Poor battery performance

kelbal

Hi Guys,
Took the MH out this week for its first proper trip since Christmas, and the battery performance was dreadful. Guessing it needs replacing, but I'm surprised as just last summer we were easily able to spend 2 nights stood still without hookup, running lights & water pump. But now the battery goes flat after only about 4 hours with just 2 lights on inside.
Its a 70Ah battery. Did some tests with multimeter to see if its charging OK.......

MH not running, not hooked up -> battery reads 12.63V
MH not running, hooked up -> battery reads 12.63V
MH running and revving accelerator (in neutral!) -> battery reads 14.5V

Should I expect to see 14.5V when hooked up, to indicate its charging? Anyways - the poor performance of the battery dying after 4 hours of just a light or 2 running was experienced after a 3 hour drive.

Have been regularly plugging in to house electrics recently, but earlier in the autumn/winter I suppose a couple of 2/3 weeks intervals could have gone by with no connection.

What do you think?

thanks

Aidan_M_M

Sounds like a dead cell in the battery P. also 70ah is a bit low IMO for a MH of your size. We'd have a 110 ah in there. 220v hookup should be minimum 13.5 volts.

kelbal

Aidan_M_M wrote: »

Sounds like a dead cell in the battery P. also 70ah is a bit low IMO for a MH of your size. We'd have a 110 ah in there. 220v hookup should be minimum 13.5 volts.

ok, thanks. Don't know much about batteries, can anything be done to repair a dead cell?
If the hookup voltage is the same as when I'm not hooked up - does that mean there's an issue with the charging system when hooked up? Or is it just another indication of a poor battery?

defike

A battery can be helped by discharging it a few times and recharging it.
Down to 11 volts and back up again 2 or 3 times.
When you plug in the mains is it set up to automatically keep the battery on charge or do you have to throw a switch to charge battery.
Mine is a home build panel van so I don't know how the factory ones are wired. I had 2 50aH batteries and changed them for 2 90aH.

niloc1951

defike wrote: »

A battery can be helped by discharging it a few times and recharging it.
Down to 11 volts and back up again 2 or 3 times.
.........................................

NOOOOOOOO NEVER do that.



In the yellow shortens battery life

In the red kills it quickly

AND, never leave a battery for any length of time in need of charge, that will also shorten its life.

defike

defike wrote: »

A battery can be helped by discharging it a few times and recharging it.
Down to 11 volts and back up again 2 or 3 times.
.

I concur, mostly, putting the battery into a few deep cycles reactivates the electrons deep in the plates. It's called conditioning. I would however stop the discharge at 12.0v/12.2v (unloaded).
Depends on the battery type some don't even like being below 12.3v.

Conditioning charges I find generally out-perform topping-up by 20% -ish.

Batteries will last longer in the summer because there is less need of lighting and the cold weather isn't discharging them.

As regards frequent charging; it's use them or lose them I'm afraid.

kelbal wrote: »

MH not running, not hooked up -> battery reads 12.63V
MH not running, hooked up -> battery reads 12.63V

No change; looks to me it's not charging off mains I'd expect it to jump somewhere between 13.1v and 14.4v on charge.

niloc1951

Sir Liamalot wrote: »

I concur, mostly, putting the battery into a few deep cycles reactivates the electrons deep in the plates. It's called conditioning. I would however stop the discharge at 12.0v/12.2v (unloaded).
Depends on the battery type some don't even like being below 12.3v.

Conditioning charges I find generally out-perform topping-up by 20% -ish.

Batteries will last longer in the summer because there is less need of lighting and the cold weather isn't discharging them.

As regards frequent charging; it's use them or lose them I'm afraid.



No change; looks to me it's not charging off mains I'd expect it to jump somewhere between 13.1v and 14.4v on charge.

The 'conditioning' of batteries refers to the old NiCd batteries used in earlier video cameras and other electronics back in the 1990's and are still available today at the cheaper end of 'rechargeable' batteries. These batteries have a kind of memory and if not flattened end up not delivering their full potential. Quality chargers for these type of batteries incorporated an initial phase where the battery was drained of any 'left over' power before charging commenced.

I've never heard of the principal being applicable to lead acid batteries though

Try it and see.

niloc1951

Sir Liamalot wrote: »

Try it and see.

I don't want to get into an argument, but if the battery is banjaxed there is nothing to loose. However if it still has some life ..................................

Not trying to start one, ...it works for me.
I get five days instead of four before hitting 12.2v from a full cycle. That's why I say 20%.
I know they don't have memories I imagined it was an excitation thing.

paddyp

How old it the battery, what kind of battery is it, agm, gel, flooded.

-Lead acid batteries don't like being deep discharged, at at 80% discharge they may only last 200 cycles at 10 -20% discharge cycles they can last thousands. If you regularly run them down you shortened their life.

