Battery Replacement: AGM 200AH vs 245AH

[Richard Ad]

My original batteries (2005) are bad. I want to replace them with AGM. I'm looking at Deka 8A4DM (200AH) and 8A8DM (245AH). I do not have a dedicated starting battery so these two will be my "house" and "starting" power and will be controled by my 1-2-Both switch. My boat will never leave the Chesapeake (at least with my wife on board) and we usually stay in marinas with shore power. We will only anchor out 4-8 times per year and will use our GPS, Auto Pilot, instruments, refriderator, lights, etc while sailing and during our anchor nights out. Any comments would be appreciated especially regarding AH & physical dimensions. Suggestions welcome.

20.75" L x 8.5" W x 10" H (8A4DM)

20.75" L x 11" W x 10" H (8A8DM)

Thank you.
Richard Ad

[KenKrawford]

Richard,
I'm of the opinion that you can never be too thin, too rich or have too many amp hours. If there isn't a significant cost difference, I'd go with the bigger batteries. I just installed a set of 4 Trojan T-105's. They are 11"L x 7"W x 12"H. I had about 1 1/2" of length to spare and probably 4" of width to spare so you should have plenty of room.
Good luck with your project.

[yodagwb]

I took the 4D and combined them on bank one. Reason being I found 220amp hrs 110 usable puts the batteries down about 50% overnight. Thats a pretty deep discharge, I prefer a 25% discharge, not as hard on the batteries. Combined you have400+ amp hrs total, 200+ usable and 100 amp hr discharge is only 25%. The batteries will thank you. I threw a back up starter battery in the 2 bank position and its never been used. There is my 1 1/2 cents.

[Richard Ad]

Yodagwb: Thank you for your response. I was on the boat today (Annapolis) and your 1 1/2 cents is exactly the system I decided to go with. Everyone I talked to thinks AGM's, for the money are an over kill for sailing on the Chesapeake. Using two 4D's (190 AH x 2 batteries = 380AH) and one $100.00 dedicated starting battery which has better cranking power that will really make my house batteries happy is the system I'm going with. Therefore, two 4D's plus a starting battery for a total of $400.00 that will last 4 years is better than 2 4D AGM's at $360.00 each and one AGM starting battery for $180.00. $400.00 vs $900.00....... I'll check the water level and trickle charge a few time in the winter.

[lyle]

I too replaced the 4D batteries with 6 volt golf carts. 4 Trojan T125's fit nicely in the same space as the 2 - 4D's but give you almost 100 more amp hours (important if you spend a lot of time at anchor). Other than wiring the 6 volts in series then combining them to make one house bank it is a simple installation. The other plus is the 6 volts each weigh a LOT less than a 4D and are much easier to take out and install in that space without giving yourself a hernia. Either way combining the batteries to make one house bank and having a seperate start battery IMO is the way to go.