge them all to the same voltage but it will not necessarily keep them balanced on discharge will it?

 

[Zwy]

That will charge them all to the same voltage but it will not necessarily keep them balanced on discharge will it?

No, it won't.

 

[Hedges]

Nothing will keep them balanced on discharge.
The only time any balancing scheme is applied is when the cells/batteries are charged into the upper knee of the curve (or a scheme for lower knee.)

Fully charging three batteries separately is top-balancing, just like you can fully charge individual cells to top-balance without paralleling them.

 

[OffGridForGood]

I'm curious ? to know more about such a BMS with master/slave wireless comunication to balance all three packs cells with respect to each other! if you know such a bms or have a link about it please let me know!

REC BMS

 

[740GLE]

Battery Balancer - Victron Energy

Equalize the state of charge of two series connected 12V batteries using the Battery Balancer. Find a Victron Energy dealer near you.

www.victronenergy.com

Two of these should do it?

 

[Checkthisout]

So costly to do it that way

 

[toms]

How about 3x 12V chargers mounted on board. One AC cord to plug in, and all three "12V" batteries get fully charged each time. That maintains balance between them.

This is the way. It doesn’t matter if the individual packs get imbalanced then.

 

[robot_zombie]

could you make 3x 4s drop in 'blocks' but with plugs / connectors between blocks that result in a single 12s pack / connect to a single BMS. sorry if I misunderstood the problem. once working right you should not need to periodically rebalance (assuming no cell fault), my DIY pack has over 300 cyc no worries (catl 302 / JKbms 2A balance, balance on >3.45V abs V ~3.49 VPC). (hmmm doesnt help with the charging issue)

 

[Ampster]

Nothing will keep them balanced on discharge.

I agree but a 12S BMS will have a better chance at keeping all 12 cells closer together. The OP has already purchased many 36 volt chargers which can be programmed for his cells. I think buying that many 12S BMSs is a more optimal solution than buying that three times that many chargers and throwing out the existing chargers.

 

[Hedges]

True, although if packaged as 12V batteries for his customers, easier for them to comprehend and wire 3x 12V chargers than balance leads for 12 cells.
Some special harness and connectors could make the 12s BMS connection idiot proof.
Assuming only a few batteries already assembled.