Brandon avatar image
Brandon asked

Pylontech UP2500 and Multiplus II 24/3000 fuse sizes

I am trying to work out fuse/CB sizing for my 2 x Pylontech UP2500 batteries an my Multiplus II. (these will be linked to Cerbo GX and SmartSolar MPPT 150/100)

- Should I have a CB for each battery? Or should I have one bigger CB where both batteries join in parallel together?

- Should my circuit breaker size be the same as the max discharge current of the batteries? Or slightly lower? I know that the CB is really there to protect the cabling and that these batteries have internal over-current shut-off protection but would it be better to have CB blow rather than the battery going into over current protection?

With the Multiplus II, the manual recommends a 300A fuse which is just way to big for my battery setup. So obviously my fuse would have to be smaller than this, but how much?

Also wondering if I can change settings and put a limit on the power output of the multiplus which would help with this?

FYI I will be getting 2 more of these batteries, 4 in total soon as I am aware this battery setup isn't quite big enough to use the Multiplus II at full capacity. At the moment it will only be running small loads like lights etc.

Sorry for the long question but basically what I want to know is what size CB/fuses for batteries (and should batteries be fused individually)? And what size fuse for the Multiplus II in this setup?

I have attached the specs for the UP2500 batteries. Keep in mind I will have 2 of these in parallel. Thank you!

Multiplus-IIcerbo gxPylontechfuses
up2500.jpg (111.5 KiB)
2 |3000

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Rob Duthie avatar image Rob Duthie commented ·


The max power the inverter can pull is only about 125Amps. For 4x batteries allow for about 160Amp DC breaker, which protect the cable to the inverter etc as all 4 batteries will power share anyway. As each battery will deliver 30 to 35Amps each on max load.

So one breaker will do.


Rob D


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Brandon avatar image Brandon Rob Duthie commented ·

I don't have 4 batteries yet so what size breaker would you recommend for 2 batteries?

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Rob Duthie avatar image Rob Duthie Brandon commented ·


125Amp is on the limit but the will be Ok for your small 3kw unit.

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