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Gel vs Acid batteries - AGAIN!


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I am very grateful to Messrs Clive, Jon, Derek, Nobby et all who contributed such a lot of useful info to me last thread on what to replace my two 110am/hr wet batteries which failed after less than a year.

I had decided to go more "up-market" with two better quality lead acid replacements and actually rang the company that fitted the last pair (they are replacing them under guarantee) to tell them to go ahead and order them.

I also thought, having seen some very complimentary remarks about Schaudt (the German company that made my, bought second-hand in Germany, 2003 Hymer's Electrobloc EBL 99 G charger), to see if they could give any advice.

Schaudt deserve all the praise that I have seen them get - within 8 hours they had sent me a reply attaching the English translation of my charger's Instruction Manual. I have been studying its contents and my heart stopped for a bit when I saw that Schaudt say that whilst you can change from lead acid to gel you cannot change lead acid for gel!!!

Yes the Electrobloc had a switch to change the charge that it gives to suit either lead acid or gel. I though, at the end of the day, as long as the batteries were being given the right type of charge the power coming out of either type would be okay for my Hymer.

I recall that the original single leisure battery that came out of my Hymer before I went to the twin arrangement was a gel. It also bore a sticker on it saying replace only with another gel battery!

What do I do now..........................

Thank you all in advance for any advice you can offer.


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The EBL99G has this switch on the top right hand corner for selecting the different algorythms for WET or GEL batteries. The charging algorythm for GEL batteries used by many chargers will allow the battery voltage to go to a higher voltage during the penultimate charging phase than it does for a wet cell battery. Hence if the WET algorythm is selected it will safely charge both types of battery although the GEL battery will not be charged so fully. However if the charger is set to GEL and a WET cell battery is connected it can cause excessive gassing and overcharge.

If the charger charges both starter and leisure batteries it may be necessary to only use the WET cell algorythm.



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Schaudt's statement still seems odd (or at least it does to me!)


When a GEL battery is used on a motorhome it will invariably be employed to provide power to the vehicle's 'habitation' side. In such instances the motorhome's onboard battery-charger's WET/GEL switch (assuming it has one) should be set to "GEL". If the motorhome's charger is also able to charge the vehicle's 'motor' battery - either simultaneously with the habitation battery or separately - presumably the motor-battery (which will always be WET type) will also receive a charging regimen appropriate to a GEL battery.


This is what happens with my own motorhome - the battery-charger prioritises to the habitation battery (which in my Hobby's case is GEL type) and, once that battery has attained a certain level of charge, automatically passes a reduced level of charge (maximum 2A) to the WET motor battery. Should I choose to replace the present GEL habitation battery with a WET one, then I would need to select the "WET" setting on the Hobby's charger to ensure that the replacement battery is charged using the correct regimen. When the Hobby is being driven, the WET motor battery receives a WET charging regimen from the vehicle's alternator and, because the GEL habitation battery is parallel-coupled to the motor battery while en route, it gets the same charging treatment.


Hobby's User Manual warns that a habitation battery should only be replaced on a like-for-like basis, which, of course, is good K.I.S.S. advice. Nevertheless, in principle, a motorhome battery set-up where all the batteries are 'WET' and the charger is set to "WET" should be technically less controversial than a WET(motor)/GEL(habitation)/charger-set-to-GEL electrical configuration with its inherent potential charging conflicts.


I can appreciate that Hymer, having fitted a GEL habitation battery, would choose to add a sticker saying that this battery should only be replaced with another GEL type. If a WET replacement were used and the setting of the motorhome's charger were not changed from "GEL" to "WET", there would be a high risk of the new battery being damaged. There might also be the requirement to alter the installation itself (eg. to provide venting should the original GEL battery have been installed within the motorhome's living-area).


I could also understand Schaudt's documentation advising that, should a GEL battery be replaced with a WET one (or vice versa), then the charger's WET/GEL switch must be re-set to match. Plainly one CAN swap battery types around, but, provided that the person doing the swapping knows what they are up to and ensures that the charging equipment and batteries are compatible, problems should not occur. As it's basically 'safer' to replace a WET battery with a GEL battery than GEL with WET, I suspect Schaudt's warning falls into the category of "Advice for the Technically Challenged" rather than being a genuine "You CANNOT replace GEL with WET" prohibition.


Might be educational to go back to Schaudt and ask "Why not?"

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A further thought,

It may be that the battery installation is in a non ventilated compartment. If this is the case then only sealed batteries should be used unless something is put in place to provide adequate venting. (Like a tube going through a hole in the floor connected to the vent tube on the battery)




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Many thanks for your replies. Schaudt says consult the manufacturer ref swapping gel for lead acid but will e-mail the helpful service department again for further clarification. Will also call someone like Deepcar, who deal in used Hymers, to ask the same question.

I have also been thinking that the warning on the original gel battery (which is a quality German leisure type) could actually refer to it not being replaced with a "conventional" lead acid one rather than a "leisure" lead acid...................?

The Schaudt manual states that, when on hook-up the vehicle battery will also receive a charge (I think it said about 2 amps) and my vehicle battery is a lead-acid sealed-for-life type which is plainly the original. It is in fine condition.

It is starting to give me a headache as well!


The company


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betsy - 2009-01-10 7:09 PM


I have also been thinking that the warning on the original gel battery (which is a quality German leisure type) could actually refer to it not being replaced with a "conventional" lead acid one rather than a "leisure" lead acid...................?


No, I'm sure that's a Red Herring...


I believe that your Hymer's original battery arrangement is essentially no different from my Hobby's, with a conventional wet 'chassis' battery and a relatively low capacity gel 'habitation' battery.


From a technical point of view I would have absolutely no personal qualms over swapping my motorhome's gel habitation battery for a 'wet' one, though I would, of course, ensure that the charger's gel/wet switch was moved to its "wet" setting. In my Hobby's case I'd also need to think carefully about where I installed the replacement battery if it were a type that needed any maintenance (the present maintenance-free gel battery is totally inaccessible beneath a cab seat) and I'd need to address any venting requirements.


As a lot of motorcaravanners seem to do it without any apparent ill effects, I suppose it's OK doubling or trebling habitation-battery overall capacity and not enhancing the original electrical system to match.


I've noticed that, when extra batteries are an option on a new motorhome, it's sometimes the case that an upgraded battery-charger is part of the package. Also, where 'coupler/separators' (normally used in Continental motorhomes instead of a split-charge relay) are sold in French accessory magazines, there are different versions according to the battery Ah capacity and the maximum charge.

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