Correct wiring and battery set up advice needed

**the evil twin** · 15th February 2015, 11:47 AM

I have made a few guesses about your setup in coming up with the following suggestions
The main factors you mention for sure are-
That you have an Oven and Sine Wave Inverter (both use high current when they are running)
That a DC-DC charger is not in the budget at the moment.
A 90 amp Alternator is used (not much advantage in a bigger one anyway really)
You have 180 watts of Solar for camping that must have some sort of Reg already
Not sure what you have for the 40

Sooo,
I would do the following
-keep the basic Isolator under the bonnet
-in the existing leads that supply the rear (3rd) battery disconnect the battery and fit an Anderson Power Pole or mini Anderson or similar plug.
-remove the rear battery and for whenever you need it make a small fly lead for it that plugs into the Anderson.
-keep the existing power distribution to accessories in the rear however you have it set up so it runs on the under bonnet aux if the 3rd battery isn't fitted.
So far you have spent about $10
- not sure what you have with the 40 or what you intend but if it is going on the vehicle permanent then a cheaper PV reg will be all you need for floating the batteries
Maybe $30 so that is $40
- keep the 3rd battery charged up at home on a decent mains or solar charger (use the 40 panel and reg if it isn't on the truck) every week or so
- regularly (once a monthish) and after any major use of the Aux put a mains charger on the vehicle for 24 hours or so
- if it is feasible and you can use one reg and swap it between the 40 and the 180 panels then even better.

Remember, a Solar Panel and Reg is a DC/DC charger so use it whenever it is available

Advantages to you
Cost
Simplicity
Versatility
The aux's will charge quicker to 80%-85% off the Alternator than a DC/DC if they are well down on charge

Disadvantages to you
You need to remember to isolate the Cranker and reconnect the Aux/s
You may lose a small amount of battery capacity (maybe 10% max) in some circumstances of low solar availability and higher power useage

Hope that helps

**BigRAWesty** · 15th February 2015, 12:14 PM

Originally Posted by the evil twin

I have made a few guesses about your setup in coming up with the following suggestions The main factors you mention for sure are- That you have an Oven and Sine Wave Inverter (both use high current when they are running) That a DC-DC charger is not in the budget at the moment. A 90 amp Alternator is used (not much advantage in a bigger one anyway really) You have 180 watts of Solar for camping that must have some sort of Reg already Not sure what you have for the 40 Sooo, I would do the following -keep the basic Isolator under the bonnet -in the existing leads that supply the rear (3rd) battery disconnect the battery and fit an Anderson Power Pole or mini Anderson or similar plug. -remove the rear battery and for whenever you need it make a small fly lead for it that plugs into the Anderson. -keep the existing power distribution to accessories in the rear however you have it set up so it runs on the under bonnet aux if the 3rd battery isn't fitted. So far you have spent about $10 - not sure what you have with the 40 or what you intend but if it is going on the vehicle permanent then a cheaper PV reg will be all you need for floating the batteries Maybe $30 so that is $40 - keep the 3rd battery charged up at home on a decent mains or solar charger (use the 40 panel and reg if it isn't on the truck) every week or so - regularly (once a monthish) and after any major use of the Aux put a mains charger on the vehicle for 24 hours or so - if it is feasible and you can use one reg and swap it between the 40 and the 180 panels then even better. Remember, a Solar Panel and Reg is a DC/DC charger so use it whenever it is available Advantages to you Cost Simplicity Versatility The aux's will charge quicker to 80%-85% off the Alternator than a DC/DC if they are well down on charge Disadvantages to you You need to remember to isolate the Cranker and reconnect the Aux/s You may lose a small amount of battery capacity (maybe 10% max) in some circumstances of low solar availability and higher power useage Hope that helps

What about the mixing of chemistry between 2nd and 3rd batteries??

**Cuppa** · 15th February 2015, 12:20 PM

What follows is for your consideration, as usual it just my flow of thoughts so may or may not be as coherent as I’d like.

