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Will AGM batterys be OK in my boat?

M

moondrifter

Regular Contributor
I have 2 regular type ,(flooded cell), 2 year old batterys in my 2000 4.3 190 hp, Wired thru Guest switch.(Off,1, both, 2, position) I use only 1 battery on a outing and alternate each time out and turn the Guest switch off each time when done. The Mando alternator is 70 amp output and checks out perfect. The problem is the self discharge rate of 1-3 amps per day of this type battery, which tend to make a slow start after a month of non use. The self discharge rate of an AGM is .5-1 amp per month. Will my charging system handle these type batterys. I know not to mix types and will replace both if the system will allow. Thanks Moondrifter.
 
Yes, It will work fine. No difference in use.

Just make sure it is the correct CCA for your boat.
 
moondrifter said:
I have 2 regular type ,(flooded cell), 2 year old batterys in my 2000 4.3 190 hp, Wired thru Guest switch.(Off,1, both, 2, position) I use only 1 battery on a outing and alternate each time out and turn the Guest switch off each time when done. The Mando alternator is 70 amp output and checks out perfect. The problem is the self discharge rate of 1-3 amps per day of this type battery, which tend to make a slow start after a month of non use. The self discharge rate of an AGM is .5-1 amp per month. Will my charging system handle these type batterys. I know not to mix types and will replace both if the system will allow. Thanks Moondrifter.
Click to expand...
Conventional Wet Cell batteries are pretty hard to beat for a Marine application, IMO.

I can't speak re; self discharge rate of an AGM @ .5-1 amp per month.
Do you not have an O/B marine battery charger?

I think that perhaps you are looking at your battery banks a little differently than most do.
Typically we'll use a dedicated cranking battery on #1 position of your MBSS (main battery selector switch).... in your case, the Guest switch.
We'll use a Deep Cycle battery (or multiples) on the #2 postion.... (commonly refered to as our House Bank).
We fire up on #1, warm the engine while still on #1 (charge rate will replace the AH used during starting) and we can then switch to #2 while under way.
This keeps #1 in "Reserve" for us.

I always suggest that we avoid using ALL/BOTH during charging.
The engine alternator will perform better if it can sense each bank independantly..... and likewise with an O/B Marine battey charger...... but again, IMO.

If you are concerned with shared engine alternator charging, install a BlueSea ACR unit. An ACR will outperform an "isolator".
If you want an auto-combining feature, BlueSea also offers an ACR that will do this for you.

A few questions;
Do you moor this boat? If so, how is your bilge pump "float switch" powered? The float switch should be powered via an Un-Interruptible power source, and typically from your #2 HB.
If your uninterruptible power source is now from #1, I'd suggest moving this to #2.

Do you have a radio that requires constant power for pre-set memory? If so, move this to #2 also.




.
 
AGMs will work fine, and not a thing wrong with the way you operate (particularly since that's how it's wired). But buy the largest batteries that will fit the space available, I've never heard anyone complain they had too much battery. Be cautious of using BOTH, except for a starting emergency, whatever happened to one can likely happen to the other .... :)
 
Sorry but I used the wrong info. Should be: Self discharge rate for Regular wet cell battery is 1 to 3% AGM Self discharge rate is.5 to 1% per month
 
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