Anders_P42
Well-Known Member
How many weeks are you going to run this setup, is the charger going to overheat / die supplying 25A 24/7 ?
Battery charger with no batteries: crazy or what?
- Thread starter MapisM
- Start date
jfm
Well-Known Member
The charger should be continuously rated. I mean, it would be pretty bad/surprising if it were not
MapisM
Well-Known Member
Thanks again everybody for your support.
Following the order of your questions/comments:
@elton: 4/5 years is actually pretty good for domestic batteries. I wouldn't expect them to last much longer even with your relay trick...
@monique: I understand that by "do it right once" you mean the same that also Deleted User suggested afterwards, i.e. replace the whole battery bank.
Of course, that would be a possibility, but having in mind to redesign a bit the AC circuit, replacing the charger with an inverter, and being at the end of the season, it seems logical to install the new fresh batteries right before next summer.
As long as I have a decent alternative that can work for a few weeks, obviously - which is the point of the whole thread.
@newWave+rich: yup, I already removed all the short "bridging" cables completely. I took the pic just after trying the batteryless configuration...
@jfm: yeah, in hindsight it was a bit of blonde moment question from my part... I don't know what I was thinking, with my concern on the current flowing along the cables still connected to one terminal of each battery!
Re. the dash electronics instead, I was actually thinking to use none. In fact, I'm probably going out just a few other times, for short daily trips in places round the corner, which I know like the back of my hand, so flying by the seat of my pants is not a problem at all.
The only thing which I like to turn always on, if nothing else because without it I have no rudder indicator, is the A/P. But I already gave it a try, and it seems to work just fine! Which btw means not only the pump, but also the display, the control unit and the electronic compass. So, I guess that the charger DC output must be not too bad, all considered...
@Deleted User: see previous answer to monique. But if you get in touch with your SL man, I could also use a supply of fresh batteries with no bill!
@Pinnacle: yep, there are more cables than would be strictly necessary in theory. I suspect that they simply used multiple (relatively) small cables rather than a much bigger single cable just because they are easier to handle.
Anyway, I must admit that the whole onboard electrical system is not the most elegant bit of boatbuilding which I've ever seen....
@Anders: I thought about it, but aside from agreeing with jfm that the charger is bound to be continuously rated (though not having any manual I can only hope it is), there are two other reasons why I expect it to withstand the job (and in fact, it never felt warmer than usually, so far):
1) it isn't actually supplying 25A 24/7. It's more like 40A for a few seconds when I use for instance the passerelle; 20 to 25A when all fridges are running, some (led) lights are turned on, and possibly one shower or WC pump; 5 to 10A when only one fridge is running; close to nothing for the rest of the time.
2) whatever the charger is now supplying with no batteries, it should have supplied also with the batteries, if you think about it. I mean, if you live onboard for say one month, with fully charged batteries, and at the end of the month you still have your batteries fully charged, it means that the overall current consumption of that month has been supplied by the charger. Yes, the charger supply would be "smoother" with the batteries, but the overall Ah can only be the same, unless I'm missing something. Therefore, I would think/hope that the more "irregular" demand to the charger, in itself, shouldn't make its life much harder, over a given period of time.
Following the order of your questions/comments:
@elton: 4/5 years is actually pretty good for domestic batteries. I wouldn't expect them to last much longer even with your relay trick...
@monique: I understand that by "do it right once" you mean the same that also Deleted User suggested afterwards, i.e. replace the whole battery bank.
Of course, that would be a possibility, but having in mind to redesign a bit the AC circuit, replacing the charger with an inverter, and being at the end of the season, it seems logical to install the new fresh batteries right before next summer.
As long as I have a decent alternative that can work for a few weeks, obviously - which is the point of the whole thread.
@newWave+rich: yup, I already removed all the short "bridging" cables completely. I took the pic just after trying the batteryless configuration...
@jfm: yeah, in hindsight it was a bit of blonde moment question from my part... I don't know what I was thinking, with my concern on the current flowing along the cables still connected to one terminal of each battery!
