AGM Batteries and Charger

Last week I decided it was time to change the batteries, house and starting banks. There were a pair of group 27 for each use and last year I found out they were replaced in 2012. It turns out that the most accessible starting bank were replaced in 2012. The house bank were replaced in 2011. I replaced my 110v fridge that was running on an inverter and draining down both banks every weekend even when I shut it down for long periods of time. So I figured it was time. Off I went to the East Penn manufacturing warehouse and purchased 4-Deka Group 31 AGM batteries (the Intimidator!) and 2 sets of correct cables to replace the anemic cables that the PO installed with the Group 27 batteries. Here's my question: I have a rather old on board Sea Ranger battery charger that will charge the new batteries and also a standard lead acid battery for my generator (which I replaced in 2015). Do I need a special charger for the AGM batteries? Should I have just stuck to standard batteries? I would hate to have to have to replace the charger.

Here is an article that will help you answer your own question.
It is written by Rod Collins, he is one of the best.
Bruce

https://marinehowto.com/installing-a-marine-battery-charger/

Thanks Bruce. I guess I didn't do my homework before I purchased the AGM's.....

slowandsteady said:

Here's my question: I have a rather old on board Sea Ranger battery charger that will charge the new batteries and also a standard lead acid battery for my generator (which I replaced in 2015). Do I need a special charger for the AGM batteries? Should I have just stuck to standard batteries? I would hate to have to have to replace the charger.

Click to expand...

Does it have any charge profile settings -- perhaps "lead" and "gel" or some such? Do you know what bulk/absorption and float voltages the charger provides? For each profile setting, if it has more than one?

Do you know what bulk/absorption and float voltages the battery makers recommend? For both your genset flooded battery and the new AGMs?

Or...

FWIW, your charger manual might also include commentary about how each of the banks should be mostly similar in capacity, so your genset battery may be risking overcharge already anyway. Does your genset have it's own alternator? If so, would it be sufficient to just let your genset motor charge it's own battery, so you could remove it from the charger?

Is this a diesel boat, or gas? If the former, and if the genset engine will charge it's own battery, could be a simple set of jumper cables could be an additional belt-and-suspenders thing. Would want to risk sparks in a gas boat, though...

-Chris

Chris,
Existing charger is pretty old. Settings consist of "on" and "off"
Recommended bulk/absorption and float voltages are labeled on the new batteries. I'll make note of them when I go to the boat later on.
The gen set is a 3.5KW and has no alternator.
The boat has a single Perkins T354.6M

Sterling ProCharge Ultra*and ProMariner Pronautic P are nicely future proof if your future banks have different requirements from your current one.

Get at least 20% of your AH capacity in charging amps, 40% would be better to minimize charge times and possible future expansion.

slowandsteady said:

Chris,
Existing charger is pretty old. Settings consist of "on" and "off"
Recommended bulk/absorption and float voltages are labeled on the new batteries. I'll make note of them when I go to the boat later on.
The gen set is a 3.5KW and has no alternator.
The boat has a single Perkins T354.6M

Click to expand...

The question really is whether your charger does bulk and absorption charging at all. Depending on that, you may want to consider replacing it with a modern one that does.

I'm wondering, if I purchase a new charger, if I will be able to program 2 different types of batteries. Do all the batteries on the charger have to be the same type?

slowandsteady said:

Chris,
Existing charger is pretty old. Settings consist of "on" and "off"
Recommended bulk/absorption and float voltages are labeled on the new batteries. I'll make note of them when I go to the boat later on.
The gen set is a 3.5KW and has no alternator.
The boat has a single Perkins T354.6M

Click to expand...

Hmmm... so much for my earlier ideas.

dhays said:

The question really is whether your charger does bulk and absorption charging at all. Depending on that, you may want to consider replacing it with a modern one that does.

Click to expand...

But this is a really good point, and leads to another. Even if your current charger provides separate bulk/absorption and float voltages, they may not be appropriate voltages for your new batteries... and they may not have been appropriate for your earlier batteries, either. Might be OK, or might not be great. If you can pin down the charger voltages, you might be better able to decide whether you should do something about it, or not.

slowandsteady said:

I'm wondering, if I purchase a new charger, if I will be able to program 2 different types of batteries. Do all the batteries on the charger have to be the same type?

Click to expand...

I've not seen any that offer a multiple-profiles-at-once option like that, at least when I was shopping. OTOH, the available profiles or other voltage selections can usually offer a decent compromise between various brands of AGMs and FLAs. Can't usually add any gel batteries into the mix, though, but that's not hard to avoid.

-Chris

There are very expensive multi-bank chargers that allow different profiles per output.

A cheaper way is Sterling's "Battery Chemistry Module"

https://cdn.shopify.com/s/files/1/0658/7343/files/full_cec_instruction_1.pdf

Or just use a DCDC battery to battery charger, more versatile, can use in conjunction with different charge sources like Alts.

View attachment 1
Here's my high tech charger.....
And here's my new AGM battery

Does it have a temp sensor for safety/compensation?

No it doesn't.
I just purchased a Sterling Pro Charge Ultra 40 amp charger on line.
Kind of high tech for my 34 year old boat but if I'm going to get the most out of the batteries I just purchased I may as well charge them correctly.
Does it make sense to keep the old one in place for the lead acid batteries and use the new charger for the AGM's? I can always phase in the battery chemistry module at a later date. I think I've spent enough money this week on batteries and charging system, not to mention the furniture I just ordered for the boat!
Thanks everyone for pointing me in the right direction.

Sure use the old one for FLA (AGM is also lead acid, just sealed).

Maybe verify what it's doing a cycle or two just to make sure.