Pete-B Posted January 6, 2016 Share Posted January 6, 2016 In terms of voltage at what level of discharge will a nearly new, original engine battery, become un-recoverable or be in danger sulphating? Link to comment Share on other sites More sharing options...
Derek Uzzell Posted January 7, 2016 Share Posted January 7, 2016 The following links explain battery sulphation/desulphation http://batteryuniversity.com/learn/article/sulfation_and_how_to_prevent_it https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery You’ll realise from the advice that there’s no simple voltage/level of discharge thresholds below which a battery would become so sulphated that it could not be revived by a battery-charger with a ‘desulphation’ capability. The rule of thumb seems to be that the older the battery and/or the longer it remains in a low state of charge, the less likely recovery to full working order will prove practicable. The Wikipedia link above includes a table in the “Terminal Voltage” section that lists terminal voltage against approximate percentage charge. Personally, if I had a vehicle sitting idle for an extended period (eg. a motorhome) I would not want to allow its 12V starter-battery’s voltage to drop below 12.30V. (Might to useful to know why you’ve asked this...) Link to comment Share on other sites More sharing options...
Pete-B Posted January 7, 2016 Author Share Posted January 7, 2016 Hi, The reason I asked was, the van is in storage and after it had had been stood for about four weeks the engine battery was showing a voltage of 11.8 volts but yet there was still sufficient power to start the engine. Not knowing too much about auto electrics I wonder how often this could happen before permanent damage occurred. I do have a 80watt solar panel fitted which through a regulator/controller is supposed to monitor both engine and leisure batteries but I guess with low light at this time of the year it struggles a bit. I've got two 100amp leisure batteries and I'm told, one way to solve the problem would be to fit a battery master which would prevent the engine battery from running to low. Link to comment Share on other sites More sharing options...
Brambles Posted January 8, 2016 Share Posted January 8, 2016 Its possible your controller is set (or wired up) to give priority to the leisure batteries. It might be worth altering ( if it can be done) to give priority to the engine battery when in storage. Then keep an eye on what volts the leisure battery falls to. You might find it will work better. It is also possible if your leisure batteries are getting a bit tired they are just self discharging too much and grabbing all the power from the solar panel when there is decent daylight. Link to comment Share on other sites More sharing options...
Tracker Posted January 8, 2016 Share Posted January 8, 2016 My inclination would be to disconnect, or better still isolate via an accessible switch, the leisure batteries when the van is in store and send all of the meagre winter solar charge to the starter battery - assuming the solar regulator will allow that without damage to it caused by no output load. That way the leisure batteries should not drain by any significant ammount and the engine should always start. Having started the engine I would let it idle for a minute or two to fully replenish the starter battery and then turn on the leisure batteries so that they could take some charge from both the solar and/or the alternator. That might protect what we are told is a seemingly delicate alternator from having to work too hard and commit hari kari! Link to comment Share on other sites More sharing options...
Pete-B Posted January 8, 2016 Author Share Posted January 8, 2016 Thanks for the quality information and advice. The van is only 6 months old so all three batteries are virtually new and in good condition. Before I put the van in storage I did indeed swop the cables over so that the engine battery has priority. Then about 6 weeks ago I did disconnect the leisure cable altogether, (after seeking advice from Solartechnology), so the engine battery gets whatever feed from the panel there is, which is not a lot this time of the year, About every 4 weeks I give the van a good run out (about 20-25 miles and last week I brought it home and hooked up to power for a couple of days to bring all three batteries up to maximum. But my point is, with two 100amp leisure batteries which don't seem to loose any power, or very little because I use the shutdown button on the Sargent unit, would it be advisable to fit a Batter Master and re-connect the leisure side cable to the regulator/controller and even maybe dis-connect the engine side. But not knowing a lot about auto-electrics am I just talking rubbish? Link to comment Share on other sites More sharing options...
Tracker Posted January 8, 2016 Share Posted January 8, 2016 I'm not at all sure that you have a problem or that you need to do anything as you seem to have it pretty much sussed! Does this all revolve around the low 11.8 volts from your starter battery? If so and this reading was taken with the ignition on then maybe with the load of all the electronics and warning lights on it is not so bad? If the true voltage were 11.8 the battery would be far too flat to even turn the engine over let alone start it. To get a true comparison of the battery state could you check the voltage without the ignition on? This would mean lifting the carpets and accessing the starter battery under the cab floor and putting a digital voltmeter across it's terminals with nothing switched on and you may well find that the voltage is much closer to 12.5 volts give or take? Of course, I could be wrong, in which case the battery drain is simply greater than the solar input over time in winter and there is not a lot you can do about that except ensure that what solar energy there is does in fact reach the starter battery an/or maybe talk to Fiat to possibly get the base vehicle electrics checked by them to ensure that there is not an undue power drain when not in use. Link to comment Share on other sites More sharing options...
Keithl Posted January 8, 2016 Share Posted January 8, 2016 Pete, Is your solar controller wired directly to the starter and leisure batteries or through the Sargent control panel? I suspect directly as you mention swapping the wires over. If so, as your MH is only six months old, does your Sargent unit have a dedicated solar input? I read the A & N Caravans post recently recommending ALWAYS using the Sargent input or this can cause issues with battery management. Secondly someone suggested adding a Battery Master, from memory these do not work well with Sargent power supply units and I am sure I have read of owners having to remove them because of serious problems after fitting. Caveat Emptor! HTH, Keith. Link to comment Share on other sites More sharing options...
Pete-B Posted January 8, 2016 Author Share Posted January 8, 2016 Re the engine battery, there was nothing at all switched on and I got the 11.8VOLT reading from the sargent display unit which, I've always been led to believe, are pretty accurate,but the engine did start without a problem. Perhaps next time I go over I will take my multimeter and check with that! Link to comment Share on other sites More sharing options...
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