Re. the dash electronics instead, I was actually thinking to use none. In fact, I'm probably going out just a few other times, for short daily trips in places round the corner, which I know like the back of my hand, so flying by the seat of my pants is not a problem at all.
The only thing which I like to turn always on, if nothing else because without it I have no rudder indicator, is the A/P. But I already gave it a try, and it seems to work just fine! Which btw means not only the pump, but also the display, the control unit and the electronic compass. So, I guess that the charger DC output must be not too bad, all considered...
@Deleted User: see previous answer to monique. But if you get in touch with your SL man, I could also use a supply of fresh batteries with no bill!
@Pinnacle: yep, there are more cables than would be strictly necessary in theory. I suspect that they simply used multiple (relatively) small cables rather than a much bigger single cable just because they are easier to handle.
Anyway, I must admit that the whole onboard electrical system is not the most elegant bit of boatbuilding which I've ever seen....
@Anders: I thought about it, but aside from agreeing with jfm that the charger is bound to be continuously rated (though not having any manual I can only hope it is), there are two other reasons why I expect it to withstand the job (and in fact, it never felt warmer than usually, so far):
1) it isn't actually supplying 25A 24/7. It's more like 40A for a few seconds when I use for instance the passerelle; 20 to 25A when all fridges are running, some (led) lights are turned on, and possibly one shower or WC pump; 5 to 10A when only one fridge is running; close to nothing for the rest of the time.
2) whatever the charger is now supplying with no batteries, it should have supplied also with the batteries, if you think about it. I mean, if you live onboard for say one month, with fully charged batteries, and at the end of the month you still have your batteries fully charged, it means that the overall current consumption of that month has been supplied by the charger. Yes, the charger supply would be "smoother" with the batteries, but the overall Ah can only be the same, unless I'm missing something. Therefore, I would think/hope that the more "irregular" demand to the charger, in itself, shouldn't make its life much harder, over a given period of time.
fireball
Well-Known Member
Forgive me if I've misunderstood - the Charger is being powered by shorepower? If so, it doesn't matter if the Nav electronics work fine on it or not - as soon as you cast off you'll have nothing powered by the domestic battery bank as you don't have one (unless you reconnect it!) ... Of course you could have your instruments powered by the engine battery ...
jfm
Well-Known Member
When at sea he has genset that could power the batt charger and thence the helm electronics (if he wanted to)
fireball
Well-Known Member
MapisM
Well-Known Member
Actually, I guess I could also hotwire the alternator which recharges the domestic batteries bank (as previously suggested by jfm), hence getting DC while cruising without turning the genset on.
Not sure it's worth experimenting further, though....
...for just a few other hours out now and then, I might as well fire the genset, and be done with that.
I would need it while anchored anyway, after all.
But I will update the thread if I'll decide to give that a try!
Not sure it's worth experimenting further, though....
...for just a few other hours out now and then, I might as well fire the genset, and be done with that.
I would need it while anchored anyway, after all.
But I will update the thread if I'll decide to give that a try!
Pinnacle
Well-Known Member
jfm. It appears you were, as always, correct!! [Mumbles to himself/ON] I should have know better after all these years................................) [Mumbles to himself/OFF]
jfm
Well-Known Member
jfm. It appears you were, as always, correct!! [Mumbles to himself/ON] I should have know better after all these years................................) [Mumbles to himself/OFF]
I dunno. When I look at that pic some more I think the whole things needs a good sort out. Normally you'd parallel the two banks. Ie the two batteries on the left making 24v would be paralleled to the two on the right. But in this case the two 24v banks seem to be serving somewhat different loads, eg the two retro-fitted grey cables that you can see in the top right of the picture draw only from the two batteries on the left, not from the whole bank. I guess that Mapis will sort all this out
when he installs the new Victron device
MapisM
Well-Known Member
Agreed. a bit of housekeeping is in order.
But all the banks (there's another couple of them not visible in the pic - 8 batteries in total) ARE actually paralleled.
