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Steve avatar image
Steve asked

Victron Battery Balancers in Series/Parallel 48V System with String Fusing

Hi Guys,


I am looking to setup a 600A/h battery bank consisting of 12x 200A/h SLA solar batteries in a series/parallel configuration to create a 48V system. i.e. Three parallel strings of 4 batteries in series.

I would like to use Victron battery balancers as per Victron recommendations to keep the bank evenly charged/discharged. i.e. Three balancers with mid-point interconnecting link cables.

I also want to use string fusing to keep the arc blast potential as low as possible. This is not inter-string fusing in the middle of the string, but rather fusing the +ve and -ve at the source/end of each string. I plan to use Bussman 160A sitched fuse disconnectors for this string protection.

My question is, what is the overall effect of having the mid-point interconnecting cables and battery balancers when using string fusing ? As there is multiple parallel paths for current, is this string fusing not recommended when using interconnecting cables and battery balancers ?

I would like to use 50mm cables for all string wiring and interconnecting links. Then after each string fuse protection, bring the three strings to either a DC busbar or straight onto a Bussman 400A switched fuse disconnector. Then 2x 95mm cables from 400A disconnector to Victron 48/10000/140 Quattro inverter.

I have most of my system worked out so far but am a bit unsure of these interconnecting mid-point links in a system with string fusing.

Any help would be greatly appreciated.

TIA

battery charging
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1 Answer
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janieronen answered ·


Hi

You have quite the same kind of setup that I have built. My design is 24V and three 5kva multis. 16pcs SLAs in 4 strings create an 8P2S bank with one balancer.

The difference is that I used for the strings also a busbar(5mmx25mm=125mm2) and not used string fuses. Someone may have a better answer, but I think string fusing with SLAs does not have that many benefits and downside because all fuses are with littlebit different resistance. What may lead that your battery balancers do need to cover that potential difference.

I have used main busbars 10x30=300mm and all multis connected with 2x70mm2=150mm2 evenly distributed to the main busbar. Plus side of multi has 400amp bussmann CF8 fuses what the only fusing I have is. That makes installation very neat, looking as bussmann CF8 goes between the busbar and the cable lug. Bussmann CF8 fuses have the lowest resistance from my experience

Victron Wiring unlimited manual advises not to use smaller string cables. Your idea about the smaller string cable cross sections and string fuses applies very well to the small Lion cell structure but not may be best for the large capacity and peak current SLAs. It will most likely work but not maybe the best approach. Hope that helps :)

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