Battery charging volts low.

[xtrailman]

I've had a tow bar fitted today the car is a diesel CX-5.

In the UK we have a voltage sensitive relay fitted to enable battery charging and fridge cooling to the trailer (caravan).

This relay seems reluctant to pull in, it needs around 13 volts to pull in, and there lies the problem, I don't know how the alternator charge is managed but with the engine on fast tick over up to 2K revs, the voltage across the battery never goes above 13 volts, it may do when running on the road but not while stationary.

Any ideas? Or similar experiences.

 

[MikeM.]

Maybe one or more cells of your battery is defective. That might cause the regulator to under charge. I have the gas 2.0L and system voltage is generally above 13V when the engine is running.

 

[xtrailman]

Thanks Mike I'll speak to my dealer Thursday.

 

[erhayes]

Normal charging voltage is ~ 14.2V at 1,500 rpms

 

[piotrek91]

Are you measuring the <13V on the battery in your trailer?

If so, my first guess would be that your battery and fridge pull a lot of current,
and there might be a large voltage drop on the long wire connecting your trailer to your alternator.
There is probably 15-25 feet of wire between your alternator and the battery/fridge in your trailer.
If the battery+fridge pull 10A of current (just a guess) over a 16 gauge wire (another guess.. I don't know what gauge wire you're using) you're looking at a drop of at least 1V from your alternator to the trailer.
Try measuring the voltage across the battery in your car, there you should hopefully see over 14V.

If you are seeing the <13V on your car battery you may have a more serious problem (or it may just be some smart, efficient charging system)
I'm guessing that if you have the i-Eloop system on your car, the alternator may not even be running unless the battery voltage falls too low.

 

[xtrailman]

Well this has all been a strange scenario.

Yesterday I couldn't get more than 13 volts across the car battery, and no charge to the caravan battery.

Today I've seen over 14 volts on the car battery, and about 14 volts across the caravan battery, so all is now as expected.

In both cases the fridge was turn off, and I've had two 3mm cables run, one for fridge other for the caravan battery charge.

I'm not sure what's happening, but as it is the system is working!

 

[piotrek91]

Maybe the alternator is decoupled unless the battery voltage drops below a certain level?

I'm speculating here, but if you ever have this issue try turning on your headlights, brights and brake lights to see if it helps bring up the voltage.

 

[dad of jon]

I've had a tow bar fitted today the car is a diesel CX-5.

In the UK we have a voltage sensitive relay fitted to enable battery charging and fridge cooling to the trailer (caravan).

This relay seems reluctant to pull in, it needs around 13 volts to pull in, and there lies the problem, I don't know how the alternator charge is managed but with the engine on fast tick over up to 2K revs, the voltage across the battery never goes above 13 volts, it may do when running on the road but not while stationary.

Any ideas? Or similar experiences.

my car wouln't i-stop for the first few days i had it, until I assume the battery had been topped up sufficiently following its journey from japan.

 

[xtrailman]

I don't think it the I stop that's been ok from day one for me.

 

[HiCx5]

My CX-5 (July 2013) has an undocumented feature that changes the battery charging voltage depending on the engine load and the battery state of charge. I've seen the battery voltage vary between 12.1 and 14.9v while driving. The higher voltage occurs when decelerating which provides a sort of regenerative braking. It's a great feature for fuel savings but it's not mentioned in any of the user documentation that was given to me. I still haven't figured out all the details of how it is implemented - seems quite complex and a bit unpredictable. Best solution for a trailer / fridge / aux battery is to buy a DC/DC converter that can accept a wide range of input voltages while supplying the output voltage that you need. 4WD shops should have something - other off road vehicles have the same issue when used with camper trailers.

 

[xtrailman]

Thanks for the intel.
Your post ties in with my findings solo, I've recently bought a plug in voltmeter and been monitoring that.

http://www.amazon.co.uk/gp/product/B0092KVYGI/

Its a bit disconcerting to see the volts so low just after starting often 12.1 volts, just when you have taken a large load from the battery, also I always thought a good battery should be around 12.6 volts, so would expect the car to be charging.

