running 12 volts from the front, to outside rear of the vehicle..

ay up.

i have a trailer with a hiab fixed to the draw bar, its a home made affair with a old tail lift pump and a 12 volt battery running the hiab.

at the moment i have to charge the battery at home which is getting to be a pain.

sooo, i want to run heavy cable from the front nearside battery to the rear cross member and an anderson connector.

i would like opinions on the best way to do this, if i should plug the hiab battery into the anderson connector and charge it or do away with the hiab battery and run off the cruiser battery for example.

cheers

I'd consider running an anderson to the rear as you suggest but put a split charger in between both batteries.

becareful with the near side battery as i have heard you might get 24v spike. please check and let me know 100% i run every thing of the drivers.

would the split charger make a mess of things if i wanted to put a anderson connector on a set of jump leads and use them off the back?

i think your right in what you say stu but i cant see the spike hurting anything on start up. my other battery is cluttered with the winch electrics..

If you're running just one wire (pos 12v) and picking up an earth at the rear of the vehicle then don't use the NS batt 'cos you'll get 24v at the pos terminal relative to earth when cranking the engine. If you're running a twin cable, pos and neg from the NS batt this should be OK but current will then be drawn from the Hiab batt when starting the engine. Personally, I'd do as suggested above and run from the OS batt (all the 12v electrics on the vehicle are connected to this) via a split charge relay.

Edit
You should still be able to use jump leads from the back via the Anderson connector but I wouldn't do it with the engine running. The split charge relay and possibly the wiring from it won't be up to handling jump starting current. If the rear batt is a bit low and you try jumping from it current will be drawn from the front batteries via the charge relay. With the engine off the Anderson connector/rear battery is disconnected from the charging system and front batteries.

The alternative rugged simple system is to take a pair from the offside battery heavy enough (35mm copper) to run the Hiab and jump leads when necessary.

Pop a big fuse at the battery, something like 200A or so, possibly more depending on the draw of the Hiab.

The next level of complexity, seeing as you have a winch, is to do a rear mounted leisure battery (possibly the one from your Hiab) in the vehicle with a split charge system, cables as above to the front for your winch and possibly split for a front mounted Anderson plus the same at the rear. That way you free up your main vehicle battery and won't ever drain it with winch or Hiab as they both run from the leisure battery.

Richard

PS, I'm considering this setup (minus Hiab) on mine. Anyone got any thoughts on linking the split charge to the 35mm pair that would run front to rear, or would the preference be to run a dedicated cable. I'm with the former (I'm an electrician BTW) but interested to hear others' thoughts.

StarCruiser said:

The alternative rugged simple system is to take a pair from the offside battery heavy enough (35mm copper) to run the Hiab and jump leads when necessary.

Pop a big fuse at the battery, something like 200A or so, possibly more depending on the draw of the Hiab.

The next level of complexity, seeing as you have a winch, is to do a rear mounted leisure battery (possibly the one from your Hiab) in the vehicle with a split charge system, cables as above to the front for your winch and possibly split for a front mounted Anderson plus the same at the rear. That way you free up your main vehicle battery and won't ever drain it with winch or Hiab as they both run from the leisure battery.

Richard

PS, I'm considering this setup (minus Hiab) on mine. Anyone got any thoughts on linking the split charge to the 35mm pair that would run front to rear, or would the preference be to run a dedicated cable. I'm with the former (I'm an electrician BTW) but interested to hear others' thoughts.

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With a separate battery in the rear feeding the winch at the front, and even an additional anderson connector, via large 35mm cables, you could just connect the charging circuit to these cables via the split charge relay but, as I said in the above post, with the engine running there's a risk of drawing too much current through the relay if the leisure battery starts to run low while winching etc. All the relay does is effectively connect all the batteries together for charging when the engine is running so if the leisure battery can't supply enough current for the winch it'll try and pull it from the front batteries through the relay 'cos that's the only link between them. Unless you can find a split charge relay that can handle >200A and connect it direct to the front OS battery then it wouldn't be a problem. JMO

You have a very valid point. It does tie in with my question on where to connect the charging cable as there is the resistance of the cables and consequent voltage difference to consider.

Durite do a 140A intelligent charging relay. Quite whether this would get overloaded is something I think I will need to sit down and calculate. At full battery charge, leisure and main, the load will be shared dependent on the internal resistances of the batteries plus the resistance of the cables. This will be lower for the two vehicle batteries as they are in parallel. If this is connected near to the winch, the charging circuit will feed this more than the leisure battery. If the charging connection is made at the leisure battery with a dedicated cable, this resistance will be additional and cause the leisure battery to deliver more current. This is my current (no pun intended) thinking.

