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Tasemu

Beta Diesel Generator and a Victron Multiplus.

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Hi, on my new boat I have a diesel genny installed which supplies 240v throughout the boat. I also have a 20a sterling battery charger and 480ah of sealed lead acid batteries. Currently charging the batteries takes a very long time with the small charger and I am considering swapping it out for a Victron Multiplus Compact, with the added bonus of having an inverter if needed. I've heard that generators and inverter-chargers can have issues so I wanted to get a general consensus and any advice from you all before moving ahead with a fairly heavy purchase.

 

Cheers for any and all advice as always!

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Should be fine. You don’t give any details about the generator though. You just have to avoid overloading the genny with the Combi. Depends therefore on the genny output and the Combi 12v output. With Victrons you get the remote panel which has a knob that you can adjust to limit the maximum mains input current. Probably a good idea to get that so you can limit the demand from the genny if it’s not big.

 

Victrons can also be a bit funny about input waveform but there is a setting that you can change to make it more tolerant (no idea why this isn’t the default setting!).

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Smallest Beta gennie is 6.7 KVA which Beta say is 23 amps. Make sure you get Victron Multiplus with 50 amp transfer switch rather than the standard 16 amp.

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2 hours ago, Tasemu said:

Hi, on my new boat I have a diesel genny installed which supplies 240v throughout the boat. I also have a 20a sterling battery charger and 480ah of sealed lead acid batteries. Currently charging the batteries takes a very long time with the small charger and I am considering swapping it out for a Victron Multiplus Compact, with the added bonus of having an inverter if needed. I've heard that generators and inverter-chargers can have issues so I wanted to get a general consensus and any advice from you all before moving ahead with a fairly heavy purchase.

 

Cheers for any and all advice as always!

 

and apart from a shorter bulk charging time that is typically less than an hour or so the charging will still take a long time. Just upping the potential charging current does little to shorten acceptance time because its the batteries that are controlling the  acceptance current.

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1 hour ago, Tony Brooks said:

 

and apart from a shorter bulk charging time that is typically less than an hour or so the charging will still take a long time. Just upping the potential charging current does little to shorten acceptance time because its the batteries that are controlling the  acceptance current.

Only up to a point, and with a decent domestic battery bank of say 440Ah at 50% SoC that will be 11 hours even if the charger can put in 20A towards the end (which it won’t be able to). If the charger is 100A then probably it will be able to put that in for the first hour so straight away one has saved 4 hours.


It has been interesting observing our battery’s behaviour with my new home made regulator - by holding the current at max until 0.1v or so of the regulated voltage, the mid-period charge is done at a much higher current and is much quicker, even though the old regulator was a nominal 14.5v or so. But the old regulator would start to significantly decrease the current with more than 0.5v to go to the nominal regulated voltage.

 

So in reality whilst there is of course some truth in the statement “the batteries are controlling the acceptance current”, that is only part of the story. The charging source’s ability to deliver the regulated voltage at high current (or not, with a conventional regulator) is the other half of the story.

Edited by nicknorman

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So i'm confused haha, i'm hearing from these comments (though I bet i'm misunderstanding) that i do not need a bigger battery charger because the batteries wont take a higher charge?

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10 minutes ago, Tasemu said:

So i'm confused haha, i'm hearing from these comments (though I bet i'm misunderstanding) that i do not need a bigger battery charger because the batteries wont take a higher charge?

After the first period of charging it will be the batteries that in effect control the charge.

 

In Nick's case he has built his own regulator that holds the voltage at a higher level for longer than the standard alternator regulator. As the current flowing is proportional to voltage charging at a higher voltage will deliver  more amps but unless strictly controlled at the  risk of battery damage.

 

Now, Nick is talking about alternator charging while you are talking about charging from a higher output charger and that is where the difference is. If your charger part of the (Combi-unit) has a higher acceptance charge voltage than the alternator or your small charger then it will shorten the acceptance charge time as well as the bulk charge time but, and its a big but chargers often drop into float far too early so that extends time to fully charged. I expect both your old charger and the new combi-unit will tend to do this.

 

You have to decide if the unknown reduction of charging time is worth the expense. If fact  if the new unit drops into float earlier than the old one it may lengthen the charging time. the only way to find out is to carefully study the specs with a deal of scepticism.

 

It is a fact that for lead acid batteries once the bulk charge is over (the new charger will speed that up) its the batteries that limit the current at any given voltage.

