Dual battery charging systems for overlanding - Pt. 1

[@desertdog1664]

I cant believe there are so few views for an excellent informative channel backed up by science, engineering and experience. Thank you for sharing your advice.

[@defendermodsandtravels]

Aah if I was chasing viewers I'd make videos about unboxing expensive and useless accessories :-)

[@brianhoskins1979]

3:50 I am confused about this. My understanding of a typical alternator is that it produces an unregulated A.C. voltage which is then fed into a diode pack to convert it to an unregulated D.C. voltage, and subsequently it is fed to a regulator which is usually internal in the alternator such that the final output from the alternator is a regulated D.C. voltage of approximately 14V. Now the trouble is, that is a _constant_ voltage. So it cannot possibly apply the charging scheme you described, even though the scheme you described _is_ the correct way to charge a lead acid battery. In order to apply the scheme you described, the constant voltage regulated output from the alternator would have to feed a charging middleware which then supplies the correct scheme to the lead acid battery, using a combination of constant current and constant voltage charging stages and maximising the battery's useful life. My thinking is that in all standard vehicles (except maybe more recent vehicles) it's just a dumb system that uses the alternator to apply a regulated voltage to the battery. And that's it. So if you completely flatten your battery so that it only has 9V open circuit voltage at its terminals, and then you get your vehicle started by some other means, the alternator is going to regulate to ~14V and once your battery gets charging properly it's going to consume a heck of a current, leading to a fairly brutal charging cycle. Eventually it will all get figured out and you will arrive at the charged status. But the battery will have been battered. This is the way I understand that most charging systems work on older vehicles. Dumb systems that focus on simplicity rather than protecting the life of the battery. Am I missing something? Do you have some middleware in your vehicle that takes care of applying the proper charging sequence you described? You know, if you _do_ have that middleware than you effectively have a DC-DC converter solution.

[@defendermodsandtravels]

Hi and thanks for your detailed comment. If you watch Pt. 2 you will see that the "middleware" is provided by a Sterling smart charge controller (there are others available too). You are correct that the effect is somewhat the same as a good DC-DC charger however this achieved through a different route. The principal advantage of a DC-DC charger is that it's non-intrusive so it can be fitted to almost any vehicle and shouldn't affect the warranty. The disadvantages are they are expensive and usually only provide a modest charging current (although I think more recent models provide quicker charging). There are also some reported faulty designs which manage to discharge the main battery under certain conditions - see the 4Xoverland YT channel for details. For overlanders who want simplicity and reliability there are attractions in having a dumb charge controller with a voltage sensitive relay for a dual battery system however the charging cycle is far from ideal, as you have highlighted in your comment. For me the advantages of a smart charge controller and split charging system outweigh the risks caused by the increased complexity. In case of problems I have a pre-installed spare charge controller and I can charge the second battery by hard wiring it to the starter battery - this is enough to get you to safety where the problems can be sorted. The technology of smart chargers is quite mature these days - almost any mains charger uses this technology. I hope this helps.

[@ryanleathers9025]

Thanks for the video... would love to see what you did in part 2

[@defendermodsandtravels]

I did a Part 2 video but I wasn't satisfied with it so I took it down. I am now nearing the end of a major electrical upgrade and my next task will be to record this on sveral videos. The dual charging system will be part of this. I now have the benefit of experience of using the new system - v. good too (and BTW it isn't a B2B charger). Please be patient.

[@blessedbackpacker222]

song in start seems like Indian.

[@defendermodsandtravels]

Nope Spanish. They were excellent.