Question on fusing for gen set starter

memilanuk

Solar Enthusiast
Joined
Apr 21, 2021
Messages
86
So... getting closer to putting things in place in the truck camper... one of which is a Victron Lynx distributor, so the only things coming off the battery terminals will be the leads to the disconnect (+) and shunt (-), and on to the bus bars of the Lynx.

Right now the factory pre-wire #2 cables for the generator (Onan 2500w) starter comes *directly* off the battery terminals, with no fuse that I can find. According to my clamp-on ammeter, peak starting current is 350-375A - for about a second or two.

Going forward, what's the best place to land those leads? If it's the Lynx distributor, what should I fuse them for? Would it be acceptable to tap off the end lugs of the Lynx, and mount a single fuse just for the gen starter, so as to get a little extra room? I'm planning to use all the spots on the Lynx (and then some) but don't have enough space for a second one.
 

HRTKD

Boondocker
Joined
Apr 24, 2020
Messages
6,498
Location
Somewhere South of Denver
On my RV trailer, there is an automatic resetting circuit breaker close to the tongue. However, the generator (Onan 5500) bypasses all that. I don't recall seeing a circuit breaker or fuse on the DC input side of the generator. Maybe the Onan service manual would say otherwise.

Because of the high amp draw of the generator's starter, I chose to retain a medium size lead acid battery on the tongue for the generator. That works for me since I have room on the tongue. For you in a truck camper, that's probably not a good solution.

Other forum members have tested the surge amps and found it to be in the low 200's. I can't capture surge amps (just max amps, which isn't good enough) so I can't say how many amps my generator is drawing.
 

memilanuk

Solar Enthusiast
Joined
Apr 21, 2021
Messages
86
I've asked around a few other places... the 'consensus' seems to be that that's just the way they come set up from the dealer / manufacturer - though it's really starting to bother me that to not know what exactly they're basing the wire sizing, etc. *on*. Voltage drop over distance, maybe?

I think I've seen a few anecdotal mentions about the start current being lower with LFP cells due to less voltage drop under load... I'm really hoping that's the case, because as you say, there really isn't room to keep a dedicated starter battery around.
 
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