Mis-matched batteries. Questions for lecky wizards.

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peterandjeanette

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My boat was originally fitted with 4 batteries. All 135 amp/hr. One for each engine and two for domestic use. The two domestics have been replaced with 165amp/hr batteries. There is also a built in 240 volt battery charger. (Mastervolt)
Does this mean that when the engine batteries are up to full strength the domestic batteries stop charging and thus do not reach full capacity?
Also, what would be the effect if I replaced the two remaining engine batteries with 165 amp/hr units. Would I over stretch the charger and/or alternators.
Boat is a Fairline Phantom 40 (2004)

This system has been running well for several years, but the engine batteries are now 6 years old and will probably need replacing soon.

All replies gratefully received.
 
The batteries don't have to be matched, when one is charged before another, the second one will still get charge.

Imagine you have three or four water tanks, fitted with ball valves. They all fill as required, whatever their capacity. Same with your batteries.

Can't see any point in replacing the engine batteries with bigger ones. If they only start the engines, batteries big enough for...erm....starting the engines will suffice.

If you put bigger batteries on the boat they won't exactly over stretch the batteries. Forgetting about natural losses, which would be bigger with larger AH batteries, but insignificant in any event, you won't use any more electricity because you have bigger batteries, so the chargers will have no more work to do than they do now. If you increased you power usage, the charger/alternators would have to work harder, but would not "over stretch", in the sense they would not overload and fail. If consumption was too great, they would just not keep up. They would likely have a shorter lifespan though, as they would work harder trying to keep up.
 
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no clear answer is yet possible because we don't know how the Mastervolt delivers charge to the battery banks.

Is is two separate charger out puts, or one, or four ?

How are the batteries connected ? Series or parallel, or mixed ? 6v, or 12v, or 24v batteries ?

In very general terms, intelligent chargers like to work with matched sets of batteries. Matched as in capacity, type, discharge characteristics.

More info pls.
 
sarabande said:
no clear answer is yet possible because we don't know how the Mastervolt delivers charge to the battery banks.

Is is two separate charger out puts, or one, or four ?

How are the batteries connected ? Series or parallel, or mixed ? 6v, or 12v, or 24v batteries ?

In very general terms, intelligent chargers like to work with matched sets of batteries. Matched as in capacity, type, discharge characteristics.

More info pls.
Click to expand...

Default spec is for all batteries to be 12v, in three separate banks. The domestic bank of two batteries are wired in parallel.

The OP's battery arrangement is identical to current Fairline spec.
 
Fairline fit a split charge diode its in the engine room probably a volvo penta one its blue in colour.

The alternators are single output diode then wired to a double diode output system to both domestic and engine batteries, both engine do this so in the event of one engine loss at sea the remaining engine carries on output to all the batteries.
 
You could try to extend their life by 3 years fitting a megapulse unit.
£63 is cheaper than 2 new batteries..

I just bought and fitted one 3 weeks ago to our domestic bank of 3x105Ah. Too soon to tell final results, as it needs to be fitted for min 8 weeks, but I think it's already improving things.

http://www.megapulse.net/ has all the details,

sold in the UK through http://www.pulsingproducts.co.uk/

The UK website is out of date but the contact details are the same. Apparently his computer went bust and now he can't update the website details. He is selling the Mk4 though.

No connection etc, just a recent customer. I figured the cost was worth a punt given the price of the batteries, and having read previous threads on here that spoke highly.
 
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