Magnum Charger/Inverter 2nd opinion

[Todd Franklin]

So we have an 08 Contessa with the Magnum ME2012.  I recently changed out all the house batteries from AGM to Li-ion and in the process installed a Victron battery monitor.  What I'm seeing is that the Magnum goes immediately to float charge when plugged into shore power or starting the generator and doesn't pump charge in. Usually the batteries are in the 70-75% SOC at this point.  The Magnum panel shows 12.9-13.1v and 0>A.  This morning I went to the garage, batteries at 50% SOC and unplugged from the shore power and plugged back in.  It immediately started to charge. 

So my conversations with Magnum was that the charger will stay in float status until the batteries hit 12.8 vdc.  That makes sense.  But if the SOC is 50% meaning that the batteries are probably around 12.7, shouldn't the Magnum automatically top them off? We're always plugged in when in the garage so battery should always be at full charge.  Why would I need to do something to get the charger to start charging?  I'm thinking I may have an internal problem with the Magnum?  I know there are upgrades to a newer charger/inverter but this is still perplexing.  On our trip back from Montana Sunday the alternator topped them off so I know it's not a battery or shunt issue. Any thoughts?  Thanks!

[Bill Lampkin]

Todd, From what I know about lithium, they don't need a 'float' charge, nor equalization charge. Does your Magnum have a lithium or custom setting? I would turn off settings for float and certainly for eq charging. YOu may have to get used to 70 or 80% charge level with the lithium, remember, they recharge much faster than lead acid. And be sure not to charge at all below 32F.

[Fred Brooks]

   Todd,
 Did you change the charging profile from the former batteries to the Lithium batteries? What settings did Magnum recommend? For starters, I would discharge the batteries down to 50% which is 12.3 volts. You can do this by unplugging the coach and turn all the interior lights on and turn the inverter on and the tv's and audio equipment. Once the batteries reach 12.3 volts, turn everything back off you turned on. Plug the coach into 30 or 50 amp plug. The inverter/converter should go to "bulk charge" the amperage jump up to 80 to 90 amps charge rate. Once the batteries reach approximately 80% charge it should change to "absorb charge". This means the charger is ramping down the charge rate to give the batteries the ability to absorb the charge instead of overcharging. You will see the amps go down gradually to approximately 25 amps and then the charger will go into "float". Float is the maintenance charge rate to "top off the batteries" and supply the needs of the 12volts demands of the coach interior. This should prove that the inverter/converter is working as designed. In the event you change the inverter/charger. I would recommend the MS version because it is a "pure sine wave" inverter/converter. Hope this helps, Fred

[Bill Lampkin]

You may also want to look at replacing your 'BIRD' relay with one designed for lithium:

https://battlebornbatteries.com/systems/rv/

Lots of good info

[Bill Lampkin]

More info on Magnum 2012 and lithium


https://battlebornbatteries.com/can-use-magnum-ms2012-lifepo4-battery-bank

[Todd Franklin]

Thank you everyone for the great responses.  These are Battle Born batteries since they are local to me.  We have adjusted the settings on the Magnum and continue to tweak.  We will be installing a BIM from Battle Born.  Our low cut off and float parameters are set.  Since we hit the road right after the batteries were installed we haven't had a chance to do any follow up with BB and will be doing so over the next few days.  What we do know is that 10 days of dry camping were so much better with these batteries.

[Joel Ashley]

Keep us apprised, Todd.  I’m in a quandary over replacing my factory 14+ year-old original house batteries.  More Interstate wet cells would be cheap and easy, and obviously are long-lived.  But all but one advisor, a respected member here, like lithium’s, and his main concern was with the price, 9 times that of wet cells.  He’d stick with flooded ones.  BMS only adds to that cost, and contrary to some info, a Magnum/Big Boy/BIRD system can charge them, just not as fast.

I too was looking into Battle Born, and Expion and Victron, all road-tough brands unlike cheaper Chinese-made ones.

One Bend repairman has replaced more AGM’s than he can count, and isn’t a fan of them.  So now I’m not certain what I’ll do.  A year ago I would have bought Costco flooded Interstate GC2’s, like the old ones, but I’d rather not deal any more with the tray corrosion and plastics melting related to gassing wet cells. 

Joel

[Bill Lampkin]

Joel, After speaking to Battle Born, the issue with the Big boy is possible overcharging from the engine alternator.

