How do you test a deul Bat set up?

[Remydog05]

Ive got an 80 Series and it has a Soleniod for the deul batt set up.
Have not had the car long only about 4 months
Ive just discovered over the past week the batterys are dying qucikly!

Is there any way I can test the set up before I go and get new batterys?
Just in case its the system killing them?

THanks

[Weiner]

Get the multi-meter out and check the voltages at each point along the line?

[Spimon_NH]

Not quite sure what you mean by killing them. Do you mean flattening the batteries or destroying them from overcharging?

Which particular dual battery system is it? This may help in the diagnosis if someone has some 'inside info' on it. Mine's a DIY job so may work slightly differently to the commercial ones, but the basic output should be the same.

If its totally killing them by overcharging for long periods of time, I think the only way you could test would be to use a ammeter to monitor the current flowing into each battery and ensure when they reach ~13.5v the current drops (unfortunately this requires a better (more expensive) multimeter than most people have).
If this is happening I'd be more inclinded to think a faulty voltage regulator is to blame, but would think that would cause a lack of current, rather than too much.
My dual battery system is equivilent to getting out of the car every 20 minutes and swapping batteries, to make sure they both get topped up. No battery can receive more current than it would without the dual battery system (as long as alternator and voltage regulator are working).


To test if the system is charging your batteries and not just letting them run flat....(this may not apply to your particular dual battery set up, but is applicable to mine).
Mine works by charging the main battery until it reaches 13.5v, then switches to charge the second battery until the main drops to below 12v. Ie Its priority is to keep the main battery between 12v and 13.5v. Once this is done, the 'leftover' current is used to top up the second battery.

To test mine, I'd disconnect the second battery. The system now thinks the second battery is dead flat (0v). I turn the car on and run it until the main battery is at 13.5v.
Now I can test if current is reaching the second battery by testing the voltage across the second battery terminals. I can also hear the solenoid physically clicking when mine changes batteries.

You could then disconnect the main battery (so the system thinks it's at 0v) and test if the solenoid switches back to charge the main battery.

Of course if you're not getting any voltage to one or both batteries, time to start troubleshooting (and possibly report back here with the symptoms).

Hope you can scavange something of help from here...

- Simon

[Box Feroza]

Great advice Simon.

[hando]

Not quite sure what you mean by killing them. Do you mean flattening the batteries or destroying them from overcharging?

Which particular dual battery system is it? This may help in the diagnosis if someone has some 'inside info' on it. Mine's a DIY job so may work slightly differently to the commercial ones, but the basic output should be the same.

If its totally killing them by overcharging for long periods of time, I think the only way you could test would be to use a ammeter to monitor the current flowing into each battery and ensure when they reach ~13.5v the current drops (unfortunately this requires a better (more expensive) multimeter than most people have).
If this is happening I'd be more inclinded to think a faulty voltage regulator is to blame, but would think that would cause a lack of current, rather than too much.
My dual battery system is equivilent to getting out of the car every 20 minutes and swapping batteries, to make sure they both get topped up. No battery can receive more current than it would without the dual battery system (as long as alternator and voltage regulator are working).


To test if the system is charging your batteries and not just letting them run flat....(this may not apply to your particular dual battery set up, but is applicable to mine).
Mine works by charging the main battery until it reaches 13.5v, then switches to charge the second battery until the main drops to below 12v. Ie Its priority is to keep the main battery between 12v and 13.5v. Once this is done, the 'leftover' current is used to top up the second battery.

To test mine, I'd disconnect the second battery. The system now thinks the second battery is dead flat (0v). I turn the car on and run it until the main battery is at 13.5v.
Now I can test if current is reaching the second battery by testing the voltage across the second battery terminals. I can also hear the solenoid physically clicking when mine changes batteries.

You could then disconnect the main battery (so the system thinks it's at 0v) and test if the solenoid switches back to charge the main battery.

Of course if you're not getting any voltage to one or both batteries, time to start troubleshooting (and possibly report back here with the symptoms).

Hope you can scavange something of help from here...

- Simon

Simon, it'd be interesting to know why you chose to do a DIY job.

[Middo]

agreed on the multi-meter idea. its the quickest and easiest way of testing it.