Battery charger for marine grade dual battery setup

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

mechanixhorseman

mechanixhorseman

10 Year
Joined
Feb 28, 2010
Threads
24
Messages
427
Location
SO Oregon
Well I finally got around to installing my dual battery setup mostly detailed here.

https://forum.ih8mud.com/showpost.php?p=8525886&postcount=1138

I used a similar battery setup that I've noticed a few others of you have went with using Die Hard Platinum Marine Group 31M and 34M batteries. Conventional wisdom seems to be that these are just rebadged odysseys at a better price. The specs and packaging seems to confirm that. As awesome as these batteries are, further research has revealed that most traditional battery chargers are not recommended for batteries of this grade as they do not have a sufficient amperage output for charging. Odyssey lists acceptable chargers for each of their batteries here:

http://www.odysseybattery.com/documents/ODYSSEYapproved12VchargersOCT2012.pdf

and specifically identifies their OMAX-50A-1B as the minimally sufficient charger for the 31M, link here:

http://mudflaps.com/i-10079301-odys...mizer-battery-charger-50-amp-single-bank.html

I read somewhere else that the 31M requires a minimum charging current of 40amps. My first question is, is there anything special about this charger other than its high amp output that makes it suitable for the 31M/34M? Could I use any smart charger so long as its rated for more than 40amps charging current?

My second question is whether it is necessary to disconnect the batteries from the relay while charging them? I'm assuming so, since once the controller has detected that the primary battery is sufficiently charged the relay will link the batteries together, effectively splitting my charging power between the two with a negative effect on their health.

Thoughts?
 
Bump for good questions...

I'm about to throw in a second battery and would like info on this as well. Searching through old threads- it doesn't seem like there's a clear consensus on a good charging setup...
 
I think any charger that follows this algorithm should be ok. Per Odyssey they recommend 14.7 V for absorption and 13.6 V for trickle charging at http://www.odysseybattery.com/chargers.html. I know a lot folks pick solar charge controllers that can be programmed or switched to different charging algorithms (Reg. Lead Acid, Gel, Sealed Lead Acid....) All these have different voltages for abs. and trickle charging.

I think the external battery charger is probably more needed for the auxiliary battery than the starter. Do you know approximately the % charge of the starter and auxiliary?

I think the main thing for the charger is that it has the correct charging algorithm (with the higher voltages required by AGM vs. traditional lead acids). The higher current capacity of the charger only helpful to recharge your battery system faster than a lower current system. The stock alternator in our trucks is limited by the regulating diode and doesn't quite get to the higher voltage recommended by Odyssey / other AGM manufacturer's. On my group 65 Diehard Platinum, I find that if I only take inside roads and don't get on the freeway (<35 mphs / stop and go), my battery will sit at between 85-92%. If I head on the freeway I can push that up close to 95-98%. So once a week I hook up my Odyssey OMAX 25 to top my battery off. I'm not sure what the charging current is for the 100 series charging diodes and if it follows any special / smart charging algorithm? Oh, one nice thing about the Odyssey OMAX line of chargers is that it displays the % charge of the battery. A lot of the battery monitor systems that I have seen offered like the National Luna / IBS only show you a qualitative read out and don't give you number. Might need a power meter like a Watt's up or similiar system with a shunt to get that info for both batteries.

I have read a lot of the auxiliary batteries regardless of the isolator system need a larger amount to top off when compared to their starter battery mate. I'm only speculating but I think the stock charging system isn't fully able to top off the first battery before the isolater system will kick in to let it charge the second battery. I don't think it's the alternator's fault per say but rather the regulatory charging diode. A couple of folks in Oz have tried to boost their charging system like here: https://forum.ih8mud.com/100-series-cruisers/503895-alternator-voltage-booster.html (available through ebay). Or one could get new smart charging system like this: http://sterling-power-usa.com/proreg-B-12voltadvancedalternatorregulator.aspx that can adjust for battery type and would bypass the OEM charging diodes.


One thing that seems to really apparent, if you read the reviews on sears.com for folks with stock dual battery set ups like in the dually Ford / Chevy heavy pick up tricks and other forums for those respective trucks. They really kill their AGMs, which again (I think is) due to the stock charging diodes limiting the charging voltage in their trucks and not using a battery maintenance or trickle charger.

