Solar vs Generator

[rusty69]

Just now, mrsmelly said:

So on a rainy January day you run a fridge, freezer and washing machine via solar? Do your panels keep batteries fully charged through the winter then?

No. That's why he wants some additional stick on ones too

[leeco]

2 minutes ago, mrsmelly said:

So on a rainy January day you run a fridge, freezer and washing machine via solar? Do your panels keep batteries fully charged through the winter then?

I’ve not had a 1000w in winter but I will get 30amps in winter I think which will charge them up. I’ve got a generator too.

 

end of the day you need both imo 

4 minutes ago, rusty69 said:

No. That's why he wants some additional stick on ones too

Them are for my dads camper van he’s bought ?

[Nick D]

26 minutes ago, Tony Brooks said:

And how many times have we heard that. How was it checked and when? 

Unfortunately I'm not a technical sort so rely on the advice from the engineer who says it was ok.  

 

It does seem that as a rule of thumb that 6-8 hours of cruising/engine running should be enough to meet the average electrical needs of a boat and that is what I have been doing. For those days when we only cruise for say 4 hours, I was trying to work out whether it's a better option to get solar or a generator or indeed do neither and just continue to run the engine for n short cruising days.

[Wanderer Vagabond]

47 minutes ago, WotEver said:

Impossible to answer because you haven’t given us your usage. Only a list of stuff that you have. You also haven’t said what power your alternator is. A power audit will tell us what you use and then, if you also tell us the size of your alternator, we can have a stab at estimating how long you might have to take to charge. 

 

As a general rule no, 4 hours isn’t enough. 6 to 8 hours is more like it. 

 

I don't think that your general rule is that general. Over the past 5 years we rarely cruise for more than 4 hours a day since we aren't in any rush to get anywhere and during that time our batteries have always reached 100% on the Victron meter (often in less that 4 hours, usually something like 3, even with the washing machine running). Whilst I know that someone is going to go into the technics of how a Victron meter can't be relied on etc.etc.etc but (tempting fate) our batteries are still doing fine so it is good enough for me, if it were giving me duff info the batteries would have failed a long time ago. As a rider I should add that we have a twin alternator set up, domestic and engine alternators, which obviously helps.

Edited August 2, 2018 by Wanderer Vagabond

[leeco]

My set up it’s fully charged by noon and I feel like I’m wasting power so put stuff on I don’t even need to use power.

 

most I’ve seen is 80amps coming into the batteries 

[Alan de Enfield]

41 minutes ago, mrsmelly said:

So on a rainy January day you run a fridge, freezer and washing machine via solar? Do your panels keep batteries fully charged through the winter then?

Can I have a go at answering that one ?

[Wanderer Vagabond]

4 minutes ago, leeco said:

My set up it’s fully charged by noon and I feel like I’m wasting power so put stuff on I don’t even need to use power.

 

most I’ve seen is 80amps coming into the batteries 

Is that good? When I start up it often charges at 60amps but only for  a short time, settling down somewhere about 30 - 35 amps for the long charge.

[leeco]

4 minutes ago, Wanderer Vagabond said:

Is that good? When I start up it often charges at 60amps but only for  a short time, settling down somewhere about 30 - 35 amps for the long charge.

On my controller it’s one of them outback ones that you can look back at data from 120 days I think and that was the highest I’ve seen looking back but normally when I look it’s putting 50amps in on a cloudy day it’s putting around 20amps but my batteries are always fully charged every day including cloudy days.

Edited August 2, 2018 by leeco

[Wanderer Vagabond]

12 minutes ago, leeco said:

On my controller it’s one of them outback ones that you can look back at data from 120 days I think and that was the highest I’ve seen looking back but normally when I look it’s putting 50amps in on a cloudy day it’s putting around 20amps but my batteries are always fully charged every day including cloudy days.

So it is possible/probable that the 80 amps was only for a short time before the regulator or whatever reduced it to a level the batteries are comfortable with. I was just thinking that charging at 80amps would put quite a lot of unwanted heat into the batteries if maintained for a long period.

[leeco]

4 minutes ago, Wanderer Vagabond said:

So it is possible/probable that the 80 amps was only for a short time before the regulator or whatever reduced it to a level the batteries are comfortable with. I was just thinking that charging at 80amps would put quite a lot of unwanted heat into the batteries if maintained for a long period.

