diy solar

diy solar

Cross-checking my ideas for my Battery v2 after Battery v1 Nighmare

silverstone said:
So the LF304 should reach 200°C ?
Click to expand...

Even if it does: I would like to know how it got to that stage in the first place without the BMS kicking in. An internal short (dendrites) can not carry that much current [1] and the internal short will just drain the cell, again kicking in the BMS.

[1] 'ISC due to Li dendrites are often referred to as “soft-shorts”, since they are known to “self-heal” by melting (melting point of Li metal: 180.5 °C) due to the fuse-effect'
 
upnorthandpersonal said:
Even if it does: I would like to know how it got to that stage in the first place without the BMS kicking in. An internal short (dendrites) can not carry that much current [1] and the internal short will just drain the cell, again kicking in the BMS.

[1] 'ISC due to Li dendrites are often referred to as “soft-shorts”, since they are known to “self-heal” by melting (melting point of Li metal: 180.5 °C) due to the fuse-effect'
Click to expand...
No, fair enough.

Internal short would be the only thing you cannot do anything against.

Everything else will be covered either by bms, smoke detector or some other overtemperature protection.

Thanks 😊
 
upnorthandpersonal said:
Yes, but I meant that temperature is much more important. The reason for the cycle life difference between 280k and 304 is that they test them at different C rates: 0.5C vs 1C
Click to expand...
Can only imagine what sitting in an outdoor enclosure in summer does to degradation, eg4 power pro 280ah for example. I see a few batteries with heating to allow sub freezing charging, but seems like avoiding high temps would be just as critical if not more so?
 
Brucey said:
So you get a piece of this and then the 285-150s use it as a bus?

Click to expand...
If you want the exact part list here it is :) :
- DIN Rail for mounting the terminal blocks: https://www.elektromax24.de/2m-weidmueller-trageschiene-ts-35x15-ll-2m-st-zn-gelocht
- Wago 285-150 to connect the wires: https://www.elektromax24.de/wago-2-leiter-durchgangsklemme-285-150-50qmm-grau
- Wago 285-450 to bridge terminal blocks together ("jumper"): https://www.elektromax24.de/wago-querbruecker-285-450-fuer-50qmm-klemmen-grau
- Wago 285-447 to get a "voltage tap" (typically for measurement, prechargee, smaller cross-section): https://www.elektromax24.de/5-St.-Wago-Potentialabgriff-285-447-fuer-Hochstromklemmen-50qmm

The only thing I'm still debating is how to (properly and securily) connect the JK BMS wires: see https://diysolarforum.com/threads/terminal-blocks-and-class-6-extra-fine-stranded-conductors.80670/ (still no reply sigh :confused:). The JK BMS wires I would assume are class 6, so technically I guess they CANNOT be connected to the wagos directly (*maybe* with ferrule), otherwise the pressure of the cage clamp would simply destroy them.

But I might also need to use the smaller brother WAGO 285-135 for the JK BMS wires since they are so small (taken individually at least) ...
 
Brucey said:
So you get a piece of this and then the 285-150s use it as a bus?

Click to expand...
Note that you do NOT use the DIN rail as a bus. The "bus" is "provided" by the "jumper" WAGO 285-450 :)

DIN Rails are used as a bus for earth connection regularly. For power transfer (i.e. in copper, like the one you linked) I'm not so familiar. Copper DIN rail is good, the question would be how good the *electrical* contact between the DIN rail and your terminal block is.

FYI this is WITH contact between DIN rail and "power" contacts, but usually Earth doesn't carry continuous current:
www.elektromax24.de

Wago 2 Leiter Schutzleiterklemme 285-157 50qmm gruen-gelb

POWER CAGE CLAMP®, nur auf TS 35 x 15 2,3 mm dick Kupfer
www.elektromax24.de www.elektromax24.de

The WAGO 285-150 (grey) and 285-154 (blue) do NOT have an electrical connection to the DIN rail. It's plastic on the back and plastic clips, nothing connecting the "back" to the power terminals.
 
silverstone said:
Note that you do NOT use the DIN rail as a bus. The "bus" is "provided" by the "jumper" WAGO 285-450 :)

DIN Rails are used as a bus for earth connection regularly. For power transfer (i.e. in copper, like the one you linked) I'm not so familiar. Copper DIN rail is good, the question would be how good the *electrical* contact between the DIN rail and your terminal block is.

FYI this is WITH contact between DIN rail and "power" contacts, but usually Earth doesn't carry continuous current:
www.elektromax24.de

Wago 2 Leiter Schutzleiterklemme 285-157 50qmm gruen-gelb

POWER CAGE CLAMP®, nur auf TS 35 x 15 2,3 mm dick Kupfer
www.elektromax24.de www.elektromax24.de

The WAGO 285-150 (grey) and 285-154 (blue) do NOT have an electrical connection to the DIN rail. It's plastic on the back and plastic clips, nothing connecting the "back" to the power terminals.
Click to expand...
Ok thanks I understand now I was missing the bridge pieces you linked. Seems like a nice clean solution.
 
Brucey said:
Ok thanks I understand now I was missing the bridge pieces you linked. Seems like a nice clean solution.
Click to expand...
Everything has pros and cons.

