Hope this makes sense? My tug has duel batteries as standard, they are seperated by an ignition activated solenoid so that I can use the 2nd battery to run things and not put the starting battery at risk, when you run the 2nd battery down to say half charge will the alternator charge that battery or sense the start battery is full and drop charge rate to suit or will the two batteries naturally balance and charge to capacity during the trip
Electrical Battery charging
- Thread starter poor but proud
- Start date
It really depends on the set up, normally it should charge both to capacity ................. if fitted with a DC-DC charger then it will put full charge into the aux ............ if just a dumb alternator with a old school set up and just a charging relay which keeps the 2 batteries seperate, it will charge up the aux happily, so it all depends on how they ares et up, the aux battery should only run down when a load on it and the engine is shut down, when engine running the battery should stay charged.... of course if a dumb set up both batteries must be the same chemistry and ideally the ground for the aux should be at the connection where the main battery is grounded, engine/chassis ..
Something not quite right with my second tug battery, battery good same as starter battery, I will look at all fuses connections etc ,appears to only get about ;70 percent of the charge the start battery is getting, probably something simple like a dirty/corroded wire something to cause a voltage drop, first step ,the battery came to 100 percent on charger and solar, next is to look at all connection between battery and isolation solimoid
A simple way to test would be to measure the voltage of 2nd battery without, then with, engine running. if the voltage jumps to over 14 (usually 14.6) then it should charge fine. Not fully charging could be due to the time required? It's easy to run a charger for 10 hours over night compared to driving.
What sort of charging relay/isolator are you using, I know some will sort of trickle the aux until the cranker is full then work on the aux, then again if the aux has a load hanging off it you may never see it full .............. when you get back from a run disconnect the aux, wire or close fuse, check it then come back 30 min later and see what it reads that will give you decent SOC on the thing ......................... As Jazza said it can take a fair run down the road to get everything juiced up ...
A DC-DC charger will give it full noise from the get go as it only see's a power supply from alternator and the state of whatever is on its load side... hence they will charge an aux far quicker than an alternator trying to charge 2 batteries and run the rest of the show as well, 60-80 amps doesn't really go far in modern vehicles nowadays ..
A DC-DC charger will give it full noise from the get go as it only see's a power supply from alternator and the state of whatever is on its load side... hence they will charge an aux far quicker than an alternator trying to charge 2 batteries and run the rest of the show as well, 60-80 amps doesn't really go far in modern vehicles nowadays ..
I made up a charging system from a Jaycar kit some years' back for my brother in law's 4WD . He wanted to connect a second battery under the bonnet to run auxiliary items separate from the main cranking battery. The extra battery would not get ANY charge from alternator until the cranking battery had reached 14 odd volts so the cranker was always topped right up before the extra battery got anything. The trigger to start charging the extra battery was sensed by voltage through a small resistor before any amps could start charging the extra battery. The cut-in voltage could be adjusted by changing the resistance value. This connected two high capacity mosfets (in parallel) to vary charging the extra battery, all independent of cranking battery. All worked well for his trip to the Cape, that is, until he dipped the bonnet into the water and splashed water over the unit. Had to do without unit until he returned to home where I replaced the the voltage sensing resistor. This was all before the later electrical setups and DC to DC chargers were around. So, the problem could just be the setting for the change-over charging point. A good multimeter could assist in confirming this.
Travelling for the next couple of days ,I did I quick voltage check with engine at ldle start battery appears to be getting more charge than the second battery I will do it again when I get home and record the actual figures, the l set up is KISS, .no DC to DC charger, just a ignition operated isolation solinoid ,I did find a fuse holder that has been hot at some stage,fuse not blow, but some corrosion in the fuse holder same type of corrosion you see on you trailer plug fridge wire
Forgot to say in my previous message that although the made up kit was great, the one thing it could not do was provide a different charging VOLTAGE to the extra battery, as it was still linked to the voltage regulator for the cranking battery. This setup probably would not be too good with todays "smart" alternators which vary the charging voltage according to the vehicle load. That is the advantage of todays DC to DC chargers in that you can have the varying charge voltages for the tug cranker battery, and a step up/step down voltage for the extra/auxiliary battery with the DC to DC unit connected between the alternator and the extra/auxiliary battery. And additionally, as @Drover said, both batteries could be charged at the same time if required. That sort of technology was not around at that time and 12 volt electrics and batteries have changed considerably since then!!