Some of the cables behind them are in fact meant to put each pair in parallel.
You spotted the only exception though, because the grey cables were retrofitted when I installed the hydraulic passerelle, which has its own master switch.
It was the installer of the passerelle who made that connection, I'm not sure why TBH (and at that time I had not time to follow what he did), but since it always worked, I never bothered changing it.
Besides, since each battery pair is paralleled anyway, I suppose the passerelle cables could be attached to any pair without actually drawing current just from that one... Or is there some "prevalence" due to the current flowing from the "nearest" batteries...?
With apologies if it's yet another blonde moment question!
But all the banks (there's another couple of them not visible in the pic - 8 batteries in total) ARE actually paralleled.
Some of the cables behind them are in fact meant to put each pair in parallel.
You spotted the only exception though, because the grey cables were retrofitted when I installed the hydraulic passerelle, which has its own master switch.
It was the installer of the passerelle who made that connection, I'm not sure why TBH (and at that time I had not time to follow what he did), but since it always worked, I never bothered changing it.
Besides, since each battery pair is paralleled anyway, I suppose the passerelle cables could be attached to any pair without actually drawing current just from that one... Or is there some "prevalence" due to the current flowing from the "nearest" batteries...?
With apologies if it's yet another blonde moment question!
Beyondhelp
Well-Known Member
To many assumptions. If its an old charger with no regulation then disconnecting the batteries will be a VERY BAD idea. MapisM you need to measure the voltage across the banks as to get them HOT as you say I'd expect to see around 30v across them. Sulphated batteries have high internal resistance and don't tend to get hot. Batteries with a shorted out cell DO get hot as there is to much voltage for the rest of the cells.
Battery charges are not intended to run without batteries unless stated that they can so be careful there or as suggested replace the batteries with some cheap ones for now, or sort it properly.
D
Deleted User YDKXO
Guest
Jeez, all this to avoid buying some batteries now rather than later! How about an interim solution? How about buying say 1 new battery now instead of 8 which will surely be sufficient to power any nav instrumentation when under way and disconnecting or throwing away the old ones? Then buy the other 7 during the winter
fireball
Well-Known Member
Cos he needs 2 for a 24v solution ... ?
MapisM
Well-Known Member
Thanks for your warning, but I'm not sure if you saw my previous post where I confirmed that after disconnecting the batteries and running on the charger alone, apparently everything was working fine.
And still is, after almost two full days, by now. I mean, the charger never overheated, and it's handling the DC demand of everything I'm interested in.
The only inconvenience, as I previously mentioned (but which I can only notice because I know what I did and I'm keeping an eye on the instruments) is that when the higher absorption equipment (like the passerelle or the fresh water pump) start, it takes a second or two before the charger increases the current supply from say 5 or 10 Amps to 40 or whatever is required.
And in that second, the voltage drops below 20, and the passerelle obviously starts moving very slowly.
But it really takes close to nothing before the charger increases its output, the voltage comes back to normal, and the passerelle moves normally.
Are you suggesting that this could ruin the charger, and/or some other equipment? And if yes, why?
Thanks in advance.
Last edited:
D
Deleted User YDKXO
Guest
Ok missed the fact that he needed 24V and not 12V but even so 2 instead of 8 now is better than all 8 now
Pinnacle
Well-Known Member
I am quite good at installing new battery sets/chargers. Wiring will be much neater than at present!
PM me for a quote!
PM me for a quote!
MapisM
Well-Known Member
I see what you mean M, but the "all this" was not much, really.
I spent more time posting in this thread, rather than disconnecting the cables in each pairs of batteries, which is all the "real work" I did so far.
Sure, I can't fire up all the onboard DC equipment together, and for instance (I didn't try, just guessing) it might be a problem to run both WC and/or shower pumps together when also some other DC stuff is already drawing 20 or 30A, but I'm alone with swmbo onboard ATM, so this won't be a problem for us.
And it's just for a short time anyway....
