Charger in series with load

dilbert99

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Is it possible to connect a smart 12v charger in series with the load? I've got an existing PMS3 and wish to ditch the internal charger for an external one with a higher charge voltage. the PMS3 has a spare 240v output but I'm trying to figure how to wire in the 12v side.
 
I am not sure you really mean "in series with the load"?
Anyway, this is how I would - and have - connect up an external charger on a van with a PMS3 unit to use instead of the PMS built-in charger...

240V Mains Input
Connect up the mains charger to one of the 3 MCB outlets at the rear of the PMS. This wll let you turn the charger off easily from the PMS3 control panel by flipping the relevant Breaker (and so you leave the charger switch off on the control panel so the internal one does not get used).
This shows how it is connected to a PMS3H unit. The PMS3V will be the same
1588431212720.png

+12V DC Out
For the charger output to the battery, I would connect it to a suitable 12V connection that goes to the Leisure Battery.
That connection could be the same as the 12V connection that goes INTO the PMS3 from the battery, or a connection direct to the battery - whichever is most suitable for your setup
On the same installation as above, this shows the +12V Path used for this installation
1588432575934.png
The PMS3 +12V supply cable is connected to the Battery via a fusebox (this was moved to this position for this new setup)
The Mains Charger +12V output cable is connected on its own fuse in the same fusebox
The Leisure Battery +12V cable is connected to the Fusebox as the main general supply. This accepts +12V input from the Charger and provides +12V to the PMS3

Hope this explanation is clear!
 
dilbert99 said:
Thanks for the reply, I think I understand it. if I get a fuse box like this https://www.12voltplanet.co.uk/fuse-box-with-common-power-ground-buses-6-way.html. Where do I connect the negative output from the charger? to the common negative on the busbar in the fusebox?
Click to expand...
well, #1 - that is rather an expensive fusebox for a blade fusebox. unless you want the features that specific one offers.
If you are looking at the fusebox purely to add in the charger connection, then there are easier and more economical ways. connect direct to the battery (for both +ve and -ve) if the charger is close to it and/or you can route the cables easily. Get some kind of junction box/connector strip to connect the PMS +ve in, the Battery +ve supply and the charger +ve output is another alternative. It really depends on where things are located in your van to the best way to do it.
Generally, all the negatives are connected together, either on busbars, or using earthing points on the vehicle metalwork as chassis ground/-ve points.

Remember - work safely and disconnect the EHU before touching ANYTHING around the PMS - there are potential live connections exposed!
 
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