Charging Voltage too high ?

[Mblinko]

I noticed that my Tmax split charge was clicking in/out frequently following a month of being laid up so I drove it around for a while to top up the batteries and this morning carried out some basic tests using my trusty digital meter. This is what I found:

1. Both batteries in the engine bay are giving 14.5 volts as has the Aux battery
2. On start up from cold the alternator is kicking out 16 volts but this settles to 15.5 after a few mins.
3. The FSM says test at 25 degrees C so I went for a run, retested and the result is the same, 15.5 volts
4. The split charge relay is no longer clicking in and out repeatedly.

The FSM says if it's charging at over 15 volts check the IC Regulator. I've no idea what this is or whether in reality 0.5 volt overcharge represents a problem.

Anyone out there who can advise?

I'm just concerned to address any problems before we leave on our tour in September.

 

[Dave2000]

First pull all the cables and clean them thoroughly, check earths to engine/body as well. FWIW if my vehicle has been out of use for a week or two the initial battery charge is high circa14.4 - 14.8, after about five or six minutes it drops to 14.2 - 14.3.

Most split chargers drop out if the voltage is too high/low, they also act up if a battery going bad, of course depending on the age of the batteries you may end up replacing both.

If you have access to wet cells use a hydrometer to look for a bad cell, if not then find someone with a battery tester. Checking battery voltage with a multi meter is a bit hit and miss. If that is all you have then both batteries should be subjected for about 15 minutes to a load which will burn off the surface charge which will mislead you.

Continual high charge rates may indicate the alternator is packing for a holiday.

regards

Dave

 

[StarCruiser]

Sounds to me that the regulator located inside the alternator is giving out too high a charge voltage. The voltage you are seeing is above the max charge voltage for a 12v car battery and can damage the batteries if left in this condition. Yes, 0.5v is a problem.

As Dave has said, check all connections, unplug the plug in the back of the alternator and plug it back in to scrape the connections.

Sometimes there is a bolt sense connection at this plug. If all is good and the voltage is still above 14.8 at the terminal on the rear of the alternator, then I would expect the regulator to be in need of replacement.

If you can, test a known voltage with your meter to make sure it is reading correctly, however as you have been drawn to this problem I would suggest your meter is probably reading correctly.

I believe the regulator can be changed, I believe it is a bolt in item and will be far less cost than a replacement alternator and worth doing if nothing else is wrong with the rest of it.

 

[Mblinko]

Thanks Dave.

The aux battery is a new Odessy one. The others came with the car. I have this tester ..



And both starter batteries read green, ie good after a 10s load. Checked the charging voltage again and it is still 15.5-15.6 volts, though instantly I connected the meter it read 19v but dropped to 15.6. Is this pointing to a dodgy alternator ?

 

[StarCruiser]

Looks like the regulator in the alternator needs replacing.

 

[Mblinko]

Thanks Guys. Alternator looks very old and is unknown to me so will replace it.

One final question, should I go for 80A or 110A?

 

[StarCruiser]

If you've got gadgets, gizmos and a fridge, maybe worth the 110A. If you've had all these things on and connected for a while with no issues (this one aside) then there may be no need. Ten years ago pre LED my answer would have been a straight 'get the 110A' but nowadays, loading is decreasing. All depends on your setup and which battery it's connected to. The one trump card would be a winch IMO.

 

[Mblinko]

Yes, you got it. I have a winch on the starter battery. All other new electrical facilities are connected to the aux battery.

 

[StarCruiser]

We have a winner…110A [emoji4]

 

[Dave2000]

What is the chance of getting a 150 amp unit in the UK? I got mine from the states but it was a deal I could not refuse and I was not in a hurry for it, more or less bolted straight in. *Other than that 80 amp to 110 is approaching an increase of 40%, given the age of the wiring it might it be worth considering running a new cable up to the battery?

regards

Dave

 

[StarCruiser]

For sure Dave, even if the wiring were new I would be advocating that plus a suitable fuse/fusible link at the battery.

I have a pal who rewinds alternators and starter motors, I'll ask the question re the 150A unit. [emoji6]

 

[Chris]

Mine is a 120 amp unit. For me it's not to do with load whilst running (ie charging ipads etc). Under normal conditions I pretty sure an 80 amp unit is more than enough. But when you have been parked for three days with everything running and all three batteries need recharging I figure that I'd rather have the alternator being well capable of providing that peak charge, even if it's only for a while. I want the batteries back up to full condition again quickly. My split charge across the front two batteries is timer related but only starts counting ONCE 13.5 volts or something is registered in the battery itself. So on a slow charge I could go quite some way and not actually put anything into the aux battery. I'd like to change that system at some point actually.

