Fuse flows for my Renogy DC-DC 40A! Why?

Majten

New Member
Joined
May 8, 2021
Messages
8
Hi!

I've just finished my solar installation in my van conversion and everything is working well, except for the fact that the fuse from the Renogy 40A DC-DC charger blows after a few minutes, even though it's sized according to the recommendations at 50A. The charger is connected to a positive and a negative busbar, to which the three Renogy 100ah lithium batteries are also connected. Could anyone tell me why? The cable distance is super short, only about 1 foot in total. When resetting the fuse, starting the ignition and looking at my shunt statistics, it says it's transferring around 39A–40A, until it blows.

Any help would be appreciated! Perhaps it's just a bad fuse?
 

mikefitz

Solar Addict
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May 28, 2020
Messages
887
The 50 amp setting may be too low for the feed from the engine starter battery. You refer to " reseting the fuse", implying it's a circuit breaker. Low cost units are unreliable, fit a breaker from Bussman/ Blue Sea or fit a replaceable Midi link fuse with holder.

Fit a 60 amp fuse at the starter battery and a 50 amp at the service battery, in each case the fuses as close as practical to the battery positive to protect the cable .

Mike
 

Majten

New Member
Joined
May 8, 2021
Messages
8
The 50 amp setting may be too low for the feed from the engine starter battery. You refer to " reseting the fuse", implying it's a circuit breaker. Low cost units are unreliable, fit a breaker from Bussman/ Blue Sea or fit a replaceable Midi link fuse with holder.

Fit a 60 amp fuse at the starter battery and a 50 amp at the service battery, in each case the fuses as close as practical to the battery positive to protect the cable .

Mike
Thanks, Mike! Correct, it's a circuit breaker, we just use the same word for the two in Swedish.

Ok, so maybe it's a matter of poor quality. Just to be clear though, the circuit breaker breaks going from the charger to the battery – the breaker between the starter battery and the charger (60A) is doing just fine.
 

mikefitz

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May 28, 2020
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887
I am in the UK and quality breakers are expensive and not easy to obtain. The low cost units from Amazon/eBay and some suppliers are often unreliable with variations in trip values and excessive volt drops.

Mike
 

grizzzman

Some say "Why" and some say "Why not?"
Joined
Sep 21, 2019
Messages
1,104
I have a Renogy 40 amp DC to DC charger when testing it I found that if input voltage was 14.00 volts output set at 14.7 volts input amps were 50 amps and output was just shy of 40 amps.
 

Zil

Just another ass on the web
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May 27, 2020
Messages
1,331
Fuse to the cable wire gauge size, not the charge amperes. A LiFePo bank can draw the extreme maximum amperes from the charger for a few moments. I recommend a fuse as opposed to a circuit breaker.
 
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