Auto reset fuse query on a camper trialer

Submitted: Tuesday, Jul 14, 2009 at 18:14

ThreadID: 70678 Views:3745 Replies:2 FollowUps:3

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macbushy

Here's the rundown. Camper trailer battery is charged via battery cable from aux batt under bonnet. Cable to trailer battery has 50amp auto reset fuse at aux battery end, in case of short or o/load etc.
I have nothing at the camper trailer end of the main supply cable.

If a short or o/load happens when trailer not connected to cruiser, or even if it is conected, power can still travel back from camper battery.

Question, Can an auto reset fuse (if I fit one at the camper end) have a relativley high charge flow back through it, as the protection it provides should be set up for current flowing out, not in.

Thanks in advance for even trying to understand the question.

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Reply By: Member - Mike DID - Tuesday, Jul 14, 2009 at 19:31

Tuesday, Jul 14, 2009 at 19:31

Fuse/Breaker Size needs to be based on the current rating of the cable - if the cable is rated at 50 amps, the Fuse/Breaker needs to be 50 amps or less.

Do anything else and you have a fire hazard and your insurance company may disown you.

AnswerID: 374538

Reply By: Maîneÿ . . .- Tuesday, Jul 14, 2009 at 19:34

Tuesday, Jul 14, 2009 at 19:34

I understand you have two (2) batteries with only one (1) "FUSE" between them ??

You need to add a second (auto reset) fuse at the pos (+) terminal of other battery, so that the cable attached to each (+) battery terminal is protected.

Maîneÿ . . .

AnswerID: 374539

Follow Up By: macbushy - Tuesday, Jul 14, 2009 at 19:56

Tuesday, Jul 14, 2009 at 19:56

Thanks for your concern, but the point is....or the query is.... if (or more like when ) i put another auto reset fuse on the camper trailer end, will a decent charge flow back through it to the battery.

FollowupID: 641767

Follow Up By: ABR - SIDEWINDER - Tuesday, Jul 14, 2009 at 20:43

Tuesday, Jul 14, 2009 at 20:43

Hi Mac

The fuse protects the circuit and will carry the current in both directions to its max rating.

Regards

Derek from ABR

FollowupID: 641776

Follow Up By: Maîneÿ . . .- Tuesday, Jul 14, 2009 at 23:18

Tuesday, Jul 14, 2009 at 23:18

Mac,
In the (imaginary) diagram below, fuse (1) protects the Cranking battery, because it sits on or adjacent to the Cranking battery, likewise "fuse (2)" protects the AGM DC battery, because it sits on or adjacent to the AGM DC Battery.
The distance between the batteries (fuse's) can be only millimetres, or many Metres, depending where the second battery is placed, either beside the first battery or in the Caravan or Camper Trailer with an Anderson plug in between.

If the battery cable shorts anywhere between the two fuses, BOTH fuses will blow so you will have NO current in the cable between the two blown fuses.

However, when you only use ONE fuse, the current will attempt to run from BOTH batteries to the one blown fuse, stopping only at the single blown fuse and ALSO the place where the battery cable has shorted out.

One side of the battery cable will still be *LIVE* and will continue shorting out, discharging the battery, maybe starting a fire and causing trouble.

Hope this picture shows it clearer

Image Could Not Be FoundMaîneÿ . . .

FollowupID: 641792