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  1. #1
    Member bloodman's Avatar
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    AGM 100 and Ionic 125 in parallel

    What happens if these batteries are run in parallel?

  2. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #2
    Nothing useful. They have different open circuit voltages so one will discharge into the other.
    If you have integrity, nothing else matters. If you don't have integrity,
    nothing else matters.​

  3. Member bloodman's Avatar
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    #3
    Quote Originally Posted by CatFan View Post
    Nothing useful. They have different open circuit voltages so one will discharge into the other.
    You might reasonably think that but it has not happened. I have been running this setup since spring although they are linked through a 1, 2, both, off switch, so I can choose which to draw power from. There is also an isolator to both from the big motor. They play very nice together when in the both position...so far. No discharge while sitting in the garage according to the Ionic app.
    It seems that since the litho is normally at 13.3v, when in parallel this would be like a float for the AGM which draws little from the litho.
    I am not a specialist in this area and can only go by my experience.
    I have this setup because of the required AGM for the Mercury and since I have power steering with a kicker, I need the second battery.

  4. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #4
    Quote Originally Posted by bloodman View Post
    You might reasonably think that but it has not happened. I have been running this setup since spring although they are linked through a 1, 2, both, off switch, so I can choose which to draw power from. There is also an isolator to both from the big motor. They play very nice together when in the both position...so far. No discharge while sitting in the garage according to the Ionic app.
    It seems that since the litho is normally at 13.3v, when in parallel this would be like a float for the AGM which draws little from the litho.
    I am not a specialist in this area and can only go by my experience.
    I have this setup because of the required AGM for the Mercury and since I have power steering with a kicker, I need the second battery.
    Physically impossible for one not to drain into the other. They will equalize temporarily, then on the next use begin the draining process again.
    If you have integrity, nothing else matters. If you don't have integrity,
    nothing else matters.​

  5. Member bloodman's Avatar
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    Quote Originally Posted by CatFan View Post
    Physically impossible for one not to drain into the other. They will equalize temporarily, then on the next use begin the draining process again.
    I can watch it on the Ionic app. The only drain should be from the Ionic to the AGM correct? If the Ionic drains it is very small and of little consequence. Sometime this winter I will try a direct parallel between the two batteries to eliminate any parasitic drain caused by the boat.

  6. Member Texas Larry's Avatar
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    #6
    I agree with CatFan. The boat dealer that installed my Son-in-Law's new Ionic lithium's, paralleled the 125A lithium with an Optima Blue Top by just adding jumpers to the positive and negative battery posts. He wanted all the accessories moved to the lithium and the AGM to be used solely for cranking the 250 hp Mercury Pro XS. He is still having the low voltage alarms after several hours of fishing even though the lithium battery shows a 90%+ charge. We will be moving all accessories to the lithium and use the AGM solely for powering the Mercury.

  7. Member bloodman's Avatar
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    #7
    Quote Originally Posted by Texas Larry View Post
    I agree with CatFan. The boat dealer that installed my Son-in-Law's new Ionic lithium's, paralleled the 125A lithium with an Optima Blue Top by just adding jumpers to the positive and negative battery posts. He wanted all the accessories moved to the lithium and the AGM to be used solely for cranking the 250 hp Mercury Pro XS. He is still having the low voltage alarms after several hours of fishing even though the lithium battery shows a 90%+ charge. We will be moving all accessories to the lithium and use the AGM solely for powering the Mercury.
    Understood but this is not my experience and I have logged many many hours on this. I have watched the drain on the lithium from use while there is none on the AGM. I assume, all power is used from the lithium until it gets down to the same volts as the AGM and then, I assume power would be drawn from both. That has never happened yet since the litho has been plenty to power my needs. Both do get charge from the big motor while underway and I can watch that also. The lithium gets up to 40amps from the big motor while on the run.