I was just thinking why they only do green/yellow terminal blocks with DIN rail & Power Contacts connected. Probably because most of the time you have more than one potential on a single DIN rail. So of course bridging DC+ to DC- is a VERY BAD idea (you need to remember to cut that DIN rail if the DIN rail was internally connected to the power contacts :ROFLMAO: ).

Some products at (much) lower ratings allow to mount (typically just for the "neutral") a busbar and distribute that across the terminal blocks e.g.
- WAGO https://www.wago.com/global/rail-mo...-distribution-board-set/p/821-122#description
- Phoenix https://www.phoenixcontact.com/en-p...n-ground-terminal-block-pti-4-pe-l-nt-3214047

I'm personally not aware of others but then again I never looked very deep into this particular case. I usually use jumpers provided by the manufacturer.
 
upnorthandpersonal said:
Yep - at cold temps, the battery limits charge current itself due to increasing internal resistance. No such limiting at high temps.
Click to expand...
But I'm wondering with the low internal resistance ...

Can it really self-heat excessively (provided you stay within reasonable current ratings of fuse/breaker, below say 0.5C continuous, no bad connection, etc) if you start at an ambient of say 30°C ?

Of course if you leave it outside under the sun in a steel black box it's another story, alright :ROFLMAO:
 
Think about Andy's garage in sunny hot Australia. They see 35C for sure in his cabinet.
It's not about self-heating (LFP has a very efficient round trip), it's more about ambient over 30C which many people not in our Nordic region face for long periods of time during a year.
 
upnorthandpersonal said:
Think about Andy's garage in sunny hot Australia. They see 35C for sure in his cabinet.
It's not about self-heating (LFP has a very efficient round trip), it's more about ambient over 30C which many people not in our Nordic region face for long periods of time during a year.
Click to expand...
In my insulated garage I have approximately a delta of +10°C between outdoors and inside. So the battery is currently at 18-20°C, just because of the losses of the chargers and/or inverters.

It's (almost) warmer than in the house during winter months.

So I might have around 30°C soon. But that is why I also put a small heat pump there, just in case it's too hot (or cold) :) .
 
Now I'm also (finally) starting to understand why inverter communication with BMS is so important ...

a. In order to prevent cell overvoltage & BMS disconnection. Right now I needed to set a float voltage = absorbtion voltage = equalization voltage = 54.4V in order to prevent cell overvoltage (yeah ... one battery seems to be quite unbalanced, even if I top balanced it less than 1 week before)

b. In order to charge rapibly. If I take a short-circuit current of say 10kA at a voltage of 56V, that's equivalent to approx. 5.6 mOhm (let's say 5mOhm to make math easier). That alone will require, at say 100A, an EXTRA voltage on the inverter terminal of 0.5V. Plus approximatively the same to compensate for voltage drop across cables (currently it's approx 2 x 16mm2 wires in parallel 10m runs for 2 batteries -> R_each_bat = 5 mOhm for each battery). So 1V overall extra is needed in order to charge at full charge current (for this temporary setup at least). That might be easy to achieve if your absorbtion voltage is set to e.g. 55.2V when float is set to 53.6V-54.0V, but that is far too high for my setup, where one cell will just all of a sudden jump to the moon ...)


Previously point a. was the determining one. Now it's more related to point b. I'm charging barely at 40A each battery (instead of the possible / designed 100A).

In order to fix this, I plan to implement https://diysolarforum.com/threads/j...g-logic-open-source.79325/page-6#post-1029595 (@Der_Hannes solution).

Just to let you know the update on the situation :)
 
silverstone said:
Did you use / will you use treated wood (usually green-ish, for outdoor use and insect/termite resistant) or just regular untreated wood ?
Click to expand...
Treated lumber is very corrosive. You need to use specially rated fasteners with it or they will quickly deteriorate. I wouldn't recommend treated lumber for anything electrical.
 
wheisenburg said:
Treated lumber is very corrosive. You need to use specially rated fasteners with it or they will quickly deteriorate. I wouldn't recommend treated lumber for anything electrical.
Click to expand...
I thought I read that as long as fastener are galvanized it should be fine.

But yeah, for the battery I'm building now, it's raw (untreated) wood.
 
silverstone said:
I thought I read that as long as fastener are galvanized it should be fine.
Click to expand...
Galvanized nails are Ok for treated lumber. The "Hot Dipped Galvanized" are better and will last longer. Untreated regular nails or screws are not recommended. Now some of this depends on where the items are used too. If they are in a perfectly dry location, they probably would not be severely affected by corrosion. Corrosion is usually going to require some moisture. Of course the whole point of treated lumber is that it is meant for locations that will have some moisture. If you have some moisture, plus untreated fasteners, plus treated lumber, that is a bad combination.
 
Last edited:
silverstone said:
I thought I read that as long as fastener are galvanized it should be fine.

But yeah, for the battery I'm building now, it's raw (untreated) wood.
Click to expand...
Just to clarify because I re-googled what I found back then ... The key word is "hot dip galvanized", which provides thick enough zinc. Do NOT use electrically galvanized steel ! Electrically galvanized steel is NOT suitable for outdoors anyways, where treated wood would be used.

Use either hot dip galvanized or stainless steel.
 
You must log in or register to reply here.

Similar threads

Z
RV Battery Build – looking for advice and such…?
Replies
4
Views
579
Zbugsii
Z
Back
Top