Notices

22 Sisu Electrical

Old 03-05-2013, 07:41 AM
  #1  
Junior Member
Thread Starter
 
Join Date: Nov 2012
Location: Bermuda
Posts: 12
Default 22 Sisu Electrical

Hey guys, i had a thread a little while ago about a single diesel boat with three batteries. I still have the same boat, and the time has now come to get down to business as boating season is around the corner.

Here is what i am working with, i have a lead-acid starting battery and a gel house battery. i was originally looking at having three batteries, but am now going with 2. I have a Blue Sea add-a-battery ACR charging relay on order and will use to isolate the batteries while only having one battery switch on the boat.

My concerns are if i need to get a voltage regulator or not? The ACR will take care of isolation The engine in the boat is a Perkins 4.236, and i remember reading somehwere that the voltage output on these motors is too high for the gel battery and will kill it in a short period of time. Any help on the matter would be appreciated.

Thanks.
apowell is offline  
Old 03-05-2013, 09:51 PM
  #2  
Senior Member
 
Join Date: Aug 2012
Posts: 2,418
Default

Originally Posted by apowell View Post
Hey guys, i had a thread a little while ago about a single diesel boat with three batteries. I still have the same boat, and the time has now come to get down to business as boating season is around the corner.

Here is what i am working with, i have a lead-acid starting battery and a gel house battery. i was originally looking at having three batteries, but am now going with 2. I have a Blue Sea add-a-battery ACR charging relay on order and will use to isolate the batteries while only having one battery switch on the boat.
This is not a good idea.

While I am normally a fan of using an ACR/VSR to distribute charging current between multiple battery banks, that presumes use of the same (or at least very similar) battery types all around. But in this case, it could lead to some serious problems: Gel cells and flooded batteries have significantly different charging requirements. In particular, gel cells are VERY intolerant of over-voltage during the absorption and float stages, and their acceptable limits are significantly lower than those for AGMs and flooded-cell types. Hence, tying them together with an ACR and charging them from a common source will ensure that either the flooded battery is never fully charged (which not only cripples its performance, but also shortens its long-term life expectancy), or that the gel cell is OVERcharged (and probably damaged or destroyed in the process).


My concerns are if i need to get a voltage regulator or not?
What sort of voltage regulator did you have in mind? You already have one such, as part of your engine's alternator system. The problem is that it can only "regulate" to one particular voltage at a time; and that one voltage cannot be right for both different battery types.


The ACR will take care of isolation
Well, sort of. But it only "isolates" the batteries when there is no charging current/voltage present. The problem starts when there is a charging source applied, at which point the relay closes and puts both batteries in parallel.


The engine in the boat is a Perkins 4.236, and i remember reading somehwere that the voltage output on these motors is too high for the gel battery and will kill it in a short period of time.
Near-certainly true; but I highly doubt this is specific to that particular engine. Gel cells were never designed to be starting batteries, or to be charged from the (typically crude) output of an engine-mounted alternator.


Any help on the matter would be appreciated.
Your best bet is to replace the gel cell with one or more (as needed to meet your capacity/packaging requirements) high-quality AGM batteries, then proceed as you initially described with the ACR. You can probably defer replacing the (presumably flooded open-cell) starting battery until it finally wears out, as the charging requirements of AGM and flooded types are pretty close (at least as compared to gel cells). But when that times comes, it too would ideally be an AGM type.

As far as the switching is concerned, you DO need the capability to connect and disconnect BOTH battery banks from their loads, as well as to (temporarily) change their load assignments and/or put them in parallel for emergency engine-starting. Assuming this is a single-engine application, this requirement can be met with EITHER two conventional single-pole "1-2-Both-Off" switches, or one dual-pole switch such as the Blue Sea System #5511e http://www.bluesea.com/products/5511...Battery_Switch.



Itteldoo is offline  
Old 03-06-2013, 04:59 AM
  #3  
Junior Member
Thread Starter
 
Join Date: Nov 2012
Location: Bermuda
Posts: 12
Default

thanks for the relpy. i was under the impression that this would be the way to go (replacing the gel with an AGM) but i only bought the gel a few months ago for a hefty price, so was trying to avoid this.

but as you stated this is the best way to go!
apowell is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread