gel or "normal" leisure batteries?

[betsy]

Hello everyone,

I know there is quite a lot out there on the subject but I still cannot find the specific answers that Im looking for.

About a year ago I changed Hymers. I decided to buy and have fitted to the latest 'van (a 2003 B584 on Fiat Ducato 2.8 chassis) twin 110AH acid (normal/old fashioned/wet) batteries and this was done by my local motohome solar power/satellite dish specialsts (always good, always helpful). The old battery (almost certainly the original one fitted by Hymer) was gel.

When the new ones were put in the fitter told me that as they were maintenance - free he would leave the charger on the "gel" setting. You guessed it - they are now no longer holding a charge for long! The company that fitted them have agreed to replace them with two others (same brand or any other that I may care to choose - obviously with a cash adjustment for more expensive ones).

I checked the old gel battery and it has a sticker on it saying "replace only with another gel battery"

I am aware that wet batteries (even maintainance-free ones) need to be properly vented, particularly if under the cab seats (my expired ones were not). I am happy to vent the replacements if I should go back to wet ones.

Do I go for gel or two good quality sealed wet ones - what setting should the charging block be set to?

I also note that the starter battery under the bonnet is a wet type and wonder if my charger is also called upon to charge this up when on hook up even though it has previously obviously been set to the gel position?

Grateful for any help

 

[Clive]

Maintenance free WET electrolyte batteries use a catalist in the cell tops to turn gasses back to water. But these only work if the batteries are correctly charged. Gel batteries are actually taken to a higher terminal voltage during the later phases of charge with multi-stage chargers and if the Gel charging algorythm is applied to wet electrolyte batteries they will gas excessively.

 

So, if you fit any variant of wet cell batteries you should set the charger appropriately to WET.

 

 

The alternator output voltage of 14 volts will not overcharge wet, gel or agm batteries or cause much gassing. This is why its the safest and most reliable method of charging batteries if you don't need them to be brimming full of charge. Typically 75%/80% charge is achieved with a 14 volt supply.

 

So perhaps a simple charger supplying a current limited 14 volt output and some batteries which are about 25% bigger than you calculate you actually need could be a long living reliable compromise??

 

C.

 

 

 

 

 

 

[Brambles]

"Gel batteries are actually taken to a higher terminal voltage during the later phases of charge with multi-stage chargers and if the Gel charging algorythm is applied to wet electrolyte batteries they will gas excessively. "

 

 

Clive, are you sure about this? Gel cells have a lower end point charge voltage than wet cells. AGM (Absorbed glass mat) are similar to wet.

Some batteries using additives to the lead plates need a slightly higher voltage but in general what I have said applies.

The settings should have been changed to wet cell, but leaving on gell would not have been detrimental as such. Excessive discharging and leaving discharged would be and is possible by using the gell setting you were not getting that extra bit of charge needed to prolong the time between needing to top up when vehicle is laid up. What happens when tht battery starts to lose charge and the voltage drops below approx 12.4 volts is the lead sulphates..not good for the battery. However the Wet setting takes the voltage a bit higher and can reverse some of the sulphation.

 

Now for the techies reading. All batteries sulphate as they discharge, this is part of thr process, but is termed soft sulphation and is reversable as the battery is recharged. If you take up to 14.4 volts most will be reversed but not at 14 volts. When thr voltage is below 12.4 volts for long periods the sulphation crytals become 'hard' and is known as hard sulphation and this is not so easily reversable except at much higher voltages approaching 16 volts and because of excessive gassing when it converts back to lead is not always deposited back on the plates and falls to the bottom of the battery. Anyway, ignoring all that. If you use a gell setting, your battery is not recovering properly after discharging. Gell will never last as long as a wet cell. Wet cells also have the advantage when you do get water loss you can top up.

 

Conclusion is, and is generally accepted Wet cells are far superior than gel. However you must vent a wet cell to the outside world.

NEVER USE wet setting for Gel

You can use gel or wet setting, but preferably wet setting for wet cells.

 

Jon.

 

[Derek Uzzell]

I'm sure I remember a letter in MMM, quite a few years ago, where two large Elecsol batteries had been fitted to a motorhome, replacing the original smallish gel battery. The motorhome's on-board charger had been left on the 'gel' setting and the letter-writer said that the replacement batteries had both failed within 12 months.

 

 

Brambles,

 

The technical information for my Hobby's CBE-made switch-mode on-board charger indicates a charging regimen for gel batteries that would seem to be potentially damaging for 'wet' batteries, but not vice versa.

 

The gel-battery regimen involves a maximum voltage of 14.3V and a maintenance voltage of 13.8V, with equivalent figures for the wet-battery regimen being 14.1V and 13.5V.

 

Charging is said to be carried out in 4 stages:

 

1. Maximum current until end-charge voltage is reached.

2. Then continuous charger operation for 90 minutes (wet batteries) or 8 hours (gel batteries) with constant voltage.

3. Constant voltage holding 13.8V (gel batteries) or 13.5V (wet batteries).

4. After 10 hours the charger enters stand-by mode and only resumes operation when the battery voltage is lower than 13V.

 

If these data are correct, it appears that the gel charging regimen is more 'rigorous' than the wet battery one.

 

As far as I'm concerned, the primary (perhaps sole) advantage of a gel battery being fitted to a motorhome for 'leisure' use is its genuine no-maintenance requirement, allowing the motorhome manufacturer to stick it in a totally inaccessible place. (Hmmm- perhaps that's not such an advantage after all!)