 

[StarCruiser]

The bigger the alternator, the faster it will charge a battery, or more accurately, the more it will be able to keep up with a load connected to the battery. In a standard truck with no additional loads, the alternator has to supply enough power to continuously run anything that is likely to be switched on together at the same time. Worst case could be for example, rear demist, front fan on max, headlights, tail lights, trailer lights, fog lights, fuel cut solenoid, radio, dash lights, air con clutch, wipers front, wiper rear. On top if this it needs to put some charge back into the battery to top it up after starting. So the 80A will be enough to do all that.

The thing to look at is whether you are adding to this overall total, or somehow only using power when some or most of these items are not being use.

The classic example of an addition is a second or leisure battery as Chris has mentioned. With only the standard setup, it may be some time before the vehicle batteries get to their fully charged state and hence the leisure battery may not receive full charge for some considerable time later in the journey. In this scenario, replacing the alternator with a higher current one will mean that the vehicle batteries get charged quicker and there is then charging current available for the leisure battery much earlier on, and at a higher rate, as there will be no more than the load exhibited by wipers, headlamps etc as above. In other words there will be a fair bit left over.

A winch on the other hand draws varying currents from perhaps 100A at no load to 400A or more when under load but for fairly short periods of time. This will draw heavily from the battery (be it starter or leisure) and will be supplemented by the alternator if the engine is running, and charging the battery back up when the winch isn't running. The difference here is that the winch is only likely to be used with headlamps and fuel cut off valve (if unnecessary loads are switched off) and as such has more of the factory alternator capacity available to it.

The benefit of a larger alternator with a winch is that it is able to supplement the battery current far better than the smaller one, keeping the batteries from cycling (discharging) as deeply, which is a benefit to the batteries as (most) vehicle batteries are not designed for deep discharge but for high currents over short periods.

 

[Chris]

And....... when winching, try to winch in short runs. Don't flog it til the battery is exhausted. A bigger alternator will replace that power to the battery ready for the next pull. OK sometimes the winch is low draw, but when you get that major winch action going you can be pulling your battery inside out! Not many people consider their battery when doing heavy winch work. Use a snatch block to reduce effort too. Every bit helps.

 

[StarCruiser]

This is where the 24volt start cruisers score as with the two batteries in parallel there is twice the capacity (of each battery) in the system so the draw is from both roughly equally (slightly more from the battery that the winch is connected to due to losses in the connecting cables, change over relay contacts etc.). And if the engine is revved slightly on the hand throttle then the alternator will be taking a share of the load, again helping with the batteries. The higher current the alternator, the bigger the share of that load it will be able to take.

The advice from Chris is the best way to help the winch and batteries maintain their health, but a strong electrical system (good batteries, good alternator, good cables) will allow the system to remain healthy longer and cope with more and tougher use.

I'll have to look into the Optima batteries but IIRC they are designed to take a deeper discharge with higher current than most.

 

[Chris]

or you have a system like mine that at the touch of a button the 2 batteries are linked anyway. In fact I get the benefit of all three batteries being linked. Ho ho.

 

[Gary Stockton]

Me too

 

[Dave2000]

The 24 volt cruisers have no advantage if you have the split charge twin batteries, both systems can have 12v with double the amperage. I use a Blue Seas dual sense system, unless it is dark and the engine off the batteries are always on charge, via alternator or solar panel.

I am afraid Optima's have started to lose their reputation IME, the rumour is that the quality has fallen since Johnson Controls took them over. Wherever possible regardless of manufacturer try to get something specified for marine use, I have found anything designed for use at sea (split charger for example), are manufactured to a higher quality level.

Also you get the additional stud terminals which makes it easier to hook up accessories.

The cut in/out of 13,5 is typical of most battery isolators but, your primary battery will have a voltage exceeding 13.8 within seconds of starting up, so all batteries connected to the system will start to charge pretty much straight away but having the spare amps will help get them healthy sooner.

regards

Dave

 

[StarCruiser]

Even better Chris!![emoji108][emoji108]

 

[StarCruiser]

It all depends on the size of the batteries (and I'm talking about the twin battery setup as compared to a 12v single battery conversion) where there will be more capacity and cranking amps across two batteries in parallel than across one of the size that fits the standard battery tray. Add the leisure battery if wired with heavy cabling and there's some serious current available.