Thread: "Low Battery Warning- Start car now" with Traxide DBS fitted

To help with how this works.

The alternator is earthed through the engine and then to the chassis via an earth lead.

So what happens when, say your cranking battery is drawing 20 amps.

Your auxiliary battery is drawing another 20 amps.

Your driving lights are drawing 15 amps

Your fridge in the cargo area is drawing 5 amps.

Your entertainment system is drawing 25 amps.

Thats a total POSITIVE draw of 85 amps being drawn from the alternator via the connection on the cranking battery's positive ( + ) terminal.

BUT the 85 amp earth return for all this current is coming from the chassis.

The earth returns for the Auxiliary battery, driving lights, fridge and entertainment system are connected directly to the chassis so they do not come back to the alternator via the cranking battery. A total current draw of 65 amps.

The only earth return current coming via the EARTH lead on the cranking battery is the 20 amps the cranking battery is itself drawing.

So as the BMS is monitoring the EARTH lead at a point between the cranking battery negative terminal and where the EARTH lead connects to the chassis, and therefore the BMS will only see the 20 amps the cranking battery is creating.

Hope that helps to explain how the BMS monitors the cranking battery and why you should not connect ANYTHING to the cranking battery's negative ( - ) terminal.

Tim.
When connecting a Ctek,or any other charger is there an issue connecting the charger dircet to the aux battery,both pos/neg????.
Ctek has spark protection if thats an issue.
Andrew

Hi Andrew and it is standard safety practice to never connect jumper leads or battery charger leads to the negative terminal of the battery needing to be charged.

So if you are going to be connecting to the battery with alligator clips, then the positive clip goes the the battery's positive terminal.

The negative clip must not be connected to the negative terminal. This must be connect to an earth somewhere away from the battery.

BUT, if you are going to fit the Ctek lead with the eye terminals directly to the battery, then this can be to the ( + ) and ( - ) terminals.

Then it is safe to connect the battery charger via the plug.

And yes, if you have one of my isolators, this can all be done on the auxiliary battery, and both batteries will be charged.

Originally Posted by drivesafe

Hi Andrew and it is standard safety practice to never connect jumper leads or battery charger leads to the negative terminal of the battery needing to be charged.

So if you are going to be connecting to the battery with alligator clips, then the positive clip goes the the battery's positive terminal.

The negative clip must not be connected to the negative terminal. This must be connect to an earth somewhere away from the battery.

BUT, if you are going to fit the Ctek lead with the eye terminals directly to the battery, then this can be to the ( + ) and ( - ) terminals.

Then it is safe to connect the battery charger via the plug.

And yes, if you have one of my isolators, this can all be done on the auxiliary battery, and both batteries will be charged.

Hi
I use the CTEK lead with the eye terminals and I have the +ve connected to main battery and the -ve connected to the -ve post on the aux battery and it works ok.
Mainly done this way as getting at the earth point on car was a bit tight. I have a Traxide dual battery set up as well.

Richard

Originally Posted by drivesafe

So if you are going to be connecting to the battery with alligator clips, then the positive clip goes the the battery's positive terminal.

The negative clip must not be connected to the negative terminal. This must be connect to an earth somewhere away from the battery.

BUT, if you are going to fit the Ctek lead with the eye terminals directly to the battery, then this can be to the ( + ) and ( - ) terminals.

Then it is safe to connect the battery charger via the plug.

Whats the difference whether alligator clips or eyelets - aren't they both performing the same function?
Presumably when you say 'CTek', that is substitutable for other brands (eg my repco 7 stage with eyelet connections), or is there something particular about ctek?
thanks
Andrew

Hi Andrew, the reason I mentioned the Ctek eye terminals is because they come with both two leads, one with clips and one with eye terminals.

There are a number of other brands with similar leads.

The point about the eye terminals is that you need to spend the time to install them before you use the charger and as such, dramatically lower the chances of causing a spark and igniting and hydrogen that may have built up around the battery.

Whereas, with clips, people are more likely to connect straight to the battery's terminals without realising the danger it imposes.

Originally Posted by stray dingo

Whats the difference whether alligator clips or eyelets - aren't they both performing the same function? Presumably when you say 'CTek', that is substitutable for other brands (eg my repco 7 stage with eyelet connections), or is there something particular about ctek? thanks Andrew

As long as you don't have the unit powered on you will be fine. Just connect it all up nice and secure, then hit the switch on the power point.

My preference is to use the soft fittings supplied with the CTek and leave those permanently fitted....I have 6 of these soft fittings on 6 different batteries.

Brett....

Got the message tonight on my d4 my14

I probably have not driven for about a week ago

I was doing things in the car and had the doors open for an hour or so at most.

Before starting I went onto to the tekonsha p3 troubleshooting section to see what the battery was reading
This is not the best way to do it. It said 11.95v

I started the car ok and as you expect it went up as I went for a drive

I have left the car idle and will check again later and will put on the charger over night

I have a Traxide dual battery set up

Richard