For some back of the envelop calculations, to get the approximate capacity of the battery, one can take the reserve time of 205 minutes x (0.5 to 0.6 conversion factor to get amp hours at 20 hr rate) = 100 amp hours at the 20 hr rate. So if you have a half depleted battery, you need to replace 50 amp hours. But to account for internal resistance you should include a correction factor of 1.15, so 50*1.15 = 57.5 amp hours. So if one could use all 50 amps of the charger at once, it should take just over 1 hr 9 mins. However the smart chargers in order to protect the battery from overheating/gassing will probably stretch out the charging time by going through the phases of bulk, absorption, and trickle/float charging will take like 4-8 hrs? I've not run my Group 65 battery down that low before so I don't know how long it would take.

So I think for the starter you might be good with a 3 to 5 amp battery tender style charger designed to work with AGM (only going from ~85-95%). But for the auxiliary battery if you run a lot of accesories off it and run it down (around 50% charge remaining) that a 20 amp charger (assuming it's the group 34) should be sufficient.

I don't have a second battery installed yet, but it's in the plans for the future. I think the best way to manage it is to have a http://www.powerwerx.com/digital-meters/dc-inline-watt-meter-power-analyzer-powerpoles.html with a current shunt to calculate the amp-hours of each battery. I think there is a more expensive system that folks run in the from Bogart Engineering (TriMetric systems) http://www.bogartengineering.com/products/TriMetric.

Some other threads that might be of interest.
https://forum.ih8mud.com/electronic-toys/733391-agm-battery-management.html
https://forum.ih8mud.com/electronic-toys/705147-smart-alternator-regulators.html
http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/

Yah sorry in advance for too much typing lol.
 
You clearly have a much better grasp of battery technology than I do and I appreciate the detailed response. I'm still confused however, as to why the group 31M requires a 40amp charging current and the 34M a similarly high current. If I could use a 5amp charger, why wouldn't they have identify any other chargers as suitable for those batteries? I don't think it is a matter of pushing the more expensive product as they are listing off various chargers from their competitors as well.

I've considered the various ways to improve the onboard charging system, but it seems that given the highly inconsistent nature of driving regularly in varying conditions it would be more prudent to just figure out a proper way to maintain your batteries on a monthly basis.

I have pretty much relied on the IBS' level meter (with the engine off) to get the current levels of each battery, but as you've noted, the meter doesn't exactly quantify the current levels into useable numbers. I may just end up dropping the $200 some odd dollars on the OMAX-50A, but I won't be happy about it.

So then the next question is, will the relay isolate the primary and aux batteries while charging or will it open the connection once the charger is attached to the primary battery?
 
Last edited:
Call Advanced Battery Systems and talk to Mike about a proper charger for the Odyssey batteries. Tell him Scott at Perfect Switch suggested you call. It will be worth your time. 323.333.0358
 
Scott, I should have called you in the first place. I forgot you specialize in isolators and similar components. I'll give him a call sometime this week. Thanks.
 
mechanixhorseman said:
You clearly have a much better grasp of battery technology than I do and I appreciate the detailed response. I'm still confused however, as to why the group 31M requires a 40amp charging current and the 34M a similarly high current. If I could use a 5amp charger, why wouldn't they have identify any other chargers as suitable for those batteries? I don't think it is a matter of pushing the more expensive product as they are listing off various chargers from their competitors as well.
Click to expand...

Please post up what you find out from the contact that Mobi-arc suggested! I'm still learning stuff everyday from other folks. I don't have experience with the dual battery isolater systems yet, so I'm not sure how the relay system will react with charging.

My guess is that Odyssey only tested the chargers back in 08/09 and just haven't updated the list with more recent chargers. The recommended schumacher charger on that list isn't available / made anymore. So I think there are more potential chargers out there that should work fine and not break the bank. If you use a 5 amp charger on a 50% depleted battery 31M, it would take like 10 hrs (if you could get 5 amps all the time under "ideal" conditions), but would take closer to 18-24 hrs due to the charging algorithm to get back to 100% if that make's sense. So you the lower current systems wouldn't be able to get you back on the road after a night of charging? Just speculation on my part again.
 
