Charging 2 Banks, More of the Same with a twist

[BC Bus]

I know this has been beaten to death, but I am searching for one simple answer from within this topic that I can't pull out on this or other boards. 

Scenario - Two 24v banks of batteries, one for the bus which are 2 stock 8 D's, and another band for the house, which are 4-6volt Golf Cart Batts which are connected to a 24v, 3600 watt Trace inverter.  The MAIN reason I RUN this system is to run Roof top AC's driving down the road, taking advantage of the 50DN's output.

Question: It seems that if they are connected together for charging, from the stock  50DN Deco Remy  bus Alternator, that one or both of the banks of batteries will be ruined, boiled, OR overcharged.  Right now I have a manual switch so that I AM NEVER CHARGING THE TWO BANKS SIMULTANEOUSLY. 

What if I elimininated the manual switch an converted to a Solenoid, discussed to death on the other board, and both banks where being charged when the engine was running.  Would it lessen the battery life?

Comments please.

[Nick Badame Refrig/ACC]

Hi BC,

I think that if you were able to monitor the start batts with a volt meter, you can simply charge them as needed manually with either

a solenoid switch or selector switch.   Keep it simple!  More gadgets mean more headachs!

Nick-

[jeffacc]

I did the same thing and I used a battery isolator. I have 2 8Ds for the bus and a 24 volt bank of batteries for the house it runs a 24 volt inverter I also have a equalizer for 12 volt off the house batteries its been 3 years and no problems.

[gumpy]

Solenoid works well. Make sure it's at least 200 amps continuous duty. You won't ever see that much current, but it's good insurance.

[jjrbus]

Being electrically challenged I looked at what other people where doing in the real world that worked!!! I did not want theory, or an education, I do not care that the molecues are rotating around the planet in an orderly fashion. Besides even if I were to learn all this I would forget it all anyway!!
 The system that I found that is simple and does not let the smoke out of the box. I have a 24 volt system,  2 group 31 batterys in the engine compartment for the bus. I have 4 6 volt golf cart batteries for the house. These are tied together with a selector switch (one less thing to go wrong,hopefully) I normally run with the selector switch in the both position. Useing the 24 volt bus alternator coupled to a Trace Dr3624 inverter, to run everything including the roof air as I travel. Also chargeing the bus batteries.
 In 5 years useing this sytem, I have yet to ruin a battery or let the smoke out of the inverter, alternator, voltage regulator ect.
 I was carefull to wire everything with the right size wire or larger, mostly larger! All circuts are fuse protected. Cable ends are crimped on and  shrink wraped. The selector switch is a heavy duty marine style, 350 amp continuous 1000 amp surge I belive.
 I was told by the mechanic, a man by the name of Dan in Milton Wa., NEVER walk away from the bus without turning the batterys off. I rambled on a bit here but to ansewer your question no it will not ruin the batteries.
                                                                         HTH

[Sojourner]

Question…can two separate bank of batteries can be charge at the same time?
Yes and No!

Yes if:
1)   All batteries are same capacity & model # & physical size & same brand & build date within a few days.
2)   All batteries are installed & charged fully same time.
3)   Discharging rate of both bank are equally same or the given state of charge are equal.
4)   All batteries before getting charge are within same given temperature.
5)   Water level is same according to the given state of charge.

Might add….If equips with a master cut-off switch…never run alternator with switch in “off” state. It can go into wide open mode…very high volts to damage diodes &/or regulator.

Otherwise No if you want max batteries life!

Why….because all series connected batteries are to be treated as One battery. Such as 2-6v batteries is now 12v battery. Two-12v batteries are now 24v battery.
Alternator with internal or external regulator Only sees whatever given battery output voltage is. Another word alternator does not care what size or number of batteries to achieve whatever your main power voltage of 12v or 24v. If less than fully state of charge it will be charge accordingly. Another word if one bank is discharged more than other….it will shorten life of the “less discharge” bank before other bank is less than fully charged. Any rate of overcharged will cause higher plates heat & drying out than lesser charged.

Longest & strongest battery life is to keep it cool as possible while charging & in storage area as well to avoid being draining below 50% state of charge. The less the better.

However if you are please with mixed & unequal drained batteries banks being charged at the Same Time via one alternator...good....it your money invested.

You can & should only charge one bank of batteries at a time using same alternator.

FWIW

Sojourn for Christ, Jerry

[jjrbus]

 My battery banks are not equlal size . I have group 31 and golf cart. They a re not the same age, bus batterys were put in at least 1 year befor house battery.I have totally discharged one bank of batterys and not the other.
 In theory this is not a good setup. But I have seen people do it, it is simple, cost effective and it works! If you need gauges and gizmos, sensors and diodes, seperators and dohickeys, to get  more life out of your batterys go for it. Its your bus, do it your way!!!!!

[JackConrad]

Question: It seems that if they are connected together for charging, from the stock  50DN Deco Remy  bus Alternator, that one or both of the banks of batteries will be ruined, boiled, OR overcharged.  Right now I have a manual switch so that I AM NEVER CHARGING THE TWO BANKS SIMULTANEOUSLY. 

What if I elimininated the manual switch an converted to a Solenoid, discussed to death on the other board, and both banks where being charged when the engine was running.  Would it lessen the battery life?

The alternator will charge based on the voltage in the battery bank that the regulator is connected to. There are many variables that will effect the overall life of your batteries and every usage situation is different. I like to go by the advice of people that have BTDT. Jack

[Lee Bradley]

It will be a while before I get there but I am thinking of seperating the housing and the coach. The big alternator with an upgraded requlator for the housing batteries, a small (90 amp) single-wire alternator running off the cam pulley for the coach batteries and a solenoid to connect them for a jump start. If I lose the big alternator, I can run the house off the gen-set. If I lose the small alternator, I charge the coach batteries with a 110 volt charger.

[Stan]

In an ideal world you could buy identical batteries and make two sets of identical battery banks. This is not an ideal world and even new batteries out of the same lot will not be identical. They may be close but at some point one battery will fail before the others in the set.

If you take a random batch of batteries and make two banks and tie them in parallel to the alternator neither bank will charge above the setting on the regulator and the current will flow to the batteries with the lowest resisitance. At some point all the batteries will be charged up to the voltage set on the regulator. If you set the voltage too high, even one battery will be boiled dry. If you set it too low none of the batteries will be fully charged. If you set it to a point where you are not using excessive water from any battery you have the best compromise.

You may not get the maximum theoretical life out of any of the batteries but the convenience far outweighs the cost of changing batteries a few weeks or months sooner than you would with multiple switches and charging systems. Batteries are an expendable item and like tires, brakes and oil changes you shouldn't be trying to get the last possible mile or minute out of them because then the cost and inconvenience skyrockets with breakdowns.