Electrical Does car charge caravan battery while driving.

Rayden

New Member
Jun 19, 2021
5
3
3
melbourne
I have just purchased a 2017 Jayco Starcraft 19' caravan that does not have a solar panel. It seems that the caravan battery can be charged from the car while driving, as noted in the ST-III manual. As we spend some nights not in caravan parks running on battery power, we really need to know whether the battery will be charged when we're driving to the next destination. Is there a way to determine whether the caravan battery will be charged from the car while driving? It's not easy to see the back of the ST-III box (without major work).
 

Boots in Action

Well-Known Member
Mar 13, 2017
2,053
1,804
113
Ferny Grove, Queensland
I have just purchased a 2017 Jayco Starcraft 19' caravan that does not have a solar panel. It seems that the caravan battery can be charged from the car while driving, as noted in the ST-III manual. As we spend some nights not in caravan parks running on battery power, we really need to know whether the battery will be charged when we're driving to the next destination. Is there a way to determine whether the caravan battery will be charged from the car while driving? It's not easy to see the back of the ST-III box (without major work).
Hi @Rayden , and welcome to the forum. In answer to your question, the answer is not that simple. The Setec Series III does mention that the AUX input is for connection to tug, but there are problems with that. Firstly, if you have a Gel battery, recommended charging voltage for optimum charging is around 14.3 volts, a level the Setec cannot achieve at only 14.05 volts. If you have an AGM battery, that type requires around 14.7 volts optimum. You can still get some sort of charge from your tug but this will be limited by the charging voltage you can get from tug to van battery after losses in cabling. In addition, modern alternators ("smart") do NOT properly charge auxiliary batteries. See attached. The only way to really do that task successfully is to have a DC to DC charger fitted between the alternator and van battery. This raises the voltage from tug alternator to a higher voltage to charge van battery at optimum levels for proper charging. There are a lot of posts on this on previous posts.Check battery charging requirements on side of van battery.
 

Attachments

  • AGM Battery Voltage-Charging_0002.jpg
    AGM Battery Voltage-Charging_0002.jpg
    318.5 KB · Views: 282
  • battery charging stages.jpg
    battery charging stages.jpg
    366.9 KB · Views: 273
  • Alternators and charging voltages .pdf
    1.1 MB · Views: 311
  • Alternators and charging voltages 2.pdf
    957 KB · Views: 244
  • P1120266.JPG
    P1120266.JPG
    295.8 KB · Views: 325
Last edited:

Boots in Action

Well-Known Member
Mar 13, 2017
2,053
1,804
113
Ferny Grove, Queensland
I have just purchased a 2017 Jayco Starcraft 19' caravan that does not have a solar panel. It seems that the caravan battery can be charged from the car while driving, as noted in the ST-III manual. As we spend some nights not in caravan parks running on battery power, we really need to know whether the battery will be charged when we're driving to the next destination. Is there a way to determine whether the caravan battery will be charged from the car while driving? It's not easy to see the back of the ST-III box (without major work).
Sorry @Rayden , forgot to include photo of an AGM battery.
 

Attachments

  • P1120268.JPG
    P1120268.JPG
    222.7 KB · Views: 197
  • P1120268.JPG
    P1120268.JPG
    222.7 KB · Views: 197

mikerezny

Well-Known Member
Sep 11, 2016
1,630
2,728
113
Mount Waverley, VIC
Hi,
further to the good information provided by @Boots in Action: An alternative to working out if your 12-pin socket on the car is wired correctly to charge the battery on pin 2 ( common standard can be that pin 2 is used for reversing lights), determining if you have a smart alternator or not, and also possibly having to fit an expensive DC-DC or equivalent: consider buying an inexpensive 100W portable panel / solar blanket and regulator and connect it directly to the battery terminals of the van battery via an inline fuse fitted close to the battery terminals.

take care
Mike
 
  • Like
Reactions: Boots in Action

Drover

Well-Known Member
Nov 7, 2013
12,723
19,450
113
QLD
To find out if your tug/van connection actually works the simple way is to connect up your van, leave engine running, turn the van battery switch in van to OFF, if no switch disconnect it and then turn a light on, if it works your connection is good...if not then you tug may not be wired up... note the fridge will only run on 12v when engine is running it will not run on van battery. No 240v then fridge runs on gas.
Your Setek will charge your batteries good enough for general use.
 

jazzeddie1234

Well-Known Member
May 19, 2016
606
729
93
Mandurah
I have the drifter battery / water tank display in mine so a quick look at the current going in tells me the car is charging - between 3 and 6 amps from memory but it depends on how flat the battery is. You have to drive a long way to charge a battery at that rate!
 

Boots in Action

Well-Known Member
Mar 13, 2017
2,053
1,804
113
Ferny Grove, Queensland
I have the drifter battery / water tank display in mine so a quick look at the current going in tells me the car is charging - between 3 and 6 amps from memory but it depends on how flat the battery is. You have to drive a long way to charge a battery at that rate!
Yes @jazzeddie1234 , and it also depends on the voltage you are getting with that current as to how fast the battery will charge also, as you and I know while trying to use a LTC3780 to boost voltage for AGM to charge. Yes, I have received my units and are still testing same. More on that when I send you a PM.
 
  • Like
Reactions: jazzeddie1234