29 replies to this topic

[pvstoy]

Under the hood near the battery look for the positive wire from the battery to the firewall and see if there is a circuit breaker, a little silver thing.  8 gauge wire then it should be a 30 or 40 amp breaker.  Should have one just before the Blue Seas separator also.

[ntsqd]

Don't get me started on OE camper wiring. Our Phoenix was a disaster looking for a place to happen before I stripped out everything and started over.

 

If FWC is using those little, metal cased breakers the odds are that they are using the auto-reset version as those are by far and away the most common version. Have to really go out of your way to get the manual reset version, and I'm not sure that those allow you to 'pop' them.

[Desert Scruff]

There is a 30 amp circuit breaker in the truck on the line from the truck battery to the camper. There is a fuse on the ground from the ACR and there is a 30 amp fuse near the camper batteries on the wire from the solar controller. The only other hot wire to/from the battery is the line from the ACR. Other than the fuse/breaker box those are the only fuses/circuit breaker I find. 

[Desert Scruff]

I cannot see any fuse near the ACR other than the one on the ground wire, which was a 10 amp fuse although the ACR installation instructions called for a 1 amp fuse. 

[ckent323]

Picking up on ntsqd's comment.

 

I think it best to use a properly sized breaker with adequately sized wire between battery banks and a re-settable type breaker rather than an automatic resetting type.

 

Something like this type:    

 

https://shop.pkys.co...ASABEgIssfD_BwE

 

 

Not this type:

 

https://www.amazon.c...p_72:1248909011

 

 

I suppose we can quibble on wire size but if you are relying on charging the camper house battery bank from the truck you may see large current flow on the order of 80 A and probably should size the wire and breakers for that.

I attached a wire size calculator spreadsheet based on short term current .  It also has a voltage drop calculation and some embedded reference tables (I have not had it independently checked so use at your own risk).

 

Regards,

Craig

Attached Files

•  Wire size for short term current.xlsx   415.35K   56 downloads

Edited by ckent323, 09 July 2018 - 06:56 PM.

[Desert Scruff]

ckent323, I assume you are recommending replacing the circuit breaker near the truck batteries, and with the wiring I have use a 30 amp breaker. Do you see anywhere else in this system that I need to add a fuse or circuit breaker, or replace what I have? I have read the topic on increasing the size of the wiring but I am keeping the gauges as is for the present.

[ckent323]

Desert Scruff, et al,

 

It is my opinion that a re-settable circuit breaker be placed between the Truck battery and the ACR and another between the house battery bank and the ACR. I believe that is consistent with the Blue Sea recommendations for installation.  It is further my opinion that 8 AWG wire is too small to run between the truck and the camper unless the camper house batteries are kept mostly charged by solar or ground power. 

 

The circuit breakers should be sized for the wire size chosen.  I used the spreadsheet for short term current to determine wire size for my truck to camper connection.  I wound up using 6/2 duplex boat cable that I ordered from PKYS. 

Based on comments I have seen in these forums I assumed a worst case of 80A for 10 min for my calculations. I think that is very conservative, maybe too conservative. 

My calculations show that for an 80 A load for 10 minutes a minimum wire size of about 5 AWG is needed,  I would have gone with 4 AWG at time of purchase but the largest duplex wire from PKYS was 6/2.  Thinking more about this since then I am  comfortable with 6/2.

I thought about how my solar has been working and how likely or unlikely it might be that I would actually experience an 80A load for 10 minutes.  That caused me to buy a battery monitor for the truck battery (I already have one on the camper house battery bank) that way I can compare differences in charge. 

I also put in the Blue Sea ML-ACR with remote along with Blue Sea series 285 80A circuit breakers (on each battery bank as described above).   The battery monitors allow me to decide how the system operates, say if the load differential is too big I will just isolate the batteries (so I don't fry the wires) until the solar brings up the house batteries.  This set-up also allows me to jump the truck battery from the camper house battery bank if I need to (jumping is less an issue because the truck usually starts with less than 6 seconds of cranking)

 

Caveat: I just finished installing all of this stuff so do not yet have real time field use on it.

 

Therefore, I defer to any comments on this from ntqsd, Rando, or Vic as I believe they are a bit more experienced and knowledgeable about this stuff (particularly since I may be too conservative).

 

 

I hope this info is helpful.

 

Craig 

 

P.S.  I did not specifically answer your question about replacing the automatic resetting breaker.  I don't know enough about their operation (yet) and it bothers me that on a circuit that could fry from over current that they auto-reset.  I want visual indications of issues (popped breaker) and ability to manually open (or close) the circuit.  I don't see how I get that from the auto-reset devices.

Edited by ckent323, 09 July 2018 - 08:02 PM.

[Vic Harder]

100 A breakers and 2G wire for me i very rarely draw down my camper batteries, but if i do the alternator can bulk charge at will

[rando]

I am not sure there is really a problem here - AGM batteries have a slightly higher fully charged voltage (~12.8) than flooded batteries (~12.6), so your house battery will carry the vehicle parasitic loads until the voltage reaches 12.75 and the ACR disconnects.   12.75V is ~95% SOC for the house battery.   I am not sure it is worth reconfiguring the system to maybe gain back 5% house battery capacity. 

 

I have a lithium house battery that has a 13.2V resting voltage, so my ACR is almost always combined - but I don't really worry about it as my solar system more than offsets the vehicle parasitic loads and in the process keeps the starting battery fully charged.   The truck roars to life even after sitting for months. 

[mhjackson123]

Thanks. That is pretty much what I decided as well. Not enough to lose too much sleep over. It would be great if I could adjust the cutoff voltage, but since I can't, I will live with it!

 

I am not sure there is really a problem here - AGM batteries have a slightly higher fully charged voltage (~12.8) than flooded batteries (~12.6), so your house battery will carry the vehicle parasitic loads until the voltage reaches 12.75 and the ACR disconnects.   12.75V is ~95% SOC for the house battery.   I am not sure it is worth reconfiguring the system to maybe gain back 5% house battery capacity. 

 

I have a lithium house battery that has a 13.2V resting voltage, so my ACR is almost always combined - but I don't really worry about it as my solar system more than offsets the vehicle parasitic loads and in the process keeps the starting battery fully charged.   The truck roars to life even after sitting for months.