New AGMs fitted

P

plumbob

Well-Known Member
Joined
18 Oct 2009
Messages
1,669
Location
Bucks
Visit site
My boat has always had the same wiring configuration but as we needed some work doing I thought it was a good time to change all 4 batteries as I know they are at Ieast 10 years old. Decided to go with AGMs each rated at 120ah ( the previous were LA at 125ah) Victron 40ah charger reconfigured for AGM.
Should I leave the charger on for a few days, to get them fully charged?
If they are fully charged will the voltmeter still show a charge rate of 14v?
Thanks for your help.
 
I'd leave the charger on permanently. If a modern Victron charger it will go to float then down to Storage Mode at 13.2v.

I had a Victron (Easyplus) charger permanently on for sixteen years with our previous boat. So far on this boat our Victron Multi has been on for five years with no problems. AGM batteries. Excepting when we’re away from shore power of course.
 
Last edited:
GEM43 said:
I'd leave the charger on permanently. If a modern Victron charger it will go to float then down to Storage Mode at 13.2v.
Click to expand...
I agree that it is worth putting charger on for a day or so to fully charge.
But personally I do not leave the charger on permanently, but switch off and disconnect shorepower when leaving the boat.
 
plumbob said:
My boat has always had the same wiring configuration but as we needed some work doing I thought it was a good time to change all 4 batteries as I know they are at Ieast 10 years old. Decided to go with AGMs each rated at 120ah ( the previous were LA at 125ah) Victron 40ah charger reconfigured for AGM.
Should I leave the charger on for a few days, to get them fully charged?
If they are fully charged will the voltmeter still show a charge rate of 14v?
Thanks for your help.
Click to expand...
You don't paint a full picture. Is the shore power charger the only source of charging?

In my experience of AGMs your volt meter will show anything between 12.56>12.70 volts when your batteries are 'at rest' for 24 hours.
Note: I run a Victron shunt, battery sensor, MMPT and shore power and there is about a 0.50 amp power draw at all times.

Personally, I pull the fuse between the shore power and the battery (like throwing a switch) when not using the shore power.
 
Sandy said:
You don't paint a full picture. Is the shore power charger the only source of charging?

In my experience of AGMs your volt meter will show anything between 12.56>12.70 volts when your batteries are 'at rest' for 24 hours.
Note: I run a Victron shunt, battery sensor, MMPT and shore power and there is about a 0.50 amp power draw at all times.

Personally, I pull the fuse between the shore power and the battery (like throwing a switch) when not using the shore power.
Click to expand...
We have shore power, obviously engine and a 170 watt solar panel with a double battery bank controller. Just thinking might be better left on charge for a few days. Why not?? All 4 batteries showed 14.68v with the engine running. Bow thruster held at 13.08 Starter held at 13.18 and house x 2 held at 13.62.
Charger is currently off.
Thanks
 
plumbob said:
Just thinking might be better left on charge for a few days. Why not??
Click to expand...
You won't do any harm leaving them charging, but also it won't make any difference after about 24 hours.

A modern Victron charger will go onto float once they're fully charged, maybe even switch itself off an check on the batteries daily, so I don't see any harm in leaving it powered on, But you also have the solar, so that will be doing the same thing.

If you fit a SmartShunt you will see a high amount of current rushing into discharged batteries when you first turn the charger on - maybe 40A or something. Then after only a few minutes the inflowing current falls and after an hour the current falls and you'll probably be only at 5A or so (depends on the size of the battery). After 24 hours, if the boat is on shore power and you're not discharging the batteries, the charger will be putting out only about 1A - it's not really true to say that the battery is absorbing or accepting that, or getting any benefit from it at all. Lead acid batteries (including AGM) have internal resistance, so I would think that the 1A is mostly just being dissipated as heat.

And, as I already said, if you have solar then that will be giving the batteries this flat charge anyway.
 
Some of the Victron chargers, certainly the Multiplus, can be configured, when connected to shorepower, to use solar generated energy in preference to shorepower. Arguably this is the best of both worlds as a prolonged period of poor solar yield is not detrimental as the charger switches to use grid power.
 
plumbob said:
We have shore power, obviously engine and a 170 watt solar panel with a double battery bank controller. Just thinking might be better left on charge for a few days. Why not?? All 4 batteries showed 14.68v with the engine running. Bow thruster held at 13.08 Starter held at 13.18 and house x 2 held at 13.62.
Charger is currently off.
Thanks
Click to expand...
Leave the mains charger off, the solar will look after your batteries, assuming a decent, correctly configured controller.
 
You must log in or register to reply here.

Share this page

Top