Desulphation

[PeterV]

I suspect that my less than 1 year old batteries are badly sulphated and need advice on the best way to desulphate them now and to keep them desulphated.

 

I am seldom connected to shore power and so rely on the main engine and twin alternators to charge, which from 50% takes about 4 to 5 hours but they don't hold charge and consumption in the summer (?) has been 240v fridge. a couple of hours lights, the usual assortment of shower pumps and other minor short use equipment, and the invertor.

 

There are 4 x 110 amp leisure batteries, 1 x 110 amp engine and 1 x 110 amp thruster batteries. charged with 2 x 80 amp alternators, which are linked with a smartguage.

 

240v is via a victron multiplus but except for rare hookups it is not used for charging.

 

I have never seen a smartguage voltage reading higher than 14.25v when charging and I am assuming (am I correct) that is the maximum voltage output from the alternators.

 

The smartguage reading when I start charging from say 60% will usually be about 13.9v and that rises gradually to 14.25v by the time charging reaches 90+%.

 

I will not get the best out of the alternators as cruising revs are about 1000 rpm and static charging about 850 rpm, although raising the revs gives only a relatively small additional charge voltage and is not worth the additional noise

 

After charging the voltage rapidly drops back after a few hours to about 12.4v and by morning is down to 12.2v.

 

What is the best method or gadget to give the batteries the higher voltage needed to reduce the sulphation please?

 

Peterv.

[stuart]

I'd be tempted to get an ammeter fitted into the battery bank(s) as well - I've a smartgauge unit and like it but theres nothing like being able to see the current being drawn/put back into the batterys - you can also see how well the alternators are doing then (including running at higher revs).

 

Stu.

[Chris Pink]

Sulphation is dealt with by a higher than usual charging voltage, easy said (many times on the forum) but not so easy to achieve in practice though if your Victron has a 'equalisation' setting then this will do it.

 

The 'i fly with goggles' brigade say they do it with 16V+ but only armed with water bottle and teflon underpants. It's not so easy to get dial-in-voltage battery chargers.

 

You can get anti-sulphation devices (Waeco, Stirling et al) which are unproven and don't claim to get rid of existing sulphation but rather prevent it.

 

14.8V is the recommended charge voltage for wet cells to avoid sulphation, again easy to say not so easy to achieve.

 

Your 440AH bank is possibly a bit small for an inverter running a 240V fridge at this time of year.

 

"I will not get the best out of the alternators as cruising revs are about 1000 rpm and static charging about 850 rpm, although raising the revs gives only a relatively small additional charge voltage and is not worth the additional noise"

 

What are the different voltages?

Edited July 21, 2008 by Chris Pink

[Gibbo]

One possibility would be to increase the charge voltage form the alternators as detailed here...........

 

http://smartgauge.co.uk/alt_mod.html

 

Your current charge voltage is ok for recharging but you also need to do periodic equalisation at 15.5 to 16.5 volts. So the mod to the alternator needs to be bypassed with a switch to put them back to normal.

 

I don't see any other option as you don't have regular shorepower available.

 

WARNING. You need to read up on desulphating/equalising batteries as you stand a decent chance of blowing yourself up if you do it wrong.

 

Gibbo

[Justme]

What about re pullying the engine / alternator to increase the charge at lower engine revs? I know it wont help the sulphating but will up the amps/reduce charge times.

 

Justme

[PeterV]

"I will not get the best out of the alternators as cruising revs are about 1000 rpm and static charging about 850 rpm, although raising the revs gives only a relatively small additional charge voltage and is not worth the additional noise"

 

What are the different voltages?

 

Chris - about 0.1 or 0.2v by increasing to 1000 or 1100 rpm

 

Hopefully the fridge should not take more than about 50amps per day even with the invertor loss

 

Peterv

[PeterV]

One possibility would be to increase the charge voltage form the alternators as detailed here...........

 

 

Gibbo

 

Gibbo - given that smartgauge is feeding both battery banks from both alternators would you need to modify both alternators or would just one be ok?

