Charging Gremlins

**AndyG** · 3rd January 2016, 12:36 PM

I have an MY15 Defender with two batteries, second being deep cycle
They are joined with a CTEK D250S
Today i was charging them with a Ctex MXS 5.0, + to Battery A and - to Battery B
After some hours i heard a load beeping, coming from, i think , the D250S. Nothing i can see mentions beeping as an error alert.
Prior to unplugging the MXS 5.0 Battery A was 15v and Battery B was 13V
A quickly dropped to 13 v once the charger was removed.
Recond mode will go as high as 15.7
Do i have a faulty charger as it should have gone into float mode ? But was on recond.

DiscoMick · 3rd January 2016, 06:10 PM

13 volts is fully charged (actually 6 x 2.1 volts). Anything over that is a surface charge which disappears when the battery is placed under load.
Does the manual for your charger have a table showing charge levels? Does the manual explain the beeping?
Why did you have the + and - connected to different batteries? Better to connect them both to battery A and when charged to about 80% the C-Tek should connect them and the charge flow to battery B, I think.
Once charged your charger should go into float mode and regularly test to see if the battery's charge level has been drained.

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**Dorian** · 3rd January 2016, 06:42 PM

Originally Posted by DiscoMick

Why did you have the + and - connected to different batteries? Better to connect them both to battery A and when charged to about 80% the C-Tek should connect them and the charge flow to battery B,

x 2, I,ve got a sidewinder and it joins the 2nd battery once the primary is up to 13.4V (ish). Then both batteries charge up and onto float mode. Sometimes the charger errors before it gets to float mode as the two batteries go over the chargers in built time limit.

Edit - having thought about it, it wouldn't matter where the -ve is as they are all connected , still your battery controller should close once the main is up and allow the house to charge

If the voltages were different before unplugging then your dual battery controller is not happy

**AndyG** · 4th January 2016, 06:00 AM

Why -ve on the second battery, something i long pondered,
1/ rule of thumb, connect nothing to the main battery -ve
2/ its all one big -ve circuit
3/ thats where the auto electrician put it when he installed the Ctek etc

Neither Ctek manual mentions beeping

BTW i have now set it up for 5 hours charging a week whilst overseas, that should keep it reasonably happy

DiscoMick · 4th January 2016, 09:04 AM

Some cars, I believe including D4s, can't be connected to the negative on the battery when jump-starting, but have to go to a point on the chassis, but I don't think that's true for the Defender.
Our camper trailer has a built-in multi-stage charger and we leave it connected fulltime when at home without any issues. The fridge is running and when it draws a bit of power, the charger tests the battery and puts it back and then goes into float mode, no worries.
I understand your concern about leaving the charger on permanently while you are away overseas. Maybe you could fit a multi-stage charger permanently in the Defender and do it that way. Or put a timer on the powerpoint.
If the batteries are different sizes and types then they are going to give different readings, but I don't think that means anything is actually wrong, it's just different battery types and sizes giving differing results. For example, the 800CCA starting battery in our Defender (which is a new one) usually gives different readings to the 120 Amp AGM second battery, but nothing is wrong.

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