You would only get 80amps for a very short time but my inverter plugged into power puts a constant 90amps in and I’ve never had issues but tbh I’ve never really plugged into power.

[Tony Brooks]

Some misunderstanding going on I feel.

 

1. No battery charging source will deliver "a constant 90 amps" or any other constant value unless you keep increasing the voltage and if you do you will soon wreck the batteries so any talk of "constant amps" is just wrong.

 

2. Basically its the batteries that determine the charging current so typically the current starts high, usually at or close to the alternator's rated output, and then over the next minutes the voltage will rise until the alternator (or solar) voltage regulator cuts in. Then over the next hours the charging voltage will stay more or less the same but the current will gradually reduce.

 

3. The OP seems to be concerned that his batteries are not charging fast enough/well enough with three to four hours engine running yet when asked for their power audit and the results of the alternator test are unable to give them. Answering "I am not very technical" is no help whatsoever in trying to solve  the perceived problem. It could be using more electricity than the charging regime can put back into the battered (well, that IS the issue) or the alternator not delivering sufficient output and that in turn can be because it is too small for the job you want it to do or its faulty. Then there are the batteries. Its unlikely because  we are told they are new but if they are badly sulphated or have an internal short then that would give similar symptoms.

 

An alternator with a blown diode will still raise the charging voltage but not as high as it should and it will produce charging current but again, not as high a sit should. This is why it is important to ensure the alternator is working properly.

 

4. Until we get the results of the alternator tests, the power audit, and some idea of the rested battery voltage at various times during the day and night we can only guess at the cause of the problem  if indeed there is one.

 

 

I think the only simple non-technical answer we can give the OP is that for year round use then a diesel generator plus suitable battery charger unless one is already fitted.

Edited August 3, 2018 by Tony Brooks

[Nick D]

I apologise for not being technically minded, so that is why I ask questions on here from people who are!  I paid a supposedly qualified engineer to replace my batteries and test the alternator.  When he said it was ok, I believed him as most non technical people would. I didn't know them about taking various rested readings - I do now, so thank you.

 

Rather  than go through the procedure you describe to see if there is indeed a problem, I was trying to establish earlier whether 'on average' 4 hours cruising was 'generally' enough to charge the batteries. It seems that opinion differs so I may well have to go down that route. Can you tell me what equipment I need to test the rested voltage and what details you need for a power audit?  I am not currently on the boat but hope to be in a few weeks.

 

Yes, I do have a battery charger and twin alternators.  The boat is just over two years old and appears (from a non technical person) to have generally good equipment levels.

[WotEver]

8 hours ago, Wanderer Vagabond said:

our batteries have always reached 100% on the Victron meter

It’s lying to you. 

 

8 hours ago, Wanderer Vagabond said:

Whilst I know that someone is going to go into the technics of how a Victron meter can't be relied on...

I shan’t bother with technicalities then, but I can assure you that it’s lying. 

[WotEver]

8 minutes ago, Nick D said:

Rather  than go through the procedure you describe to see if there is indeed a problem, I was trying to establish earlier whether 'on average' 4 hours cruising was 'generally' enough to charge the batteries. It seems that opinion differs... 

Those who differ either only discharge their batteries by a tiny amount (say up to 20% DoD) or they are simply wrong. Note that none of them are offering their tail current readings to support their assertions that their batteries are fully charged. They’re either guessing or believing faulty instrumentation. 

 

A battery at say 60% SoC will easily take 6 hours to fully charge, quite possibly longer. Ignore stupid comments about a ‘constant 60A’ or similar, the final charge rate will be only a handful of amps, as dictated by the batteries, not the charge source. 

[Nick D]

2 minutes ago, WotEver said:

Those who differ either only discharge their batteries by a tiny amount (say up to 20% DoD) or they are simply wrong. Note that none of them are offering their tail current readings to support their assertions that their batteries are fully charged. They’re either guessing or believing faulty instrumentation. 

So are you saying that 7/8 hours engine running is nearer the mark?

[WotEver]

1 minute ago, Nick D said:

So are you saying that 7/8 hours engine running is nearer the mark?

Or generator, or solar, or mains charger, yes. 

