diy solar

diy solar

Based in Groningen, The Netherlands

Interesting, but will that protect the battery against overcurrent? If the inverter is bypassing the BMS, it will not be able to measure the load from the inverter and will not shut off right?

No, it won't. But the 280Ah is rated for 1C, thus 280A max. My inverter is 1500W, so approx 125A on full load, so well within the specs of the cells.

The BMS won't register/measure the inverter and its load, but I don't care. I have a Victron BMV installed, and the inverter does pass the shunt, so I'm still able to see the current draw from the cells.

Also, off course I did put a fuse on the cells, so in case of a short, the fuse will blow (I've installed a 150A block fuse, a Littlefuse CF8, which protects everything: Both inverter and the BMS, so if anything goes horribly wrong, I still have a final protection which will kick in.
Also, the fuse is rated much lower than the 1C cell rating, so the fuse will be gone long before the cells hits its maximum discharge current.

Even if I run everything at max, in the unlikely case i'm using the inverter at full load, AND pull >30A from the BMS at the same time. But even in that case, the fuse won't pop immediately, since all fuses can handle overcurrent for a certain amount of time. The higher the overcurrent, the shorter the time you can exceed its rating). But realisticly: Chances this will happen is like 0.01% :)

And if I want to do that for whatever reason, I still can upgrade my fuse to a 200A version, my wiring is 50mm2 so should be able to handle it, but I don't see any need to oversize the fuse.


I also can run the inverter from the BMS, but with 120A i can't run it on full load. Also, lots of people are reporting the BMS generating a nice amount of heat when running a high loads, which would have me to redesign the enclosure (it doesn't have much airflow). And generally people recommend to stay on the low side and not stressing the electronics to high loads, so it will last longer.
 
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Great to see more Dutchies on this board! Im building a camper too, with some solar, inverters etc. Currently I have 8x 280ah cells and the overkill 24v BMS (planning to go 24v) and will need some help with topcharging.

Anyone experience with that?
 
Fastest way (at least, how I did it)

- Cells in series, with BMS connected
- Set HVD on 3.65V
- Charge with regular charger till HVD hits (1 cell @ 3.65V)
- Disconnect BMS and hook up cells in parallel
- Using a bench top supply, set voltage to 3.6V, and connect the load (important to first set the voltage, before connecting)
- Wait till current drops to (near) 0A
- Increase voltage till 3.65, and closely monitor cell voltage

You can just charge the cells parallel right away, without the first series charge which I did, but that either requires a decent power supply (capable to provide as much amps as possible, but keep in mind you're using the proper wire gauge to compensate for the loss). With a powersupply only providing a few amps, it will take days, even weeks. (8x280Ah = 2240 Ah @ 3.2V, so if the cells would be empty, and your powersupply only can deliver 5A, it would take 448 hours....)

Note: Always measure directly at the cells, don't trust the powersupply's reading: Voltage at the cells might differ due to voltage drops in the wiring.
 
@DJSmiley thanks for the repsonse, I checked your blog too and am now wondering what you call a bench powersupply, I see you have a regular charger listed on your blog, the meanwell. Ill probably go for the Mean Well PB 600 ( https://www.meanwell.com/Upload/PDF/PB-600/PB-600-SPEC.PDF ), the slightly largwer 24v version of your 12v edition. But I cannot figure out what top bench charger to go with. Any leads on those? (cheap :))
 
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A bench powersupply is also called 'Labaratoriumvoeding'. Used by electronics freaks, but it's just an adjustable powersupply.

Important for using as topbalancer: It should go as low as 3.6V, and it should have current limiting (and not shutdown by overload). The linked one is fine, as long as you don't only rely on its internal voltmeter, just check with a decent multimeter on the cells.

Another good option is the Riden RD6012. That's not a full powersupply but only the adjustable part. It requires a regular powersupply to power it. But it's way more advanced compared to that 37 euro Chinese thing. If you're planning to use if for other things as well, that's a better option (althoug its more expensive). You can use the Meanwell als power source.

That meanwell PB600 is a nice beast, but make sure you don't forget to select the right charge curve (I'd go for 2-stage)

But do you really need 40A charging? If you have decent solar and DC-DC charging, it's more a last resort, than really necessary. Assuming the battery isn't completely discharged, and you're using it only incidentaly overnight, with 24A you still can charge almost 200Ah within 8 hours... I don't see what advantages it has to be able to topup within a few hours.

There are a lot of people who say 'I have it installed, but actually never had to use it since my solar and dc-dc are able to keep it up'.
 
Also, off course I did put a fuse on the cells, so in case of a short, the fuse will blow (I've installed a 150A block fuse, a Littlefuse CF8, which protects everything: Both inverter and the BMS, so if anything goes horribly wrong, I still have a final protection which will kick in.



Interrupt rating 2000A

My automotive starting battery can supply that into a short. How about your lithium battery?

I've seen 3000A interrupt rating for ANL (from Blue Sea) but 6000A from a fuse manufacturer.
20,000A for class T fuse.
50,000A for breaker from Midnight Solar.

 
IR rating is specified at 58V. My battery is 12V.

