[RE-wrenches] DKD Lithium Batteries

[Roberto Kruse]

Hi Kienan.

I am not familiar with these particular batteries but I have some
experience with LFP.
Since there are no com wires from battery to battery, it seems that they
have an internal BMS.
In this case, I would say that these batteries cannot be connected in
series. From what I have seen, if you want a 48V battery bank with LFP, you
have to order the batteries at this rated voltage from the beginning. You
can connect several in parallel.

Regards,
Roberto Kruse

El lun., 4 mar. 2019 a las 7:23, Kienan Maxfield (<maxfieldsolar at hotmail.com>)
escribió:

> Hello all,
>
> I just got back from looking at an off-grid system that is only about 4
> months old or so, and it has several problems. I have specialized in
> off-grid for 8 years, so most of the problems will be easy for me, but
> there's just one thing that is a bit perplexing and I'm hoping someone
> might have some advice.
>
> The system was "designed" by some retailer in Texas (I don't know who) and
> the home-owner found some local installer to put it together for him (they
> already charged a ridiculous price and they won't come back). The battery
> is a big bank of DKD LiFePO4 batteries, each one says 100 Ah @ 12.8V. They
> are in series sets of 4 for 48V. I think there were 5 strings (500 ah
> total). There are no com wires from battery to battery or anything like
> that (nor did I find anywhere for com ports). I have not yet been
> successful in finding any information about these batteries online. I'm not
> that familiar with this type of battery and I'm hoping that some of you
> might have some info/insight on a couple of questions about this situation.
> Here's a picture of one of the batteries,
>
>
>
>
>    1. The biggest question is if this configuration is okay. I'm not
>    familiar with this type of batteries, but I saw at least one brand that
>    said not to put their batteries in series. They said that (at least with
>    their brand) if you needed a 48V battery, you couldn't use (4) 12V
>    batteries.
>    2. Does anybody have any thoughts (positive or negative) or
>    experiences with these batteries?
>    3. Does anybody have any technical information (like a voltage/SOC
>    curve or anything else) for these batteries?
>
> I will be fixing the other things in his system, but when he asks what I
> think about his battery bank, I don't know what to tell him at this point.
> He also has no idea how to tell how full his batteries are, and since it
> doesn't seem like his batteries have any kind of readout or anything, I'm
> not sure what to tell him on that either. If I could find a Voltage/SOC
> curve or a voltage/SOC conversion table, that would help on that front.
>
> Thank-you,
> Kienan
>
>
> *Maxfield Solar*
> *maxfieldsolar at hotmail.com* <maxfieldsolar at hotmail.com>
> * (801) 477-0-SUN (477-0786) (801) 631-5584 (Cell) (preferable contact
> number) *
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-- 



*Ing Roberto Kruse Font* | *SERC – Costa Rica*| *roberto.kruse at sercsa.com
<roberto.kruse at sercsa.com>*
Tel (506)2273-4545 | Fax (506)2273-1010 | www.energiasolar.c
<http://www.sercsa.com/>r

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