[RE-wrenches] DKD Lithium Batteries

[Brian Mehalic]

Battle Born seems somewhat similar (internal BMS) - who knows how many different labels get slapped on batteries coming out of the same factory. 

Their manual does say you can do series connections up to 48 Vdc. 

Brian

> On Mar 4, 2019, at 8:50 AM, Roberto Kruse <roberto.kruse at sercsa.com> wrote:
> 
> 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,
>> 
>> <IMG_4362.jpg>
>> 
>> 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.
>> Does anybody have any thoughts (positive or negative) or experiences with these batteries? 
>> 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
>> (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
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