Charging Deep Cycle Battery 70HP Johno

[Barrymundi]

I am looking for a bit of advice please.

I have a 70hp Johno with a normal battery for cranking and sounder. This battery is charged though the motor.

I have a deep cycle up the front for my Minn Kotta.

The big plan is to be to charge the Deep Cycle whilst moving around with the Johno running but keeping the Main battery isolated to avoid flattening and not being able to start motor.

Is the output from the charging circuit on the 70hp Johno of sufficient size to put enough juice back into my deep cycle ?

How do I isolate the main battery AUTOMATICALLY?

Any advice would be appreciated.

Thanks

Alan Deaner

[macca]

From past readings I have come to the conclusion you would do more harm to your dc battery by giving in little charges from your motor.

When it would be more effient to run your battery down when fishing and then do a proper recharge using the appropiate charge when you get home.

This would give you better performance and longer life from your battery.

My thoughts

Macca

[peterbo3]

Hi Alan,
My Mariner 75HP puts out 18 amps at WOT. I think the 70 Johnno would be about the same. A MK can draw up to
40 amps (average but may vary).
In theory you are going to have to run at WOT on the OB for more than two hours to make up for each hour of MK use. :(
I'm with Macca. It is not a cheap way of topping up your deep cycle. :o Perhaps 2x130 ampHour would be the way to go.By all means fit the battery changeover switch ($70 for a good Perko) but I would put the $70 towards a second deep cycle battery. 200+AH capacity would give you five hours plus of constant use on the MK. Recharge the deep cycles at home.

[Barrymundi]

Reason for the question.

I am going away for 2 weeks fishing with no power, maybe a genset.

Travel 1hour each day in boat.

Minn Kotta is only used for steering or holding boat not trolling.

In an average day it will work about 4 hours per day

[Rev]

What sort of Deep Cycle Battery? ???

[Barrymundi]

12V 90AH

[caveman]

take your charger with you and charge your battery off the genset

[peterbo3]

Evening Alan,
Please disregard my previous post if you saw it as I was unaware of your battery size & MK usage.
If you are running your MK four hours per day your current drain will not be replaced by the two hours OB charging. You will need to run the genset to power your battery charger. What will be the max draw from your MK? If you don't have your manual the MK site has a list of motors & what amperage each draws.

[rwells9999]

Hi Allan,
Have a look at an article on the 4th August "Myths and facts on dual battery setups". It should answer most of yor questions.
Robin

[Barrymundi]

Thankyou,

That is the posting I was looking for but could not find the other. It is close enough for me. I do not want to crank from my second battery.

Alan

[NQCairns]

Hi Just a word of caution some of the Johnson year/models dont like running on anything less than a full battery (battery CDI) can cause expensive CDI replacement (often), yours may be alright though, but keep in mind. Got something on file somewhere, will dig it up if you are interested. cheers nq

[Barrymundi]

I would like to read that if you can find it.

Thank you

[NQCairns]

Hi Barry I just had a search through my files but had no luck finding the piece I probably have backed it up somewhere or just named it poorly if i find it I will let you know. Give a friendly mechanic a ring about your particular engine and low battery better safe than sorry. good luck.nq