 

Peterv

[Keeping Up]

If you do run the alternator at a high voltage for desulphation, remember to make sure you first disconnect anything that may be damaged by the voltage

[Gibbo]

Gibbo - given that smartgauge is feeding both battery banks from both alternators would you need to modify both alternators or would just one be ok?

 

Peterv

 

Just one will do. Prefereably the one connected to the domestic bank otherwise SmartGauge might disconnect them unless you go into setup and change the high voltage disconnect.

 

Gibbo

 

If you do run the alternator at a high voltage for desulphation, remember to make sure you first disconnect anything that may be damaged by the voltage

 

Indeed. But there's lots more to be aware of hence....

 

QUOTE

 

WARNING. You need to read up on desulphating/equalising batteries as you stand a decent chance of blowing yourself up if you do it wrong.

 

UNQUOTE

 

Gibbo

[larkshall]

Just one will do. Prefereably the one connected to the domestic bank otherwise SmartGauge might disconnect them unless you go into setup and change the high voltage disconnect.

 

Gibbo

 

 

 

Indeed. But there's lots more to be aware of hence....

 

QUOTE

 

WARNING. You need to read up on desulphating/equalising batteries as you stand a decent chance of blowing yourself up if you do it wrong.

 

UNQUOTE

 

Gibbo

 

Ah yes what fun boiling dilute sulphuric acid and hydrogen, 'got a loight boy?'

 

 

 

Off this topic but in a way related what kit do you recommend if I was to re-wire boat for liveaboard, say using a twin alternator setup, and 12 by 2volt accumulators (225 amp hrs each) To provide mains, to power fridge/freezer, dishwasher, W/machine, plus tv/sound system hi-fi etc) EG that is inverter, shore charging sevice, battery management and control etc?. U often advise users of wiring problms, but I want to avoid them in first place

[Gibbo]

Off this topic but in a way related what kit do you recommend if I was to re-wire boat for liveaboard, say using a twin alternator setup, and 12 by 2volt accumulators (225 amp hrs each) To provide mains, to power fridge/freezer, dishwasher, W/machine, plus tv/sound system hi-fi etc) EG that is inverter, shore charging sevice, battery management and control etc?. U often advise users of wiring problms, but I want to avoid them in first place

 

Fridge/freezer, washing machine, dish washer, plus all the usual stuff?

 

Do you intend running this without the engine or a generator running?

 

Do you wish to go a few days without running the engine or charging up from shoreline?

 

Assuming you do, then add another zero to your "225 amp hrs each" fit a couple of 500 amp alternators and get a 250 amp mains charger.

 

 

Gibbo

[larkshall]

Fridge/freezer, washing machine, dish washer, plus all the usual stuff?

 

Do you intend running this without the engine or a generator running?

 

Do you wish to go a few days without running the engine or charging up from shoreline?

 

Assuming you do, then add another zero to your "225 amp hrs each" fit a couple of 500 amp alternators and get a 250 amp mains charger.

 

 

Gibbo

 

 

Sorry will have a generator for re-charge and running w/m and d/w.. 4.3kva continious rating, lombardini diesel

[Gibbo]

Sorry will have a generator for re-charge and running w/m and d/w.. 4.3kva continious rating, lombardini diesel

 

Ok. Do you intend doing most of your charging whilst cruising from the propulsion engine or when moored up from the genny (if so how often and how long do you think you'll be running the genny for)? That makes a big difference to the type of equipment you'd be best with.

 

Gibbo

[larkshall]

I would want to run genny as little as possible. I hope not more than an hour possibly 1.5 hrs each end of the day

[Gibbo]

I would want to run genny as little as possible. I hope not more than an hour possibly 1.5 hrs each end of the day

 

This is what I was expecting. It's a problem. From 50% to 100% the minimum recharge time to PROPERLY recharge lead acid batteries is around 6 hours and ideally much longer.

 

Even from 90% to 100% will take 4 hours or more to do it properly.

 

If you search this forum it has been discussed many, many times.

 

Note that the size of the charger make VERY little difference to this.

 

Gibbo