New battery charger..how many amps?

[Luther]

My old Sentry battery charger seems to have died.
I'm looking at a ProMariner 63120 as a replacement.
I have 2x225 ah AGM batteries and a lead acid starter battery.

Is a 20amp model sufficient? The current Sentry is 40amp.

Note: My AGM's are 6 years old and I'm planning to swap them out for Golfcart batteries soon.

Need to order the charger asap so any advice greatly appreciated.

[Scot McPherson]

don't get a battery charger if you are going to replace the batteries really soon, just replace the batteries and THEN buy the charger to match.


The prosport is a great battery charger however. I love mine. The 20amp should be fine for your 220ah. Make sure if you DO buy the battery charger that you buy the charger for the number of batteries you have. If you have a 2 battery bank, then get a 2 battery charger...This is especially true of the prosports. a 3 bank charger will NOT operate with two batteries. It will just go into fault mode.

[Luther]

Cheers Scott,
So it's the amp hours of the individual batterys that matters and not the total amp hours of all batteries?

[Paul L]

Originally Posted by Luther

Cheers Scott,
So it's the amp hours of the individual batterys that matters and not the total amp hours of all batteries?

No, it is total amp-hours at 12v. Are you going to charge from shore power overnight or from a gender?

[john61ct]

FLA GCs will likely accept lower current than good AGMs, so 10% your bank AH while on the low end should be fine.

But super-quality FLA like Rolls will take faster, I'd stick to at least 15-20%. Can't go "too high", it's just money 8-)

Note the ProNautic P series have full charging customizability, in case your bank after next has different requirements.

[john61ct]

Originally Posted by Luther

Cheers Scott,
So it's the amp hours of the individual batterys that matters and not the total amp hours of all batteries?

No, a bank of fulltime-connected batteries should be treated as one big battery, which is actually exactly what it is electrically.

Quality chargers with multiple bank outputs usually automatically deliver proportional output amps as needed, and/or allow multiple outputs to be paralleled together.

A single output is fine be fine if using some sort of VSR / combiner to charge multiple banks at the same time.

[john61ct]

Sorry, I see that model is actually ProNautic P.

[Scot McPherson]

No I didn't say the individual batteries determine your AMP requirements. I said the ProSport manages each battery separately no matter how you have the batteries wired up. This lets the smart technology analyze the condition of each battery individually and charge it/maintain it accordingly.


I have 2x 160 Ah batteries group 4D case, and the ProSport is fine for that. I got it direct from ProMariner that the ProSport is good for about 2x 200 Ah batteries. I bought the model I have based on their direct recommendation for my setup.


The model of charger that is recommended by ProMariner for 2x 225 Ah (450 Ah Total) is the ProNautica 1250 which is designed for three banks anyway, so throw your starter battery on a set of leads as well. It's ok, the unit is smart and handles each battery separately.

[john61ct]

NBD, but may be more clear if you refer to what may be multiple cells/batteries always connected together in normal use as a bank.

When distinguishing between the different functions like starter, house, backup, reserve etc, using such terms with "battery" is also clear.

Otherwise IMO it does sound like you mean the individual batteries within a bank.

[LLizzard]

I agree with John61, for that size bank, a 40 amp charger is usually the min. those 20 amp chargers are really designed for the guys running 2 group 27 batteries in skiffs. A 450 amp bank usually has a 40 or 50 amp charger. t
Then again, if you are always plugged into shore power, does it really matter? You'll eventually get to fully charged.

[Maine Sail]

Originally Posted by Luther

My old Sentry battery charger seems to have died.
I'm looking at a ProMariner 63120 as a replacement.
I have 2x225 ah AGM batteries and a lead acid starter battery.

Is a 20amp model sufficient? The current Sentry is 40amp.

Note: My AGM's are 6 years old and I'm planning to swap them out for Golfcart batteries soon.

Need to order the charger asap so any advice greatly appreciated.

The 20A ProNautic P could work but it will be working harder and longer than it really should. The 30A and smaller units also use small terminal strips on the outputs that are tough to fit the correct gauge lug into, when taking voltage drop into account. The 30A and larger units have studs and nuts. ProMariner and Sterling Power both (The Sterling ProCharge Ultra is the same charger) recommend sizing the charger at 10%, or larger, than bank Ah capacity.

