Kind of reminds me of when I was doing solar systems for houseboats. Doesn't matter how many 'fail safe' features, meters, or gadgets I added, there was always generators running all over the lake during the day. I always said a silent prayer..
Good we all sort of agree,trolling batt.'s are a hit an miss at best,like anything else that has some scientific theory behind it books don't teach you life nor reality,the real world is usually what you have experienced an Know to be Fact,that's why we have these forums,find a likely match to your Q an go for it,do a little trial an error in real conditions an you'll be OK.......I Hope!!!!!..LOL........Don
Don, I'd base it on worst case scenario, then you have plenty of power for anything that comes along.
Like I said one needs to know the "Max" amp draw of the motor and everything else connected to the bank. If you don't have the time or the test equipment, to load the motor and find the max amps. One could possibly use the fuse rating to go by which might give you quite a bit more back up to boot.
The sad thing in all this is there are fourmula's to figure these kinds of things out, that can get a layman a close idea of what he needs.
BUT, you throw in things like, how old are the batteries that you are using, have the cells been kept wet, have the batteries always been charged properly?????? And on and on and on, then i agree that Murphy will rear his head.
Then on top of all that you add a few guys on the internet with nothing better to do, and here comes the cluster mess
Heck, the easiet way to do it get a battery monitor (a fuel guage for batteries) set the alarm on it........... When it goes off fire up your motor and give the batteries a filling back up
.....all that calculating stuff is OK under a constant load but vary the load an it won't do ya any good on the water,.....
Correctomundo Don, and, not one single trolling motor will give you electrical draw for a 'windy' day
Even if you (and you should) calculate your needed storage/usage based on the solar industry's guidelines, you could still find yourself in a conundrum on the water. If you must rely on battery power, you must multiply the appliance max usage draw 1.5 times the max possible hours usage and multiply that by the 2.0 safety factor. Even then you need a backup to Murphy.
Very simple to answer. One just needs to know the max amps/watts the motor uses, and the amp hours of the batteries on board.
There's a tons of amp/hr calculators available if you google search. Many of which are from the solar community.
If draw down and charging is going to be big, look at golf cart batts to give you longer battery life. They are cheap and have numerous cycles per life.
IS TRUE.You go out on any givin lake an you never know what kind of demand your going to put on your batt.'s,Koke fishing is probably the most constant,usually I'll get 6+ hrs on a no wind,glass lake,with 2 people an gear,add a bunch of wind a third person speed above 1 mph an the same batt.'s will give out in 4/5 hr's on my boat,all that calulating stuff is OK under a constant load but vary the load an it won't do ya any good on the water,the only way to get a good guesstament is experience an time on the water useing an electric under diff.situations an with a load that goes from minor to extreme.....
Let's start with the golf cart battery scenario. They are 6v 220 ah batteries so it would take two for a 12v trolling motor and you still only have 220 ah of storage. And they are heavy. You can get 2 12v bats with 200 ah of storage and that would give you about double the storage. But, you can also wire the system so the main motor charges ALL the batteries and yet the trolling motor will NOT run down the battery for the main. This is good because you will never get stranded and you can charge the batteries by running the main in neutral. There may also be a kicked up alternator for your main motor which would be a plus. There are many solutions to your problem. Just pick one
How long do your batteries last while trolling? We're seriously considering this option at this point if it will get us moving to 2 mph or so in a current.
That is an impossible Q to answer,I can tell you about my own exp.for what it's worth,I have a PD V2 co an auto pilot 60" shaft 70#thrust,the first boat it was on was a old 83 seaswirl very heavy boat Guessing 3000 lbs loaded,I could troll 6 to 7 hrs for koke at .5 to1.5 ,for trout at 1.5 to 2.5 about 5 hrs,those times varied with wind etc.ON my new crestliner 19' I get about the same times an the weight is about the same due to all the stuff I have added to it even though it's aluminum,I have ran the new boat faster when fishing for browns at 3 to 3.5 an the batt's died in about 3 1/2 hrs,I run group 27 interstate batt's an I always carry 4 on board cuz you never know really the shape they are in even though they show fully charged stuff happens,I haven't run against current like in a river but depending on how strong it is you may find your max speed very low like .5 or 1 mph an you will kill your batt's within 2 hrs I would guess.I have been in 2 to 3 ft.chop with high winds an just to troll for koke or trout have killed the batt's in about 3 hrs.So as you can see there's to many variables to be real accurate.the currant thing is the real kicker,how much currant an what are you fishing for,if you are around Rio vista with a little wind an chop I don't think you would last more than 2 hrs if the motor could even maintain course very well without a added oversize skeg....Any help...LOL....Don