The old set up of mine back in the analog days, once the cranker was juiced up it was full noise to the aux, unless the big spotties were running then it was take whats left over which wasn't very much.......... now with smart chargers and there are a few varieties, any extra stuff the ground must be to the engine/body where the cranker connects and not on the cranker battery it self or all sorts of drama happens, a quick look at the NEG post on the cranker usually shows a box of some sort on the post or on the cable run, this is where the ECU monitors the battery so any connection must not be fitted between it and the battery............... Found this out when my mates Ranger years ago, wired up by the Dealer for an aux from new, wrecked 2 batteries in short order, something on this site reminded me so we rewired it and now years later its still working and the dealer said BS, we proved him wrong..... Well thats what I have found works with Rangers, BT50's the Jeeperific doesn't seem to be problematic ..............
I think you will find @poor but proud that all will be well in the long run........................... but alternators while everyone see's 70 or 80 amp capacity, old style would only throw that amount once the revs are high enough, at idle it can easily be half or less which is why batteries can take time and today electric everything and with electric steering it can eat nearly all of that with an ECU governing output using battery state, load and ambient temp to configure a charge rate ...........
@Drover , oh so true on your last paragraph, and also the connection of the neg to the same ground as other battery - not the neg battery terminal!!
If the temp sensor plays up and the ECU thinks its cold like 5c but its really 30c you can end up with a stuffed battery or it may be vis a vis, anyway it makes the charging go haywire and cook things it seems .... some found that out when doing an EGR shut down on a Merc engine, think it was the wrong resistor fitted and the ECU got the wrong message .......................
Just as info, my WK2 Jeep has a 220a alternator in it just to power all the bits, the mind boggles from the days when an 80 amp was a biggy, the old 100 series was 120a I think and its just climbed away since, no wonder batteries cark it early and things go fizz............... My electri/hydraulic steering can want up to 80a when its busy, so imagine the load with a van plugged in and a fridge in the back as well as spotties burning..............
Just as info, my WK2 Jeep has a 220a alternator in it just to power all the bits, the mind boggles from the days when an 80 amp was a biggy, the old 100 series was 120a I think and its just climbed away since, no wonder batteries cark it early and things go fizz............... My electri/hydraulic steering can want up to 80a when its busy, so imagine the load with a van plugged in and a fridge in the back as well as spotties burning..............
Another simple check (with a digital multi-meter) is to measure the voltage between battery 1 pos and battery 2 pos. That will tell you if there is any loss in the wiring, fuse, solenoid etc. If you see a drop (say 1 volt) then leave one probe on batt 1 pos and work your way back along the circuit. This also works doing the negatives but not so clearly
to some one who grew up using carbide lights, 32volt gen. sets and tilley lights, sometimes i think you learned gentleman speak in another language
@poor but proud, you are not alone. If I did not know some of these members personally, I would be reminding myself of the old saying, “Bullsh1t baffles brains”. However, I bow to their superior knowledge, even if I don’t understand it.
I know exactly what you mean, what knowledge I have is from trial and error in many cases, poke it with a stick and see what happens sort of thing....... Mainly never having the money or time to get someone else to do it, nor trust, it was trial and error with lots and lots of reading, be it mechanical, electronic or 12v electrickery ... Things like vehicles evolved slow enough so I could keep up, mostly ........... Often most of the great improvements are more to do with fattening wallets of maintenance people I think, they ceratainly aren't always an improvement in reliability or usefullness.
Though I'll pick an LED light over a carbide anyday, though peeing into a carbide light to recharge was a laugh........... did some caving back in the day.
the mystery is solved,the difference in the charge rate was a faulty soleniod,, it was not allowing the full charge to the second battery, on starting the drop was only a small amount , but at highway speed the solenoid cut off the charge causing the battery to go flat when using fridge/freezer, took two different guys to find it. have replaced the solenoid with a redarc unit which now services the battery properly and i can set a desired cut off voltage which will give me some extra usable amps without putting the start battery at risk, saga over wallet lighter
Thought it might be something like that - the change over voltage not allowing any current (or the correct current) to be applied to second battery. Yeah, a faulty solenoid would be hard to pick up at times. Glad it is fixed now anyway. Good luck and safe travels.
If the Red Arc chucks a wobbly and the leds just flash all together, disconnect it for 5 mins then hook back up seems to fix them up.............................. I hope you sorted that corrosion on the fuse wire bit, while it may show OK on a meter, the corrosion could cause a big loss when full power is being drawn .........
All connections fuse carriers and wires checked.cleaned or replaced. The auto sparky gave me printouts idle.fast idle and highway reves all look good at this stage .big trip coming up need the extra storage capacity to support the van in the cold and cloudy state that starts with T. I am not allowed to say that name until we get there .this is the fourth try.3 weeks 5 day and 12 hours before departure .but I am not counting ( much)