HMV Barn Project

[Nowhere-Man]

Here is an interesting argument on the topic of split charge relays (which I plan on fitting). For some time, there has been some controversy about surges, discussed on marine forums. The argument runs as follows: An inverter/charger is connected to a battery bank. It has a total load rating of 3 Kilowatts. Someone plugs in a high load or a high load is plugged in to inverter as the engine is being started. Let's say, 2500 watts. Starter battery is charged but house batteries are flat. 

12 volts/3500 gives a current of roughly 200 amps, plus on coupling via the relay the batteries try to equalise. Result = current surge, melted battery terminals and smoke from dashboard. Is it true? Here is some information on surges.

http://www.smartgauge.co.uk/nosurge2.html

[Terry]

Car batteries? Why on earth would you use car batteries?

I'm afraid you jumped the gun a bit here by taking me so literally. By "car batteries" I simply meant "lead acid batteries".

Basically anyone who owns a yacht or narrow boat is going to know the difference between leisure and starter batteries. At least I hope they do ...

With respect, this forum caters for folk with a wide range of technical knowledge and, most definitely, very few own a yacht or narrow boat. Many may have a requirement for a leisure battery though and may have already tried a car battery unsuccessfully without knowing the reason why it has been a failure.

To complain that my correction of your blatantly incorrect and misleading statement is 'jumping the gun a bit' is, to my mind, very disrespectful to other members. Anybody can make a slip - I'm sure we all do it from time to time - but to suggest it should remain uncorrected in perpetuity is not in the spirit of this forum.

Many posts here clarify misunderstandings, correct errors and omissions, fill gaps in understanding and generally seek to educate wherever possible - long may it continue to do so.

[Joe]

Hear, hear.

[pwdrive]

Pass.

Lawrence.

[Crackle]

I put a plug on the inverter as it's shown in the booklet and just plugged it in. So, the inverter is secondary and used as an appliance. The battery is reluctant to charge. It may or may not have sulphated but sometimes it's possible to get a charge. Time will tell. I have to step over it as it's on the floor at the moment charging.

Please clarify the above:
It sounds like you fitted a 13 amp plug to the 240v output of the inverter, was this with the view to plugging it into the ships 240v mains circuit.
Highly dangerous, anyone reading this should NEVER attempt to do this.

One thing I discovered was I think it's a ferro resonant charger because the booklet shows a max current of 10 amps at charge yet lower voltage. When the voltage goes up to 13, current drops. There was a debate with a friend about cable size but I ended up fitting a very high amps cable, mainly to accommodate any surge or high load across the inverter.

Unlikely, for leisure use in the 90's, it is more likely to be a constant voltage charger, or switched mode 3 stage charger. (bulk charge equalise, float)
 

This is a modified sine wave unit. Not sure how my radio would work on it.

Modified sine wave is more or less square wave. It may work, but in my experience with valve radios on a modified sine wave inverter there is so much "noise and interference" that the AGC of the radio will be turned full on and it will have difficulty picking up any stations on MW or LW.

Mike

[Nowhere-Man]

I put a plug on the inverter as it's shown in the booklet and just plugged it in. So, the inverter is secondary and used as an appliance. The battery is reluctant to charge. It may or may not have sulphated but sometimes it's possible to get a charge. Time will tell. I have to step over it as it's on the floor at the moment charging.

Please clarify the above:
It sounds like you fitted a 13 amp plug to the 240v output of the inverter, was this with the view to plugging it into the ships 240v mains circuit.
Highly dangerous, anyone reading this should NEVER attempt to do this.

One thing I discovered was I think it's a ferro resonant charger because the booklet shows a max current of 10 amps at charge yet lower voltage. When the voltage goes up to 13, current drops. There was a debate with a friend about cable size but I ended up fitting a very high amps cable, mainly to accommodate any surge or high load across the inverter.

Unlikely, for leisure use in the 90's, it is more likely to be a constant voltage charger, or switched mode 3 stage charger. (bulk charge equalise, float)
 

This is a modified sine wave unit. Not sure how my radio would work on it.

Modified sine wave is more or less square wave. It may work, but in my experience with valve radios on a modified sine wave inverter there is so much "noise and interference" that the AGC of the radio will be turned full on and it will have difficulty picking up any stations on MW or LW.

Mike

It must be the case I use vague terminology or express myself in ways members are having difficulty understanding. This may well be the case because what I want to communicate is being read in a totally different way.

O.K., the first point is I have never wired this boat up. The whole inverter system was in fact wired in by a qualified AC electrician before I owned it. I haven't done anything to the wiring whatsoever except remove an inverter that had a blown a 15 Amp fuse. I had to remove the inverter  it was boxed in to get at the fuse because if not the system would have been non-operational.

I have not fitted any 13 amp plug to the inverter output. I'm not sure how I might have given that impression. What I did say was the instruction leaflet shows examples of the inverter being used with power connected to a mains socket. That is the supply not the output.

The batteries are now being charged on my boat via the inverter with 100 amp wire. They are only holding about 12.3 volts but are old batteries so I may need to get some better batteries.

I'm afraid at this stage I think it's best I drop out of this site with no hard feelings on my part.   As I said, I think what happens is people are struggling to understand my explanations which I admit is probably due to me being a bit vague at times but my workload is very high and sometimes I get in a rush. As I said, I tend to simply call lead acid batteries car batteries as a colloquial term and didn'tthink I'd need to also explain the difference between CCA batteries and Amp Hour batteries.

I was working on the radio today and expect to have it up and running maybe in 2 months depending upon how things go.

[pwdrive]

I get the impression you were given a bit of a hard time on UKVRR by some of it's members, no need to quit this forum, I'm sure most of us are onside with you in your endeavors, my previous post (#44) stated that I will pass, pass that is on some of the comments directed toward you, some technically supreme types are sometimes a bit keen to in effect ridicule, rather than phrase stuff from a teaching and understanding point of view...I've now said my bit on this and have nothing further to add except to say that anyone can make of it what they will...It would be sad if nowhereman left the forum...

Lawrence.

[Alan Douglas]

No need to leave. I'm a bit puzzled myself, reading the explanations, and perhaps others are too, but we can sort that out. "Inverter" to me means 12 VDC in, 120VAC out. Is that not the case?

[Mark Hennessy]

I also agree that there is no need to leave.

But perhaps it's best to "park" the subject of boat electrics for the time being. Anything involving electrical installations and electrical safety is bound to be contentious to some extent. Whatever was said, please remember that fundamentally, it came from knowledgeable people who have your safety at the centre of their concerns.

Engineers are - by their very nature - very precise in their thinking. That's just how we are. So we can't help but pick out minor errors for clarification - especially when electrical safety might be a factor. To others, engineers can appear to be pedantic and punctilious - not realising that engineers just want to make things better! It's a problem in big companies when engineers have to communicate with other departments.

I think it's best if we close this thread for the time being - hopefully that'll draw a line under the electrical safety issues (marine installations are stretching the bounds of this forum anyway). Let me know (via a PM) if you'd like it re-opened, although once you've made some progress with the HMV, a new thread might be more appropriate. We can copy across posts or tidy it all up in whatever way makes most sense to you.

All the best,

Mark