More Than 1 Cranking Battery

[Ripsalip2]

TY sir, appreciate it. One last question if you don't mind, appreciate your taking the time to help. If I add up the amp draw from electronics, for example, how do I calculate how much time I'd get out of a battery for a given amp-hour rating? I thought I had a handle on this, and now I'm confused. Lets say I have a total of 7 amps draw from electronics and a battery with 195min RC, 95Ah @ 20hr rate, 88.5 Ah @ 10-hr rate. Man, I thought I had a handle on this....appreciate any help.

Hey 1blue,
Glad to help where I can.
On that note, I by no means am an expert in the battery world. I know just enough to get me in trouble

With that being said, here's some info I've used to help me figure out amps,volts, run time, etc.

Reserve Capacity (RC) is the number of minutes a fully charged battery at 80 o F (26.7 o C) is discharged at 25 amps before the voltage falls below 10.5 volts. To convert Reserve Capacity (RC) to Ampere-Hours at the 25 amp rate, multiple RC by .4167. More ampere-hours (or RC) are better in every case.

For example, if your trolling motor is drawing a steady 20 amps and you want it to last 1 hour you would start out with Step 1:
C=20 amps * 1 hour = 20 AH
Then proceed to Step 2
C’ = 20 AH / 0.8 = 25 AH
Then take the high rate into account
C’‘=25 /.5 = 50 AH
Thus you would need a 50 amp hour sealed lead acid battery to run the trolling motor for 1 hour at 20 amps average draw.
Im sure this is clear as mud now. Lol.

Look up Lou r Pitcher here. He definitely seems to know his business when it comes to this stuff.

[1bluemcm]

No, that helps. Thanks very much. Yeah, agree, Lou is a batery guru around here. Thanks!!

[Phoenix Ed]

There is no such thing as overkill when it comes to your cranking battery. If you want to put 2 in parallel I think its a great idea. Currently on my boat I have an X2 Power 31 AGM (2150 CA 1150 CCA and 220 Reserve Capacity). I can fish 16 hours on it without putting my graphs in standby and still fire the motor up no problem. The X2 Power AGM is 2 batteries in 1. 1 dedicated for starting the motor and 1 for accessories like pumps and electronics. How does it work? I have no idea but its a BA battery. .

I've got the same battery, it is a beast! The Cabelas X900 is the same battery with different decals.

[haus9393]

I've got the same battery, it is a beast! The Cabelas X900 is the same battery with different decals.

Yep I see you link it all the time in threads. One of the many great accessories more my boat that I would not want to be without.

[Fishysam]

Anyone ever give a thought to wiring power poles off of one of the trolling motor batteries?

I have my two pole powered buy a tm battery each. I have 36v tm only down side would be increasing the possibility of wearing out 2 batteries before the third... I figure 2 times a year I'll switch the leads one battery at a time.

[xranger77]

Wiring two in parallel would be a good idea if you had concerns about draining with graphs and pumps in a 10-12 hour day. Or get one of those beast mode batteries Haus has.

If you do two, make sure they are the same. Dont want to mix a wet cell with a AGM. Identical batteries would probably be best.

[B. Dillon]

There is no such thing as overkill when it comes to your cranking battery. If you want to put 2 in parallel I think its a great idea. Currently on my boat I have an X2 Power 31 AGM (2150 CA 1150 CCA and 220 Reserve Capacity). I can fish 16 hours on it without putting my graphs in standby and still fire the motor up no problem. The X2 Power AGM is 2 batteries in 1. 1 dedicated for starting the motor and 1 for accessories like pumps and electronics. How does it work? I have no idea but its a BA battery. I also have the Tournament saver pro jump starter and I just got a NOCO Genius Boost HD jump start pack that is supposedly good for up to 40 starts on a single charge and rated for up to an 8.0L motor. I hope to never need to use it but its great piece of mind.

I have the same battery with (3) 12" Gen 2's. I get low voltage warning on graphs and they flicker after about 3 hours without cranking the big motor. Battery is about 3 months old.

[CatFan]

I'll be doing the same. That way both batteries are drawn down equally, giving you more than enough juice for everything for a day. Especially helpful if you have large electronics like HDS 12s.
I run a stealth charging system with one lead 31 series and only one 36 volt lithium pro trolling battery. 28pounds. My big motor charges up everything on the run. I have no plug in charger or one in the garage.
Plenty of room to add another battery in parallel to the cranking.

If your Stealth keeps the TM battery fully charged, then you have zero need for a second cranking battery. You could even downsize to a smaller cranking battery because your outboard is keeping your cranking battery near 100% charge or it would never put any charge into the TM battery.

[haus9393]

I have the same battery with (3) 12" Gen 2's. I get low voltage warning on graphs and they flicker after about 3 hours without cranking the big motor. Battery is about 3 months old.

Does the motor crank? And do the graphs show the same voltage at the battery directly?

[B. Dillon]

Does the motor crank? And do the graphs show the same voltage at the battery directly?

Yes, the motor cranks. Units display 11.77 and at the battery it's 12.68+. The console units are wired direct to the battery and the bow unit is wired to the switch at the console. Probably need to upgrade the wiring but really didn't start having this issue until the last couple of trips.

I think my options are upgrade the wiring or add another battery... adding another battery, I'd think, would solve it for sure. It's pretty frustrating.

[haus9393]

Yes, the motor cranks. Units display 11.77 and at the battery it's 12.68+. The console units are wired direct to the battery and the bow unit is wired to the switch at the console. Probably need to upgrade the wiring but really didn't start having this issue until the last couple of trips.

I think my options are upgrade the wiring or add another battery... adding another battery, I'd think, would solve it for sure. It's pretty frustrating.

I installed new wires on my graphs this winter and my voltage on the graphs are .5-.7volts less than my mercury monitor. But I've yet to measure my voltage at the battery to see exactly what that shows. I'm running my motor, jackplate, sonic hub, 4 graphs and 2 poles all on her. I need to put bigger wires in for my graphs.

[xranger77]

I ALWAYS go one size if not two, up from mfg recommended on graphs. I also wire direct as well, never tap into a power supply for todays electronics for best performance.

[DREWTICK]

TY sir, appreciate it. One last question if you don't mind, appreciate your taking the time to help. If I add up the amp draw from electronics, for example, how do I calculate how much time I'd get out of a battery for a given amp-hour rating? I thought I had a handle on this, and now I'm confused. Lets say I have a total of 7 amps draw from electronics and a battery with 195min RC, 95Ah @ 20hr rate, 88.5 Ah @ 10-hr rate. Man, I thought I had a handle on this....appreciate any help.

there are a few app to do this but here is a simple web app that might help https://www.batterystuff.com/kb/tool...to-a-load.html