-If you leave leave it substantially discharged sulfation sets in and the capacity begins to drop, after a couple of weeks you'll have lost significant capacity after a few months its scrap.

-A proper charger should switch to a low voltage when the battery is charged, if your charger is staying high when the battery can no longer accept a charge it is basically cooking your battery. Most chargers I've seen have a float voltage thats not optimum for battery life but good for battery performance in the short term. The appropriate voltage varies with temperature but almost no chargers bar expensive marine ones have temperature compensation, this means that if your battery is toasty warm in a closed compartment somewhere its almost certainly being overcharged.

-If its a gel battery 14.5V is too high regardless

Living out under the bonnet of a car in our climate is fairly ideal for a lead acid battery its rarely too cold, rarely too hot due to ventilation which driving, they are rarely discharged. Cars with smart charge alternators will adjust the charging voltage according to the air intake temperature and provide the optimum charge voltage. Silver calcium batteries can last 10-12 years in these kind of conditions.

In comparison the average leisure battery is often charged in a sealed compartment, too hot, regularly deeply discharged, regularly flat, overcharged by mains chargers, overcharged by alternators. They have a hard life.

Aidan_M_M

I say it regularly , the alternator is the main culprit for "wearing out" leisure batteries.

kelbal

Hi Guys,
Have investigated a bit more. Trying to narrow down if the battery is acting strange, or if the electrics in my MH are not quite right.

With a full charge the battery reads 12.64V
With no hookup I turned on all the lights and let a DVD play on the TV until the battery level on the system console thingy flashed red, and then it cut itself off. Then I put the multimeter across it again and it read 12.53V. Going by Niloc's table, this is still at 90% charge??
When I plug back into mains electrics, I get 12.63V again. I know this is lower than expected, but the battery does charge.
It was mentioned to me that I should get a car battery I know is good, and temporarily connect it to MH terminals, connect MH to mains, and see if I get the expected 13-14V across the terminals. This will indicate whether the hookup charging is ok. Still have to get around to this.

Anyway - should I be seeing less than 12.53V when the 12V system flashes low battery and cuts out?

thanks

Aidan_M_M

Most modern MHs cut off the power to the panel when the voltage drops to about 10.7 volts. Then the battery "recovers" the voltage to 12 ish with nothing consuming power. Put back on your multimeter and watch it while the lights etc are on and that's what you'll see.

niloc1951

The voltage in the chart I posted relates to when the battery is 'at rest' that is the effect of recent charging voltage or current draw has died away.

When being charge a battery will show a high voltage and while supplying current to appliances it will show a lowered voltage.

The true condition of the battery is its voltage when at rest.

If a battery is subjected to a high current draw its output voltage will drop, in some circumstances it will drop low enough to trigger cutouts designed to protect the battery. However if the battery is in good condition its voltage should recover in a relatively short time.

Think of it this way, when trying to start an engine a battery may go flat and no longer turn the starter motor, but when left for a while it will have recovered to turn the engine again.

Fully charged all things rightways the sitting voltage should be 12.8v unladen.
Some charge units only charge to 80% to prevent overcharging the batteries.
Perhaps your charging unit has one of these cut-offs.
One possible solution would be to try a stand alone charger;
(assuming it's a good battery)


Cheapo job;

http://www.halfords.ie/webapp/wcs/stores/servlet/product_storeId_11101_catalogId_15551_productId_270511_langId_-1_categoryId_212463

Good 'un;

http://www.satellitetv.ie/deep_cycle_batteries/elecsol_12v_10amp_charger

Also might be worth turning everything that's running off the leisure battery system off and take a reading of amps off the system to see if you have a parasitic drain you're unaware of.

kelbal

Really not sure whats going on with it. Had it plugged into mains for hours to charge, then turned on lights when unhooked and the electrics cut off after 1.5 hours. Tested regularly and never saw lower than 12.5 volts.
Could it be that the battery is fine, but the sensor in the motorhome electrics to cut the system off is faulty? It thinks the voltage is lower than it actually is, and cuts off when there's still plenty of power? Where would I investigate this?

I know its still possible a dodgy battery, but don't want to fork out €100+ on a new battery and get the same issues

Aidan_M_M

If the battery never drops below 12.5 before cutting out, I suspect a bad connection , positive OR negative in the supply to the charging system.

kelbal

Aidan_M_M wrote: »

If the battery never drops below 12.5 before cutting out, I suspect a bad connection , positive OR negative in the supply to the charging system.

But if there was a bad connection, surely the battery wouldn't be getting any charge when hooked up? It does though.

Aidan_M_M

But you're NOT getting full charge from mains.

kelbal

Aidan_M_M wrote: »

But you're NOT getting full charge from mains.

