AGM & Wet Cell Batteries Together?

[Papabrer]

Hi All,

New owner of a Sea Ray 440 (1994). Upon inspection & survey I noted that I have AGM & Wet Cell batteries on board connected to the same electrical and charging systems. I don't know if this was done due to battery shortages (during the pandemic) or if this was a cost decision.

I believe that the two types of batteries charge at different levels. I wanted to ask if this is a problem or if both types can survive in the same system?

 

[carterchapman]

Papa - what a beautiful boat and engines!

Although I don't know your boat, you probably have a port bank of two batteries, and a starboard bank of two batteries. If the batteries in each bank are the same - all AGM or all Wet Cells you should be fine. Older chargers will charge AGMs and Wets the same profile which is fine. Newer chargers will have specific AGM and Wet profiles.

What you don't want is one bank to have an AGM and a Wet. The batteries in each bank should be the same. Like shocks on your car's axles...they should be the same - never replace one without the other....

 

[jmcdboater]

Hi All,

New owner of a Sea Ray 440 (1994). Upon inspection & survey I noted that I have AGM & Wet Cell batteries on board connected to the same electrical and charging systems. I don't know if this was done due to battery shortages (during the pandemic) or if this was a cost decision.

I believe that the two types of batteries charge at different levels. I wanted to ask if this is a problem or if both types can survive in the same system?

Howdy, and Welcome to the cult. That is a fabulous vessel, you’ll enjoy her immensely!

The Admiral and myself lived aboard a 1990 440 MY….(her idea, no less…..ain’t I lucky!). Berthed In Benicia, CA, which is just off the San Francisco Bay. It was absolute Heaven.

 

[ranger58sb]

I believe that the two types of batteries charge at different levels. I wanted to ask if this is a problem or if both types can survive in the same system?

To add to what Carter @carterchapman said, you can also check each battery maker's actual charging voltage recommendations and then ideally pick a preset or programmed charging voltage that will work for each of your banks, too.

This part isn't so much the AGM-versus-flooded construction; rather each battery maker has their chemistry designed for given bulk/absorption and float voltages and you'll be trying to match both at the same time as best you can. If you can't match perfectly, lower is better than higher.

Then whenever you need to replace batteries, you can pick whichever type you've decided you prefer... eventually get both banks to be the same, and charger voltages can be matched even more closely.

-Chris

 

[ttmott]

To add to what Carter @carterchapman said, you can also check each battery maker's actual charging voltage recommendations and then ideally pick a preset or programmed charging voltage that will work for each of your banks, too.

This part isn't so much the AGM-versus-flooded construction; rather each battery maker has their chemistry designed for given bulk/absorption and float voltages and you'll be trying to match both at the same time as best you can. If you can't match perfectly, lower is better than higher.

Then whenever you need to replace batteries, you can pick whichever type you've decided you prefer... eventually get both banks to be the same, and charger voltages can be matched even more closely.

-Chris

Yes - the downside is the charger is configured for one chemistry regardless of how many outputs. The AGM absorption voltage is higher than SLA so if your charger is programmable set to SLA like @ranger58sb alludes.

 

[ranger58sb]

Yes - the downside is the charger is configured for one chemistry regardless of how many outputs. The AGM absorption voltage is higher than SLA so if your charger is programmable set to SLA like @ranger58sb alludes.

Our earlier chargers offered preset profiles like AGM, flooded, or gel... and the manual stated actual voltages for each of those profiles. Once of those chargers combined AGM and flooded into one profile, gel for the other. And then on that one, we could select absorption duration to sort-of match bank capacity.

Newer chargers have offered more flexibility, sometimes including programming whatever exact voltages might be required.

FWIW, Lifeline's float voltage recommendation is lower than many other makers... and I think a too-high float voltage is hard on battery banks...

-Chris

 

[Papabrer]

Thanks very much everyone this and GREAT information. I am truly looking forward to time on the boat and out on the ocean. I have some work to be done at a shipyard prior to taking possession, really hard to wait for the work but every yard around here is crazy busy right now.

Thanks again