Thruster Battery Type

R

rick&sue

Well-known member
Joined
Feb 5, 2014
Messages
135
Fluid Motion Model
C-248 C
Hull Identification Number
FMLT2506J607
Vessel Name
POPEYE
The thruster battery failed a load test, so I purchased a group 27 (flooded) cranking battery as a replacement. After buying the cranking battery, I’m second guessing myself – wondering if I should have bought a deep cycle battery. The thruster battery is not tied to any other battery group and it operates the winch and thrusters only. I can’t find anything addressing this in the archives, so I am asking if any of you have direct experience with using a cranking battery versus a deep cycle battery for the thrusters? I will be putting the boat in the water later this week.
 
Just wondering how you will set up the charger if all the batteries are not similar. On my charger there are different settings for different types of batteries. I do not know how important this is or if if makes much of a difference.
My understanding is the deep cycle batteries handle having their charge depleted repeatedly better then a cracking battery. So they handle heavy use better.
 
Mark is spot on, they should all be the same. In addition if you run the parallel switch, to combine all your batteries, I would think they'd all need to be the same type of batteries.

Jim F
 
Hmmmm. I thought lots of people had starting and house batteries of different types. No?
 
Opens up a good discussion point and I am guessing has more than likely been discussed at sometime on the forum. I understand all the batteries need to be the same when it comes to type such as all AGM, all flooded cell, etc. But, do they all need to be the same series? All Group 27 yes and fully agree, but does the charger know how to distinguish between say a flooded cell start battery and a flooded cell deep cycle? When my AGMs give up (going my 6th season) I plan to revert back to flooded cell. Was planning to use a Gp 27 Interstate Start Battery for the MCA needed to spin my Cummins and three Gp 27 Walmart Deep Cycle for house and thruster (I have my thruster and house batteries wired together to provide higher amps to the thruster when needed or additional amps in the cabin). In reading the comments it kind of leads me to believe I should not do this. Or should I read they just all need to be flooded, AGM, etc.?
 
The charger has only one setting for all three banks supported. Thus the battery's need to be the same types but not size per bank. If you plan to connect batteries in parallel for an unattended period of time they should be as close as possible and I would even pick the same manufacturing batch. The word here is "unattended" meaning unmonitored either by person or electronic device.

If a cell in parallel batteries develops a problem, like a short, the other battery would try to compensate and bring that battery to the same voltage which can result in fire or explosion. If seen picture of that event after
 
Hello Rick,

I THINK you are fine with a "start" battery for the thrusters. Since the thrusters use large amounts of current over a short period of time, much like a start battery, then are immediately recharged, their service life is the same as the engine start battery.

Compare this usage to the house bank (i.e., "deep cycle"), whereby they are slowly discharged - often "deeply" then charged back up.

I think the START type battery will work fine for the thrusters; and the deep cycle would work too just to be clear.

You will need to review the charging circuit on your boat...when connected to shore power, do the Automatic Charging Relays (ACRs) function to parallel ALL the boat's batteries into ONE Bank? I suspect their may be a "charging lead" from the multi-bank charger going to each bank, but if the ACRs close to effectively create a parallel situation, the charger really "sees" one bank - not 2 or 3. In another thread recently someone stated the "Parallel" switch did NOT include the thruster battery, so maybe it remains 'alone' during charging. The forgoing comments pertain to "shore power" charging. That is the ONLY time our boats can possibly get "per bank" charging; i.e., when the main engine's alternator is the only charging source, ALL batteries must (somehow) become paralleled in order to receive a charge.

/dave
 
A true deep cycle battery is the golf cart type and are very heavy because of all the lead and they aren't cheap either. Then you will see deep cycle and deep cycle dual purpose. These are better than your average cranking battery because they can discharge slowly over a long period of time. A cranking battery is made to have a quick discharge and then recharge. I use the standard (not golf cart) deep cycle for thruster, and house and have a switch to group the thruster to the house. In reality you are running the engine when using the thruster and the alternator puts out quite a bit of amperage so my opinion is a regular deep cycle is fine. For my engine I use a dual purpose. The important thing is that all batteries be the same, either flooded, agm or maintenance free and this has to do with how the charger is set to charge the batteries. Since our batteries get coupled via the relays at any given point they are grouped together and are being charged as per the setting on the charger. So if you mix the types you could cause damage to the battery not compatible with the setting. For my money, I go flooded and replace them every three years.
 
