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 Topic: Charging caravan battery whilst towing.
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19/10/2021 at 7:03pm
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so you have been on ehu and still your battery didnt get any charge? that suggests to me that your issue is one of the charger not working at all, nevermind whilst your towing. what is your battery reading?
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19/10/2021 at 7:06pm
Location: East Herts
Outfit: 1992 Elddis Wisp 450CT + X Trail
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That is certainly a strange one. Quite an omission on the part of the manufacturers. I wonder why?
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Colin
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19/10/2021 at 7:15pm
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you need a DC to DC charger to properly charge a van battery..
i have a renogy 20 amp one.. this basically takes voltage (whatever it gets) from the cars battery and boosts to put a controlled 20 amps into the vans battery..
the cars alternator charges the car battery..
trog
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19/10/2021 at 9:16pm
Location: Lichfield
Outfit: Coachman Amara 450
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You need to check the towing socket with a multimeter when the engine is running to see if you have a live feed from the vehicle alternator or not. If it's a 13 pin towing socket then the pins to check are 9 & 13 which 9 is the battery supply and 13 is the earth for pin 9. If you Google '13 pin trailer plug wiring diagram' you will find various diagrams to find out which are pins 9 & 13.
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19/10/2021 at 10:23pm
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the real problem is the voltage drop between the cars alternator and the vans battery.. the cable run is too long and there is never enough voltage left to properly charge the vans battery..
another problem is modern cars have smart alternators this is for economy reasons but it also stops a caravans battery from being properly charged..
trog
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20/10/2021 at 1:32pm
Location: East Herts
Outfit: 1992 Elddis Wisp 450CT + X Trail
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I can't comment on smart alternators as I know nothing about them, but wouldn't have thought there would be any problem with an "ordinary" alternator.
Many years ago I made my own split charging system, before I had even heard of such things, for my Mk2 Cortina and Sprite caravan. The Cortina had a dynamo at first too until I changed it for an alternator. It worked fine even with the dynamo, and in fact it was the only way the caravan battery got charged away from home, as few sites had EHU then and our caravan had no facilities for it anyway. I did use fairly hefty cable though.
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Colin
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20/10/2021 at 6:18pm
Location: Berks.
Outfit: Bailey Unicorn Vigo
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Re. Trogg message.
I bought a new BMW last year, previously with factory fitted tow bars they left out 2 pins i.e. charging and fridge but mine had the 13 pins. Just to make sure I checked out the relevant pins in the 13 pin socket and with the engine running there wasn't any voltage reading. I got in touch with a mobile auto electrician, he came out and connected his box of tricks. With the engine running there was no voltage reading but he then asked me to switch on the headlights and straight away there was voltage (I can't remember what the reading was). He said that is what happens with smart alternator, and advised me to keep the headlights on whenever I am towing to overcome this problem.
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20/10/2021 at 11:30pm
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Just to add to that, I always use dipped headlights when towing, anyway.
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21/10/2021 at 9:06am
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smart alternator or not the long cable length between a cars alternator and the van battery means there is never a high enough voltage reaching the vans battery to fully charge it..
a DC to DC charger remedies this.. mine is a 20 amp version but you can get bigger ones.. bigger ones do require a hefty cable running from the cars battery..
if plugged into the mains all the time none of this matters but if you want to get some real use out of the vans battery it does..
trog
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