Wrknrvr Posted March 17, 2019 Report Share Posted March 17, 2019 Just curious about charging two different types and sizes of batteries. Now let's say I have three 8D sealed batteries for RV power. And I have four group 31 12vdc starting batteries for stating the engine. Should the two different groups of batteries be charged separate or can they be charged at the same time. Some motor homes will charge both at the same time. Some will not. Some people ad a really for that purpose. Sorta bored waiting to travel in a few weeks. So I was thinking. Maybe good or just mite be bad. Just saying,. Vern Link to comment Share on other sites More sharing options...
Darryl&Rita Posted March 17, 2019 Report Share Posted March 17, 2019 Separate for battery life, together for cost/convenience. I have been wrong before, I'll probably be wrong again. 2000 Kenworth T 2000 w/N-14 and 10 speed Gen1 Autoshift, deck built by Star Fabrication 2006 smart fourtwo cdi cabriolet 2007 32.5' Fleetwood QuantumPlease e-mail us here. Link to comment Share on other sites More sharing options...
oldjohnt Posted March 17, 2019 Report Share Posted March 17, 2019 8 hours ago, Wrknrvr said: Now let's say I have three 8D sealed batteries for RV power. And I have four group 31 12vdc starting batteries for stating the engine. Should the two different groups of batteries be charged separate or can they be charged at the same time. Some motor homes will charge both at the same time. Some will not. Some people ad a really for that purpose. Great question, it gets a bit complicated but I will try my best to provide some degree of insight and will post a link where you can get a more detailed answer about charging multiple batteries in parallel which is basically what you're asking about. 1) If say you're driving down the road and you have EITHER a mechanical isolation relay that parallels your house and engine batteries together OR a solid state battery isolator THE ENGINES ALTERNATOR WILL LIKELY PROVIDE "SOME" CHARGING CURRENT to your house battery bank but its NOT near the quality nor quantity nor completeness a proper smart charger set to match your battery type (lead acid or AGM or Lithium) can provide. HOWEVER that all depends on the wire gauge and distance back to the house batteries and any other resistances plus the voltage regulation circuitry of your engines alternator and the type or relay used. If you used light gauge wire several feet back to the house bank and expect the engines alternator to charge it very well, you could be disappointed... 2) A problem if you try to charge different batteries in parallel even with a so called smart charger IS DIFFERENT BATTERY TYPES CHARGE BEST AT PARTICULAR CHARGING ALGORITHMS (Voltage, Current, Time etc) . A lead acid prefers one rate while AGM or Lithium is different. Again you can still get 'some" degree of charge but its nowhere near or perfect to what similar batteries would receive connected to one common charger AND FURTHER MORE if the proper series/parallel wiring arrangement isn't used still one battery may not charge as much or as well as the other See: http://www.smartgauge.co.uk/batt_con.html 3) YES two different groups should be charged separate with a charger to match their type FOR BEST RESULTS but as I explained you can still get some degree of charge (albeit not near as good or full or proper) into both if not. For example I let my smart 4 stage charger (set for AGM not Lead acid) OR my MPPT Solar Charge Controller (set for AGM) charge my AGM house bank and engine alternator charge my starting battery BUT I do have a 100% duty cycle mechanical relay so the engines alternator can provide some current to my house bank IFFFFFFFF I turn it on when driving like if its night or cloudy etc where solar isn't contributing. Hope this helps, theres lots more but consider this a NON exact NON perfect start and if you ask I will add more John T Link to comment Share on other sites More sharing options...
sundancer268 Posted March 18, 2019 Report Share Posted March 18, 2019 If the sealed 8D is NOT an AGM, Jell or Lithium, it will be a Lead Acid battery and will charge the same as the Chassis battery. Maintenance free does not mean AGM, Jell or Lithium. I have a set of Maintenance free batteries for starting and had two Flooded cell 6 volt batteries for the house side and had no problems. The 6 volt batteries died after 7 years and were replaced with AGM batteries, the Sealed Maintenance free Chassis batteries are still working going on 9 years, (Hope they will start the coach when I take it out of winter storage). I did reset the Magnum inverter to AGM for the charging profile, and let the alternator be for now. I am looking into a Belmar type regulator for future alternator installation, I just am not sure my Delco can be easily converted. I do keep the coach plugged in 24/7 when at home whether up by the house in the summer season or in the barn for winter storage so I am sure that helps. U.S. Navy GSMC(SW) (RETIRED) 1993-11-01, 26 years service with 23 years of that active and 3 years reserve. Now retired after 20 years at local hospital in the maintenance department. 1995 Gulf Stream Scenic Cruiser 34' DP W/6Spd Allison. Road Master Sterling All terrain, Air Force One, towing new 2019 Jeep Cherokee Elite Link to comment Share on other sites More sharing options...
oldjohnt Posted March 18, 2019 Report Share Posted March 18, 2019 2 hours ago, sundancer268 said: If the sealed 8D is NOT an AGM, Jell or Lithium, it will be a Lead Acid battery and will charge the same as the Chassis battery. Good morning sundancer, Even if the house and engine batteries are lead acid they will NOT "charge the same". That's simply because in the wiring back to the house battery there is resistance and voltage drop and its NOT the same as the factory wiring from the alternator and its voltage regulation scheme and where voltage is monitored to the engine battery. YES the house battery will still receive "some" charge and that depends on the wire size and distance and relay but the two batteries although still "charging" will NOT "charge the same" Of course, the fact that BOTH are lead acid is MUCH better then if they were mixed which could make proper charging and balanced charging even worse lol YES indeed I sure agree both being lead acid means they have the same preferred charge algorithm and charge profile and will "charge the same" PROVIDED all else is equal ….. 2 hours ago, sundancer268 said: I did reset the Magnum inverter to AGM for the charging profile, and let the alternator be for now. I am looking into a Belmar type regulator for future alternator installation, I just am not sure my Delco can be easily converted. I do keep the coach plugged in 24/7 when at home whether up by the house in the summer season or in the barn for winter storage so I am sure that helps Good plan, the charger or solar charge controller should indeed be set to match the battery!!! YES when plugged to shore power a quality "smart charger" maintaining the batteries is great and the same method I use at times Fun chatting with you Sundancer, best wishes n God Bless John T Link to comment Share on other sites More sharing options...
