Engine and genny charging comparisons

[bigcol]

Okay I know I'm being lazy

But someone on the forum knows the answer

 

I want to know what's the most cost effective way to charge my battery's up

Battery's 5 x 110, plus 3 x 70 amp engine a BT battery's

 

Have 50 hp beta engine with 150 amp alternator, set to 1200'revs. Figures Per hour of use

 

Or Whisper/paguro 4000 Genny, running the inverter charger 80 amp. Figures Per hour of use

 

Both diesel

 

My heads full of cotton wall, thanks to new meds

Or is the difference so small.

 

Knowing that with the engine it heats the water

But with Genny can switch the emersion on anyway

 

Any help with answers would be appreciated

Col

Edited September 27, 2014 by bigcol

[b0atman]

if fuel is from same tank then dip tank run one system for one hour noting loads and battery levels .

then dip tank to find diesel useage

the next day repeat test on other system load is easy its getting batteries to similar state that is problem in this test

[smileypete]

Cost of fuel, engine likely wins as it directly heats water. Cost of wear and tear, genny likely wins.

 

As a very generous rule of thumb, if using engine for daily batt charging while stationary, I'd go for a decent cruise at least once and ideally twice a week.

 

cheers, Pete.

~smpt~

Edited September 27, 2014 by smileypete

[b0atman]

I suppose main difference would be more if generator was smaller

[bottle]

On my set up the 50 amp charger run from the generator will charge the batteries quicker than the 80 amp alternator on the engine.

 

The engine and generator almost equal each other on fuel consumption .

[Detling]

The costs will depend on how discharged your batteries are and how full you want to charge them.

 

Once your 5 domestic batteries are over 80% charged your alternator is unlikely to put more than 40 amps into them at 14.2+ volts, the generator will have the same problem. I find that the last 20% (according to smartgauge) for my 5 domestic batteries takes over 2 hours often 3 before smartgauge reads 100, and the current drops to below 4 amps whilst cruising.

 

So if you wish to fully charge your batteries the last few hours will be cheaper via generator as the batteries will limit the current, If you are only looking to bulk up the batteries to about 80% the higher current from the engine will offer a shorter charge time and free hot water.

[blackrose]

So if you wish to fully charge your batteries the last few hours will be cheaper via generator as the batteries will limit the current, If you are only looking to bulk up the batteries to about 80% the higher current from the engine will offer a shorter charge time and free hot water.

But since charging to 80% on a regular basis isn't generally a good idea as far as overall battery longevity is concerned, then that also points towards the generator as the most cost-effective.

Edited September 28, 2014 by blackrose

[kevinl]

At the risk of looking stupid (and not for the first time), if I runs my genny (1KW) then disconnected the earth that connects the batteries together so they all stand alone then use one battery charger for each battery would that not be better?

So if bigcol (the OP) ran his genny straight to the leisure batteries only and then just used the engine to top up the starter batteries if/when needed to chare or for hot water would than make any more sense. As col says "My heads full of cotton wall" when it comes to things like this.

K

[Rambling]

Can I ask why charging to 80% regularly is not a good idea for batteries ?

[Kae]

Rambling - it's charging to only 80% that's the problem. You should be charging to 100% at least once a week.

[Pykebird]

This is why I am in the process of getting a genny installed to both charge the batteries and heat the water. It will do both quicker than the engine and as I have no shore power will help when sun not out or trees fall down!

[blackrose]

At the risk of looking stupid (and not for the first time), if I runs my genny (1KW) then disconnected the earth that connects the batteries together so they all stand alone then use one battery charger for each battery would that not be better?

So if bigcol (the OP) ran his genny straight to the leisure batteries only and then just used the engine to top up the starter batteries if/when needed to chare or for hot water would than make any more sense. As col says "My heads full of cotton wall" when it comes to things like this.

K

Im not sure why you would want to charge each battery separately, but on the other part of your question, while I'm on shore power my battery charger charges my domestics and start battery via 3 output terminals (2 connected together go to domestics and the other one to the start battery. You should always use all output terminals on a multi output charger)，but when I'm away from my mooring and charging from the generator I connect all 3 output terminals together and use them to charge the domestics only.

 

Can I ask why charging to 80% regularly is not a good idea for batteries ?

Because it breaks one of the golden rules of charging/discharging: In general for long battery life you should avoid discharging your batteries to below 50% capacity and you should try to charge close to 100%. I think there was a third golden rule as well, but I've forgotten it!

Edited September 28, 2014 by blackrose

[Arthur Brown]

Can I ask why charging to 80% regularly is not a good idea for batteries ?

What's not charged, sulphates -which is bad for the battery. so if you charged to 80% the other 20% (distributed through the battery) can start to sulphate and die. Once that 20% is lost then further charging to 80% of the new lower capacity will let more battery sulphate, repeatedly til it's just a dead battery not a lead battery. Fortunately sulphating is a slow process so catching up with the charge state every week minimises the damage.

 

Best plan is a generator charge in the morning to put in the bulk charge at a high rate, then leave the solar to keep the lower current charge stages going to completion.

 

The reasons to run several chargers include -different charge voltage profiles for different battery chemistries, and running a charger so close to the generator rating that the start surge current trips the supply. (a 1000w charger will likely run off a 1000w genny, but will not start as the surge may be to great but two 500w chargers switched on separately will draw less surge current so may well run together happily.

 

As electricity is essential to modern life (-even on a boat!) and generated electricity is usually more prone to failure than the mains, having two means of getting electricity is a good idea.

 

Long term the best generator is the most neighbour friendly one, and one that burns cleanly -I've seen a full pea soup haze across a cut and floating the smell of unburned diesel into neighbouring gardens at ten at night before, it does bring ill repute onto all boaters.

Edited September 28, 2014 by Arthur Brown

[Rambling]

I just can't get my batteries up to 100% even with solar and a trip each week. Inverter kills them, but all the plugs are 240v. I think I need a generator fast.

Pykebird, I am the same. Can I ask which genny you are going for?

Edited September 28, 2014 by Rambling