Dual battery charging systems for overlanding - Pt. 2

[@jean5110]

Thank you for clearing this up. I have always been suspicious of low amp dc-dc chargers. I really enjoy your channel and approach to your build, thank you.

[@adelarsen9776]

I only follow Roaming the Outback, The Road Chose Me and this channel. There's a sound reason for this choice. Great video Bill. Keep up the good work.

[@defendermodsandtravels]

I follow those two channels too but it seems that Brett Lewis is now giving up to concentrate on other things which is a pity. Both of those guys are very down-to-earth with no bs and the videography in Roaming the Outback is outstanding. The other guy who seems genuine and knowledgeable is Stephan Fischer of All OffRoad 4x4 Adventures.

[@adelarsen9776]

@@defendermodsandtravels Brett is busy working saving money for his next round of long range exploration. He'll be back and it will be interesting to see where he pops up.

[@defendermodsandtravels]

@@adelarsen9776 I have been in touch with him by email. I think you will find he different goals now. Ask him yourseif.

[@adelarsen9776]

@@defendermodsandtravels Hi Bill I had an email from him 3 weeks ago. I'll ask him, ok. THanks.

[@adelarsen9776]

@@defendermodsandtravels Bill, All is happy and ok.

[@deriusnorris4463]

Thank you for this very informative video. I have being toying with the DC to DC charger however have not yet installed(running solar so as yet have rarely needed to charge alternately) but have an isolation switch which I make after the main batter has reached charge so it's not perfect but solves the issue... A plus side is if the main battery is low then I can charge it via the solar panels in an emergency.

[@defendermodsandtravels]

I trust that the isolation switch which you use to connect the two batteries is suitably rated? It can see high currents esp if they are connected when you start the engine. I'm sure you are aware of the weakness of your setup. The auxiliary battery will need around 14.4V to charge but if the main battery is already charged the alternator will reduce the voltage. If the aux battery doesn't get fully charged it will start to sulphate. Good travels.

[@deriusnorris4463]

@@defendermodsandtravels yup Know the issues. Only switch on the isolator once vehicle is running and only if there is no Sun and the aux batteries are at a low discharge which is not often as in ZA the Sun shines often so it's really just to stop the batteries discharging to much(damage) the absorption will be done when the Sun pops out. Even if the camper stands for a while (not traveling) the batteries will be floated by the solar with the isolator off. However I am looking at the split charger you have, the "name brands" are silly costly. Thanks for your reply and video. Safe travels.

[@ailo4x4]

I did some research to use the Stirling diode split charger as you have (and I like the way it works) but the instructions make it very clear it is not to be used on any modern vehicle with an ECU. My vehicle has an early 5-wire ECU but it is an ECU nonetheless so I think I might end up having to use a DC-DC charger in the end. I am using a Redarc smart battery isolator at the moment. I'm upgrading my alternator to a 140amp unit and my current isolator is only rated to 100amp. So, back to the drawing board for me!

[@defendermodsandtravels]

I fully agree with your comments about the ECU and you don't want any sort of invasive mods. I am intrigued why you need a 140A alternator, unless you have a large electrical set up. There are rules for maximum charging rates for conventional batteries and you couldn't use the power of such a large alternator (or do you have Li batteries?) The one argument in favour is that if you de-rate equipment it tends to be more reliable; the charge controller would however need to limit the current draw to

[@ailo4x4]

@@defendermodsandtravels I do have Li batteries in my expedition camper trailer and I want to be able to charge them completely while driving. But I also have second Optima AGM battery in the truck (same as my start battery, both Optimas) for running the air compressor, winch when installed, etc). Redarc sent me diagrams on how to wire the truck for AGM house battery in the truck AND charge Li batteries in the trail. It involves 2 DC-DC chargers (of course!), one for the truck and one in the trailer. Do I really NEED 140a? Probably not but I come from the old school where it was best to have as much as possible. Maybe that time has passed. But I am still trying to figure out how to charge both the truck aux battery and the trailer Li batteries. I'm sure that I will absolutely need a Victron DC-DC unit for the trailer. Any thoughts?? Many thanks!!

[@overlandready]

Totally agree re dc-dc inverter chargers. THere are only really 3 times you would actually need one, 1, certain batteries that require a higher voltage output than the alternator can supply or the start battery can safely handle, 2, smart alternators where a VSR would disconnect and 3, trailers or other applications that there is excessive volt drop. Diode split chargers were all the rage in marine systems but because of the volt drop issues they were left by the wayside years ago. For all constant voltage alternators, a simple relay split charge whether alternator or voltage driven is more than adequate. As I understand the Stirling Power unit is just a delay timer to the aux battery, and to be fair, unless it is constantly disconnecting to no load there is no way it can sufficiently assess the battery condition over the alternator voltage, which incidentally should be adequately over any existing batter voltages so removes backdraw from one battery to the other. Pepole forget that the charge voltage exceeds the battery voltage so effectively isolates both batteries from them drawing capacity from the other bettery, unlike when there is not a charge voltage applied.

[@ailo4x4]

I know you are travelling just now but when you get a moment could you explain how you wired the switched voltmeter? Many thanks and good travels!

[@defendermodsandtravels]

Hi it isn't a difficult mod. You need a digital voltmeter with the negative terminal grounded to to a good earthing point. You then need a positive cable from both batteries going to a single pole / two way toggle switch (break before make to ensure the two batteries don't become connected instantaneously). The central terminal of the switch goes to the voltmeter +'ve. This way you can connect either battery to the voltmeter. The current taken will be low so a 0.75mm2 cable will suffice. I hope this helps.

[@Predator27007]

Hello Bill. The vehicle I have came with the Swiss IBS Dual Battery System already installed. Did you come across this system in your search?

[@defendermodsandtravels]

No I haven't seen it in the UK

[@BittnerBuddenbrock]

Would you use the same set up for your Discovery? I have a 1998 Discovery 300Tdi and would like a dual battery system along the same guidelines which you have pointed out in your video. Thank you very much for your reply.

[@defendermodsandtravels]

This is a more complicated question than you might think. I too have a 1998 Disco 300 Tdi although I have done little work on it myself and leave that to others. I think that model may have a 100A alternator with an integrated controller? I could look at mine but I am occupied on other matters now. My response to your question will depend on the alternator and its controller.

[@Maedetto]

Great video as always. Thanks! One note is: as soon as the alternator increases the voltage to 14.0 v to charge, the relay will allow charge of the second battery thus charging both batteries equally. Wasn't that something to avoid due to the different charge state at any point in time?

[@defendermodsandtravels]

Absolutely. You are reiterating one of the central themes of the video. Relay based split chargers have their place (simplicity, ruggedness) but the charging performance is far from ideal.

[@Maedetto]

@@defendermodsandtravels I see, i missed that it was your final goal. Thanks for the reply and sharing.

[@defendermodsandtravels]

@@Maedetto Yes. I firstly introduced the SmartBank dual charge controller which trumpets its fancy electronics etc but the smart box still only controls a large relay and hence forces the two batteries to charge at the same voltage, and for this reason I didn't buy one. I then introduced the Sterling ProSplit where both batteries are monitored and controlled independently although battery 1 always takes precedence - this is what I finally bought. It seems to work very well. I hope this clarifies.

[@Maedetto]

@@defendermodsandtravels Certainly does. Thank you for the clarification.

[@peterpontikos3786]

'simple can be harder than complex' Plato

[@defendermodsandtravels]

I like simple, light and efficient as you may have detected from this channell

[@peterpontikos3786]

@@defendermodsandtravels concur