Although LittleFuse doesn't specify it in their datasheet, other vendors like BlueSea do specify the IR at lower voltages.
Ok, I haven't checked, but I'm quite sure the Littlefuses are equally to the BlueSea ones

Interrupt Capacity: 10000A @ 14V DC, 5000A @ 32V DC, 2000A @ 58V DC

Source: http://assets.bluesea.com/files/resources/catalogs/sections_2009/DC_Main_2009.pdf , page 21

So thats why I think i'm good ;)

Also, a short, if it occurs, will be outside my box (I'm 99.9% sure about that) so the added resistance of connections and wire will limit any short current also, the max short current only applies directly between the poles.
 
Yes, with all my typing I forgot to add that you can engineer your fault with a controlled length of battery cable.
The times I've done the exercise, it appeared to be within spitting distance of the spec.

For the ANL and class T fuses, I thought interrupt rating ought to be higher at lower voltage. Especially for the larger 300VDC class T fuses. Those have a different curve but no higher interrupt rating shown even for lower voltage.

"So thats why I think i'm good ;)"

And of course you had already worked that out when you first designed the system, right? :)
 
Lot of "Dutchies" around here, i will feel right at home....Located nearby Enkhuizen in Noord Holland.
To bad i was a week to late with the meeting.
With best regards Igor
 
hmmmmm oke then neighbor, let me be more specific, westwood city....closer to the train station of Hoogkarspel.....
"het oude landpad", i think it will ring a bell or two?
Bicycle dealer on the corner? near albert hein.?

Mvg Igor
 
Considering a other post of you we are indeed very close, i would not be surprised if we know each other?
Care to meat up? on the bench on "landpad" after the tracks?
send me a pm
 
Can anyone help me out in making a 'kitlist' and high level schematic of what to connect and where in the chain? Or perhaps one of you has a good contact in the Randstad area that might be able to help?

Im looking to built a solar, shore and engine powered system for my camper, mostly 24v 'consumers' with some 12v too.
 
yep i can do hoogkarspel holland just pm me
in my mind it is just stupid to buy over and over a bench-power supply and a multi meter you can better rnt them ou you only need to use it once
 
Rent might be an option, but sometimes it's more expensive than buying some equipment yourself.

If you including rental fee and shipping fees... Than just grabbing an old powersupply and a small adjustable converter from Aliexpress is cheaper.
Cheapest way: Grab a https://www.aliexpress.com/item/4001078401775.html Costs you <10 eur, assuming you have a fan and an old powersupply which you can use for this. Otherwise, just visit a local kringloopwinkel (if they reopen) and grab one for a few eur
That one can provide 4A (you need to add some cooling, just let some air from a fan hit it). You can use any powersupply you have (A 12V /5A from an old monitor or a 19V/3-4A from an old laptop are perfect to use)

First, charge all cells in series with a BMS connected, set HVD disconnect to 3.65V. Once 1 cell will hit that, the BMS will disconnect the carger. Since you can use a nice beefy charger that won't take too long, depending on the SOC and the charger a few hours.
Once that's done, reconnect all in parallel, connect the cheap powersupply, set it to 3.65 and wait till the current is dropped to almost zero (and measure on the cell poles). With only 4A that will take some time, but since the cells are almost full (with the series charging) it only depends on how much they differ. Generally, if the cells are pretty close, it won't be many hours to finish the top balance.



Maybe a friend who has a powersupply you can use is an option. If you're willing to travel, you can probably use one from a fellow dutchie member here as well (I'm located in Nunspeet for example)

If you're going for a 24V system, that's not gonna be a problem, but you are a little more limited in the available equipment, since most campervans are 12V based. 24 will do, but if you have for example a 12V alternator you can't use a regular DC-DC charger.
However, depending on your budget you can do some creative options if you're not willing to pay for a 12->24V DC charger.

- Make the shorepower charger switchable between shore power, and engine power by adding a 'source' switch and installing an starter/alternator powered separate inverter. You only need to buy a 12V inverter with sufficient power and wire it to the alternator / contact / D+
- Use a 12V step-up converter like https://www.aliexpress.com/item/32886419468.html
Set the output voltage to eg 55V. That will limit the voltage drop on the wire. And near the housebank, install a solar charger (eg an Epever) and hook up the 55V to the PV input. The solar charger will work as a great charger. You only need to make sure the charger won't overload the boost convertor. A 30A charger on a 40A boost convertor will work fine and will give you a 12 -> 24V DC-DC charger for approx 100-125 EUR
If you're really into saving, you can use a relay to simply disconnect the solar while driving and use the boost as input (relay will be triggered by D+ / alternator)
 
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Hello guys, just wanted to introduce myself by saying that I live in Groningen (area) in the north of the Netherlands and that If people in the area are keen on meeting for workshop events (assemble things together and make tests) I would be happy to organize that. Other locations in the Netherlands might also be doable.

I am a solar hobbyist trying to make small steps towards integration of solar energy and batteries in city environments where there is no space for big solar panels and where small set ups could feed a few low consumption devices (TV, led lights, modem, charging gadgets,...).
I also live in the Netherlands (Zuid Holland) - just starting my journey on solar + Li-ion systems. It will be great to connect with fellow DIY solar enthusiasts!
 
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