[Gene Obie]

Joel, on your comment "One Bend repairman has replaced more AGM’s than he can count, and isn’t a fan of them. "  Was his comment he's replaced AGM with Lithium and wasn't a fan of lithium or was the comment he's replaced flooded with AGM and not a fan of AGM?

For the bird relay issue, if the only problem is alternator overcharging the lithium, I'm wondering if you could just put a switch in the control line to big bird and disable it when hitting the road. You could charge the house batteries with generator if necessary. A little bit of a pain but sure easier than swapping out the entire bid bird system.

I'm also due for new house batteries and with research I've done so far I'm thinking for me 6-6V AGM may be the best route. Perhaps in the future I will add 1-2 lithium under the bed on separate system (2-3 panels on the roof with separate charge controller) mainly to run residential fridge and a few outlets. Would only do that if I find I'm doing more dry camping than expected and my smaller inverter generator with AGM is not working for me. I can run that little generator a long time for the cost delta. I'm also concerned with temperature issues on having the lithium in outside tray. Can be mitigated with heaters (Battleborn sells a solution) but just something else to install and worry about

[Joel Ashley]

Gene, it was well-respected Jeff Spear that told me he removed more AGMs from coaches than other types, but as with anything else there are different battery qualities, and owners are different in how well they care for them.  They don’t need or care for equalization, for example, and owners may not switch their solar and inverter controls accordingly when changing to AGMs from wet cells. 

He was encouraging me to go lithium without any additional special monitoring devices or modifications he deemed unnecessary.  But further professional opinions since pointed up other considerations that just made lithium’s with best performance add-ons too expensive.  My Magnum had the wrong remote for lithium’s and the solar controller model wasn’t right.  I had talked with Battleborn, looked at several other brands, and considered a full professional install at AM Solar, but the cost got prohibitive for that and too complex if I tried installing it myself.

As I note in another thread here today, I zeroed in on a local dealer’s decent price on high-rated Fullriver AGMs, Centennial, and US Battery.  US Battery makes Centennials in China.  Fullriver is a US Brand too, but makes it’s batteries in China.  US Battery branded ones are made here, I think by Johnson Controls using USB’s parameters.  Some Chinese builds are high quality like Fullriver, but where possible I’m trying to avoid sending my cash to China.

Joel

[Gene Obie]

Hmmm, after reading your response I've dug into my SW2512 inverter and RV45D solar controller specs. It seems I can set the bulk charge voltage to 14.4V (in range with Battleborn Lithium spec). And I can set SW2512  float voltage down to 13.6V (per Battleborn spec, basically disabling float charge). And RV45D has a setting to disable auto-float and equalization.  And looking at my Big Boy schematics, I'm thinking of adding a relay to the Big Boy relay so whenever ignition is on Big Boy is disabled (the ignition switch signal already goes to Big Bird controller to in the area and easy mod). It will need to be wired such that boost is still enabled- so tap the relay into the signal between Big Bird and boost relay). With this setup I will still get inverter to charge both batteries when ignition is OFF and always isolate chassis and house batteries when ignition is ON (unless I hit boost switch). I'm fine (actually prefer) the alternator not charging house batteries... and really don't like the fact when I'm running generator (or shore) and engine/alternator at the same time the systems can be connected via Big Boy. Evidently doesn't cause problems but seems like a problem waiting to happen. With Lithiums I'll have enough house battery energy for any length of drive I make to keep refrigerator going - or I can just run the generator a bit. I've sent Battleborn with a list of questions. Am I missing anything?

Apologies if I inappropriately hijacked this thread.

[Mike Shumack]

I wonder how the mix of batteries (AGM/wet cell and Lithium) handle being charged at the same rate or same charging profile.

If you install Lithium "House" batteries and AGM "Chassis" batteries, then setup your Inverter/Charger for Lithium, your Chassis batteries would be charging using the wrong profile (meaning your now charging your Chassis batteries on the Lithium setting), and vise versa, when the battery isolator is closed and both battery groups are connected together.

[Bill Lampkin]

I'm not an expert, but charge voltage for AGM is 14.6-14.8v and float is about 1v less. Same as Lithium as far as I can tell. I asked this question of Battleborn some time ago and they suggested replacing the BIRD with this: https://precisioncircuitsinc.com/product/battery-isolation-manager-225-amps-lithium-battery/