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    #8
    Quote Originally Posted by bloodman View Post
    I can watch it on the Ionic app. The only drain should be from the Ionic to the AGM correct? If the Ionic drains it is very small and of little consequence. Sometime this winter I will try a direct parallel between the two batteries to eliminate any parasitic drain caused by the boat.
    That was my experience when my Ionic battery was connected to a flooded lead acid battery. The Ionic, having a higher resting voltage than the lead acid, supplied current to the lead acid. But only until the voltage of the lead acid rose to the level of the Ionic battery. When the voltage of the two batteries was the same the current flow was nil. Or so low that I could not measure it.

  9. Member bloodman's Avatar
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    #9
    Quote Originally Posted by yam911 View Post
    That was my experience when my Ionic battery was connected to a flooded lead acid battery. The Ionic, having a higher resting voltage than the lead acid, supplied current to the lead acid. But only until the voltage of the lead acid rose to the level of the Ionic battery. When the voltage of the two batteries was the same the current flow was nil. Or so low that I could not measure it.
    That is exactly what I think happens. So the AGM will be at 13.3 also and will be in float stage which is what is recommended at rest anyway. Seems like both should be happy then.
    Could this be a perfect solution to Mercurys no lithium issue? Seems to me it could be. Even if the lithium shut down there would still be power from the AGM. I dont know but so far its awesome.
    Last edited by bloodman; 10-08-2021 at 12:41 PM.

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    #10
    You should only connect similar batteries of the same chemistry and age in parallel.

  11. Member bloodman's Avatar
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    #11
    Quote Originally Posted by mwh624 View Post
    You should only connect similar batteries of the same chemistry and age in parallel.
    I've heard that but these seem to love each other. The AGM is very happy at 13 + volts. All manufacturers say you can keep them indefinitely at that level. The Ionic is also very happy and its bms protects it. I watch the Bluetooth app and no where it is always.
    Help me if I'm wrong because I'd like to know what could happen.

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    #12
    Quote Originally Posted by mwh624 View Post
    You should only connect similar batteries of the same chemistry and age in parallel.
    Why?

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    #13
    Yam, flooded batteries have a lower voltage than AGM and may not be optimal for direct connection. Keep an eye on the fluid level. I have read many successful AGM to Lithium stories. Can’t recall any flooded battery story till yours. Hope it continues good for you. Bob
    Tell me where has a slow movin' once quick draw outlaw got to go

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    #14
    Quote Originally Posted by yam911 View Post
    Why?
    Different chemistries have different nominal voltages as we as different discharge voltage profiles.

    As batteries age they can become less efficient, putting more load on the other battery they are in parallel with.

  15. Member bloodman's Avatar
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    #15
    Who has ever tested this to know because as of now its not my experience.
    This setup is to keep my Mercury engine happy otherwise I would have dual lithiums.

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    #16
    The lithium battery is the highest voltage and does not mind being less than fully charged. The AGM wants to be fully charged for a long life. 2 mismatched lead acids are a problem. JMO Bob
    Tell me where has a slow movin' once quick draw outlaw got to go

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    #17
    I connected my Li battery to a flooded lead acid battery. Fully charged for both.

    Current flow from the Li to the lead acid battery was 37 milliamps. Li was obviously keeping the voltage of the Pb battery higher than its normal resting voltage.

    Will this be a problem for someone? I can't say.

    Does not really answer the OP's question. Which I suspect would have less current flow between the two. If any current flow at all.

    Now in practice would I parallel an Li battery with a lead acid battery? Nope. Can't think of any good reason to do so.

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    #18
    Quote Originally Posted by yam911 View Post
    I connected my Li battery to a flooded lead acid battery. Fully charged for both.

    Current flow from the Li to the lead acid battery was 37 milliamps. Li was obviously keeping the voltage of the Pb battery higher than its normal resting voltage.

    Will this be a problem for someone? I can't say.

    Does not really answer the OP's question. Which I suspect would have less current flow between the two. If any current flow at all.

