Hi Justin.
Thank you so much for the the info, I’ll remove them from my system and use ANL fuses and holders instead. Bless you. Mike.
Hi R.L.
That’s funny, I was looking at fireproof boards earlier this evening. His comment (Karl-Heinz) kind-of got me worried. Regards. Mike.
I have to agree about the Chinese circuit breakers. I had some on a previous installation and they played up. I worked out they were unsafe within a few weeks of installing them and switched to fuses.
However, I am concerned that ANL fuses will not have a high enough Ampere Interrupting Capacity (AIC) for lithium batteries. You need to check the AIC of your batteries. You might get away with MRBF fuses as they have a slightly higher AIC than ANL fuses, but really Class T is the gold standard for lithium.
Thank you NotMy Name.
After the comment from another poster about the breaker switches, I removed them immediately and planned to install ANL fuses instead.
When you mention the Class T fuses, do you mean I would have to replace all my existing ones; 200A at the battery, 150A at the Inverter, 40A at the Victron MPPT 100/30, and the 20A at the 6 Way Fuse Box?
Bless you. Mike.
I have now ordered a Flame-Proof, Fire Retardant board, made to the regulations of the UK. I have removed all my appliances from the old board in readiness of a complete rebuild, using many of the recommendations I have been given on this forum.
Thank you all.
Mike.
Hi Mike,
Sorry, just the 200A at battery should need Class T and the rest you should be OK with ANL, or MRBF etc. Sorry for the confusion, but definitely better with fuses than cheap Chinese breakers.
Hi NotMyName.
Thank you so much for that info, I will order a Class T fuse tomorrow. I’m assuming that it will need to be a 200A one?
Regards.
Mike.
200A is too much for a 35 mm² cable; it should be 70 mm².
Hi.
Thank you for the advice, I have reviewed the fuse and have changed this to 175A Class T fuse for my 35mm² cables.
Regards. Mike.
Hi All.
I have now completed my latest wiring diagram, please check to see all is okay. I would also like to ask a fuse question if I may! As I have a Class T 175A fuse after the parallel connection on the main feed to the busbar, should there be a fuse on the other battery to stop anything going bad if that one shorts?
M:C Trailer Solar Build V5.6 30:09:26 10-47GMT.pdf (96.6 KB)
Each battery must be fused!
Hi Karl-Heinz.
Will it affect the connecting cable length between the batteries or is this allowed? I’m also assuming that the fuse should be a 175A Class T as well?
Regards.
Mike.
The fuse depends on the BMS fitted and the cable gauge!
The cable length should be the same as that of the first battery.
Hi K-H.
Sorry to bug you, but the two cables between bat 1 & bat 2 have to be the same length, so that the parallel batteries equalise. How then, if I place a Class T fuse on the positive cable of bat 2, determine the exact length of the cables + fuse to be the same as negative cable?
Regards. Mike.
Hi Mike,
Edit: moving away from simple paralleling to individual fusing of batteries is a good thing IMO, but there are more rules 
In this case we are aiming to wire each battery directly onto the busbar. Having a fuse between each battery and the others protects against any battery going “bad” by preventing the others from piling charge into it, as you suggest.
The combined +ve and -ve cable length must be the same for each battery.
It doesn’t matter how that length is distributed between + and - as long as the total length for each battery is the same as every other battery.
The cable length represents resistance and we want the same resistance for each battery so they each take an equal share of the load.
I have 25mm2 cables on each (PylonTech) battery and each cable set is protected by an 80A NH00 knife fuse.
Hi David.
Are you suggesting to wire the batteries like this diagram, so each can be fused?
Regards. Mike.
M:C Trailer Solar Build V5.0.6 28:09:26 09-00GMT Sheet #4.t2d.pdf (42.1 KB)
More-or-less yes. Disclaimer: this is just my opinion, I don’t do this for a living
I would use only 1 kill switch AFTER the buss.
Double-check if 175A is OK to fuse a 35mm2 cable. It seems quite high to me. Are you expecting each battery to operate in a normal range above 100A? Remember: the function of a fuse is to protect the cable.
If not, you might look out for a smaller classT fuse that would make more sense with having a 150A fuse after the buss bar.
FWIW In my (48V) system I have 80A fuses on each of 9 batteries on 25mm cables. After the busbar I have 400A fusing going into an 8kW inverter. Each battery has a normal peak throughput around 35A.
Hi David.
Could you share your wiring diagram with me, so that I can get a better idea of what to do, please?
Regards. Mike.
Hi Mike,
I wouldn’t say this is “what you should do” since our builds are quite different, but the major concern is whether there can be safety improvements by individual fusing of Lithium batteries compared with unfused parallel wiring. I think there is and it is worth the trouble and expense. The cost premium for fusing like I have is in the region of £600 compared with just running the batteries in parallel. Whether one thinks that is a worthwhile expenditure is a personal choice
I don’t have a wiring diagram like yours, but perhaps this photo and the explanation will be sufficient?
Each battery has its own fuse before it gets to the buss bar and this protects against the (admittedly unlikely) case where an individual battery / cable set goes short or low voltage. At that time, the other batteries would feed into the short at peak current and in the absence of a fuse the situation would very rapidly get out of control. The amperages involved during such an event would be very high and that is why fuses with large Interrupt current rating (like Class-T or NH series are required).
The 6 PylonTech batteries at the bottom are connected to the Lynx buss bars using their commercial 2 metre 25qmm cable sets. I cut the +ve cables 50cm from the end and added lugs to the cut ends to fix onto the 80A NH00 fuse/disconnect holders.
At the RHS of the buss bar are the cables to the inverter. This inverter is specified to have 2x 50qmm cables per pole and I have fitted a 200A NH1 fuse to each of the +ve cables.
Hi David.
Thank you for the image, wow! That is some kit you have there, judging by the wall on the left, this is a very large domestic setup.
Makes my little setup in a box trailer look a little bit tame. This is a learning curve for me and I appreciate your help/time in giving me some good intellectual advice.
Bless you my friend. Mike.