Battery Voltage Dropping Quickly - Why ?

[Alan de Enfield]

Battery bank = 6x 230Ah FLA’s

Alternators = 2 x 70Amp

Battery Charger = Victron 50 amp

Solar Panel = 1 x 170 watt

Inverter = Sterling 1800 watt ‘Quasi Wave’

 

Yesterday we unplugged from the landline, and whilst the engines were warming up at 1200 rpm I checked the alternator outputs at 1.2 amp and 1.3 amp respectively so the batteries were as close to fully charged as I could get them.

Rate of charge about 0.2% of bank size.

 

Switched off the battery charger before going over to the inverter (didn’t want to try and invent perpetual motion !!!)

Inverter switched on.

 

Items left running from the batteries :

220v Freezer (via inverter) approx. 40Ah per day

12v Fridge approx. 27-30Ah per day.

2x phone chargers

2x Kindle chargers

Lap-Top charger (via inverter)

 

Cruised for 3.5 hours, then stopped and moored up at about 13:30.

 

As the afternoon progressed I noticed that the battery voltage appeared to be dropping rather quickly compared to normal – our normal daily usage is 100Ah-130Ah and the batteries tend to last us several (4 or 5) days.

By 7pm the batteries were down to 12.4 volts so ‘summut was seriously wrong’, at that rate, by morning, we would be on the wrong side of 12 volts.

 

The investigations started,

 

 

- to cut the story short I found that on disconnecting the land line I had not switched off the Immersion heater (1000 watt) and although it was on a timer it had been ‘on’ for 2 hours of the cruise and had been ‘on’ for 5.5 hours with ‘engines stopped’.

STUPID, STUPID mistake and one that I know is suggested (regularly) as one of the 1st things to check when your batteries 'unexpectedly go flat'

Switched off the immersion heater and battery voltage remained at 12.4 volts overnight, starting to pick up as the solar came into play at about 7 am.

Have now connected the generator and for the last 2 hours it has been putting 47 amps (via the battery charger) back into the battery bank – will continue to leave it running for a few more hours.

I know I could wire the immersion so it will not work via the inverter but we do, occasionally, use it to heat up the water and normally 30-45 minutes is enough (50-70Ah) If 'managed' correctly it is not a big issue.

I just need to ‘stick to the check-list’ and not get distracted or rushed into departing.

 

It doesn’t matter how many years you have been on the water – you can still make mistakes, fortunately this one was easily rectified with a bit of petrol and a few hours running the generator.

[rusty69]

Checklists are great. Trouble is, the older, and more forgetful I am becoming the more check lists I need. 

I need another checklist to check I've checked the checklist. 

Glad you sorted it

 

[Naughty Cal]

Funny bit as I was reading that my first thought was the immersion heater

[Alan de Enfield]

1 minute ago, Naughty Cal said:

Funny bit as I was reading that my first thought was the immersion heater

Yup - the number of times I have suggested that to folks, but, when it happens to you .........................

[cuthound]

The immersion heater on my boat terminates in a red 3 pin plug next to a 230 volt socket in the bedroom.

Dead easy to see if it's been plugged in or not.

We rarely use it, but I check it's not plugged in every time I pass it.

[Alan de Enfield]

After 1 hour on charge : 45 amps 'going in'

After 2 hours on charge : 47.3 amps 'going in'

After 3 hours on charge, now at 13.99 volts & 44.9 amps 'going in'

Solar is adding 3.5 amps

Still a way to go yet to get back to fully charged.

[Robbo]

One of the reasons I'm wiring up my boat to terminate high wattage items when running on inverter only.  Many combi's do this now for you but mine doesn't :(, so I have a contactor (relay) that only energies when on genny/shore that enables those MCB's.   This way everything is still going via the combi and taking advantage of it's reduced charging if going over the shore power current rating.

Edited October 10, 2017 by Robbo
Spelling as pointed out by System 4-50

[OldGoat]

1 hour ago, Alan de Enfield said:

Battery bank = 6x 230Ah FLA’s

Alternators = 2 x 70Amp

Battery Charger = Victron 50 amp

Solar Panel = 1 x 170 watt

Inverter = Sterling 1800 watt ‘Quasi Wave’

 

Wouldn't it be great if the multitudes of new boaters seeking advice on here got near to emulating your capacities? I recall arguing with folks thinking that 3 x 110Ah, one 70 amp alternator would be more than adequate...

Edited October 10, 2017 by OldGoat

[nicknorman]

We can power the immersion heater from the inverter or travelpower, which is useful to get hot water quickly with the engine started - the increased load on the engine is probably a good thing and helps to warm it up quicker. There is a domestic type appliance switch with a red neon light for the immersion heater, next to the Smartgauge etc so it is fairly obvious when it is on.

Hmmm, now I've said that I know what will happen next...