Originally Posted by Scot McPherson

I have 2x 160 Ah batteries group 4D case, and the ProSport is fine for that. I got it direct from ProMariner that the ProSport is good for about 2x 200 Ah batteries. I bought the model I have based on their direct recommendation for my setup.

I am very surprised ProMariner suggested a ProSport charger for 4D's but their tech support sometimes lacks, so I'm not totally surprised.

The ProSports are one of the most frequently fried chargers I see out there other than Xantrex. The ProSports are small waterproof chargers intended for small bass boat batteries. They were not intended or designed for large house banks.

In the manual ProMariner is quite specific that these chargers are designed for G-24, 27, 30/31 batteries with one battery per output. I know this because I have had to open the manual and point this out to customers who bought them and were then angry at ProMariner for building a "crappy charger".. I have to explain that they do what they were intended to do and that is charge smallish banks on bass boats or center consoles not 450Ah's of batteries.

If remember the last ProSport "cooked" discussion I had correctly there is also a black box warning specifically stating that if you have 4D or 8D batteries you need to jump to the ProNautic line of non-waterproof chargers.

Originally Posted by Scot McPherson

The model of charger that is recommended by ProMariner for 2x 225 Ah (450 Ah Total) is the ProNautica 1250 which is designed for three banks anyway, so throw your starter battery on a set of leads as well. It's ok, the unit is smart and handles each battery separately.

The ProNautic P is a good charger and a much better choice for charging a large house bank. Like most any "multi-output" charger the ProNautic P has one power supply and one voltage regulation circuit and all connected banks get the same charge profile. The single power supply and regulation circuit simply feeds three outputs, usually through either FET's or diodes, that prevent back feeding between batteries when the charger is off.

Today many boaters have charge management devices installed such as ACR's, combiners, voltage sensing latching relays, Echo Chargers, Duo Chargers or DC to DC battery to battery chargers/B2B's. The reason CMD's are so prevalent is because they can work with any charging source including battery chargers, solar, wind, alternators, hydro generators or fuel cells to charge multiple banks and do so automatically.

In an ever growing number of installations a multi-output charger is being installed using just a single output that is feeding direct to the house bank or its bus.. When the house bank is getting charged, from any source, the charge management device take care of the start or windlass/thruster bank.

[john61ct]

Oh, I misread, thought 225 was the total AH.

If 450 then IMO < .1C at 45A is the minimum, really 40A OK I guess, as I said that may be right around the mfg recommended rate for lower cost FLA.

I think if desulphation conditioning is needed 5% C may not be strong enough?

Edit: whoops, saw MS post, so, what he said 8-)

[smac999]

40-60a

[ranger58sb]

Originally Posted by Scot McPherson

The model of charger that is recommended by ProMariner for 2x 225 Ah (450 Ah Total) is the ProNautica 1250 which is designed for three banks anyway, so throw your starter battery on a set of leads as well. It's ok, the unit is smart and handles each battery separately.

Well... maybe with some external management.

FWIW, I have the older model 40-amp ProMariner 3-bank charger, and the manual suggests all three banks should be roughly similar in capacity. I suspect there are limits to how smart the unit is, and how well it handles each bank separately.

My set-up was two 300-Ah main banks... plus a 68-Ah bank (single battery) for the genset starter. Latter showed signs of excessive charging, I suspect because it was so much smaller than the other two banks.

Took it off the charger, jumped the now-unused terminal on the charger to one of the other terminals (per the manual), all good.

Their newer ProNautic is probably better, but it wouldn't surprise me if it's still not a complete rocket scientist. Might be useful (if OP pursues that option) to review that manual prior to purchase and see if they still suggest that multiple banks be roughly the same size.

-Chris

[a64pilot]

One thing to remember when sizing a charger is your house load, for instance if you have a load of 10 amps, then you only have 10 left for charging, if you have a 20 amp charger, and your running it at max capacity, which may mean excessive heat and a shorter life?
Also I believe that most battery chemistries benefit from high charge rates, your AGM's will, and I believe your flooded batteries will too, I believe a high charge rate will get the electrolyte moving via a convection current, a low charge rate will I think allow it to stratify, separate the acid concentration somewhat, in a flooded battery.

I will get some argument, but bottom line you can't have too big a charger, only too small.
Way, way too big may be a waste of money though