    Now in practice would I parallel an Li battery with a lead acid battery? Nope. Can't think of any good reason to do so.
    I run a similar setup to Bloodman, except my 100 aHr Lithium house battery has a starter battery BMS in it. I also run the same style switch Bloodman does. A good reason to do this is redundancy for starting the outboard should something go wrong with my Batteries Plus XPower AGM battery. Since the house battery has a starting battery BMS it does the job of backing up the AGM starter very well. The house battery powers only my Lowrance LIVES on a dedicated circuit, and my starter battery powers all the original boat accessories (aerators, bilge, lights, etc.). This keeps the accessories off the same circuit as my LIVES so I get a better picture with no interference.

    Another reason besides the jump start for this setup is redundancy for the house battery. Should it fail for any reason I can switch that circuit over to the starting battery circuit and keep fishing the tournament. And since I have Stealth 1 Charger (AC and DC) I can even use the switch to equalize my lithium 100 aHr trolling motor batteries by temporarily switching the circuit to both starter and house while plugging into AC which then powers my DC charger to charge the trolling batteries.

    So while I normally only use the switch in the position 1 only (starter only) I have the option to switch it to both and perform other functions as well. I also can charge all my batteries from my Yukon AT4 using the TowNCharge from Stealth Charging.

    This setup is the best I have ever used in 45+ years of tournament fishing.
    ciao,
    Marc

  19. Member bloodman's Avatar
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    #19
    Interesting Marc and thanks for your input. How'd you figure all that out?
    My big motor positive goes to the switch so it gets its power from either or both. The charge from it goes to the isolator to distribute to each battery. If the lithium shuts down for wherever reason the alternator should still send power the AGM which should prevent any problem with the Mercury and is the reason I have the AGM anyway. I was not ready to use my Mercury without the AGM so still testing before full switchover.
    So far this system has not drawn enough from the lithium to get into the AGM which should mean the AGM will last a very long time.
    These lithiums have opened a new ball game for power. I hope others offer their experiences with them too.

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    #20
    Quote Originally Posted by bloodman View Post
    Interesting Marc and thanks for your input. How'd you figure all that out?
    My big motor positive goes to the switch so it gets its power from either or both. The charge from it goes to the isolator to distribute to each battery. If the lithium shuts down for wherever reason the alternator should still send power the AGM which should prevent any problem with the Mercury and is the reason I have the AGM anyway. I was not ready to use my Mercury without the AGM so still testing before full switchover.
    So far this system has not drawn enough from the lithium to get into the AGM which should mean the AGM will last a very long time.
    These lithiums have opened a new ball game for power. I hope others offer their experiences with them too.
    I once got a small paycheck in a BASS Invitational tournament on the Columbia River instead of a big paycheck because my trolling motor batteries failed before noon due to high winds and current. So that started many years of study, and learning from others smarter than me. I always figure every problem has at least one solution; you just have to find it. In 2007 I learned about Stealth 1 charging systems, and made the switch and never looked back. I recently exchanged my charger which was still in great condition, but wasn't setup to be ideal with my lithium trolling motor batteries and my lithium house battery. Stealth makes a model for different chemistries and configurations, so I got one ideal for charging my AGM X2Power starter while also being ideal for my lithium house battery and three trolling motor batteries. All in one charger.

    In my research I discovered that there are differences in lithium batteries and particularly in their BMS. Many don't realize some lithium's are setup to be used as starting batteries (similar to the differences between lead-based storage batteries and lead-based starting batteries). BTW, if you are using a lithium starting battery one should consider getting a Sterling Pro Protect which is designed to protect your outboard's charging system. You might consider this for your house battery if you ever want to leave your switch in the both position while running the outboard. I bought one in case my lithium starting battery being used as a house battery ever quits...in which case if I replace it with a lithium storage battery I will have an extra measure of protection. For now I don't need to install this as I am doing great with the 100 aHr lithium starting battery for running all electronics.

    Like you I am not afraid to try out solutions to problems; and I still listen to the warnings but try to take steps that solve the problem rather than just fixing the symptoms of the problem. Sometimes it comes back to bite you, but so far the rewards have outpaced the consequences.
    ciao,
    Marc

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