And yes it defiantly uses regen, as soon as you lift of the accelerator usually.

As yet I haven't towed since I've bought the gadget.

From what I've read all new cars now have a similar smart system, the Vauxhall one will increase the volts when the headlights are used.

How do you monitor yours?

 

[HiCx5]

I have the exact same plug in meter. Very useful. The 12.6v that you refer to is correct (actually closer to 12.7v when fully charged) but indicates the state of charge only when the battery is unloaded and has had time to settle. I also see 12.1v just after starting. You can get a better indication of the state of charge by observing the voltage before starting. In my model I do this by pressing the start button with my foot off the brake. That turns on accessories only, which includes the plug in meter. That way I usually see something close to 12.7v. Radio and nav system pulls it down quite quickly but you get enough time for a quick reading.

The bit that I can't quite figure out is why sometimes the regen system reverts to a "conventional" charge mode that gives a constant 14.5v. It seems to go into that mode for a few days at a time then it goes back into regen mode by itself. It's probably reated to the battery state of charge - too many starts and not enough deceleration regeneration. On one occasion I think I coaxed it out of that "conventional" mode by toggling the istop off/on -may have been a fluke 'cause it hasn't worked on other attempts. I want to understand the battery charging system better because I plan to do some road trips with a car fridge and other heavy loads on the aux sockets - don't want any surprises after I set off. So far I haven't found any detailed info on this system anywhere.

 

[xtrailman]

I was hoping you had a different one, as I suspect the reading may not be 100% accurate, 12.1 volt seems low to me with the engine running.

So when I get round to it I'll compare with my Fluke meter.

 

[HiCx5]

Well..it's not a precision instrument but should be close enough to indicate what's going on. Incidentally I modified mine to prevent voltage spikes disturbing the reading - that was a problem on my former vehicle which had a noisy alternator.

I forgot to mention that my CX-5 is a 2.5l petrol so there may be some differences with the implementation of the regen scheme. E.g. when cold at idle the alternator isn't charging the battery at all - presumably to help with smooth idle. That's when I see see very low voltages as the battery hasn't had time to recover from starting. As I drive and the engine warms up the alternator voltage seems to be progressively increased. When the engine is hot the regen scheme seems to kick in fully so again I see very low voltages (down to 12.1v when accelerating and very high voltages (up to 14.9v) when decelerating.

Also, try googling "battery used for istop system". There's a Mazda technical bulletin that contains some useful info on battery charging. I suspect some periodic battery maintenence is built into the regen scheme to minimise sulphation of the battery. Current into and out of the battery is monitored by a sensor on the negative battery terminal so the PCM knows the battery state of charge and "should" adapt the charging regime to compensate. That may explain the "conventional" voltages that I see sometimes.

Please let me know if your observations stack up with any of the above.

 

[xtrailman]

Sorry about the late reply.
Since starting the post I have had time to monitor the charging voltage.

unfortunately my car failed to start, volts were down to just above 11 volts. First car since a 80's metro since I've had a car fail to start.
luckily I have a power pack so managed to jump start the car, following a 2 hour drive I put the car into a Mazda dealer.

Dealer said the battery required reinitialising, after that the charging volts were at 14 volts with the head lights on initially.
However on the return journey another 2 hour trip on motorways, very little was put back into the battery, as you say often showing only 12.1 volts then upto 14.7 volts on the overrun.

Problem is most of the time I'm accelerating or using throttle, so next to nothing is going into the battery.

What I cant grasp or understand, is immediately after starting I would expect maximum charging volts to replenish the battery??

This never happens!

I'm going to take SG readings from the battery tomorrow, as I don't have confidence in the car starting, I'm carrying a power pack in the car just in case.
Once armed with readings I'll be phoning the garage.

Well..it's not a precision instrument but should be close enough to indicate what's going on. Incidentally I modified mine to prevent voltage spikes disturbing the reading - that was a problem on my former vehicle which had a noisy alternator.

