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excossack

Member Since: 22 Feb 2012
Location: North West
Posts: 5894

1999 Defender 110 Td5 SW Caledonian Blue

Can you add a relay to the circuit that is ignition fed so its only active when the vehicle is running? That way you can isolate the split charge from the 12v feed and should allow the ctek to give 12v to the battery that needs charging? 1999 Defender TD5 110

Regards
John M0VAZ
Econet Station 48 no clock

4th Mar 2025 9:49am

JackNorris

Member Since: 16 Mar 2020
Location: Milton Keynes
Posts: 78

Hi all

Thanks for the replies, some great stuff there

It’s getting a bit complex for effectively me to avoid flicking a switch…

So I think I’m back to

Stick a switch in the ground of the tmax, this will stop batteries joining

I’ll then stick a ctek comfort connector on each battery and I can charge each battery independently

Could I charge both batteries at the same time if I had two ctek? I don’t see why not but.

Thanks

4th Mar 2025 10:53pm

macfrank

Member Since: 05 Nov 2015
Location: somewhere in the north
Posts: 1105

2015 Defender 110 Puma 2.2 SW Keswick Green

Two CTEKs, each to its own battery, should be fine.
Should NOT be done when the TMAX has connected them!
At best the chargers get "confused", at worst you'll get some smoke.

Reason is they control their output (voltage, current) depending on voltage and current/resistance of the battery. So each one may adjust its output in reaction to the other one.

Electrically if you connect multiple voltage sources with different voltages in parallel there will be a compensation current until all voltages are the same. With two or three lead acid batteries that's not a problem, because they have a high internal resistance limiting the currents (that's why we can charge them with our powerful, what 150A?, alternator).
The CTEKs do limit currents and have a protection against reverse currents flowing into them (when the battery's voltage is higher than the CTEK's current output voltage), but I'm not sure that'll work as planned when you connect two CTEKs.

I know that I would eventually make every mistake possible

So I use the switch and plug the CTEK into either connector. Most of the time both batteries are connected (as said MXS 10 is usually able to handle that).

5th Mar 2025 5:44pm

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