Search results

Oh good question - the lynx tech specs say 60V. But it's a very robust unit with good separation between positive and negative so I don't see why 200 plus volts would be a problem, excluding the fuses of course.

Yeah that should work. With some creativity you can also attach a fuse holder to the positive end lug and attach another 2 wires there.

I've found a solution to using Midi fuses in a Victron Distributor - see the thread on it: https://diysolarforum.com/forums/wire-connectors-junction-boxes.59/

I've found a workaround to fit Midi fuses into a Lynx Distributor, but I haven't energised it yet. The Distributor is made to hold Mega fuses, but unfortunately they're not available in amperages below 125A, at least not rated for 48 Volt systems. Any problems with this? Here's what I did. 1...

Unfortunately not - the Lynx Distributor has 8mm bolts on 51mm centres and only handles Mega fuses. I'm resorting to mounting a Midi fuse outside the Lynx. It would have been nice if the Distributor used some kind of insert fuse holder that was swappable to hold different format fuses. Maybe...

Wow great insights, thanks Hedges! That makes sense, but we can't put a Class T fuse on every circuit because of size and cost, and they're not available in low enough amperage ratings. First I've heard of those - thanks! They're too bulky though - for amperage ratings at or above 60A the...

Yep I've got a Class T fuse at the battery positive terminal, and also one mid-string between battery cells. This discussion is about using an MRBF on the busbar to supply a load circuit at say 50A, at a maximum voltage of 57.6V. What do you think for that application?

Yep! I'm going to cover that with communication from the REC BMS to the Victron gear via CAN-bus. The BMS can tell the Victron gear to stop charging the battery in cold temps, while still leaving the contactor open to allow discharge. Apparently it's even smart enough to allow the solar...

Great, I was planning on charging to 3.60V rather than 3.65V. 3.50 would give even more buffer below the fuse voltage threshold, sounds good, thanks!

Great, that's what I thought too. Now, if the Victron 58V Mega fuses are good for 48V systems, what about a Victron 58V Midi fuse in a Victron midi fuse holder? They're described as "58V for 48V products" :-) https://www.outbackmarine.com.au/victron-fuse-holder-for-midi-fuse...

Yeah, done that. The voltage is fine, it's just the short-circuit current that's "iffy" but I'm going to give it a try. :-)

Yeah that's valid. My thinking was that the contactor is kinda "part of the battery" as it's controlled by the BMS.

Yeah it's only 2 panels in series so it'll be below 100V. It can handle more than that - you can oversize the panel power and it'll clip its production. I'm starting with 2 of these MPPTs with future expansion to 4 as noted in the schematic.

Good idea thanks - I've posted a question on the Victron community forum, I'll let you guys know of any info from there. :-)

It's for an offgrid cabin with some existing 24V DC loads.

Thanks Steve! Yes that's what I'm doing. I'll be charging to 3.60 V per cell * 16 cells = 57.6 V. 3.60 is the level to which I top-balanced the cells. Consider the Victron Lynx Distributor which is used in Victron's largest, multi-inverter / multi-battery 48V nominal systems. Victron says...

The interesting thing is, some other fuses specify a maximum voltage of 58V and are OK for 48V systems. Eg some Mega fuses and midi fuses: https://www.outbackmarine.com.au/victron-midi-fuse-60a-58v-for-48v-products-1-pc~48556...

Yeah that makes sense - wouldn't my approach also avoid stress on the cell terminals?

Thanks Paul! What fuses would be suitable to protect <100A circuits coming off a 48V nominal busbar? I've already got class T fuses for the battery itself.

That's what I'm planning on doing too - a strong battery box with the cells packed so they're not under constant pressure, but have no room to bulge. What do people think about that approach?

Hi - I was thinking of using MRBF fuses on my busbar of my 2P16S off-grid system. I'm planning on charging the cells to a maximum of 3.6V for a total of 57.6V, which is just within the fuse's maximum rating of 58V. HOWEVER, product info also says "The breaking capacity meets the requirements...

I haven't got the panels yet, but I'm looking at Jinko Tiger JKM370M-60HLM. Sorry, I'm not organised enough for a parts list. :)

Thanks for the bump boondock :) My build is coming together, the main change is the battery cable is 70mm2 instead of 95mm2. Hopefully that'll be OK 'cause if the current approaches 225 Amps, it wont' be that high for long. Also I couldn't find Mega fuses below 100A that were rated for 48V...

Good points, thanks. Maybe rather than stripping the whole cable I'll just strip intermittently at spacing to match the battery terminals.

Great, thanks for the info!

Thanks Sojourner. His threshold for cell-cell unbalance before connecting in parallel is 200 mV. My unbalance is only 62 mV, so maybe I'm OK to connect up? But I like how he gets around a lack of busbars - putting twisted copper cable under the nuts, and tightening them down. I might just do...

Update: I've top-balanced each batch of 16 separately to 3.6V. Now the two batches have settled: - Batch A: 3.507 V - Batch B: 3.569 V Is that close enough to assemble them into a proper 48V pack, with each cell pair including one cell from batch A and one from batch B?

How does this look? I realised that a 100/20 charge controller can feed 48V to the battery while keeping solar voltages below 120V. That's enabled me to switch from 24V to 48V battery voltage, which simplifies everything and reduces currents, compared to my previous design. Cells are new from...

Where I am, battery standards talk about "arc flash incident energy" to quantify the effects of a short-circuit. A large-cell 48V battery has a high value, i.e. a dangerous arc. Even though there's a fuse at the positive terminal, it's still possible to accidentally short-circuit the negative...

Ok that makes sense, thanks!

At that voltage how would I measure amp-hours to determine battery capacity? I can measure amps with my Fluke clamp meter, but not amp-hours.

That was going to be my next question - whether a capacity check is necessary. :) I guess it's a good idea to make sure the product is correct. That's a great option thanks, 'cause I don't have a usable 48V inverter yet. Cool. Yep I was planning on doing that too. Sounds good to me - long...

I've just purchased 32 CALB cells, 163 Ah each. Like the ones in this pic, with the raised terminals. https://www.globalsources.com/LiFePO4-battery/CALB-Grade-A-new-prismatic-cell-3-2V-163Ah-LifePo4-1178960172p.htm#1178960172 I've got a 50A single-cell charger, but not enough busbars to...

Yeah I'll be replacing that. Thanks!

True! I'll look into it.