Kirk W Posted March 18, 2019 Report Share Posted March 18, 2019 Vern, based on many years of working with batteries I'll offer a few comments on previous posts knowing that I will be corrected. In practical application, if the batteries are all flooded cell most of us would opt to charge them all together even though it won't be the very best use of battery theory because the cost of designing and implementing the perfect solution is far beyond the value of what you would gain. When you get into the newest technology such as lithium batteries mixed with flooded cell you create an entirely different situation. Flooded cell is still the most common type of battery in use in the RV community but the days are probably numbered. Good travelin !...............KirkFull-time 11+ years...... Now seasonal travelers.Kirk & Pam's Great RV Adventure Link to comment Share on other sites More sharing options...
oldjohnt Posted March 18, 2019 Report Share Posted March 18, 2019 7 hours ago, Kirk W said: Flooded cell is still the most common type of battery in use in the RV community but the days are probably numbered. AMEN Kirk no argument from me...…...I see more and more AGM use nowadays (and even some factory installed Lithium, RVX) to reduce worry and hassle of adding electrolyte PLUS the latest series of "drop in" Lithium battery technology with built in protection and in reduced frame sizes such as Battle Born and others is making it simple n easier to go the Lithium route, but darn they are expensive up front even if over the long run considering cost per life cycle they are great. They still have some cold temperature issues. Hey as one gets older they don't even buy green bananas let alone invest in batteries that may perform 10 plus years to recoup their huge initial investment lol IE at my age AGM was my choice... FWIW We are also on the same page regarding your statement "In practical application, if the batteries are all flooded cell most of us would opt to charge them all together" I SURE DO When I had four flooded lead acid I charged them all together and now when I have three AGM I again charge them all together. Might I dare to say GREAT MINDS THINK ALIKE No correction from me on that for darn sure...…….. FWIW Ive primarily been talking above about letting the RV engine alternator charge the house batteries when driving down the road, although sure one can also configure the house charger/converter when plugged to shore power to also charge the engine battery if desired. Although its not rocket science the easy and simplest way to achieve better charge balance when batteries are separated is the use of bigger cables, but that could prove expensive and cumbersome As always great chatting with you Kirk John T Link to comment Share on other sites More sharing options...
noteven Posted March 18, 2019 Report Share Posted March 18, 2019 I always wonder if you been campin’ and run the house battery down with lights and gadgets and furnace and watching the latest fear, disasters and mayhem ‘scuse me “The News”, and then plug in the 7 wire plug as you hook up to leave is the teeny blue wire in there now the worlds smallest booster cable? "Are we there yet?" asked no motorcycle rider, ever. Link to comment Share on other sites More sharing options...
oldjohnt Posted March 18, 2019 Report Share Posted March 18, 2019 1 hour ago, noteven said: is the teeny blue wire in there now the worlds smallest booster cable? Pretty much LOL A teeny wire ran back maybe 20 or 30 or more feet is a darn poor "booster cable" yet it can keep a toad battery trickle charged while towing to "some" limited extent...…….. When dry camped I don't allow my RV engine battery nor any toad battery in the house battery circuit...…….. John T Link to comment Share on other sites More sharing options...
Wrknrvr Posted March 18, 2019 Author Report Share Posted March 18, 2019 Noteven,. When I see the low battery's on that blue wire situation. It most likely will have blown the fuse in the truck to charge the blue wire subject. I have one siting across from me now that has that problem. Just thinking,. Vern Link to comment Share on other sites More sharing options...
noteven Posted March 19, 2019 Report Share Posted March 19, 2019 Hi John and Vern, On my previous truck camper rigs I disconnect the blue charge wire in the truck camper’s 7 way plug. I connect the camper batteries with I forget what size cables (3/8” diameter or so) to a 160amp isolator. I get nice amps at the camper batteries I think. "Are we there yet?" asked no motorcycle rider, ever. Link to comment Share on other sites More sharing options...
oldjohnt Posted March 19, 2019 Report Share Posted March 19, 2019 55 minutes ago, noteven said: On my previous truck camper rigs I disconnect the blue charge wire in the truck camper’s 7 way plug. I connect the camper batteries with I forget what size cables (3/8” diameter or so) to a 160amp isolator. I get nice amps at the camper batteries I think. With big enough cables and heavy duty high current rated quality connectors (IE low resistance and voltage drop), you get MUCH MORE charging amps, that a WELL DUH LOL If you want to use an energy source such as an alternator or battery charger to pump energy into a battery, its best to dissipate that energy into the desired load NOT waste it as I Squared R heat losses in the wiring. That's all basic conservation of energy. Then if you want to balance the charging into multiple batteries its best if they are the same type and design and if connected according to http://www.smartgauge.co.uk/batt_con.html. Take care yall John T Dry camped in the Ocala Natl Forest but under full shade and cloudy days I'm not harvesting an abundance of solar energy... Link to comment Share on other sites More sharing options...
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