aux batteries issues!!

Hi Derek

Thanks for your reply. The battery management system is one of yours a DBi-120.

The aux battery is immediately adjacent to the original battery and connected via sufficient size large cable ( from memory 8mm maybe 10mm but it is was the cable supplied by you with knowledge of the project and vehicle at the time and so I am sure it is adequate)

I also have two other batteries (AGM deep cycle 100ah) under the tray which are also managed / connected via another DBi-120 between the aux and themselves (connected by starter size cable)....which in turn are also managed by a Plasmatronics PL20 solar controller (including shunt for the alternator charge) with 2 x 64 w uni solar on the roof of the canopy!

These two under tray batteries are managed by the PL20 as far as load and LV cut out and are about 5 years old now (from previous vehicle and still working fine)

so a bit of a power house really but over the years I have learnt about being under powered, under cabled and under storage capacity!

The low voltage cut off has for almost from the beginning (Feb 08)disconnected if the vehicle is parked for longer than maybe a week.......something that confused me but I never got around to testing the damn thing until very recently..........discovered that on standby it (the LVCO)is drawing 0.25a (two LED and whatever is chewing it up inside as well)..........I rang the manufaturers (12 volt shop - Arrid) and asked innocently what the stand by current draw was and they said they did not know!

I have isolated all circuits and very satisified that the only load on standby is the LV cut out....

in theory this stand by load should have done the battery more good than harm by cycling it?...OR WHAT HAS JUST OCCURED to me as I type

It has continued to draw current on stand by and whilst cutting off the aux circuit has continued to draw down the aux battery and stuffed it. ? 7 days x 24 hours at 0.25ah is = 42a ! and there has been periods exceeding 7 days parked up...JUST MAYBE i HAVE ANSWERED MY OWN QUESTION??

I made an assumption that the battery was fully charged because of

a) the long drive as mentioned at the start
b) the measured voltage about 1 hour after the final drive at the end of the day (12.6v)
c) I measured battery voltage after about 1 hour of the sound system and was well below 12v.and the sound system dropped out at 10.7V (may have been a bit below that because I lost 2 or 3 mins before i managed to test the battery

your comments appreciated

Thanks

Graeme

should have proof read my work.....the "long drive" mentioned was 4hours with no load on the aux battery....ambient was high 20's at the most

cheers

Hi Graeme

The drive time and alternator voltage may not be enough to charge the battery to 100%, you would need to maintain this battery with a charger or link to the solar system. (N.C. relay) or a DBi-120 in reverse between the AGM's and MRV70.

Yes the LVCO has a small relay and will use power too but once activated at low voltage should draw nothing or only the red LED current if it has one.

I would suggest you try revive the battery first and then test it again, it may recover.

My new Prado 150 also drops voltage down to 13.42V when hot, when I got home from a 4 hour drive and plugged into my ABR 20A charger the charger went Bulk 2 mins, Absorption 30 mins and then to float. I did not measure the amps but would say the battery took another 8 to 10Ah. This is on a 60Ah battery. (Fridge was off)

Regards

Derek.

Hi Derek

I guess I should have added that the battery had not been used for any accessory for some time and the vehicle has had lots of use and so I am sure the battery would have been fully charged before i actually got around to testing it..obviously I have no way of knowing for sure...this battery really has no use other than sit there!

dont you think the LV cut out is using excessive current on stand by?

Graeme

Hi Derek

the LV Cut out is activated now and I have just put the clamp meter on it and it is still drawing 0.25 ah with the accesory outlet disconnected!

Hi Graeme

Yes 6Ah a day is a lot for the LVCO, can you fit a switch in line or pull the fuse when not in use.

You may have damaged the battery and that is why it is not holding charge, I would still recommend you try revive it but if you do replace it you now know what to look for to make the new battery last longer.

Regards Derek

If it draws 0.25A when it is supposed to be protecting the battery this is a problem. It then has the potential to take a battery down to 0V if you are not around.

Thanks Derek

I am satisified that the LV cut out is a second rate design!.......will remove it out of the system........

try and revive the battery and if not successful I will give MRV70 the benefit of the doubt and buy another one

appreciate your help..another mind always helps kick start the one stuck in tram tracks!

Graeme

Hi again Derek

This question relates to the function of the DBi-120 in this system

have had the aux battery (still in the vehicle) on charge over night (CTek). Battery indicator shows full and function light normal on the charger.