Just finished investigating the charging system. Did the following:

(1) Disconnected the output of the 12V charging system and put the multimeter across the terminals - reads 14.08V

(2) Reconnected above, and disconnected the two cables that are attached to the leisure battery terminals. With hookup connected, and these 2 cables unattached, I get 13.4V across them.

(3) Reconnect these 2 cables to the battery, reattach the hookup, and I get 12.8V (was reading as 12.63 yesterday) across the battery terminals.

Does this indicate the charging mechanism is OK, and the battery is in fact damaged?

Aidan_M_M

It doesn't really, as I said before you need it connected to any good battery to truly check it.

Turn everything off first. If you have a clamp meter check the amps off the positive lead from the battery with the clamp. If you have a simple meter then you need to disconnect the positive terminal and read the amps with the probes in series, so one probe on the positive terminal and the other on the positive lead you just disconnected. If you get a reading of 0a then I'd suspect a bad battery. If it reads anything above 0.5a then there's something else on causing a drain on the battery.

kelbal

Aidan_M_M wrote: »

It doesn't really, as I said before you need it connected to any good battery to truly check it.

Got my car battery into the MH and attached to system. With no hookup it read 12.03V. With hookup it initially started at 12.33V, then over the space of 10 minutes this slowly climbed to 12.65V and seemed to settle here.
Due to space restrictions the battery had to be on its side - not recommended to leave it like that I know, but not sure if this would make a difference with my test.
As I said earlier though, I did confirm that back at the charging system output that it is sending out 14V.
Not sure where that leaves me.

kelbal

OK, I'm an idiot. Have a snigger, and then help please!

I assumed that the battery that was inside, and not in the engine bay was the leisure battery. I've been looking at the van battery the whole time! Dawned on me when I had live disconnected and went to turn on the cab light to see better and it didn't work. Checked the MH lights, and they came on! I had read somewhere ages ago about leisure batteries being under seats, thats why I was thinking this.
But the thing is, for the life of me I can't see another battery at all. I've now read that the leisure battery can be in beside the van battery, or it can be under the passenger seat. Definitely nothing under the passenger seat. Its fairly compact under the driver seat, but just seams to be one battery there.
I'm obviously fairly familiar with my MH, but can't think where it would be.
Wouldn't be on the underbody outside would it?
And sorry for wasting your time so far, for those who've replied.

kelbal

kelbal wrote: »

Got my car battery into the MH and attached to system. With no hookup it read 12.03V. With hookup it initially started at 12.33V, then over the space of 10 minutes this slowly climbed to 12.65V and seemed to settle here.
Due to space restrictions the battery had to be on its side - not recommended to leave it like that I know, but not sure if this would make a difference with my test.
.

:eek: Don't leave a battery on it's side ever! They leak acid...even a sealed one is liable (through the hydrogen vents). Also the plates are designed to be submerged in fluid while sitting upright so you will not get accurate performance sideways. You will warp the plates charging while sideways!

If the car battery is 12.03v that's possibly banjaxed too...I'm surprised it'll start an engine that low but it might be the sidewaysness.

As regards finding the leisure battery best guess would be to chase the wires from the charger, it's probably nearby to prevent voltage loss on long cable runs.

Funny that the charging unit is charging the starter, if this is the case it could send current backwards through the alternator which would be bad. ...I guess someone may know better on this. Easy enough put some diodes in there I guess.

kelbal

Found it, in a sub-floor compartment, accessed from a ground level cupboard. Some glued in carpet was concealing it.

Voltage readings now seem normal. When hooked up I'm getting 13.7V.
With no hookup and I run lights & TV, when it gets down to one bar on the level indicator, I'm reading 11.1V

So I guess its just dead cell then that accounts for the poor performance?

Oh, and BTW, it is 95Ah.

Sir Liamalot wrote: »

Funny that the charging unit is charging the starter

hmmm, what from what I've previously said makes you think it actually is doing this?

thanks guys

kelbal

kelbal wrote: »

With no hookup it read 12.03V. With hookup it initially started at 12.33V, then over the space of 10 minutes this slowly climbed to 12.65V and seemed to settle here.
.

.

kelbal

ok - but could that not just have been because I put the battery on its side, resulting in fluctuating readouts as the acid shifts about? The jump from 12.03 to 12.33 might not have had anything to do with the hookup, might have just adjusted to that in the time it took me to go out, plug in electrics, and come back to test.

kelbal

kelbal wrote: »

ok - but could that not just have been because I put the battery on its side, resulting in fluctuating readouts as the acid shifts about? The jump from 12.03 to 12.33 might not have had anything to do with the hookup, might have just adjusted to that in the time it took me to go out, plug in electrics, and come back to test.

More than likely.



11.1v...more than one dead cell methinks...banjaxed

I recommend these as a replacement they're more durable than most. They withstand deep depletion quite well.

http://www.satellitetv.ie/deep_cycle_batteries/elecsol_125amp