Anderson Plugs & Electrical Specs

the caravanners forum has a lot of info on that

We have the standard sized Anderson Plugs, that will allow about 6mm diameter cable to just fit inside them.
I bought mine from an Auto Electrician in Katherine while on our recent trip and they recommended that the cables be soldered into the end pieces. They did this soldering by removing the plug section out of the plastic holder, then placing it in a vice and while heating it filled it with solder. They then inserted the cable into the plug.
On the end nearest to the batteries in both the vehicle and the caravan they supplied 50amp circuit breakers, in case of a short circuit.

I know the experts will say that the alternator doesn't read the van batteries voltage when detirmining what rate to charge at, but in our case, I have found that the F250 quickly supplies sufficient charge to fully charge the caravan batteries, and keep them charged while the engine is running.

I think it was money well spent, buying and installing the Anderson Plug with the heaviest cable that will fit into the end terminals. Remember that the heavy cables are required for both positive and negative terminals.

Dusky,

I'm no electrical engineer or electrician but have some experience with vehicle (and my BT) wiring ....

Lets explore the Andersen plug ....

Firstly ...charging BT batteries via the vehicles single alternator is certainly not ideal and is really a "not first choice" way to do it. As a back-up or emergency way to charge ... yes maybe ..if set up right.

Secondly .... it says in your post ...to ensure the batteries can be charged while on the move. This assumes the batteries will be down before taking off ? Can you give some details on why the batteries would be down ....large inverter, microwave use, large entertainment system, too much shade over panels, overcast weather, south in winter, not enough solar panels etc etc.

There are two problems charging the BT's batts from the single vehicle alternator.

1. The alternator duty cycle.

An alternator puts out a constant voltage and varies its current (amps) to charge a battery. With a single battery (or secondary vehicle battery nearby) the alternator brings the battery up to about 70% charged very quickly then drops its amps markedly and takes a long time to bring the battery up to a 90% state of charge. This means the alternator cuts back it output reasonably quick so it stays relatively cool. The time its spends doing this ...from small output (battery charged) to large output (battery down) and back to small output (battery charged) can loosely be called its duty cycle. The average vehicle alternator has a continuous duty cycle of around 60-70% of its rating. If you ask it to maintain an output any higher for a long period of time you will kill it very quickly from overheating.

Placing 4-5 batteries on this charge circuit effectively forces the alternator into a continuous output (duty cycle) ..this stands to reason as the alternator is rated for the vehicle, it battery plus maybe one other ...and the vehicles electrical load. It is not meant to charge an extra set of batteries (especially of a different size and type) 10 metres away from it.

An easy illustration is the alternator is your garden hose turned fully on ...its output is rated at a max like the amount of litres of water the hose is giving. Much quicker to fill one bucket (vehicle battery) than five buckets (one vehicle, second vehicle, three in BT. The buckets are also different sizes (battery size) and types (differing internal resistances).

2. Voltage Drop.

An alternator puts out a constant voltage of around 14.35v which is enough to charge a battery very quickly ... especially say an AGM with its low internal resistance and capacity to take high current (amps).

The further away the battery from the charge source (long cable runs) the lower the voltage becomes .... if the run is too long for the cable size used ...by way of resistance, the voltage might be only 13.8 ish which will only float charge a battery ...and take ages ..especially multiplied by three (BT batteries).

So the cables have to be sized accordingly for an acceptable voltage drop. I only like a .15(good) to .25(max) (150mA -250mA) drop. This keeps the charge voltage originally at 14.35v to only drop to 14.2v ish ...still an acceptable charge voltage.

I'm not saying dont do it but I'm saying its not the ideal way to the charge battery systems in our rigs. If you want to do it as a primary charge source ...the best way is a second alternator (large enough for 3 batts) to charge the BT batteries only. To stop the voltage drop the cables would have to sized to suit or an adjustable voltage regulator/controller placed in the circuit. This allows you to adjust the voltage up until you receive the correct charge voltage at the battery terminal. The right voltage is specified by the battery manufacturer.

I have an Andersen plug I can connect but its only a back-up system. My alternator is a 200 amp jobbie with a high duty cycle so I can get away with it.

I increased my solar capacity (from 2 panels up to 4) as a first line of defence against overdischarging my batteries. Then .... my Honda genny with my Victron 4 stage (adjustable) fan cooled, temp compensated, battery overheat protection probe, battery charger running off it as a second choice. Andersen is third but in all honesty I've never connected it ... the electrical load in my BT is low though .... have 4 panels and 3x 110 amp AGM's.

As an example of my solar capacity the battery charger was not even plugged in let alone turned on at Copeton.

Hope this helps a little ....

Regards
Anthony

Anthony,
Far be it for me to challenge such a well thought out answer but the reason I would connect up the batteries via anderson plug cable (size yet to be determined) would be to allow the solar panels to top up the vechicle's batteries and vice versa. I am chosing a system from Rotronics which allows for solar panels on van and was told by Rod Street to connect my auxillary to van's battery to allow a two way flow of power. Hope this is a good idea?!
regards
macka

Anthony,
I agree was thinking perhaps a regulator of some sort
regards
macka

Thankyou everyone for your comprehensive replies. The intent is to have the Anderson plugs to use as a back up power source to assist the solar. But I do not want to jeopardise the BTs’ battery’s life. Anthony's well thought through response has now made me rethink this approach. I was planning on having 4 solar panels but am now thinking of going to 3 and having a portable solar panel that can be connected if the BT is in the shade. My power requirements would only be for the standard BT lights, TV and 180 ltr fridge. Was not even thinking of running an inverter, not even to charge madams mobile (which would be a considerable saving in call charges. But then is my sanity worth that much!! Better rethink a small portable inverter!).

Thanks, Dusky