Dumb question about running 2 lithium cranking batteries in parallel...

[TNfish3]

Right now I've got 1 125Ah Ionic lithium battery that is running everything except the trolling motor on my Phoenix 920 Elite. Looking to get a 2nd lithium battery (this 2nd one will be a 100Ah battery) and running it parallel with the cranking battery to increase my fishing day. Dumb question, but if I run a 125Ah cranking battery parallel with a 100Ah "regular" (not listed as a cranking battery), it shouldn't make any difference with cranking right? A local shop said I should run another cranking battery as the 2nd battery, but I can't seem to figure out what difference it would make, other than that's the battery they want to sell me (higher price tag...).

Thanks

[yam911]

You are correct. Two batteries in parallel, even of different sizes, will provide more power than either battery alone.

Since one of the two is not a cranking battery it could, repeat could not will, shut itself down if the amount of current flow exceeds what ever limit the BMS is set for. But that should not matter given that the other battery is more than capable of starting the motor on its own.

[bobcoy]

Ask someone else (battery seller) their opinion. If you don’t trust the seller, buy it from someone you do trust. As Yam said, there could be a conflict caused by different specs on the BMS. Bob

[TNfish3]

You are correct. Two batteries in parallel, even of different sizes, will provide more power than either battery alone.

Since one of the two is not a cranking battery it could, repeat could not will, shut itself down if the amount of current flow exceeds what ever limit the BMS is set for. But that should not matter given that the other battery is more than capable of starting the motor on its own.

That's what I was thinking...

[yam911]

Here is a deep cycle non cranking battery that says it has 900 CCA output. More than enough to start most any Yamaha outboard motor.

I don't know what model and brand you have.

Interesting to me that they comment about it starting a 200 HP Yamaha when many many Yamaha V6 VF200's, F225's, F250's, F300's and V6F350's use the same starting motor. Same amount of current to crank and start the motor.

[TNfish3]

Here is a deep cycle non cranking battery that says it has 900 CCA output. More than enough to start most any Yamaha outboard motor.

I don't know what model and brand you have.

Interesting to me that they comment about it starting a 200 HP Yamaha when many many Yamaha V6 VF200's, F225's, F250's, F300's and V6F350's use the same starting motor. Same amount of current to crank and start the motor.

That's the battery I was looking to run parallel with my 125Ah cranking battery. I've got a Merc ProXS 250, but it shouldn't matter since my big motor cranks now with my current cranking battery. I'll just call Ionic tomorrow morning to make sure...
Thanks for the replies!

[GOTTA BIG SACK]

Curious what Ionic says.

[TXSkeeterBells]

Drewcraft I just noticed has the 125ah dual purpose on sale for $150 more than the 100ah. If it were me I’d just get the 125ah.

[justinp61]

I’m far from a battery expert but wonder if the all purpose or dual purpose batteries are designed to handle the alternator charge from the OB and maybe the standard batteries aren’t. As mentioned different BMS.

[TNfish3]

Called Ionic and was told that I could use the 100Ah battery and it would work fine for my setup. Going to the 150Ah "cranking" battery would only add run time since it's a 150 vs a 100Ah.

[TNfish3]

Drewcraft I just noticed has the 125ah dual purpose on sale for $150 more than the 100ah. If it were me I’d just get the 125ah.

I called Drewcraft too. He advised the 100Ah would work just fine in my setup. Also, the 100Ah is the same size as my current 125Ah so I can put them side by side in a double tray. The 150Ah cranking battery for $700 is a group 31 size battery and is much bigger.

[TNfish3]

How long of a run is considered too long for the wiring running between the 2 starting batteries? My spare prop is mounted in between where the 2 batteries will be so I'm looking at probably an 18" run from 1 battery to the other battery. I'll probably use 2AWG or 4AWG to overcome any resistance. Trying to figure out if this will work ok. I hate to remove the spare prop cuz then it's gotta get mounted in a tackle compartment, taking up valuable tackle space...

[jerzia]

How long of a run is considered too long for the wiring running between the 2 starting batteries? My spare prop is mounted in between where the 2 batteries will be so I'm looking at probably an 18" run from 1 battery to the other battery. I'll probably use 2AWG or 4AWG to overcome any resistance. Trying to figure out if this will work ok. I hate to remove the spare prop cuz then it's gotta get mounted in a tackle compartment, taking up valuable tackle space...

Not an issue

[DREWTICK]

Sense 2020 all Ionic 100ah have been dual purpose and can be used for cranking or in parallel with 125ah or 150ah

but to also clarify and only speaking of an Ionic, you can run a 50ah and a 125ah in parallel for cranking or a 60ah and a 150ah parallel, the cranking will carry the load of the cranking and the smaller will provide extra amp hours
we have not tested it with other brands or mixed brands but Ionic approved this setup 5 years ago and have many customers running it
our recommendation would be using at least a 100ah but never had any problem with the 50ah and 125ah , the main motor leads need to be directly on the larger battery

[DREWTICK]

How long of a run is considered too long for the wiring running between the 2 starting batteries? My spare prop is mounted in between where the 2 batteries will be so I'm looking at probably an 18" run from 1 battery to the other battery. I'll probably use 2AWG or 4AWG to overcome any resistance. Trying to figure out if this will work ok. I hate to remove the spare prop cuz then it's gotta get mounted in a tackle compartment, taking up valuable tackle space...

use a minimum if 4awg preferable 2awg , smaller size and longer cables will give you odd uneven charging charging

[Mahomee]

I called Drewcraft too. He advised the 100Ah would work just fine in my setup. Also, the 100Ah is the same size as my current 125Ah so I can put them side by side in a double tray. The 150Ah cranking battery for $700 is a group 31 size battery and is much bigger.

My 125ah Ionics are all group 31 size did they change them to a smaller case in the last few years. Mine have a chunk of foam in them to take up the empty space.

[z520brewer]

I am thinking my ionics 120ah is a group 27 but could be mistaken

[DREWTICK]

Ionic 100ah and 125ah have always fit a gp 27 tray, being 12x6" at the bottom, they classify it as a 31 because the top of the battery is 12 5/8", gp size is based overall length and with

the new 150ah batteries require a full size gp 31 tray being 13.3 x 7.3"

[GOTTA BIG SACK]

Wonder if you could use any brand to add with the Ionic? Say a 50 ah LiTime. How would you charge them? Just hook the one charger lead to the Ionic cranker and both would charge?

[Mahomee]

Wonder if you could use any brand to add with the Ionic? Say a 50 ah LiTime. How would you charge them? Just hook the one charger lead to the Ionic cranker and both would charge?

yes and yes