 

You may find the new device pulses the acceptance voltage like the Adverc does and if so that will shorten the acceptance charge time but by how much is open to question.

 

My gut feeling is that the change is unlikely to make the degree of difference you think it will but who knows until you have sent the money.

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27 minutes ago, Tasemu said:

So i'm confused haha, i'm hearing from these comments (though I bet i'm misunderstanding) that i do not need a bigger battery charger because the batteries wont take a higher charge?

The batteries will take a (much) higher charge at the start of the charging process. Near the end of the charge they won’t even be taking 20A (a full charge occurs when the charge current falls to around 1 or 2% of capacity ie 4.8 to 9.6A in your case). It is true that there are diminishing returns to having a high current charger, but in your case a 20A charger is very small compared to the 480Ah batteries and so there will be significant benefit to having a bigger charger.

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7 minutes ago, Tony Brooks said:

After the first period of charging it will be the batteries that in effect control the charge.

 

In Nick's case he has built his own regulator that holds the voltage at a higher level for longer than the standard alternator regulator. As the current flowing is proportional to voltage charging at a higher voltage will deliver  more amps but unless strictly controlled at the  risk of battery damage.

 

Now, Nick is talking about alternator charging while you are talking about charging from a higher output charger and that is where the difference is. If your charger part of the (Combi-unit) has a higher acceptance charge voltage than the alternator or your small charger then it will shorten the acceptance charge time as well as the bulk charge time but, and its a big but chargers often drop into float far too early so that extends time to fully charged. I expect both your old charger and the new combi-unit will tend to do this.

 

You have to decide if the unknown reduction of charging time is worth the expense. If fact  if the new unit drops into float earlier than the old one it may lengthen the charging time. the only way to find out is to carefully study the specs with a deal of scepticism.

 

It is a fact that for lead acid batteries once the bulk charge is over (the new charger will speed that up) its the batteries that limit the current at any given voltage.

 

You may find the new device pulses the acceptance voltage like the Adverc does and if so that will shorten the acceptance charge time but by how much is open to question.

 

My gut feeling is that the change is unlikely to make the degree of difference you think it will but who knows until you have sent the money.

Something like the victron multiplus mentioned, has a lot of configuration options. “Out of the box” you are right, there is a risk (even a probability) of it going to float too early, however there are a number of settings that can be optimised to prevent that.

 

For a Combi not used to connect permanently to shore power there is not much point in having a float mode at all, and so it is better to configure it to have the same voltage for absorb and float, so even when it notionally goes to float, nothing actually changes.

 

i know where you are coming from with all this, but ultimately is is wrong to say “it doesn’t matter how small a charger is, there won’t be much effect on charging time”. Consider a 1A charger etc! There are diminishing returns but the OP is currently well below any sort of optimal charge capability in the cost/charge time compromise.

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4 minutes ago, Loddon said:

 

And don't start me on Victrons adaptive charging its rubbish.

Yes, needs to be disabled.

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20 hours ago, nicknorman said:

Only up to a point, and with a decent domestic battery bank of say 440Ah at 50% SoC that will be 11 hours even if the charger can put in 20A towards the end (which it won’t be able to). If the charger is 100A then probably it will be able to put that in for the first hour so straight away one has saved 4 hours.


It has been interesting observing our battery’s behaviour with my new home made regulator - by holding the current at max until 0.1v or so of the regulated voltage, the mid-period charge is done at a much higher current and is much quicker, even though the old regulator was a nominal 14.5v or so. But the old regulator would start to significantly decrease the current with more than 0.5v to go to the nominal regulated voltage.

 

So in reality whilst there is of course some truth in the statement “the batteries are controlling the acceptance current”, that is only part of the story. The charging source’s ability to deliver the regulated voltage at high current (or not, with a conventional regulator) is the other half of the story.

 

Back in the day when I was on the tools, one of my jobs was to charge the main batteries at the London International telephone exchanges.

 

In those days the charging source was rectifiers with a manual override for charging.

 

We used to charge at 25% of the batteries capacity for the bulk stage of the charging process. Charging at greater rates caused a rapid increase in battery temperature, necessitating a reduction in charge rate until the temperature dropped, which resulted in increased, rather than reduced overall charge times.

 

One of my team was an ex-submariner, who said that the on the diesel-electrc submarines he worked on, battery charging times were reduced by blowing compressed air through the charging batteries to dislodge the hydrogen bubbles from the plates. 

 

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