[Brambles]

Hi Derek - You are right! I have also found other Chargers saying the same. Gell has a higher voltage. I really am confused now and have to concede I am off the rails somewhere. I know it is complicated by so many different technologies used and some wet cells have higher voltages than others but looks lke gel technology may have moved on and I have not.

I am going to check this out and apologies as I am just confusing the issue by the looks of it.

Jon

[Clive]

So there you have it, ensuring a FULL charge comes with attendant risks. This is why vehicle manufacturers have not strayed from the 14 volt supply from the alternator with a current limit. Its the good safe compromise.

 

C.

 

[Derek Uzzell]

Returning to the final paragraph of betsy's original posting.

 

It seems commonplace now for motorhomes to have a gel leisure battery, but, as far as I'm aware, no manufacturer of the base vehicles (Fiat, Ford, Mercedes, etc.) used for European-built motorhomes fits a gel 'engine' battery.

 

In many cases this mix of battery types won't produce any potential charging conflict. Engine and leisure batteries will both receive 'wet-battery suitable' charging via the vehicle's alternator while driving - which may not to optimal for the gel battery, but shouldn't do it any harm - and, when the motorhome's on-board charger is operating, only the gel leisure battery gets charged. In such instances the on-board charger can be safely placed on its gel-setting and everything is hunky-dory.

 

However, other motorhome electrical systems (like my Hobby's) function differently when the on-board charger is operating. These prioritise output from the charger towards the leisure battery and - presumably when that battery has reached a particular state of charge - allow a low amperage charge (2 Amps maximum for my motorhome) to pass to the engine battery.

 

My Hobby's on-board charger has a gel-battery/wet-battery switch and this is set to "gel". I've no idea what regimen the charger follows when it's charging the 'wet' engine battery but, if it's using a gel regimen, I suppose there's the theoretical possibility of damage resulting. Can't say this worries me personally, as we rarely use 230V campsite hook-ups and I employ the motorhome's on-board charger only when I believe the batteries need it rather than whenever a mains power-supply is available. But I can appreciate it might concern motorcaravanners who prefer to have the charger running continuously when the opportunity arises.

 

There must be a good many folk who have motorhomes with the same wet/gel battery system as my Hobby's and who use the continuous charging technique. As I don't recall any mass complaints about engine battery failures, I assume (tentatively!) that there are no problems in practice.

[spospe]

Can I suggest looking at my post:

 

http://www.outandaboutlive.co.uk/forums/forums/thread-view.asp?tid=14089&posts=1

 

for a bit more on this subject.

 

Michael

[Nobby]

Derek Uzzell - 2008-12-13 6:26 PM

There must be a good many folk who have motorhomes with the same wet/gel battery system as my Hobby's and who use the continuous charging technique. As I don't recall any mass complaints about engine battery failures, I assume (tentatively!) that there are no problems in practice.

 

Hi Derek,

Some personal anecdotal evidence for you in this regard.

My own (nearly 7 year old) Hobby 650 with similar battery configuration to yourself is kept on a permanent charging regime via EHU when at home and at all other times both batteries receive a charge via the on-board solar panel/battery master.

I have just this month had to replace the wet lead acid engine battery which has been on the vehicle for the 7 years and 50k miles since it's manufacture. My two gel habitation batteries which have been on the vehicle almost as long are still in good and efficient working order.

 

I am quite happy with this level of reliability and I suspect most others would be also.

 

Best Regards,

Nobby

 

 

[snowchain]

Hi betsy,

Have just done the same on my Hymer as the original gel batteries had died!Took advice from Diamond Dave (practical motorhome tech.expert) and Hymer Uk,both very helpful and both advised move charger switch to wet;hope this helps

 

[betsy]

Boy I love MMM and these forums!!!

Thank you all for your contributions and advice!

Am following up some of the points raised (I am not entirely sure whether my onboard charger also tops up the vehicle battery, for example).

At the moment I am leaning towards two good quality "wet" leisure batteries with the charger's setting switched to "wet". As they will go under the driver's/passenger's seats any advice from any Hymer owner on "venting" routes would also be appreciated.

Am still open to any more advice if it is available.......................

Once again, many thanks to you all.

 

[Derek Uzzell]

betsy,

 

I believe the 'caravan' electrical system normally used by Hymer is based on Schaudt products. Whether your motorhome's on-board battery-charger can be used to charge the vehicle battery may depend on which Schaudt installation has been used, but the Schaudt control-panel employed by Pilote a few years ago did include that facility. The panel carried a switch with two vehicle-shaped icons alongside, one depicting the vehicle's rear end (ie. the 'caravan' section) and the other the vehicle's cab section. The switch would normally be set to 'caravan', but could be altered to the 'cab' position to charge the vehicle battery. In the latter case, an LED above the switch illuminated.

 

I'm sure that the 'all wet-batteries' approach is the right way to go, and it's definitely going to be the cheapest. Battery venting will usually use standardised parts (ie. a venting-tube of limited length that plugs into the battery), so you may be restricted as to the route the tubes takes. The shortest, simplest route will be the best and, if you are going to put the batteries beneath the cab-seats, that will mean drilling holes through the cab floor unless you are lucky enough to find some pre-existing holes. Should be straightforward enough as long as care is taken not to drill into anything important and any gaps around the venting-tubes where they pass to the outside are subsequently sealed.

 

I came across the following on the MTH forum. It applies to a later Hymer than yours, but might be useful.

 

http://www.motorhomefacts.com/forum-printtopic-1-55418-0-0-asc-viewresult-1.html