Battery charger question

[Dulcesuenos]

Our boat has 5 AGM 90 ah batteries, (we installed) the boat came with 2x130 kyocera panels, an automatic 30 amp multi stage charger (yes its set to agm) the prior owner also had installed a large Iota 75 amp boost charger/ power supply . My question, is this really benefitial?? Never had a boat someone did this too. His answer was its great if the batteries are low and you need to start in a hurry?? Well if we were in a marina and hooked to shorepower great but if that were the case its pretty east to maintain the batteries with the regular charger. Id rather remove the boost charger and use the heavy wires there to tie in a nice inverter.
Unless someone has a reason not to?? This unit is a charger but also a 75 amp and 1000watt power supply it charges at 13.4. Is it better to leave this on at a marina when running all our 12V items ( lights wp etc

[sailinglegend]

30 amps shorepower is nowhere near enough to charge 450Ah of AGMs - that is why the prior owner added the extra charging. AGMs should be charged at least at 20% of their capacity. With only 30 Amps charging you won't be taking advantage of their faster charging rates, and if you go into a marina only occasionally then you will not get fully charged overnight. If you have an AC genny you need the largest shorepower charger you can get.

[Dulcesuenos]

Ok than does that make the other charger not needed? We have a 2kw genny not sure of that will run the iota

[Andina Marie]

HOWEVER if you want to make use of the heavy cables for an inverter and are reluctant to give up the extra charger, for very little additional cost you can get an inverter with the charger built in, usually a fairly hefty charger so you would have the best of both worlds.

[donradcliffe]

Originally Posted by sailinglegend

AGMs should be charged at least at 20% of their capacity.

Wrong.

[Dulcesuenos]

Ok spoke to IOTA, GREAT guys and wealth of info and help. The unit I have has the IQ4 which has automatic programming for all battery types, It will charge at 14.2 and automaticaly decrease and float when needed but always have the 75amp 12v power supply available so you are drawing 12v amps from the unit not the battery. I am guessing the prior owner used the smaller charger when they were using the generator as the 2k gen wont run the larger charger.

[Redline452]

Originally Posted by sailinglegend

30 amps shorepower is nowhere near enough to charge 450Ah of AGMs.

uh... 30A at 120VAC could provide over 200A at 12VDC (allowing roughly for RMS conversion and charger efficiency) - more than enough to charge 450AH of any pretty much anything. There's a 10:1 voltage difference to consider - 30A at 120V is 3600 Watts.

(I guess this is how people get confused about solar panel ratings and MTTP controllers, but I digress).

[sailinglegend]

Originally Posted by donradcliffe

Wrong.

Maybe I should have said Lifeline AGMs should be charged at least at 20% of their capacity - straight from my manual. Odyssey say 40%.

The point is if you are NOT charging AGMs at greater than 20% of their capacity then you are not taking full advantage of AGMs extra cost.

If you can't charge your AGMs at a higher rate than 20% then you probably have a Trojan or a dual purpose AGM, not a proper deep cycle.

[sailinglegend]

Originally Posted by Redline452

uh... 30A at 120VAC could provide over 200A at 12VDC.....

The OP was talking about a 30 DC charger. Maybe I should have said:

"A 30 amps shorepower charger is nowhere near enough......". Life is too short!

[barnakiel]

30A shore power charger is, IMHO, always a 30A of charge capacity. We are talking of 30 A charged into a 12 or respectively 24 Volt bank.

Now we were using:
25A on 240 Ah bank,
25A on 90 Ah bank,
100A on 670 Ah bank,
and these all worked as advertised.

Remember most chargers today will have some sort of time/amperage limiter and so if charging very depleted banks in shortest possible time is an issue (say an overnight stay at the dock only) then do get a BIG charger.

Balance all things prior to any budgetary commitments - perhaps the way you use energy and your solar panels balance evenly or nearly so. Then a 30A shore power charger is absolutely adequate.

b.