Very helpful advice re: battery charging

[dor]

Steve you have an evil cynical twist - and I love it!

[Guest]

Oh dear John. You've heard of a can of worms I presume?

 

You'll have the horse drawn narrowboat lobby down on you like a ton of bricks for making a suggestion like that. No matter that you have many years of experience to back it up.

 

On another thread a while a back I suggested such a thing simply because I want the minimum maintenance possible for all the various equipment on my boat, plus AGM batts. charge much quicker because of the higher rate they can stand.

 

Wot? Maintenance free batteries? Are you nuts? Everyone knows that the best batteries are those filthy things that you have keep topping up with distilled water, which if you forget are ruined, are the best! And as for charging those disgusting AGM things, well, you have to regulate it very carefully don't you know. It's not true that you charge at a huge rate. Forget what Mastervolt tell you, wotdotheyknow? They're filthy corrupt capitalists only trying to sell you their stuff.

 

However, I remain totally convinced of the huge benefits of AGM or other mf batteries. Glad to have your opinion in support based on actual experience.

 

regards

Steve

Steve

I was one of the ones who replied saying I wasn't keen on MF . I have never had AGM. Can I tackle this a bit differnetly so as not to offend anyone?

What am I donig wrong?

I bought five MF lead acid to a toal of 600a/h (5x120). They take an age to charge despite a healthy 90amp alternator, all new batteries and a healthy 14.5 volts across each battery when charging. All terminations are new showing miniscule volt drops. The situation is the same using the mains charger (40amp).I have always put the problem down to MF batteries, maybe I'm wrong? The previous boat charged its slightly smaller bank quite quickly despite a 40 amp alternator-the only difference was open lead acid batteries.

[GUMPY]

Steve

I was one of the ones who replied saying I wasn't keen on MF . I have never had AGM. Can I tackle this a bit differnetly so as not to offend anyone?

What am I donig wrong?

I bought five MF lead acid to a toal of 600a/h (5x120). They take an age to charge despite a healthy 90amp alternator, all new batteries and a healthy 14.5 volts across each battery when charging. All terminations are new showing miniscule volt drops. The situation is the same using the mains charger (40amp).I have always put the problem down to MF batteries, maybe I'm wrong? The previous boat charged its slightly smaller bank quite quickly despite a 40 amp alternator-the only difference was open lead acid batteries.

 

You have almost answered your own question!

Its not the batteries but the chargers

Think of it this way

You run the batteries down to half thats 300Ah that needs replacing

Now to replce that with a 40a charger will take how long? In theory 300/40 or 7.5hours and that doesnt include the fact that a 40amp charger doesnt charge at 40amps and that to get a battery back to the same state of charge you always have to put more back in than you took out and that the charge rate tails off as the batteries reach full charge. So it will be nearer 9 hours.

Even with a 90amp alternator you are looking at 3.5hrs.............

 

So soloution is bigger charging system.

 

J

[John Dixon]

sounds like a manual version of an alternator controller which costs a couple of hundred quid. cheap. but expensive if you forget ........

 

Yep! Most certainly true, and Steve is right about opening a can of worms. However, there are ways and means to improve charging. It just depends on what time you are prepared to spend on it. For a simple carefree life then Steve is right. More important than the batteries is your selection of charger which should be matched to battery type. Beware of manufacturers claiming their charger is good for all battery types. There are differences in charging voltages and profiles for wet, AGM etc due to differences in plate construction.

Fast charging can kill batteries by warping the plates so it is important not to exceed a charge rate that can be simply worked out and there-in lies the advantage of manually selecting the charge current to reduce charging time. Also, wet cell equalization will significantly increase battery life and maintain efficiency. Equalization is not recommended for most AGM's.

AGM's will accept all the power that a charging system will produce. This means that if you are using an alternator sized a 25% or less of the battery bank A/hrs, it is very possible to overheat and burn out an air cooled alternator during a long bulk charging phase. I have extra cooling vents cut into my 150amp alternator casing and a simple fan blowing onto it. A temp sensor can also be fitted.

Hope this helps

John

[anhar]

Steve

I was one of the ones who replied saying I wasn't keen on MF . I have never had AGM. Can I tackle this a bit differnetly so as not to offend anyone?

What am I donig wrong?

I bought five MF lead acid to a toal of 600a/h (5x120). They take an age to charge despite a healthy 90amp alternator, all new batteries and a healthy 14.5 volts across each battery when charging. All terminations are new showing miniscule volt drops. The situation is the same using the mains charger (40amp).I have always put the problem down to MF batteries, maybe I'm wrong? The previous boat charged its slightly smaller bank quite quickly despite a 40 amp alternator-the only difference was open lead acid batteries.

Hello catweasel

 

Idleness is correct I'd say.

 

Gel and AGM batteries minimum charge current should be 15 to 20% of capacity. The maximum charge current is 50% for a gel battery and 30 to 40% for an AGM battery.

 

So in your case with a total battery capacity of 600Ah, which I presume are gels, you should be charging at an absolute minimum of 90amps and a maximum of 300amps. Consequently this appears to be your problem. You are simply applying the absolute minimum charge current for gels which means that it would take some time.

 

Note that these figures apply assuming there is no drain whilst charging. But on a lot of boats there will be, a fridge for example etc. If there is, you would have to increase the minimum of 90amps to cover that. For example if you have a 10amp load whilst charging, you would need to apply an absolute minimum of 100amps in order ever to be able to charge up in a reasonable time. Any less than that and it will take far too long.

 

regards

Steve

[anhar]

Steve you have an evil cynical twist - and I love it!

Hello dor

 

Yeah, you are probably right. You should see my bad side.

 

Steve

[Cafnod]

loj[j[u9

Edited February 14, 2006 by Cafnod

[JohnT]

This might seem very elementary to many of you long-time-liveaboards out there, but for those of us (like me) who have only been living aboard a short time so far, this could be very useful knowledge.

We moved aboard our boat 6 months ago now (loving every minute!), and we were advised to run our engine for around 2 hrs per night (winter) to keep out 4x100ah batteries charged up. We did this and found it to be fine. A bit heavy on the diesel though (£25 - £30 a month). We always ran it at tickover (Beta 43 Greenline - around 850rpm) and did alternate nights in gear and in neutral.

I was recently advised that this may not be the best rpm for charging our batteries. So I phoned Beta Marine (very helpful) and asked them what we should be doing. They suggested around 1400 rpm and running in neutral (only need to run in gear every couple of weeks or so to clear out any carbon deposits). This I duly did and have now found that we only have to run the engine for around 40 minutes each night to keep our batteries topped up (running lights, pumps, laptop, stereo, 1800w inverter). Genius

 

Well said Tom & Sophie good tip and practical too, sod the Sceptics, know alls, who only seem to want to put people down and do their own thing on this forum.

[Smelly]

viva john T.

 

for all the know alls, and some of them do know their stuff, they can't anticipate the exact circumsatnces of your boat. If it works for you use it!