Macca is correct when he suggests ya gotta spend some money to get an ideal/efficient system where you know it will ‘just work’.

That said you do have a system you can use even if it is less than ideal & is inefficient. If I’ve understood correctly you have a collection of batteries of unknown condition & remaining capacity by virtue of their past life, but sounding likely that they have been abused & are not in the greatest condition. If that is so, then the aim is just to keep them going until you can afford new batteries. Luckily what they need to keep them going as long as possible is the same as what a new set of batteries will need to ensure a long life.

One thing I will emphasise - DO NOT BELIEVE ANYONE who tells you you can ‘flatten’ any battery, deep cycle or not, & then recharge it...... at least not if you want your batteries to last. Letting your batteries get down to the point where the fridge cuts out or the inverter low voltage alarm sounds is seriously bad for your batteries health. I repeat do not believe anyone who says different, regardless of whether they are a fridge manufacturer or the bloke who claims his batteries are just fine doing so (ask him in 12 to 18 months time why he’s bought new batteries). Discharging batteries to 40% to 50% is the go. That means not below 12.1v or 12.0V at the lowest!

There is nothing wrong with having the third battery in the back as you have ...BUT.... you need some seriously heavy cable between the aux under the bonnet & the aux in the back. (Consider that ‘standard’ battery cables under the bonnet ar 35mm2 - the greater the distance between batteries the heavier cable required) The idea would be to allow sufficient current flow between the under bonnet aux & the rear aux so that they effectively charge as a ’single’ battery. If the cable is not heavy enough much of the ‘charge’ to the rear will be lost in warming up the cable. Bigger is better but can get very expensive. I used 70mm2 cable in my front to rear setup not cheap ........ unless you know of a source of used heavy duty welding cable. Move the rear battery closer to the front if you can to reduce cable length. You can use the chassis for earth, but this is less reliable than direct cable.

You will have read about my thoughts on installing Dc to Dc chargers. Generally I consider them to be a good thing because of their ’multi stage’ charging capability (aka ’smart charging’). At risk of being boring by repeating myself, their advantage is they have the capability of charging batteries to 100%, alternators alone will not do so in everyday use. The point is that if you can’t charge your battery to 100% (& can only discharge it to 40% to 50% if you want it to last) this is significant. Smart charging can as much as double your ‘useable capacity’. Batteries which are only ever charged to 70% to 80% (which is what an alternator or any ‘dumb’ charger will do) will not last so long. 4 years is an average life of a starter battery - smart charged deep cycle batteries commonly see 10 years.

There are alternative ways of ’smart charging’ aux batteries other than DC to DC chargers. Whether they are cheaper depends upon what you already have or can get at reasonable cost.
1. All solar regulators will be smart chargers. ‘Bulk charging’ the batteries from the alternator & then ’topping them up’ from solar is quite a reasonable option. I wouldn’t worry overly about MPPT but I would suggest you use a regulator better than the pieces of crap that commonly get supplied on the back of panels, also the regulator should be close to the batteries & be preferably temperature compensated. These things make a difference to how much of the panel’s output gets’s squeezerd into you batteries rather than wasted. Little differences are cumulative.

2. If you have an inverter & a multi stage mains charger, you can set up your own version of a dc to dc charger. Not quite as efficient, but used widely in motorhomes before dc to dc became commonplace. Essentially you run the inverter (modified sine wave is ok & cheaper than pure sine wave) off the crank battery, plug the mains charger into the inverter & charge the aux from the mains charger. The ‘risk’ with this set up is that when driving you have a cable (between inverter & mains charger) which is live 240v. The risk is in an accident situation - if this cable were shorted to the vehicle body it could electrocute someone - possibly the SES bloke who has come to cut you out of the mangled wreck, possibly occupants of the vehicle. The generally acceted way to mitigate this risk was to place the inverter & mains charger very close together to keep the 240v cable as short as possible (& to armour it if possible). There would still be plenty of motorhomes getting around with this system.

