LTO battery question

[jhaz6471]

Those equalizers 1.2amp do not work well , they can have a .1v difference each cell progressive , 1.1 volt difference for 12 cells.

I use https://www.ebay.com/itm/Hot-Universal-4-LTO-LFP-Lipo-Battery-Active-Equalizer-5A-Battery-Cells-Balancer/284141408574?hash=item422825d13e:g:z4wAAOSw-uRfBT1-

They will keep the cells within a total of .05 volts

A Rolls Royce equalizer is Qnbbm https://www.alibaba.com/product-detail/QNBBM-6s-Yinlong-LTO-lithium-titanate_62327529720.html?spm=a2700.galleryofferlist.normal_offer.d_title.13292c89pCdUVY

 

[999zip999]

Don't know how you have those wired up but I would wire 4p then 12s . So you can monitor the parallel groups each parallel group of 4 I guess is 45 ah
24v 45ah total ?
Okay I see it now

 

[999zip999]

You can get a 6S RC hobby charger and 2-6 s balance wires and bounds have to pack at a time
I mean once you get in balance if she stay in balance and if it's not you could do it with a cell checker 6s and use the RC charger we need it.
Cheap and you have access

 

[HrKlev]

Its only a 18s 80Ah pack (I have put in 70Ah in the parameter settings because I only charge ti 4.1v), but here is a snapshot of the latest build I have made with this kind of BMS. I dont remember what the delta on the cells were, but I think it was around +/- 0.05v. Not perfect. I let the balancer work only above 3.9v, the balance current is 180ma, and "CellDiff Value to Start Balancing" is set to 0.004V. After a few days all the cells sat at 0.004V difference. These are automotive quality cells, but as long as there is not a lot of self discharge and you only let the balancer work at say ~75% SOC and up, I dont see how an external balancer will do anything better. OP should bleed off the highest cell groups manually to get a better starting point, and get the parameters set up correctly, then should be fine, IMO.

 

[999zip999]

Sorry typo I meant two 6s jst balance wires for access not 26s.

 

[john61ct]

4mV is a pretty extreme target delta

10-15mV really is close enough IMO

your rig your choice of course

 

[HrKlev]

Yeah, I agree, dont remember why I used it, Im using 0.01 on most of my other packs. Point was that the BMS does a nice job on a 80Ah pack. Its a big leap up to 180Ah, but as long as the cells are OK quality, I would think it should work. Also its free to try

 

[john61ct]

At such a tiny current rate and large cells, it really would be best to start with a very narrow delta, so the BMS just needs to do touch-up maintenance each charge cycle, maybe only an hour or two extra.

Taking days and days requiring a high voltage "float" so long, is really not great for cell longevity.

A higher current balancer

or atomizing the pack and doing it manually IMO are really the way to go.

I've seen power supplies from top vendors like Lambda / TDK, nominal 3V but adjustable and high amps, go for cheap on eBay, the price of one meal out with the family.

 

[999zip999]

All I meant with the RC charger it's very easy to do and you can straighten out the balance to start with.
You build your building with a good foundation.

 

[john61ct]

12S and LTO settings ?

Reco please?

 

[john61ct]

TDK Lambda SWS300-3 3.3V

universal AC input

max output 55A

OCP >105%, Constant current style

Adjustable voltage only goes down to 3V, so you would need an adjustable HVC

unless you're going to sit and watch it.

can probably be paralleled if you need higher current, LTO can handle 4-5C no problem

This lot only $18 each delivered, and I bet you could haggle

https://www.ebay.com/itm/TDK-LAMBDA-SWITCH-MODE-3-3V-POWER-SUPPLY-P-N-SWS300-3-/333776984747