Charging the trolling motor under way

[HarleyC]

I have a Force 125 1986 model want to check the out put for the Alternator but do not know how or where to hook up the Amp meter. It seems to charge the battery ok, and now I want to know if it makes enough juice to charge the trolling motor using an Diode Isolater system. Thanks for any advice HArley

 

[almost retired again]

Re: Charging the trolling motor under way

Hello Fishboy100,<br />The ampmeter should be connected in series with either of large wires that connect to the battery. With the larger current that some of the alternators on larger outboards deliver today I would suggest using at least a 50 amp meter. You can also use a clamp-on ampmeter on either of those large wires. This is probly the easiest as you don't have to disconnect anything. If your outboard alternator puts out more than your boat normally uses, then your plan is sound.<br />Have Fun

 

[HarleyC]

Re: Charging the trolling motor under way

ARA, I don't know how to hook up the meter in series. Does that mean pos to pos neg to neg at the battery? HArley

 

[DJ]

Re: Charging the trolling motor under way

fishboy,<br /><br />That means in line with the positive battery cable. Example, one lead on the pos. battery post and the other on the disconnected pos. batt. cable. All current then goes through the meter.<br /><br />The inductive (clamp on) ammeters are much simpler.

 

[HarleyC]

Re: Charging the trolling motor under way

DJ Thanks for the reply. OK, I think I got it on the hook up. Another question: can I disconnect the ground cable from the neg battery post while the engine is running without damaging anything? Or should I put the meter inline before before starting engine. Hope this makes sense. You help is much appreciated.

 

[alcan]

Re: Charging the trolling motor under way

Hi Fishboy<br /> Never run the engine with out a good battery connected to the circut. Do all connecting with engine off.

 

[Boatist]

Re: Charging the trolling motor under way

FishBoy100<br />Since you need to hook it up before starting your meter needs to be able to handle current in both directions. Also since you then need to start motor need to be able to handle starter current, at least 60 amps. also unless your battery is low may not charge at full amps for more than a few sec after starting. I think would be easer to look up the amps output on your motor. Should be listed in the manual.<br />One way you could get buy with a smaller amp meter would be to hook up a shunt in parallel with meter. If you have a battery switch wire your amp meter in Parallel with switch. Turn switch to on or battery one and start up then turn switch to off so all the current goes thru the amp meter. <br />In general I would say not a good idea to try and charge trolling motor battery with a outboard alternator. I do not have a Force motor manual but the 2002 Merc 125 2 stroke is 18 amps the optimax 135 belt driver is 60 amps.<br />If you have a big I/O 100 amp alternator or the 60 amp like on the optimax it may make since.<br />Here is the problem. Your trolling motor usually has a big battery and lots of drain on it so it can be very low voltage and take a lot to charge up. With a battery isolator you drop about .7 volts to each battery. Since the trolling motor battery can be very low it will take most or all of the charge from your alternator. When it gets charged to a point where voltage is higher than your starting battery then your starting battery will start to get charged. If your trolling battery is run down like I have seen at the end of the day on many bass boats. When you start up all your charge is going to go to the trolling battery and starting battery will get nothing. Also your alternator is going to be putting out max amps and even if you run 2 hours is not going to have charged your trolling battery and your starting battery has got nothing. Since outboard alternators are inside a closed cover with no airflow when charging at max amps they can get so hot they burn up. Just my two cents.

 

[Yepblaze]

Re: Charging the trolling motor under way

You can surely attach one of those diode type isolators without a problem but, the output of most outboards won't have the capacity to charge your trolling batteries. <br /><br />Charge them at home or camp, and keep their amp hour capacities as such to support a days fishing.

 

[HarleyC]

Re: Charging the trolling motor under way

Hey thanks Yepblaze and Boatist. Thats some good advice you gave and I appreciate it a lot. I think you may have answered my question. Since my trolling motor battery is one of those big "truck" ones, I agree that it may never get charged enough to cause the DI to swith over charging to the starting battery which is a goup 27 deep cycle marine and is much smaller that the TM battery. Fishboy