Aux battery voltage 13.86v (charger still connected) BUT THE MAIN BATTERY also shows 13.86v and the DBi-120 has an orange light showing

Unfortunately the way I have had to install the DBi-120 is vertically facing away from me on the aux battery cradle and all I can see is the orange light glowing but not able to read the writing etc on the front....so not sure what it is saying. The other DBi-120 connecting the aux to the pair of batteries under the tray is NOT LIT

Disconnecting the positive cable from main battery to the DBi-120 on the aux immediately causes the main battery voltage to start dropping (INDICATING A REVERSE FLOW OF CURRENT IS HAPPENING through the DBi-120) The orange light on the DBi-120 remains on.

re connecting the cable the reverse flow of current commences (aux to main).......I was under the impression that the DBi-120 was monitoring the main battery voltage and connected the aux when main battery reached the pre determined voltage / assumed state of charge. Obviously in this case the voltage on this controller is doing the reverse. The other DBi-120 (aux to other battery bank) is behaving as I expected..well at least there is no light displayed

Your comments please
Thanks

Hi Graeme

First of all if the car was recently switched off or the main battery is fully charged the DBi will still be engaged so this would then allow the Ctek to charge both batteries.

I would recommend you switch the Ctek off and switch the headlights on and wait to see if the DBi switches off and you will then know you have installed it correctly which I would think you have. Start the car and the DBi's should both switch on.

The 2nd DBi should engage and also be glowing if the supply voltage is 13.86V as you say.

Perhaps do a few tests and back probe the voltages.

Regards

Derek.

Hi Derek

Switched off the Ctek. Dbi still engaged.........headlights and spotlights on.........DBi disengages (main BV got to 12.05 before I had a chance to measure it as soon as I noticied the DBi disengage...probably disengaged a bit higher than that V but happened so quiick I was still walking around the vehicle)

Headlights off...both Dbi still disengaged
Start engine and in a few seconds both DBi engage main BV 13.9..aux 13.89V

Stop engine.....Dbi (main to aux ) stays on...DBi 2nd bank goes off

headlights back on to disengage aux DBi

connect battery charger to AUX...Dbi remains off

Main Batttery voltage 12.8 and isolated.... Aux battery under charge 14. something

So my assumption is that

1) the first DBi was engaged when I put the Charger on as I had driven it around to my workshop to access the charger 5 mins minutes beforehand...and I would not have been looking or noticied that the light on
2) therefore once charging the AUX the circuit remained on routing backwards throught the DBi...makes sense

Only thing that remains unanswered in my mind is why the DBi remained with the light on when I removed the cable battery positive from the main to the AUX connections on it.....as it should have sensed a voltage drop from the main battery (0 actually) and disconnected...... a timing thing or what?

Thanks again
Graeme

Sorry for my late reply, we went out for lunch. (Great spot in Toowoomba called Fitzy's Fibber Magee, 153 Margarent St)

All sounds fine.

If you disconnect the main battery while the DBi is energized it will stay on until the aux then drops to 12.5V it is designed to sense a slow drop in main battery voltage not an instantaneous cut off of all power.

Regards

Derek

Thanks a lot for your help and prompt replies Derek.......glad you stopped for lunch!

end result is I will give the MRV70 allrounder the benefit of the doubt and purchase another if I cannot salvage this one

Will through away the arrid LV cut out.....expensive purchase....

"1) AGM's need higher V than what the alternator can deliver "
- garbage - they'll charge fully at 13.6 volt.

"2) AGM's does not like the heat under the bonnet "
- true - if your alternator regulator is not working correctly.

"3) AGM's need constant voltage when being charged and does not like the variable charge of the alternator "
- garbage.

For salesmans' talk, one out of three ain't bad.

I have 3 x 50 amp AGM Orbitals. 1 under bonnet, died after 3 years. 2 in the rear of the truck, still going at 5 years.
Cheers Lyndon

> 1) AGM's need higher V than what the alternator can deliver

Provided the alternator voltage is correct for the battery being used, they are fine. Problem is a lot of moden vehicle alternators decrease the voltage after the engine is warm to decrease their load at idle to reduce emissions. In these cases you will probably need to use a battery charger as well to get the battery up to 100% charge on a regular basis.


> 2) AGM's does not like the heat under the bonnet

True. However, no battery does. All Valve Regulated Lead Acid (VRLA) batteries regardless of if they are GEL or AGM cannot be "topped up" so need to be protected from heat as much as possible to reduce excessive gassing and drying out to maximise their service life. Heatshield sheetmetal is now readily available for 80Ah and 100Ah sizes.


> 3) AGM's need constant voltage when being charged and does not like the variable charge of the alternator

Alternator voltages normally only change when a large load is applied, and are otherwise fixed, unless the they are the type mentioned in (1) above.

Best regards, Dave