I found this after some googling. The IBS system should open the relay once the charging voltage (alternator or external like solar? or battery charger) at 13.1 V and then the flow of current depends on the internal battery resistance (so the lesser charged one should receive the proportionally higher amount of current).

http://ibs-tech.ch/en/products/dual-battery-system/faqs-for-ibs-dbsdbi.html
 
So I called Mr. X (we'll call him) at [Superior] Battery Systems. I did not talk to anyone named above. As I understand it, he is a licensed distributor and service representative for Odyssey batteries. As such, he is thoroughly familiar with Odyssey's full line of batteries and chargers.

He informed me that the OMAX-50a is actually not specifically manufactured by Odyssey, which wasn't really a surprise to me as I was really just hoping to find the cheaper brand of it. What he told me after that surprised me. Apparently that charger is notorious for not detecting when the battery is fully charged (thermal run away) and has a tendency to overcharge resulting in aggravating to potentially catastrophic effects. In other words, run the opposite direction of this charger.

He did not state that the charger needs to have a 40 or 50 amp charging current so long as it can detect an internal short, low voltage and is generally automatic in nature. When asking him what his shop uses to service Odyssey batteries and primarily the group 31 and 34 PM batteries, he identified the Techmate Optimate 6 charger.

He also mentioned that he is familiar with the IBS isolator and stated that it was unnecessary to disconnect the batteries from the relay during charging because the relay will not allow the charge current to pass from one battery on to the next. I got sort of lost in the technical speak of it but essentially that was the gist of it.

Link to the charger:
http://www.tecmate.com/u_optimate_6.php
 
Last edited:
Thanks for the report back mechanixhorseman! Good to know about charging requirement and the issues with the OMAX 50. I will need to check out the Techmate Optimate 6, it looks pretty compact and is less than the OMAX 20 that I have!

5 Amp Smart Charger that Mechanixhorseman is referring to. I was googling it and it seems like it got good reviews. MSRP 120, at Amazon.com they ahve it for like 108.
http://www.amazon.com/OptiMate-Ampm...r-tester-maintainer/dp/B003UANXCE?tag=ihco-20
 
Just wanted to update this one more time as I don't want any misinformation subject to search on these forums.

I received the optimate 6 battery charger and hooked it up to my 31M, which is being utilized as my primary battery. Out of curiosity (and maybe a little bit of skepticism) I felt the 200amp relay and it was warm to the touch. I busted out my multi-meter and sure as sh!t, my 34M (aux) battery was receiving a charge consistent with the changes being displayed on the optimate charger. The link and charge lights were also illuminated on the IBS controller.

In other words, the batteries should be manually isolated from one another during interval charges unless someone can explain to me otherwise, why it isn't necessary. I thought about purchasing another 150A circuit breaker to place between the main battery and the relay, or maybe 200.

Thoughts?
 
Makes sense, since the job of the IBS is to link the batteries when a charge is detected. Hmmm. I have one of those Blue Sea switches I use for my winch cutoff- it would make a great override.
 
Any more news on this? I finished my setup this weekend- T-max system with a red top(already had it) starter battery and a platinum 34m aux. I noticed the starter battery was only at 12-12.2 after 1.5 hours drive, and the aux was at ~12.8. This is after very little depletion. Of course, the platinum may not have been fully charged to begin with. So I am also interested in the appropriate charger. I'm also thinking I may have to manually isolate each battery to charge. Everything I read says the deep cycles need a really high amp charger for the first charge phase...? I'm a bit perturbed that I may have to redo the wiring under the hood that I JUST FINISHED. I think I may use the manual switch as an inline disconnect so I will have manual override control of the batteries. Thoughts?
 
Well so far I've got somewhat conflicting information from IBS and the aforementioned odyssey distributor. IBS claims that there is no issue with charging both batteries while linked together because the "smart charge" sees them as one big battery. On the other hand the odyssey rep states that because the batteries are of differing sizes this can and will lead to negative complications. In order to err on the side of caution I would be manually isolating them (one way or another) on probably a monthly basis and charging them individually.

The Optimate 6 has been doing a pretty phenomenal job with charging and I've got it out on the garage now desulfating and reviving my old red top group 35. It is recommended for the full range and types of batteries and since it was recommended by someone whose occupational duties include reconditioning my exact battery, I think it's probably safe to rely on. Initially I found a lot of documentation indicating that the 31M needed a high amp charger, but throughout my research, I really haven't been able to find any rationale for that. I'm still waiting for some answers to a couple more questions I had for IBS, but so far that's where I'm at.