All of your batteries will be lead acid, but among these you may have a mix of wet, AGM or Gel. Not ideal, but I had wets & AGM’s paralleled for years without problem - so I wouldn’t worry about that. Different if you have a Calcium type (also lead acid) battery though.

DO NOT smart charge a wet battery INSIDE the vehicle. When wet batteries are fully charged they will bubble & gas - inside the vehicle this stinks as well as representing an explosive risk. Using AGM or Gel batteries inside is ok.

If smart charging a wet battery it will need regularly checking & topping up with distilled water or it will dry out (a surefire method of battery killing too).

EDIT. I see ET has posted whilst I’ve been writing, so I’ll nw have a read of his stuff to see if we are or are not in agreement. LOL. There’s always more than one way to skin a cat!

**the evil twin** · 15th February 2015, 12:25 PM

Originally Posted by biggqwesty

What about the mixing of chemistry between 2nd and 3rd batteries??

If one of the batteries isn't full Calcium, Lithium or other exotic technology it won't matter as worth a damn

**Bloodyaussie** · 15th February 2015, 01:25 PM

Originally Posted by the evil twin

I have made a few guesses about your setup in coming up with the following suggestions
The main factors you mention for sure are-
That you have an Oven and Sine Wave Inverter (both use high current when they are running)
That a DC-DC charger is not in the budget at the moment.
A 90 amp Alternator is used (not much advantage in a bigger one anyway really)
You have 180 watts of Solar for camping that must have some sort of Reg already
Not sure what you have for the 40

Sooo,
I would do the following
-keep the basic Isolator under the bonnet
-in the existing leads that supply the rear (3rd) battery disconnect the battery and fit an Anderson Power Pole or mini Anderson or similar plug.
-remove the rear battery and for whenever you need it make a small fly lead for it that plugs into the Anderson.
-keep the existing power distribution to accessories in the rear however you have it set up so it runs on the under bonnet aux if the 3rd battery isn't fitted.
So far you have spent about $10
- not sure what you have with the 40 or what you intend but if it is going on the vehicle permanent then a cheaper PV reg will be all you need for floating the batteries
Maybe $30 so that is $40
- keep the 3rd battery charged up at home on a decent mains or solar charger (use the 40 panel and reg if it isn't on the truck) every week or so
- regularly (once a monthish) and after any major use of the Aux put a mains charger on the vehicle for 24 hours or so
- if it is feasible and you can use one reg and swap it between the 40 and the 180 panels then even better.

Remember, a Solar Panel and Reg is a DC/DC charger so use it whenever it is available

Advantages to you
Cost
Simplicity
Versatility
The aux's will charge quicker to 80%-85% off the Alternator than a DC/DC if they are well down on charge

Disadvantages to you
You need to remember to isolate the Cranker and reconnect the Aux/s
You may lose a small amount of battery capacity (maybe 10% max) in some circumstances of low solar availability and higher power useage

Hope that helps

Ok this is what I have done for now.... all your assumptions are correct and I have basically done everything you mentioned.

I already had an anderson plug set up so only made minor changes there.. the 40w has a reg and I am using the 40w on the cranking battery and the 180w on the aux right now charging the car.

I already had the larger gauge wire running through the car as I was warned about voltage drop over a long distance.

The power from the aux is going into a junction that is feeding the accessories at the back plus the inverter and I have redone the earth as I had my doubts.

I cannot see me spending the money on a redarc and will probably buy one of those Ctek jobs when I can afford it but for now I think this set up will get me through as I think I may need a good battery charger at home or will the panels do for now?

I had the intention of running the 40w on the roof but for the sake of safety of my cars it is now parked where the roof rack must come off and is only put on when really needed.

Thanks so much for the help so far I really appreciate it.

**threedogs** · 15th February 2015, 01:32 PM

why not use your panels free power .
I have a 20watt panel the does my lighting and radio in the back yard,
Then I make sure that battery pack is full and take it away for camp lights.
Never ran out of 12v power yet at camp
I take it you only use the Travel Buddy on the move they
draw a hell of a lot a power to be used stationary

**the evil twin** · 15th February 2015, 01:52 PM