Hurricane
Well-Known Member
Everyone here seems to be ignoring the safety aspects of having some old knackered batteries on board that should IMHO be dumped - NOW
Duff batteries can cause huge damage and batteries (in general) should be respected.
You say that the old ones are getting hot - I bet they are bulging as well - IMO they need throwing out ASAP
Since buying this boat, I've had my share of battery problems and during the last 6/7 years we've been through 3 sets so I know what you are experiencing.
It seems to me that there are two schools of thought regarding batteries.
You either pay a lot and have really good deep discharge ones or do as I do and by the cheapest truck batteries you can find that fit.
In the past, we damaged a set of batteries - long story - but it wasn't the batteries fault.
So my view is that I can just as easily damage an expensive set as a cheap set.
In fact, my recent set of cheap batteries are working very well.
My service bank is 6x120ah and will run through the night running 3 fridges, some LED lights and some sundry electronics.
At anchor, we run the generator for 2/3 hours in the morning and for about 2/3 hours in the evening to top them up.
In the evening, the A/C goes on with the generator to cool the cabins.
As far as the future is concerned, if I were you I would do one of two things.
1. Replace the existing batteries with new cheap truck ones and accept that you can only use about 50% of the charge (if that)
2. Look at a completely new concept - a set of Lithiums and change the charger - that you say you may well need anyway.
Lithiums are not as expensive as they first sound - you don't need as many as for lead/acid - they can be cycled right down without damage so you get much more than the 50% - and above all, they will last longer.
The only disadvantage that I see is the danger of fire but lead/acid aren't without risk either.
I met up with an old forumite that used to post on this forum who has changed his for Lithium - his 750ah bank was about a quarter of the size of my lead acid one.
I believe he paid about £3k for them.
So, would I change from lead acid or keep to my "buy cheap and often" approach - I DUNNO!!!
Duff batteries can cause huge damage and batteries (in general) should be respected.
You say that the old ones are getting hot - I bet they are bulging as well - IMO they need throwing out ASAP
Since buying this boat, I've had my share of battery problems and during the last 6/7 years we've been through 3 sets so I know what you are experiencing.
It seems to me that there are two schools of thought regarding batteries.
You either pay a lot and have really good deep discharge ones or do as I do and by the cheapest truck batteries you can find that fit.
In the past, we damaged a set of batteries - long story - but it wasn't the batteries fault.
So my view is that I can just as easily damage an expensive set as a cheap set.
In fact, my recent set of cheap batteries are working very well.
My service bank is 6x120ah and will run through the night running 3 fridges, some LED lights and some sundry electronics.
At anchor, we run the generator for 2/3 hours in the morning and for about 2/3 hours in the evening to top them up.
In the evening, the A/C goes on with the generator to cool the cabins.
As far as the future is concerned, if I were you I would do one of two things.
1. Replace the existing batteries with new cheap truck ones and accept that you can only use about 50% of the charge (if that)
2. Look at a completely new concept - a set of Lithiums and change the charger - that you say you may well need anyway.
Lithiums are not as expensive as they first sound - you don't need as many as for lead/acid - they can be cycled right down without damage so you get much more than the 50% - and above all, they will last longer.
The only disadvantage that I see is the danger of fire but lead/acid aren't without risk either.
I met up with an old forumite that used to post on this forum who has changed his for Lithium - his 750ah bank was about a quarter of the size of my lead acid one.
I believe he paid about £3k for them.
So, would I change from lead acid or keep to my "buy cheap and often" approach - I DUNNO!!!
Last edited:
Anders_P42
Well-Known Member
I checked Victron website to see if my charger is continuously rated, it seems they are. So I'm sure you're right that MM's charger will be. I found this interesting technical document that describes continuous output vs temperature / efficiency.
Anders
http://www.victronenergy.com/upload/documents/Output rating operating temperature and efficiency.pdf
Anders_P42
Well-Known Member
Having read the notes on Victron site and though some more, I agree it can probably handle it. A well discharged set of batteries would take a straight 50A for several hours, so 30 seconds powering passerelle shouldn't bother it too much.