Any ideas for manually isolating that's cheaper than a marine grade 200amp breaker? I don't really feel like busting out the sockets and resetting my clocks every time I want to charge my batteries.

Edit to answer your last about disconnecting the controller: I actually hadn't thought of that and that may very well do the trick. My only concern with that, although minor, is the wear and tear on the connector from regularly disconnecting and reconnecting it. It's a pretty beefy connector and I'm not sure if the T-max is the same, but try to limit the amount of times I have to stress plastic parts if I can.

The only thing I can't seem to get my head around is the thought that this charging issue either 1) is not that big of a deal or 2) nobody acknowledges it and just expects to only get 2-3 years out of their AGM batteries. It seems like IBS/T-Max, etc, would have put a manual isolate button on the controller if it was and maybe I'm just getting wound around the axle for no reason.
 
Last edited:
As far as an alternative to a huge circuit breaker, I have one of these I use as a winch disconnect. Plenty of amp rating and fairly inexpensive:

http://www.bluesea.com/products/9001e/e-Series_Selector_Battery_Switch

I think you could unplug the controller, or if worried about it wearing out (I'm like that, too) you could probably add a small toggle in one of the control lines. I imagine they all need to be connected for the unit to work, but I'm certainly no electrical engineer.

As far as the deep cycle batteries requiring a high amp charger for the initial bulk phase, I found the following sites helpful, but also a bit contradictory:
http://marine-electronics.net/techarticle/battery_faq/b_faq.htm
http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/
http://www.westmarine.com/webapp/wc...reId=11151&page=Battery-Charging#.UZm0IaX1DL9

A couple things I learned: Most "experts" recommend a fairly high initial charge rate. None of them seem to recommend the same rate, though, and none even seem to agree on what voltage a "full" battery should be at, what is really a depleted battery, or whether it is better to really "use" the batteries ( edit- like here: http://www.insideline.net/1996/puckett-1112-96.html ) or "take it easy" and recharge often, etc. Basically no one seems to know/agree. I also have a sneaking suspicion that:

1. Our alternators are not really doing the job (for a dual setup).
2. Most dual battery systems are really not used/charged to their potential, and are in a constant state of mediocrity.
3. Most people, like me, who install dual batteries have no idea what they're doing. They sometimes think they do...
4. 1-3 lead to many of the reports of premature battery failure we hear about.

From what I've read, it's silly to throw a fat deep cycle in as a second battery and expect it to perform without any further mods/chargers/maintenance, unless the user really doesn't need or use the full potential of the system. In that case, a house battery that lives at 70-80% may work just fine, and may be responsible for many of the successful reports of these installs. I dunno. It's late. Good chat.

Good review on the Optimate 6. Thanks!
 
Last edited:
spressomon said:
FWIW I've used a dual bank Battery Tender for about 5-years. Although charging through the isolator probably isn't an issue I've eliminated the concern by connecting both directly to the charger.

http://batterytender.com/products/a...rnational-charger-usa-western-hemisphere.html
Click to expand...

Good too hear you've had good luck with this. Have you checked to see that the batteries are in fact getting a full charge? Have you noticed whether or not the system links during charging? Lastly, it seems most recommend an initial charge amperage of 20-50% of the battery's amp hour rating. Of course 1.25 amps is much less than this. Any opinions?

I'm not looking for perfection, but I also feel like with the time and money spent on this system I should expect good reliability and longevity.

My other concern is with the isolator system itself. The battery voltage "meter" only goes up to 12.8v. This site says a deep cycle is 100% at 12.65v:

http://marine-electronics.net/techarticle/battery_faq/b_faq.htm

but another site (can't seem to find it, still looking) relates that an agm is actually 100% charge at something like 13.4-13.6 volts.

My Platinum 34m showed 12.8v last night. It ran an already cold, full arb 50 qt fridge overnight. This morning I'm showing 12.2 volts. So I used 50% of the battery's capacity to run a fridge for one night??? I sure hope that's not the case.
 
Both Odyssey's (Group 31/PC2150 + Group 34/PC1500) at a resting charge of 13.10v

I have a Powergate dual rectifier type isolator system...but I just connect the dual bank charger directly to the batteries...no other experimentation was done pushing charge current through the PG.

Per hoser: CTEK chargers come well recommended too for AGM, etc. http://smartercharger.com/
 
You must log in or register to reply here.

Share this page

Back
Top Bottom