Thanks for the info guys. And I should clarify, from what I have read in the past, the batteries should be the same "type" (as in flooded, AGM, etc.) but can be different in other ways.

Jake
 
From what I can decipher, the perfect (battery) world is to have all the same chemistry, all the same group size, all the same brand and all the same age. As you vary from perfect, you shorten battery life due to imperfect charging (rates and voltage) and/or current draw/time for your specific duty. My thought process was that thrusters require high current draw for short periods of time, so a cranking type flooded cell made sense to me. The big issue is that they don’t like to be discharged more than 30%. The thruster battery is connected to the solar charger, engine alternator and 120 volt charger as is the house and engine batteries. The thruster battery is not connected to the outputs of any other battery; it runs the thrusters and winch only.
After digesting all the info, I think the winch will be the item that will challenge the cranking type battery – takes time to winch in 150 feet of rode. The battery will most likely be discharged more than 30%. The good part is the engine is typically running when using the thrusters and winch so the alternator will be charging the same time the battery is discharging. Obviously the alternator will not keep up with the current draw of the winch or thrusters, but will be adding a small amount of current into the battery. We are putting in at Green Bay, WI and spending a month or more circling the northern portion of Lake Michigan. It will be an interesting test……. Thanks for all the comments.
 
As long as batteries connected in parallel are of the same CHEMISTRY, AND if they are properly maintained, then group size, starting vs deep cycle, etc. is not an issue. For a given chemistry each cell produces the same voltage and that's all that matters as far as compatibility. However.... few of us "properly" maintain batteries so it is best to use the same group size and type for batteries in parallel banks. Also batteries of different age/service life should NOT be connected as a parallel bank. Batteries used in a bank should be born, live their lives, and die together. The theory is that if they are of the same chemistry and type and have experienced the same history of load, cycles, etc, then they will be in the same condition. Batteries in different condition connected in parallel can cause serious problems (as someone already mentioned).

As to the question of starting vs deep cycle for the thrusters, it depends. If you only use them while the engine is running, then it really doesn't matter. Think about it. When the engine is running the ACRs are all closed. So essentially all of your batteries are in parallel and you have one big battery bank servicing all loads. So whatever the total amp capacity is of the combined bank is available for applied loads. Plus the alternator is running. If you listen to your engine when you activate the thrusters you'll hear the engine take a load as the alternator "feels" the current draw.

But, if one were to use the thrusters when the engine is not running, then in theory a high amp capacity (aka starting) battery would likely be a better fit.
 
My boat is an older model - I don't have ACRs; only a battery isolator for the alternator. The solar panel and 120 volt charger are connected directly to each battery bank. If I understand correctly, power demand (Load) is not shared between the banks as long as there is no load side battery combiner switch on. Only charging current from the alternator is shared through the isolator. Diodes in the isolator prevent current flow between the banks of batteries. All that said - I was hoping someone else had installed and had history on using a cranking battery in a thruster/winch application. This next month on the water will be a test.....
 
rick&sue":1dwuv3a5 said:
My boat is an older model - I don't have ACRs; only a battery isolator for the alternator...
Click to expand...
Oh. OK just ignore my previous post. Good luck 😀

Joking aside, a starter type battery should be healthier for the thruster motor. It will see less voltage drop than with a deep cycle. Voltage drop causes the motor to pull more current which means heat which is not good.
 
You could save significant wear and tear on the battery and thruster by adding a power control unit which gives you gradual power based on joystick deflection. Unfortunately they are a bit pricey. But there is a priceless satisfaction if you can use the thrusters silently with just enough power as needed to create that push not to mention that you would save that precious little shear pin from failing 🙂
 
All comments appreciated!! There is a whole boat load (pun intended) of very smart people (waaaay smarter than me) on this forum. I have learned considerably from all of you. Sue and I are relative newbies - Three separate month long trips on the water have been trouble free thanks to the info learned here.
Rick
 
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