The amount of charge current given to the leisure battery will depend on the leisure battery voltage difference from the main vehicle system. The other consideration is the time that any over current is applied.

In short, your caution is, in my view valid until calculations show what is fitted can cope, or overload time is kept to a minimum, or a suitable fuse is installed to limit the charge current. This then begs the question, what sort of spikes can be generated at the point the fuse blows? Much to ponder, hence the request for thoughts from others.

With 35mm cables I reckon the resistance and hence voltage drop from front to rear of the vehicle would be negligible as far as charging current goes. I had a 4mm feed from the front OS battery to some power sockets in the rear load area but when I tried running a small inverter pulling 8A from one of the sockets the drop was approaching 2 volts. Replacing the cable with a 16mm reduced this to virtually zero so, personally, I reckon you could connect the charge relay anywhere in the circuit without any loss of charging performance. The 140A relay you mention would obviously be overloaded trying to pass full winch drawn current but I guess, realistically, the rear leisure battery would have to be very low indeed for the winch to be drawing that much current through the relay from the front batteries. JMO

I think we're on the same page here. If a smaller but capable charging cable is connected to the battery, it could help limit the charging current drawn similar to your 4mm overload.

I will get around to calculating it on a rainy day.

I would rather not have a battery in the car. I may one day go down the route of fitting a deep cycle battery but I would convert to 12volt starting and put the battery in the engine bay. I would run 2 cables to the rear and use a split charger as has been advised.

Would drawing current from the hiab battery on starting be a problem? This would only happen when the trailer is on and I would probably keep the engine running when using the hiab.

Personally, I don't see too much problem drawing from the Hiab battery during starting. The other thought that crops up is the reason for using a split charging relay at all as (correct me if I'm wrong here) the vehicle doesn't in favour of linking the two batteries together and charging at 12v. The reasoning behind a charge relay is to prevent draining the leisure battery if there is drain on the vehicle battery. Not sure if the intelligent relays limit the charge current at all. I am only just looking into this so am rather light on vehicle split charging systems other than the basics.

I have reservations about an internal battery too, mainly fumes or possibility of, and spillages. Both of which I can mitigate. Curious to know your thoughts in case I'm missing something.

Richard

I would work out how many amps the Hiab uses at full load, then run slightly higher rated cables down from the OS battery straight to the Hiab battery via a fuse rated to carry the Hiab current but below the cables, fit a voltage triggered solenoid powered from the alternator.

Car will start via the normal batteries, trailer battery would engage and charge as the alternator starts to work, when you switch off the engine then the trailer is disconnected. Pulling the Anderson apart even with the engine running will not affect the alternator as it will continue to 'see' the car batteries. Of course with the fuse and solenoid 'Cole Hershee' for example (check spelling) rated high enough you could use the Hiab via the vehicle batteries in the event the Hiab battery fails for whatever reason, you forgot to plug it in for example .

Just get your component choice correct and unless anyone can see anything I have missed you are good to go.

regards

Dave

The only thing I would add to that is to place a fuse immediately adjacent to the battery at the Hiab end and the vehicle end, of the same value. This is assuming that the cables selected wouldn't be large enough to carry the full short circuit current of all batteries until such time as they are depleted (which is why heavy starter motor cables are not fused).

Fitting the fuses close to the battery would then prevent either battery feeding into a short circuit in the event of damage to the cables and a short circuit occurring.

Richard

Agree with that Richard, it makes sense that there could be a short from Hiab towards car.

regards

Dave

cant find any markings on the hydraulic pump motor. looking around the internet they "seem" to be about 800 watts, so 66 amps.

ive got loads of 10mm cable in the shed.. too small??

starcruiser, i dont want a battery inside the motor because of space rather than any other reason. with out looking into it im sure there are batterys suitable for this application.

10mm cable is way too small IMO. A 5m run of 25mm cable will give around a 5% power loss (voltage drop) with that sort of current draw. If you use cable much smaller than this you risk the cable itself heating up which you don't want for obvious reasons.

just to confirm towpack, do you mean 25mm2 or 25 mm dia cable?

Found the motor receipt whilst doing the tax returns. Its 1600 watt...
thanks for the replys btw.