[rusty69]

9 minutes ago, OldGoat said:

Wouldn't it be great if the multitudes of new boaters seeking advice on here got near were wealthy enough to emulating your capacities? I recall arguing with folks thinking that 3 x 110Ah, one 70 amp alternator would be more than adequate...

Edited October 10, 2017 by rusty69

[Alan de Enfield]

2 minutes ago, OldGoat said:

Wouldn't it be great if the multitudes of new boaters got near to emulating your capacities? I recall arguing with folks thinking that 3 x 110Ah, one 70 amp alternator would be more than adequate...

I believe that the biggest/hardest/most important learning curve for a new boater is 'electrical management'

You can see when the toilet is getting full, you can see when the water tank is getting empty, you can weigh your gas bottles to find out how full they are, but 'electrics' is a mystery to most - they are just unable to understand why (for example) a 70 amp alternator doesn't 'put back into the battery' 210 amps in 3 hours

[Alan de Enfield]

Gone beyond the allowed time for editing - so update.

After 4 hours = 14.1 volts at 44.8 amps still 'going in'

 

Switched 'genny' off now - 175Ah replaced so will keep us going for (probably) a couple of days, or we may move  tomorrow.

[system 4-50]

2 hours ago, Robbo said:

One of the reasons I'm wiring up my boat to terminate high wattage items when running on inverter only.  Many combi's do this now for you but mine doesn't :(, so I have a contractor contactor (relay) that only energies when on genny/shore that enables those MCB's.   This way everything is still going via the combi and taking advantage of it's reduced charging if going over the shore power current rating.

corrected so that copying into search engines does not give smaller results.

[ditchcrawler]

1 hour ago, OldGoat said:

Wouldn't it be great if the multitudes of new boaters seeking advice on here got near to emulating your capacities? I recall arguing with folks thinking that 3 x 110Ah, one 70 amp alternator would be more than adequate...

It depends on what you want to do.

1 hour ago, Alan de Enfield said:

Gone beyond the allowed time for editing - so update.

After 4 hours = 14.1 volts at 44.8 amps still 'going in'

 

Switched 'genny' off now - 175Ah replaced so will keep us going for (probably) a couple of days, or we may move  tomorrow.

Still a good way off being fully charged and now you are starting another discharge cycle

[cuthound]

13 minutes ago, system 4-50 said:

corrected so that copying into search engines does not give smaller results.

I thought it was an expensive solution paying someone to turn high wattage equipment on and off. 

[WotEver]

1 minute ago, cuthound said:

I thought it was an expensive solution paying someone to turn high wattage equipment on and off. 

If he had a Hudson the Butler could do it

[Robbo]

39 minutes ago, system 4-50 said:

corrected so that copying into search engines does not give smaller results.

I blame the auto correct, not my spelling at all

[larryjc]

Did something similar with an electric kettle.  Left the marina and took off shore power.  Normally turned the inverter on with the engine but forgot.  After a few minutes motoring I asked SWMBO to turn it on.  Luckily I had a NASA BM2 mounted where I could see it from the steering position.  When I saw how many amps were dissapearing I soon worked out what it was.  Mind you all sorts of thoughts of short circuits and major charging issues shot through my head first.   Have to say the NASA is crap at SOC etc but brilliant at real time monitoring.

[nb Innisfree]

When our first battery bank was shot and we were just about to order replacements I accidentaly left the immersion on for several hours, totally flattened batteries which after a few days of 8 hr absorption charges sprang back into life and lasted another few months. 

[smileypete]

Just need an ammeter in view with a decent size display.

It may be possible to run more than one from a single shunt too, the single direction ones are quite cheap these days and easy to wire.

Edited October 10, 2017 by smileypete

[Mike Todd]

6 hours ago, Robbo said:

One of the reasons I'm wiring up my boat to terminate high wattage items when running on inverter only.  Many combi's do this now for you but mine doesn't :(, so I have a contactor (relay) that only energies when on genny/shore that enables those MCB's.   This way everything is still going via the combi and taking advantage of it's reduced charging if going over the shore power current rating.

Our new build has the immersion heater such that it can only run when the land line is connected and providing power. (or so I believe!)

[Robbo]

2 minutes ago, Mike Todd said:

Our new build has the immersion heater such that it can only run when the land line is connected and providing power. (or so I believe!)

If a Combi like a Victron these have two outputs, one for when only on shore line so if it wasn’t wired like this I would be disappointed in the builder!

[StephenA]

silly question but what wattage is the immersion heater? We keep thinking about getting one for our twin coil tank.

[cuthound]

Mine is 1000 watts, but I believe you can get the from 500 watts to 3000 watts.

[Naughty Cal]

12 hours ago, cuthound said:

Mine is 1000 watts, but I believe you can get the from 500 watts to 3000 watts.

Ours is 1000 watts as well. 

We sometimes run it from the inverter during the winter to help the engine warm up quicker as it can take an age to get to running temperature when the river temperature is colder.