[Robbo]

3 minutes ago, Nick D said:

I apologise for not being technically minded, so that is why I ask questions on here from people who are!  I paid a supposedly qualified engineer to replace my batteries and test the alternator.  When he said it was ok, I believed him as most non technical people would. I didn't know them about taking various rested readings - I do now, so thank you.

 

Rather  than go through the procedure you describe to see if there is indeed a problem, I was trying to establish earlier whether 'on average' 4 hours cruising was 'generally' enough to charge the batteries. It seems that opinion differs so I may well have to go down that route. Can you tell me what equipment I need to test the rested voltage and what details you need for a power audit?  I am not currently on the boat but hope to be in a few weeks.

 

Yes, I do have a battery charger and twin alternators.  The boat is just over two years old and appears (from a non technical person) to have generally good equipment levels.

Although 4 hours won’t fully charge a modestly discharged battery to 100% as the tail end takes ages to charge, it should have charged the bulk of it.   Using a battery monitor, mainly the amp meter tells you what’s happening, without one it’s all just guess work.  It’s worth learning the basics because it will save you money in additional to having peace and quiet for when you don’t need to run the engine or generator.

 

For your initial question, you don’t need a generator, you are running your engine more than enough to do the job already.  Solar will help charge the final stage of battery charging as it’s not worth doing via engine methods.

[WotEver]

17 minutes ago, Nick D said:

Yes, I do have a battery charger and twin alternators.  The boat is just over two years old and appears (from a non technical person) to have generally good equipment levels.

I refer you to my previous reply:

https://www.canalworld.net/forums/index.php?/topic/97603-solar-vs-generator/&do=findComment&comment=2180580

[Robbo]

3 minutes ago, Nick D said:

So are you saying that 7/8 hours engine running is nearer the mark?

But it’s not worth fully charging the battery everyday using any diesel/petrol method.   I do my full charge  once a week. (No solar).   I do a bulk charge every other day, which takes around 3hrs.

[Nick D]

2 minutes ago, Robbo said:

Although 4 hours won’t fully charge a modestly discharged battery to 100% as the tail end takes ages to charge, it should have charged the bulk of it.   Using a battery monitor, mainly the amp meter tells you what’s happening, without one it’s all just guess work.  It’s worth learning the basics because it will save you money in additional to having peace and quiet for when you don’t need to run the engine or generator.

 

For your initial question, you don’t need a generator, you are running your engine more than enough to do the job already.  Solar will help charge the final stage of battery charging as it’s not worth doing via engine methods.

Thank you for a great answer!  Can you recommend a decent battery monitor?

 

[WotEver]

2 minutes ago, Robbo said:

Although 4 hours won’t fully charge a modestly discharged battery to 100% as the tail end takes ages to charge, it should have charged the bulk of it.   

4 hours will take an averagely discharged battery (whatever that is!) up to 80% or maybe a bit more. That’s where Solar scores (if it’s sunny) as it can slowly push in the ever-decreasing demand until the batteries finally get up to 100%. 

[Robbo]

Just now, Nick D said:

Thank you for a great answer!  Can you recommend a decent battery monitor?

 

Anything with a amp meter and volt meter.   A lot have a percentage gauge which becomes inaccurate over time so best left ignored.

 

just heading to work, I’ll get a list if done nice monitors if someone hasn’t beaten me to it later 

[WotEver]

5 minutes ago, Nick D said:

Thank you for a great answer!  Can you recommend a decent battery monitor?

You only require an ammeter (many available on Ebay for around a fiver), but ensure that it’s suitable for your setup - a high enough current rating. Then when installed you wait for your charging current to drop to around 1% of battery capacity at 14.1V+ to know that the batteries are full. A decent voltmeter will be required too, or even easier, a SmartGauge, to let you know where you are when discharging. 

Edited August 3, 2018 by WotEver

[Nick D]

3 minutes ago, WotEver said:

4 hours will take an averagely discharged battery (whatever that is!) up to 80% or maybe a bit more. That’s where Solar scores (if it’s sunny) as it can slowly push in the ever-decreasing demand until the batteries finally get up to 100%. 

We spend 3/4 weeks out of the marina at a time so I'm trying to weigh up whether it's worth the investment in solar or a generator.

[WotEver]

1 minute ago, Nick D said:

We spend 3/4 weeks out of the marina at a time so I'm trying to weigh up whether it's worth the investment in solar or a generator.

Yes I know. See post #23. 

And #46