lw395
Well-Known Member
A voltmeter for about £4 is a good start!
Charging batteries in parallel
- Thread starter MM5AHO
- Start date
A voltmeter for about £4 is a good start!
[70521]
Well-Known Member
GHA
Well-Known Member
MM5AHO
Well-Known Member
Many have a setup that has a (typically) 55Ah engine battery and one or more separate "house batteries" which might be >100 Ah. they then have a switch to select either or both.
We have two 55 Ah batteries, neither dedicated to any use. Two battery switches allow each to be connected to the system. Switching both on means 2 in parallel.
Normal practice is both on when engine running = charged batteries. Engine off = only one switched on, and alternate this every day to even out use.
Only variation is that VHF is wired direct to one of the two batteries so that it cannot be isolated from power.
Panel has an ammeter to show draw load, and switchable voltmeter to read each battery V independently. (direct wired to each)
In extended night sailing last year noticed that one 55 Ah was struggling, so fitted a wind generator. This is connected through a controller to one only battery. That has now become the battery to use for night sailing.
The boat is 41 years old. System has lasted that long, though many components, including panel and batteries are all changed out, but circuit principles remain same.
So batteries are mostly charged in parallel by engine. One gets a bit more by wind (though only a small generator).
We have two 55 Ah batteries, neither dedicated to any use. Two battery switches allow each to be connected to the system. Switching both on means 2 in parallel.
Normal practice is both on when engine running = charged batteries. Engine off = only one switched on, and alternate this every day to even out use.
Only variation is that VHF is wired direct to one of the two batteries so that it cannot be isolated from power.
Panel has an ammeter to show draw load, and switchable voltmeter to read each battery V independently. (direct wired to each)
In extended night sailing last year noticed that one 55 Ah was struggling, so fitted a wind generator. This is connected through a controller to one only battery. That has now become the battery to use for night sailing.
The boat is 41 years old. System has lasted that long, though many components, including panel and batteries are all changed out, but circuit principles remain same.
So batteries are mostly charged in parallel by engine. One gets a bit more by wind (though only a small generator).
halcyon
Well-Known Member
Assuming you are at tickover, then you have little alternator output and low battery charge voltage, so poor or actually no charge, in which case disconnecting the service bank will see a small increase in engine battery charge volts. Either connected or disconnected without the alternator running at good rpm, you will see low charge volts.
Fit Voltmeter and ammeter showing net amps to / from service bank, charging till you see low current and high regulation voltage means you are at max nominal battery capacity, not 100% battery charge, to reach this level is a different world.
Brian
Brian
MM5AHO
Well-Known Member
This depends on pulley sizes and ratio of the two one with respect to the other (ie alternator rpm at engine idle).
In my case 14V at engine idle enables battery charge from an engine idling with no load.
I have discovered one disadvantage of idling - exhaust elbow blockage!
lw395
Well-Known Member
I'd agree with that.
Our standard Yanmar alternator set up would usually reach regulated volts within a few minutes at tickover.
But if the batteries start quite low, and the fridge is on it's not so good.
Diesel sailing boat engines are not exactly the best way to charge yacht batteries.....
William_H
Well-Known Member
This is correct. The old dynamo (generator) of old cars could not charge at idle engine speed because the rotor (armature) was complex of wire windings and could not stand high centrepital forces of high speed rotation at high engine speeds. So had to be geared to manageable generator RPM at max engine speed = low gen speed at idle. Modern alternators have just a filed coil wound in effect along the shaft with iron pole pieces going out to the circumference. Properly ballanced it can handle really high rotation speed. (at max engine revs) so can be geared for good speed when engine is at idle.
hence usually useful charge at idle. But not full charge of course. Use an amp meter to check.
I don't have a diesel inboard engine so rely on solar. Plenty of sun here. However I reckon that diesel engine charging is the best for most sailors.
Certainly wind and solar are horrible things to have on deck. Yes useful if you go cruising for many nights but for most not really necessary. Unless you leave the boat unattended for long periods when solar is good. good luck olewill