I forgot to mention that my CX-5 is a 2.5l petrol so there may be some differences with the implementation of the regen scheme. E.g. when cold at idle the alternator isn't charging the battery at all - presumably to help with smooth idle. That's when I see see very low voltages as the battery hasn't had time to recover from starting. As I drive and the engine warms up the alternator voltage seems to be progressively increased. When the engine is hot the regen scheme seems to kick in fully so again I see very low voltages (down to 12.1v when accelerating and very high voltages (up to 14.9v) when decelerating.

Also, try googling "battery used for istop system". There's a Mazda technical bulletin that contains some useful info on battery charging. I suspect some periodic battery maintenence is built into the regen scheme to minimise sulphation of the battery. Current into and out of the battery is monitored by a sensor on the negative battery terminal so the PCM knows the battery state of charge and "should" adapt the charging regime to compensate. That may explain the "conventional" voltages that I see sometimes.

Please let me know if your observations stack up with any of the above.

 

[HiCx5]

Sorry to hear about your troubles. All I can add is that mine definitely goes into a different mode when the battery gets low - when that happens it sets the charge voltage to 14.5v and holds it there until the battery has recovered. That can take a couple of hours or days if the trips aren't long enough. Then it reverts again to the variable voltage mode. Yours seems to be stuck there. Maybe mine is a newer model or maybe yours needs a firmware update. I'd escallate it with Mazda if the problem persists. Good luck.

I also find that my typical driving around town doesn't put enough juice back into the battery in the normal variable voltage mode. The state of charge of the battery degrades on each successive trip until the recharege mode kicks in and saves the day. If I had more hills on my usual routes it would work better.

 

[joemon1984]

I had my first service last week and when I checked the service report it says "tested battery and passed but could use a recharge". I am not sure if dealer did a recharge( it took only normal amount of time for service so I assume battery wasn't recharged).I have no starting issue. Digital displays on the panel is bit sluggish when I start but gets to normal in few minutes. Do I need to recharge my battery? I have an Eliminator brand battery charger.

Is it normal to have a sluggish display in winter season?

 

[HiCx5]

joemon, I don't think that a low battery would cause problems with any displays unless the battery became really low - then the car wouldn't start. I'm not sure which display is giving you trouble - audio/nav or dashboard but either way I'd get it checked by your dealer. It sounds like you have a faulty regulator that controls the voltage to the display.

If the dealer reported the battery needed charging they may have given it a quick boost with a fast charger. Normally, you shouldn't need to charge it. It may have been a bit low when the dealer checked it but it should sort itself out with normal driving. I've seen mine get quite low - maybe about 50% charged from time to time but it recovers again without intervention (see my earlier post). No problems with any displays last winter. IMHO best not charge it unless you know what you're doing (believe it or not there are lots of things that can go wrong with a simple battery charging operation), especially if the car is still under warranty.

 

[joemon1984]

joemon, I don't think that a low battery would cause problems with any displays unless the battery became really low - then the car wouldn't start. I'm not sure which display is giving you trouble - audio/nav or dashboard but either way I'd get it checked by your dealer. It sounds like you have a faulty regulator that controls the voltage to the display.

If the dealer reported the battery needed charging they may have given it a quick boost with a fast charger. Normally, you shouldn't need to charge it. It may have been a bit low when the dealer checked it but it should sort itself out with normal driving. I've seen mine get quite low - maybe about 50% charged from time to time but it recovers again without intervention (see my earlier post). No problems with any displays last winter. IMHO best not charge it unless you know what you're doing (believe it or not there are lots of things that can go wrong with a simple battery charging operation), especially if the car is still under warranty.

HiCx5,thanks for the valuable advice. I was referring to dashboard display which indicate mpg,total distance travelled and all. It looks like it lacks voltage for about one minute but gets to normal then. Not a big issue for me though. I actually spoke with the dealer and he said it is from extreme cold(-20 to -30 these days) which makes the display screen frozen. (Not sure if anybody else from Canada experienced it) thanks again for the reply. I decided not to mess around with the car electrical/ electronics .

 

[HiCx5]

Minus 20 degrees is a bit beyond my experience here (Australia). You're probably pushing the limits of the cars design at those temperatures. Like you say, it's not a big issue so probably best to just live with it but keep an eye on it in case it gets worse. I hope it doesn't!